Effects of Acoustic Impulses on the Middle Ear

DTIC Science & Technology

2016-10-01

development of a MEMC detection algorithm for use with the National Health and Nutrition Examination Survey (NHANES) impedance traces. The second specific...Flamme GA, Deiters KK, Tasko SM, Ahroon WA (under review). Acoustic reflexes are common but not pervasive: Evidence from the National Health and Nutrition ...of new (or revising existing) damage risk criteria and health hazard assessment methods for exposure to high-level acoustic impulses such as

Theoretical performance of liquid hydrogen and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid hydrogen and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion-chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ration of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 364.6 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Theoretical performance of liquid ammonia and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid ammonia and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 311.5 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Impulsive action: emotional impulses and their control

PubMed Central

Frijda, Nico H.; Ridderinkhof, K. Richard; Rietveld, Erik

2014-01-01

This paper presents a novel theoretical view on impulsive action, integrating thus far separate perspectives on non-reflective action, motivation, emotion regulation, and impulse control. We frame impulsive action in terms of directedness of the individual organism toward, away, or against other givens – toward 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. PMID:24917835

50 KW Class Krypton Hall Thruster Performance

NASA Technical Reports Server (NTRS)

Jacobson, David T.; Manzella, David H.

2003-01-01

The performance of a 50-kilowatt-class Hall thruster designed for operation on xenon propellant was measured using kryton propellant. The thruster was operated at discharge power levels ranging from 6.4 to 72.5 kilowatts. The device produced thrust ranging from 0.3 to 2.5 newtons. The thruster was operated at discharge voltages between 250 and 1000 volts. At the highest anode mass flow rate and discharge voltage and assuming a 100 percent singly charged condition, the discharge specific impulse approached the theoretical value. Discharge specific impulse of 4500 seconds was demonstrated at a discharge voltage of 1000 volts. The peak discharge efficiency was 64 percent at 650 volts.

Experimental investigation of the pulsed electrothermal (PET) thruster

NASA Technical Reports Server (NTRS)

Burton, R. L.; Goldstein, S. A.; Hiko, B. K.; Tidman, D. A.; Winsor, N. K.

1984-01-01

Burton et al. (1982) have discussed the theory of the Pulsed Electrothermal (PET) thruster, a device which in principle can operate with 70 percent efficiency at a specific impulse of 1000 seconds and higher. It is pointed out that this level of performance would be particularly attractive for orbit raising of large satellites and other near-earth missions, which cannot be easily accomplished by chemical propulsion. The present investigation is concerned with two PET thruster operating modes. A PET thruster was built and tested on a thrust stand. Exhaust velocities for polyethylene propellant vary from 20 to 27 km/sec. Single pulse specific impulse and efficiency measurements based on ablated mass show a thruster efficiency of 37-56 percent in the time range from 1000 to 1750 seconds. It is believed that an improved design with a thruster efficiency in the range from 70 to 80 percent might be possible.

Performance Optimization of Storable Bipropellant Engines to Fully Exploit Advanced Material Technologies

NASA Technical Reports Server (NTRS)

Miller, Scott; Henderson, Scott; Portz, Ron; Lu, Frank; Wilson, Kim; Krismer, David; Alexander, Leslie; Chapman, Jack; England, Chris

2007-01-01

This paper summarizes the work performed to dale on the NASA Cycle 3A Advanced Chemical Propulsion Technology Program. The primary goals of the program are to design, fabricate, and test high performance bipropellant engines using iridium/rhenium chamber technology to obtain 335 seconds specific impulse with nitrogen tetroxide/hydrazine propellants and 330 seconds specific impulse with nitrogen tetroxide/monomethylhydrazine propellants. Aerojet has successfully completed the Base Period of this program, wherein (1) mission and system studies have been performed to verify system performance benefits and to determine engine physical and operating parameters, (2) preliminary chamber and nozzle designs have been completed and a chamber supplier has been downselected, (3) high temperature, high pressure off-nominal hot fire testing of an existing state-of-the-art high performance bipropellant engine has been completed, and (4) thermal and performance data from the engine test have been correlated with new thermal models to enable design of the new engine injector and injector/chamber interface. In the next phase of the program, Aerojet will complete design, fabrication, and test of the nitrogen tetroxide/hydrazine engine to demonstrate 335 seconds specific impulse, and also investigate improved technologies for iridium/rhenium chamber fabrication. Achievement of the NRA goals will significantly benefit NASA interplanetary missions and other government and commercial opportunities by enabling reduced launch weight and/or increased payload. At the conclusion of the program, the objective is to have an engine ready for final design and qualification for a specific science mission or commercial application. The program also constitutes a stepping stone to future, development, such as higher pressure pump-fed in-space storable engines.

Impulsivity and Suicidality in Adolescent Inpatients.

PubMed

Auerbach, Randy P; Stewart, Jeremy G; Johnson, Sheri L

2017-01-01

Suicide is the second leading cause of death among adolescents, and impulsivity has emerged as a promising marker of risk. The present study tested whether distinct domains of impulsivity are differentially associated with suicide ideation, plans, and attempts. Adolescents (n = 381; boys = 106, girls = 275) aged 13-19 years (M = 15.62, SD = 1.41) were recruited from an acute, residential treatment program. Within 48 h of admission to the hospital, participants were administered structured clinical interviews assessing mental health disorders and suicidality. Following these interviews, participants completed self-report questionnaires assessing symptom severity and impulsivity. Consistent with past research, an exploratory factor analysis of our 90-item impulsivity instrument resulted in a three-factor solution: Pervasive Influence of Feelings, Feelings Trigger Action, and Lack of Follow-Through. Concurrent analysis of these factors confirmed hypotheses of unique associations with suicide ideation and attempts in the past month. Specifically, whereas Pervasive Influence of Feelings (i.e., tendency for emotions to shape thoughts about the self and the future) is uniquely associated with greater suicidal ideation, Feelings Trigger Action (i.e., impulsive behavioral reactivity to emotions) is uniquely associated with the occurrence of suicide attempts, even after controlling for current psychiatric diagnoses and symptoms. Exploratory gender analyses revealed that these effects were significant in female but not male adolescents. These findings provide new insight about how specific domains of impulsivity differentially increase risk for suicide ideation and attempts. Implications for early identification and prevention of youth suicide are discussed.

Impulsivity and Suicidality in Adolescent Inpatients

PubMed Central

Stewart, Jeremy G.; Johnson, Sheri L.

2016-01-01

Suicide is the second leading cause of death among adolescents, and impulsivity has emerged as a promising marker of risk. The present study tested whether distinct domains of impulsivity are differentially associated with suicide ideation, plans, and attempts. Adolescents (n = 381; boys = 106, girls = 275) aged 13–19 years (M = 15.62, SD = 1.41) were recruited from an acute, residential treatment program. Within 48 h of admission to the hospital, participants were administered structured clinical interviews assessing mental health disorders and suicidality. Following these interviews, participants completed self-report questionnaires assessing symptom severity and impulsivity. Consistent with past research, an exploratory factor analysis of our 90-item impulsivity instrument resulted in a three-factor solution: Pervasive Influence of Feelings, Feelings Trigger Action, and Lack of Follow-Through. Concurrent analysis of these factors confirmed hypotheses of unique associations with suicide ideation and attempts in the past month. Specifically, whereas Pervasive Influence of Feelings (i.e., tendency for emotions to shape thoughts about the self and the future) is uniquely associated with greater suicidal ideation, Feelings Trigger Action (i.e., impulsive behavioral reactivity to emotions) is uniquely associated with the occurrence of suicide attempts, even after controlling for current psychiatric diagnoses and symptoms. Exploratory gender analyses revealed that these effects were significant in female but not male adolescents. These findings provide new insight about how specific domains of impulsivity differentially increase risk for suicide ideation and attempts. Implications for early identification and prevention of youth suicide are discussed. PMID:27025937

Status of Pulsed Inductive Thruster Research

NASA Technical Reports Server (NTRS)

Hrbud, Ivana; LaPointe, Michael; Vondra, Robert; Lovberg, Ralph; Dailey, C. Lee; Schafer, Charles (Technical Monitor)

2002-01-01

The TRW Pulsed Inductive Thruster (PIT) is an electromagnetic propulsion system that can provide high thrust efficiency over a wide range of specific impulse values. In its basic form, the PIT consists of a flat spiral coil covered by a thin dielectric plate. A pulsed gas injection nozzle distributes a thin layer of gas propellant across the plate surface at the same time that a pulsed high current discharge is sent through the coil. The rising current creates a time varying magnetic field, which in turn induces a strong azimuthal electric field above the coil. The electric field ionizes the gas propellant and generates an azimuthal current flow in the resulting plasma. The current in the plasma and the current in the coil flow in opposite directions, providing a mutual repulsion that rapidly blows the ionized propellant away from the plate to provide thrust. The thrust and specific impulse can be tailored by adjusting the discharge power, pulse repetition rate, and propellant mass flow, and there is minimal if any erosion due to the electrodeless nature of the discharge. Prior single-shot experiment,; performed with a Diameter diameter version of the PIT at TRW demonstrated specific impulse values between 2,000 seconds and 8,000 seconds, with thruster efficiencies of about 52% for ammonia. This paper outlines current and planned activities to transition the single shot device into a multiple repetition rate thruster capable of supporting NASA strategic enterprise missions.

Scaling of Ion Thrusters to Low Power

NASA Technical Reports Server (NTRS)

Patterson, Michael J.; Grisnik, Stanley P.; Soulas, George C.

1998-01-01

Analyses were conducted to examine ion thruster scaling relationships in detail to determine performance limits, and lifetime expectations for thruster input power levels below 0.5 kW. This was motivated by mission analyses indicating the potential advantages of high performance, high specific impulse systems for small spacecraft. The design and development status of a 0.1-0.3 kW prototype small thruster and its components are discussed. Performance goals include thruster efficiencies on the order of 40% to 54% over a specific impulse range of 2000 to 3000 seconds, with a lifetime in excess of 8000 hours at full power. Thruster technologies required to achieve the performance and lifetime targets are identified.

Theta-Pinch Thruster for Piloted Deep Space Exploration

NASA Technical Reports Server (NTRS)

LaPointe, Mike R.; Reddy, Dhanireddy (Technical Monitor)

2000-01-01

A new high-power propulsion concept that combines a rapidly pulsed theta-pinch discharge with upstream particle reflection by a magnetic mirror was evaluated under a Phase 1 grant awarded through the NASA Institute for Advanced Concepts. Analytic and numerical models were developed to predict the performance of a theta-pinch thruster operated over a wide range of initial gas pressures and discharge periods. The models indicate that a 1 m radius, 10 m long thruster operated with hydrogen propellant could provide impulse-bits ranging from 1 N-s to 330 N-s with specific impulse values of 7,500 s to 2,500 s, respectively. A pulsed magnetic field strength of 2 T is required to compress and heat the preionized hydrogen over a 10(exp -3) second discharge period, with about 60% of the heated plasma exiting the chamber each period to produce thrust. The unoptimized thruster efficiency is low, peaking at approximately 16% for an initial hydrogen chamber pressure of 100 Torr. The specific impulse and impulse-bit at this operating condition are 3,500 s and 90 N-s, respectively, and the required discharge energy is approximately 9x10(exp 6) J. For a pulse repetition rate of 10 Hz, the engine would produce an average thrust of 900 N at 3,500 s specific impulse. Combined with the electrodeless nature of the device, these performance parameters indicate that theta-pinch thrusters could provide unique, long-life propulsion systems for piloted deep space mission applications.

UWB transmitter

DOEpatents

Dallum, Gregory E.; Pratt, Garth C.; Haugen, Peter C.; Romero, Carlos E.

2013-01-15

An ultra-wideband (UWB) dual impulse transmitter is made up of a trigger edge selection circuit actuated by a single trigger input pulse; a first step recovery diode (SRD) based pulser connected to the trigger edge selection circuit to generate a first impulse output; and a second step recovery diode (SRD) based pulser connected to the trigger edge selection circuit in parallel to the first pulser to generate a second impulse output having a selected delay from the first impulse output.

Proposed system design for a 20 kW pulsed electrothermal thruster

NASA Technical Reports Server (NTRS)

Burton, R. L.; Goldstein, S. A.; Hilko, B. K.; Tidman, D. A.; Winsor, N. K.

1984-01-01

A conceptual design is presented for a Pulsed Electrothermal (PET) propulsion system for the Air Force Space Based Radar satellite, which has a mass of 7000 kg. The proposed system boosts the SBR satellite from 150 n.m. to 600 n.m. with a 4 deg plane change, for a total mission Delta v of 1 km/sec. Satellite power available is 50 kW, and 45 kW are used to drive two water-injected 20 kW PET thrusters, delivering 5.6 N thrust to the SBR at 1000 seconds specific impulse. The predicted mission trip time is 15 days. The proposed system consumes 850 kg of water propellant, stored in a central tank and injected with pressurized helium. Component mass estimates based on space-qualified hardware are presented for the propellant handling, power conditioning and thruster subsystems. The estimated total mass is 400 kg and the propulsion system specific mass is alpha = 10 kg/kW. The proposed system efficiency of 0.62 at 1000 seconds specific impulse is supported by experimental performance measurements.

High Pressure Earth Storable Rocket Technology Program-Hipes Options 1/2 Report

NASA Technical Reports Server (NTRS)

Chazen, M. L.; Sicher, D.; Calvignac, J.; Ono, D.

1999-01-01

Under the High Pressure Earth Storable Rocket Technology (HIPES) Program, TRW successfully completed testing of two 100 lbf thrust class rhenium chambers using N204-MMH. The first chamber was successfully fired for 4789 seconds of operating time with a maximum duration of 700 seconds. This chamber had been previously fired for 5230 seconds with N2O4-N2H4. The second chamber was successfully fired for 8085 seconds with a maximum firing duration of 1200 seconds. The Isp (specific impulse) for both chambers ranged from 323 lbf-sec/lbm to 330 lbf-sec/lbm.

Evaluation of Low Power Hall Thruster Propulsion

NASA Technical Reports Server (NTRS)

Manzella, David; Oleson, Steve; Sankovic, John; Haag, Tom; Semenkin, Alexander; Kim, Vladimir

1996-01-01

Hall thruster systems based on the SPT-50 and the TAL D-38 were evaluated and mission studies were performed. The 0.3 kilowatt SPT-50 operated with a specific impulse of 1160 seconds and an efficiency of 0.32. The 0.8 kilowatt D-38 provided a specific impulse above 1700 seconds at an efficiency of 0.5. The D-38 system was shown to offer a 56 kilogram propulsion system mass savings over a 101 kilogram hydrazine monopropellant system designed to perform North-South station keeping maneuvers on board a 430 kilogram geostationary satellite. The SPIT-50 system offered a greater than 50% propulsion system mass reduction in comparison to the chemical system on board a 200 kilogram low Earth orbit spacecraft performing two orbit raises and drag makeup over two years. The performance characteristics of the SPF-50 were experimentally evaluated at a number of operating conditions. The ion current density distribution of this engine was measured. The performance and system mass benefits of advanced systems based on both engines were considered.

Interval oscillation criteria for second-order forced impulsive delay differential equations with damping term.

PubMed

Thandapani, Ethiraju; Kannan, Manju; Pinelas, Sandra

2016-01-01

In this paper, we present some sufficient conditions for the oscillation of all solutions of a second order forced impulsive delay differential equation with damping term. Three factors-impulse, delay and damping that affect the interval qualitative properties of solutions of equations are taken into account together. The results obtained in this paper extend and generalize some of the the known results for forced impulsive differential equations. An example is provided to illustrate the main result.

Micropropulsion devices based on molecular acceleration by pulsed optical lattices

NASA Astrophysics Data System (ADS)

Shneider, Mikhail N.; Gimelshein, Sergey F.; Barker, Peter F.

2006-03-01

The ability of a traveling periodic optical potential to increase the thrust and specific impulse of microthrusters is investigated. Two flow regimes, high density and low density, are considered. The thrust from a micronozzle, with a stagnation pressure of 1 atm and temperature of 300 K, can be increased by more than an order of magnitude. These conditions can be achieved for a constant velocity lattice, produced by two near counterpropagating optical fields that are focused into the nozzle throat. A propulsion system that operates in low-density regime and is driven by molecules trapped by an accelerating optical lattice is proposed. It is shown that such a system has a potential to achieve a specific impulse of thousands of seconds.

Second Step: A Violence-Prevention Curriculum. Grades 4-5, Second Edition. Teacher's Guide.

ERIC Educational Resources Information Center

Committee for Children, Seattle, WA.

"Second Step" is a curriculum designed to reduce impulsive and aggressive behavior in children aged 9 through 12 years, increasing their levels of social competence by teaching skills in empathy, impulse control, and anger management. This guide is part of the "Second Step" series, which includes curricula for…

The Utility of Impulsive Bias and Altered Decision Making as Predictors of Drug Efficacy and Target Selection: Rethinking Behavioral Screening for Antidepressant Drugs.

PubMed

Marek, Gerard J; Day, Mark; Hudzik, Thomas J

2016-03-01

Cognitive dysfunction may be a core feature of major depressive disorder, including affective processing bias, abnormal response to negative feedback, changes in decision making, and increased impulsivity. Accordingly, a translational medicine paradigm predicts clinical action of novel antidepressants by examining drug-induced changes in affective processing bias. With some exceptions, these concepts have not been systematically applied to preclinical models to test new chemical entities. The purpose of this review is to examine whether an empirically derived behavioral screen for antidepressant drugs may screen for compounds, at least in part, by modulating an impulsive biasing of responding and altered decision making. The differential-reinforcement-of-low-rate (DRL) 72-second schedule is an operant schedule with a documented fidelity for discriminating antidepressant drugs from nonantidepressant drugs. However, a theoretical basis for this empirical relationship has been lacking. Therefore, this review will discuss whether response bias toward impulsive behavior may be a critical screening characteristic of DRL behavior requiring long inter-response times to obtain rewards. This review will compare and contrast DRL behavior with the five-choice serial reaction time task, a test specifically designed for assessing motoric impulsivity, with respect to psychopharmacological testing and the neural basis of distributed macrocircuits underlying these tasks. This comparison suggests that the existing empirical basis for the DRL 72-second schedule as a pharmacological screen for antidepressant drugs is complemented by a novel hypothesis that altering impulsive response bias for rodents trained on this operant schedule is a previously unrecognized theoretical cornerstone for this screening paradigm. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Second Step: A Violence-Prevention Curriculum. Grades 1-3, Second Edition. Teacher's Guide.

ERIC Educational Resources Information Center

Committee for Children, Seattle, WA.

"Second Step," grades 1-3 is a curriculum designed to reduce impulsive and aggressive behavior in children aged 6 through 9 years, and increase their levels of social competence by teaching skills in empathy, impulse control, and anger management. This curriculum is part of the "Second Step" series which includes curricula for…

Existence and stability of periodic solutions of an impulsive differential equation and application to CD8 T-cell differentiation.

PubMed

Girel, Simon; Crauste, Fabien

2018-06-01

Unequal partitioning of the molecular content at cell division has been shown to be a source of heterogeneity in a cell population. We propose to model this phenomenon with the help of a scalar, nonlinear impulsive differential equation (IDE). To study the effect of molecular partitioning at cell division on the effector/memory cell-fate decision in a CD8 T-cell lineage, we study an IDE describing the concentration of the protein Tbet in a CD8 T-cell, where impulses are associated to cell division. We discuss how the degree of asymmetry of molecular partitioning can affect the process of cell differentiation and the phenotypical heterogeneity of a cell population. We show that a moderate degree of asymmetry is necessary and sufficient to observe irreversible differentiation. We consider, in a second part, a general autonomous IDE with fixed times of impulse and a specific form of impulse function. We establish properties of the solutions of that equation, most of them obtained under the hypothesis that impulses occur periodically. In particular, we show how to investigate the existence of periodic solutions and their stability by studying the flow of an autonomous differential equation. Then we apply those properties to prove the results presented in the first part.

The Influence of Current Density and Magnetic Field Topography in Optimizing the Performance, Divergence, and Plasma Oscillations of High Specific Impulse Hall Thrusters

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Jankovsky, Robert S.

2003-01-01

Recent studies of xenon Hall thrusters have shown peak efficiencies at specific impulses of less than 3000 s. This was a consequence of modern Hall thruster magnetic field topographies, which have been optimized for 300 V discharges. On-going research at the NASA Glenn Research Center is investigating this behavior and methods to enhance thruster performance. To conduct these studies, a laboratory model Hall thruster that uses a pair of trim coils to tailor the magnetic field topography for high specific impulse operation has been developed. The thruster-the NASA-173Mv2 was tested to determine how current density and magnetic field topography affect performance, divergence, and plasma oscillations at voltages up to 1000 V. Test results showed there was a minimum current density and optimum magnetic field topography at which efficiency monotonically increased with voltage. At 1000 V, 10 milligrams per second the total specific impulse was 3390 s and the total efficiency was 60.8%. Plume divergence decreased at 400-1000 V, but increased at 300-400 V as the result of plasma oscillations. The dominant oscillation frequency steadily increased with voltage, from 14.5 kHz at 300 V, to 22 kHz at 1000 V. An additional oscillatory mode in the 80-90 kHz frequency range began to appear above 500 V. The use of trim coils to modify the magnetic field improved performance while decreasing plume divergence and the frequency and magnitude of plasma oscillations.

Space Storable Rocket Technology (SSRT) basic program

NASA Technical Reports Server (NTRS)

Chazen, M. L.; Mueller, T.; Casillas, A. R.; Huang, D.

1992-01-01

The Space Storable Rocket Technology Program (SSRT) was conducted to establish a technology for a new class of high performance and long life bipropellant engines using space storable propellants. The results are described. Task 1 evaluated several characteristics for a number of fuels to determine the best space storable fuel for use with LO2. The results indicated that LO2-N2H4 is the best propellant combination and provides the maximum mission/system capability maximum payload into GEO of satellites. Task 2 developed two models, performance and thermal. The performance model indicated the performance goal of specific impulse greater than or = 340 seconds (sigma = 204) could be achieved. The thermal model was developed and anchored to hot fire test data. Task 3 consisted of design, fabrication, and testing of a 200 lbf thrust test engine operating at a chamber pressure of 200 psia using LO2-N2H4. A total of 76 hot fire tests were conducted demonstrating performance greater than 340 (sigma = 204) which is a 25 second specific impulse improvement over the existing highest performance flight apogee type engines.

Preliminary Investigation of Performance and Starting Characteristics of Liquid Fluorine : Liquid Oxygen Mixtures with Jet Fuel

NASA Technical Reports Server (NTRS)

Rothenberg, Edward A; Ordin, Paul M

1954-01-01

The performance of jet fuel with an oxidant mixture containing 70 percent liquid fluorine and 30 percent liquid oxygen by weight was investigated in a 500-pound-thrust engine operating at a chamber pressure of 300 pounds per square inch absolute. A one-oxidant-on-one-fuel skewed-hole impinging-jet injector was evaluated in a chamber of characteristic length equal to 50 inches. A maximum experimental specific impulse of 268 pound-seconds per pound was obtained at 25 percent fuel, which corresponds to 96 percent of the maximum theoretical specific impulse based on frozen composition expansion. The maximum characteristic velocity obtained was 6050 feet per second at 23 percent fuel, or 94 percent of the theoretical maximum. The average thrust coefficient was 1.38 for the 500-pound thrust combustion-chamber nozzle used, which was 99 percent of the theoretical (frozen) maximum. Mixtures of fluorine and oxygen were found to be self-igniting with jet fuel with fluorine concentrations as low as 4 percent, when low starting propellant flow rated were used.

High temperature oxidation-resistant thruster research

NASA Technical Reports Server (NTRS)

Wooten, John R.; Lansaw, P. Tina

1990-01-01

A program was conducted for NASA-LeRC by Aerojet Propulsion Division to establish the technology base for a new class of long-life, high-performance, radiation-cooled bipropellant thrusters capable of operation at temperatures over 2200 C (4000 F). The results of a systematic, multi-year program are described starting with the preliminary screening tests which lead to the final material selection. Life greater than 15 hours was demonstrated on a workhorse iridium-lined rhenium chamber at chamber temperatures between 2000 and 2300 C (3700 and 4200 F). The chamber was fabricated by the Chemical Vapor Deposition at Ultramet. The program culminated in the design, fabrication, and hot-fire test of an NTO/MMH 22-N (5-lbF) class thruster containing a thin wall iridium-lined rhenium thrust chamber with a 150:1 area ratio nozzle. A specific impulse of 310 seconds was measured and front-end thermal management was achieved for steady state and several pulsing duty cycles. The resulting design represents a 20 second specific impulse improvement over conventional designs in which the use of disilicide coated columbium chambers limit operation to 1300 C (2400 F).

Impulse Noise Cancellation of Medical Images Using Wavelet Networks and Median Filters

PubMed Central

Sadri, Amir Reza; Zekri, Maryam; Sadri, Saeid; Gheissari, Niloofar

2012-01-01

This paper presents a new two-stage approach to impulse noise removal for medical images based on wavelet network (WN). The first step is noise detection, in which the so-called gray-level difference and average background difference are considered as the inputs of a WN. Wavelet Network is used as a preprocessing for the second stage. The second step is removing impulse noise with a median filter. The wavelet network presented here is a fixed one without learning. Experimental results show that our method acts on impulse noise effectively, and at the same time preserves chromaticity and image details very well. PMID:23493998

Analysis of gas turbine engines using water and oxygen injection to achieve high Mach numbers and high thrust

NASA Technical Reports Server (NTRS)

Henneberry, Hugh M.; Snyder, Christopher A.

1993-01-01

An analysis of gas turbine engines using water and oxygen injection to enhance performance by increasing Mach number capability and by increasing thrust is described. The liquids are injected, either separately or together, into the subsonic diffuser ahead of the engine compressor. A turbojet engine and a mixed-flow turbofan engine (MFTF) are examined, and in pursuit of maximum thrust, both engines are fitted with afterburners. The results indicate that water injection alone can extend the performance envelope of both engine types by one and one-half Mach numbers at which point water-air ratios reach 17 or 18 percent and liquid specific impulse is reduced to some 390 to 470 seconds, a level about equal to the impulse of a high energy rocket engine. The envelope can be further extended, but only with increasing sacrifices in liquid specific impulse. Oxygen-airflow ratios as high as 15 percent were investigated for increasing thrust. Using 15 percent oxygen in combination with water injection at high supersonic Mach numbers resulted in thrust augmentation as high as 76 percent without any significant decrease in liquid specific impulse. The stoichiometric afterburner exit temperature increased with increasing oxygen flow, reaching 4822 deg R in the turbojet engine at a Mach number of 3.5. At the transonic Mach number of 0.95 where no water injection is needed, an oxygen-air ratio of 15 percent increased thrust by some 55 percent in both engines, along with a decrease in liquid specific impulse of 62 percent. Afterburner temperature was approximately 4700 deg R at this high thrust condition. Water and/or oxygen injection are simple and straightforward strategies to improve engine performance and they will add little to engine weight. However, if large Mach number and thrust increases are required, liquid flows become significant, so that operation at these conditions will necessarily be of short duration.

Radiation energy receiver for laser and solar propulsion systems

NASA Technical Reports Server (NTRS)

Rault, D. F. G.; Hertzberg, A.

1983-01-01

The concept of remotely heating a rocket propellant with a high intensity radiant energy flux is especially attractive due to its high specific impulse and large payload mass capabilities. In this paper, a radiation receiver-thruster which is especially suited to the particular thermodynamic and spectral characteristics of highly concentrated solar energy is proposed. In this receiver, radiant energy is volumetrically absorbed within a hydrogen gas seeded with alkali metal vapors. The alkali atoms and molecules absorb the radiant flux and, subsequently, transfer their internal excitation to hydrogen molecules through collisional quenching. It is shown that such a radiation receiver would outperform a blackbody cavity type receiver in both efficiency and maximum operating temperatures. A solar rocket equipped with such a receiver-thruster would deliver thrusts of several hundred newtons at a specific impulse of 1000 seconds.

First Stage of a Highly Reliable Reusable Launch System

NASA Technical Reports Server (NTRS)

Kloesel, Kurt J.; Pickrel, Jonathan B.; Sayles, Emily L.; Wright, Michael; Marriott, Darin; Holland, Leo; Kuznetsov, Stephen

2009-01-01

Electromagnetic launch assist has the potential to provide a highly reliable reusable first stage to a space access system infrastructure at a lower overall cost. This paper explores the benefits of a smaller system that adds the advantages of a high specific impulse air-breathing stage and supersonic launch speeds. The method of virtual specific impulse is introduced as a tool to emphasize the gains afforded by launch assist. Analysis shows launch assist can provide a 278-s virtual specific impulse for a first-stage solid rocket. Additional trajectory analysis demonstrates that a system composed of a launch-assisted first-stage ramjet plus a bipropellant second stage can provide a 48-percent gross lift-off weight reduction versus an all-rocket system. The combination of high-speed linear induction motors and ramjets is identified, as the enabling technologies and benchtop prototypes are investigated. The high-speed response of a standard 60 Hz linear induction motor was tested with a pulse width modulated variable frequency drive to 150 Hz using a 10-lb load, achieving 150 mph. A 300-Hz stator-compensated linear induction motor was constructed and static-tested to 1900 lbf average. A matching ramjet design was developed for use on the 300-Hz linear induction motor.

Homotopy method for optimization of variable-specific-impulse low-thrust trajectories

NASA Astrophysics Data System (ADS)

Chi, Zhemin; Yang, Hongwei; Chen, Shiyu; Li, Junfeng

2017-11-01

The homotopy method has been used as a useful tool in solving fuel-optimal trajectories with constant-specific-impulse low thrust. However, the specific impulse is often variable for many practical solar electric power-limited thrusters. This paper investigates the application of the homotopy method for optimization of variable-specific-impulse low-thrust trajectories. Difficulties arise when the two commonly-used homotopy functions are employed for trajectory optimization. The optimal power throttle level and the optimal specific impulse are coupled with the commonly-used quadratic and logarithmic homotopy functions. To overcome these difficulties, a modified logarithmic homotopy function is proposed to serve as a gateway for trajectory optimization, leading to decoupled expressions of both the optimal power throttle level and the optimal specific impulse. The homotopy method based on this homotopy function is proposed. Numerical simulations validate the feasibility and high efficiency of the proposed method.

Nontoxic Hydroxylammonium Nitrate (HAN) Monopropellant Propulsion

NASA Technical Reports Server (NTRS)

McKechnie, Timothy N.

2015-01-01

Nontoxic monopropellants have been developed that provide better performance than toxic hydrazine. Formulations based on HAN have superior performance as compared to hydrazine with enhanced specific impulse (Isp), higher density and volumetric impulse, lower melting point, and much lower toxicity. However, HAN-based monopropellants require higher chamber temperatures (2,083 K vs. 883 K) to combust. Current hydrazine-based combustion chamber technology (Inconel® or niobium C103 and silicide coating) and catalyst (Shell 405) are inadequate. In Phase I, state-of-the-art iridium-lined rhenium chambers and innovative new foam catalysts were demonstrated in pulse and 10-second firings. Phase II developed and tested a flight-weight thruster for an environmentally green monopropellant.

Unique aspects of impulsive traits in substance use and overeating: specific contributions of common assessments of impulsivity.

PubMed

Beaton, Derek; Abdi, Hervé; Filbey, Francesca M

2014-11-01

Abstract Background: Impulsivity is a complex trait often studied in substance abuse and overeating disorders, but the exact nature of impulsivity traits and their contribution to these disorders are still debated. Thus, understanding how to measure impulsivity is essential for comprehending addictive behaviors. Identify unique impulsivity traits specific to substance use and overeating. Impulsive Sensation Seeking (ImpSS) and Barratt's Impulsivity scales (BIS) Scales were analyzed with a non-parametric factor analytic technique (discriminant correspondence analysis) to identify group-specific traits on 297 individuals from five groups: Marijuana (n = 88), Nicotine (n = 82), Overeaters (n = 27), Marijuauna + Nicotine (n = 63), and CONTROLs (n = 37). A significant overall factor structure revealed three components of impulsivity that explained respectively 50.19% (pperm < 0.0005), 24.18% (pperm < 0.0005), and 15.98% (pperm < 0.0005) of the variance. All groups were significantly different from one another. When analyzed together, the BIS and ImpSS produce a multi-factorial structure that identified the impulsivity traits specific to these groups. The group specific traits are (1) CONTROL: low impulse, avoids thrill-seeking behaviors; (2) Marijuana: seeks mild sensation, is focused and attentive; (3) Marijuana + Nicotine: pursues thrill-seeking, lacks focus and attention; (4) Nicotine: lacks focus and planning; (5) Overeating: lacks focus, but plans (short and long term). Our results reveal impulsivity traits specific to each group. This may provide better criteria to define spectrums and trajectories - instead of categories - of symptoms for substance use and eating disorders. Defining symptomatic spectrums could be an important step forward in diagnostic strategies.

Unique aspects of impulsive traits in substance use and overeating: specific contributions of common assessments of impulsivity

PubMed Central

Beaton, Derek; Abdi, Hervé; Filbey, Francesca M.

2015-01-01

Background Impulsivity is a complex trait often studied in substance abuse and overeating disorders, but the exact nature of impulsivity traits and their contribution to these disorders are still debated. Thus, understanding how to measure impulsivity is essential for comprehending addictive behaviors. Objectives Identify unique impulsivity traits specific to substance use and overeating. Methods Impulsive Sensation Seeking (ImpSS) and Barratt’s Impulsivity scales (BIS) Scales were analyzed with a non-parametric factor analytic technique (discriminant correspondence analysis) to identify group-specific traits on 297 individuals from five groups: Marijuana (n = 88), Nicotine (n = 82), Overeaters (n = 27), Marijuauna + Nicotine (n = 63), and Controls (n = 37). Results A significant overall factor structure revealed three components of impulsivity that explained respectively 50.19% (pperm<0.0005), 24.18% (pperm<0.0005), and 15.98% (pperm<0.0005) of the variance. All groups were significantly different from one another. When analyzed together, the BIS and ImpSS produce a multi-factorial structure that identified the impulsivity traits specific to these groups. The group specific traits are (1) Control: low impulse, avoids thrill-seeking behaviors; (2) Marijuana: seeks mild sensation, is focused and attentive; (3) Marijuana + Nicotine: pursues thrill-seeking, lacks focus and attention; (4) Nicotine: lacks focus and planning; (5) Overeating: lacks focus, but plans (short and long term). Conclusions Our results reveal impulsivity traits specific to each group. This may provide better criteria to define spectrums and trajectories – instead of categories – of symptoms for substance use and eating disorders. Defining symptomatic spectrums could be an important step forward in diagnostic strategies. PMID:25115831

Development of Selective Attention in Reflective and Impulsive Children.

ERIC Educational Resources Information Center

Weiner, Alan S.; Berzonsky, Michael D.

Selective attention was assessed in second, fourth, and sixth grade reflective and impulsive children with an incidental learning task using pictures (animal-household object pairs) or shapes (colored forms) as stimuli. By the sixth grade, reflective children displayed less incidental learning and greater central learning than impulsive children…

Psychopathic predators? Getting specific about the relation between psychopathy and violence

PubMed Central

Camp, Jacqueline P.; Skeem, Jennifer L.; Barchard, Kimberly; Lilienfeld, Scott O.; Poythress, Norman G.

2014-01-01

Objective The Psychopathy Checklist-Revised (PCL-R; Hare, 1991, 2003) is often used to assess risk of violence, perhaps based on the assumption that it captures emotionally detached individuals who are driven to prey upon others. This study is designed to assess the relation between (a) core interpersonal and affective traits of psychopathy and impulsive antisociality on the one hand, and (b) the risk of future violence, and patterns of motivation for past violence, on the other. Method A research team reliably assessed a sample of 158 male offenders for psychopathy, using both the interview-based PCL-R and the self-report Psychopathic Personality Inventory (PPI: Lilienfeld & Andrews, 1996). Then, a second, independent research team assessed offenders' lifetime patterns of violence and its motivation. After these baseline assessments, offenders were followed in prison and/or the community for up to one year to assess their involvement in three different forms of violence. Baseline and follow-up assessments included both interviews and reviews of official records. Results First, the PPI manifested incremental validity in predicting future violence over the PCL-R (but not vice versa) – and most of its predictive power derived solely from impulsive antisociality. Second, impulsive antisociality – not interpersonal and affective traits specific to psychopathy – were uniquely associated with instrumental lifetime patterns of past violence. The latter psychopathic traits are narrowly associated with deficits in motivation for violence (e.g., lack of fear; lack of provocation). Conclusion These findings and their consistency with some past research advise against broad generalizations about the relation between psychopathy and violence. PMID:23316742

Flight and Preflight Tests of a Ram Jet Burning Magnesium Slurry Fuel and Utilizing a Solid-propellant Gas Generator for Fuel Expulsion

NASA Technical Reports Server (NTRS)

Bartlett, Walter, A , jr; Hagginbotham, William K , Jr

1955-01-01

Data obtained from the first flight test of a ram jet utilizing a magnesium slurry fuel are presented. The ram jet accelerated from a Mach number of 1.75 to a Mach number of 3.48 in 15.5 seconds. During this period a maximum values of air specific impulse and gross thrust coefficient were calculated to be 151 seconds and 0.658, respectively. The rocket gas generator used as a fuel-pumping system operated successfully.

Second Step: A Violence-Prevention Curriculum. Preschool-Kindergarten (Ages 4-6). Teacher's Guide.

ERIC Educational Resources Information Center

Committee for Children, Seattle, WA.

"Second Step" for preschoolers and kindergartners is a curriculum kit designed to reduce impulsive and aggressive behavior in young children and to increase their levels of social competence by teaching skills in empathy, impulse control, and anger management. The kit, which is part of a series that includes curricula for grades 1-3,…

Apollo 16, LM-11 descent propulsion system final flight evaluation

NASA Technical Reports Server (NTRS)

Avvenire, A. T.

1974-01-01

The performance of the LM-11 descent propulsion system during the Apollo 16 missions was evaluated and found satisfactory. The average engine effective specific impulse was 0.1 second higher than predicted, but well within the predicted one sigma uncertainty of 0.2 seconds. Several flight measurement discrepancies existed during the flight as follows: (1) the chamber pressure transducer had a noticeable drift, exhibiting a maximum error of about 1.5 psi at approximately 130 seconds after engine ignition, (2) the fuel and oxidizer interface pressure measurements appeared to be low during the entire flight, and (3) the fuel propellant quantity gaging system did not perform within expected accuracies.

Impulsive Driving: Definition and Measurement Using the I-Driving Scale (IDS).

PubMed

Pérez-Moreno, Elisa; Hernández-Lloreda, María José; Gallego-Largo, Trinidad Ruiz; Castellanos, Miguel Ángel

2015-11-27

Impulsivity has been widely studied in the context of traffic. The trait is believed to be the root of some accidents, along with other variables like aggression and anger. The present research objective is to develop a new scale - the I-Driving Scale (IDS) - to evaluate and measure the construct of impulsivity in specific driving situations. To that end, two studies were conducted, with 162 and 107 participants, respectively. In both studies, participants were recruited via their social networks, and answered anonymously. In addition to the IDS, they completed the Use the Vehicle to Express Anger subscale of the Driving Anger Expression Inventory (DAX), the Driving Anger Scale (DAS), and the Barratt Impulsivity Scale (BIS11), and also provided demographic information. The final scale had 11 items falling into two factors: impatience, and aggressiveness/abruptness. The results show a high consistency (αT = .81, αI = .70, and αA = .85 in the first study; αT = .83, αI = .80, and αA = .88 in the second study). Statistical results of Exploratory Factor Analysis in the first sample indicated goodness of fit to a two-factor model (RMSR = .057, GFI = .98). The second study confirmed that factorial structure (χ2/df = 80.50/43 = 1.87, RMSEA = .088, CFI = .94, TLI = .92). Correlations with other measures indicated the Impatience subscale is associated with different expressions of anger behind the wheel, and directly correlated with the loss of driver's license points. Furthermore, the Aggressiveness or Abruptness subscale was associated with more mechanical aspects, and correlated inversely with age.

On the interpretation of kernels - Computer simulation of responses to impulse pairs

NASA Technical Reports Server (NTRS)

Hung, G.; Stark, L.; Eykhoff, P.

1983-01-01

A method is presented for the use of a unit impulse response and responses to impulse pairs of variable separation in the calculation of the second-degree kernels of a quadratic system. A quadratic system may be built from simple linear terms of known dynamics and a multiplier. Computer simulation results on quadratic systems with building elements of various time constants indicate reasonably that the larger time constant term before multiplication dominates in the envelope of the off-diagonal kernel curves as these move perpendicular to and away from the main diagonal. The smaller time constant term before multiplication combines with the effect of the time constant after multiplication to dominate in the kernel curves in the direction of the second-degree impulse response, i.e., parallel to the main diagonal. Such types of insight may be helpful in recognizing essential aspects of (second-degree) kernels; they may be used in simplifying the model structure and, perhaps, add to the physical/physiological understanding of the underlying processes.

Design and Performance Estimates of an Ablative Gallium Electromagnetic Thruster

NASA Technical Reports Server (NTRS)

Thomas, Robert E.

2012-01-01

The present study details the high-power condensable propellant research being conducted at NASA Glenn Research Center. The gallium electromagnetic thruster is an ablative coaxial accelerator designed to operate at arc discharge currents in the range of 10-25 kA. The thruster is driven by a four-parallel line pulse forming network capable of producing a 250 microsec pulse with a 60 kA amplitude. A torsional-type thrust stand is used to measure the impulse of a coaxial GEM thruster. Tests are conducted in a vacuum chamber 1.5 m in diameter and 4.5 m long with a background pressure of 2 microtorr. Electromagnetic scaling calculations predict a thruster efficiency of 50% at a specific impulse of 2800 seconds.

Advanced OTV engine concepts

NASA Technical Reports Server (NTRS)

Zachary, A. T.

1984-01-01

The results and status of engine technology efforts to date and related company funded activities are presented. Advanced concepts in combustors and injectors, high speed turbomachinery, controls, and high-area-ratio nozzles that package within a short length result is engines with specific impulse values 35 to 46 seconds higher than those now realized by operational systems. The improvement in life, reliability, and maintainability of OTV engines are important.

Exploring the victimization‒early substance misuse relationship: In search of moderating and mediating effects.

PubMed

Walters, Glenn D; Espelage, Dorothy L

2018-07-01

This study was designed to address two research questions. The first research question asked whether physical abuse victimization at the hands of parents/guardians, bullying victimization at the hands of peers, and the abuse x bullying interaction encouraged early involvement in substance misuse. The second research question inquired as to whether the victimization‒substance misuse relationship was mediated by variables proposed by various theories and research studies-specifically, cognitive impulsivity, negative affect, and low self-esteem. A moderated mediation hypothesis was tested in a group of 865 (417 boys, 448 girls) schoolchildren from the Illinois Study of Bullying and Sexual Violence who were 10 to 15 years of age at the time of initial contact. A path analysis performed with three waves of data revealed that physical abuse and bullying victimization predicted substance misuse with mediation by cognitive impulsivity, but there was no evidence of moderation. On the basis of these results, it was concluded that victimization, whether through parental physical abuse or peer bullying, increases cognitive impulsivity, and that cognitive impulsivity, in turn, encourages early involvement in substance misuse. The practical implications of these results are that interventions designed to counter cognitive impulsivity and encourage cognitive control may be effective in preventing children traumatized by physical abuse and bullying from entering the early stages of a drug or substance using lifestyle. Copyright © 2018 Elsevier Ltd. All rights reserved.

Increased self-reported impulsivity in methamphetamine users maintaining drug abstinence.

PubMed

Jones, Hannah W; Dean, Andy C; Price, Kimberly A; London, Edythe D

2016-09-01

Impulsivity has been proposed as an important factor in the initiation and maintenance of addiction. Indirect evidence suggests that some methamphetamine users report less impulsivity when they are using methamphetamine compared to when abstaining from drug use, but this hypothesis has not been directly tested. In this study, self-reports of impulsivity were obtained from 32 methamphetamine-dependent (DSM-IV) research participants and 41 healthy control subjects, using the Barratt Impulsiveness Scale-11. The methamphetamine users were assessed during an active period of methamphetamine use, as determined through urinalysis, and again after approximately 1 week of confirmed abstinence. Control subjects likewise completed two assessments. A subset of participants also completed serial assessments of the Beck Depression Inventory (Methamphetamine Group, N = 17, Control Group, N = 38) and the Methamphetamine Withdrawal Questionnaire (Methamphetamine Group, N = 12). There was a significant interaction of group with time on impulsivity (p = 0.044), reflecting a significant increase from the first to the second assessment in the methamphetamine users (p = 0.013), but no change among healthy control subjects. In contrast, depressive and withdrawal symptoms significantly decreased between the first and second assessments in the methamphetamine users (ps ≤0.01). Change in impulsivity in methamphetamine users was not significantly correlated with change in withdrawal or depression (ps >0.05). These findings suggest that methamphetamine users report more impulsivity when abstaining from drug use, an effect that is not significantly related to methamphetamine withdrawal. Attenuation of impulsivity may reinforce continued methamphetamine use in these individuals.

Studies of Fission Fragment Rocket Engine Propelled Spacecraft

NASA Technical Reports Server (NTRS)

Werka, Robert O.; Clark, Rodney; Sheldon, Rob; Percy, Thomas K.

2014-01-01

The NASA Office of Chief Technologist has funded from FY11 through FY14 successive studies of the physics, design, and spacecraft integration of a Fission Fragment Rocket Engine (FFRE) that directly converts the momentum of fission fragments continuously into spacecraft momentum at a theoretical specific impulse above one million seconds. While others have promised future propulsion advances if only you have the patience, the FFRE requires no waiting, no advances in physics and no advances in manufacturing processes. Such an engine unequivocally can create a new era of space exploration that can change spacecraft operation. The NIAC (NASA Institute for Advanced Concepts) Program Phase 1 study of FY11 first investigated how the revolutionary FFRE technology could be integrated into an advanced spacecraft. The FFRE combines existent technologies of low density fissioning dust trapped electrostatically and high field strength superconducting magnets for beam management. By organizing the nuclear core material to permit sufficient mean free path for escape of the fission fragments and by collimating the beam, this study showed the FFRE could convert nuclear power to thrust directly and efficiently at a delivered specific impulse of 527,000 seconds. The FY13 study showed that, without increasing the reactor power, adding a neutral gas to the fission fragment beam significantly increased the FFRE thrust through in a manner analogous to a jet engine afterburner. This frictional interaction of gas and beam resulted in an engine that continuously produced 1000 pound force of thrust at a delivered impulse of 32,000 seconds, thereby reducing the currently studied DRM 5 round trip mission to Mars from 3 years to 260 days. By decreasing the gas addition, this same engine can be tailored for much lower thrust at much higher impulse to match missions to more distant destinations. These studies created host spacecraft concepts configured for manned round trip journeys. While the vehicles are very large, they are primarily made up of a habitat payload on one end, the engine on the opposite end and a connecting spine containing radiator acreage needed to reject the heat of this powerful, but inefficient engine. These studies concluded that the engine and spacecraft are within today's technology, could be built, tested, launched on several SLS launchers, integrated, checked out, maintained at an in-space LEO base, and operated for decades just as Caribbean cruise ships operate today. The nuclear issues were found to be far less daunting that [than for] current nuclear engines. The FFRE produces very small amounts of radioactive efflux compared to their impulse, easily contained in an evacuated "bore-hole" test site. The engine poses no launch risk since it is simply a structure containing no fissionable material. The nuclear fuel is carried to orbit in containers highly crash-proofed for launch accidents from which it, in a liquid medium, is injected into the FFRE. The radioactive exhaust, with a velocity above 300 kilometers per second rapidly leaves the solar system.

Specific Impulse Definition for Ablative Laser Propulsion

NASA Technical Reports Server (NTRS)

Herren, Kenneth A.; Gregory, Don A.

2004-01-01

The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

Preliminary performance and life evaluations of a 2-kW arcjet

NASA Technical Reports Server (NTRS)

Morren, W. Earl; Curran, Francis M.

1991-01-01

The first results of a program to expand the operational envelope of low-power arcjets to higher specific impulse and power levels are presented. The performance of a kW-class laboratory model arcjet thruster was characterized at three mass flow rates of a 2:1 mixture of hydrogen and nitrogen at power levels ranging from 1.0 to 2.0 kW. This same thruster was then operated for a total of 300 h at a specific impulse and power level of 550 s and 2.0 kW, respectively, in three continuous 100-h sessions. Thruster operation during the three test segments was stable, and no measurable performance degradation was observed during the test series. Substantial cathode erosion was observed during an inspection following the second 100-h test segment. Most notable was the migration of material from the center of the cathode tip to a ring around a large crater. The anode sustained no significant damage during the endurance test segments. Some difficulty was encountered during start-up after disassembly and inspection following the second 100-h test segment, which caused constrictor erosion. This resulted in a reduced flow restriction and arc chamber pressure, which in turn caused a reduction in the arc impedance.

Trait impulsivity components correlate differently with proactive and reactive control

PubMed Central

Huang, Shihua; Zhu, Zude; Zhang, Wei; Chen, Yu; Zhen, Shuangju

2017-01-01

The relationship between impulsivity and cognitive control is still unknown. We hypothesized that trait impulsivity would differentially correlate with specific cognitive control processes. Trait impulsivity was measured by the Barratt Impulsiveness Scale, which assesses motor, attention, and non-planning impulsiveness components. Cognitive control was measured by a hybrid-designed Stroop task, which distinguishes proactive and reactive control. Thirty-three participants performed the Stroop task while they were scanned by functional magnetic resonance imaging. Proactive and reactive control involved increased activity in the fronto-parietal network, and brain activity was associated with impulsivity scores. Specifically, higher motor impulsiveness was associated with a larger proactive control effect in the inferior parietal lobule and a smaller reactive control effect in the right dorsolateral prefrontal cortex (DLPFC) and anterior cingulate contex. Higher attention impulsivity was associated with a smaller proactive control effect in the right DLPFC. Such a correlation pattern suggests that impulsivity trait components are attributable to different cognitive control subsystems. PMID:28423021

Sex differences in impulsive action and impulsive choice.

PubMed

Weafer, Jessica; de Wit, Harriet

2014-11-01

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. © 2013.

Sex differences in impulsive action and impulsive choice

PubMed Central

Weafer, Jessica; de Wit, Harriet

2013-01-01

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

Trait impulsivity components correlate differently with proactive and reactive control.

PubMed

Huang, Shihua; Zhu, Zude; Zhang, Wei; Chen, Yu; Zhen, Shuangju

2017-01-01

The relationship between impulsivity and cognitive control is still unknown. We hypothesized that trait impulsivity would differentially correlate with specific cognitive control processes. Trait impulsivity was measured by the Barratt Impulsiveness Scale, which assesses motor, attention, and non-planning impulsiveness components. Cognitive control was measured by a hybrid-designed Stroop task, which distinguishes proactive and reactive control. Thirty-three participants performed the Stroop task while they were scanned by functional magnetic resonance imaging. Proactive and reactive control involved increased activity in the fronto-parietal network, and brain activity was associated with impulsivity scores. Specifically, higher motor impulsiveness was associated with a larger proactive control effect in the inferior parietal lobule and a smaller reactive control effect in the right dorsolateral prefrontal cortex (DLPFC) and anterior cingulate contex. Higher attention impulsivity was associated with a smaller proactive control effect in the right DLPFC. Such a correlation pattern suggests that impulsivity trait components are attributable to different cognitive control subsystems.

Does impulsivity predict outcome in treatment for binge eating disorder? A multimodal investigation.

PubMed

Manasse, Stephanie M; Espel, Hallie M; Schumacher, Leah M; Kerrigan, Stephanie G; Zhang, Fengqing; Forman, Evan M; Juarascio, Adrienne S

2016-10-01

Multiple dimensions of impulsivity (e.g., affect-driven impulsivity, impulsive inhibition - both general and food-specific, and impulsive decision-making) are associated with binge eating pathology cross-sectionally, yet the literature on whether impulsivity predicts treatment outcome is limited. The present pilot study explored impulsivity-related predictors of 20-week outcome in a small open trial (n = 17) of a novel treatment for binge eating disorder. Overall, dimensions of impulsivity related to emotions (i.e., negative urgency) and food cues emerged as predictors of treatment outcomes (i.e., binge eating frequency and global eating pathology as measured by the Eating Disorders Examination), while more general measures of impulsivity were statistically unrelated to global eating pathology or binge frequency. Specifically, those with higher levels of negative urgency at baseline experienced slower and less pronounced benefit from treatment, and those with higher food-specific impulsivity had more severe global eating pathology at baseline that was consistent at post-treatment and follow-up. These preliminary findings suggest that patients high in negative urgency and with poor response inhibition to food cues may benefit from augmentation of existing treatments to achieve optimal outcomes. Future research will benefit from replication with a larger sample, parsing out the role of different dimensions of impulsivity in treatment outcome for eating disorders, and identifying how treatment can be improved to accommodate higher levels of baseline impulsivity. Copyright © 2016 Elsevier Ltd. All rights reserved.

The moderating role of social support on the relationship between impulsivity and suicide risk.

PubMed

Kleiman, Evan M; Riskind, John H; Schaefer, Karen E; Weingarden, Hilary

2012-01-01

Suicide is the second leading cause of death among college students. There has been considerable research into risk factors for suicide, such as impulsivity, but considerably less research on protective factors. The present study examines the role that social support plays in the relationship between impulsivity and suicide risk. Participants were 169 undergraduates who completed self-report measures of impulsivity and social support. Suicide risk was assessed using an interview measure. Social support moderates the relationship between impulsivity and suicide risk, such that those who are highly impulsive are less likely to be at risk for suicide if they also have high levels of social support. Social support can be a useful buffer to suicide risk for at-risk individuals who are highly impulsive.

Electrostatic Plasma Accelerator (EPA)

NASA Technical Reports Server (NTRS)

Brophy, John R.; Aston, Graeme

1995-01-01

The application of electric propulsion to communications satellites, however, has been limited to the use of hydrazine thrusters with electric heaters for thrust and specific impulse augmentation. These electrothermal thrusters operate at specific impulse levels of approximately 300 s with heater powers of about 500 W. Low power arcjets (1-3 kW) are currently being investigated as a way to increase specific impulse levels to approximately 500 s. Ion propulsion systems can easily produce specific impulses of 3000 s or greater, but have yet to be applied to communications satellites. The reasons most often given for not using ion propulsion systems are their high level of overall complexity, low thrust with long burn times, and the difficulty of integrating the propulsion system into existing commercial spacecraft busses. The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass.

The Story of the Nuclear Rocket: Back to the Future

NASA Astrophysics Data System (ADS)

Dewar, James A.

2002-01-01

The United States had a nuclear rocket development program from 1955-1973 called Project Rover/NERVA. Twenty reactor tests demonstrated conclusively the superiority, flexibility and reliability of nuclear rocket engines over their chemical counterparts. This paper surveys the technical accomplishments from that perspective, to help illustrate why many call for the program's reestablishment. Most focus on the large NERVA, but this review will consider the little known Small Nuclear Engine. KIWI-B1B was one of the first tests in which nuclear rockets demonstrated their superiority. It ejected its core as it rose to 1000MW (a megawatt equals 50 pounds of thrust). This seems contradictory, how can a `failure' demonstrate superiority? Precisely in this: the reactor remained controllable going to and from 1000MW, still ejecting its core, but still turning out power. That gave insurance to a mission. A solid or liquid chemical engine suffering similar damage would likely shutdown or blow up. KIWI-TNT and Phoebus-1A had planned and unplanned accidents. That verified the safety of nuclear engines in launch operations. NRX/EST and XE-Prime proved they could startup reliably under their own power in a simulated space environment and change power without loss of specific impulse or control, from 20MW to 1000MW and back. That gave flexibility for mid-course corrections, maneuvering between orbits or breaking into orbit. Pewee and the Nuclear Furnace tested fuels to achieve 10 hours of engine operation with 60 recycles (stops and starts). That meant an engine could perform multiple missions. Work started on fuels promising1000 seconds of specific impulse. That meant increased power and payload capacity and speed. This contrasts with the 450 seconds of LOX/LH2. The NERVA of 1971 would be 1500MW, with 10/60 capability and 825 seconds of a specific impulse. Later generation NERVAs would be in excess of 1000 seconds, 3000MW and 10/60. The Nixon Administration cancelled it in 1971. After its demise, the Small Nuclear Engine appeared for unmanned missions. To fit in the space shuttle's 15 by 60 foot cargo bay, the 10 foot long engine would be 400MW, weigh 5600 pounds and use slush hydrogen. That left 50 feet and almost 60,000 pounds for the tank, propellant and payload that could vary in size, but it was nominally 5 tons. It would cost 500 million (in1972 dollars) and take a decade to develop. It had NERVA's operating characteristics, but subsequent generation systems envisioned longer engine life and recycle capability and specific impulses of 1000+ seconds. Nixon ended this in 1973. By reconsidering it instead of a nuclear electric engine that serves only space science, the nation could gain a fast, powerful system that would radically change most future unmanned space missions. With its recycle capability, a single engine could ferry large scientific payloads swiftly throughout the solar system. Yet it also could propel heavy national security and commercial payloads to geo-synchronous orbit. NASA might even offer a satellite retrieval service. Thus, one lesson is clear: it is 1960s era technology, but the Small Engine is not obsolete. If developed, it would serve not just one, but three users yet have growth potential for decades for an ever more expansive space program.

Intrinsic Network Connectivity Patterns Underlying Specific Dimensions of Impulsiveness in Healthy Young Adults.

PubMed

Kubera, Katharina M; Hirjak, Dusan; Wolf, Nadine D; Sambataro, Fabio; Thomann, Philipp A; Wolf, R Christian

2018-05-01

Impulsiveness is a central human personality trait and of high relevance for the development of several mental disorders. Impulsiveness is a multidimensional construct, yet little is known about dimension-specific neural correlates. Here, we address the question whether motor, attentional and non-planning components, as measured by the Barratt Impulsiveness Scale (BIS-11), are associated with distinct or overlapping neural network activity. In this study, we investigated brain activity at rest and its relationship to distinct dimensions of impulsiveness in 30 healthy young adults (m/f = 13/17; age mean/SD = 26.4/2.6 years) using resting-state functional magnetic resonance imaging at 3T. A spatial independent component analysis and a multivariate model selection strategy were used to identify systems loading on distinct impulsivity domains. We first identified eight networks for which we had a-priori hypotheses. These networks included basal ganglia, cortical motor, cingulate and lateral prefrontal systems. From the eight networks, three were associated with impulsiveness measures (p < 0.05, FDR corrected). There were significant relationships between right frontoparietal network function and all three BIS domains. Striatal and midcingulate network activity was associated with motor impulsiveness only. Within the networks regionally confined effects of age and gender were found. These data suggest distinct and overlapping patterns of neural activity underlying specific dimensions of impulsiveness. Motor impulsiveness appears to be specifically related to striatal and midcingulate network activity, in contrast to a domain-unspecific right frontoparietal system. Effects of age and gender have to be considered in young healthy samples.

Subjective field study of response to impulsive helicopter noise

NASA Technical Reports Server (NTRS)

Powell, C. A.

1981-01-01

Subjects, located outdoors and indoors, judged the noisiness and other subjective noise characteristics of flyovers of two helicopters and a propeller driven airplane as part of a study of the effects of impulsiveness on the subjective response to helicopter noise. In the first experiment, the impulsive characteristics of one helicopter was controlled by varying the main rotor speed while maintaining a constant airspeed in level flight. The second experiment which utilized only the helicopters, included descent and level flight operations. The more impulsive helicopter was consistently judged less noisy than the less impulsive helicopter at equal effective perceived noise levels (EPNL). The ability of EPNL to predict noisiness was not improved by the addition of either of two proposed impulse corrections. A subjective measure of impulsiveness, however, which was not significantly related to the proposed impulse corrections, was found to improve the predictive ability of EPNL.

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

PubMed

Abe, Takeru; Hagihara, Akihito; Nobutomo, Koichi

2010-10-01

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.

Closed-Form and Numerically-Stable Solutions to Problems Related to the Optimal Two-Impulse Transfer Between Specified Terminal States of Keplerian Orbits

NASA Technical Reports Server (NTRS)

Senent, Juan

2011-01-01

The first part of the paper presents some closed-form solutions to the optimal two-impulse transfer between fixed position and velocity vectors on Keplerian orbits when some constraints are imposed on the magnitude of the initial and final impulses. Additionally, a numerically-stable gradient-free algorithm with guaranteed convergence is presented for the minimum delta-v two-impulse transfer. In the second part of the paper, cooperative bargaining theory is used to solve some two-impulse transfer problems when the initial and final impulses are carried by different vehicles or when the goal is to minimize the delta-v and the time-of-flight at the same time.

A meta-analytic review of the relationship between adolescent risky sexual behavior and impulsivity across gender, age, and race.

PubMed

Dir, Allyson L; Coskunpinar, Ayca; Cyders, Melissa A

2014-11-01

Impulsivity is frequently included as a risk factor in models of adolescent sexual risk-taking; however, findings on the magnitude of association between impulsivity and risky sexual behavior are variable across studies. The aims of the current meta-analysis were to examine (1) how specific impulsivity traits relate to specific risky sexual behaviors in adolescents, and (2) how the impulsivity-risky sex relationship might differ across gender, age, and race. Eighty-one studies were meta-analyzed using a random effects model to examine the overall impulsivity-risky sex relationship and relationships among specific impulsivity traits and risky sexual behaviors. Overall, results revealed a significant, yet small, association between impulsivity and adolescent risky sexual behavior (r=0.19, p<0.001) that did not differ across impulsivity trait. A pattern of stronger effects was associated with risky sexual behaviors as compared to negative outcomes related to these behaviors. Gender moderated the overall relationship (β=0.22, p=0.04), such that effect sizes were significantly larger in samples with more females. Age, race, study design, and sample type did not moderate the relationship, although there was a pattern suggesting smaller effects for adolescents in juvenile detention settings. Adolescent samples with more females showed a larger impulsivity-risky sex relationship, suggesting that impulsivity may be a more important risk factor for risky sex among adolescent females. Research and treatment should consider gender differences when investigating the role of impulsivity in adolescent sexual risk-taking. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effect of ITE and nozzle exit cone erosion on specific impulse of solid rocket motors

NASA Astrophysics Data System (ADS)

Smith-Kent, Randall; Ridder, Jeffrey P.; Loh, Hai-Tien; Abel, Ralph

1993-06-01

Specific impulse loss due to the use of a slowly eroding integral throat entrance, or a throat insert, with a faster eroding nozzle exit cone is studied. It is suggested that an oblique shock wave produced by step-off erosion results in loss of specific impulse. This is studied by use of a shock capturing CFD method. The shock loss predictions for first-stage Peacekeeper and Castor 25 motors are found to match the trends of the test data. This work suggests that a loss mechanism, previously unaccounted, should be considered in the specific impulse prediction procedure for nozzles with step-off exit cone erosion.

Investigation of helicopter rotor blade/wake interactive impulsive noise

NASA Technical Reports Server (NTRS)

Miley, S. J.; Hall, G. F.; Vonlavante, E.

1987-01-01

An analysis of the Tip Aerodynamic/Aeroacoustic Test (TAAT) data was performed to identify possible aerodynamic sources of blade/vortex interaction (BVI) impulsive noise. The identification is based on correlation of measured blade pressure time histories with predicted blade/vortex intersections for the flight condition(s) where impulsive noise was detected. Due to the location of the recording microphones, only noise signatures associated with the advancing blade were available, and the analysis was accordingly restricted to the first and second azimuthal quadrants. The results show that the blade tip region is operating transonically in the azimuthal range where previous BVI experiments indicated the impulsive noise to be. No individual blade/vortex encounter is identifiable in the pressure data; however, there is indication of multiple intersections in the roll-up region which could be the origin of the noise. Discrete blade/vortex encounters are indicated in the second quadrant; however, if impulsive noise were produced here, the directivity pattern would be such that it was not recorded by the microphones. It is demonstrated that the TAAT data base is a valuable resource in the investigation of rotor aerodynamic/aeroacoustic behavior.

Electromagnetic propulsion for spacecraft

NASA Technical Reports Server (NTRS)

Myers, Roger M.

1993-01-01

Three electromagnetic propulsion technologies, solid propellant pulsed plasma thrusters (PPT), magnetoplasmadynamic (MPD) thrusters, and pulsed inductive thrusters (PIT), were developed for application to auxiliary and primary spacecraft propulsion. Both the PPT and MPD thrusters were flown in space, though only PPT's were used on operational satellites. The performance of operational PPT's is quite poor, providing only approximately 8 percent efficiency at approximately 1000 s specific impulse. However, laboratory PPT's yielding 34 percent efficiency at 2000 s specific impulse were extensively tested, and peak performance levels of 53 percent efficiency at 5170 s specific impulse were demonstrated. MPD thrusters were flown as experiments on the Japanese MS-T4 spacecraft and the Space Shuttle and were qualified for a flight in 1994. The flight MPD thrusters were pulsed, with a peak performance of 22 percent efficiency at 2500 s specific impulse using ammonia propellant. Laboratory MPD thrusters were demonstrated with up to 70 percent efficiency and 700 s specific impulse using lithium propellant. While the PIT thruster has never been flown, recent performance measurements using ammonia and hydrazine propellants are extremely encouraging, reaching 50 percent efficiency for specific impulses between 4000 to 8000 s. The fundamental operating principles, performance measurements, and system level design for the three types of electromagnetic thrusters are reviewed, and available data on flight tests are discussed for the PPT and MPD thrusters.

Understanding Impulsivity among Children with Specific Learning Disabilities in Inclusion Schools

ERIC Educational Resources Information Center

Al-Dababneh, Kholoud Adeeb; Al-Zboon, Eman K.

2018-01-01

Impulsive behavior is a characteristic of children with specific learning disabilities (SLD), and is related to learning ability. The present study aims to identify impulsivity behavior in children with SLD who attend inclusion schools, from their resource room teachers' perspectives. A 31-item questionnaire that addressed four subscales was…

Impulsivity, perceived self-regulatory success in dieting, and body mass in children and adolescents: A moderated mediation model.

PubMed

Meule, Adrian; Hofmann, Johannes; Weghuber, Daniel; Blechert, Jens

2016-12-01

Impulsivity has been suggested to contribute to overeating and obesity. However, findings are inconsistent and it appears that only specific facets of impulsivity are related to eating-related variables and to body mass. In the current study, relationships between self-reported impulsivity, perceived self-regulatory success in dieting, and objectively measured body mass were examined in N = 122 children and adolescents. Scores on attentional and motor impulsivity interactively predicted perceived self-regulatory success in dieting, but not body mass: Higher attentional impulsivity was associated with lower perceived self-regulatory success at high levels of motor impulsivity, but not at low levels of motor impulsivity. A moderated mediation model revealed an indirect effect of attentional and motor impulsivity on body mass, which was mediated by perceived self-regulatory success in dieting. Thus, results show that only specific facets of impulsivity are relevant in eating- and weight-regulation and interact with each other in the prediction of these variables. These facets of impulsivity, however, are not directly related to higher body mass, but indirectly via lower success in eating-related self-regulation in children and adolescents. Copyright © 2016 Elsevier Ltd. All rights reserved.

Overlapping and disease specific trait, response, and reflection impulsivity in adolescents with first-episode schizophrenia spectrum disorders or attention-deficit/hyperactivity disorder.

PubMed

Jepsen, J R M; Rydkjaer, J; Fagerlund, B; Pagsberg, A K; Jespersen, R Av F; Glenthøj, B Y; Oranje, B

2018-03-01

Schizophrenia and attention-deficit/hyperactivity disorder (ADHD) are developmental disorders with shared clinical characteristics such as cognitive impairments and impulsivity. Impulsivity is a core feature of ADHD and an important factor in aggression, violence, and substance use in schizophrenia. Based on the hypothesis that schizophrenia and ADHD represent a continuum of neurodevelopmental impairments, the aim was to identify overlapping and disease specific forms of impulsivity. Adolescents between 12 and 17 years of age were assessed with the Schedule for Affective Disorders and Schizophrenia for School-aged Children - Present and Lifetime Version. Subjects with early-onset, first-episode schizophrenia spectrum disorders (EOS) (N = 29) or ADHD (N = 29) and healthy controls (N = 45) were compared on two performance measures (Information Sampling Task, Stop Signal Task) and a subjective personality trait measure of impulsivity (Barratt Impulsiveness Scale, Version 11 (BIS-11)). Significantly increased reflection impulsivity was observed in ADHD but not in the EOS group. No significant response inhibition deficits (stop signal reaction time) were found in the two clinical groups. The ADHD and the EOS group showed significantly increased motor, attentional, and non-planning subtraits of impulsivity. Impaired pre-decisional information gathering appeared to be specific for ADHD while the information gathering was not significantly reduced in subjects with EOS. Neither the ADHD nor EOS group showed impaired response inhibition but shared increased personality subtraits of attentional, non-planning, and motor impulsivity although the latter was significantly more pronounced in ADHD. These increased subtraits of impulsivity may reflect diagnostic non-specific neurodevelopmental impairments in ADHD and EOS in adolescence.

Genetic and Modeling Approaches Reveal Distinct Components of Impulsive Behavior

PubMed Central

Nautiyal, Katherine M; Wall, Melanie M; Wang, Shuai; Magalong, Valerie M; Ahmari, Susanne E; Balsam, Peter D; Blanco, Carlos; Hen, René

2017-01-01

Impulsivity is an endophenotype found in many psychiatric disorders including substance use disorders, pathological gambling, and attention deficit hyperactivity disorder. Two behavioral features often considered in impulsive behavior are behavioral inhibition (impulsive action) and delayed gratification (impulsive choice). However, the extent to which these behavioral constructs represent distinct facets of behavior with discrete biological bases is unclear. To test the hypothesis that impulsive action and impulsive choice represent statistically independent behavioral constructs in mice, we collected behavioral measures of impulsivity in a single cohort of mice using well-validated operant behavioral paradigms. Mice with manipulation of serotonin 1B receptor (5-HT1BR) expression were included as a model of disordered impulsivity. A factor analysis was used to characterize correlations between the measures of impulsivity and to identify covariates. Using two approaches, we dissociated impulsive action from impulsive choice. First, the absence of 5-HT1BRs caused increased impulsive action, but not impulsive choice. Second, based on an exploratory factor analysis, a two-factor model described the data well, with measures of impulsive action and choice separating into two independent factors. A multiple-indicator multiple-causes analysis showed that 5-HT1BR expression and sex were significant covariates of impulsivity. Males displayed increased impulsivity in both dimensions, whereas 5-HT1BR expression was a predictor of increased impulsive action only. These data support the conclusion that impulsive action and impulsive choice are distinct behavioral phenotypes with dissociable biological influences that can be modeled in mice. Our work may help inform better classification, diagnosis, and treatment of psychiatric disorders, which present with disordered impulsivity. PMID:27976680

Teacher Perceptions of the Classroom Behavior of Reflective and Impulsive Children

ERIC Educational Resources Information Center

McKinney, James D.

1975-01-01

Four second-grade teachers completed the Classroom Behavior Inventory for every student in their class (N=101). Subjects were classified as either reflective (N=32) or impulsive (N=32) by using the Matching Familiar Figures Test (MFF). (Author)

Electromagnetic propulsion for spacecraft

NASA Technical Reports Server (NTRS)

Myers, Roger M.

1993-01-01

Three electromagnetic propulsion technologies, solid propellant pulsed plasma thrusters (PPT), magnetoplasmadynamic (MPD) thrusters, and pulsed inductive thrusters (PIT) have been developed for application to auxiliary and primary spacecraft propulsion. Both the PPT and MPD thrusters have been flown in space, though only PPTs have been used on operational satellites. The performance of operational PPTs is quite poor, providing only about 8 percent efficiency at about 1000 sec specific impulse. Laboratory PPTs yielding 34 percent efficiency at 5170 sec specific impulse have been demonstrated. Laboratory MPD thrusters have been demonstrated with up to 70 percent efficiency and 7000 sec specific impulse. Recent PIT performance measurements using ammonia and hydrazine propellants are extremely encouraging, reaching 50 percent efficiency for specific impulses between 4000 and 8000 sec.

General existence principles for Stieltjes differential equations with applications to mathematical biology

NASA Astrophysics Data System (ADS)

López Pouso, Rodrigo; Márquez Albés, Ignacio

2018-04-01

Stieltjes differential equations, which contain equations with impulses and equations on time scales as particular cases, simply consist on replacing usual derivatives by derivatives with respect to a nondecreasing function. In this paper we prove new existence results for functional and discontinuous Stieltjes differential equations and we show that such general results have real world applications. Specifically, we show that Stieltjes differential equations are specially suitable to study populations which exhibit dormant states and/or very short (impulsive) periods of reproduction. In particular, we construct two mathematical models for the evolution of a silkworm population. Our first model can be explicitly solved, as it consists on a linear Stieltjes equation. Our second model, more realistic, is nonlinear, discontinuous and functional, and we deduce the existence of solutions by means of a result proven in this paper.

Domain-Specific Impulsivity in School-Age Children

PubMed Central

Tsukayama, Eli; Duckworth, Angela Lee; Kim, Betty

2013-01-01

Impulsivity is a salient individual difference in children with well-established predictive validity for life outcomes. The current investigation proposes that impulsive behaviors vary systematically by domain. In a series of studies with ethnically and socioeconomically diverse samples of middle school students, we find that schoolwork-related and interpersonal-related impulsivity, as observed by teachers, parents, and the students themselves, are distinct, moderately correlated behavioral tendencies. Each demonstrates differentiated relationships with dimensions of childhood temperament, Big Five personality factors, and outcomes, such as sociometric popularity, report card grades, and classroom conduct. Implications for theoretical conceptions of impulsivity as well as for practical applications (e.g., domain-specific interventions) are discussed. PMID:24118714

Accuracy Improvement in Magnetic Field Modeling for an Axisymmetric Electromagnet

NASA Technical Reports Server (NTRS)

Ilin, Andrew V.; Chang-Diaz, Franklin R.; Gurieva, Yana L.; Il,in, Valery P.

2000-01-01

This paper examines the accuracy and calculation speed for the magnetic field computation in an axisymmetric electromagnet. Different numerical techniques, based on an adaptive nonuniform grid, high order finite difference approximations, and semi-analitical calculation of boundary conditions are considered. These techniques are being applied to the modeling of the Variable Specific Impulse Magnetoplasma Rocket. For high-accuracy calculations, a fourth-order scheme offers dramatic advantages over a second order scheme. For complex physical configurations of interest in plasma propulsion, a second-order scheme with nonuniform mesh gives the best results. Also, the relative advantages of various methods are described when the speed of computation is an important consideration.

Performance Increase Verification for a Bipropellant Rocket Engine

NASA Technical Reports Server (NTRS)

Alexander, Leslie; Chapman, Jack; Wilson, Reed; Krismer, David; Lu, Frank; Wilson, Kim; Miller, Scott; England, Chris

2008-01-01

Component performance assessment testing for a, pressure-fed earth storable bipropellant rocket engine was successfully completed at Aerojet's Redmond test facility. The primary goal of the this development project is to increase the specific impulse of an apogee class bi-propellant engine to greater than 330 seconds with nitrogen tetroxide and monomethylhydrazine propellants and greater than 335 seconds with nitrogen tetroxide and hydrazine. The secondary goal of the project is to take greater advantage of the high temperature capabilities of iridium/rhenium chambers. In order to achieve these goals, the propellant feed pressures were increased to 400 psia, nominal, which in turn increased the chamber pressure and temperature, allowing for higher c*. The tests article used a 24-on-24 unlike doublet injector design coupled with a copper heat sink chamber to simulate a flight configuration combustion chamber. The injector is designed to produce a nominal 200 lbf of thrust with a specific impulse of 335 seconds (using hydrazine fuel). Effect of Chamber length on engine C* performance was evaluated with the use of modular, bolt-together test hardware and removable chamber inserts. Multiple short duration firings were performed to characterize injector performance across a range of thrust levels, 180 to 220 lbf, and mixture ratios, from 1.1 to 1.3. During firing, ignition transient, chamber pressure, and various temperatures were measured in order to evaluate the performance of the engine and characterize the thermal conditions. The tests successfully demonstrated the stable operation and performance potential of a full scale engine with a measured c* of XXXX ft/sec (XXXX m/s) under nominal operational conditions.

Aircraft Icing Handbook. Volume 2

DTIC Science & Technology

1991-03-01

an airfoil surface. icenhobig - A surface property exhibiting a reduced adhesion to ice; literally, "ice-hating." light icing - The rate of...power, and are a light weight system of reasonable cost. K. ill I-I1 1.I.2 Pneumatic Impulse Ice Protection A Pneumatic Impulse Ice Protection System...should be about 5 to 6 seconds. During moderate icing a 60 second cycle is suggested, while for light icing, longer accretion times of 3 to 4 minutes

Development and characterization of high-efficiency, high-specific impulse xenon Hall thrusters

NASA Astrophysics Data System (ADS)

Hofer, Richard Robert

This dissertation presents research aimed at extending the efficient operation of 1600 s specific impulse Hall thruster technology to the 2000--3000 s range. While recent studies of commercially developed Hall thrusters demonstrated greater than 4000 s specific impulse, maximum efficiency occurred at less than 3000 s. It was hypothesized that the efficiency maximum resulted as a consequence of modern magnetic field designs, optimized for 1600 s, which were unsuitable at high-specific impulse. Motivated by the industry efforts and mission studies, the aim of this research was to develop and characterize xenon Hall thrusters capable of both high-specific impulse and high-efficiency operation. The research divided into development and characterization phases. During the development phase, the laboratory-model NASA-173M Hall thrusters were designed with plasma lens magnetic field topographies and their performance and plasma characteristics were evaluated. Experiments with the NASA-173M version 1 (v1) validated the plasma lens design by showing how changing the magnetic field topography at high-specific impulse improved efficiency. Experiments with the NASA-173M version 2 (v2) showed there was a minimum current density and optimum magnetic field topography at which efficiency monotonically increased with voltage. Between 300--1000 V, total specific impulse and total efficiency of the NASA-173Mv2 operating at 10 mg/s ranged from 1600--3400 s and 51--61%, respectively. Comparison of the thrusters showed that efficiency can be optimized for specific impulse by varying the plasma lens design. During the characterization phase, additional plasma properties of the NASA-173Mv2 were measured and a performance model was derived accounting for a multiply-charged, partially-ionized plasma. Results from the model based on experimental data showed how efficient operation at high-specific impulse was enabled through regulation of the electron current with the magnetic field. The decrease of efficiency due to multiply-charged ions was minor. Efficiency was largely determined by the current utilization, which suggested maximum Hall thruster efficiency has yet to be reached. The electron Hall parameter was approximately constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400--900 V, which confirmed efficient operation can be realized only over a limited range of Hall parameters.

Impulsivity, Impulsive and Reflective Processes and the Development of Alcohol Use and Misuse in Adolescents and Young Adults

PubMed Central

Wiers, Reinout W.; Ames, Susan L.; Hofmann, Wilhelm; Krank, Marvin; Stacy, Alan W.

2010-01-01

This paper contrasts dual-process and personality approaches in the prediction of addictive behaviors and related risk behaviors. In dual-process models, behavior is described as the joint outcome of qualitatively different “impulsive” (or associative) and “reflective” processes. There are important individual differences regarding both types of processes, and the relative strength of both in a specific situation is influenced by prior behavior and state variables (e.g., fatigue, alcohol use). From this perspective, a specific behavior (e.g., alcohol misuse) can be predicted by the combined indices of the behavior-related impulsive processes (e.g., associations with alcohol), and reflective processes, including the ability to refrain from a motivationally salient action. Personality approaches have reported that general traits such as impulsivity predict addictive behaviors. Here we contrast these two approaches, with supplementary analyses on four datasets. We hypothesized that trait impulsivity can predict specific risky behaviors, but that its predictive power disappears once specific behavior-related associations, indicators of executive functioning, and their interaction are entered into the equation. In all four studies the observed interaction between specific associations and executive control (EC) was robust: trait impulsivity did not diminish the prediction of alcohol use by the interaction. Trait impulsivity was not always related to alcohol use, and when it was, the predictive power disappeared after entering the interaction between behavior-specific associations and EC in one study, but not in the other. These findings are interpreted in relation to the validity of the measurements used, which leads to a more refined hypothesis. PMID:21833213

Observations of the Coronal Mass Ejection with a Complex Acceleration Profile

NASA Astrophysics Data System (ADS)

Reva, A. A.; Kirichenko, A. S.; Ulyanov, A. S.; Kuzin, S. V.

2017-12-01

We study the coronal mass ejection (CME) with a complex acceleration profile. The event occurred on 2009 April 23. It had an impulsive acceleration phase, an impulsive deceleration phase, and a second impulsive acceleration phase. During its evolution, the CME showed signatures of different acceleration mechanisms: kink instability, prominence drainage, flare reconnection, and a CME–CME collision. The special feature of the observations is the usage of the TESIS EUV telescope. The instrument could image the solar corona in the Fe 171 Å line up to a distance of 2 {R}ȯ from the center of the Sun. This allows us to trace the CME up to the LASCO/C2 field of view without losing the CME from sight. The onset of the CME was caused by kink instability. The mass drainage occurred after the kink instability. The mass drainage played only an auxiliary role: it decreased the CME mass, which helped to accelerate the CME. The first impulsive acceleration phase was caused by the flare reconnection. We observed the two-ribbon flare and an increase of the soft X-ray flux during the first impulsive acceleration phase. The impulsive deceleration and the second impulsive acceleration phases were caused by the CME–CME collision. The studied event shows that CMEs are complex phenomena that cannot be explained with only one acceleration mechanism. We should seek a combination of different mechanisms that accelerate CMEs at different stages of their evolution.

Energy Partitioning and Impulse Dispersion in the Decorated, Tapered, Strongly Nonlinear Granular Alignment: A System with Many Potential Applications

DTIC Science & Technology

2010-03-01

finally discuss some preliminary experimental results using systems with chrome spheres and small Nitinol interstitial grains to present the... Nitinol interstitial grains to present the underlying nonlinear dynamics of this so-called decorated tapered granular alignment. We are specifically...second was the DTC setup. In this case, small Nitinol 2.38 mm diameter particles were in- troduced between the main STC particles so that NDTC=9. 53 The

Characterization of long-range functional connectivity in epileptic networks by neuronal spike-triggered local field potentials

NASA Astrophysics Data System (ADS)

Lopour, Beth A.; Staba, Richard J.; Stern, John M.; Fried, Itzhak; Ringach, Dario L.

2016-04-01

Objective. Quantifying the relationship between microelectrode-recorded multi-unit activity (MUA) and local field potentials (LFPs) in distinct brain regions can provide detailed information on the extent of functional connectivity in spatially widespread networks. These methods are common in studies of cognition using non-human animal models, but are rare in humans. Here we applied a neuronal spike-triggered impulse response to electrophysiological recordings from the human epileptic brain for the first time, and we evaluate functional connectivity in relation to brain areas supporting the generation of seizures. Approach. Broadband interictal electrophysiological data were recorded from microwires adapted to clinical depth electrodes that were implanted bilaterally using stereotactic techniques in six presurgical patients with medically refractory epilepsy. MUA and LFPs were isolated in each microwire, and we calculated the impulse response between the MUA on one microwire and the LFPs on a second microwire for all possible MUA/LFP pairs. Results were compared to clinical seizure localization, including sites of seizure onset and interictal epileptiform discharges. Main results. We detected significant interictal long-range functional connections in each subject, in some cases across hemispheres. Results were consistent between two independent datasets, and the timing and location of significant impulse responses reflected anatomical connectivity. However, within individual subjects, the spatial distribution of impulse responses was unique. In two subjects with clear seizure localization and successful surgery, the epileptogenic zone was associated with significant impulse responses. Significance. The results suggest that the spike-triggered impulse response can provide valuable information about the neuronal networks that contribute to seizures using only interictal data. This technique will enable testing of specific hypotheses regarding functional connectivity in epilepsy and the relationship between functional properties and imaging findings. Beyond epilepsy, we expect that the impulse response could be more broadly applied as a measure of long-range functional connectivity in studies of cognition.

Characterization of long-range functional connectivity in epileptic networks by neuronal spike-triggered local field potentials

PubMed Central

Lopour, Beth A; Staba, Richard J; Stern, John M; Fried, Itzhak; Ringach, Dario L

2017-01-01

Objective Quantifying the relationship between microelectrode-recorded multi-unit activity (MUA) and local field potentials (LFPs) in distinct brain regions can provide detailed information on the extent of functional connectivity in spatially widespread networks. These methods are common in studies of cognition using non-human animal models, but are rare in humans. Here we applied a neuronal spike-triggered impulse response to electrophysiological recordings from the human epileptic brain for the first time, and we evaluate functional connectivity in relation to brain areas supporting the generation of seizures. Approach Broadband interictal electrophysiological data were recorded from microwires adapted to clinical depth electrodes that were implanted bilaterally using stereotactic techniques in six presurgical patients with medically refractory epilepsy. MUA and LFPs were isolated in each microwire, and we calculated the impulse response between the MUA on one microwire and the LFPs on a second microwire for all possible MUA/LFP pairs. Results were compared to clinical seizure localization, including sites of seizure onset and interictal epileptiform discharges. Main results We detected significant interictal long-range functional connections in each subject, in some cases across hemispheres. Results were consistent between two independent datasets, and the timing and location of significant impulse responses reflected anatomical connectivity. However, within individual subjects, the spatial distribution of impulse responses was unique. In two subjects with clear seizure localization and successful surgery, the epileptogenic zone was associated with significant impulse responses. Significance The results suggest that the spike-triggered impulse response can provide valuable information about the neuronal networks that contribute to seizures using only interictal data. This technique will enable testing of specific hypotheses regarding functional connectivity in epilepsy and the relationship between functional properties and imaging findings. Beyond epilepsy, we expect that the impulse response could be more broadly applied as a measure of long-range functional connectivity in studies of cognition. PMID:26975603

"Impulsive" suicide attempts: What do we really mean?

PubMed

May, Alexis M; Klonsky, E David

2016-07-01

Suicide attempts are often regarded as impulsive acts. However, there is little consensus regarding the definition or clinical characteristics of an "impulsive" attempt. To clarify this issue, we examined 3 indicators of the impulsivity of an attempt: (a) preparation, (b) time contemplating the attempt, and (c) self-report that impulsivity motivated the attempt. We examined relationships among the indicators and their relationship to trait impulsivity and characteristics of the suicide attempt. Adult participants (N = 205) with a history of suicide attempts were administered validated interviews and questionnaires. In general, the 3 attempt impulsivity indicators correlated only moderately with each other and not at all with trait impulsivity or with important characteristics of the attempt (e.g., lethality, preattempt communication, motivations). However, there were 2 exceptions. First, intent to die was inversely related to the 3 attempt impulsivity indicators (rs ranged from -.17 to .45) such that more impulsive attempts were associated with lower intent. Second, self-report that the attempt was motivated by impulsivity was related to 3 facets of trait impulsivity (rs ranged from .16 to .41). These findings suggest that individuals endorsing trait impulsivity are likely to describe their attempts as motivated by impulsivity, regardless of the presence of preparation or prolonged contemplation. Overall, study results suggest that the common conception of a unidimensional impulsive attempt may be inaccurate and that the emphasis on general impulsivity in prevention guidelines should be tempered. Implications for suicide risk assessment and prevention are discussed. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Dysfunctional, but not functional, impulsivity is associated with a history of seriously violent behaviour and reduced orbitofrontal and hippocampal volumes in schizophrenia.

PubMed

Kumari, Veena; Barkataki, Ian; Goswami, Sangeeta; Flora, Satinder; Das, Mrigendra; Taylor, Pamela

2009-07-15

Aggression and violent acts have been linked with impulsive responding. We investigated whether impulsive personality trait, especially suggestive of dysfunctional impulsivity (i.e. fast and inaccurate responding where this is non-optimal), is associated with a history of seriously violent behaviour and specific brain deficits in schizophrenia. Twenty-four male participants with schizophrenia, of whom 10 had a history of serious physical violence, and 14 healthy male participants were assessed on impulsiveness (dysfunctional impulsivity), venturesomeness (functional impulsivity), and empathy. All participants underwent magnetic resonance imaging. The results revealed that participants with schizophrenia and a history of violence showed elevated impulsiveness but had comparable scores on venturesomeness and empathy dimensions. Impulsiveness scores correlated negatively with reduced orbitofrontal grey matter volume in both the patient and healthy control groups, and with hippocampal volume in the patient group. Our findings suggest that dysfunctional, but not functional, impulsivity is elevated in patients with schizophrenia with a propensity for repetitive violence, and this in turn appears to be associated with reduce volumes of both the orbitofrontal cortex grey matter and the hippocampus. Violence risk prediction and management strategies in schizophrenia may benefit from including specific measures of dysfunctional impulsive traits.

Project NEO Specific Impulse Testing Solutions

NASA Technical Reports Server (NTRS)

Baffa, Bill

2018-01-01

The Neo test stand is currently configured to fire a horizontally mounted rocket motor with up to 6500 lbf thrust. Currently, the Neo test stand can measure flow of liquid propellant and oxidizer, pressures residing in the closed system up to the combustion chamber. The current configuration does not have the ability to provide all data needed to compute specific impulse. This presents three methods to outfit the NEO test fixture with instrumentation allowing for calculation of specific impulse.

Second-to-fourth digit ratio and impulsivity: a comparison between offenders and nonoffenders.

PubMed

Hanoch, Yaniv; Gummerum, Michaela; Rolison, Jonathan

2012-01-01

Personality characteristics, particularly impulsive tendencies, have long been conceived as the primary culprit in delinquent behavior. One crucial question to emerge from this line of work is whether impulsivity has a biological basis. To test this possibility, 44 male offenders and 46 nonoffenders completed the Eysenck Impulsivity Questionnaire, and had their 2D∶4D ratio measured. Offenders exhibited smaller right hand digit ratio measurements compared to non-offenders, but higher impulsivity scores. Both impulsivity and 2D∶4D ratio measurements significantly predicted criminality (offenders vs. nonoffenders). Controlling for education level, the 2D∶4D ratio measurements had remained a significant predictor of criminality, while impulsivity scores no longer predicted criminality significantly. Our data, thus, indicates that impulsivity but not 2D∶4D ratio measurements relate to educational attainment. As offenders varied in their number of previous convictions and the nature of their individual crimes, we also tested for differences in 2D∶4D ratio and impulsivity among offenders. Number of previous convictions did not correlate significantly with the 2D∶4D ratio measurements or impulsivity scores. Our study established a link between a biological marker and impulsivity among offenders (and lack thereof among non-offenders), which emphasise the importance of studying the relationship between biological markers, impulsivity and criminal behavior.

Muscle-Specific Effective Mechanical Advantage and Joint Impulse in Weightlifting.

PubMed

Kipp, Kristof; Harris, Chad

2017-07-01

Kipp, K, and Harris, C. Muscle-specific effective mechanical advantage and joint impulse in weightlifting. J Strength Cond Res 31(7): 1905-1910, 2017-Lifting greater loads during weightlifting exercises may theoretically be achieved through increasing the magnitudes of net joint impulses or manipulating the joints' effective mechanical advantage (EMA). The purpose of this study was to investigate muscle-specific EMA and joint impulse as well as impulse-momentum characteristics of the lifter-barbell system across a range of external loads during the execution of the clean. Collegiate-level weightlifters performed submaximal cleans at 65, 75, and 85% of their 1-repetition maximum (1-RM), whereas data from a motion analysis system and a force plate were used to calculate lifter-barbell system impulse and velocity, as well as net extensor impulse generated at the hip, knee, and ankle joints and the EMA of the gluteus maximus, hamstrings, quadriceps, and triceps surae muscles. The results indicated that the lifter-barbell system impulse did not change as load increased, whereas the velocity of the lifter-barbell system decreased with greater load. In addition, the net extensor impulse at all joints increased as load increased. The EMA of all muscles did not, however, change as load increased. The load-dependent effects on the impulse-velocity characteristics of the lifter-barbell system may reflect musculoskeletal force-velocity behaviors, and may further indicate that the weightlifting performance is limited by the magnitude of ground reaction force impulse. In turn, the load-dependent effects observed at the joint level indicated that lifting greater loads were due to greater net extensor impulses generated at the joints of the lower extremity and not greater EMAs of the respective extensor muscles. In combination, these results suggest that lifting greater external loads during the clean is due to the ability to generate large extensor joint impulses, rather than manipulate EMA.

High/variable mixture ratio O2/H2 engine

NASA Technical Reports Server (NTRS)

Adams, A.; Parsley, R. C.

1988-01-01

Vehicle/engine analysis studies have identified the High/Dual Mixture Ratio O2/H2 Engine cycle as a leading candidate for an advanced Single Stage to Orbit (SSTO) propulsion system. This cycle is designed to allow operation at a higher than normal O/F ratio of 12 during liftoff and then transition to a more optimum O/F ratio of 6 at altitude. While operation at high mixture ratios lowers specific impulse, the resultant high propellant bulk density and high power density combine to minimize the influence of atmospheric drag and low altitude gravitational forces. Transition to a lower mixture ratio at altitude then provides improved specific impulse relative to a single mixture ratio engine that must select a mixture ratio that is balanced for both low and high altitude operation. This combination of increased altitude specific impulse and high propellant bulk density more than offsets the compromised low altitude performance and results in an overall mission benefit. Two areas of technical concern relative to the execution of this dual mixture ratio cycle concept are addressed. First, actions required to transition from high to low mixture ratio are examined, including an assessment of the main chamber environment as the main chamber mixture ratio passes through stoichiometric. Secondly, two approaches to meet a requirement for high turbine power at high mixture ratio condition are examined. One approach uses high turbine temperature to produce the power and requires cooled turbines. The other approach incorporates an oxidizer-rich preburner to increase turbine work capability via increased turbine mass flow.

Potentially traumatic events, personality, and risky sexual behavior in undergraduate college students.

PubMed

Moore, Ashlee A; Overstreet, Cassie; Kendler, Kenneth S; Dick, Danielle M; Adkins, Amy; Amstadter, Ananda B

2017-01-01

Impulsivity and extraversion have demonstrated associations with risky sexual behavior (RSB) and potentially traumatic events (PTEs). In addition, interpersonal trauma appears to be associated with RSB, but research on the relationship between RSB and noninterpersonal PTEs (e.g., accidental) is lacking. The current study aims to investigate the relationships between personality (i.e., impulsivity, extraversion), RSB and multiple types of PTEs (i.e., accidental, physical, or sexual). Personality and demographic characteristics were assessed during participants' (N = 970) first semester of college, past-12 month PTEs and RSB were assessed during the second semester of participants' junior year. Multiple linear regression was used to examine the relationship between PTEs, personality factors, and RSB. Analyses were also conducted to examine the potential mediating effect of interpersonal PTEs on the relationship between personality and RSB. Impulsivity and extraversion were significantly positively associated with RSB. Both physical and sexual PTEs, but not accidental PTEs, were also significantly positively associated with RSB. Sexual PTEs significantly mediated the relationship between impulsivity and RSB. This is the first study to date to simultaneously examine the relationship between personality, RSB, and types of PTEs in a large sample of young adults. Exposure to interpersonal trauma appears to be a salient factor in the relationship between personality, specifically impulsivity, and RSB. These results indicate that college students may benefit from education regarding the potential negative outcomes of RSB, and that individuals with a history of interpersonal PTEs may be at increased risk for sexual risk taking. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Potentially traumatic events, personality and risky sexual behavior in undergraduate college students

PubMed Central

Moore, Ashlee A.; Overstreet, Cassie; Kendler, Kenneth S.; Dick, Danielle M.; Adkins, Amy; Amstadter, Ananda B.

2016-01-01

Objective Impulsivity and extraversion have demonstrated associations with risky sexual behavior (RSB) and potentially traumatic events (PTEs). In addition, interpersonal trauma appears to be associated with RSB, but research on the relationship between RSB and non-interpersonal PTEs (e.g., accidental) is lacking. The current study aims to investigate the relationships between personality (i.e., impulsivity, extraversion), RSB and multiple types of PTEs (i.e., accidental, physical, sexual). Methods Personality and demographic characteristics were assessed during participants’ (N = 970) first semester of college, past-12 month PTEs and RSB were assessed during the second semester of participants’ junior year. Multiple linear regression was used to examine the relationship between PTEs, personality factors, and RSB. Analyses were also conducted to examine the potential mediating effect of interpersonal PTEs on the relationship between personality and RSB. Results Impulsivity and extraversion were significantly positively associated with RSB. Both physical and sexual PTEs, but not accidental PTEs, were also significantly positively associated with RSB. Sexual PTEs significantly mediated the relationship between impulsivity and RSB. Conclusions This is the first study to date to simultaneously examine the relationship between personality, RSB, and types of PTEs in a large sample of young adults. Exposure to interpersonal trauma appears to be a salient factor in the relationship between personality, specifically impulsivity, and RSB. These results indicate that college students may benefit from education regarding the potential negative outcomes of RSB, and that individuals with a history of interpersonal PTEs may be at increased risk for sexual risk taking. PMID:27348066

Stability-maneuverability trade-offs during lateral steps.

PubMed

Acasio, Julian; Wu, Mengnan/Mary; Fey, Nicholas P; Gordon, Keith E

2017-02-01

Selecting a specific foot placement strategy to perform walking maneuvers requires the management of several competing factors, including: maintaining stability, positioning oneself to actively generate impulses, and minimizing mechanical energy requirements. These requirements are unlikely to be independent. Our purpose was to determine the impact of lateral foot placement on stability, maneuverability, and energetics during walking maneuvers. Ten able-bodied adults performed laterally-directed walking maneuvers. Mediolateral placement of the "Push-off" foot during the maneuvers was varied, ranging from a cross-over step to a side-step. We hypothesized that as mediolateral foot placement became wider, passive stability in the direction of the maneuver, the lateral impulse generated to create the maneuver, and mechanical energy cost would all increase. We also hypothesized that subjects would prefer an intermediate step width reflective of trade-offs between stability vs. both maneuverability and energy. In support of our first hypothesis, we found that as Push-off step width increased, lateral margin of stability, peak lateral impulse, and total joint work all increased. In support of our second hypothesis, we found that when subjects had no restrictions on their mediolateral foot placement, they chose a foot placement between the two extreme positions. We found a significant relationship (p<0.05) between lateral margin of stability and peak lateral impulse (r=0.773), indicating a trade-off between passive stability and the force input required to maneuver. These findings suggest that during anticipated maneuvers people select foot placement strategies that balance competing costs to maintain stability, actively generate impulses, and minimize mechanical energy costs. Published by Elsevier B.V.

A path model of different forms of impulsivity with externalizing and internalizing psychopathology: Towards greater specificity.

PubMed

Johnson, Sheri L; Tharp, Jordan A; Peckham, Andrew D; Carver, Charles S; Haase, Claudia M

2017-09-01

A growing empirical literature indicates that emotion-related impulsivity (compared to impulsivity that is unrelated to emotion) is particularly relevant for understanding a broad range of psychopathologies. Recent work, however, has differentiated two forms of emotion-related impulsivity: A factor termed Pervasive Influence of Feelings captures tendencies for emotions (mostly negative emotions) to quickly shape thoughts, and a factor termed Feelings Trigger Action captures tendencies for positive and negative emotions to quickly and reflexively shape behaviour and speech. This study used path modelling to consider links from emotion-related and non-emotion-related impulsivity to a broad range of psychopathologies. Undergraduates completed self-report measures of impulsivity, depression, anxiety, aggression, and substance use symptoms. A path model (N = 261) indicated specificity of these forms of impulsivity. Pervasive Influence of Feelings was related to anxiety and depression, whereas Feelings Trigger Action and non-emotion-related impulsivity were related to aggression and substance use. The findings of this study suggest that emotion-relevant impulsivity could be a potentially important treatment target for a set of psychopathologies. Recent work has differentiated two forms of emotion-related impulsivity. This study tests a multivariate path model linking emotion-related and non-emotion-related impulsivity with multiple forms of psychopathology. Impulsive thoughts in response to negative emotions were related to anxiety and depression. Impulsive actions in response to emotions were related to aggression and substance use, as did non-emotion-related impulsivity. The study was limited by the reliance on self-report measures of impulsivity and psychopathology. There is a need for longitudinal work on how these forms of impulsivity predict the onset and course of psychopathology. © 2017 The British Psychological Society.

Genetic association of impulsivity in young adults: a multivariate study

PubMed Central

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

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

Hypersonic ignition and thrust production in a scramjet

NASA Technical Reports Server (NTRS)

Paull, A.

1993-01-01

Experimental results are given for the specific impulse produced by a two-dimensional scramjet at flight speeds ranging between 2.5 and 5.5 km/s with a combustion chamber Mach number of 4.5. Both hydrogen and ethane fuels were used. Results show that provided sufficiently high pressures and sufficiently long combustion chambers are used specific impulses in excess of 1500 s can be obtained with hydrogen. Ethane produced specific impulses less than 600 s with the same conditions and model configuration.

Overweight in adolescent, psychiatric inpatients: A problem of general or food-specific impulsivity?

PubMed

Deux, Natalie; Schlarb, Angelika A; Martin, Franziska; Holtmann, Martin; Hebebrand, Johannes; Legenbauer, Tanja

2017-05-01

Adolescent psychiatric patients are vulnerable to weight problems and show an overrepresentation of overweight compared to the healthy population. One potential factor that can contribute to the etiology of overweight is higher impulsivity. As of yet, it is unclear whether it is a general impulse control deficit or weight-related aspects such as lower impulse control in response to food that have an impact on body weight. As this may have therapeutic implications, the current study investigated differences between overweight and non-overweight adolescent psychiatric inpatients (N = 98; aged 12-20) in relation to trait impulsivity and behavioral inhibition performance. The Barratt Impulsiveness Scale and two go/no-go paradigms with neutral and food-related stimulus materials were applied. Results indicated no significant differences concerning trait impulsivity, but revealed that overweight inpatients had significantly more difficulties in inhibition performance (i.e. they reacted more impulsively) in response to both food and neutral stimuli compared to non-overweight inpatients. Furthermore, no specific inhibition deficit for high-caloric vs. low-caloric food cues emerged in overweight inpatients, whereas non-overweight participants showed significantly lower inhibition skills in response to high-caloric than low-caloric food stimuli. The results highlight a rather general, non-food-specific reduced inhibition performance in an overweight adolescent psychiatric population. Further research is necessary to enhance the understanding of the role of impulsivity in terms of body weight status in this high-risk group of adolescent inpatients. Copyright © 2017 Elsevier Ltd. All rights reserved.

Gender-specific mediational links between parenting styles, parental monitoring, impulsiveness, drinking control, and alcohol-related problems.

PubMed

Patock-Peckham, Julie A; King, Kevin M; Morgan-Lopez, Antonio A; Ulloa, Emilio C; Moses, Jennifer M Filson

2011-03-01

Recently, it has been suggested that traits may dynamically change as conditions change. One possible mechanism that may influence impulsiveness is parental monitoring. Parental monitoring reflects a knowledge regarding one's offspring's whereabouts and social connections. The aim of this investigation was to examine potential gender-specific parental influences to impulsiveness (general behavioral control), control over one's own drinking (specific behavioral control), and alcohol-related problems among individuals in a period of emerging adulthood. Direct and mediational links between parenting styles (permissive, authoritarian, and authoritative), parental monitoring, impulsiveness, drinking control, and alcohol-related problems were investigated. A multiple-group, SEM model with (316 women, 265 men) university students was examined. In general, the overall pattern among male and female respondents was distinct. For daughters, perceptions of a permissive father were indirectly linked to more alcohol-related problems through lower levels of monitoring by fathers and more impulsive symptoms. Perceptions of an authoritative father were also indirectly linked to fewer impulsive symptoms through higher levels of monitoring by fathers among daughters. For men, perceptions of a permissive mother were indirectly linked to more alcohol-related problems through lower levels of monitoring by mothers and more impulsive symptoms. For sons, perceptions of mother authoritativeness were indirectly linked to fewer alcohol-related problems through more monitoring by mothers and fewer impulsive symptoms. Monitoring by an opposite-gender parent mediated the link between parenting styles (i.e., permissive, authoritative) on impulsiveness.

Interactive effects of cumulative stress and impulsivity on alcohol consumption.

PubMed

Fox, Helen C; Bergquist, Keri L; Peihua, Gu; Rajita, Sinha

2010-08-01

Alcohol addiction may reflect adaptations to stress, reward, and regulatory brain systems. While extensive research has identified both stress and impulsivity as independent risk factors for drinking, few studies have assessed the interactive relationship between stress and impulsivity in terms of hazardous drinking within a community sample of regular drinkers. One hundred and thirty regular drinkers (56M/74F) from the local community were assessed for hazardous and harmful patterns of alcohol consumption using the Alcohol Use Disorders Identification Test (AUDIT). All participants were also administered the Barratt Impulsiveness Scale (BIS-11) as a measure of trait impulsivity and the Cumulative Stress/Adversity Checklist (CSC) as a comprehensive measure of cumulative adverse life events. Standard multiple regression models were used to ascertain the independent and interactive nature of both overall stress and impulsivity as well as specific types of stress and impulsivity on hazardous and harmful drinking. Recent life stress, cumulative traumatic stress, overall impulsivity, and nonplanning-related impulsivity as well as cognitive and motor-related impulsivity were all independently predictive of AUDIT scores. However, the interaction between cumulative stress and total impulsivity scores accounted for a significant amount of the variance, indicating that a high to moderate number of adverse events and a high trait impulsivity rating interacted to affect greater AUDIT scores. The subscale of cumulative life trauma accounted for the most variance in AUDIT scores among the stress and impulsivity subscales. Findings highlight the interactive relationship between stress and impulsivity with regard to hazardous drinking. The specific importance of cumulative traumatic stress as a marker for problem drinking is also discussed.

Low-Mass, Low-Power Hall Thruster System

NASA Technical Reports Server (NTRS)

Pote, Bruce

2015-01-01

NASA is developing an electric propulsion system capable of producing 20 mN thrust with input power up to 1,000 W and specific impulse ranging from 1,600 to 3,500 seconds. The key technical challenge is the target mass of 1 kg for the thruster and 2 kg for the power processing unit (PPU). In Phase I, Busek Company, Inc., developed an overall subsystem design for the thruster/cathode, PPU, and xenon feed system. This project demonstrated the feasibility of a low-mass power processing architecture that replaces four of the DC-DC converters of a typical PPU with a single multifunctional converter and a low-mass Hall thruster design employing permanent magnets. In Phase II, the team developed an engineering prototype model of its low-mass BHT-600 Hall thruster system, with the primary focus on the low-mass PPU and thruster. The goal was to develop an electric propulsion thruster with the appropriate specific impulse and propellant throughput to enable radioisotope electric propulsion (REP). This is important because REP offers the benefits of nuclear electric propulsion without the need for an excessively large spacecraft and power system.

Identifying the facets of impulsivity that explain the relation between ADHD symptoms and substance use in a nonclinical sample

PubMed Central

Roberts, Walter; Peters, Jessica R.; Adams, Zachary W.; Lynam, Donald R.; Milich, Richard

2014-01-01

Adults with attention-deficit/hyperactivity disorder (ADHD) are at higher risk to use substances than their nonclinical peers. Increased levels of impulsivity are generally thought to contribute to their increased levels of risk. Impulsivity is a multifaceted construct, however, and little research to date has attempted to identify which facets of impulsivity contribute to the increased rates of substance abuse among individuals with ADHD. The current study examined the relation among ADHD symptom clusters (i.e., hyperactivity/impulsivity and inattention), substance use rates (i.e., alcohol use, nicotine use, and marijuana use), and personality processes associated with impulsive behavior in a group of young adults. Participants were 361 undergraduate students. Both symptom clusters were positively associated with rates of substance use. Specifically, hyperactive/impulsive symptoms were associated with alcohol and nicotine use, and inattentive symptoms were associated with alcohol use. Several pathways from hyperactive/impulsive symptoms to alcohol, nicotine, and marijuana use via specific facets of impulsivity were identified. These findings have implications for understanding the relation between ADHD symptoms and substance use, as well as clinical implications for preventing and treating substance use problems in individuals with symptoms of ADHD. PMID:24813555

Deflection corridors of abdomen and thorax in oblique side impacts using equal stress equal velocity approach: comparison with other normalization methods.

PubMed

Yoganandan, Narayan; Arun, Mike W J; Humm, John; Pintar, Frank A

2014-10-01

The first objective of the study was to determine the thorax and abdomen deflection time corridors using the equal stress equal velocity approach from oblique side impact sled tests with postmortem human surrogates fitted with chestbands. The second purpose of the study was to generate deflection time corridors using impulse momentum methods and determine which of these methods best suits the data. An anthropometry-specific load wall was used. Individual surrogate responses were normalized to standard midsize male anthropometry. Corridors from the equal stress equal velocity approach were very similar to those from impulse momentum methods, thus either method can be used for this data. Present mean and plus/minus one standard deviation abdomen and thorax deflection time corridors can be used to evaluate dummies and validate complex human body finite element models.

Development of the Executive Personal Finance Scale.

PubMed

Spinella, Marcello; Yang, Bijou; Lester, David

2007-03-01

There is accumulating evidence that prefrontal systems play an important role in management of personal finances, based on studies using clinical populations, functional neuroimaging, and both subjective and objective neuropsychological measures. This study developed the Executive Personal Finance Scale (EPFS) as a specific self-rating measure of executive aspects of personal money management. The resulting 20-item scale had good reliability and showed four factors: impulse control, organization, planning, and motivational drive. Validity was evidenced by correlations with income, credit card debt, and investments. The EPFS also showed logical correlations with compulsive buying and money attitudes. Second-order factor analysis of the EPFS and other scales revealed two higher-order factors of personal finance: cognitive (e.g., planning, organizing) and emotional (e.g., anxiety, impulse-spending, prestige). The EPFS shows good psychometric properties, is easy to use, and will make a convenient complement to other research methodologies exploring the neural basis of personal finance management.

Mission Advantages of Constant Power, Variable Isp Electrostatic Thrusters

NASA Technical Reports Server (NTRS)

Oleson, Steven R.

2000-01-01

Electric propulsion has moved from station-keeping capability for spacecraft to primary propulsion with the advent of both the Deep Space One asteroid flyby and geosynchronous spacecraft orbit insertion. In both cases notably more payload was delivered than would have been possible with chemical propulsion. To provide even greater improvements electrostatic thruster performance could be varied in specific impulse, but kept at constant power to provide better payload or trip time performance for different mission phases. Such variable specific impulse mission applications include geosynchronous and low earth orbit spacecraft stationkeeping and orbit insertion, geosynchronous reusable tug missions, and interplanetary probes. The application of variable specific impulse devices is shown to add from 5 to 15% payload for these missions. The challenges to building such devices include variable voltage power supplies and extending fuel throughput capabilities across the specific impulse range.

Low voltage 30cm ion thruster

NASA Technical Reports Server (NTRS)

1972-01-01

The construction of an ion thruster module (including thruster, power conditioning, and control system) capable of operating for 10,000 hours over a five to one range at an effective specific impulse of approximately 2800 seconds is discussed. The several interrelated tasks involved in the construction of the engine are described. Performance tests of the engine and the effects of various modifications are reported. It was demonstrated that thruster performance and stability were not materially affected by reasonable changes from the nominal operating point.

Reactor moderator, pressure vessel, and heat rejection system of an open-cycle gas core nuclear rocket concept

NASA Technical Reports Server (NTRS)

Taylor, M. F.; Whitmarsh, C. L., Jr.; Sirocky, P. J., Jr.; Iwanczyke, L. C.

1973-01-01

A preliminary design study of a conceptual 6000-megawatt open-cycle gas-core nuclear rocket engine system was made. The engine has a thrust of 196,600 newtons (44,200 lb) and a specific impulse of 4400 seconds. The nuclear fuel is uranium-235 and the propellant is hydrogen. Critical fuel mass was calculated for several reactor configurations. Major components of the reactor (reflector, pressure vessel, and waste heat rejection system) were considered conceptually and were sized.

A combined approach for weak fault signature extraction of rolling element bearing using Hilbert envelop and zero frequency resonator

NASA Astrophysics Data System (ADS)

Kumar, Keshav; Shukla, Sumitra; Singh, Sachin Kumar

2018-04-01

Periodic impulses arise due to localised defects in rolling element bearing. At the early stage of defects, the weak impulses are immersed in strong machinery vibration. This paper proposes a combined approach based upon Hilbert envelop and zero frequency resonator for the detection of the weak periodic impulses. In the first step, the strength of impulses is increased by taking normalised Hilbert envelop of the signal. It also helps in better localization of these impulses on time axis. In the second step, Hilbert envelope of the signal is passed through the zero frequency resonator for the exact localization of the periodic impulses. Spectrum of the resonator output gives peak at the fault frequency. Simulated noisy signal with periodic impulses is used to explain the working of the algorithm. The proposed technique is verified with experimental data also. A comparison of the proposed method with Hilbert-Haung transform (HHT) based method is presented to establish the effectiveness of the proposed method.

Time discounting and time preference in animals: A critical review.

PubMed

Hayden, Benjamin Y

2016-02-01

Animals are an important model for studies of impulsivity and self-control. Many studies have made use of the intertemporal choice task, which pits small rewards available sooner against larger rewards available later (typically several seconds), repeated over many trials. Preference for the sooner reward is often taken to indicate impulsivity and/or a failure of self-control. This review shows that very little evidence supports this assumption; on the contrary, ostensible discounting behavior may reflect a boundedly rational but not necessarily impulsive reward-maximizing strategy. Specifically, animals may discount weakly, or even adopt a long-term rate-maximizing strategy, but fail to fully incorporate postreward delays into their choices. This failure may reflect learning biases. Consequently, tasks that measure animal discounting may greatly overestimate the true discounting and may be confounded by processes unrelated to time preferences. If so, animals may be much more patient than is widely believed; human and animal intertemporal choices may reflect unrelated mental operations; and the shared hyperbolic shape of the human and animal discount curves, which is used to justify cross-species comparisons, may be coincidental. The discussion concludes with a consideration of alternative ways to measure self-control in animals.

Diffusive vs. impulsive energetic electron transport during radiation belt storms

NASA Astrophysics Data System (ADS)

Vassiliadis, D.; Koepke, M.; Tornquist, M.

2008-12-01

Earth's electron radiation belts are continually replenished by inward particle transport (as well as other, local acceleration processes) taking place during radiation belt storms. For some storms the radial transport is primarily diffusive while for others it is impulsive, or characterized by injections. To distinguish between these types of inward transport, we first use a dynamic model of the phase-space density as measured by POLAR/HIST and expressed in terms of adiabatic invariants [Green and Kivelson, 2004]. In a review of storms from 1997 to 2004 the coefficients of the model are peaked at characteristic temporal and phase- space (mu, k, L*) scales during specific storms. The transport is quantified in terms of those invariants which are violated and identified with peaks of the electron distribution in invariant space. Second, we run guiding- center simulations in wave fields fitted to in situ measurements complemented at low and high L by ground ULF pulsations. The modes of response identified in earlier studies from SAMPEX and POLAR electron flux measurements are now associated with primarily diffusive transport in the central range of the outer belt, L=4-8, and primarily impulsive transport near the plasmapause boundary, L=3-4.

ADAPTATION OF A TECHNIQUE FOR PREDICTING LARGE SOLID ROCKET MOTOR SPECIFIC IMPULSE FROM DATA OBTAINED IN MICROMOTORS.

DTIC Science & Technology

Laboratory. The purpose of this technique is to predict specific impulse in large solid rocket motors based on data obtained in micromotors . As little as 2...concerning performance of a propellant in a large solid motor. Predictions, based on data obtained in micromotors , were within 0.6% of the delivered impulse in 6-pound motors and 70-pound BATES motors. (Author)

Heat generated by Er:YAG laser in the pulp chamber of teeth submitted to removal of dental tissue and composite resin

NASA Astrophysics Data System (ADS)

Zanin, Fatima; Brugnera, Aldo, Jr.; Pecora, Jesus D.; Pinheiro, Antonio; Spano, Julio; Barbin, Eduardo; Marchesan, Melissa A.

2004-05-01

The knowledge about and control of thermal energy produced by Er:YAG laser after irradiating hard dental tissues and compound resin is important because the pulp, like all vital biological tissue, has a certain capacity for supporting stimulus. The objective of this study was to analyze the thermal variation generated by Er:YAG laser (λ=2.94μm) during the preparation of a Class I cavity in the dental structure and in the removal of microhybrid Z100 (3M) compound resin. An evaluation was made of 30 maxillary human pre-molar teeth from the bank of the Endodontic Laboratory Center of Ribeirao Preto Dental School, Brasil. The sample was divided into 6 groups of 5 teeth each: Group 1, preparation of Class I cavity with Er:YAG laser (350mJ, 3Hz, 343 impulses, 120J, 113 seconds); Group 2, preparation of Class I cavity with Er:YAG laser (350mJ, 4Hz, 343 impulses, 120J, 81 seconds); Group 3, preparation of Class I cavity with Er:YAG laser (350mJ, 6Hz, 343 impulses, 120J, 58 seconds); Group 4, removal of compound resin from Class I preparation with Er:YAG laser (350mJ, 3Hz, 258 impulses, 90J, 85 seconds); Group 5, removal of compound resin from Class I preparation with Er:YAG laser (350mJ, 4Hz, 258 impulses, 90J, 67 seconds); Group 6, removal of compound resin from Class I preparation with Er:YAG laser (350mJ, 6Hz, 258 impulses, 42 seconds). The laser used was KaVo Key 2 (Biberach, Germany), λ=2,94μm, P=3 Watts, pulse duration of 250μs, with air-water cooling. The increase in temperature during dental preparation and the removal of the compound resin was evaluated by means of a Tektronix DMM916 Thermocouple (Consitec, Brasil). The results showed that the application of laser for the removal of the hard dental tissues and for the removal of compound resins with the pulse frequencies 3, 4 and 6 Hz did not generate heating greater than 3.1°C and remained within the histopathological limits permitted for pulp tissue (5.5°C) and there was a significant statistical difference between the heat generated by the application of laser in the removal of the hard dental tissues and in the removal of compound resins (p<0.01). The average increase in temperature of the compound resin component was greater than the tooth.

Interactive Effects of Cumulative Stress and Impulsivity on Alcohol Consumption

PubMed Central

Fox, Helen C.; Bergquist, Keri L.; Gu, Peihua; Sinha, Rajita

2013-01-01

Background Alcohol addiction may reflect adaptations to stress, reward, and regulatory brain systems. While extensive research has identified both stress and impulsivity as independent risk factors for drinking, few studies have assessed the interactive relationship between stress and impulsivity in terms of hazardous drinking within a community sample of regular drinkers. Methods One hundred and thirty regular drinkers (56M/74F) from the local community were assessed for hazardous and harmful patterns of alcohol consumption using the Alcohol Use Disorders Identification Test (AUDIT). All participants were also administered the Barratt Impulsiveness Scale (BIS-11) as a measure of trait impulsivity and the Cumulative Stress/Adversity Checklist (CSC) as a comprehensive measure of cumulative adverse life events. Standard multiple regression models were used to ascertain the independent and interactive nature of both overall stress and impulsivity as well as specific types of stress and impulsivity on hazardous and harmful drinking. Results Recent life stress, cumulative traumatic stress, overall impulsivity, and nonplanning-related impulsivity as well as cognitive and motor-related impulsivity were all independently predictive of AUDIT scores. However, the interaction between cumulative stress and total impulsivity scores accounted for a significant amount of the variance, indicating that a high to moderate number of adverse events and a high trait impulsivity rating interacted to affect greater AUDIT scores. The subscale of cumulative life trauma accounted for the most variance in AUDIT scores among the stress and impulsivity subscales. Conclusions Findings highlight the interactive relationship between stress and impulsivity with regard to hazardous drinking. The specific importance of cumulative traumatic stress as a marker for problem drinking is also discussed. PMID:20491738

Relations of parenting style to Chinese children's effortful control, ego resilience, and maladjustment.

PubMed

Eisenberg, Nancy; Chang, Lei; Ma, Yue; Huang, Xiaorui

2009-01-01

The purpose of the study was to examine the relations of authoritative parenting and corporal punishment to Chinese first and second graders' effortful control (EC), impulsivity, ego resilience, and maladjustment, as well as mediating relations. A parent and teacher reported on children's EC, impulsivity, and ego resilience; parents reported on children's internalizing symptoms and their own parenting, and teachers and peers reported on children's externalizing symptoms. Authoritative parenting and low corporal punishment predicted high EC, and EC mediated the relation between parenting and externalizing problems. In addition, impulsivity mediated the relation of corporal punishment to externalizing problems. The relation of parenting to children's ego resilience was mediated by EC and/or impulsivity, and ego resilience mediated the relations of EC and impulsivity to internalizing problems.

Attentional impulsivity in binge eating disorder modulates response inhibition performance and frontal brain networks.

PubMed

Hege, M A; Stingl, K T; Kullmann, S; Schag, K; Giel, K E; Zipfel, S; Preissl, H

2015-02-01

A subgroup of overweight and obese people is characterized by binge eating disorder (BED). Increased impulsivity has been suggested to cause binge eating and subsequent weight gain. In the current study, neuronal correlates of increased impulsivity in binge eating disorder during behavioral response inhibition were investigated. Magnetic brain activity and behavioral responses of 37 overweight and obese individuals with and without diagnosed BED were recorded while performing a food-related visual go-nogo task. Trait impulsivity was assessed with the Barratt Impulsiveness Scale (BIS-11). Specifically, increased attentional impulsiveness (a subscale of the BIS-11) in BED was related to decreased response inhibition performance and hypoactivity in the prefrontal control network, which was activated when response inhibition was required. Furthermore, participants with BED showed a trend for a food-specific inhibition performance decline. This was possibly related to the absence of a food-specific activity increase in the prefrontal control network in BED, as observed in the control group. In addition, an increase in activity related to the actual button press during prepotent responses and alterations in visual processing were observed. Our results suggest an attentional impulsiveness-related attenuation in response inhibition performance in individuals with BED. This might have been related to increased reward responsiveness and limited resources to activate the prefrontal control network involved in response inhibition. Our results substantiate the importance of neuronal markers for investigating prevention and treatment of obesity, especially in specific subgroups at risk such as BED.

What Money Can't Buy: Different Patterns in Decision Making About Sex and Money Predict Past Sexual Coercion Perpetration.

PubMed

Carrier Emond, Fannie; Gagnon, Jean; Nolet, Kevin; Cyr, Gaëlle; Rouleau, Joanne-Lucine

2018-02-01

Self-reported impulsivity has been found to predict the perpetration of sexual coercion in both sexual offenders and male college students. Impulsivity can be conceptualized as a generalized lack of self-control (i.e., general perspective) or as a multifaceted construct that can vary from one context to the other (i.e., domain-specific perspective). Delay discounting, the tendency to prefer sooner smaller rewards over larger delayed rewards, is a measure of impulsive decision making. Recent sexual adaptations of delay discounting tasks can be used to test domain-specific assumptions. The present study used the UPPS-P impulsivity questionnaire, a standard money discounting task, and a sexual discounting task to predict past use of sexual coercion in a sample of 98 male college students. Results indicated that higher negative urgency scores, less impulsive money discounting, and more impulsive sexual discounting all predicted sexual coercion. Consistent with previous studies, sexuality was discounted more steeply than money by both perpetrators and non-perpetrators of sexual coercion, but this difference was twice as large in perpetrators compared to non-perpetrators. Our study identified three different predictors of sexual coercion in male college students: a broad tendency to act rashly under negative emotions, a specific difficulty to postpone sexual gratification, and a pattern of optimal non-sexual decision making. Results highlight the importance of using multiple measures, including sexuality-specific measures, to get a clear portrait of the links between impulsivity and sexual coercion.

Angular distributions of plasma edge velocity and integrated intensity: Update on specific impulse for Ablative Laser Propulsion

NASA Astrophysics Data System (ADS)

Lin, Jun; Pakhomov, Andrew V.

2005-04-01

This work concludes our discussion of the image processing technique developed earlier for determination of specific impulse (Isp) for Ablative Laser Propulsion (ALP). The plasma plumes are recorded with a time-resolved intensified charge-coupled device (ICCD) camera. The plasma was formed in vacuum (˜ 3×10-3 Torr) by focusing output pulses of a laser system (100-ps pulsewidth at 532 nm wavelength and ˜35 mJ energy) on surfaces of C (graphite), Al, Si, Fe, Cu, Zn, Sn, and Pb elements. Angular profiles for integrated intensity and plasma expansion velocity were determined for the tested elements. Such profiles were used further for assessment of specific impulse. Specific impulses derived from angular distributions of plasma expansion velocity and integral intensity appeared in excellent agreement with the data derived earlier from force measurements.

The effects of physical activity on impulsive choice: Influence of sensitivity to reinforcement amount and delay

PubMed Central

Strickland, Justin C.; Feinstein, Max A.; Lacy, Ryan T.; Smith, Mark A.

2016-01-01

Impulsive choice is a diagnostic feature and/or complicating factor for several psychological disorders and may be examined in the laboratory using delay-discounting procedures. Recent investigators have proposed using quantitative measures of analysis to examine the behavioral processes contributing to impulsive choice. The purpose of this study was to examine the effects of physical activity (i.e., wheel running) on impulsive choice in a single-response, discrete-trial procedure using two quantitative methods of analysis. To this end, rats were assigned to physical activity or sedentary groups and trained to respond in a delay-discounting procedure. In this procedure, one lever always produced one food pellet immediately, whereas a second lever produced three food pellets after a 0, 10, 20, 40, or 80-second delay. Estimates of sensitivity to reinforcement amount and sensitivity to reinforcement delay were determined using (1) a simple linear analysis and (2) an analysis of logarithmically transformed response ratios. Both analyses revealed that physical activity decreased sensitivity to reinforcement amount and sensitivity to reinforcement delay. These findings indicate that (1) physical activity has significant but functionally opposing effects on the behavioral processes that contribute to impulsive choice and (2) both quantitative methods of analysis are appropriate for use in single-response, discrete-trial procedures. PMID:26964905

Choice Impulsivity: Definitions, Measurement Issues, and Clinical Implications

PubMed Central

Hamilton, Kristen R.; Mitchell, Marci R.; Wing, Victoria C.; Balodis, Iris M.; Bickel, Warren K.; Fillmore, Mark; Lane, Scott D.; Lejuez, C. W.; Littlefield, Andrew K.; Luijten, Maartje; Mathias, Charles W.; Mitchell, Suzanne H.; Napier, T. Celeste; Reynolds, Brady; Schütz, Christian G.; Setlow, Barry; Sher, Kenneth J.; Swann, Alan C.; Tedford, Stephanie E.; White, Melanie J.; Winstanley, Catharine A.; Yi, Richard; Potenza, Marc N.; Moeller, F. Gerard

2015-01-01

Background Impulsivity critically relates to many psychiatric disorders. Given the multi-faceted construct that impulsivity represents, defining core aspects of impulsivity is vital for the assessment and understanding of clinical conditions. Choice impulsivity (CI), involving the preferential selection of smaller sooner rewards over larger later rewards, represents one important type of impulsivity. Method The International Society for Research on Impulsivity (InSRI) convened to discuss the definition and assessment of CI and provide recommendations regarding measurement across species. Results Commonly used preclinical and clinical CI behavioral tasks are described, and considerations for each task are provided to guide CI task selection. Differences in assessment of CI (self-report, behavioral) and calculating CI indices (e.g., area-under-the-curve, indifference point, steepness of discounting curve) are discussed along with properties of specific behavioral tasks used in preclinical and clinical settings. Conclusions The InSRI group recommends inclusion of measures of CI in human studies examining impulsivity. Animal studies examining impulsivity should also include assessments of CI and these measures should be harmonized in accordance with human studies of the disorders being modeled in the preclinical investigations. The choice of specific CI measures to be included should be based on the goals of the study and existing preclinical and clinical literature using established CI measures. PMID:25867841

Impulsive suicide attempts: a systematic literature review of definitions, characteristics and risk factors.

PubMed

Rimkeviciene, Jurgita; O'Gorman, John; De Leo, Diego

2015-01-15

Extensive research on impulsive suicide attempts, but lack of agreement on the use of this term indicates the need for a systematic literature review of the area. The aim of this review was to examine definitions and likely correlates of impulsive attempts. A search of Medline, Psychinfo, Scopus, Proquest and Web of Knowledge databases was conducted. Additional articles were identified using the cross-referencing function of Google Scholar. 179 relevant papers were identified. Four different groups of research criteria used to assess suicide attempt impulsivity emerged: (a) time-related criteria, (b) absence of proximal planning/preparations, (c) presence of suicide plan in lifetime/previous year, and (d) other. Subsequent analysis used these criteria to compare results from different studies on 20 most researched hypotheses. Conclusions regarding the characteristics of impulsive attempts are more consistent than those on the risk factors specific to such attempts. No risk factors were identified that uniformly related to suicide attempt impulsivity across all criteria groups, but relationships emerged between separate criteria and specific characteristics of suicide attempters. Only published articles were included. Large inconsistencies in methods of the studies included in this review prevented comparison of effect sizes. The vast disparities in findings on risk factors for impulsive suicide attempts among different criteria groups suggest the need to address the methodological issues in defining suicide attempt impulsivity before further research into correlates of such attempts can effectively progress. Specific recommendations are offered for necessary research. Copyright © 2014 Elsevier B.V. All rights reserved.

Selective Attention of Impulsive and Reflective Children. Research Report No. 66.

ERIC Educational Resources Information Center

Egeland, Byron; Thibodeau, Anne

The present investigation looked at selective attention in impulsive and reflective children using a central/incidental task similar to that used by Hagen, 1967. In order to examine developmental change in selective attention, children at kindergarten, second, and fifth grades were tested. The central recall task involved presenting the child with…

On the origin of multiply-impulsive emission from solar flares. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Karpen, J. T.

1980-01-01

A set of solar hard X-ray bursts observed with the hard X-ray burst spectrometer on board the OSO-5 satellite was analyzed. The multiply-impulsive two stage events were selected on the basis of both morphological characteristics and association with appropriate phenomena at other wavelengths. Coincident radio, soft X-ray, H-alpha interplanetary particle, and magnetographic data were obtained from several observatories, to aid in developing a comprehensive picture of the physical processes underlying these complex bursts. Two classes of multiply impulsive bursts were identified: events whose components spikes apparently originate in one location, and events in which groups of spikes appear to come from separate regions which flare sequentially. The origin of multiplicity in the case of a single source region remains unidentified. Purely impulsive emissions show no sign of betatron acceleration, thus eliminating this mechanisn as a candidate for inducing multiply spiked structure. The majority of the two stage bursts, however, exhibited spectral behavior consistent with the betatron model, for the first few minutes of the second stage. Betatron acceleration thus has been identified as a common second stage phenomenon.

[The application of impulse magnetic therapy for the treatment of the patients presenting with lymphedema of the lower extremities].

PubMed

Kulchitskaya, D B; Gerasimenko, M Yu; Aphanova, T V; Konchugova, T V

The principal objective of the present work was to evaluate the influence of impulse magnetic therapy on the state of the microcirculatory system in the patients presenting with lymphedema of the lower extremities. The study included 59 patients with stage of 1 and 2 lymphedema who were divided into two groups. Those comprising the first group had impulse magnetic therapy applied to their lower extremities while the patients making up the second group served as controls. All the patients were examined with the use of the laser Doppler flowmetry (LDF) that revealed the initially present pathological changes in the microcirculatory system of their lower extremities. The study has demonstrated that the application of impulse magnetic therapy produced a positive effect on all the constituent components of the microcirculatory blood stream of the patients suffering from lymphedema of the lower extremities. Specifically, the initially increased arteriolar tonus was decreased, the blood flow in the capillary vessels was improved, and congestive phenomena in the venular segments of the microcirculation blood stream were markedly reduced. The results of the LDF examination in the control group gave no evidence of significant changes in the patients' microcirculatory system. The results of the LDF examination of the patients of the control group suggested the absence of any appreciable changes in the microcirculatory system. The present study has demonstrated the advisability of the application of impulse magnetic therapy for the treatment of the patients presenting with lymphedema of the lower extremities as a minimally invasive technique for the evaluation of the condition of the microcirculatory system and the objective assessment of the effectiveness of the outcomes of physiotherapy in the patients with vascular pathology.

Performance of Solar Electric Powered Deep Space Missions Using Hall Thruster Propulsion

NASA Technical Reports Server (NTRS)

Witzberger, Kevin E.; Manzella, David

2006-01-01

Power limited, low-thrust trajectories were assessed for missions to Jupiter, Saturn, and Neptune utilizing a single Venus Gravity Assist (VGA) and a primary propulsion system based on either a 3-kW high voltage Hall thruster, of the type being developed by the NASA In-Space Propulsion Technology Program, or an 8-kW variant of this thruster. These Hall thrusters operate with specific impulses below 3,000 seconds. A trade study was conducted to examine mission parameters that include: net delivered mass (NDM), beginning-of-life (BOL) solar array power, heliocentric transfer time, required launch vehicle, number of operating thrusters, and throttle profile. The top performing spacecraft configuration was defined to be the one that delivered the highest mass for a range of transfer times. In order to evaluate the potential future benefit of using next generation Hall thrusters as the primary propulsion system, comparisons were made with the advanced state-of-the-art (ASOA), 7-kW, 4,100 second NASA's Evolutionary Xenon Thruster (NEXT) for the same mission scenarios. For the BOL array powers considered in this study (less than 30 kW), the results show that the performance of the Hall thrusters, relative to NEXT, is largely dependant on the performance capability of the launch vehicle, and that at least a 10 percent performance gain, equating to at least an additional 200 kg dry mass at each target planet, is achieved over the higher specific impulse NEXT when launched on an Atlas 551.

Effects of cannabis on impulsivity: a systematic review of neuroimaging findings.

PubMed

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

2014-01-01

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.

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

PubMed Central

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

2014-01-01

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

Analysis of an open cycle gas core nuclear propulsion system using MHD driven vortices for fuel containment

NASA Astrophysics Data System (ADS)

Sedwick, Raymond John

1998-12-01

A novel method for containing gaseous uranium vapor in an open cycle nuclear space propulsion system is developed. In an attempt to increase the operating temperature of the nuclear reactor beyond the melting point of solid fuel rods (thus increasing specific impulse), the fuel is instead suspended as a vapor in the propellant using the pressure forces developed in a confined vortex flow. The introduction of the fuel as uranium hexafluoride is found to be effective in maintaining its vapor phase in the feed passages from the tank, but not in the main vortex. A mechanism by which the resulting condensation of the uranium may be tolerated is identified, and the electro- optical properties of the resulting mixture are investigated. Containment is modeled using a 1D- axisymmetric geometry, and radiative heat transfer is found to restrict the maximum specific impulse of the system to 1500 seconds using pumping pressures of 500 atm. The specific impulse is related to this pressure as pm1/4, allowing only marginal increases in Isp at increased pressure levels. Additional 2D- axisymmetric issues, such as non-uniform current distribution and bypass flows through the boundary layers, are investigated, with possible methods of solution cited. A two-group, two-region reactor analysis is performed, estimating the mass of the reactor to be about 10 metric tonnes, and establishing the thrust to weight ratio achievable by the system at about 50. To reduce the mass of the power system, a scheme for using cross-flow heat exchange with the propellant flow to minimize (and possibly eliminate) the need for radiators to reject waste heat is presented. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Impulsive personality and the ability to resist immediate reward: an fMRI study examining interindividual differences in the neural mechanisms underlying self-control.

PubMed

Diekhof, Esther Kristina; Nerenberg, Lesly; Falkai, Peter; Dechent, Peter; Baudewig, Jürgen; Gruber, Oliver

2012-12-01

The ability to resist immediate rewards is crucial for lifetime success and individual well-being. Using functional magnetic resonance imaging, we assessed the association between trait impulsivity and the neural underpinnings of the ability to control immediate reward desiring. Low and high extreme impulsivity groups were compared with regard to their behavioral performance and brain activation in situations, in which they had to forego immediate rewards with varying value to achieve a superordinate long-term goal. We found that highly impulsive (HI) individuals, who successfully compensated for their lack in behavioral self-control, engaged two complementary brain mechanisms when choosing actions in favor of a long-term goal, but at the expense of an immediate reward. First, self-controlled decisions led to a general attenuation of reward-related activation in the nucleus accumbens, which was accompanied by an increased inverse connectivity with the anteroventral prefrontal cortex. Second, HI subjects controlled their desire for increasingly valuable, but suboptimal rewards through a linear reduction of activation in the ventromedial prefrontal cortex (VMPFC). This was achieved by an increased inverse coupling between the VMPFC and the ventral striatum. Importantly, the neural mechanisms observed in the HI group differed from those in extremely controlled individuals, despite similar behavioral performance. Collectively, these results suggest trait-specific neural mechanisms that allow HI individuals to control their desire for immediate reward. Copyright © 2011 Wiley Periodicals, Inc.

Subjective assessment of simulated helicopter blade-slap noise

NASA Technical Reports Server (NTRS)

Lawton, B. W.

1976-01-01

The effects of several characteristics of helicopter blade slap upon human annoyance are examined. Blade slap noise was simulated by using continuous and impulsive noises characterized by five parameters: The number of sine waves in a single impulse; the frequency of the sine waves; the impulse repetition frequency; the sound pressure level (SPL) of the continuous noise; and the idealized crest factor of the impulses. Ten second samples of noise were synthesized with each of the five parameters at representative levels. The annoyance of each noise was judged by 40 human subjects. Analysis of the subjective data indicated that each of the five parameters had a statistically significant effect upon the annoyance judgments. The impulse crest factor and SPL of the continuous noise had very strong positive relationships with annoyance. The other parameters had smaller, but still significant, effects upon the annoyance judgments.

Relations of parenting style to Chinese children’s effortful control, ego resilience, and maladjustment

PubMed Central

EISENBERG, NANCY; CHANG, LEI; MA, YUE; HUANG, XIAORUI

2009-01-01

The purpose of the study was to examine the relations of authoritative parenting and corporal punishment to Chinese first and second graders’ effortful control (EC), impulsivity, ego resilience, and maladjustment, as well as mediating relations. A parent and teacher reported on children’s EC, impulsivity, and ego resilience; parents reported on children’s internalizing symptoms and their own parenting, and teachers and peers reported on children’s externalizing symptoms. Authoritative parenting and low corporal punishment predicted high EC, and EC mediated the relation between parenting and externalizing problems. In addition, impulsivity mediated the relation of corporal punishment to externalizing problems. The relation of parenting to children’s ego resilience was mediated by EC and/or impulsivity, and ego resilience mediated the relations of EC and impulsivity to internalizing problems. PMID:19338693

Theoretical performance of some rocket propellants containing hydrogen, nitrogen, and oxygen

NASA Technical Reports Server (NTRS)

Miller, Riley O; Ordin, Paul M

1948-01-01

Theoretical performance data including nozzle-exit temperature, specific impulse, volume specific impulse and composition, temperature, and mean molecular weight of reaction products based on frozen equilibrium and isentropic expansion are presented for 13 propellant combinations at reaction pressure of 300 pounds per square inch absolute and expansion ratio of 20.4. On basis of maximum specific impulse alone, five fuels had the following order for any given oxidant: liquid hydrogen, hydrazine, liquid ammonia, and either hydrazine hydrate or hydroxylamine. Three oxidants with a given fuel had the following order: liquid ozone, liquid oxygen, and 100-percent hydrogen peroxide.

Development and Characterization of High-Efficiency, High-Specific Impulse Xenon Hall Thrusters

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Jacobson, David (Technical Monitor)

2004-01-01

This dissertation presents research aimed at extending the efficient operation of 1600 s specific impulse Hall thruster technology to the 2000 to 3000 s range. Motivated by previous industry efforts and mission studies, the aim of this research was to develop and characterize xenon Hall thrusters capable of both high-specific impulse and high-efficiency operation. During the development phase, the laboratory-model NASA 173M Hall thrusters were designed and their performance and plasma characteristics were evaluated. Experiments with the NASA-173M version 1 (v1) validated the plasma lens magnetic field design. Experiments with the NASA 173M version 2 (v2) showed there was a minimum current density and optimum magnetic field topography at which efficiency monotonically increased with voltage. Comparison of the thrusters showed that efficiency can be optimized for specific impulse by varying the plasma lens. During the characterization phase, additional plasma properties of the NASA 173Mv2 were measured and a performance model was derived. Results from the model and experimental data showed how efficient operation at high-specific impulse was enabled through regulation of the electron current with the magnetic field. The electron Hall parameter was approximately constant with voltage, which confirmed efficient operation can be realized only over a limited range of Hall parameters.

A centre-triggered magnesium fuelled cathodic arc thruster uses sublimation to deliver a record high specific impulse

NASA Astrophysics Data System (ADS)

Neumann, Patrick R. C.; Bilek, Marcela; McKenzie, David R.

2016-08-01

The cathodic arc is a high current, low voltage discharge that operates in vacuum and provides a stream of highly ionised plasma from a solid conducting cathode. The high ion velocities, together with the high ionisation fraction and the quasineutrality of the exhaust stream, make the cathodic arc an attractive plasma source for spacecraft propulsion applications. The specific impulse of the cathodic arc thruster is substantially increased when the emission of neutral species is reduced. Here, we demonstrate a reduction of neutral emission by exploiting sublimation in cathode spots and enhanced ionisation of the plasma in short, high-current pulses. This, combined with the enhanced directionality due to the efficient erosion profiles created by centre-triggering, substantially increases the specific impulse. We present experimentally measured specific impulses and jet power efficiencies for titanium and magnesium fuels. Our Mg fuelled source provides the highest reported specific impulse for a gridless ion thruster and is competitive with all flight rated ion thrusters. We present a model based on cathode sublimation and melting at the cathodic arc spot explaining the outstanding performance of the Mg fuelled source. A further significant advantage of an Mg-fuelled thruster is the abundance of Mg in asteroidal material and in space junk, providing an opportunity for utilising these resources in space.

Sustained impact of inattention and hyperactivity-impulsivity on peer problems: mediating roles of prosocial skills and conduct problems in a community sample of children.

PubMed

Andrade, Brendan F; Tannock, Rosemary

2014-06-01

This prospective 2-year longitudinal study tested whether inattentive and hyperactive/impulsive symptom dimensions predicted future peer problems, when accounting for concurrent conduct problems and prosocial skills. A community sample of 492 children (49 % female) who ranged in age from 6 to 10 years (M = 8.6, SD = .93) was recruited. Teacher reports of children's inattention, and hyperactivity/impulsivity symptoms, conduct problems, prosocial skills and peer problems were collected in two consecutive school years. Elevated inattention and hyperactivity/impulsivity in Year-1 predicted greater peer problems in Year-2. Conduct problems in the first and second years of the study were associated with more peer problems, and explained a portion of the relationship between inattention and hyperactivity/impulsivity with peer problems. However, prosocial skills were associated with fewer peer problems in children with elevated inattention and hyperactivity/impulsivity. Inattention and hyperactivity/impulsivity have negative effects on children's peer functioning after 1-year, but concurrent conduct problems and prosocial skills have important and opposing impacts on these associations.

Ballistic impulse gauge

DOEpatents

Ault, Stanley K.

1993-01-01

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.

Ballistic impulse gauge

DOEpatents

Ault, S.K.

1993-12-21

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. 4 figures.

An Experiment on Repetitive Pulse Operation of Microwave Rocket

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oda, Yasuhisa; Shibata, Teppei; Komurasaki, Kimiya

2008-04-28

Microwave Rocket was operated with repetitive pulses. The microwave rocket model with forced breathing system was used. The pressure history in the thruster was measured and the thrust impulse was deduced. As a result, the impulse decreased at second pulse and impulses at latter pulses were constant. The dependence of the thrust performance on the partial filling rate of the thruster was compared to the thrust generation model based on the shock wave driven by microwave plasma. The experimental results showed good agreement to the predicted dependency.

Impulsivity and hopelessness as predictors of suicide-related ideation among older adults.

PubMed

Neufeld, Eva; O'Rourke, Norm

2009-10-01

Research has demonstrated that impulsivity is strongly associated with suicide-related ideation and behaviour among young adults. However, to date, the potential importance of impulsivity as a predictor of suicide-related ideation in later life has yet to be determined. Our study examined impulsivity, hopelessness, depressive symptomatology, and sociodemographic factors vis-à-vis suicide-related ideation among older adults at risk of self-harm. A sample (n = 117) of older adults was recruited from multiple sources for this study over a 1-year period. Suicide-related ideation was measured with the Geriatric Suicide Ideation Scale, a multidimensional measure of suicide-related ideation developed for use with older adults. Canonical correlation identified 2 pairings of linear composites in which impulsivity emerged along both as significantly associated with facets of suicide-related ideation. Of note, the greater proportion of variance in impulsivity was subsumed along the second set of vectors with somatic depressive symptoms. Our findings suggest that the impulse to self-harm may be even more pronounced among older adults less likely to present as typically depressed. It is further suggested that impulsivity is more broadly associated with suicide-related ideation than hopelessness, and that screening for impulsivity as well as hopelessness may increase clinicians' ability to identify older adults at greatest risk of self-harm.

Relationship between movement time and hip moment impulse in the sagittal plane during sit-to-stand movement: a combined experimental and computer simulation study.

PubMed

Inai, Takuma; Takabayashi, Tomoya; Edama, Mutsuaki; Kubo, Masayoshi

2018-04-27

The association between repetitive hip moment impulse and the progression of hip osteoarthritis is a recently recognized area of study. A sit-to-stand movement is essential for daily life and requires hip extension moment. Although a change in the sit-to-stand movement time may influence the hip moment impulse in the sagittal plane, this effect has not been examined. The purpose of this study was to clarify the relationship between sit-to-stand movement time and hip moment impulse in the sagittal plane. Twenty subjects performed the sit-to-stand movement at a self-selected natural speed. The hip, knee, and ankle joint angles obtained from experimental trials were used to perform two computer simulations. In the first simulation, the actual sit-to-stand movement time obtained from the experiment was entered. In the second simulation, sit-to-stand movement times ranging from 0.5 to 4.0 s at intervals of 0.25 s were entered. Hip joint moments and hip moment impulses in the sagittal plane during sit-to-stand movements were calculated for both computer simulations. The reliability of the simulation model was confirmed, as indicated by the similarities in the hip joint moment waveforms (r = 0.99) and the hip moment impulses in the sagittal plane between the first computer simulation and the experiment. In the second computer simulation, the hip moment impulse in the sagittal plane decreased with a decrease in the sit-to-stand movement time, although the peak hip extension moment increased with a decrease in the movement time. These findings clarify the association between the sit-to-stand movement time and hip moment impulse in the sagittal plane and may contribute to the prevention of the progression of hip osteoarthritis.

Knee joint kinetics in response to multiple three-dimensional printed, customised foot orthoses for the treatment of medial compartment knee osteoarthritis.

PubMed

Allan, Richard; Woodburn, James; Telfer, Scott; Abbott, Mandy; Steultjens, Martijn Pm

2017-06-01

The knee adduction moment is consistently used as a surrogate measure of medial compartment loading. Foot orthoses are designed to reduce knee adduction moment via lateral wedging. The 'dose' of wedging required to optimally unload the affected compartment is unknown and variable between individuals. This study explores a personalised approach via three-dimensional printed foot orthotics to assess the biomechanical response when two design variables are altered: orthotic length and lateral wedging. Foot orthoses were created for 10 individuals with symptomatic medial knee osteoarthritis and 10 controls. Computer-aided design software was used to design four full and four three-quarter-length foot orthoses per participant each with lateral posting of 0° 'neutral', 5° rearfoot, 10° rearfoot and 5° forefoot/10° rearfoot. Three-dimensional printers were used to manufacture all foot orthoses. Three-dimensional gait analyses were performed and selected knee kinetics were analysed: first peak knee adduction moment, second peak knee adduction moment, first knee flexion moment and knee adduction moment impulse. Full-length foot orthoses provided greater reductions in first peak knee adduction moment (p = 0.038), second peak knee adduction moment (p = 0.018) and knee adduction moment impulse (p = 0.022) compared to three-quarter-length foot orthoses. Dose effect of lateral wedging was found for first peak knee adduction moment (p < 0.001), second peak knee adduction moment (p < 0.001) and knee adduction moment impulse (p < 0.001) indicating greater unloading for higher wedging angles. Significant interaction effects were found for foot orthosis length and participant group in second peak knee adduction moment (p = 0.028) and knee adduction moment impulse (p = 0.036). Significant interaction effects were found between orthotic length and wedging condition for second peak knee adduction moment (p = 0.002). No significant changes in first knee flexion moment were found. Individual heterogeneous responses to foot orthosis conditions were observed for first peak knee adduction moment, second peak knee adduction moment and knee adduction moment impulse. Biomechanical response is highly variable with personalised foot orthoses. Findings indicate that the tailoring of a personalised intervention could provide an additional benefit over standard interventions and that a three-dimensional printing approach to foot orthosis manufacturing is a viable alternative to the standard methods.

Multiple spike initiation zones in a neuron implicated in learning in the leech: a computational model.

PubMed

Crisp, Kevin M

2009-03-01

Sensitization of the defensive shortening reflex in the leech has been linked to a segmentally repeated tri-synaptic positive feedback loop. Serotonin from the R-cell enhances S-cell excitability, S-cell impulses cross an electrical synapse into the C-interneuron, and the C-interneuron excites the R-cell via a glutamatergic synapse. The C-interneuron has two unusual characteristics. First, impulses take longer to propagate from the S soma to the C soma than in the reverse direction. Second, impulses recorded from the electrically unexcitable C soma vary in amplitude when extracellular divalent cation concentrations are elevated, with smaller impulses failing to induce synaptic potentials in the R-cell. A compartmental, computational model was developed to test the sufficiency of multiple, independent spike initiation zones in the C-interneuron to explain these observations. The model displays asymmetric delays in impulse propagation across the S-C electrical synapse and graded impulse amplitudes in the C-interneuron in simulated high divalent cation concentrations.

Deriving a dosage-response relationship for community response to high-energy impulsive noise

NASA Technical Reports Server (NTRS)

Fidell, Sanford; Pearsons, Karl S.

1994-01-01

The inability to systematically predict community response to exposure to sonic booms (and other high energy impulsive sounds) is a major impediment to credible analyses of the environmental effects of supersonic flight operations. Efforts to assess community response to high energy impulsive sounds are limited in at least two important ways. First, a paucity of appropriate empirical data makes it difficult to infer a dosage-response relationship by means similar to those used in the case of general transportation noise. Second, it is unclear how well the 'equal energy hypothesis' (the notion that duration, number, and level of individual events are directly interchangeable determinants of annoyance) applies to some forms of impulsive noise exposure. Some of the issues currently under consideration by a CHABA working group addressing these problems are discussed. These include means for applying information gained in controlled exposure studies about different rates of growth of annoyance with impulsive and non-impulsive sound exposure levels, and strategies for developing a dosage-response relationship in a data-poor area.

The impact of self-reported life stress on current impulsivity in cocaine dependent adults

PubMed Central

Ross, Elizabeth L.; Yoon, Jin H.; Mahoney, James J.; Omar, Yasmine; Newton, Thomas F.; De La Garza, Richard

2014-01-01

Current cocaine treatments may be enhanced with a better understanding of the underlying mechanisms that contribute to the onset and maintenance of the disease, such as life stress and impulsivity. Life stress and impulsivity have previously been studied independently as contributors to drug use, and the current study expands upon past research by examining how these factors interact with one another. The aim of the current study was to evaluate the role of life stress in predicting impulsivity in a non-treatment seeking cocaine-dependent sample (N = 112). Analyses revealed that trait impulsivity (as measured by the Barratt Impulsiveness Scale) was associated with education (r = −3.09, p < 0.01), as those who had higher educational attainment also reported lower rates of trait impulsivity. In addition, those over the age of 30 demonstrated lower impulsivity in decision-making (as measured by delay discounting) than those under 30 (t = 2.21, p = 0.03). Overall exposure to life stress was not significantly correlated to either aspect of impulsivity. However several specific life stressors were significantly related to greater impulsivity including having been put up for adoption or in foster care (t = −2.96, p < 0.01), and having a child taken away against their will (t = −2.68, p = 0.01). These findings suggest that age and education relate to impulsivity; and that while an overall compilation of life stress scores was not related to impulsivity, specific types of stress related to either being taken away from a parent or having a child taken away were. Future studies should assess these constructs longitudinally to restrict response bias. PMID:23796525

Impulse control and restrained eating among young women: Evidence for compensatory cortical activation during a chocolate-specific delayed discounting task.

PubMed

Dong, Debo; Wang, Yulin; Jackson, Todd; Chen, Shuaiyu; Wang, Yu; Zhou, Feng; Chen, Hong

2016-10-01

Theory and associated research indicate that people with elevated restrained eating (RE) scores have higher risk for binge eating, future bulimic symptom onset and weight gain. Previous imaging studies have suggested hyper-responsive reward brain area activation in response to food cues contributes to this risk but little is known about associated neural impulse control mechanisms, especially when considering links between depleted cognitive resources related to unsuccessful RE. Towards illuminating this issue, we used a chocolate-specific delayed discounting (DD) task to investigate relations between RE scores, behavior impulsivity, and corresponding neural impulse control correlates in a functional magnetic resonance imaging (fMRI) study of 27 young women. Specifically, participants were required to choose between more immediate, smaller versus delayed, larger hypothetical chocolate rewards following initial consumption of a chocolate. As predicted, RE scores were correlated positively with behavior impulse control levels. More critically, higher RE scores were associated with stronger activation in impulse control region, the dorsal-lateral prefrontal cortex (DLPFC) during the completion of difficult decision trials reflecting higher cognitive demands and resource depletion relative to easy decision trials. Exploratory analyses revealed a positive correlation between RE scores and activity in a reward system hub, the right striatum. Moreover, a positive correlation between left DLPFC and striatum activation was posited to reflect, in part, impulse control region compensation in response to stronger reward signal among women with RE elevations. Findings suggested impulse control lapses may contribute to difficulties in maintaining RE, particularly when cognitive demands are high. Copyright © 2016. Published by Elsevier Ltd.

46 CFR 160.040-2 - Type and size.

Code of Federal Regulations, 2012 CFR

2012-10-01

...: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Line-Throwing Appliance, Impulse-Projected Rocket Type (and Equipment) § 160.040-2 Type and size. (a) Impulse-projected rocket type line-throwing appliances required by... and hand directed, or suitably supported and hand directed. (b) Impulse-projected rocket type line...

46 CFR 160.040-2 - Type and size.

Code of Federal Regulations, 2011 CFR

2011-10-01

...: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Line-Throwing Appliance, Impulse-Projected Rocket Type (and Equipment) § 160.040-2 Type and size. (a) Impulse-projected rocket type line-throwing appliances required by... and hand directed, or suitably supported and hand directed. (b) Impulse-projected rocket type line...

46 CFR 160.040-2 - Type and size.

Code of Federal Regulations, 2010 CFR

2010-10-01

...: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Line-Throwing Appliance, Impulse-Projected Rocket Type (and Equipment) § 160.040-2 Type and size. (a) Impulse-projected rocket type line-throwing appliances required by... and hand directed, or suitably supported and hand directed. (b) Impulse-projected rocket type line...

46 CFR 160.040-2 - Type and size.

Code of Federal Regulations, 2013 CFR

2013-10-01

...: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Line-Throwing Appliance, Impulse-Projected Rocket Type (and Equipment) § 160.040-2 Type and size. (a) Impulse-projected rocket type line-throwing appliances required by... and hand directed, or suitably supported and hand directed. (b) Impulse-projected rocket type line...

46 CFR 160.040-2 - Type and size.

Code of Federal Regulations, 2014 CFR

2014-10-01

...: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Line-Throwing Appliance, Impulse-Projected Rocket Type (and Equipment) § 160.040-2 Type and size. (a) Impulse-projected rocket type line-throwing appliances required by... and hand directed, or suitably supported and hand directed. (b) Impulse-projected rocket type line...

Domain-Specific Impulsivity in School-Age Children

ERIC Educational Resources Information Center

Tsukayama, Eli; Duckworth, Angela Lee; Kim, Betty

2013-01-01

Impulsivity is a salient individual difference in children with well-established predictive validity for life outcomes. The current investigation proposes that impulsive behaviors vary systematically by domain. In a series of studies with ethnically and socioeconomically diverse samples of middle school students, we find that schoolwork-related…

Improving Inhibitory Control Abilities (ImpulsE)-A Promising Approach to Treat Impulsive Eating?

PubMed

Preuss, Hanna; Pinnow, Marlies; Schnicker, Katja; Legenbauer, Tanja

2017-11-01

Although there is preliminary evidence that inhibitory control training improves impulsive eating, less is known about the effects on eating behaviour and weight loss in clinical samples. Sixty-nine treatment-seeking adults with obesity (binge-eating disorder 33.3%; other specific feeding and eating disorders 40.6%) were randomly blockwise allocated to ImpulsE, an intervention to improve inhibitory control and emotion regulation abilities or a guideline-appropriate cognitive behavioural therapy (CBT)-based treatment as usual. Self-reported and performance-based impulsivity, eating disorder pathology and BMI were compared at baseline (T1), post-treatment (T2) and 1- or 3-month follow-up. ImpulsE led to better food-specific inhibition performance (p = .004), but groups did not differ regarding improvements in global Eating Disorder Examination Questionnaire (EDE-Q) score at T2. At 3-month follow-up, binge eaters benefited most from ImpulsE (p = .028) and completers of ImpulsE demonstrated a significantly greater weight reduction (p = .030). The current findings propose ImpulsE as a promising approach to treat obesity, illustrating acceptability and additional benefits for course of weight. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association.

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

PubMed

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

2014-11-01

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).

Investigation of biowaste resistojets for space station application

NASA Technical Reports Server (NTRS)

Halbach, C. R.; Page, R. J.; Mccaughey, O. J.; Short, R. A.

1972-01-01

The feasibility of using electrically conducting ceramics to heat biowaste propellants to 2000 K in resistojet thrustors was demonstrated. These thrustors are being developed for use on the space station. Among the candidate ceramic heater materials, zirconia and thoria are chemically resistant to the biopropellants, and they are also sufficiently conductive at high temperatures to make them suitable for the heater elements in these thrustors. A proof of concept thrustor design is presented, incorporating a multiple passage cylindrical heater made of zirconia ceramic which is capable of operating at 2000 K wall temperature with CO2 and H2O biopropellants. For the 25 mlb size thrustor, specific impulses of 200 seconds for CO2 and 275 seconds for H2O biopropellants are predicted.

Impulsivity in binge eating disorder: food cues elicit increased reward responses and disinhibition.

PubMed

Schag, Kathrin; Teufel, Martin; Junne, Florian; Preissl, Hubert; Hautzinger, Martin; Zipfel, Stephan; Giel, Katrin Elisabeth

2013-01-01

Binge eating disorder (BED) represents a distinct eating disorder diagnosis. Current approaches assume increased impulsivity to be one factor leading to binge eating and weight gain. We used eye tracking to investigate both components of impulsivity, namely reward sensitivity and rash-spontaneous behaviour towards food in BED for the first time. Overweight and obese people with BED (BED+; n = 25), without BED (BED-; n = 26) and healthy normal-weight controls (NWC; n = 25) performed a free exploration paradigm measuring reward sensitivity (experiment 1) and a modified antisaccade paradigm measuring disinhibited, rash-spontaneous behaviour (experiment 2) using food and nonfood stimuli. Additionally, trait impulsivity was assessed. In experiment 1, all participants located their initial fixations more often on food stimuli and BED+ participants gazed longer on food stimuli in comparison with BED- and NWC participants. In experiment 2, BED+ participants had more difficulties inhibiting saccades towards food and nonfood stimuli compared with both other groups in first saccades, and especially towards food stimuli in second saccades and concerning sequences of first and second saccades. BED- participants did not differ significantly from NWC participants in both experiments. Additionally, eye tracking performance was associated with self-reported reward responsiveness and self-control. According to these results, food-related reward sensitivity and rash-spontaneous behaviour, as the two components of impulsivity, are increased in BED in comparison with weight-matched and normal-weight controls. This indicates that BED represents a neurobehavioural phenotype of obesity that is characterised by increased impulsivity. Interventions for BED should target these special needs of affected patients.

Kinetics of cycle length dependence of ventricular repolarization: effect of autonomic blockade

NASA Technical Reports Server (NTRS)

Raeder, E. A.; Albrecht, P.; Perrott, M.; Cohen, R. J.

1995-01-01

INTRODUCTION: Beat-to-beat adaptation of ventricular repolarization duration to cardiac cycle length and autonomic activity has not been previously characterized in the spontaneously beating human heart. METHODS AND RESULTS: The ECG of 14 healthy subjects was recorded from the supine and upright positions. Autonomic blockade was accomplished by atropine and propranolol. RR and RT intervals were measured by a computer algorithm, and the impulse response (h) from RR to RT computed. In the supine position the maximal adjustment of the RT interval occurred in the first beat following a change in cycle length (hpeak = 17.8 +/- 1.6 msec/sec), but continued to be detectable for 3.8 seconds (2.9-4.7 sec). Propranolol attenuated the peak impulse response to 15.8 +/- 4.0 msec/sec (P = NS). In the standing position the peak impulse response was increased to 25.2 +/- 5.0 msec/sec (P = 0.004 vs supine), and the impulse response duration (hdur) shortened to 1.4 seconds (1.3-1.6). This was reversed by beta blockade (hpeak = 10.7 +/- 3.6 [P = 0.005 vs standing]; hdur = 5.5 sec [4.8-6.1]). Parasympathetic and combined autonomic blockade resulted in too little residual heart rate variability to estimate the impulse response accurately. The slope of the regression of delta RT and delta RR in the supine position was 0.0177 +/- 0.0016, which was closely correlated with the peak impulse response (r = 0.91). CONCLUSIONS: System identification techniques can assist in characterizing the cycle dependence of ventricular repolarization and may provide new insights into conditions associated with abnormal repolarization.

Performance and Environmental Test Results of the High Voltage Hall Accelerator Engineering Development Unit

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Haag, Thomas; Huang, Wensheng; Shastry, Rohit; Pinero, Luis; Peterson, Todd; Mathers, Alex

2012-01-01

NASA Science Mission Directorate's In-Space Propulsion Technology Program is sponsoring the development of a 3.5 kW-class engineering development unit Hall thruster for implementation in NASA science and exploration missions. NASA Glenn and Aerojet are developing a high fidelity high voltage Hall accelerator that can achieve specific impulse magnitudes greater than 2,700 seconds and xenon throughput capability in excess of 300 kilograms. Performance, plume mappings, thermal characterization, and vibration tests of the high voltage Hall accelerator engineering development unit have been performed. Performance test results indicated that at 3.9 kW the thruster achieved a total thrust efficiency and specific impulse of 58%, and 2,700 sec, respectively. Thermal characterization tests indicated that the thruster component temperatures were within the prescribed material maximum operating temperature limits during full power thruster operation. Finally, thruster vibration tests indicated that the thruster survived the 3-axes qualification full-level random vibration test series. Pre and post-vibration test performance mappings indicated almost identical thruster performance. Finally, an update on the development progress of a power processing unit and a xenon feed system is provided.

Impulsive perturbations to differential equations: stable/unstable pseudo-manifolds, heteroclinic connections, and flux

NASA Astrophysics Data System (ADS)

Balasuriya, Sanjeeva

2016-12-01

State-dependent time-impulsive perturbations to a two-dimensional autonomous flow with stable and unstable manifolds are analysed by posing in terms of an integral equation which is valid in both forwards- and backwards-time. The impulses destroy the smooth invariant manifolds, necessitating new definitions for stable and unstable pseudo-manifolds. Their time-evolution is characterised by solving a Volterra integral equation of the second kind with discontinuous inhomogeniety. A criteria for heteroclinic trajectory persistence in this impulsive context is developed, as is a quantification of an instantaneous flux across broken heteroclinic manifolds. Several examples, including a kicked Duffing oscillator and an underwater explosion in the vicinity of an eddy, are used to illustrate the theory.

Food-Related Impulsivity in Obesity and Binge Eating Disorder-A Systematic Update of the Evidence.

PubMed

Giel, Katrin E; Teufel, Martin; Junne, Florian; Zipfel, Stephan; Schag, Kathrin

2017-10-27

The specific eating pattern of Binge Eating Disorder (BED) patients has provoked the assumption that BED might represent a phenotype within the obesity spectrum that is characterized by increased impulsivity. Following the guidelines of the PRISMA statement (preferred reporting items for systematic reviews and meta-analyses), we here provide a systematic update on the evidence on food-related impulsivity in obese individuals, with and without BED, as well as normal-weight individuals. We separately analyzed potential group differences in the impulsivity components of reward sensitivity and rash-spontaneous behavior. Our search resulted in twenty experimental studies with high methodological quality. The synthesis of the latest evidence consolidates conclusions drawn in our initial systematic review that BED represents a distinct phenotype within the obesity spectrum that is characterized by increased impulsivity. Rash-spontaneous behavior in general, and specifically towards food, is increased in BED, while food-specific reward sensitivity is also increased in obese individuals without BED, but potentially to a lesser degree. A major next step for research entails the investigation of sub-domains and temporal components of inhibitory control in BED and obesity. Based on the evidence of impaired inhibitory control in BED, affected patients might profit from interventions that address impulsive behavior.

Domain-Specific Relationships in Sexual Measures of Impulsive Behavior.

PubMed

Mahoney, Colin T; Lawyer, Steven R

2018-04-25

Impulsivity is an important construct for understanding sexual behaviors, but behavioral and self-report measures of impulsivity often are not correlated. One possible explanation for this is that there is little shared variance in the measures because behavioral measures index impulsivity by asking questions about monetary preferences, while self-report measures index impulsivity by asking about a broad range of real-world outcomes (including those of a sexual nature) largely unrelated to money-related preferences. Undergraduate students (total N = 105; female n = 77, male n = 28) completed laboratory measures-delay discounting (DD) and probability discounting (PD)-for two different outcomes-money and sexual activity. Participants also completed the Delaying Gratification Inventory (DGI), which measures difficulty with delaying gratification (i.e., impulsivity) across different domains, including money and physical pleasures. Findings indicated that DD and PD for money were not related to any of the DGI subscales. However, DD for sexual activity was significantly related to the DGI Physical Pleasures subscale, but not other subscales. These findings suggest that the relationship between behavioral and self-report measures of impulsive choice may be stronger when both are measuring domain-specific rather than domain-general behavioral patterns, but further research is warranted.

Experimental and simulation study of a Gaseous oxygen/Gaseous hydrogen vortex cooling thrust chamber

NASA Astrophysics Data System (ADS)

Yu, Nanjia; Zhao, Bo; Li, Gongnan; Wang, Jue

2016-01-01

In this paper, RNG k-ε turbulence model and PDF non-premixed combustion model are used to simulate the influence of the diameter of the ring of hydrogen injectors and oxidizer-to-fuel ratio on the specific impulse of the vortex cooling thrust chamber. The simulation results and the experimental tests of a 2000 N Gaseous oxygen/Gaseous hydrogen vortex cooling thrust chamber reveal that the efficiency of the specific impulse improves significantly with increasing of the diameter of the ring of hydrogen injectors. Moreover, the optimum efficiency of the specific impulse is obtained when the oxidizer-to-fuel ratio is near the stoichiometric ratio.

Differential contributions of cortical thickness and surface area to trait impulsivity in healthy young adults.

PubMed

Kubera, Katharina M; Schmitgen, Mike M; Maier-Hein, Klaus H; Thomann, Philipp A; Hirjak, Dusan; Wolf, Robert C

2018-05-08

Impulsivity is an essential human personality trait and highly relevant for the development of several mental disorders. There is evidence that impulsivity is heritable, yet little is known about neural correlates reflecting early brain development. Here, we address the question whether motor, attentional and non-planning components, as reflected by the Barratt Impulsiveness Scale (BIS-11), are distinctly associated with cortical thickness and surface area variations in young healthy individuals. We investigated cortical thickness and surface area in 54 healthy volunteers (m/f = 30%/70%; age mean/SD = 24.9/4.02) using structural magnetic resonance imaging at 3 T together with surface-based analysis techniques. Impulsivity was examined on the Barratt impulsiveness scale (BIS-11) and related to the two distinct cortical measurements. Higher BIS-11 total scores were negatively associated with cortical thickness variations in the left lingual gyrus, left superior temporal gyrus, right cuneus, and right superior parietal gyrus (p<0.05 cluster-wise probability [CWP] corrected). Higher BIS-11 nonplanning scores were negatively associated with cortical thickness variations in bilateral pericalcarine gyrus (p<0.05 CWP corr.). In the orbitofrontal cortex motor impulsivity associated cortical thickness differs significantly between male and female. These data suggest distinct neurodevelopmental trajectories underlying impulsivity in healthy subjects. Impulsivity total scores appear to be specifically related to cortical thickness variations, in contrast to variations of cortical surface area. Furthermore, our findings underscores the importance of better characterizing gender-specific structural correlates of impulsivity. Copyright © 2018. Published by Elsevier B.V.

Optimization of operation conditions and configurations for solid-propellant ducted rocket combustors

NASA Astrophysics Data System (ADS)

Onn, Shing-Chung; Chiang, Hau-Jei; Hwang, Hang-Che; Wei, Jen-Ko; Cherng, Dao-Lien

1993-06-01

The dynamic behavior of a 2D turbulent mixing and combustion process has been studied numerically in the main combustion chamber of a solid-propellant ducted rocket (SDR). The mathematical model is based on the Favre-averaged conservation equations developed by Cherng (1990). Combustion efficiency, rather than specific impulse from earlier studies, is applied successfully to optimize the effects of two parameters by a multiple linear regression model. Specifically, the fuel-air equivalence ratio of the operating conditions and the air inlet location of configurations for the SDR combustor have been studied. For a equivalence ratio near the stoichiometric condition, the use of specific impulse or combustion efficiency will show similar trend in characterizing the reacting flow field in the combustor. For the overall fuel lean operating conditions, the change of combustion efficiency is much more sensitive to that of air inlet location than specific impulse does, suggesting combustion efficiency a better property than specific impulse in representing the condition toward flammability limits. In addition, the air inlet for maximum efficiency, in general, appears to be located at downstream of that for highest specific impulse. The optimal case for the effects of two parameters occurs at fuel lean condition, which shows a larger recirculation zone in front, deeper penetration of ram air into the combustor and much larger high temperature zone near the centerline of the combustor exit than those shown in the optimal case for overall equivalence ratio close to stoichiometric.

Dysfunctional decision-making in pathological gambling: pattern specificity and the role of impulsivity.

PubMed

Kräplin, Anja; Dshemuchadse, Maja; Behrendt, Silke; Scherbaum, Stefan; Goschke, Thomas; Bühringer, Gerhard

2014-03-30

Dysfunctional decision-making in individuals with pathological gambling (PGs) may result from dominating reward-driven processes, indicated by higher impulsivity. In the current study we examined (1) if PGs show specific decision-making impairments related to dominating reward-driven processes rather than to strategic planning deficits and (2) whether these impairments are related to impulsivity. Nineteen PGs according to DSM-IV and 19 matched control subjects undertook the Cambridge Gambling Task (CGT) to assess decision-making. The delay discounting paradigm (DDP) as well as the UPPS Impulsive Behavior Scale (measuring urgency, premeditation, perseverance and sensation seeking) were administered as multidimensional measures of impulsivity. Results revealed that (1) PGs exhibited higher risk seeking and an immediate reward focus in the CGT and, in contrast, comparable strategic planning to the control group. (2) Decision-making impairments were related to more severe delay discounting and, specifically, to increased urgency and less premeditation. Our findings suggest (1) the necessity to disentangle decision-making components in order to improve etiological models of PGs, and (2) that urgency and premeditation are specifically related to disadvantageous decision-making and should be tackled in intervention strategies focusing on emotion tolerance and control strategies. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Impulsivity and Gambling Type Among Treatment-Seeking Disordered Gamblers: An Explorative Study.

PubMed

Lutri, Vittorio; Soldini, Emiliano; Ronzitti, Silvia; Smith, Neil; Clerici, Massimo; Blaszczynski, Alex; Bowden-Jones, Henrietta

2018-03-03

Several studies have found that certain traits of impulsivity are associated with gambling disorder, and influence its severity. Furthermore, it has been suggested that some forms of gambling, particularly electronic gambling machines, are particularly widespread among pathological gamblers. In the present, exploratory study, we aim to clarify the role played by impulsivity in influencing the choice of specific gambling activities, by examining the relation between individual dimensions of impulsivity, and the choice of specific gambling activities in a clinical population. 100 consecutively admitted pathological gamblers at the National Problem Gambling Clinic in London (UK) in 2014 were administered the UPPS-P and BIS-11 impulsivity questionnaires, the Problem Gambling Severity Index, and underwent a structured interview concerning their gambling activities in the month and year prior to assessment. The correlation between individual gambling activities and impulsivity dimensions was analyzed both at a bivariate level, and using logistic regression. We found a significant correlation between Negative Urgency, Motor impulsivity and low-stakes machine gambling on multivariate analysis. Negative urgency (i.e. the tendency to act impulsively in response to negative affect), and Motor impulsivity (a tendency to rash action and restlessness) might be mediating factors in the choice of electronic gambling machines, particularly among patients whose gambling is escape-oriented. Structural and situational characteristics of gambling machines, particularly the widespread availability of low-stakes-rather than high-stakes-gaming machines, might concur to the choice of this form of gambling among individuals who present higher negative urgency and restlessness.

Validity of proposed DSM-5 ADHD impulsivity symptoms in children.

PubMed

Ünsel Bolat, Gül; Ercan, Eyüp Sabri; Salum, Giovanni Abrahão; Bilaç, Öznur; Massuti, Rafael; Uysal Özaslan, Taciser; Bolat, Hilmi; Rohde, Luis Augusto

2016-10-01

The American Psychiatric Association (APA) working group on Attention-Deficit/Hyperactivity Disorder (ADHD) proposed the inclusion of four new impulsivity symptoms. However, they were not included in DSM-5 due to the lack of sufficient evidence. The aim of this study is to investigate the performance of the proposed four ADHD impulsivity symptoms with respect to: (a) ADHD factor structure; (b) performance in predicting clinical impairment; (c) specificity for ADHD diagnosis and (d) best symptomatic threshold to predict clinical impairment. The sample comprised 416 children (31 ADHD subjects according to both DSM-IV and proposed DSM-5, 20 ADHD subjects according to just one diagnostic system and 365 controls) from 12 schools. Diagnoses were derived using semi-structured interviews and ADHD rating scales. Results from confirmatory factor analysis indicate that addition of the four new impulsivity items provided a slightly better factor structure if compared to models including only 18 items. Regression analyses showed that only one of the new impulsivity symptoms (impatient) was part of the list of best predictors of impairment. None of the four new impulsivity items was specifically associated with ADHD diagnosis. The best cutoff point in the hyperactivity/impulsivity dimension for predicting impairment did not change significantly. Overall, our findings suggest that the determination on how to best capture impulsivity dimension as part of the ADHD construct needs more investigation and that there is not enough evidence to include these four assessed impulsivity symptoms as part of the ADHD criteria.

Different relations between schedule-induced polydipsia and impulsive behaviour in the Spontaneously Hypertensive Rat and in high impulsive Wistar rats: questioning the role of impulsivity in adjunctive behaviour.

PubMed

Ibias, Javier; Pellón, Ricardo

2014-09-01

Rats belonging to three different strains (15 Wistar, 8 Spontaneously Hypertensive - SHR- and 8 Wistar Kyoto - WKY-) were used to evaluate the possible relationship between different levels of impulsivity and development of schedule-induced polydipsia (SIP). We first measured the rats' levels of impulsivity by means of delay-discounting and indifference-point procedures. Secondly, development of SIP was studied under a series of fixed time 15, 30, 60 and 120s food schedules, which were counterbalanced by means of a Latin-square design. Finally, we re-assessed the rats' levels of impulsivity by replicating the delay-discounting test. The findings showed that, starting from equivalent levels of impulsivity, development of SIP differed among the groups of rats. In comparison with the rest of the animals, the SHRs were observed to attain elevated drinking rates under SIP. On the other hand, the Wistar rats which had initial high impulsivity levels similar to those of the SHRs, displayed the lowest rates of induced drinking. Moreover, low levels of impulsivity in Wistar rats prior to SIP acquisition were reflected into high drinking rates. Relation of SIP and impulsivity is questioned by present results, which gives ground to the understanding of the behavioural mechanisms involved in adjunctive behaviour and its usefulness as an animal model of excessive behaviour. Copyright © 2014 Elsevier B.V. All rights reserved.

Dual-fuel, dual-mode rocket engine

NASA Technical Reports Server (NTRS)

Martin, James A. (Inventor)

1989-01-01

The invention relates to a dual fuel, dual mode rocket engine designed to improve the performance of earth-to-orbit vehicles. For any vehicle that operates from the earth's surface to earth orbit, it is advantageous to use two different fuels during its ascent. A high density impulse fuel, such as kerosene, is most efficient during the first half of the trajectory. A high specific impulse fuel, such as hydrogen, is most efficient during the second half of the trajectory. The invention allows both fuels to be used with a single rocket engine. It does so by adding a minimum number of state-of-the-art components to baseline single made rocket engines, and is therefore relatively easy to develop for near term applications. The novelty of this invention resides in the mixing of fuels before exhaust nozzle cooling. This allows all of the engine fuel to cool the exhaust nozzle, and allows the ratio of fuels used throughout the flight depend solely on performance requirements, not cooling requirements.

Advanced concepts. [specific impulse, mass drivers, electromagnetic launchers, and the rail gun

NASA Technical Reports Server (NTRS)

Banks, B. A.

1980-01-01

The relative strengths of those interactions which enable propulsive forces are listed as well as the specific impulse of various propellants. Graphics show the linear synchronous motor of the mass driver, the principle of the direct current electromagnetic launcher, and the characteristics of the rail gun.

The evolutionary development of high specific impulse electric thruster technology

NASA Technical Reports Server (NTRS)

Sovey, James S.; Hamley, John A.; Patterson, Michael J.; Rawlin, Vincent K.; Myers, Roger M.

1992-01-01

Electric propulsion flight and technology demonstrations conducted primarily by Europe, Japan, China, the U.S., and the USSR are reviewed. Evolutionary mission applications for high specific impulse electric thruster systems are discussed, and the status of arcjet, ion, and magnetoplasmadynamic thrusters and associated power processor technologies are summarized.

Impulsivity in Alcohol-Dependent Patients with and without ADHD: The Role of Atomoxetine.

PubMed

Coppola, Maurizio; Mondola, Raffaella

2018-06-07

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by symptoms of hyperactivity, inattention, and impulsivity. As shown in the literature, this disorder is frequently associated with alcohol and drug abuse. Patients affected by ADHD show high levels of impulsivity and sensation seeking. These characteristics can significantly increase the risk of alcohol abuse, which is itself a clinical condition associated with high levels of impulsivity. Clinical studies suggest that atomoxetine is effective and safe in patients affected by both ADHD and alcohol dependence; however, information focused specifically on impulsivity is very limited. In an open-label study, we evaluated the difference in impulsivity level between alcohol-dependent patients with and without a diagnosis of ADHD. Furthermore, we hypothesized that, in patients with ADHD, atomoxetine could reduce the impulsivity trait.

Impulsive behaviour in rats induced by intracortical DOI infusions is antagonized by co-administration of an mGlu2/3 receptor agonist.

PubMed

Wischhof, Lena; Hollensteiner, Karl J; Koch, Michael

2011-12-01

The orbitofrontal cortex (OFC) and the medial prefrontal cortex (mPFC) modulate impulsive behaviours. Serotonin [5-hydroxytryptamine (5-HT)] 2A receptors have also been implicated in impulsivity and govern antagonistic interactions with metabotropic glutamate (mGlu)2/3 receptors. This study examined the interactions between 5-HT2A and mGlu2/3 receptors in the OFC and mPFC with relevance to impulsive choice and impulsive action. Impulsive choice was assessed in Lister Hooded rats, trained in a delay-discounting T-maze task, after bilateral intra-OFC infusions of the 5-HT2A/C receptor agonist DOI [(+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropan hydrochloride; 5 μg/0.5 μl] and the mGlu2/3 receptor agonist LY379268 (1 μg/0.5 μl). Impulsive action was assessed in a second group of rats trained in a five-choice serial reaction time task (5-CSRTT) and receiving bilateral intra-mPFC infusions of DOI (5 μg/0.5 μl) and LY379268 (1 μg/0.5 μl). Intra-OFC DOI increased impulsive choice, which was not seen when DOI was co-administered with LY379268. LY379268 itself had no effect on choice behaviour. Intra-mPFC DOI caused impulsive over-responding in the 5-CSRTT that was attenuated when DOI and LY379268 were co-injected. Local mPFC-infusions of LY379268 had no effect on 5-CSRTT performance. This study suggests a differential involvement of OFC and mPFC 5-HT2A receptors in impulsive choice and impulsive action. Moreover, compounds acting at mGlu2/3 receptors might have the potential to improve impulsivity-related impairments.

Genetics of impulsive behaviour

PubMed Central

Bevilacqua, Laura; Goldman, David

2013-01-01

Impulsivity, defined as the tendency to act without foresight, comprises a multitude of constructs and is associated with a variety of psychiatric disorders. Dissecting different aspects of impulsive behaviour and relating these to specific neurobiological circuits would improve our understanding of the etiology of complex behaviours for which impulsivity is key, and advance genetic studies in this behavioural domain. In this review, we will discuss the heritability of some impulsivity constructs and their possible use as endophenotypes (heritable, disease-associated intermediate phenotypes). Several functional genetic variants associated with impulsive behaviour have been identified by the candidate gene approach and re-sequencing, and whole genome strategies can be implemented for discovery of novel rare and common alleles influencing impulsivity. Via deep sequencing an uncommon HTR2B stop codon, common in one population, was discovered, with implications for understanding impulsive behaviour in both humans and rodents and for future gene discovery. PMID:23440466

Second Step: A Violence-Prevention Curriculum. Grades 6-8.

ERIC Educational Resources Information Center

Committee for Children, Seattle, WA.

"Second Step" is a curriculum designed to reduce impulsive and aggressive behavior in children in grades 6 through 8, increasing their levels of social competence through empathy training, interpersonal cognitive problem solving, behavioral social skill training, and anger management. This guide is part of the "Second Step"…

The Breakdown Characteristics of the Silicone Oil for Electric Power Apparatus

NASA Astrophysics Data System (ADS)

Yoshida, Hisashi; Yanabu, Satoru

The basic breakdown characteristics of the silicone oil as an insulating medium was studied with aim of realization of electric power apparatus which may be considered to be SF6 free and flame-retarding. As the first step, the impulse breakdown characteristics was measured with three kinds of electrodes whose electric field distributions differed. The breakdown characteristics in silicone oil was explained in relation to stressed oil volume (SOV) and the breakdown stress. At the second step the surface breakdown characteristic for impulse voltage was measured with two kinds of insulators which was set to between plane electrodes. The surface breakdown characteristic for impulse voltage was explained in relation to the ratio of the relative permittivity of oil and insulator. And on the third step, the breakdown characteristics of oil gap after interrupting small capacitive current was studied. In this experiment, the disconnecting switch to interrupt capacitive current was simulated by oil gap after interrupting impulse current, and to measure breakdown characteristics the high impulse voltage was subsequently applied. The breakdown stress in silicone oil after application of impulse current was discussed for insulation recovery characteristics.

Mission Analysis for High Specific Impulse Deep Space Exploration

NASA Technical Reports Server (NTRS)

Adams, Robert B.; Polsgrove, Tara; Brady, Hugh J. (Technical Monitor)

2002-01-01

This paper describes trajectory calculations for high specific impulse engines. Specific impulses on the order of 10,000 to 100,000 sec are predicted in a variety of fusion powered propulsion systems. This paper and its companion paper seek to build on analyses in the literature to yield an analytical routine for determining time of flight and payload fraction to a predetermined destination. The companion paper will compare the results of this analysis to the trajectories determined by several trajectory codes. The major parameters that affect time of flight and payload fraction will be identified and their sensitivities quantified. A review of existing fusion propulsion concepts and their capabilities will also be tabulated.

Current evaluation of the tripropellant concept

NASA Technical Reports Server (NTRS)

Zurawski, R. L.

1986-01-01

An analytical study was conducted to determine the specific-impulse advantages of adding metals to conventional liquid-bipropellant systems. These tripropellant systems theoretically offer higher specific impulse and increased propellant density compared with bipropellant systems. Metals considered were Be, Li, and Al. Bipropellant systems were H2/O2, N2H4/N2O4, RP-1/O2, and H2/F2. Thermochemical calculations were performed for sea-level expansion from 6.895-MN/sq. m. (1000-psia) chamber pressure over a wide range of mixture ratios and propellant compositions. Three-dimensional plots characterize the specific impulse of each tripropellant system. Technology issues pertinent to metallized propellant systems are discussed.

Relationship between anhedonia and impulsivity in schizophrenia, major depression and schizoaffective disorder.

PubMed

Amr, Mostafa; Volpe, Fernando Madalena

2013-12-01

Anhedonia and impulsivity are prominent symptoms of many psychiatric disorders and may indicate worse prognosis, notably in schizophrenia and major depression. Despite the convergence of negative outcomes from both dimensions, the relationship between anhedonia and impulsivity in psychiatric disorders has been seldom directly assessed. The objective of the present study is to examine the correlations between anhedonia and impulsivity in three diagnostic groups: major depression, schizophrenia and schizoaffective disorder. 121 outpatients (Mansoura University Hospital, Egypt) with major depressive disorder (N=29), schizophrenia (N=59), and schizoaffective disorder (N=33), were assessed and responded to the Beck Depression Inventory, Barrat's Impulsivity Scale-11, and Chapman's Social and Physical Anhedonia Scales. Physical and social anhedonia scores were negatively correlated to impulsivity scores in major depression patients. Conversely, higher scores in physical and social anhedonia predicted higher impulsivity scores in schizophrenia. No correlations between impulsivity and anhedonia were evidenced among schizoaffectives. The relationship between self-reported physical and social anhedonia and impulsivity is diagnosis-specific. Copyright © 2013 Elsevier B.V. All rights reserved.

Design feasibility via ascent optimality for next-generation spacecraft

NASA Astrophysics Data System (ADS)

Miele, A.; Mancuso, S.

This paper deals with the optimization of the ascent trajectories for single-stage-sub-orbit (SSSO), single-stage-to-orbit (SSTO), and two-stage-to-orbit (TSTO) rocket-powered spacecraft. The maximum payload weight problem is studied for different values of the engine specific impulse and spacecraft structural factor. The main conclusions are that: feasibility of SSSO spacecraft is guaranteed for all the parameter combinations considered; feasibility of SSTO spacecraft depends strongly on the parameter combination chosen; not only feasibility of TSTO spacecraft is guaranteed for all the parameter combinations considered, but the TSTO payload is several times the SSTO payload. Improvements in engine specific impulse and spacecraft structural factor are desirable and crucial for SSTO feasibility; indeed, aerodynamic improvements do not yield significant improvements in payload. For SSSO, SSTO, and TSTO spacecraft, simple engineering approximations are developed connecting the maximum payload weight to the engine specific impulse and spacecraft structural factor. With reference to the specific impulse/structural factor domain, these engineering approximations lead to the construction of zero-payload lines separating the feasibility region (positive payload) from the unfeasibility region (negative payload).

Characterization of advanced electric propulsion systems

NASA Technical Reports Server (NTRS)

Ray, P. K.

1982-01-01

Characteristics of several advanced electric propulsion systems are evaluated and compared. The propulsion systems studied are mass driver, rail gun, MPD thruster, hydrogen free radical thruster and mercury electron bombardment ion engine. These are characterized by specific impulse, overall efficiency, input power, average thrust, power to average thrust ratio and average thrust to dry weight ratio. Several important physical characteristics such as dry system mass, accelerator length, bore size and current pulse requirement are also evaluated in appropriate cases. Only the ion engine can operate at a specific impulse beyond 2000 sec. Rail gun, MPD thruster and free radical thruster are currently characterized by low efficiencies. Mass drivers have the best performance characteristics in terms of overall efficiency, power to average thrust ratio and average thrust to dry weight ratio. But, they can only operate at low specific impulses due to large power requirements and are extremely long due to limitations of driving current. Mercury ion engines have the next best performance characteristics while operating at higher specific impulses. It is concluded that, overall, ion engines have somewhat better characteristics as compared to the other electric propulsion systems.

Impulsivity, aggression and suicidal behavior in unipolar and bipolar disorders.

PubMed

Perroud, Nader; Baud, Patrick; Mouthon, Dominique; Courtet, Philippe; Malafosse, Alain

2011-11-01

Predictors of suicidal behaviors (SB) in bipolar (BD) and major depressive disorder (MDD) patients are poorly understood. It has been recognized that behavioral dysregulation characterizes SB with traits of impulsivity and aggression being particularly salient. However, little is known about how these traits are segregated among mood disorder patients with and without a history of suicide attempt (SA). This article aims to compare impulsivity and aggression between 143 controls, 138 BD and 186 MDD subjects with or without a history of SA. BD and MDD patients showed higher impulsivity scores (BIS-10 = 57.9 vs. 44.7, p < 0.0001) and more severe lifetime aggression than controls (Lifetime History of Aggression = 7.3 vs. 3.9, p < 0.0001). Whereas impulsivity helped to distinguish MDD subjects without a history of SA from those with such a history, this was not the case in BD subjects where no difference in impulsive traits was observed between BD without and with history of SA (57.2 vs. 63.2 for BIS-10; p = 0.259). Impulsive and aggressive traits were strongly correlated in suicide attempters (independently of the diagnosis) but not in non-suicide attempters. Dimensional traits were not characterized at different stages of illness. Impulsivity, as a single trait, may be a reliable suicide risk marker in MDD but not in BD patients, and its strong correlation with aggressive traits seems specifically related to SB. Our study therefore suggests that the specific dimension of impulsive aggression should be systematically assessed in mood disorder patients to address properly their suicidal risk. Copyright © 2011 Elsevier B.V. All rights reserved.

Sex differences in the reduction of impulsive choice (delay discounting) for cocaine in rats with atomoxetine and progesterone

PubMed Central

Smethells, John R.; Swalve, Natashia L.; Eberly, Lynn E.; Carroll, Marilyn E.

2016-01-01

Rationale Impulsive choice, or an inability to delay immediate gratification, has been strongly linked to the development and persistence of drug abuse. Indeed, delaying drug use itself may underlie drug addiction and relapse. Thus, employing treatments that are efficacious in reducing impulsive choice (atomoxetine; ATO) or drug-seeking behavior (progesterone; PRO) may be an effective means of treating drug addiction. Objective The current study assessed sex differences in the effects of PRO, ATO and their combination in a delay discounting paradigm for cocaine and for sucrose pellets. Method Male and female rats chose between a small-immediate or a large-delayed (0, 7.5, 15, 30, 60 sec) outcome in an impulsive choice procedure for sucrose pellets (1 vs 3 pellets) or for iv cocaine infusions (0.3 vs 0.9 mg/kg). Following baseline assessment of impulsive choice, rats received daily treatment of vehicle (VEH), PRO (0.5 mg/kg), ATO (1.5 mg/kg) or a combination (PRO + ATO) until a second assessment of impulsive choice was determined. Results Compared to the VEH group, females were less impulsive for cocaine following PRO or the PRO + ATO combined treatment, whereas males were less impulsive for cocaine following ATO. No treatment effects were observed on impulsive choice for sucrose pellets. Conclusions The present results indicate that impulsive choice for cocaine is reduced by PRO in females and by ATO in males. These findings suggest both treatments may be an effective intervention in treating cocaine abuse, but that their effectiveness differs by sex. PMID:27325394

Delay discounting and impulsivity traits in young and older gambling disorder patients.

PubMed

Steward, Trevor; Mestre-Bach, Gemma; Fernández-Aranda, Fernando; Granero, Roser; Perales, José C; Navas, Juan Francisco; Soriano-Mas, Carles; Baño, Marta; Fernández-Formoso, Jose A; Martín-Romera, Virginia; Menchón, José M; Jiménez-Murcia, Susana

2017-08-01

Impulsivity is understood to be a multidimensional construct involving aspects such as impulsive choice and impulsive traits. Delay discounting, the tendency to place greater value in immediate rewards over larger, long-term rewards, has been associated with maladaptive choices in gambling disorder (GD). Delay discounting is known to evolve with age; though no study to date has evaluated the interactions between impulsivity, GD severity and age in treatment-seeking patients. We aimed to examine whether associations between delay discounting and impulsivity traits differed between younger and older-aged GD patients. Secondly, we sought to untangle the mediating role of impulsivity in determining gambling behavior in these two age groups. GD patients (N=335) were evaluated using the UPPS-P Impulsive Behavior Scale and a delay discounting task. Structural Equation Modeling (SEM) was used to explore associations between impulsivity measures and gambling severity in young (18-30years) and old (31-70) GD patients. No differences in delay discounting were found between young and old GD patients. Significant correlations between delay discounting and urgency levels (the tendency to act rashly under emotional states) were identified only in the young GD group. Path analyses also revealed both positive and negative urgency to be a mediator of GD severity levels in young GD patients. Significant associations between impulsive choice and positive urgency are only present in young gamblers, suggesting that positive urgency influence choice behavior to a greater degree at younger ages. Implications for targeted interventions are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Extreme sensory processing patterns show a complex association with depression, and impulsivity, alexithymia, and hopelessness.

PubMed

Serafini, Gianluca; Gonda, Xenia; Canepa, Giovanna; Pompili, Maurizio; Rihmer, Zoltan; Amore, Mario; Engel-Yeger, Batya

2017-03-01

The involvement of extreme sensory processing patterns, impulsivity, alexithymia, and hopelessness was hypothesized to contribute to the complex pathophysiology of major depression and bipolar disorder. However, the nature of the relation between these variables has not been thoroughly investigated. This study aimed to explore the association between extreme sensory processing patterns, impulsivity, alexithymia, depression, and hopelessness. We recruited 281 euthymic participants (mean age=47.4±12.1) of which 62.3% with unipolar major depression and 37.7% with bipolar disorder. All participants completed the Adolescent/Adult Sensory Profile (AASP), Toronto Alexithymia Scale (TAS-20), second version of the Beck Depression Inventory (BDI-II), Barratt Impulsivity Scale (BIS), and Beck Hopelessness Scale (BHS). Lower registration of sensory input showed a significant correlation with depression, impulsivity, attentional/motor impulsivity, and alexithymia. It was significantly more frequent among participants with elevated hopelessness, and accounted for 22% of the variance in depression severity, 15% in greater impulsivity, 36% in alexithymia, and 3% in hopelessness. Elevated sensory seeking correlated with enhanced motor impulsivity and decreased non-planning impulsivity. Higher sensory sensitivity and sensory avoiding correlated with depression, impulsivity, and alexithymia. The study was limited by the relatively small sample size and cross-sectional nature of the study. Furthermore, only self-report measures that may be potentially biased by social desirability were used. Extreme sensory processing patterns, impulsivity, alexithymia, depression, and hopelessness may show a characteristic pattern in patients with major affective disorders. The careful assessment of sensory profiles may help in developing targeted interventions and improve functional/adaptive strategies. Copyright © 2016 Elsevier B.V. All rights reserved.

Genetic relations among procrastination, impulsivity, and goal-management ability: implications for the evolutionary origin of procrastination.

PubMed

Gustavson, Daniel E; Miyake, Akira; Hewitt, John K; Friedman, Naomi P

2014-06-01

Previous research has revealed a moderate and positive correlation between procrastination and impulsivity. However, little is known about why these two constructs are related. In the present study, we used behavior-genetics methodology to test three predictions derived from an evolutionary account that postulates that procrastination arose as a by-product of impulsivity: (a) Procrastination is heritable, (b) the two traits share considerable genetic variation, and (c) goal-management ability is an important component of this shared variation. These predictions were confirmed. First, both procrastination and impulsivity were moderately heritable (46% and 49%, respectively). Second, although the two traits were separable at the phenotypic level (r = .65), they were not separable at the genetic level (r genetic = 1.0). Finally, variation in goal-management ability accounted for much of this shared genetic variation. These results suggest that procrastination and impulsivity are linked primarily through genetic influences on the ability to use high-priority goals to effectively regulate actions. © The Author(s) 2014.

Genetic Relations Among Procrastination, Impulsivity, and Goal-Management Ability: Implications for the Evolutionary Origin of Procrastination

PubMed Central

Gustavson, Daniel E.; Miyake, Akira; Hewitt, John K.; Friedman, Naomi P.

2014-01-01

Previous research has revealed a moderate positive correlation between procrastination and impulsivity. However, little is known about why these two constructs are related. This study used behavioral genetic methodology to test three predictions derived from an evolutionary account that postulates that procrastination arose as a by-product of impulsivity (Steel, 2010): (a) Procrastination is heritable; (b) the two traits share considerable genetic variation; and (c) goal-management ability is an important component of this shared variation. These predictions were confirmed. First, both procrastination and impulsivity were moderately heritable (46% and 49%, respectively). Second, although the two traits were separable at the phenotypic level (r=.65), they were not separable at the genetic level (rg=1.0). Finally, variation in goal-management ability accounted for much of this shared genetic variation. These results suggest that procrastination and impulsivity are linked primarily through genetic influences on the ability to use their high-priority goals effectively to regulate their action. PMID:24705635

Impulsivity makes more susceptible to overeating after contextual appetitive conditioning.

PubMed

van den Akker, Karolien; Jansen, Anita; Frentz, Florentine; Havermans, Remco C

2013-11-01

Animals can learn that specific contexts are associated with important biological events such as food intake through classical conditioning. Very few studies suggest this is also possible in humans and contextual appetitive conditioning might even be a main determinant of habitual overeating in vulnerable humans. A Virtual Reality laboratory was used to test whether humans show conditioned responding (increased food desires and expectations, increased salivation and increased food intake) to a specific context after repeated pairings of this context with intake. It was also examined whether the personality trait impulsivity strengthens this contextual appetitive conditioning. Conditioned context-induced reactivity was indeed demonstrated and impulsivity predicted increased intake in only the intake-associated context. It is concluded that humans easily learn desires to eat in intake-related environments. The data also suggest that in particular more impulsive people are vulnerable for conditioned context-induced overeating. This relatively easy learning of associations between specific contexts and intake might stimulate habitual overeating and contribute to increased obesity prevalence. Copyright © 2013 Elsevier Ltd. All rights reserved.

Impulsivity in the supermarket. Responses to calorie taxes and subsidies in healthy weight undergraduates.

PubMed

Giesen, Janneke C A H; Havermans, Remco C; Nederkoorn, Chantal; Jansen, Anita

2012-02-01

The present study investigated the effect of taxing high-energy dense products and subsidizing low-energy dense products on changes in calorie consumption. More specifically, we hypothesized that 'more impulsive' individuals were less influenced by such pricing strategies compared to 'less impulsive' individuals. Contrary to our hypothesis, results showed that 'more impulsive' individuals adjusted their calorie consumption with regard to price changes whereas 'less impulsive' participants were less influenced by price changes. Furthermore, taxing high-energy dense products was more successful in reducing calorie consumption than subsidizing low-energy dense products. Copyright © 2011 Elsevier Ltd. All rights reserved.

Advantage of impulse oscillometry over spirometry to diagnose chronic obstructive pulmonary disease and monitor pulmonary responses to bronchodilators: An observational study.

PubMed

Saadeh, Constantine; Saadeh, Charles; Cross, Blake; Gaylor, Michael; Griffith, Melissa

2015-01-01

This retrospective study was a comparative analysis of sensitivity of impulse oscillometry and spirometry techniques for use in a mixed chronic obstructive pulmonary disease group for assessing disease severity and inhalation therapy. A total of 30 patients with mild-to-moderate chronic obstructive pulmonary disease were monitored by impulse oscillometry, followed by spirometry. Lung function was measured at baseline after bronchodilation and at follow-up (3-18 months). The impulse oscillometry parameters were resistance in the small and large airways at 5 Hz (R5), resistance in the large airways at 15 Hz (R15), and lung reactance (area under the curve X; AX). After the bronchodilator therapy, forced expiratory volume in 1 second (FEV1) readings evaluated by spirometry were unaffected at baseline and at follow-up, while impulse oscillometry detected an immediate improvement in lung function, in terms of AX (p = 0.043). All impulse oscillometry parameters significantly improved at follow-up, with a decrease in AX by 37% (p = 0.0008), R5 by 20% (p = 0.0011), and R15 by 12% (p = 0.0097). Impulse oscillometry parameters demonstrated greater sensitivity compared with spirometry for monitoring reversibility of airway obstruction and the effect of maintenance therapy. Impulse oscillometry may facilitate early treatment dose optimization and personalized medicine for chronic obstructive pulmonary disease patients.

Hybrid rocket propulsion

NASA Technical Reports Server (NTRS)

Holzman, Allen L.

1993-01-01

Topics addressed are: (1) comparison of the theoretical impulses; (2) comparison of the density-specific impulses; (3) general propulsion system features comparison; (4) hybrid systems, booster applications; and (5) hybrid systems, upper stage propulsion applications.

Status of 30 cm mercury ion thruster development

NASA Technical Reports Server (NTRS)

Sovey, J. S.; King, H. J.

1974-01-01

Two engineering model 30-cm ion thrusters were assembled, calibrated, and qualification tested. This paper discusses the thruster design, performance, and power system. Test results include documentation of thrust losses due to doubly charged mercury ions and beam divergence by both direct thrust measurements and beam probes. Diagnostic vibration tests have led to improved designs of the thruster backplate structure, feed system, and harness. Thruster durability is being demonstrated over a thrust range of 97 to 113 mN at a specific impulse of about 2900 seconds. As of August 15, 1974, the thruster has successfully operated for over 4000 hours.

Fusion Propulsion and Power for Future Flight

NASA Technical Reports Server (NTRS)

Froning, H. D., Jr.

1996-01-01

There are innovative magnetic and electric confinement fusion power and propulsion system designs with potential for: vacuum specific impulses of 1500-2000 seconds with rocket engine thrust/mass ratios of 5-10 g's; environmentally favorable exhaust emissions if aneutronic fusion propellants can be used; a 2 to 3-fold reduction in the mass of hypersonic airliners and SSTO aerospace planes; a 10 to 20 fold reduction in Mars expedition mass and cost (if propellant from planetary atmospheres is used); and feasibility or in-feasibility of these systems could be confirmed with a modest applied research and exploratory development cost.

A north-south stationkeeping ion thruster system for ATS-F.

NASA Technical Reports Server (NTRS)

Worlock, R.; James, E.; Ramsey, W.; Trump, G.; Gant, G.; Jan, L.; Bartlett, R.

1972-01-01

An ion thruster system is being developed for the ATS-F satellite to demonstrate the application of ion thruster technology to the synchronous satellite north-south stationkeeping mission. The cesium bombardment ion thruster develops one millipound thrust at 2600 seconds specific impulse and provides thrust vectoring by accelerator electrode displacement. The propellant system is sized for two years operation at 25 percent duty cycle. Power conditioning circuitry is based on transistor inverters switching at 10 kHz. Thirteen command channels allow flexibility in operation; 12 telemetry channels provide information on system performance. Input power is less than 150 watts.

Are executive function and impulsivity antipodes? A conceptual reconstruction with special reference to addiction

PubMed Central

Bickel, Warren K.; Jarmolowicz, David P.; Mueller, E. Terry; Gatchalian, Kirstin M.; McClure, Samuel M.

2014-01-01

Rationale Although there is considerable interest in how either executive function (EF) or impulsivity relate to addiction, there is little apparent overlap between these research areas. Objectives The present paper aims to determine if components of these two constructs are conceptual antipodes—widely separated on a shared continuum. Methods EFs and impulsivities were compared and contrasted. Specifically, the definitions of the components of EF and impulsivity, the methods used to measure the various components, the populations of drug users that show deficits in these components, and the neural substrates of these components were compared and contrasted. Results Each component of impulsivity had an antipode in EF. EF, however, covered a wider range of phenomena, including compulsivity. Conclusions Impulsivity functions as an antipode of certain components of EF. Recognition of the relationship between EF and impulsivity may inform the scientific inquiry of behavioral problems such as addiction. Other theoretical implications are discussed. PMID:22441659

Impulse noise generator--design and operation.

PubMed

Brinkmann, H

1991-01-01

In the seventies PFANDER (Pfander, 1975) proposed a screening test with an impulse noise simulator to check the particular responsivity of soldiers on vulnerability of the inner ear concerning the impulse noise-induced hearing loss. According to a system developed at the University of Oldenburg (Germany) (Klug & Radek, 1987), we have constructed an impulse noise generator designed for our specific requirements that will be presented. The simulator consists of an electrical ignited impulse noise spark gap which is supplied by a 3.5 kV high voltage source. At a distance of 1.10 m from the center of the impulse noise spark gap a peak pressure level of 155 dB with a C-Duration (Pfander, 1975) of .2 msec and with the main energy in the frequency range from 1 kHz to 2 kHz was good reproducible. It would be preferable to shift the impulse noise spectrum to lower frequencies but experimental effort has failed so far.

Reconsidering the link between impulsivity and suicidal behavior.

PubMed

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

2014-11-01

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. © 2014 by the Society for Personality and Social Psychology, Inc.

Diet-induced impulsivity: Effects of a high-fat and a high-sugar diet on impulsive choice in rats

PubMed Central

Pirkle, Jesseca R. A.; Kirkpatrick, Kimberly

2017-01-01

Impulsive choice is a common charactertistic among individuals with gambling problems, obesity, and substance abuse issues. Impulsive choice has been classified as a trans-disease process, and understanding the etiology of trait impulsivity could help to understand how diseases and disorders related to impulsive choice are manifested. The Western diet is a possible catalyst of impulsive choice as individuals who are obese and who eat diets high in fat and sugar are typically more impulsive. However, such correlational evidence is unable to discern the direction and causal nature of the relationship. The present study sought to determine how diet may directly contribute to impulsive choice. After 8 weeks of dietary exposure (high-fat, high-sugar, chow), the rats were tested on an impulsive choice task, which presented choices between a smaller-sooner reward (SS) and a larger-later reward (LL). Then, the rats were transferred to a chow diet and retested on the impulsive choice task. The high-sugar and high-fat groups made significantly more impulsive choices than the chow group. Both groups became more self-controlled when they were off the diet, but there were some residual effects of the diet on choice behavior. These results suggest that diet, specifically one high in processed fat or sugar, induces impulsive choice. This diet-induced impulsivity could be a precursor to other disorders that are characterized by impulsivity, such as diet-induced obesity, and could offer potential understanding of the trans-disease nature of impulsive choice. PMID:28662133

Diet-induced impulsivity: Effects of a high-fat and a high-sugar diet on impulsive choice in rats.

PubMed

Steele, Catherine C; Pirkle, Jesseca R A; Kirkpatrick, Kimberly

2017-01-01

Impulsive choice is a common charactertistic among individuals with gambling problems, obesity, and substance abuse issues. Impulsive choice has been classified as a trans-disease process, and understanding the etiology of trait impulsivity could help to understand how diseases and disorders related to impulsive choice are manifested. The Western diet is a possible catalyst of impulsive choice as individuals who are obese and who eat diets high in fat and sugar are typically more impulsive. However, such correlational evidence is unable to discern the direction and causal nature of the relationship. The present study sought to determine how diet may directly contribute to impulsive choice. After 8 weeks of dietary exposure (high-fat, high-sugar, chow), the rats were tested on an impulsive choice task, which presented choices between a smaller-sooner reward (SS) and a larger-later reward (LL). Then, the rats were transferred to a chow diet and retested on the impulsive choice task. The high-sugar and high-fat groups made significantly more impulsive choices than the chow group. Both groups became more self-controlled when they were off the diet, but there were some residual effects of the diet on choice behavior. These results suggest that diet, specifically one high in processed fat or sugar, induces impulsive choice. This diet-induced impulsivity could be a precursor to other disorders that are characterized by impulsivity, such as diet-induced obesity, and could offer potential understanding of the trans-disease nature of impulsive choice.

Serotonin receptor, SERT mRNA and correlations with symptoms in males with alcohol dependence and suicide.

PubMed

Thompson, P M; Cruz, D A; Olukotun, D Y; Delgado, P L

2012-09-01

This study tested the hypothesis that abnormalities in components of the serotonin (5HT) system in the prefrontal cortex are associated with suicide in alcohol-dependent subjects. Second, we assessed the relationship of lifetime impulsivity and mood symptoms with prefrontal cortex 5-HT measures. Tissue was obtained from Brodmann's areas (BA) 9 and 24 in postmortem samples of individuals who were alcohol dependent with suicide (n = 5), alcohol dependent without suicide (n = 9) and normal controls (n = 5). Serotonin receptor (5HT) and serotonin reuptake transporter (SERT) mRNA were measured. Interviews with next of kin estimated lifetime impulsivity and mood symptoms in the last week of life. Serotonin receptor 1A (5HT1A) mRNA in BA 9 was elevated in the alcohol dependence without suicide group compared with controls. In the alcohol dependence with suicide group, anxiety symptoms were associated with decreased BA 24 SERT mRNA and depressive symptoms with BA 9 5HT1A mRNA expression. In the alcohol dependent only group impulsivity is correlated with increased BA 9, and BA 24 serotonin receptor 2A mRNA. Our data suggest region-specific change, rather than global serotonin blunting is involved in alcohol dependence and suicide. It also suggests that symptoms are differentially influenced by prefrontal cortex serotonin receptor mRNA levels. © 2011 John Wiley & Sons A/S.

Impulsivity and the Modular Organization of Resting-State Neural Networks

PubMed Central

Davis, F. Caroline; Knodt, Annchen R.; Sporns, Olaf; Lahey, Benjamin B.; Zald, David H.; Brigidi, Bart D.; Hariri, Ahmad R.

2013-01-01

Impulsivity is a complex trait associated with a range of maladaptive behaviors, including many forms of psychopathology. Previous research has implicated multiple neural circuits and neurotransmitter systems in impulsive behavior, but the relationship between impulsivity and organization of whole-brain networks has not yet been explored. Using graph theory analyses, we characterized the relationship between impulsivity and the functional segregation (“modularity”) of the whole-brain network architecture derived from resting-state functional magnetic resonance imaging (fMRI) data. These analyses revealed remarkable differences in network organization across the impulsivity spectrum. Specifically, in highly impulsive individuals, regulatory structures including medial and lateral regions of the prefrontal cortex were isolated from subcortical structures associated with appetitive drive, whereas these brain areas clustered together within the same module in less impulsive individuals. Further exploration of the modular organization of whole-brain networks revealed novel shifts in the functional connectivity between visual, sensorimotor, cortical, and subcortical structures across the impulsivity spectrum. The current findings highlight the utility of graph theory analyses of resting-state fMRI data in furthering our understanding of the neurobiological architecture of complex behaviors. PMID:22645253

Posttraumatic Stress Disorder's Underlying Dimensions and Their Relation With Impulsivity Facets.

PubMed

Contractor, Ateka A; Armour, Cherie; Forbes, David; Elhai, Jon D

2016-01-01

Research indicates a significant relationship between posttraumatic stress disorder (PTSD) and impulsivity (Kotler, Julian, Efront, and Amir, J Nerv Ment Dis 189:162-167, 2001; Ledgerwood and Petry, J Trauma Stress 19:411-416, 2006). The present study assessed relations between PTSD symptom clusters and impulsivity subscales in an effort to assess the specific impulsivity component most related to PTSD's alterations in arousal/reactivity and alterations in mood/cognitions symptoms. In the current study, the PTSD Checklist for Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, and the UPPS Impulsivity Scale were administered to a sample of 412 nonclinical subjects with a trauma history. Results indicated that PTSD's alterations in arousal/reactivity and mood/cognition factors were most related to impulsivity's sensation-seeking tendency compared with other impulsivity components. Results highlight the importance of assessing and addressing (1) sensation-seeking tendencies and (2) urges to act impulsively when experiencing negative affect in trauma treatment. Furthermore, it is possible that sensation-seeking tendencies are primarily driving the comorbidity between PTSD and certain impulsive behaviors.

A History of Welding on the Space Shuttle Main Engine (1975 to 2010)

NASA Technical Reports Server (NTRS)

Zimmerman, Frank R.; Russell, Carolyn K.

2010-01-01

The Space Shuttle Main Engine (SSME) is a high performance, throttleable, liquid hydrogen fueled rocket engine. High thrust and specific impulse (Isp) are achieved through a staged combustion engine cycle, combined with high combustion pressure (approx.3000psi) generated by the two-stage pump and combustion process. The SSME is continuously throttleable from 67% to 109% of design thrust level. The design criteria for this engine maximize performance and weight, resulting in a 7,800 pound rocket engine that produces over a half million pounds of thrust in vacuum with a specific impulse of 452/sec. It is the most reliable rocket engine in the world, accumulating over one million seconds of hot-fire time and achieving 100% flight success in the Space Shuttle program. A rocket engine with the unique combination of high reliability, performance, and reusability comes at the expense of manufacturing simplicity. Several innovative design features and fabrication techniques are unique to this engine. This is as true for welding as any other manufacturing process. For many of the weld joints it seemed mean cheating physics and metallurgy to meet the requirements. This paper will present a history of the welding used to produce the world s highest performance throttleable rocket engine.

Analysis of a Rocket Based Combined Cycle Engine during Rocket Only Operation

NASA Technical Reports Server (NTRS)

Smith, T. D.; Steffen, C. J., Jr.; Yungster, S.; Keller, D. J.

1998-01-01

The all rocket mode of operation is a critical factor in the overall performance of a rocket based combined cycle (RBCC) vehicle. However, outside of performing experiments or a full three dimensional analysis, there are no first order parametric models to estimate performance. As a result, an axisymmetric RBCC engine was used to analytically determine specific impulse efficiency values based upon both full flow and gas generator configurations. Design of experiments methodology was used to construct a test matrix and statistical regression analysis was used to build parametric models. The main parameters investigated in this study were: rocket chamber pressure, rocket exit area ratio, percent of injected secondary flow, mixer-ejector inlet area, mixer-ejector area ratio, and mixer-ejector length-to-inject diameter ratio. A perfect gas computational fluid dynamics analysis was performed to obtain values of vacuum specific impulse. Statistical regression analysis was performed based on both full flow and gas generator engine cycles. Results were also found to be dependent upon the entire cycle assumptions. The statistical regression analysis determined that there were five significant linear effects, six interactions, and one second-order effect. Two parametric models were created to provide performance assessments of an RBCC engine in the all rocket mode of operation.

Hepatic and Splenic Acoustic Radiation Force Impulse Shear Wave Velocity Elastography in Children with Liver Disease Associated with Cystic Fibrosis

PubMed Central

Cañas, Teresa; Maciá, Araceli; Muñoz-Codoceo, Rosa Ana; Fontanilla, Teresa; González-Rios, Patricia; Miralles, María; Gómez-Mardones, Gloria

2015-01-01

Background. Liver disease associated with cystic fibrosis (CFLD) is the second cause of mortality in these patients. The diagnosis is difficult because none of the available tests are specific enough. Noninvasive elastographic techniques have been proven to be useful to diagnose hepatic fibrosis. Acoustic radiation force impulse (ARFI) imaging is an elastography imaging system. The purpose of the work was to study the utility of liver and spleen ARFI Imaging in the detection of CFLD. Method. 72 patients with cystic fibrosis (CF) were studied and received ARFI imaging in the liver and in the spleen. SWV values were compared with the values of 60 healthy controls. Results. Comparing the SWV values of CFLD with the control healthy group, values in the right lobe were higher in patients with CFLD. We found a SWV RHL cut-off value to detect CFLD of 1.27 m/s with a sensitivity of 56.5% and a specificity of 90.5%. CF patients were found to have higher SWC spleen values than the control group. Conclusions. ARFI shear wave elastography in the right hepatic lobe is a noninvasive technique useful to detect CFLD in our sample of patients. Splenic SWV values are higher in CF patients, without any clinical consequence. PMID:26609528

Hepatic and Splenic Acoustic Radiation Force Impulse Shear Wave Velocity Elastography in Children with Liver Disease Associated with Cystic Fibrosis.

PubMed

Cañas, Teresa; Maciá, Araceli; Muñoz-Codoceo, Rosa Ana; Fontanilla, Teresa; González-Rios, Patricia; Miralles, María; Gómez-Mardones, Gloria

2015-01-01

Liver disease associated with cystic fibrosis (CFLD) is the second cause of mortality in these patients. The diagnosis is difficult because none of the available tests are specific enough. Noninvasive elastographic techniques have been proven to be useful to diagnose hepatic fibrosis. Acoustic radiation force impulse (ARFI) imaging is an elastography imaging system. The purpose of the work was to study the utility of liver and spleen ARFI Imaging in the detection of CFLD. Method. 72 patients with cystic fibrosis (CF) were studied and received ARFI imaging in the liver and in the spleen. SWV values were compared with the values of 60 healthy controls. Results. Comparing the SWV values of CFLD with the control healthy group, values in the right lobe were higher in patients with CFLD. We found a SWV RHL cut-off value to detect CFLD of 1.27 m/s with a sensitivity of 56.5% and a specificity of 90.5%. CF patients were found to have higher SWC spleen values than the control group. Conclusions. ARFI shear wave elastography in the right hepatic lobe is a noninvasive technique useful to detect CFLD in our sample of patients. Splenic SWV values are higher in CF patients, without any clinical consequence.

Childhood impulsive behavior and problem gambling by adulthood: A 30-year prospective community-based study

PubMed Central

Shenassa, Edmond D.; Paradis, Angela D.; Dolan, Sara L.; Wilhelm, Charlotte S.; Buka, Stephen L.

2015-01-01

Aims Problem gambling can create major financial, emotional and sometimes criminal problems for an individual. This study prospectively investigated the association between impulsive behavior at age 7 and the development of lifetime problem gambling by adulthood. We also examined the specificity of any observed association between impulsive behaviors and problem gambling by conducting parallel analyses examining the link between respondents’ shy/depressed behavior in childhood and later problem gambling. Design, setting and participants Cohort study of 958 offspring of mothers enrolled in the Collaborative Perinatal Project who participated in an adult follow-up study at a mean age of 39 years. Measurements Multivariable logistic regression models were fit to determine associations between psychologist-rated impulsive and shy/depressed behaviors at age 7 and lifetime self-reported gambling as measured by the South Oaks Gambling Screen administered during the adult follow-up study. Findings Children who exhibited impulsive behaviors at age 7, compared to their non-impulsive counterparts, were 3.09 (95% confidence interval: 1.40–6.82) times as likely to report problem gambling years later. In contrast, we did not find a significant association between childhood shy/depressed behavior and problem gambling by adulthood in adjusted analyses. Conclusions Impulsive behaviors at age 7 are a specific and significant risk factor for later problem gambling.. PMID:21752146

Magnetic Flux Compression Concept for Aerospace Propulsion and Power

NASA Technical Reports Server (NTRS)

Litchford, Ron J.; Robertson, Tony; Hawk, Clark W.; Turner, Matt; Koelfgen, Syri

2000-01-01

The objective of this research is to investigate system level performance and design issues associated with magnetic flux compression devices for aerospace power generation and propulsion. The proposed concept incorporates the principles of magnetic flux compression for direct conversion of nuclear/chemical detonation energy into electrical power. Specifically a magnetic field is compressed between an expanding detonation driven diamagnetic plasma and a stator structure formed from a high temperature superconductor (HTSC). The expanding plasma cloud is entirely confined by the compressed magnetic field at the expense of internal kinetic energy. Electrical power is inductively extracted, and the detonation products are collimated and expelled through a magnetic nozzle. The long-term development of this highly integrated generator/propulsion system opens up revolutionary NASA Mission scenarios for future interplanetary and interstellar spacecraft. The unique features of this concept with respect to future space travel opportunities are as follows: ability to implement high energy density chemical detonations or ICF microfusion bursts as the impulsive diamagnetic plasma source; high power density system characteristics constrain the size, weight, and cost of the vehicle architecture; provides inductive storage pulse power with a very short pulse rise time; multimegajoule energy bursts/terawatt power bursts; compact pulse power driver for low-impedance dense plasma devices; utilization of low cost HTSC material and casting technology to increase magnetic flux conservation and inductive energy storage; improvement in chemical/nuclear-to-electric energy conversion efficiency and the ability to generate significant levels of thrust with very high specific impulse; potential for developing a small, lightweight, low cost, self-excited integrated propulsion and power system suitable for space stations, planetary bases, and interplanetary and interstellar space travel; potential for attaining specific impulses approaching 10 (exp 6) seconds, which would enable missions to the outer planets within ten years and missions at interstellar distances within fifty years.

Diagnosis and treatment of impulse control disorders in patients with movement disorders.

PubMed

Mestre, Tiago A; Strafella, Antonio P; Thomsen, Teri; Voon, Valerie; Miyasaki, Janis

2013-05-01

Impulse control disorders are a psychiatric condition characterized by the failure to resist an impulsive act or behavior that may be harmful to self or others. In movement disorders, impulse control disorders are associated with dopaminergic treatment, notably dopamine agonists (DAs). Impulse control disorders have been studied extensively in Parkinson's disease, but are also recognized in restless leg syndrome and atypical Parkinsonian syndromes. Epidemiological studies suggest younger age, male sex, greater novelty seeking, impulsivity, depression and premorbid impulse control disorders as the most consistent risk factors. Such patients may warrant special monitoring after starting treatment with a DA. Various individual screening tools are available for people without Parkinson's disease. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease has been developed specifically for Parkinson's disease. The best treatment for impulse control disorders is prevention. However, after the development of impulse control disorders, the mainstay intervention is to reduce or discontinue the offending anti-Parkinsonian medication. In refractory cases, other pharmacological interventions are available, including neuroleptics, antiepileptics, amantadine, antiandrogens, lithium and opioid antagonists. Unfortunately, their use is only supported by case reports, small case series or open-label clinical studies. Prospective, controlled studies are warranted. Ongoing investigations include naltrexone and nicotine.

Some neuroanatomical insights to impulsive aggression in schizophrenia.

PubMed

Leclerc, Marcel P; Regenbogen, Christina; Hamilton, Roy H; Habel, Ute

2018-06-13

Patients with schizophrenia are at increased risk of engaging in violence towards others, compared to both the general population and most other patient groups. We have here explored the role of cortico-limbic impairments in schizophrenia, and have considered these brain regions specifically within the framework of a popular neuroanatomical model of impulsive aggression. In line with this model, evidence in patients with aggressive schizophrenia implicated structural deficits associated with impaired decision-making, emotional control and evaluation, and social information processing, especially in the orbitofrontal and ventrolateral prefrontal cortex. Given the pivotal role of the orbitofrontal and ventrolateral cortex in emotion control and evaluation, structural deficits may result in inappropriate use of socially relevant information and improper recognition of impulses that are in need for regulation. Furthermore, we have extended the original model and incorporated the striatum, important for the generation of aggressive impulses, as well as the hippocampus, a region critical for decision-making, into the model. Lastly, we discuss the question whether structural impairments are specific to aggressive schizophrenia. Our results suggest, that similar findings can be observed in other aggressive patient populations, making the observed impairments non-specific to aggressive schizophrenia. This points towards a shared condition, across pathologies, a potential common denominator being impulsive aggression. Copyright © 2018. Published by Elsevier B.V.

Limbic striatal dopamine D2/3 receptor availability is associated with non-planning impulsivity in healthy adults after exclusion of potential dissimulators.

PubMed

Reeves, Suzanne J; Polling, Catherine; Stokes, Paul R A; Lappin, Julia M; Shotbolt, Paul P; Mehta, Mitul A; Howes, Oliver D; Egerton, Alice

2012-04-30

Positron emission tomography (PET) studies have reported an association between reduced striatal dopamine D2/3 receptor availability and higher scores on self-report measures of trait impulsivity in healthy adults. However, impulsivity is a multi-faceted construct, and it is unclear which aspect(s) of impulsivity might be driving these associations. The current study aimed to investigate the relationship between limbic (ventral) striatal D2/3 receptor availability and individual components of impulsivity (attentional, motor and non-planning) using the Barratt Impulsiveness Scale (BIS-11) and [(11)C]raclopride PET in 23 healthy volunteers. A partial correlational analysis showed a significant association between non-planning impulsiveness (lack of forethought or 'futuring') and limbic D2/3 receptor availability, which was only apparent after the exclusion of potential dissimulators (indexed by high scores on impression management). Our findings suggest that non-planning impulsiveness is associated with individual variation in limbic striatal D2/3 receptor availability and that different facets of impulsivity may have specific neurochemical correlates. Future studies that combine D2/3 receptor imaging with behavioral measures of impulsivity are required to further elucidate the precise relationship between individual components of trait impulsivity and brain dopaminergic function. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Optimal neurocognitive, personality and behavioral measures for assessing impulsivity in cocaine dependence.

PubMed

LoBue, Christian; Cullum, C Munro; Braud, Jacqueline; Walker, Robrina; Winhusen, Theresa; Suderajan, Prabha; Adinoff, Bryon

2014-11-01

Impulsivity may underlie the poor treatment retention and high relapse rates observed in cocaine-dependent persons. However, observed differences in measures of impulsivity between cocaine-dependent and healthy control participants often do not reach clinical significance, suggesting that the clinical relevance of these differences may be limited. To examine which measures of impulsivity (i.e. self-report impulsivity, self-report personality, neurocognitive testing) best distinguish cocaine-dependent and healthy control participants (i.e. showing differences at least 1.5 standard deviations [SD] from controls). Optimal measures were considered to demonstrate sufficient classification accuracy. Sixty-five recently abstinent cocaine-dependent and 25 healthy control participants were assessed using select neurocognitive tests and self-report questionnaires including the NEO Personality Inventory-Revised (NEO-PI-R), Temperament and Character Inventory (TCI), Barratt Impulsiveness Scale (BIS-11a), and the Frontal Systems Behavior Scale (FrSBe). When corrected for years of education and gender, neurocognitive measures did not demonstrate clinically significant differences between cocaine-dependent and control participants. The personality measures TCI Purposefulness and Congruent Second Nature and NEO-PI-R Impulsiveness, and the self-rating measures FrSBe Disinhibition and BIS-11 Motor Impulsivity and Total successfully identified clinically meaningful elevations in impulsivity within cocaine-dependent participants (>1.5 SDs from controls). Furthermore, these measures achieved 84-93% accuracy in discriminating cocaine-dependent from control participants. Clinically significant neurocognitive impairment in cocaine-dependent participants was not observed in this sample. As the BIS-11 or FrSBe are brief to administer, accurate, and have been shown to predict treatment retention and relapse, these measures appear to be optimal, relative to the personality measures, for examining trait impulsivity in cocaine dependence.

Optimal neurocognitive, personality and behavioral measures for assessing impulsivity in cocaine dependence

PubMed Central

LoBue, Christian; Cullum, C. Munro; Braud, Jacqueline; Walker, Robrina; Winhusen, Theresa; Suderajan, Prabha; Adinoff, Bryon

2015-01-01

Background Impulsivity may underlie the poor treatment retention and high relapse rates observed in cocaine-dependent persons. However, observed differences in measures of impulsivity between cocaine-dependent and healthy control participants often do not reach clinical significance, suggesting that the clinical relevance of these differences may be limited. Objectives To examine which measures of impulsivity (i.e. self-report impulsivity, self-report personality, neurocognitive testing) best distinguish cocaine-dependent and healthy control participants (i.e. showing differences at least 1.5 standard deviations [SD] from controls). Optimal measures were considered to demonstrate sufficient classification accuracy. Methods Sixty-five recently abstinent cocaine-dependent and 25 healthy control participants were assessed using select neurocognitive tests and self-report questionnaires including the NEO Personality Inventory-Revised (NEO-PI-R), Temperament and Character Inventory (TCI), Barratt Impulsiveness Scale (BIS-11a), and the Frontal Systems Behavior Scale (FrSBe). Results When corrected for years of education and gender, neurocognitive measures did not demonstrate clinically significant differences between cocaine-dependent and control participants. The personality measures TCI Purposefulness and Congruent Second Nature and NEO-PI-R Impulsiveness, and the self-rating measures FrSBe Disinhibition and BIS-11 Motor Impulsivity and Total successfully identified clinically meaningful elevations in impulsivity within cocaine-dependent participants (>1.5 SDs from controls). Furthermore, these measures achieved 84–93% accuracy in discriminating cocaine-dependent from control participants. Conclusion Clinically significant neurocognitive impairment in cocaine-dependent participants was not observed in this sample. As the BIS-11 or FrSBe are brief to administer, accurate, and have been shown to predict treatment retention and relapse, these measures appear to be optimal, relative to the personality measures, for examining trait impulsivity in cocaine dependence. PMID:25083938

Individual in Context: The Role of Impulse Control on the Association between the Home, School, and Neighborhood Developmental Contexts and Adolescent Delinquency.

PubMed

Fine, Adam; Mahler, Alissa; Steinberg, Laurence; Frick, Paul J; Cauffman, Elizabeth

2017-07-01

Social ecological theories and decades of supporting research suggest that contexts exert a powerful influence on adolescent delinquency. Individual traits, such as impulse control, also pose a developmental disadvantage to adolescents through increasing risk of delinquency. However, such individual differences may also predispose some youth to struggle more in adverse environments, but also to excel in enriched environments. Despite the prominence of impulse control in both developmental and criminological literatures, researchers are only beginning to consider impulse control as an individual characteristic that may affect developmental outcomes in response to environmental input. Using a racially diverse (Latino 46 %; Black 37 %; White 15 %; other race 2 %) sample of 1,216 first-time, male, juvenile offenders from the longitudinal Crossroads Study, this study examined key interactions between baseline impulse control and the home, school, and neighborhood contexts in relation to delinquency within the following 6 months. The results indicated that even after accounting for prior delinquency, youth in more negative home, school, and neighborhood contexts engaged in the same amount of delinquency in the following 6 months regardless of their level of impulse control. However, the effects of positive home, school, and neighborhood contexts on delinquency were stronger for youth with moderate or high impulse control and minimally affected youth with low impulse control. The findings suggest two risk factors for delinquency: low impulse control as a dispositional vulnerability that operates independently of developmental context, and a second that results from a contextual vulnerability.

Relationships between impulsivity, anxiety, and risk-taking and neural correlates of attention in adolescents

PubMed Central

Elsey, James W. B.; Crowley, Michael J.; Mencl, W. Einar; Lacadie, Cheryl M.; Mayes, Linda C.; Potenza, Marc N.

2016-01-01

Although impulsivity, anxiety, and risk-taking may relate to attentional processes, little research has directly investigated how each may be associated with specific facets of attentional processes and their underlying neural correlates. Nineteen adolescents performed an fMRI task involving simple, selective and divided attention. Out-of-scanner-assessed impulsivity, anxiety and risk-taking scores were not correlated with each other and showed task-phase-specific patterns of association. Results are discussed in light of research and theory suggesting a relationship between these domains and attention and may serve to focus future research aiming to understand these relationships. PMID:27135550

Self-reported impulsivity, but not behavioral choice or response impulsivity, partially mediates the effect of stress on drinking behavior

PubMed Central

HAMILTON, KRISTEN R.; ANSELL, EMILY B.; REYNOLDS, BRADY; POTENZA, MARC N.; SINHA, RAJITA

2013-01-01

Stress and impulsivity contribute to alcohol use, and stress may also act via impulsivity to increase drinking behavior. Impulsivity represents a multi-faceted construct and self-report and behavioral assessments may effectively capture distinct clinically relevant factors. The present research investigated whether aspects of impulsivity mediate the effect of stress on alcohol use. A community-based sample of 192 men and women was assessed on measures of cumulative stress, alcohol use, self-reported impulsivity, and behavioral choice and response impulsivity. Data were analyzed using regression and bootstrapping techniques to estimate indirect effects of stress on drinking via impulsivity. Cumulative adversity exhibited both direct effects and indirect effects (via self-reported impulsivity) on drinking behavior. Additional models examining specific types of stress indicated direct and indirect effects of trauma and recent life events, and indirect effects of major life events and chronic stressors on drinking behavior. Overall, cumulative stress was associated with increased drinking behavior, and this effect was partially mediated by self-reported impulsivity. Self-reported impulsivity also mediated the effects of different types of stress on drinking behavior. These findings highlight the value of mediation models to examine the pathways through which different types of stress increase drinking behavior. Treatment and prevention strategies should focus on enhancing stress management and self-control. PMID:22376044

Self-reported impulsivity, but not behavioral choice or response impulsivity, partially mediates the effect of stress on drinking behavior.

PubMed

Hamilton, Kristen R; Ansell, Emily B; Reynolds, Brady; Potenza, Marc N; Sinha, Rajita

2013-01-01

Stress and impulsivity contribute to alcohol use, and stress may also act via impulsivity to increase drinking behavior. Impulsivity represents a multi-faceted construct and self-report and behavioral assessments may effectively capture distinct clinically relevant factors. The present research investigated whether aspects of impulsivity mediate the effect of stress on alcohol use. A community-based sample of 192 men and women was assessed on measures of cumulative stress, alcohol use, self-reported impulsivity, and behavioral choice and response impulsivity. Data were analyzed using regression and bootstrapping techniques to estimate indirect effects of stress on drinking via impulsivity. Cumulative adversity exhibited both direct effects and indirect effects (via self-reported impulsivity) on drinking behavior. Additional models examining specific types of stress indicated direct and indirect effects of trauma and recent life events, and indirect effects of major life events and chronic stressors on drinking behavior. Overall, cumulative stress was associated with increased drinking behavior, and this effect was partially mediated by self-reported impulsivity. Self-reported impulsivity also mediated the effects of different types of stress on drinking behavior. These findings highlight the value of mediation models to examine the pathways through which different types of stress increase drinking behavior. Treatment and prevention strategies should focus on enhancing stress management and self-control.

Performance Evaluation of the T6 Ion Engine

NASA Technical Reports Server (NTRS)

Snyder, John Steven; Goebel, Dan M.; Hofer, Richard R.; Polk, James E.; Wallace, Neil C.; Simpson, Huw

2010-01-01

The T6 ion engine is a 22-cm diameter, 4.5-kW Kaufman-type ion thruster produced by QinetiQ, Ltd., and is baselined for the European Space Agency BepiColombo mission to Mercury and is being qualified under ESA sponsorship for the extended range AlphaBus communications satellite platform. The heritage of the T6 includes the T5 ion thruster now successfully operating on the ESA GOCE spacecraft. As a part of the T6 development program, an engineering model thruster was subjected to a suite of performance tests and plume diagnostics at the Jet Propulsion Laboratory. The engine was mounted on a thrust stand and operated over its nominal throttle range of 2.5 to 4.5 kW. In addition to the typical electrical and flow measurements, an E x B mass analyzer, scanning Faraday probe, thrust vector probe, and several near-field probes were utilized. Thrust, beam divergence, double ion content, and thrust vector movement were all measured at four separate throttle points. The engine performance agreed well with published data on this thruster. At full power the T6 produced 143 mN of thrust at a specific impulse of 4120 seconds and an efficiency of 64%; optimization of the neutralizer for lower flow rates increased the specific impulse to 4300 seconds and the efficiency to nearly 66%. Measured beam divergence was less than, and double ion content was greater than, the ring-cusp-design NSTAR thruster that has flown on NASA missions. The measured thrust vector offset depended slightly on throttle level and was found to increase with time as the thruster approached thermal equilibrium.

Can emergency physicians accurately and reliably assess acute vertigo in the emergency department?

PubMed

Vanni, Simone; Nazerian, Peiman; Casati, Carlotta; Moroni, Federico; Risso, Michele; Ottaviani, Maddalena; Pecci, Rudi; Pepe, Giuseppe; Vannucchi, Paolo; Grifoni, Stefano

2015-04-01

To validate a clinical diagnostic tool, used by emergency physicians (EPs), to diagnose the central cause of patients presenting with vertigo, and to determine interrater reliability of this tool. A convenience sample of adult patients presenting to a single academic ED with isolated vertigo (i.e. vertigo without other neurological deficits) was prospectively evaluated with STANDING (SponTAneousNystagmus, Direction, head Impulse test, standiNG) by five trained EPs. The first step focused on the presence of spontaneous nystagmus, the second on the direction of nystagmus, the third on head impulse test and the fourth on gait. The local standard practice, senior audiologist evaluation corroborated by neuroimaging when deemed appropriate, was considered the reference standard. Sensitivity and specificity of STANDING were calculated. On the first 30 patients, inter-observer agreement among EPs was also assessed. Five EPs with limited experience in nystagmus assessment volunteered to participate in the present study enrolling 98 patients. Their average evaluation time was 9.9 ± 2.8 min (range 6-17). Central acute vertigo was suspected in 16 (16.3%) patients. There were 13 true positives, three false positives, 81 true negatives and one false negative, with a high sensitivity (92.9%, 95% CI 70-100%) and specificity (96.4%, 95% CI 93-38%) for central acute vertigo according to senior audiologist evaluation. The Cohen's kappas of the first, second, third and fourth steps of the STANDING were 0.86, 0.93, 0.73 and 0.78, respectively. The whole test showed a good inter-observer agreement (k = 0.76, 95% CI 0.45-1). In the hands of EPs, STANDING showed a good inter-observer agreement and accuracy validated against the local standard of care. © 2015 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine.

Study of monopropellants for electrothermal thrusters

NASA Technical Reports Server (NTRS)

Kuenzly, J. D.

1974-01-01

A 333 mN electrothermal thruster designed to use MIL-grade hydrazine was demonstrated to be suitable for operation with low freezing point monopropellants containing hydrazine azide, monomethylhydrazine, unsymmetrical-dimethylhydrazine and ammonia. The steady-state specific impulse was greater than 200 sec for all propellants. The pulsed-mode specific impulse for an azide blend exceeded 175 sec for pulse widths greater than 50 msec; propellants containing carbonaceous species delivered 175 sec pulsed-mode specific impulses for pulse widths greater than 100 msec. Longer thrust chamber residence times were required for the carbonaceous propellants; the original thruster design was modified by increasing the characteristic chamber length and screen packing density. Specific recommendations were made for the work required to design and develop flight worthy thrusters, including methods to increase propellant dispersal at injection, thruster geometry changes to reduce holding power levels and methods to initiate the rapid decomposition of the carbonaceous propellants.

Penrose junction conditions extended: Impulsive waves with gyratons

NASA Astrophysics Data System (ADS)

Podolský, J.; Švarc, R.; Steinbauer, R.; Sämann, C.

2017-09-01

We generalize the classical junction conditions for constructing impulsive gravitational waves by the Penrose "cut and paste" method. Specifically, we study nonexpanding impulses which propagate in spaces of constant curvature with any value of the cosmological constant (that is, Minkowski, de Sitter, or anti-de Sitter universes) when additional off-diagonal metric components are present. Such components encode a possible angular momentum of the ultrarelativistic source of the impulsive wave—the so-called gyraton. We explicitly derive and analyze a specific transformation that relates the distributional form of the metric to a new form which is (Lipschitz) continuous. Such a transformation automatically implies an extended version of the Penrose junction conditions. It turns out that the conditions for identifying points of the background spacetime across the impulse are the same as in the original Penrose cut and paste construction, but their derivatives now directly represent the influence of the gyraton on the axial motion of test particles. Our results apply both for vacuum and nonvacuum solutions of Einstein's field equations and can also be extended to other theories of gravity.

Impulsivity and reasons for living among African American youth: a risk-protection framework of suicidal ideation.

PubMed

Salami, Temilola K; Brooks, Bianca A; Lamis, Dorian A

2015-05-15

This study aims to explore the impact of specific facets of impulsivity as measured by the UPPS Impulsive Behavior Scale (UPPS), as well as reasons for living in predicting suicidal ideation among African American college-aged students. The incremental validity of each facet of the UPPS interacting with reasons for living, a construct meant to buffer against risk for suicide, was explored in a sample of African American students (N = 130; ages 18-24). Results revealed significant interactions between reasons for living and two factors of impulsivity, (lack of) premeditation and sensation seeking. Higher levels of sensation seeking and lack of premeditation in conjunction with lower reasons for living was associated with increased suicidal ideation. Neither urgency nor (lack of) perseverance significantly interacted with reasons for living in association with suicidal ideation. These results suggest including elements of impulsivity, specifically sensation seeking and (lack of) premeditation, when screening for suicidal ideation among African American youth. Future investigations should continue to integrate factors of both risk and protection when determining risk for suicide.

Impulsivity and Reasons for Living Among African American Youth: A Risk-Protection Framework of Suicidal Ideation

PubMed Central

Salami, Temilola K.; Brooks, Bianca A.; Lamis, Dorian A.

2015-01-01

This study aims to explore the impact of specific facets of impulsivity as measured by the UPPS Impulsive Behavior Scale (UPPS), as well as reasons for living in predicting suicidal ideation among African American college-aged students. The incremental validity of each facet of the UPPS interacting with reasons for living, a construct meant to buffer against risk for suicide, was explored in a sample of African American students (N = 130; ages 18–24). Results revealed significant interactions between reasons for living and two factors of impulsivity, (lack of) premeditation and sensation seeking. Higher levels of sensation seeking and lack of premeditation in conjunction with lower reasons for living was associated with increased suicidal ideation. Neither urgency nor (lack of) perseverance significantly interacted with reasons for living in association with suicidal ideation. These results suggest including elements of impulsivity, specifically sensation seeking and (lack of) premeditation, when screening for suicidal ideation among African American youth. Future investigations should continue to integrate factors of both risk and protection when determining risk for suicide. PMID:25988310

On the Spur of the Moment: Intrinsic Predictors of Impulse Sports Betting.

PubMed

Hing, Nerilee; Li, En; Vitartas, Peter; Russell, Alex M T

2018-06-01

Betting on impulse, without thoughtful consideration, research or informed decision-making, may cause financial and other harms and lead to the development of gambling problems. Impulse betting undermines responsible consumption of gambling because it reflects self-regulatory failure, impaired control, unreflective decision-making and betting more than planned. In this paper we define impulse gambling and report on a study that aimed to understand more about the intrinsic characteristics of sports bettors who have a greater tendency to bet on impulse. Specifically, the study aimed to identify behavioural, psychological and socio-demographic predictors of impulse sports betting. A sample of 1816 Australian sports bettors completed an online survey that measured the proportion of their bets placed on impulse both before and during sporting events, as well as bets that were researched and planned in advance. Impulse betting was common, accounting for nearly one-half of all past-year sports bets by respondents. Over three-quarters of respondents had placed one or more impulse bets in the last year and one in seven respondents had made all of their sports bets on impulse. More impulsive sports bettors were characterised as having higher trait impulsiveness, higher problem gambling severity, more frequent sports betting and a shorter history of sports betting. They favoured betting on in-match contingencies instead of overall match outcomes. While health promotion strategies are needed to discourage impulse betting, research into contextual factors that arouse urges to bet would also provide direction for harm minimisation measures that help consumers to resist impulsive betting decisions.

Impulsive Personality and Alcohol Use: Bidirectional Relations Over One Year

PubMed Central

Kaiser, Alison; Bonsu, Jacqueline A.; Charnigo, Richard J.; Milich, Richard; Lynam, Donald R.

2016-01-01

Objective: Impulsive personality traits have been found to be robust predictors of substance use and problems in both cross-sectional and longitudinal research. Studies examining the relations of substance use and impulsive personality over time indicate a bidirectional relation, where substance use is also predictive of increases in later impulsive personality. The present study sought to build on these findings by examining the bidirectional relations among the different impulsive personality traits assessed by the UPPS-P Impulsive Behavior Scale, with an interest in urgency (the tendency to act rashly when experiencing strong affect). Method: Participants were 525 first-year college students (48.0% male, 81.1% White), who completed self-report measures assessing personality traits and a structured interview assessing past and current substance use. Data collection took place at two different time points: the first occurred during the participants’ first year of college, and the second occurred approximately 1 year later. Bidirectional relations were examined using structural equation modeling. Results: Time 1 (T1) positive urgency predicted higher levels of alcohol use at Time 2 (T2), whereas T1 lack of perseverance predicted lower levels of alcohol use at T2. T1 alcohol use predicted higher levels of positive urgency, negative urgency, sensation seeking, and lack of premeditation at T2. Conclusions: Findings provide greater resolution in characterizing the bidirectional relation between impulsive personality traits and substance use. PMID:27172580

Ultrasonic hydrometer. [Specific gravity of electrolyte

DOEpatents

Swoboda, C.A.

1982-03-09

The disclosed ultrasonic hydrometer determines the specific gravity (density) of the electrolyte of a wet battery, such as a lead-acid battery. The hydrometer utilizes a transducer that when excited emits an ultrasonic impulse that traverses through the electrolyte back and forth between spaced sonic surfaces. The transducer detects the returning impulse, and means measures the time t between the initial and returning impulses. Considering the distance d between the spaced sonic surfaces and the measured time t, the sonic velocity V is calculated with the equation V = 2d/t. The hydrometer also utilizes a thermocouple to measure the electrolyte temperature. A hydrometer database correlates three variable parameters including sonic velocity in and temperature and specific gravity of the electrolyte, for temperature values between 0 and 40/sup 0/C and for specific gravity values between 1.05 and 1.30. Upon knowing two parameters (the calculated sonic velocity and the measured temperature), the third parameter (specific gravity) can be uniquely found in the database. The hydrometer utilizes a microprocessor for data storage and manipulation.

Specific Impulses Losses in Solid Propellant Rockets

DTIC Science & Technology

1974-12-17

binder -- polyvinyl, polyurethane, or polybutadiene) markedly increases performance. Aluminum is the most widely used metal since its energy properties...temperature is also used. -5- The specific impulse values calculated for a typical propellant with 16.4% aluminum are as follows: (p0 70 atm. p - 1 atm...Direct Measurement of Combuction Efficiency of Aluminum Analysis of the condensed phase enables the proportion of unburnt aluminum to be determined

Design of optimal impulse transfers from the Sun-Earth libration point to asteroid

NASA Astrophysics Data System (ADS)

Wang, Yamin; Qiao, Dong; Cui, Pingyuan

2015-07-01

The lunar probe, Chang'E-2, is the first one to successfully achieve both the transfer to Sun-Earth libration point orbit and the flyby of near-Earth asteroid Toutatis. This paper, taking the Chang'E-2's asteroid flyby mission as an example, provides a method to design low-energy transfers from the libration point orbit to an asteroid. The method includes the analysis of transfer families and the design of optimal impulse transfers. Firstly, the one-impulse transfers are constructed by correcting the initial guesses, which are obtained by perturbing in the direction of unstable eigenvector. Secondly, the optimality of one-impulse transfers is analyzed and the optimal impulse transfers are built by using the primer vector theory. After optimization, the transfer families, including the slow and the fast transfers, are refined to be continuous and lower-cost transfers. The method proposed in this paper can be also used for designing transfers from an arbitrary Sun-Earth libration point orbit to a near-Earth asteroid in the Sun-Earth-Moon system.

Modification of Impulse Generation During Pirouette Turns With Increased Rotational Demands.

PubMed

Zaferiou, Antonia M; Wilcox, Rand R; McNitt-Gray, Jill L

2016-10-01

This study determined how dancers regulated angular and linear impulse during the initiation of pirouettes of increased rotation. Skilled dancers (n = 11) performed single and double pirouette turns with each foot supported by a force plate. Linear and angular impulses generated by each leg were quantified and compared between turn types using probability-based statistical methods. As rotational demands increased, dancers increased the net angular impulse generated. The contribution of each leg to net angular impulse in both single and double pirouettes was influenced by stance configuration strategies. Dancers who generated more angular impulse with the push leg than with the turn leg initiated the turn with the center of mass positioned closer to the turn leg than did other dancers. As rotational demands increased, dancers tended to increase the horizontal reaction force magnitude at one or both feet; however, they used subject-specific mechanisms. By coordinating the generation of reaction forces between legs, changes in net horizontal impulse remained minimal, despite impulse regulation at each leg used to achieve more rotations. Knowledge gained regarding how an individual coordinates the generation of linear and angular impulse between both legs as rotational demand increased can help design tools to improve that individual's performance.

Diagnosis and treatment of impulse control disorders in patients with movement disorders

PubMed Central

Mestre, Tiago A.; Strafella, Antonio P.; Thomsen, Teri; Voon, Valerie

2013-01-01

Impulse control disorders are a psychiatric condition characterized by the failure to resist an impulsive act or behavior that may be harmful to self or others. In movement disorders, impulse control disorders are associated with dopaminergic treatment, notably dopamine agonists (DAs). Impulse control disorders have been studied extensively in Parkinson’s disease, but are also recognized in restless leg syndrome and atypical Parkinsonian syndromes. Epidemiological studies suggest younger age, male sex, greater novelty seeking, impulsivity, depression and premorbid impulse control disorders as the most consistent risk factors. Such patients may warrant special monitoring after starting treatment with a DA. Various individual screening tools are available for people without Parkinson’s disease. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease has been developed specifically for Parkinson’s disease. The best treatment for impulse control disorders is prevention. However, after the development of impulse control disorders, the mainstay intervention is to reduce or discontinue the offending anti-Parkinsonian medication. In refractory cases, other pharmacological interventions are available, including neuroleptics, antiepileptics, amantadine, antiandrogens, lithium and opioid antagonists. Unfortunately, their use is only supported by case reports, small case series or open-label clinical studies. Prospective, controlled studies are warranted. Ongoing investigations include naltrexone and nicotine. PMID:23634190

Role of Serotonin and Dopamine System Interactions in the Neurobiology of Impulsive Aggression and its Comorbidity with other Clinical Disorders

PubMed Central

Seo, Dongju; Patrick, Christopher J.; Kennealy, Patrick J.

2008-01-01

Impulsive aggression is characterized by an inability to regulate affect as well as aggressive impulses, and is highly comorbid with other mental disorders including depression, suicidal behavior, and substance abuse. In an effort to elucidate the neurobiological underpinnings of impulsive aggression and to help account for its connections with these other disorders, this paper reviews relevant biochemical, brain imaging, and genetic studies. The review suggests that dysfunctional interactions between serotonin and dopamine systems in the prefrontal cortex may be an important mechanism underlying the link between impulsive aggression and its comorbid disorders. Specifically, serotonin hypofunction may represent a biochemical trait that predisposes individuals to impulsive aggression, with dopamine hyperfunction contributing in an additive fashion to the serotonergic deficit. The current paper proposes a modified diathesis-stress model of impulsive aggression in which the underlying biological diathesis may be deficient serotonergic function in the ventral prefrontal cortex. This underlying disposition can be manifested behaviorally as impulsive aggression towards oneself and others, and as depression under precipitating life stressors. Substance abuse associated with impulsive aggression is understood in the context of dopamine dysregulation resulting from serotonergic deficiency. Also discussed are future research directions in the neurobiology of impulsive aggression and its comorbid disorders. PMID:19802333

Impulsive Choice in Mice Lacking Paternal Expression of Grb10 Suggests Intragenomic Conflict in Behavior

PubMed Central

Dent, Claire L.; Humby, Trevor; Lewis, Katie; Ward, Andrew; Fischer-Colbrie, Reiner; Wilkinson, Lawrence S.; Wilkins, Jon F.; Isles, Anthony R.

2018-01-01

Imprinted genes are expressed from one parental allele only as a consequence of epigenetic events that take place in the mammalian germ line and are thought to have evolved through intragenomic conflict between parental alleles. We demonstrate, for the first time, oppositional effects of imprinted genes on brain and behavior. Specifically, we show that mice lacking paternal Grb10 make fewer impulsive choices, with no dissociable effects on a separate measure of impulsive action. Taken together with previous work showing that mice lacking maternal Nesp55 make more impulsive choices, this suggests that impulsive choice behavior is a substrate for the action of genomic imprinting. Moreover, the contrasting effect of these two genes suggests that impulsive choices are subject to intragenomic conflict and that maternal and paternal interests pull this behavior in opposite directions. Finally, these data may also indicate that an imbalance in expression of imprinted genes contributes to pathological conditions such as gambling and drug addiction, where impulsive behavior becomes maladaptive. PMID:29563147

Evidence for the Trait-Impulsivity Etiological Model in a Clinical Sample: Bifactor Structure and Its Relation to Impairment and Environmental Risk.

PubMed

Rodenacker, Klaas; Hautmann, Christopher; Görtz-Dorten, Anja; Döpfner, Manfred

2018-05-01

The trait-impulsivity etiological model assumes that a general factor (trait-impulsivity) underlies attention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and other externalizing disorders. We investigated the plausibility of this assumption by testing the factor structure of ADHD and ODD in a bifactor framework for a clinical sample of 1420 children between 6 and 18 years of age (M = 9.99, SD = 3.34; 85% male). Further, the trait-impulsivity etiological model assumes that ODD emerges only if environmental risk factors are present. Our results support the validity of the trait-impulsivity etiological model, as they confirm that ADHD and ODD share a strong general factor of disruptive behavior (DB) in this clinical sample. Furthermore, unlike the subdimensions of ADHD, we found that the specific ODD factor explained as much true score variance as the general DB factor. This suggests that a common scale of ADHD and ODD may prove to be as important as a separate ODD subscale to assess externalizing problems in school-age children. However, all other subscales of ADHD may not explain sufficient true score variance once the impact of the general DB factor has been taken into consideration. In accordance with the trait-impulsivity model, we also showed that all factors, but predominantly the general factor and specific inattention factor, predicted parent-rated impairment, and that predominantly ODD and impulsivity are predicted by environmental risk factors.

Testing of molded high temperature plastic actuator road seals for use in advanced aircraft hydraulic systems

NASA Technical Reports Server (NTRS)

Waterman, A. W.; Huxford, R. L.; Nelson, W. G.

1976-01-01

Molded high temperature plastic first and second stage rod seal elements were evaluated in seal assemblies to determine performance characteristics. These characteristics were compared with the performance of machined seal elements. The 6.35 cm second stage Chevron seal assembly was tested using molded Chevrons fabricated from five molding materials. Impulse screening tests conducted over a range of 311 K to 478 K revealed thermal setting deficiencies in the aromatic polyimide molding materials. Seal elements fabricated from aromatic copolyester materials structurally failed during impulse cycle calibration. Endurance testing of 3.85 million cycles at 450 K using MIL-H-83283 fluid showed poorer seal performance with the unfilled aromatic polyimide material than had been attained with seals machined from Vespel SP-21 material. The 6.35 cm first stage step-cut compression loaded seal ring fabricated from copolyester injection molding material failed structurally during impulse cycle calibration. Molding of complex shape rod seals was shown to be a potentially controllable technique, but additional molding material property testing is recommended.

A-law/Mu-law Dynamic Range Compression Deconvolution (Preprint)

DTIC Science & Technology

2008-02-04

noise filtering via the spectrum proportionality filter, and second the signal deblurring via the inverse filter. In this process for regions when...is the joint image of motion impulse response and the noisy blurred image with signal to noise ratio 5, 6(A’) is the gray level recovered image...joint image of motion impulse response and the noisy blurred image with signal to noise ratio 5, (A’) the gray level recovered image using the A-law

Threshold virus dynamics with impulsive antiretroviral drug effects

PubMed Central

Lou, Jie; Lou, Yijun; Wu, Jianhong

2013-01-01

The purposes of this paper are twofold: to develop a rigorous approach to analyze the threshold behaviors of nonlinear virus dynamics models with impulsive drug effects and to examine the feasibility of virus clearance following the Manuals of National AIDS Free Antiviral Treatment in China. An impulsive system of differential equations is developed to describe the within-host virus dynamics of both wild-type and drug-resistant strains when a combination of antiretroviral drugs is used to induce instantaneous drug effects at a sequence of dosing times equally spaced while drug concentrations decay exponentially after the dosing time. Threshold parameters are derived using the basic reproduction number of periodic epidemic models, and are used to depict virus clearance/persistence scenarios using the theory of asymptotic periodic systems and the persistence theory of discrete dynamical systems. Numerical simulations using model systems parametrized in terms of the antiretroviral therapy recommended in the aforementioned Manuals illustrate the theoretical threshold virus dynamics, and examine conditions under which the impulsive antiretroviral therapy leads to treatment success. In particular, our results show that only the drug-resistant strain can dominate (the first-line treatment program guided by the Manuals) or both strains may be rapidly eliminated (the second-line treatment program), thus the work indicates the importance of implementing the second-line treatment program as soon as possible. PMID:21987085

Mechanisms of Individual Differences in Impulsive and Risky Choice in Rats

PubMed Central

Kirkpatrick, Kimberly; Marshall, Andrew T.; Smith, Aaron P.

2016-01-01

Individual differences in impulsive and risky choice are key risk factors for a variety of maladaptive behaviors such as drug abuse, gambling, and obesity. In our rat model, ordered individual differences are stable across choice parameters, months of testing, and span a broad spectrum, suggesting that rats, like humans, exhibit trait-level impulsive and risky choice behaviors. In addition, impulsive and risky choices are highly correlated, suggesting a degree of correlation between these two traits. An examination of the underlying cognitive mechanisms has suggested an important role for timing processes in impulsive choice. In addition, in an examination of genetic factors in impulsive choice, the Lewis rat strain emerged as a possible animal model for studying disordered impulsive choice, with this strain demonstrating deficient delay processing. Early rearing environment also affected impulsive behaviors, with rearing in an enriched environment promoting adaptable and more self-controlled choices. The combined results with impulsive choice suggest an important role for timing and reward sensitivity in moderating impulsive behaviors. Relative reward valuation also affects risky choice, with manipulation of objective reward value (relative to an alternative reference point) resulting in loss chasing behaviors that predicted overall risky choice behaviors. The combined results are discussed in relation to domain-specific versus domain-general subjective reward valuation processes and the potential neural substrates of impulsive and risky choice. PMID:27695580

Impulsivity-like Traits and Risky Driving Behaviors among College Students

PubMed Central

Murphy, Elaine M.; Doane, Ashley N.

2017-01-01

The present study examined the predictive effects of five impulsivity-like traits (Premeditation, Perseverance, Sensation Seeking, Negative Urgency, and Positive Urgency) on driving outcomes (driving errors, driving lapses, driving violations, cell phone driving, traffic citations, and traffic collisions). With a convenience sample of 266 college student drivers, we found that each of the impulsivity-like traits was related to multiple risky driving outcomes. Positive Urgency (tendency to act impulsively when experiencing negative affect) was the most robust predictor of risky driving outcomes. Positive Urgency is a relatively newly conceptualized impulsivity-like trait that was not examined in the driving literature previously, suggesting a strong need to further examine its role as a personality trait related to risky driving. These findings generally support the multidimensional assessment of impulsivity-like traits, and they specifically support the addition of Positive Urgency to a list of risk factors for risky driving behaviors. PMID:23428428

Impulsivity-like traits and risky driving behaviors among college students.

PubMed

Pearson, Matthew R; Murphy, Elaine M; Doane, Ashley N

2013-04-01

The present study examined the predictive effects of five impulsivity-like traits (Premeditation, Perseverance, Sensation Seeking, Negative Urgency, and Positive Urgency) on driving outcomes (driving errors, driving lapses, driving violations, cell phone driving, traffic citations, and traffic collisions). With a convenience sample of 266 college student drivers, we found that each of the impulsivity-like traits was related to multiple risky driving outcomes. Positive Urgency (tendency to act impulsively when experiencing negative affect) was the most robust predictor of risky driving outcomes. Positive Urgency is a relatively newly conceptualized impulsivity-like trait that was not examined in the driving literature previously, suggesting a strong need to further examine its role as a personality trait related to risky driving. These findings generally support the multidimensional assessment of impulsivity-like traits, and they specifically support the addition of Positive Urgency to a list of risk factors for risky driving behaviors. Copyright © 2013 Elsevier Ltd. All rights reserved.

The influence of impulsiveness on binge eating and problem gambling: A prospective study of gender differences in Canadian adults.

PubMed

Farstad, Sarah M; von Ranson, Kristin M; Hodgins, David C; El-Guebaly, Nady; Casey, David M; Schopflocher, Don P

2015-09-01

This study investigated the degree to which facets of impulsiveness predicted future binge eating and problem gambling, 2 theorized forms of behavioral addiction. Participants were 596 women and 406 men from 4 age cohorts randomly recruited from a Canadian province. Participants completed self-report measures of 3 facets of impulsiveness (negative urgency, sensation seeking, lack of persistence), binge-eating frequency, and problem-gambling symptoms. Impulsiveness was assessed at baseline, and assessments of binge eating and problem gambling were followed up after 3 years. Weighted data were analyzed using zero-inflated negative binomial and Poisson regression models. We found evidence of transdiagnostic and disorder-specific predictors of binge eating and problem gambling. Negative urgency emerged as a common predictor of binge eating and problem gambling among women and men. There were disorder-specific personality traits identified among men only: High lack-of-persistence scores predicted binge eating and high sensation-seeking scores predicted problem gambling. Among women, younger age predicted binge eating and older age predicted problem gambling. Thus, there are gender differences in facets of impulsiveness that longitudinally predict binge eating and problem gambling, suggesting that treatments for these behaviors should consider gender-specific personality and demographic traits in addition to the common personality trait of negative urgency. (c) 2015 APA, all rights reserved).

The ENABLER - Based on proven NERVA technology

NASA Astrophysics Data System (ADS)

Livingston, Julie M.; Pierce, Bill L.

The ENABLER reactor for use in a nuclear thermal propulsion engine uses the technology developed in the NERVA/Rover program, updated to incorporate advances in the technology. Using composite fuel, higher power densities per fuel element, improved radiation resistant control components and the advancements in use of carbon-carbon materials; the ENABLER can provide a specific impulse of 925 seconds, an engine thrust to weight (excluding reactor shield) approaching five, an improved initial mass in low Earth orbit and a consequent reduction in launch costs and logistics problems. This paper describes the 75,000 lbs thrust ENABLER design which is a low cost, low risk approach to meeting tommorrow's space propulsion needs.

Performance effects resulting from plugged liquid oxygen posts of the Space Shuttle Main Engine Injector

NASA Technical Reports Server (NTRS)

Kim, S.; Trinh, H. P.

1992-01-01

The paper discusses the performance effects resulting from plugged LOX posts of the Space Shuttle Main Engine Injector. The simulation was performed with the REFLEQS 2-D code. Analysis was performed axisymmetrically and injector surface was divided into several regions to account for the mixture ratio variation on the injector surface. The reduction of vaccum specific impulse was approximately 0.01 second per plugged LOX post. This reduction is an order of magnitude higher than the result of Space Shuttle flight reconstruction data. It is presumed that this overprediction is due to the axisymmetric simulation that smears local effects.

Performance capabilities of the 8-cm mercury ion thruster

NASA Technical Reports Server (NTRS)

Mantenieks, M. A.

1981-01-01

A preliminary characterization of the performance capabilities of the 8-cm thruster in order to initiate an evaluation of its application to LSS propulsion requirements is presented. With minor thruster modifications, the thrust was increased by about a factor of four while the discharge voltage was reduced from 39 to 22 volts. The thruster was operated over a range of specific impulse of 1950 to 3040 seconds and a maximum total efficiency of about 54 percent was attained. Preliminary analysis of component lifetimes, as determined by temperature and spectroscopic line intensity measurements, indicated acceptable thruster lifetimes are anticipated at the high power level operation.

Metallic Hydrogen - Potentially a High Energy Rocket Propellant

NASA Technical Reports Server (NTRS)

Cole, John; Silvera, Ike

2007-01-01

Pure metallic hydrogen is predicted to have a specific impulse (Isp) of 1700 seconds, but the reaction temperature is too high for current engine materials. Diluting metallic hydrogen with liquid hydrogen can reduce the reaction temperature to levels compatible with current material limits and still provide an Isp greater than 900 s. Metallic hydrogen has not yet been produced on earth, but experimental techniques exist that may change this situation. This paper will provide a brief description of metallic hydrogen and the status of experiments that may soon produce detectable quantities of this material in the lab. Also provided are some characteristics for diluted metallic hydrogen engines and launch vehicles.

Trait and state impulsivity in males with tendency towards Internet-pornography-use disorder.

PubMed

Antons, Stephanie; Brand, Matthias

2018-04-01

Impulsivity has been identified to be involved in the development and maintenance of specific Internet-use disorders (IUD). It can be differentiated between relatively stable trait impulsivity and state impulsivity which is dependent on environmental and affective factors such as craving. Following the I-PACE (Interaction of Person-Affect-Cognition-Execution) model, both trait and state impulsivity may play an interactive role in IUD. The present study aimed to investigate the relationship between trait and state impulsivity and symptom severity of Internet-pornography-use disorder (IPD) as one form of IUD. Fifty heterosexual males participated in this study. State impulsivity was measured with reaction times in a modified stop-signal task. Each participant conducted two blocks of this task which included neutral and pornographic pictures. Moreover, current subjective craving, trait impulsivity, and symptom severity of IPD were assessed using several questionnaires. Results indicate that trait impulsivity was associated with higher symptom severity of IPD. Especially those males with higher trait impulsivity and state impulsivity in the pornographic condition of the stop-signal task as well as those with high craving reactions showed severe symptoms of IPD. The results indicate that both trait and state impulsivity play a crucial role in the development of IPD. In accordance with dual-process models of addiction, the results may be indicative of an imbalance between the impulsive and reflective systems which might be triggered by pornographic material. This may result in loss of control over the Internet-pornography use albeit experiencing negative consequences. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effective specific impulse of external nuclear pulse propulsion systems

NASA Technical Reports Server (NTRS)

Reynolds, T. W.

1972-01-01

An investigation of a simple self-similar flow model for an external nuclear pulse propulsion system indicates that to achieve the high effective specific impulse of such a system three principal factors are required. The are (1) attaining pulses of optimum energy, (2) attaining good propellant collimation, and (3) using an ablative material for the pusher surface which has high absorptivity for radiant energy at the propellant stagnation temperature.

The relationship between second-to-fourth digit (2D:4D) ratios and problematic and pathological Internet use among Turkish university students.

PubMed

Canan, Fatih; Karaca, Servet; Düzgün, Melike; Erdem, Ayşe Merve; Karaçaylı, Esranur; Topan, Nur Begüm; Lee, Sang-Kyu; Zhai, Zu Wei; Kuloğlu, Murat; Potenza, Marc N

2017-03-01

Background and aims The ratio of the second and fourth fingers (2D:4D ratio) is a sexually dimorphic trait, with men tending to have lower values than women. This ratio has been related to prenatal testosterone concentrations and addictive behaviors including problematic video-gaming. We aimed to investigate the possible association between 2D:4D ratios and Internet addiction and whether such a relationship would be independent of impulsivity. Methods A total of 652 university students (369 women, 283 men), aged 17-27 years, were enrolled in the study. Problematic and pathological Internet use (PPIU) was assessed using the Internet Addiction Test (IAT). The participants also completed the Barratt Impulsiveness Scale (version 11; BIS-11) and had their 2D:4D ratios measured. Results 2D:4D ratios were not significantly different in women with PPIU and in those with adaptive Internet use (AIU). Men with PPIU exhibited lower 2D:4D ratios on both hands when compared with those with AIU. Correlation analysis revealed that 2D:4D ratios on both hands were negatively correlated with IAT scores among men, but not among women. The multiple linear regression analysis revealed that age, duration of weekly Internet use, impulsiveness, and 2D:4D ratios on the right hand were independently associated with IAT scores among men, and impulsivity did not mediate the relationship between 2D:4D ratios and PPIU. Conclusions For men, 2D:4D ratios on the right hand were inversely correlated with Internet addiction severity even after controlling for individual differences in impulsivity. These findings suggest that high prenatal testosterone levels may contribute to the occurrence of PPIU among men.

The relationship between second-to-fourth digit (2D:4D) ratios and problematic and pathological Internet use among Turkish university students

PubMed Central

Canan, Fatih; Karaca, Servet; Düzgün, Melike; Erdem, Ayşe Merve; Karaçaylı, Esranur; Topan, Nur Begüm; Lee, Sang-Kyu; Zhai, Zu Wei; Kuloğlu, Murat; Potenza, Marc N.

2017-01-01

Background and aims The ratio of the second and fourth fingers (2D:4D ratio) is a sexually dimorphic trait, with men tending to have lower values than women. This ratio has been related to prenatal testosterone concentrations and addictive behaviors including problematic video-gaming. We aimed to investigate the possible association between 2D:4D ratios and Internet addiction and whether such a relationship would be independent of impulsivity. Methods A total of 652 university students (369 women, 283 men), aged 17–27 years, were enrolled in the study. Problematic and pathological Internet use (PPIU) was assessed using the Internet Addiction Test (IAT). The participants also completed the Barratt Impulsiveness Scale (version 11; BIS-11) and had their 2D:4D ratios measured. Results 2D:4D ratios were not significantly different in women with PPIU and in those with adaptive Internet use (AIU). Men with PPIU exhibited lower 2D:4D ratios on both hands when compared with those with AIU. Correlation analysis revealed that 2D:4D ratios on both hands were negatively correlated with IAT scores among men, but not among women. The multiple linear regression analysis revealed that age, duration of weekly Internet use, impulsiveness, and 2D:4D ratios on the right hand were independently associated with IAT scores among men, and impulsivity did not mediate the relationship between 2D:4D ratios and PPIU. Conclusions For men, 2D:4D ratios on the right hand were inversely correlated with Internet addiction severity even after controlling for individual differences in impulsivity. These findings suggest that high prenatal testosterone levels may contribute to the occurrence of PPIU among men. PMID:28358645

Impulsive-choice patterns for food in genetically lean and obese Zucker rats

PubMed Central

Boomhower, Steven R.; Rasmussen, Erin B.; Doherty, Tiffany S.

2012-01-01

Behavioral-economic studies have shown that differences between lean and obese Zuckers in food consumption depend on the response requirement for food. Since a response requirement inherently increases the delay to reinforcement, differences in sensitivity to delay may also be a relevant mechanism of food consumption in the obese Zucker rat. Furthermore, the endocannabinoid neurotransmitter system has been implicated in impulsivity, but studies that attempt to characterize the effects of cannabinoid drugs (e.g., rimonabant) on impulsive choice may be limited by floor effects. The present study aimed to characterize impulsive-choice patterns for sucrose using an adjusting-delay procedure in genetically lean and obese Zuckers. Ten lean and ten obese Zucker rats chose between one lever that resulted in one pellet after a standard delay (either 1 s or 5 s) and a second lever that resulted in two or three pellets after an adjusting delay. After behavior stabilized under baseline, rimonabant (0–10 mg/kg) was administered prior to some choice sessions in the two-pellet condition. Under baseline, obese Zuckers made more impulsive choices than leans in three of the four standard-delay/pellet conditions. Additionally, in the 2-pellet condition, rimonabant increased impulsive choice in lean rats in the 1-s standard-delay condition; however, rimonabant decreased impulsive choice in obese rats in the 1-s and 5-s standard-delay conditions. These data suggest that genetic factors that influence impulsive choice are stronger in some choice conditions than others, and that the endocannabinoid system may be a relevant neuromechanism. PMID:23261877

Impulsive-choice patterns for food in genetically lean and obese Zucker rats.

PubMed

Boomhower, Steven R; Rasmussen, Erin B; Doherty, Tiffany S

2013-03-15

Behavioral-economic studies have shown that differences between lean and obese Zuckers in food consumption depend on the response requirement for food. Since a response requirement inherently increases the delay to reinforcement, differences in sensitivity to delay may also be a relevant mechanism of food consumption in the obese Zucker rat. Furthermore, the endocannabinoid neurotransmitter system has been implicated in impulsivity, but studies that attempt to characterize the effects of cannabinoid drugs (e.g., rimonabant) on impulsive choice may be limited by floor effects. The present study aimed to characterize impulsive-choice patterns for sucrose using an adjusting-delay procedure in genetically lean and obese Zuckers. Ten lean and ten obese Zucker rats chose between one lever that resulted in one pellet after a standard delay (either 1 s or 5 s) and a second lever that resulted in two or three pellets after an adjusting delay. After behavior stabilized under baseline, rimonabant (0-10 mg/kg) was administered prior to some choice sessions in the two-pellet condition. Under baseline, obese Zuckers made more impulsive choices than leans in three of the four standard-delay/pellet conditions. Additionally, in the 2-pellet condition, rimonabant increased impulsive choice in lean rats in the 1-s standard-delay condition; however, rimonabant decreased impulsive choice in obese rats in the 1-s and 5-s standard-delay conditions. These data suggest that genetic factors that influence impulsive choice are stronger in some choice conditions than others, and that the endocannabinoid system may be a relevant neuromechanism. Copyright © 2012 Elsevier B.V. All rights reserved.

Neural substrates of time perception and impulsivity

PubMed Central

Wittmann, Marc; Simmons, Alan N.; Flagan, Taru; Lane, Scott D.; Wackermann, Jiří; Paulus, Martin P.

2011-01-01

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 18 seconds 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 interval 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 cortex, 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

Comparison of Electrostatic Fins with Piezoelectric Impact Hammer Techniques to Extend Impulse Calibration Range of a Torsional Thrust Stand (Preprint)

DTIC Science & Technology

2011-03-23

prac- tical max impulse to 1mNs. The newly developed Piezo - electric Impact Hammer (PIH) calibration system over- comes geometric limits of ESC...the fins to behave as part of an LRC circuit which results in voltage oscillations. By adding a resistor in series between the pulse generator and...series resistor as well as the effects of no loading on the pulse generator. III. PIEZOELECTRIC IMPACT HAMMER SYSTEM The second calibration method tested

Low Pretreatment Impulsivity and High Medication Adherence Increase the Odds of Abstinence in a Trial of N-Acetylcysteine in Adolescents with Cannabis Use Disorder

PubMed Central

Bentzley, Jessica P.; Tomko, Rachel L.; Gray, Kevin M.

2016-01-01

Background In light of recent progress toward pharmacologic interventions to treat adolescent cannabis use disorder, it is important to consider which adolescent characteristics may be associated with a favorable response to treatment. This study presents secondary analyses from a parent randomized controlled trial of N-acetylcysteine (NAC) in adolescents with cannabis use disorder. We hypothesized high pretreatment impulsivity and medication non-adherence would be associated with reduced abstinence rates. Methods Participants were treatment-seeking adolescents (N = 115) who met criteria for cannabis use disorder and were assessed for pretreatment impulsivity. They received 1200 mg NAC or placebo orally twice daily for 8 weeks. An intent-to-treat analysis using a repeated-measures logistic regression model was used to relate pretreatment impulsivity (Barratt Impulsiveness Scale) and treatment group to abstinence rates, measured by urine cannabinoid tests. To explore mechanisms by which NAC may reduce cannabis use, relationships between impulsivity, adherence, and abstinence were assessed in a second statistical model using data from participants with recorded adherence and urine cannabinoid test results (n = 54). Results In the intent-to-treat analysis, low pretreatment impulsivity, NAC treatment, and negative baseline urine cannabinoid test results independently increased the odds of having negative urine cannabinoid tests during treatment (OR = 2.1, 2.3, 5.3 respectively). In the sample of participants with adherence data (n = 54), adherence tripled the odds of abstinence. Notably, the effect of adherence on abstinence was only observed in the NAC treatment group. Lastly, although the highly impulsive participants had reduced rates of abstinence, highly impulsive individuals adherent to NAC treatment had increased abstinence rates compared to non-adherent individuals. Conclusion Low impulsivity, NAC treatment, medication adherence, and baseline negative cannabinoid testing were associated with increased rates of abstinence in adolescents seeking treatment for cannabis use disorder. Efforts to optimize pharmacotherapy adherence may be particularly crucial for highly impulsive individuals. Understanding and addressing factors, such as impulsivity and adherence, which may affect outcomes, may aid in the successful evaluation and development of potentially promising pharmacotherapies. PMID:26827257

How impulsivity relates to compulsive buying and the burden perceived by caregivers after moderate-to-severe traumatic brain injury.

PubMed

Rochat, Lucien; Beni, Catia; Billieux, Joël; Annoni, Jean-Marie; Van der Linden, Martial

2011-01-01

Impulsivity is a core feature in patients with traumatic brain injury (TBI). The aim of the study is to investigate how a specific dimension of impulsivity, namely urgency (the tendency to act rashly when distressed), might shed new light on the aetiology of compulsive buying proneness in patients with TBI and to explore how urgency and compulsive buying relate to the burden perceived by the caregivers. Caregivers of 74 patients with TBI were given 3 questionnaires in order to assess their subjective burden as well as patients' impulsivity and compulsive buying proneness. Both urgency and compulsive buying tendencies significantly increased after TBI. Furthermore, path analyses revealed that current urgency was both directly and indirectly related to the subjective burden perceived by the caregivers, and this indirect pathway was mediated by compulsive buying. Urgency plays a central role in understanding specific problematic behaviours after TBI and their impact on caregivers. These findings are discussed in light of the cognitive processes underlying the urgency component of impulsivity in relation to the occurrence of compulsive buying behaviours after TBI. Copyright © 2011 S. Karger AG, Basel.

Direct and indirect effects of impulsivity traits on drinking and driving in young adults.

PubMed

Treloar, Hayley R; Morris, David H; Pedersen, Sarah L; McCarthy, Denis M

2012-09-01

Impulsivity is strongly associated with alcohol-related risk-taking behavior, and this association has been found to be mediated by alcohol cognitions. The current study expanded this literature by comparing the relative association of distinct impulsivity traits with a specific risky behavior--drinking and driving. We then tested whether drinking-and-driving expectancies uniquely mediated this relation over and above other cognitions about alcohol and drinking and driving. College student drivers (n = 816; 53.6% women) completed a paper-and-pencil survey in small groups. Self-report measures assessed alcohol use, impulsivity traits, alcohol expectancies, drinking-and-driving cognitions (i.e., expectancies, attitudes, beliefs), and drinking and driving. Although all impulsivity traits were correlated with drinking and driving, only urgency uniquely contributed to drinking and driving. Indirect effect tests indicated that drinking-and-driving convenience expectancies partially mediated this association as well as that between (lack of) perseverance and drinking and driving. These results remained significant after controlling for alcohol expectancies and other drinking-and-driving cognitions. These findings highlight the importance of distinguishing among impulsivity traits to improve theoretical models of the processes by which personality leads to specific alcohol-related consequences. In addition, results extend previous research by providing evidence for the unique importance of expectancies regarding the convenience of drinking and driving over and above more global alcohol expectancies and other drinking-and-driving cognitions.

Does drinking refusal self-efficacy mediate the impulsivity-problematic alcohol use relation?

PubMed

Stevens, Angela K; Littlefield, Andrew K; Blanchard, Brittany E; Talley, Amelia E; Brown, Jennifer L

2016-02-01

There is consistent evidence that impulsivity-like traits relate to problematic alcohol involvement; however, identifying mechanisms that account for this relation remains an important area of research. Drinking refusal self-efficacy (or a person's ability to resist alcohol; DRSE) has been shown to predict alcohol use among college students and may be a relevant mediator of the impulsivity-alcohol relation. The current study examined the indirect effect of various constructs related to impulsivity (i.e., urgency, sensation seeking, and deficits in conscientiousness) via several facets of DRSE (i.e., social pressure, opportunistic, and emotional relief) on alcohol-related problems among a large sample of college students (N=891). Overall, results indicated that certain DRSE facets were significant mediators of the relation between impulsivity-related constructs and alcohol problems. More specifically, emotional-relief DRSE was a mediator for the respective relations between urgency and deficits in conscientiousness and alcohol problems, whereas social-DRSE was a significant mediator of the respective relations between urgency and sensation seeking with alcohol problems. Results from this study suggest particular types of DRSE are important mediators of the relations between specific impulsivity constructs and alcohol-related problems. These findings support prevention and intervention efforts that seek to enhance drinking refusal self-efficacy skills of college students, particularly those high in certain personality features, in order to reduce alcohol-related problems among this population. Copyright © 2015 Elsevier Ltd. All rights reserved.

Full-waveform detection of non-impulsive seismic events based on time-reversal methods

NASA Astrophysics Data System (ADS)

Solano, Ericka Alinne; Hjörleifsdóttir, Vala; Liu, Qinya

2017-12-01

We present a full-waveform detection method for non-impulsive seismic events, based on time-reversal principles. We use the strain Green's tensor as a matched filter, correlating it with continuous observed seismograms, to detect non-impulsive seismic events. We show that this is mathematically equivalent to an adjoint method for detecting earthquakes. We define the detection function, a scalar valued function, which depends on the stacked correlations for a group of stations. Event detections are given by the times at which the amplitude of the detection function exceeds a given value relative to the noise level. The method can make use of the whole seismic waveform or any combination of time-windows with different filters. It is expected to have an advantage compared to traditional detection methods for events that do not produce energetic and impulsive P waves, for example glacial events, landslides, volcanic events and transform-fault earthquakes for events which velocity structure along the path is relatively well known. Furthermore, the method has advantages over empirical Greens functions template matching methods, as it does not depend on records from previously detected events, and therefore is not limited to events occurring in similar regions and with similar focal mechanisms as these events. The method is not specific to any particular way of calculating the synthetic seismograms, and therefore complicated structural models can be used. This is particularly beneficial for intermediate size events that are registered on regional networks, for which the effect of lateral structure on the waveforms can be significant. To demonstrate the feasibility of the method, we apply it to two different areas located along the mid-oceanic ridge system west of Mexico where non-impulsive events have been reported. The first study area is between Clipperton and Siqueiros transform faults (9°N), during the time of two earthquake swarms, occurring in March 2012 and May 2016. The second area of interest is the Gulf of California where two swarms took place during July and September of 2015. We show that we are able to detect previously non-reported, non-impulsive events and recommend that this method be used together with more traditional template matching methods to maximize the number of detected events.

Low thrust chemical rocket technology

NASA Technical Reports Server (NTRS)

Schneider, Steven J.

1992-01-01

An on-going technology program to improve the performance of low thrust chemical rockets for spacecraft on-board propulsion applications is reviewed. Improved performance and lifetime is sought by the development of new predictive tools to understand the combustion and flow physics, introduction of high temperature materials and improved component designs to optimize performance, and use of higher performance propellants. Improved predictive technology is sought through the comparison of both local and global predictions with experimental data. Predictions are based on both the RPLUS Navier-Stokes code with finite rate kinetics and the JANNAF methodology. Data were obtained with laser-based diagnostics along with global performance measurements. Results indicate that the modeling of the injector and the combustion process needs improvement in these codes and flow visualization with a technique such as 2-D laser induced fluorescence (LIF) would aid in resolving issues of flow symmetry and shear layer combustion processes. High temperature material fabrication processes are under development and small rockets are being designed, fabricated, and tested using these new materials. Rhenium coated with iridium for oxidation protection was produced by the Chemical Vapor Deposition (CVD) process and enabled an 800 K increase in rocket operating temperature. Performance gains with this material in rockets using Earth storable propellants (nitrogen tetroxide and monomethylhydrazine or hydrazine) were obtained through component redesign to eliminate fuel film cooling and its associated combustion inefficiency while managing head end thermal soakback. Material interdiffusion and oxidation characteristics indicated that the requisite lifetimes of tens of hours were available for thruster applications. Rockets were designed, fabricated, and tested with thrusts of 22, 62, 440 and 550 N. Performance improvements of 10 to 20 seconds specific impulse were demonstrated. Higher performance propellants were evaluated: Space storable propellants, including liquid oxygen (LOX) as the oxidizer with nitrogen hydrides or hydrocarbon as fuels. Specifically, a LOX/hydrazine engine was designed, fabricated, and shown to have a 95 pct theoretical c-star which translates into a projected vacuum specific impulse of 345 seconds at an area ratio of 204:1. Further performance improvment can be obtained by the use of LOX/hydrogen propellants, especially for manned spacecraft applications, and specific designs must be developed and advanced through flight qualification.

Transitional geomagnetic impulse hypothesis: Geomagnetic fact or rock-magnetic artifact?

NASA Astrophysics Data System (ADS)

Camps, Pierre; Coe, Robert S.; PréVot, Michel

1999-08-01

A striking feature of the Steens Mountain (Oregon) geomagnetic polarity reversal is the two (maybe three) extremely rapid field directional changes (6 degrees per day) proposed to account for unusual behavior in direction of remanent magnetization in a single lava flow. Each of these very fast field changes, or impulses, is associated with a large directional gap (some 90°) in the record. In order to check the spatial reproducibility of the paleomagnetic signal over distances up to several kilometers, we have carried out a paleomagnetic investigation of two new sections (B and F) in the Steens summit region which cover the second and the third directional gap. The main result is the description of two new directions, which are located between the pre second and post second impulse directions. These findings weigh against the hypothesis that the geomagnetic field cause the unusual intraflow fluctuations, which now appears to be more ad hoc as an explanation of the paleomagnetic data. However, the alternative baking hypothesis remains also ad hoc since we have to assume variable rock magnetic properties that we have not yet been able to detect within the flows at the original section Steens A and D 1.5 km to the north. In addition, new results for 22 transitional and normal lava flows in section B are presented that correlate well with earlier results from section A.

Individual Differences in Impulsivity Predict Anticipatory Eye Movements

PubMed Central

Cirilli, Laetitia; de Timary, Philippe; Lefèvre, Phillipe; Missal, Marcus

2011-01-01

Impulsivity is the tendency to act without forethought. It is a personality trait commonly used in the diagnosis of many psychiatric diseases. In clinical practice, impulsivity is estimated using written questionnaires. However, answers to questions might be subject to personal biases and misinterpretations. In order to alleviate this problem, eye movements could be used to study differences in decision processes related to impulsivity. Therefore, we investigated correlations between impulsivity scores obtained with a questionnaire in healthy subjects and characteristics of their anticipatory eye movements in a simple smooth pursuit task. Healthy subjects were asked to answer the UPPS questionnaire (Urgency Premeditation Perseverance and Sensation seeking Impulsive Behavior scale), which distinguishes four independent dimensions of impulsivity: Urgency, lack of Premeditation, lack of Perseverance, and Sensation seeking. The same subjects took part in an oculomotor task that consisted of pursuing a target that moved in a predictable direction. This task reliably evoked anticipatory saccades and smooth eye movements. We found that eye movement characteristics such as latency and velocity were significantly correlated with UPPS scores. The specific correlations between distinct UPPS factors and oculomotor anticipation parameters support the validity of the UPPS construct and corroborate neurobiological explanations for impulsivity. We suggest that the oculomotor approach of impulsivity put forth in the present study could help bridge the gap between psychiatry and physiology. PMID:22046334

Test-retest reliability of behavioral measures of impulsive choice, impulsive action, and inattention.

PubMed

Weafer, Jessica; Baggott, Matthew J; de Wit, Harriet

2013-12-01

Behavioral measures of impulsivity are widely used in substance abuse research, yet relatively little attention has been devoted to establishing their psychometric properties, especially their reliability over repeated administration. The current study examined the test-retest reliability of a battery of standardized behavioral impulsivity tasks, including measures of impulsive choice (i.e., delay discounting, probability discounting, and the Balloon Analogue Risk Task), impulsive action (i.e., the stop signal task, the go/no-go task, and commission errors on the continuous performance task), and inattention (i.e., attention lapses on a simple reaction time task and omission errors on the continuous performance task). Healthy adults (n = 128) performed the battery on two separate occasions. Reliability estimates for the individual tasks ranged from moderate to high, with Pearson correlations within the specific impulsivity domains as follows: impulsive choice (r range: .76-.89, ps < .001); impulsive action (r range: .65-.73, ps < .001); and inattention (r range: .38-.42, ps < .001). Additionally, the influence of day-to-day fluctuations in mood, as measured by the Profile of Mood States, was assessed in relation to variability in performance on each of the behavioral tasks. Change in performance on the delay discounting task was significantly associated with change in positive mood and arousal. No other behavioral measures were significantly associated with mood. In sum, the current analysis demonstrates that behavioral measures of impulsivity are reliable measures and thus can be confidently used to assess various facets of impulsivity as intermediate phenotypes for drug abuse.

Integrative Understanding of Familial Impulsivity, Early Adversity and Suicide Risk.

PubMed

Lima, Isabela M M; Malloy-Diniz, Leandro F; de Miranda, Débora M; Da Silva, Antônio G; Neves, Fernando S; Johnson, Sheri L

2017-01-01

Introduction: Impulsivity is a core characteristic of bipolar disorder and it was observed as elevated in individuals with the disorder and in their relatives. Both impulsivity and history of maltreatment are risk factors for suicide attempts, however, these two key variables may not be independent, given the fact that parental impulsivity and associated social context could increase the risk of child maltreatment. In this study it was examined the association between the impulsivity of relatives and child maltreatment taking into consideration the conjoint and unique effects of these two variables on the risk of suicide attempts among the patients. Materials and Methods: Participants of the study consisted of 117 patients diagnosed with bipolar disorder and 25 first-degree relatives. Linear regression model was conducted to describe associations between facets of impulsivity of relatives and levels of child maltreatment reported by patients. The independent associations of suicide attempt history with the dimensions of impulsivity of the patient and maltreatment were tested by multinomial logistic regression. Results: Impulsivity of relatives and, more specifically, inhibitory control can predict the maltreatment of the patient. Inhibitory control and emotional abuse were related, conjointly, to a greater likelihood of having a history of more than one suicide attempt. Discussion: Considering that the impulsivity of relatives predicts child maltreatment, it is possible that a genetically shared impulsivity is an underlying feature associated with the history of multiple suicide attempts. These findings highlight the importance of considering child maltreatment, impulsivity and suicide attempt history in integrative models.

Integrative Understanding of Familial Impulsivity, Early Adversity and Suicide Risk

PubMed Central

Lima, Isabela M. M.; Malloy-Diniz, Leandro F.; de Miranda, Débora M.; Da Silva, Antônio G.; Neves, Fernando S.; Johnson, Sheri L.

2017-01-01

Introduction: Impulsivity is a core characteristic of bipolar disorder and it was observed as elevated in individuals with the disorder and in their relatives. Both impulsivity and history of maltreatment are risk factors for suicide attempts, however, these two key variables may not be independent, given the fact that parental impulsivity and associated social context could increase the risk of child maltreatment. In this study it was examined the association between the impulsivity of relatives and child maltreatment taking into consideration the conjoint and unique effects of these two variables on the risk of suicide attempts among the patients. Materials and Methods: Participants of the study consisted of 117 patients diagnosed with bipolar disorder and 25 first-degree relatives. Linear regression model was conducted to describe associations between facets of impulsivity of relatives and levels of child maltreatment reported by patients. The independent associations of suicide attempt history with the dimensions of impulsivity of the patient and maltreatment were tested by multinomial logistic regression. Results: Impulsivity of relatives and, more specifically, inhibitory control can predict the maltreatment of the patient. Inhibitory control and emotional abuse were related, conjointly, to a greater likelihood of having a history of more than one suicide attempt. Discussion: Considering that the impulsivity of relatives predicts child maltreatment, it is possible that a genetically shared impulsivity is an underlying feature associated with the history of multiple suicide attempts. These findings highlight the importance of considering child maltreatment, impulsivity and suicide attempt history in integrative models. PMID:29312082

Test-retest reliability of behavioral measures of impulsive choice, impulsive action, and inattention

PubMed Central

Weafer, Jessica; Baggott, Matthew J.; de Wit, Harriet

2014-01-01

Behavioral measures of impulsivity are widely used in substance abuse research, yet relatively little attention has been devoted to establishing their psychometric properties, especially their reliability over repeated administration. The current study examined the test-retest reliability of a battery of standardized behavioral impulsivity tasks, including measures of impulsive choice (delay discounting, probability discounting, and the Balloon Analogue Risk Task), impulsive action (the stop signal task, the go/no-go task, and commission errors on the continuous performance task), and inattention (attention lapses on a simple reaction time task and omission errors on the continuous performance task). Healthy adults (n=128) performed the battery on two separate occasions. Reliability estimates for the individual tasks ranged from moderate to high, with Pearson correlations within the specific impulsivity domains as follows: impulsive choice (r = .76 - .89, ps < .001); impulsive action (r = .65 - .73, ps < .001); and inattention (r = .38-.42, ps < .001). Additionally, the influence of day-to-day fluctuations in mood as measured by the Profile of Mood States was assessed in relation to variability in performance on each of the behavioral tasks. Change in performance on the delay discounting task was significantly associated with change in positive mood and arousal. No other behavioral measures were significantly associated with mood. In sum, the current analysis demonstrates that behavioral measures of impulsivity are reliable measures and thus can be confidently used to assess various facets of impulsivity as intermediate phenotypes for drug abuse. PMID:24099351

Dopamine Gene Profiling to Predict Impulse Control and Effects of Dopamine Agonist Ropinirole.

PubMed

MacDonald, Hayley J; Stinear, Cathy M; Ren, April; Coxon, James P; Kao, Justin; Macdonald, Lorraine; Snow, Barry; Cramer, Steven C; Byblow, Winston D

2016-07-01

Dopamine agonists can impair inhibitory control and cause impulse control disorders for those with Parkinson disease (PD), although mechanistically this is not well understood. In this study, we hypothesized that the extent of such drug effects on impulse control is related to specific dopamine gene polymorphisms. This double-blind, placebo-controlled study aimed to examine the effect of single doses of 0.5 and 1.0 mg of the dopamine agonist ropinirole on impulse control in healthy adults of typical age for PD onset. Impulse control was measured by stop signal RT on a response inhibition task and by an index of impulsive decision-making on the Balloon Analogue Risk Task. A dopamine genetic risk score quantified basal dopamine neurotransmission from the influence of five genes: catechol-O-methyltransferase, dopamine transporter, and those encoding receptors D1, D2, and D3. With placebo, impulse control was better for the high versus low genetic risk score groups. Ropinirole modulated impulse control in a manner dependent on genetic risk score. For the lower score group, both doses improved response inhibition (decreased stop signal RT) whereas the lower dose reduced impulsiveness in decision-making. Conversely, the higher score group showed a trend for worsened response inhibition on the lower dose whereas both doses increased impulsiveness in decision-making. The implications of the present findings are that genotyping can be used to predict impulse control and whether it will improve or worsen with the administration of dopamine agonists.

Interacting Mechanisms of Impulsivity in Bipolar Disorder and Antisocial Personality Disorder

PubMed Central

Swann, Alan C.; Lijffijt, Marijn; Lane, Scott D.; Steinberg, Joel L.; Moeller, F. Gerard

2011-01-01

Background Bipolar disorder and antisocial personality disorder (ASPD) overlap in clinical characteristics and behavioral consequences. Impulsivity is prominent in both, but there is little information on how specific mechanisms of impulsivity differentiate, bridge, or underlie the disorders. Methods Subjects, all males, were controls (n=46), bipolar disorder without cluster B personality disorder (n=21), ASPD without bipolar disorder (n=50), and bipolar disorder with ASPD (n=16). Impulsivity measures were the Immediate Memory Task (IMT), a continuous performance test of response inhibition measuring ability to evaluate a stimulus before responding, and the Two Choice Impulsivity Paradigm (TCIP), a choice between smaller-sooner and larger-later reward. Data were analyzed using general linear models analysis. Results Subjects with bipolar disorder had fewer IMT correct detections and slower reaction times than controls. Reaction times were faster with combined diagnoses than in bipolar disorder alone. TCIP responding in either diagnosis alone resembled controls, but was more impulsive in combined disorders. These differences persisted after correction for age and education, which had significant independent effects. In combined ASPD and bipolar disorder, increased reaction speed, impulsive response bias, and reward-delay impulsivity occurred independent of substance-use disorder history. Conclusions Impulsivity was increased in the combined disorders over either disorder alone. Results were consistent with at least partially distinct mechanisms of impulsivity in ASPD and bipolar disorder. Compensatory mechanisms for impulsivity in uncomplicated ASPD or bipolar disorder appear to be compromised or lost when the disorders are combined. PMID:21719028

Effect of management of patients with Anorexia and Bulimia nervosa on symptoms and impulsive behavior.

PubMed

Sernec, Karin; Tomori, Martina; Zalar, Bojan

2010-12-01

The aim of the study was to provide further and up to date information on the evaluation of the management of Anorexia and Bulimia nervosa at the Eating Disorders Unit (EDU) of the Ljubljana Psychiatric Clinic, based upon detailed assessment of the eating disorders specific and non specific symptoms of impulsive behaviors, highly correlated with these entities. 34 female patients with anorexia (restrictive or purgative type) and 38 female patients with Bulimia nervosa (purgative or non-purgative type) undergoing hospital treatment at the EDU were evaluated upon admission, as well as upon discharge and three and six months after discharge, using the Eating Disorder Questionnaire. Upon discharge a marked decrease in the overall symptoms was noted. The differences in symptoms incidences between the two groups were significantly specific for the individual form of eating disorder, especially upon admission, and were more pronounced in anorexia group. In later measurements, performed during the period of three and six months after discharge, a mild trend of increase in the disorder specific symptoms was detected in both groups, but was not statistically significant. In addition to binging on food, striking, quarreling and spending sprees are characteristics of patients with eating disorders, which in particular apply to the Bulimia nervosa group. Apart from the disorder specific symptoms, impulsive behavior was also reduced during study period, while the difference in its occurrence between the two groups gradually became non-significant. The management of patients with eating disorders at the EDU was successful in both groups, confirmed by an intense reduction of the disorder specific symptoms, impulsive behavior and increased stability recorded three and six months after discharge. The study strongly suggests that the effect of treatment regime for eating disorders can be predicted by careful assessment of the relevant symptoms and impulsive behavioral patterns.

Effects of cumulative stress and impulsivity on smoking status.

PubMed

Ansell, Emily B; Gu, Peihua; Tuit, Keri; Sinha, Rajita

2012-03-01

The stress-vulnerability model of addiction predicts that environmental factors, such as cumulative stress, will result in individual adaptations that decrease self-control, increase impulsivity, and increase risk for addiction. Impulsivity and cumulative stress are risk factors for tobacco smoking that are rarely examined simultaneously in research. We examined the indirect and direct effects of cumulative adversity in a community sample consisting of 291 men and women who participated in an assessment of cumulative stress, self-reported impulsivity, and smoking history. Data were analyzed using bootstrapping techniques to estimate indirect effects of stress on smoking via impulsivity. Cumulative adversity is associated with smoking status via direct effects and indirect effects through impulsivity scores. Additional models examining specific types of stress indicate contributions of traumatic stress and recent life events as well as chronic relationship stressors. Overall, cumulative stress is associated with increased risk of smoking via increased impulsivity and via pathways independent of impulsivity. These findings support the stress-vulnerability model and highlight the utility of mediation models in assessing how, and for whom, cumulative stress increases risk of current cigarette smoking. Increasing self-control is a target for interventions with individuals who have experienced cumulative adversity. Copyright © 2012 John Wiley & Sons, Ltd.

Effects of cumulative stress and impulsivity on smoking status

PubMed Central

Ansell, Emily B.; Gu, Peihua; Tuit, Keri; Sinha, Rajita

2013-01-01

Objective The stress-vulnerability model of addiction predicts that environmental factors, such as cumulative stress, will result in individual adaptations that decrease self-control, increase impulsivity, and increase risk for addiction. Impulsivity and cumulative stress are risk factors for tobacco smoking that are rarely examined simultaneously in research. Methods We examined the indirect and direct effects of cumulative adversity in a community sample consisting of 291 men and women who participated in an assessment of cumulative stress, self-reported impulsivity, and smoking history. Data were analyzed using bootstrapping techniques to estimate indirect effects of stress on smoking via impulsivity. Results Cumulative adversity is associated with smoking status via direct effects and indirect effects through impulsivity scores. Additional models examining specific types of stress indicate contributions of traumatic stress and recent life events as well as chronic relationship stressors. Conclusions Overall, cumulative stress is associated with increased risk of smoking via increased impulsivity and via pathways independent of impulsivity. These findings support the stress-vulnerability model and highlight the utility of mediation models in assessing how, and for whom, cumulative stress increases risk of current cigarette smoking. Increasing self-control is a target for interventions with individuals who have experienced cumulative adversity. PMID:22389084

Substance Use in Undergraduate Students With Histories of Attention-Deficit/Hyperactivity Disorder (ADHD): The Role of Impulsivity.

PubMed

Egan, Theresa E; Dawson, Anne E; Wymbs, Brian T

2017-08-24

Emerging adulthood (18-25 years old) is regarded as a time of identity exploration that includes a peak in risky behaviors, such as substance use and misuse. Attention-deficit/hyperactivity disorder (ADHD) is also associated with greater levels of risky behaviors, including substance use and misuse; however, there is a lack of research on substance use by emerging adults with ADHD, in particular the potential mechanisms that may facilitate this risk. The present study builds on the existing research regarding the association between ADHD and substance use by examining roles of multiple facets of impulsivity in facilitating this association during emerging adulthood. In a sample of 197 undergraduate students (24 students with an ADHD diagnostic history), we assessed for components of impulsivity (e.g., urgency, sensation-seeking) and rates of alcohol abuse, tobacco use, cannabis use, illicit drug use, and stimulant medication misuse within the past year. Findings indicate that facets of impulsivity, as a whole, explained the association between an ADHD diagnostic history and both illicit drug use and alcohol abuse such that students with ADHD histories tended to report higher levels of impulsivity, which increased risk of alcohol abuse and illicit drug use. Higher levels of specific facets of impulsivity, particularly negative urgency, also facilitated associations between having ADHD and engaging in most forms of substance use tested herein. Conclusions/Importance: Specific facets of impulsivity appear to be important mediators of the association between ADHD and substance use, and should be considered as potential targets of substance use interventions for this population.

Impulsivity and opioid drugs: differential effects of heroin, methadone and prescribed analgesic medication.

PubMed

Baldacchino, A; Balfour, D J K; Matthews, K

2015-04-01

Previous studies have provided inconsistent evidence that chronic exposure to opioid drugs, including heroin and methadone, may be associated with impairments in executive neuropsychological functioning, specifically cognitive impulsivity. Further, it remains unclear how such impairments may relate of the nature, level and extent of opioid exposure, the presence and severity of opioid dependence, and hazardous behaviours such as injecting. Participants with histories of illicit heroin use (n = 24), former heroin users stabilized on prescribed methadone (methadone maintenance treatment; MMT) (n = 29), licit opioid prescriptions for chronic pain without history of abuse or dependence (n = 28) and healthy controls (n = 28) were recruited and tested on a task battery that included measures of cognitive impulsivity (Cambridge Gambling Task, CGT), motor impulsivity (Affective Go/NoGo, AGN) and non-planning impulsivity (Stockings of Cambridge, SOC). Illicit heroin users showed increased motor impulsivity and impaired strategic planning. Additionally, they placed higher bets earlier and risked more on the CGT. Stable MMT participants deliberated longer and placed higher bets earlier on the CGT, but did not risk more. Chronic opioid exposed pain participants did not differ from healthy controls on any measures on any tasks. The identified impairments did not appear to be associated specifically with histories of intravenous drug use, nor with estimates of total opioid exposure. These data support the hypothesis that different aspects of neuropsychological measures of impulsivity appear to be associated with exposure to different opioids. This could reflect either a neurobehavioural consequence of opioid exposure, or may represent an underlying trait vulnerability to opioid dependence.

Impulsivity Trajectories and Gambling in Adolescence among Urban Male Youth

PubMed Central

Liu, Weiwei; Lee, Grace P.; Goldweber, Asha; Petras, Hanno; Storr, Carla L.; Ialongo, Nicholas S.; Martins, Silvia S.

2012-01-01

Aim Building on the recent emerging literature on the impulsivity trajectory-gambling association, this study investigated the association between developmental trajectories of teacher-rated impulsivity in early adolescence (ages 11–15) and subsequent gambling and gambling problems (i.e. at-risk and problem gambling) by age 19. Design Prospective cohort design. Setting Urban communities in Baltimore, Maryland. Participants The sample consists of 310 predominately minority (87%) and low SES (70%) males followed from first grade to late adolescence. Measurements Impulsivity was measured using teacher ratings of classroom behavior. Self-reported gambling behavior was assessed using the South Oaks Gambling Screen-Revised for Adolescents (SOGS-RA). Findings Results from a conventional growth model suggest the intercept of the impulsivity development (as measured by the repeated assessments of impulsivity across the entire developmental period) was significantly associated with gambling. Results from a general growth mixture model evidenced two distinct trajectories: a high impulsivity trajectory (41% the sample) and a low impulsivity trajectory (59% of the sample). Despite its non-significant association with any gambling, heterogeneity in impulsivity development was significantly associated with gambling problems. Specifically, being in the high impulsivity trajectory doubled the odds of meeting criteria for at-risk or problem gambling (OR= 2.09[1.02, 4.27]) and tripled the odds of meeting criteria for problem gambling (OR=2.84[1.02, 7.91]) Conclusions Development in impulsivity is strongly associated with problem/at-risk gambling in adolescence among urban male youth. Findings highlight the importance of distinguishing gambling problems from any gambling when evaluating programs aimed at reducing youth gambling problems through reducing impulsivity. PMID:23130867

THE RELATIONSHIP BETWEEN MEASURES OF IMPULSIVITY AND ALCOHOL MISUSE: AN INTEGRATIVE STRUCTURAL EQUATION MODELING APPROACH

PubMed Central

Courtney, Kelly E.; Arellano, Ryan; Barkley-Levenson, Emily; Gálvan, Adriana; Poldrack, Russell A.; MacKillop, James; Jentsch, J. David; Ray, Lara A.

2011-01-01

Background Higher levels of impulsivity have been implicated in the development of alcohol use disorders. Recent findings suggest that impulsivity is not a unitary construct, highlighted by the diverse ways in which the various measures of impulsivity relate to alcohol use outcomes. This study simultaneously tested the following dimensions of impulsivity as determinants of alcohol use and alcohol problems: risky decision-making, self-reported risk attitudes, response inhibition, and impulsive decision-making. Method Participants were a community sample of non-treatment seeking problem drinkers (N = 158). Structural Equation Modeling (SEM) analyses employed behavioral measures of impulsive decision-making (Delay Discounting Task, DDT), response inhibition (Stop Signal Task, SST), and risky decision-making (Balloon Analogue Risk Task, BART), and a self-report measure of risk attitudes (Domain-specific Risk-attitude Scale, DOSPERT), as predictors of alcohol use and of alcohol-related problems in this sample. Results The model fit well, accounting for 38% of the variance in alcohol problems, and identified two impulsivity dimensions that significantly loaded onto alcohol outcomes: (1) impulsive decision-making, indexed by the DDT; and (2) risky decision-making, measured by the BART. Conclusions The impulsive decision-making dimension of impulsivity, indexed by the DDT, was the strongest predictor of alcohol use and alcohol pathology in this sample of problem drinkers. Unexpectedly, a negative relationship was found between risky decision-making and alcohol problems. The results highlight the importance of considering the distinct facets of impulsivity in order to elucidate their individual and combined effects on alcohol use initiation, escalation, and dependence. PMID:22091877

Small Launch Vehicle Concept Development for Affordable Multi-Stage Inline Configurations

NASA Technical Reports Server (NTRS)

Beers, Benjamin R.; Waters, Eric D.; Philips, Alan D.; Threet, Grady E., Jr.

2014-01-01

The Advanced Concepts Office at NASA's George C. Marshall Space Flight Center conducted a study of two configurations of a three stage, inline, liquid propellant small launch vehicle concept developed on the premise of maximizing affordability by targeting a specific payload capability range based on current industry demand. The initial configuration, NESC-1, employed liquid oxygen as the oxidizer and rocket propellant grade kerosene as the fuel in all three stages. The second and more heavily studied configuration, NESC-4, employed liquid oxygen and rocket propellant grade kerosene on the first and second stages and liquid oxygen and liquid methane fuel on the third stage. On both vehicles, sensitivity studies were first conducted on specific impulse and stage propellant mass fraction in order to baseline gear ratios and drive the focus of concept development. Subsequent sensitivity and trade studies on the NESC-4 configuration investigated potential impacts to affordability due to changes in gross liftoff weight and/or vehicle complexity. Results are discussed at a high level to understand the severity of certain sensitivities and how those trade studies conducted can either affect cost, performance or both.

Small Launch Vehicle Concept Development for Affordable Multi-Stage Inline Configurations

NASA Technical Reports Server (NTRS)

Beers, Benjamin R.; Waters, Eric D.; Philips, Alan D.; Threet, Grady E. Jr.

2013-01-01

The Advanced Concepts Office at NASA's George C. Marshall Space Flight Center conducted a study of two configurations of a three-stage, inline, liquid propellant small launch vehicle concept developed on the premise of maximizing affordability by targeting a specific payload capability range based on current industry demand. The initial configuration, NESC-1, employed liquid oxygen as the oxidizer and rocket propellant grade kerosene as the fuel in all three stages. The second and more heavily studied configuration, NESC-4, employed liquid oxygen and RP-1 on the first and second stages and liquid oxygen and liquid methane fuel on the third stage. On both vehicles, sensitivity studies were first conducted on specific impulse and stage propellant mass fraction in order to baseline gear ratios and drive the focus of concept development. Subsequent sensitivity and trade studies on the NESC-4 concept investigated potential impacts to affordability due to changes in gross liftoff weight and/or vehicle complexity. Results are discussed at a high level to understand the impact severity of certain sensitivities and how those trade studies conducted can either affect cost, performance, or both.

H2 arcjet performance mapping program

NASA Astrophysics Data System (ADS)

1992-01-01

Work performed during the period of Mar. 1991 to Jan. 1992 is reviewed. High power H2 arcjets are being considered for electric powered orbit transfer vehicles (EOTV). Mission analyses indicate that the overall arcjet thrust efficiency is very important since increasing the efficiency increases the thrust, and thereby reduces the total trip time for the same power. For example, increasing the thrust efficiency at the same specific impulse from 30 to 40 percent will reduce the trip time by 25 percent. For a 200 day mission, this equates to 50 days, which results in lower ground costs and less time during which the payload is dormant. Arcjet performance levels of 1200 seconds specific impulse (lsp) at 35 to 40 percent efficiency with lifetimes over 1000 hours are needed to support EOTV missions. Because of the potential very high efficiency levels, the objective of this program was to evaluate the ability of a scaled Giannini-style thruster to achieve the performance levels while operating at a reduced nominal power of 10 kW. To meet this objective, a review of past literature was conducted; scaling relationships were developed and applied to establish critical dimensions; a development thruster was designed with the aid of the plasma analysis model KARNAC and finite element thermal modeling; test hardware was fabricated; and a series of performance tests were conducted in RRC's Cell 11 vacuum chamber with its null-balance thrust stand.

The evolutionary development of high specific impulse electric thruster technology

NASA Technical Reports Server (NTRS)

Sovey, James S.; Hamley, John A.; Patterson, Michael J.; Rawlin, Vincent K.; Myers, Roger M.

1992-01-01

Electric propulsion flight and technology demonstrations conducted in the USA, Europe, Japan, China, and USSR are reviewed with reference to the major flight qualified electric propulsion systems. These include resistojets, ion thrusters, ablative pulsed plasma thrusters, stationary plasma thrusters, pulsed magnetoplasmic thrusters, and arcjets. Evolutionary mission applications are presented for high specific impulse electric thruster systems. The current status of arcjet, ion, and magnetoplasmadynamic thrusters and their associated power processor technologies are summarized.

Neurocognitive and psychiatric dimensions of “hot” impulsivity, but not “cool” impulsivity, predict HIV sexual risk behaviors among drug users in protracted abstinence

PubMed Central

Wilson, Michael J.; Vassileva, Jasmin

2016-01-01

Background Impulsivity is an important risk factor for HIV risky drug and sexual behaviors. Research identifies “hot” (i.e., affectively-mediated, reward-based) and “cool” (motoric, attentional, independent of context) neurocognitive and psychiatric dimensions of impulsivity, though the impact of specific drugs of abuse on these varieties of impulsivity remains an open question. Objectives The present study examined the associations of neurocognitive and psychiatric varieties of “hot” and “cool” impulsivity with measures of lifetime and recent sexual risk behaviors among users of different classes of drugs. Methods The study sample was comprised drug users in protracted (>1yr) abstinence: heroin monodependent (n=61), amphetamine monodependent (n=44), and polysubstance dependent (n= 73). “Hot” impulsivity was operationalized via neurocognitive tasks of reward-based decision-making and symptoms of psychopathy. “Cool” impulsivity was operationalized via neurocognitive tasks of response inhibition and symptoms of ADHD. Results “Hot” impulsivity was associated with sexual risk behaviors among heroin and amphetamine users in protracted abstinence, whereas “cool” impulsivity was not associated with sexual risk behaviors among any drug-using group. Neurocognitive “hot” impulsivity was associated with recent (past 30-day) sexual risk behaviors, whereas psychopathy was associated with sexual risk behaviors during more remote time-periods (past 6 month and lifetime) and mediated the association between heroin dependence and past 6-month sexual risk behaviors. Conclusion Assessments and interventions aimed at reducing sexual risk behaviors among drug users should focus on “hot” neurocognitive and psychiatric dimensions of impulsivity, such as decision-making and psychopathy. “Cool” dimensions of impulsivity such as response inhibition and ADHD were not related to sexual risk behaviors among drug users in protracted abstinence. PMID:26837332

A new generation of high performance engines for spacecraft propulsion

NASA Technical Reports Server (NTRS)

Rosenberg, Sanders D.; Schoenman, Leonard

1991-01-01

Experimental data validating advanced engine designs at three thrust levels (5, 15, and 100 lbF) is presented. All of the three engine designs considered employ a Moog bipropellant torque motor valve, platelet injector design, and iridium-lined rhenium combustion chamber. Attention is focused on the performance, robustness, duration, and flexibility characteristics of the engines. It is noted that the 5- and 15-lbF thrust engines can deliver a steady state specific impulse in excess of 310 lbF-sec/lbm at an area ratio of 150:1, while the 150-lbF thrust engines deliver a steady state specific impulse of 320 lbF-sec/lbm at an area ratio of 250:1. The hot-fire test results reveal specific impulse improvements of 15 to 25 sec over conventional fuel film cooled columbium chamber designs while operating at maximum chamber temperatures.

A Neurogenetic Approach to Impulsivity

PubMed Central

Congdon, Eliza; Canli, Turhan

2008-01-01

Impulsivity is a complex and multidimensional trait that is of interest to both personality psychologists and to clinicians. For investigators seeking the biological basis of personality traits, the use of neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) revolutionized personality psychology in less than a decade. Now, another revolution is under way, and it originates from molecular biology. Specifically, new findings in molecular genetics, the detailed mapping and the study of the function of genes, have shown that individual differences in personality traits can be related to individual differences within specific genes. In this article, we will review the current state of the field with respect to the neural and genetic basis of trait impulsivity. PMID:19012655

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

PubMed

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

2006-06-01

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.

The role of impulsivity in the association between childhood trauma and dissociative psychopathology: mediation versus moderation.

PubMed

Somer, Eli; Ginzburg, Karni; Kramer, Lilach

2012-03-30

Previous studies on survivors of childhood trauma documented associations between psychological dysregulation, impulsivity, and both behavioral and emotional manifestations of distress. Yet, the mechanism that links these variables remains unclear. The current study aims to examine the pattern of relations between a history of child abuse, impulsivity and dissociation. More specifically, it examines whether impulsivity serves as a moderator or mediator in the association between childhood trauma and dissociation. Eighty-one inpatients from the acute wards of two psychiatric hospitals participated in this study. Data were collected by clinician-administered questionnaires. A highly significant linear hierarchical regression analysis revealed that both psychiatric comorbidity and childhood trauma made unique contributions to the variance of dissociation. Yet, the significant association between childhood trauma and dissociation decreased when impulsivity was entered into the regression model. Our findings suggest that impulsivity mediates the association between childhood trauma and dissociative psychopathology and imply that the identification and treatment of impulsivity could be a potentially valuable clinical target in individuals with dissociative disorders. Copyright © 2012 Elsevier Ltd. All rights reserved.

Impulsive Choice in Mice Lacking Paternal Expression of Grb10 Suggests Intragenomic Conflict in Behavior.

PubMed

Dent, Claire L; Humby, Trevor; Lewis, Katie; Ward, Andrew; Fischer-Colbrie, Reiner; Wilkinson, Lawrence S; Wilkins, Jon F; Isles, Anthony R

2018-05-01

Imprinted genes are expressed from one parental allele only as a consequence of epigenetic events that take place in the mammalian germ line and are thought to have evolved through intragenomic conflict between parental alleles. We demonstrate, for the first time, oppositional effects of imprinted genes on brain and behavior. Specifically, we show that mice lacking paternal Grb10 make fewer impulsive choices, with no dissociable effects on a separate measure of impulsive action. Taken together with previous work showing that mice lacking maternal Nesp55 make more impulsive choices, this suggests that impulsive choice behavior is a substrate for the action of genomic imprinting. Moreover, the contrasting effect of these two genes suggests that impulsive choices are subject to intragenomic conflict and that maternal and paternal interests pull this behavior in opposite directions. Finally, these data may also indicate that an imbalance in expression of imprinted genes contributes to pathological conditions such as gambling and drug addiction, where impulsive behavior becomes maladaptive. Copyright © 2018 Dent et al.

Extended operating range of the 30-cm ion thruster with simplified power processor requirements

NASA Technical Reports Server (NTRS)

Rawlin, V. K.

1981-01-01

A two grid 30 cm diameter mercury ion thruster was operated with only six power supplies over the baseline J series thruster power throttle range with negligible impact on thruster performance. An analysis of the functional model power processor showed that the component mass and parts count could be reduced considerably and the electrical efficiency increased slightly by only replacing power supplies with relays. The input power, output thrust, and specific impulse of the thruster were then extended, still using six supplies, from 2660 watts, 0.13 newtons, and 2980 seconds to 9130 watts, 0.37 newtons, and 3820 seconds, respectively. Increases in thrust and power density enable reductions in the number of thrusters and power processors required for most missions. Preliminary assessments of the impact of thruster operation at increased thrust and power density on the discharge characteristics, performance, and lifetime of the thruster were also made.

Relations of Effortful Control, Reactive Undercontrol, and Anger to Chinese Children’s Adjustment

PubMed Central

Eisenberg, Nancy; Ma, Yue; Chang, Lei; Zhou, Qing; West, Stephen G.; Aiken, Leona

2006-01-01

The purpose of the study was to examine the zero-order and unique relations of effortful attentional and behavioral regulation, reactive impulsivity, and anger/frustration to Chinese first and second graders’ internalizing and externalizing symptoms, as well as the prediction of adjustment from the interaction of anger/frustration and effortful control or impulsivity. A parent and teacher reported on children’s anger/frustration, effortful control, and impulsivity; parents reported on children’s internalizing symptoms; and teachers and peers reported on children’s externalizing symptoms. Children were classified as relatively high on externalizing (or comorbid), internalizing, or nondisordered. High impulsivity and teacher-reported anger/frustration, and low effortful control, were associated with externalizing problems whereas low effortful control and high parent-reported anger were predictive of internalizing problems. Unique prediction from effortful and reactive control was obtained and these predictors (especially when reported by teachers) often interacted with anger/frustration when predicting problem behavior classification. PMID:17459176

Primer vector theory applied to the linear relative-motion equations. [for N-impulse space trajectory optimization

NASA Technical Reports Server (NTRS)

Jezewski, D.

1980-01-01

Prime vector theory is used in analyzing a set of linear relative-motion equations - the Clohessy-Wiltshire (C/W) equations - to determine the criteria and necessary conditions for an optimal N-impulse trajectory. The analysis develops the analytical criteria for improving a solution by: (1) moving any dependent or independent variable in the initial and/or final orbit, and (2) adding intermediate impulses. If these criteria are violated, the theory establishes a sufficient number of analytical equations. The subsequent satisfaction of these equations will result in the optimal position vectors and times of an N-impulse trajectory. The solution is examined for the specific boundary conditions of: (1) fixed-end conditions, two impulse, and time-open transfer; (2) an orbit-to-orbit transfer; and (3) a generalized renezvous problem.

Impulsivity, self-regulation,and pathological video gaming among youth: testing a mediation model.

PubMed

Liau, Albert K; Neo, Eng Chuan; Gentile, Douglas A; Choo, Hyekyung; Sim, Timothy; Li, Dongdong; Khoo, Angeline

2015-03-01

Given the potential negative mental health consequences of pathological video gaming, understanding its etiology may lead to useful treatment developments. The purpose of the study was to examine the influence of impulsive and regulatory processes on pathological video gaming. Study 1 involved 2154 students from 6 primary and 4 secondary schools in Singapore. Study 2 involved 191 students from 2 secondary schools. The results of study 1 and study 2 supported the hypothesis that self-regulation is a mediator between impulsivity and pathological video gaming. Specifically, higher levels of impulsivity was related to lower levels of self-regulation, which in turn was related to higher levels of pathological video gaming. The use of impulsivity and self-regulation in predicting pathological video gaming supports the dual-system model of incorporating both impulsive and reflective systems in the prediction of self-control outcomes. The study highlights the development of self-regulatory resources as a possible avenue for future prevention and treatment research. © 2011 APJPH.

Gray's Reinforcement Sensitivity Theory as a framework for research on personality-psychopathology associations.

PubMed

Bijttebier, Patricia; Beck, Ilse; Claes, Laurence; Vandereycken, Walter

2009-07-01

Gray's Reinforcement Sensitivity Theory (RST) presupposes individual differences in the sensitivity of basic brain systems that respond to punishing and reinforcing stimuli. These differences are thought to underlie the personality dimensions of anxiety and impulsivity, and to have relevance for psychopathology. The present article aims at reviewing RST-based research on personality-psychopathology associations. First, RST and its revisions are described and the link between RST systems and personality dimensions is discussed. Second, studies investigating associations between RST systems and specific types of psychopathology are summarized. Although the available research yields a rather consistent picture with respect to constellations of BIS/BAS sensitivity that are associated with specific types of psychopathology, it also provides a clear indication that much work remains to be done. The discussion section highlights several topics that deserve future research attention.

Post-error action control is neurobehaviorally modulated under conditions of constant speeded response.

PubMed

Soshi, Takahiro; Ando, Kumiko; Noda, Takamasa; Nakazawa, Kanako; Tsumura, Hideki; Okada, Takayuki

2014-01-01

Post-error slowing (PES) is an error recovery strategy that contributes to action control, and occurs after errors in order to prevent future behavioral flaws. Error recovery often malfunctions in clinical populations, but the relationship between behavioral traits and recovery from error is unclear in healthy populations. The present study investigated the relationship between impulsivity and error recovery by simulating a speeded response situation using a Go/No-go paradigm that forced the participants to constantly make accelerated responses prior to stimuli disappearance (stimulus duration: 250 ms). Neural correlates of post-error processing were examined using event-related potentials (ERPs). Impulsivity traits were measured with self-report questionnaires (BIS-11, BIS/BAS). Behavioral results demonstrated that the commission error for No-go trials was 15%, but PES did not take place immediately. Delayed PES was negatively correlated with error rates and impulsivity traits, showing that response slowing was associated with reduced error rates and changed with impulsivity. Response-locked error ERPs were clearly observed for the error trials. Contrary to previous studies, error ERPs were not significantly related to PES. Stimulus-locked N2 was negatively correlated with PES and positively correlated with impulsivity traits at the second post-error Go trial: larger N2 activity was associated with greater PES and less impulsivity. In summary, under constant speeded conditions, error monitoring was dissociated from post-error action control, and PES did not occur quickly. Furthermore, PES and its neural correlate (N2) were modulated by impulsivity traits. These findings suggest that there may be clinical and practical efficacy of maintaining cognitive control of actions during error recovery under common daily environments that frequently evoke impulsive behaviors.

Post-error action control is neurobehaviorally modulated under conditions of constant speeded response

PubMed Central

Soshi, Takahiro; Ando, Kumiko; Noda, Takamasa; Nakazawa, Kanako; Tsumura, Hideki; Okada, Takayuki

2015-01-01

Post-error slowing (PES) is an error recovery strategy that contributes to action control, and occurs after errors in order to prevent future behavioral flaws. Error recovery often malfunctions in clinical populations, but the relationship between behavioral traits and recovery from error is unclear in healthy populations. The present study investigated the relationship between impulsivity and error recovery by simulating a speeded response situation using a Go/No-go paradigm that forced the participants to constantly make accelerated responses prior to stimuli disappearance (stimulus duration: 250 ms). Neural correlates of post-error processing were examined using event-related potentials (ERPs). Impulsivity traits were measured with self-report questionnaires (BIS-11, BIS/BAS). Behavioral results demonstrated that the commission error for No-go trials was 15%, but PES did not take place immediately. Delayed PES was negatively correlated with error rates and impulsivity traits, showing that response slowing was associated with reduced error rates and changed with impulsivity. Response-locked error ERPs were clearly observed for the error trials. Contrary to previous studies, error ERPs were not significantly related to PES. Stimulus-locked N2 was negatively correlated with PES and positively correlated with impulsivity traits at the second post-error Go trial: larger N2 activity was associated with greater PES and less impulsivity. In summary, under constant speeded conditions, error monitoring was dissociated from post-error action control, and PES did not occur quickly. Furthermore, PES and its neural correlate (N2) were modulated by impulsivity traits. These findings suggest that there may be clinical and practical efficacy of maintaining cognitive control of actions during error recovery under common daily environments that frequently evoke impulsive behaviors. PMID:25674058

The energy spectra of solar flare electrons

NASA Technical Reports Server (NTRS)

Evenson, P. A.; Hovestadt, D.; Meyer, P.; Moses, D.

1985-01-01

A survey of 50 electron energy spectra from .1 to 100 MeV originating from solar flares was made by the combination of data from two spectrometers onboard the International Sun Earth Explorer-3 spacecraft. The observed spectral shapes of flare events can be divided into two classes through the criteria of fit to an acceleration model. This standard two step acceleration model, which fits the spectral shape of the first class of flares, involves an impulsive step that accelerates particles up to 100 keV and a second step that further accelerates these particles up to 100 MeV by a single shock. This fit fails for the second class of flares that can be characterized as having excessively hard spectra above 1 MeV relative to the predictions of the model. Correlations with soft X-ray and meter radio observations imply that the acceleration of the high energy particles in the second class of flares is dominated by the impulsive phase of the flares.

Primer-optimized results and trends for circular phasing and other circle-to-circle impulsive coplanar rendezvous

NASA Astrophysics Data System (ADS)

Sandrik, Suzannah

Optimal solutions to the impulsive circular phasing problem, a special class of orbital maneuver in which impulsive thrusts shift a vehicle's orbital position by a specified angle, are found using primer vector theory. The complexities of optimal circular phasing are identified and illustrated using specifically designed Matlab software tools. Information from these new visualizations is applied to explain discrepancies in locally optimal solutions found by previous researchers. Two non-phasing circle-to-circle impulsive rendezvous problems are also examined to show the applicability of the tools developed here to a broader class of problems and to show how optimizing these rendezvous problems differs from the circular phasing case.

Theoretical analysis of the electrical aspects of the basic electro-impulse problem in aircraft de-icing applications

NASA Technical Reports Server (NTRS)

Henderson, R. A.; Schrag, R. L.

1986-01-01

A summary of modeling the electrical system aspects of a coil and metal target configuration resembling a practical electro-impulse deicing (EIDI) installation, and a simple circuit for providing energy to the coil, was presented. The model was developed in sufficient theoretical detail to allow the generation of computer algorithms for the current in the coil, the magnetic induction on both surfaces of the target, the force between the coil and target, and the impulse delivered to the target. These algorithms were applied to a specific prototype EIDI test system for which the current, magnetic fields near the target surfaces, and impulse were previously measured.

Coaxial plasma thrusters for high specific impulse propulsion

NASA Technical Reports Server (NTRS)

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

1991-01-01

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.

High energy-density liquid rocket fuel performance

NASA Technical Reports Server (NTRS)

Rapp, Douglas C.

1990-01-01

A fuel performance database of liquid hydrocarbons and aluminum-hydrocarbon fuels was compiled using engine parametrics from the Space Transportation Engine Program as a baseline. Propellant performance parameters are introduced. General hydrocarbon fuel performance trends are discussed with respect to hydrogen-to-carbon ratio and heat of formation. Aluminum-hydrocarbon fuel performance is discussed with respect to aluminum metal loading. Hydrocarbon and aluminum-hydrocarbon fuel performance is presented with respect to fuel density, specific impulse, and propellant density specific impulse.

Performance characterization of a low power hydrazine arcjet

NASA Technical Reports Server (NTRS)

Knowles, S. C.; Smith, W. W.; Curran, F. M.; Haag, T. W.

1987-01-01

Hydrazine arcjets, which offer substantial performance advantages over alternatives in geosynchronous satellite stationkeeping applications, have undergone startup, materials compatibility, lifetime, and power conditioning unit design issues. Devices in the 1000-3000 W output range have been characterized for several different electrode configurations. Constrictor length and diameter, electrode gap setting, and vortex strength have been parametrically studied in order to ascertain the influence of each on specific impulse and efficiency; specific impulse levels greater than 700 sec have been achieved.

Propellant production from the Martian atmosphere

NASA Technical Reports Server (NTRS)

Bowles, J. V.; Tauber, M. E.; Anagnost, A. J.; Whittaker, T.

1992-01-01

Results are presented from a calculation of the specific impulses that can be generated through the combustion of cryogenic CO and O2 over a range of fuel/oxidizer ratios, chamber pressures, nozzle expansion ratios, freestream pressures representative of Mars, and the limiting conditions of equilibrium and frozen nozzle flow. For an expansion ratio of 80 and 100-atm. chamber pressure, a specific impulse of 298 sec was obtained; this is comparable to the best solid rocket propellants.

Impulsivity in adolescents with major depressive disorder: A comparative tunisian study.

PubMed

Khemakhem, Khaoula; Boudabous, Jaweher; Cherif, Leila; Ayadi, Hela; Walha, Adel; Moalla, Yousr; Hadjkacem, Imen; Ghribi, Farhat

2017-08-01

The association between impulsivity and depressive disorders in adolescence has been little studied at the literature and in our country, yet impulsivity is a major risk factor for suicide. Thus we aimed on this study to evaluate impulsivity in 25 adolescents with Major Depressive Disorder MDD compared to a control sample and to analyze the correlations between impulsivity and clinical features of MDD. Employing a matched case-control design, participants included 25 adolescents with MDD and 75 controls. We have administered the Barratt Impulsivity Scale BIS-11 for the two groups to evaluate impulsivity. Semi structured interviews according DSM 5 criteria were conducted for adolescents with MDD. The Child Depressive Inventory CDI was used to measure depressive symptoms in the control sample. Adolescents with MDD were more impulsive compared to controls according to the BIS-11 in its three domains: motor (24.96±6.26 against 20.6±4.84; p=0.000), attentional (20.88±5.03 against 16.64±3.2; p=0.000) and non planning (28.2±7.26 against 24.44±4.32; p=0.02). Impulsivity was not correlated with clinical features of MDD (suicide attempts, psychiatric comorbidities, antidepressant medication …). Adolescents with MDD seem to be more impulsive than control subjects regardless their clinical features. Whether it is a specific characteristic or a symptom among others of MDD, impulsivity predicts health-related behaviors and associated damage that need to be detected and prevented in time. Copyright © 2017 Elsevier B.V. All rights reserved.

Serotonin Depletion Induces ‘Waiting Impulsivity' on the Human Four-Choice Serial Reaction Time Task: Cross-Species Translational Significance

PubMed Central

Worbe, Yulia; Savulich, George; Voon, Valerie; Fernandez-Egea, Emilio; Robbins, Trevor W

2014-01-01

Convergent results from animal and human studies suggest that reducing serotonin neurotransmission promotes impulsive behavior. Here, serotonin depletion was induced by the dietary tryptophan depletion procedure (TD) in healthy volunteers to examine the role of serotonin in impulsive action and impulsive choice. We used a novel translational analog of a rodent 5-choice serial reaction time task (5-CSRTT)— the human 4-CSRTT—and a reward delay-discounting questionnaire to measure effects on these different forms of ‘waiting impulsivity'. There was no effect of TD on impulsive choice as indexed by the reward delay-discounting questionnaire. However, TD significantly increased 4-CSRTT premature responses (or impulsive action), which is remarkably similar to the previous findings of effect of serotonin depletion on rodent 5-CSRTT performance. Moreover, the increased premature responding in TD correlated significantly with individual differences on the motor impulsivity subscale of the Barratt Impulsivity Scale. TD also improved the accuracy of performance and speeded responding, possibly indicating enhanced attention and reward processing. The results suggest: (i) the 4-CSRTT will be a valuable addition to the tests already available to measure impulsivity in humans in a direct translational analog of a test extensively used in rodents; (ii) TD in humans produces a qualitatively similar profile of effects to those in rodents (ie, enhancing premature responding), hence supporting the conclusion that TD in humans exerts at least some of its effects on central serotonin; and (iii) this manipulation of serotonin produces dissociable effects on different measures of impulsivity, suggesting considerable specificity in its modulatory role. PMID:24385133

Neurocognitive and psychiatric dimensions of hot, but not cool, impulsivity predict HIV sexual risk behaviors among drug users in protracted abstinence.

PubMed

Wilson, Michael J; Vassileva, Jasmin

2016-03-01

Impulsivity is an important risk factor for HIV risky drug and sexual behaviors. Research identifies hot (i.e. affectively-mediated, reward-based) and cool (motoric, attentional, independent of context) neurocognitive and psychiatric dimensions of impulsivity, though the impact of specific drugs of abuse on these varieties of impulsivity remains an open question. The present study examined the associations of neurocognitive and psychiatric varieties of hot and cool impulsivity with measures of lifetime and recent sexual risk behaviors among users of different classes of drugs. The study sample was comprised of drug users in protracted (> 1 year) abstinence: heroin mono-dependent (n = 61), amphetamine mono-dependent (n = 44), and polysubstance dependent (n = 73). Hot impulsivity was operationalized via neurocognitive tasks of reward-based decision-making and symptoms of psychopathy. Cool impulsivity was operationalized via neurocognitive tasks of response inhibition and symptoms of attention deficit/hyperactivity disorder (ADHD). Hot impulsivity was associated with sexual risk behaviors among heroin and amphetamine users in protracted abstinence, whereas cool impulsivity was not associated with sexual risk behaviors among any drug-using group. Neurocognitive hot impulsivity was associated with recent (past 30-day) sexual risk behaviors, whereas psychopathy was associated with sexual risk behaviors during more remote time-periods (past 6 month and lifetime) and mediated the association between heroin dependence and past 6-month sexual risk behaviors. Assessments and interventions aimed at reducing sexual risk behaviors among drug users should focus on hot neurocognitive and psychiatric dimensions of impulsivity, such as decision-making and psychopathy. Cool dimensions of impulsivity such as response inhibition and ADHD were not related to sexual risk behaviors among drug users in protracted abstinence.

Trait impulsivity and impaired prefrontal impulse inhibition function in adolescents with internet gaming addiction revealed by a Go/No-Go fMRI study.

PubMed

Ding, Wei-na; Sun, Jin-hua; Sun, Ya-Wen; Chen, Xue; Zhou, Yan; Zhuang, Zhi-guo; Li, Lei; Zhang, Yong; Xu, Jian-rong; Du, Ya-song

2014-05-30

Recent studies suggest that Internet gaming addiction (IGA) is an impulse disorder, or is at least related to impulse control disorders. In the present study, we hypothesized that different facets of trait impulsivity may be specifically linked to the brain regions with impaired impulse inhibition function in IGA adolescents. Seventeen adolescents with IGA and seventeen healthy controls were scanned during performance of a response-inhibition Go/No-Go task using a 3.0 T MRI scanner. The Barratt Impulsiveness Scale (BIS)-11 was used to assess impulsivity. There were no differences in the behavioral performance on the Go/No-Go task between the groups. However, the IGA group was significantly hyperactive during No-Go trials in the left superior medial frontal gyrus, right anterior cingulate cortex, right superior/middle frontal gyrus, left inferior parietal lobule, left precentral gyrus, and left precuneus and cuneus. Further, the bilateral middle temporal gyrus, bilateral inferior temporal gyrus, and right superior parietal lobule were significantly hypoactive during No-Go trials. Activation of the left superior medial frontal gyrus was positively associated with BIS-11 and Chen Internet Addiction Scale (CIAS) total score across IGA participants. Our data suggest that the prefrontal cortex may be involved in the circuit modulating impulsivity, while its impaired function may relate to high impulsivity in adolescents with IGA, which may contribute directly to the Internet addiction process.

Trait impulsivity and impaired prefrontal impulse inhibition function in adolescents with internet gaming addiction revealed by a Go/No-Go fMRI study

PubMed Central

2014-01-01

Background Recent studies suggest that Internet gaming addiction (IGA) is an impulse disorder, or is at least related to impulse control disorders. In the present study, we hypothesized that different facets of trait impulsivity may be specifically linked to the brain regions with impaired impulse inhibition function in IGA adolescents. Methods Seventeen adolescents with IGA and seventeen healthy controls were scanned during performance of a response-inhibition Go/No-Go task using a 3.0 T MRI scanner. The Barratt Impulsiveness Scale (BIS)-11 was used to assess impulsivity. Results There were no differences in the behavioral performance on the Go/No-Go task between the groups. However, the IGA group was significantly hyperactive during No-Go trials in the left superior medial frontal gyrus, right anterior cingulate cortex, right superior/middle frontal gyrus, left inferior parietal lobule, left precentral gyrus, and left precuneus and cuneus. Further, the bilateral middle temporal gyrus, bilateral inferior temporal gyrus, and right superior parietal lobule were significantly hypoactive during No-Go trials. Activation of the left superior medial frontal gyrus was positively associated with BIS-11 and Chen Internet Addiction Scale (CIAS) total score across IGA participants. Conclusions Our data suggest that the prefrontal cortex may be involved in the circuit modulating impulsivity, while its impaired function may relate to high impulsivity in adolescents with IGA, which may contribute directly to the Internet addiction process. PMID:24885073

Modification of impulse generation during piqué turns with increased rotational demands.

PubMed

Zaferiou, Antonia M; Wilcox, Rand R; McNitt-Gray, Jill L

2016-06-01

During initiation of a piqué turn, a dancer generates impulse to achieve the desired lateral translation and whole-body rotation. The goal of this study was to determine how individuals regulate impulse generation when initiating piqué turns with increased rotational demands. Skilled dancers (n=10) performed single (∼360°) and double (∼720°) piqué turns from a stationary position. Linear and angular impulse generated by the push and turn legs were quantified using ground reaction forces and compared across turn conditions as a group and within a dancer using probability-based statistical methods. The results indicate that as the rotation demands of the piqué turn increased, the net angular impulse generated increased whereas net lateral impulse decreased. Early during turn initiation, the free moment contributed to angular impulse generation. Later during turn initiation, horizontal reaction forces were controlled to generate angular impulse. As rotational demands increased, the moment applied increased primarily from redirection of the horizontal reaction force (RFh) at the push leg and a combination of RFh magnitude and moment arm increases at the turn leg. RFh at each leg were coordinated to limit unwanted net linear impulse. Knowledge of observed subject-specific mechanisms is important to inform the design of turning performance training tools. Copyright © 2016 Elsevier B.V. All rights reserved.

Direct and Indirect Effects of Impulsivity Traits on Drinking and Driving in Young Adults

PubMed Central

Treloar, Hayley R.; Morris, David H.; Pedersen, Sarah L.; McCarthy, Denis M.

2012-01-01

Objective: Impulsivity is strongly associated with alcohol-related risk-taking behavior, and this association has been found to be mediated by alcohol cognitions. The current study expanded this literature by comparing the relative association of distinct impulsivity traits with a specific risky behavior—drinking and driving. We then tested whether drinking-and-driving expectancies uniquely mediated this relation over and above other cognitions about alcohol and drinking and driving. Method: College student drivers (n = 816; 53.6% women) completed a paper-and-pencil survey in small groups. Self-report measures assessed alcohol use, impulsivity traits, alcohol expectancies, drinking-and-driving cognitions (i.e., expectancies, attitudes, beliefs), and drinking and driving. Results: Although all impulsivity traits were correlated with drinking and driving, only urgency uniquely contributed to drinking and driving. Indirect effect tests indicated that drinking-and-driving convenience expectancies partially mediated this association as well as that between (lack of) perseverance and drinking and driving. These results remained significant after controlling for alcohol expectancies and other drinking-and-driving cognitions. Conclusions: These findings highlight the importance of distinguishing among impulsivity traits to improve theoretical models of the processes by which personality leads to specific alcohol-related consequences. In addition, results extend previous research by providing evidence for the unique importance of expectancies regarding the convenience of drinking and driving over and above more global alcohol expectancies and other drinking-and-driving cognitions. PMID:22846243

Sex-specific attenuation of impulsive action by progesterone in a Go/No-go task for cocaine in rats

PubMed Central

Swalve, Natashia; Smethells, John R.; Younk, Rebecca; Mitchell, Jared; Dougen, Ben; Carroll, Marilyn E.

2018-01-01

Rationale Previous work indicated that progesterone (PRO) reduced impulsive choice for cocaine in female but not male rats (Smethells et al. 2016). Impulsive action, typically measured by responding for a reinforcer during a signaled period of nonavailability of natural reinforcers, predicts initiation and escalation of drug use in animals and humans. The present study examined impulsive action for cocaine using progesterone (PRO) in male and female rats trained on a Go/No-go task. Objective Rats were trained on a Go/No-go task to respond for cocaine infusions (0.4 mg/kg/inf). During the “Go” component, responding was reinforced on a VI 30-s schedule; whereas, during the “No-Go” component withholding a response was reinforced on a differential reinforcement of other behavior (DRO) 30-s schedule. A response during the No-go component reset the DRO timer and served as a measure of impulsive action. After baseline responding was established, rats were pretreated with vehicle (VEH) or PRO (0.5 mg/kg), and DRO resets and responding during the Go component for cocaine were compared in males vs. females. Results DRO resets were significantly lower following PRO treatment compared to VEH in female, but not male, rats. Response rates and overall infusions during the Go component were not significantly altered by PRO in either females or males. Conclusion Treatment with PRO resulted in a sex-specific reduction in impulsive action for cocaine, while not affecting cocaine self-administration. PMID:29018893

The role of affect-driven impulsivity in gambling cognitions: A convenience-sample study with a Spanish version of the Gambling-Related Cognitions Scale.

PubMed

Del Prete, Francesco; Steward, Trevor; Navas, Juan F; Fernández-Aranda, Fernando; Jiménez-Murcia, Susana; Oei, Tian P S; Perales, José C

2017-03-01

Background and aims Abnormal cognitions are among the most salient domain-specific features of gambling disorder. The aims of this study were: (a) to examine and validate a Spanish version of the Gambling-Related Cognitions Scale (GRCS; Raylu & Oei, 2004) and (b) to examine associations between cognitive distortion levels, impulsivity, and gambling behavior. Methods This study first recruited a convenience sample of 500 adults who had gambled during the previous year. Participants were assessed using the Spanish version of GRCS (GRCS-S) questionnaire, the UPPS-P impulsivity questionnaire, measures of gambling behavior, and potentially relevant confounders. Robust confirmatory factor analysis methods on half the sample were used to select the best models from a hypothesis-driven set. The best solutions were validated on the other half, and the resulting factors were later correlated with impulsivity dimensions (in the whole n = 500 factor analysis sample) and clinically relevant gambling indices (in a separate convenience sample of 137 disordered and non-disordered gamblers; validity sample). Results This study supports the original five-factor model, suggests an alternative four-factor solution, and confirms the psychometric soundness of the GRCS-S. Importantly, cognitive distortions consistently correlated with affect- or motivation-driven aspects of impulsivity (urgency and sensation seeking), but not with cognitive impulsivity (lack of premeditation and lack of perseverance). Discussion and conclusions Our findings suggest that the GRCS-S is a valid and reliable instrument to identify gambling cognitions in Spanish samples. Our results expand upon previous research signaling specific associations between gambling-related distortions and affect-driven impulsivity in line with models of motivated reasoning.

A Serious Videogame as an Additional Therapy Tool for Training Emotional Regulation and Impulsivity Control in Severe Gambling Disorder

PubMed Central

Tárrega, Salomé; Castro-Carreras, Laia; Fernández-Aranda, Fernando; Granero, Roser; Giner-Bartolomé, Cristina; Aymamí, Neus; Gómez-Peña, Mónica; Santamaría, Juan J.; Forcano, Laura; Steward, Trevor; Menchón, José M.; Jiménez-Murcia, Susana

2015-01-01

Background: Gambling disorder (GD) is characterized by a significant lack of self-control and is associated with impulsivity-related personality traits. It is also linked to deficits in emotional regulation and frequently co-occurs with anxiety and depression symptoms. There is also evidence that emotional dysregulation may play a mediatory role between GD and psychopathological symptomatology. Few studies have reported the outcomes of psychological interventions that specifically address these underlying processes. Objectives: To assess the utility of the Playmancer platform, a serious video game, as an additional therapy tool in a CBT intervention for GD, and to estimate pre-post changes in measures of impulsivity, anger expression and psychopathological symptomatology. Method: The sample comprised a single group of 16 male treatment-seeking individuals with severe GD diagnosis. Therapy intervention consisted of 16 group weekly CBT sessions and, concurrently, 10 additional weekly sessions of a serious video game. Pre-post treatment scores on South Oaks Gambling Screen (SOGS), Barratt Impulsiveness Scale (BIS-11), I7 Impulsiveness Questionnaire (I7), State-Trait Anger Expression Inventory 2 (STAXI-2), Symptom Checklist-Revised (SCL-90-R), State-Trait Anxiety Inventory (STAI-S-T), and Novelty Seeking from the Temperament and Character Inventory-Revised (TCI-R) were compared. Results: After the intervention, significant changes were observed in several measures of impulsivity, anger expression and other psychopathological symptoms. Dropout and relapse rates during treatment were similar to those described in the literature for CBT. Conclusion: Complementing CBT interventions for GD with a specific therapy approach like a serious video game might be helpful in addressing certain underlying factors which are usually difficult to change, including impulsivity and anger expression. PMID:26617550

The role of affect-driven impulsivity in gambling cognitions: A convenience-sample study with a Spanish version of the Gambling-Related Cognitions Scale

PubMed Central

Del Prete, Francesco; Steward, Trevor; Navas, Juan F.; Fernández-Aranda, Fernando; Jiménez-Murcia, Susana; Oei, Tian P. S.; Perales, José C.

2017-01-01

Background and aims Abnormal cognitions are among the most salient domain-specific features of gambling disorder. The aims of this study were: (a) to examine and validate a Spanish version of the Gambling-Related Cognitions Scale (GRCS; Raylu & Oei, 2004) and (b) to examine associations between cognitive distortion levels, impulsivity, and gambling behavior. Methods This study first recruited a convenience sample of 500 adults who had gambled during the previous year. Participants were assessed using the Spanish version of GRCS (GRCS-S) questionnaire, the UPPS-P impulsivity questionnaire, measures of gambling behavior, and potentially relevant confounders. Robust confirmatory factor analysis methods on half the sample were used to select the best models from a hypothesis-driven set. The best solutions were validated on the other half, and the resulting factors were later correlated with impulsivity dimensions (in the whole n = 500 factor analysis sample) and clinically relevant gambling indices (in a separate convenience sample of 137 disordered and non-disordered gamblers; validity sample). Results This study supports the original five-factor model, suggests an alternative four-factor solution, and confirms the psychometric soundness of the GRCS-S. Importantly, cognitive distortions consistently correlated with affect- or motivation-driven aspects of impulsivity (urgency and sensation seeking), but not with cognitive impulsivity (lack of premeditation and lack of perseverance). Discussion and conclusions Our findings suggest that the GRCS-S is a valid and reliable instrument to identify gambling cognitions in Spanish samples. Our results expand upon previous research signaling specific associations between gambling-related distortions and affect-driven impulsivity in line with models of motivated reasoning. PMID:28118729

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

PubMed Central

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

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

A Serious Videogame as an Additional Therapy Tool for Training Emotional Regulation and Impulsivity Control in Severe Gambling Disorder.

PubMed

Tárrega, Salomé; Castro-Carreras, Laia; Fernández-Aranda, Fernando; Granero, Roser; Giner-Bartolomé, Cristina; Aymamí, Neus; Gómez-Peña, Mónica; Santamaría, Juan J; Forcano, Laura; Steward, Trevor; Menchón, José M; Jiménez-Murcia, Susana

2015-01-01

Gambling disorder (GD) is characterized by a significant lack of self-control and is associated with impulsivity-related personality traits. It is also linked to deficits in emotional regulation and frequently co-occurs with anxiety and depression symptoms. There is also evidence that emotional dysregulation may play a mediatory role between GD and psychopathological symptomatology. Few studies have reported the outcomes of psychological interventions that specifically address these underlying processes. To assess the utility of the Playmancer platform, a serious video game, as an additional therapy tool in a CBT intervention for GD, and to estimate pre-post changes in measures of impulsivity, anger expression and psychopathological symptomatology. The sample comprised a single group of 16 male treatment-seeking individuals with severe GD diagnosis. Therapy intervention consisted of 16 group weekly CBT sessions and, concurrently, 10 additional weekly sessions of a serious video game. Pre-post treatment scores on South Oaks Gambling Screen (SOGS), Barratt Impulsiveness Scale (BIS-11), I7 Impulsiveness Questionnaire (I7), State-Trait Anger Expression Inventory 2 (STAXI-2), Symptom Checklist-Revised (SCL-90-R), State-Trait Anxiety Inventory (STAI-S-T), and Novelty Seeking from the Temperament and Character Inventory-Revised (TCI-R) were compared. After the intervention, significant changes were observed in several measures of impulsivity, anger expression and other psychopathological symptoms. Dropout and relapse rates during treatment were similar to those described in the literature for CBT. Complementing CBT interventions for GD with a specific therapy approach like a serious video game might be helpful in addressing certain underlying factors which are usually difficult to change, including impulsivity and anger expression.

Emotional Lessons: Out on the Tundra, Kids Learn To Better Understand Their Own and Others' Feelings.

ERIC Educational Resources Information Center

Sherman, Lee

1999-01-01

A nationally acclaimed antiviolence program, Second Step teaches three basic skills needed for living peacefully in society: empathy, impulse control, and anger management. In Bethel (Alaska), where student gunfire killed a student and principal in 1997, Second Step is used enthusiastically, having been modified to fit Yupik Eskimo culture and…

The Relationship between Impulsivity and Internet Gaming Disorder in Young Adults: Mediating Effects of Interpersonal Relationships and Depression.

PubMed

Ryu, Hyera; Lee, Ji-Yoon; Choi, Aruem; Park, Sunyoung; Kim, Dai-Jin; Choi, Jung-Seok

2018-03-06

Background: This study aimed to explore relationships between impulsivity, interpersonal relationships, depression, and Internet Gaming Disorder (IGD) symptoms. Methods: A total of 118 young adults participated in this study: 67 IGD patients who met five or more of the DSM-5 diagnostic criteria for IGD and 56 healthy controls. We administered questionnaires to assess IGD symptoms (Young's Internet Addiction Test; Y-IAT), impulsivity (Barratt Impulsiveness Scale; BIS-11), interpersonal relationship (Relationship Change Scale; RCS), and depression (Beck Depression Inventory; BDI). We used PROCESS macro in SPSS to perform mediation analysis. Results: IGD symptom was positively related to depression and impulsivity, and negatively related to the quality of interpersonal relationships. Mediation analysis revealed full mediation effects of interpersonal relationships and depression on the association between impulsivity and IGD symptoms in the IGD group. Specifically, even after adjusting for gender as a covariate, high impulsivity was associated with greater difficulty with interpersonal relationships; which further affected depression and increased the risk of IGD. Conclusions: These results demonstrate the importance of early intervention in IGD patients, particularly in young adults with high impulsivity. When intervening in adults' IGD, we should consider not only individual factors (e.g., depression) but also socioenvironmental factors (e.g., interpersonal relationships).

The Relationship between Impulsivity and Internet Gaming Disorder in Young Adults: Mediating Effects of Interpersonal Relationships and Depression

PubMed Central

Ryu, Hyera; Lee, Ji-Yoon; Choi, Aruem; Park, Sunyoung; Kim, Dai-Jin

2018-01-01

Background: This study aimed to explore relationships between impulsivity, interpersonal relationships, depression, and Internet Gaming Disorder (IGD) symptoms. Methods: A total of 118 young adults participated in this study: 67 IGD patients who met five or more of the DSM-5 diagnostic criteria for IGD and 56 healthy controls. We administered questionnaires to assess IGD symptoms (Young’s Internet Addiction Test; Y-IAT), impulsivity (Barratt Impulsiveness Scale; BIS-11), interpersonal relationship (Relationship Change Scale; RCS), and depression (Beck Depression Inventory; BDI). We used PROCESS macro in SPSS to perform mediation analysis. Results: IGD symptom was positively related to depression and impulsivity, and negatively related to the quality of interpersonal relationships. Mediation analysis revealed full mediation effects of interpersonal relationships and depression on the association between impulsivity and IGD symptoms in the IGD group. Specifically, even after adjusting for gender as a covariate, high impulsivity was associated with greater difficulty with interpersonal relationships; which further affected depression and increased the risk of IGD. Conclusions: These results demonstrate the importance of early intervention in IGD patients, particularly in young adults with high impulsivity. When intervening in adults’ IGD, we should consider not only individual factors (e.g., depression) but also socioenvironmental factors (e.g., interpersonal relationships). PMID:29509708

The role of impulsivity in self-mutilators, suicide ideators and suicide attempters - a study of 1265 male incarcerated individuals.

PubMed

Carli, Vladimir; Jovanović, Nikolina; Podlesek, Anja; Roy, Alec; Rihmer, Zoltan; Maggi, Stefania; Marusic, Dragan; Cesaro, Caterina; Marusic, Andrej; Sarchiapone, Marco

2010-06-01

We explored differences between high and low-impulsive incarcerated individuals in the context of lifetime self-mutilation, suicide ideation and suicide attempt. A total of 1265 males detained in Italian penitentiary institutions were studied between January 2006 and December 2008. The study raters were specifically trained to discriminate between suicide attempters, ideators and self-mutilators. Participants completed the Barratt Impulsivity Scale, Childhood Trauma Questionnaire (CTQ), Eysenck Personality Questionnaire (EPQ), Connor-Davidson Resilience Scale (CD-RISC), Brown-Goodwin Assessment for Lifetime History of Aggression (BGLHA) and Buss and Durkee Hostility Inventory (BDHI). Based on BIS 7 total score distribution, two extreme quarters - high-impulsive group (n=306) and low-impulsive group (n=285) - were compared. Over 42% of participants had lifetime suicide ideation, 13% attempted suicide and 17% were self-mutilators. High-impulsive subjects were younger, more often single and with more prominent psychoticism, extraversion, aggression, hostility and resilience capacity. They were more frequently diagnosed with substance use disorders and engaged in self-mutilating behaviour. There was no difference in the rate of suicide attempts between the two groups. Although high-impulsive subjects were more prone to suicidal behaviour, it was not predicted by higher impulsivity when other psychological variables were accounted for. Copyright 2010 Elsevier B.V. All rights reserved.

Profiles of drug addicts in relation to personality variables and disorders.

PubMed

Carou, María; Romero, Estrella; Luengo, Mª Ángeles

2016-10-07

In recent decades, research has identified a set of impulsive/disinhibited personality variables closely associated with drug addiction. As well as this, disorders linked with these variables, such as ADHD and personality disorders, are being closely studied in the field of drug addiction. Although much knowledge has been accumulated about the relation of these variables and disorders taken separately, less is known about how these constructs allow identify-specific profiles within the drug dependent population to be identified. This work, on the basis of data collected on a sample of drug addicts in treatment, analyzes how impulsiveness, sensation seeking, self-control, ADHD and personality disorders contribute to identifying specific profiles of addicts. Cluster analysis allowed two profiles to be outlined according to these personality and psychopathology characteristics. Self-control, impulsiveness, impulsive and antisocial personality disorders, as well as scores in ADHD, emerge as the variables that contribute more to profile differentiation. One of these profiles (56.1% of participants) with a high disinhibition pattern, is associated with severe indicators of consumption and criminal career patterns. These results allow us to emphasize the role of personality and impulsiveness-related disorders in the identification of distinctive profiles within the addict population, and suggest the need to generate treatment strategies adapted to personal/psychopathology configurations of drug addicts.

Testing and evaluation of the LES-6 pulsed plasma thruster by means of a torsion pendulum system

NASA Technical Reports Server (NTRS)

Hamidian, J. P.; Dahlgren, J. B.

1973-01-01

Performance characteristics of the LES-6 pulsed plasma thruster over a range of input conditions were investigated by means of a torsion pendulum system. Parameters of particular interest included the impulse bit and time average thrust (and their repeatability), specific impulse, mass ablated per discharge, specific thrust, energy per unit area, efficiency, and variation of performance with ignition command rate. Intermittency of the thruster as affected by input energy and igniter resistance were also investigated. Comparative experimental data correlation with the data presented. The results of these tests indicate that the LES-6 thruster, with some identifiable design improvements, represents an attractive reaction control thruster for attitude contol applications on long-life spacecraft requiring small metered impulse bits for precise pointing control of science instruments.

The ENABLER—based on proven NERVA technology

NASA Astrophysics Data System (ADS)

Livingston, Julie M.; Pierce, Bill L.

1991-01-01

The ENABLER reactor for use in a nuclear thermal propulsion engine uses the technology developed in the NERVA/Rover program, updated to incorporate advances in the technology. Using composite fuel, higher power densities per fuel element, improved radiation resistant control components and the advancements in use of carbon-carbon materials; the ENABLER can provide a specific impulse of 925 seconds, an engine thrust to weight (excluding reactor shield) approaching five, an improved initial Mass In Low Earth Orbit (IMLEO) and a consequent reduction in launch costs and logistics problems. This paper describes the 75,000 lbs thrust ENABLER design which is a low cost, low risk approach to meeting tomorrow's space propulsion needs.

High temperature thruster technology for spacecraft propulsion

NASA Technical Reports Server (NTRS)

Schneider, Steven J.

1991-01-01

A technology program intended to develop high-temperature oxidation-resistant thrusters for spacecraft applications is considered. The program will provide the requisite material characterizations and fabrication to incorporate iridium coated rhenium material into small rockets for spacecraft propulsion. This material increases the operating temperature of thrusters to 2200 C, a significant increase over the 1400 C of the silicide-coated niobium chambers currently used. Stationkeeping class 22 N engines fabricated from iridium-coated rhenium have demonstrated steady state specific impulses 20-25 seconds higher than niobium chambers. These improved performances are obtained by reducing or eliminating the fuel film cooling requirements in the combustion chamber while operating at the same overall mixture ratio as conventional engines.

Predicting impulsive self-injurious behavior in a sample of adult women.

PubMed

Black, Emma B; Mildred, Helen

2013-01-01

Different types of self-injury have been classified as reflecting impulsive and compulsive characteristics (article by Simeon and Favazza [Self-injurious Behaviors: Assessment and Treatment {pp 1-28}. Washington, DC: American Psychiatric Publishing, Inc, 2001]). The current research used a prospective design to evaluate whether there is a progression between these different types of self-injurious behaviors (SIB) over time. Support was found for a progression from compulsive SIB (including hair pulling, nail-biting, skin picking, scratching, and preventing wounds from healing) to impulsive SIB (including cutting, burning, carving, pin sticking, and punching) in a group of adult women (N = 106). Other factors hypothesized to be linked to this outcome were disordered eating, age, and personality facets of impulsivity (specifically, urgency and lack of perseverance). Of these variables, only urgency positively predicted impulsive SIB at the study's conclusion. These findings are discussed, limitations of the study are noted, and directions for future research are outlined.

Study on the impulsive pressure of tank oscillating by force towards multiple degrees of freedom

NASA Astrophysics Data System (ADS)

Hibi, Shigeyuki

2018-06-01

Impulsive loads should be excited under nonlinear phenomena with free surface fluctuating severely such as sloshing and slamming. Estimating impulsive loads properly are important to recent numerical simulations. But it is still difficult to rely on the results of simulations perfectly because of the nonlinearity of the phenomena. In order to develop the algorithm of numerical simulations experimental results of nonlinear phenomena are needed. In this study an apparatus which can oscillate a tank by force was introduced in order to investigate impulsive pressure on the wall of the tank. This apparatus can oscillate it simultaneously towards 3 degrees of freedom with each phase differences. The impulsive pressure under the various combinations of oscillation direction was examined and the specific phase differences to appear the largest peak values of pressure were identified. Experimental results were verified through FFT analysis and statistical methods.

Analysis of fluorine addition to the vanguard first stage

NASA Technical Reports Server (NTRS)

Tomazic, William A; Schmidt, Harold W; Tischler, Adelbert O

1957-01-01

The effect of adding fluorine to the Vanguard first-stage oxidant was anlyzed. An increase in specific impulse of 5.74 percent may be obtained with 30 percent fluorine. This increase, coupled with increased mass ratio due to greater oxidant density, gave up to 24.6-percent increase in first-stage burnout energy with 30 percent fluorine added. However, a change in tank configuration is required to accommodate the higher oxidant-fuel ratio necessary for peak specific impulse with fluorine addition.

Effect of combustion-chamber pressure and nozzle expansion ratio on theoretical performance of several rocket propellant systems

NASA Technical Reports Server (NTRS)

Morrell, Virginia E

1956-01-01

Theoretical calculations of specific impulse to determine the separate effects of increasing the combustion-chamber pressure and the nozzle expansion ratio on the performance of the propellants, hydrogen-fluorine, hydrogen-oxygen, ammonia-fluorine and AN-F-58 fuel - white fuming nitric acid (95 percent). The results indicate that an increase in specific impulse obtainable with an increase in combustion-chamber pressure is almost entirely caused by the increased expansion ratio through the nozzle.

Seeing

MedlinePlus Videos and Cool Tools

... lens. The light is then refracted a second time while passing through the lens, finally focusing on the retina. The retina is the light sensitive part of the eye. Impulses travel down the optic nerve to the occipital lobe ...

Impulse-induced localized control of chaos in starlike networks.

PubMed

Chacón, Ricardo; Palmero, Faustino; Cuevas-Maraver, Jesús

2016-06-01

Locally decreasing the impulse transmitted by periodic pulses is shown to be a reliable method of taming chaos in starlike networks of dissipative nonlinear oscillators, leading to both synchronous periodic states and equilibria (oscillation death). Specifically, the paradigmatic model of damped kicked rotators is studied in which it is assumed that when the rotators are driven synchronously, i.e., all driving pulses transmit the same impulse, the networks display chaotic dynamics. It is found that the taming effect of decreasing the impulse transmitted by the pulses acting on particular nodes strongly depends on their number and degree of connectivity. A theoretical analysis is given explaining the basic physical mechanism as well as the main features of the chaos-control scenario.

Impulsivity and self-harm in adolescence: a systematic review.

PubMed

Lockwood, Joanna; Daley, David; Townsend, Ellen; Sayal, Kapil

2017-04-01

Research supports an association between impulsivity and self-harm, yet inconsistencies in methodology across studies have complicated understanding of this relationship. This systematic review examines the association between impulsivity and self-harm in community-based adolescents aged 11-25 years and aims to integrate findings according to differing concepts and methods. Electronic searches of EMBASE, MEDLINE, PsychINFO, CINAHL, PubMed and The Cochrane Library, and manual searches of reference lists of relevant reviews identified 4496 articles published up to July 2015, of which 28 met inclusion criteria. Twenty-four of the studies reported an association between broadly specified impulsivity and self-harm. However, findings varied according to the conception and measurement of impulsivity and the precision with which self-harm behaviours were specified. Specifically, lifetime non-suicidal self-injury was most consistently associated with mood-based impulsivity-related traits. However, cognitive facets of impulsivity (relating to difficulties maintaining focus or acting without forethought) differentiated current self-harm from past self-harm. These facets also distinguished those with thoughts of self-harm (ideation) from those who acted on thoughts (enaction). The findings suggested that mood-based impulsivity is related to the initiation of self-harm, while cognitive facets of impulsivity are associated with the maintenance of self-harm. In addition, behavioural impulsivity is most relevant to self-harm under conditions of negative affect. Collectively, the findings indicate that distinct impulsivity facets confer unique risks across the life-course of self-harm. From a clinical perspective, the review suggests that interventions focusing on reducing rash reactivity to emotions or improving self-regulation and decision making may offer most benefit in supporting those who self-harm.

Evaluation of factors that affect hip moment impulse during gait: A systematic review.

PubMed

Inai, Takuma; Takabayashi, Tomoya; Edama, Mutsuaki; Kubo, Masayoshi

2018-03-01

Decreasing the daily cumulative hip moments in the frontal and sagittal planes may lower the risk of hip osteoarthritis. Therefore, it may be important to evaluate factors that affect hip moment impulse during gait. It is unclear what factors affect hip moment impulse during gait. This systematic review aimed to evaluate different factors that affect hip moment impulse during gait in healthy adults and patients with hip osteoarthritis. Four databases (Scopus, ScienceDirect, PubMed, and PEDro) were searched up to August 2017 to identify studies that examined hip moment impulse during gait. Data extracted for analysis included the sample size, age, height, body mass, type of intervention, and main findings. After screening, 10 of the 975 studies identified were included in our analysis. Several factors, including a rocker bottom shoe, FitFlop™ sandals, ankle push-off, posture, stride length, body-weight unloading, a rollator, walking poles, and a knee brace, were reviewed. The main findings were as follows: increasing ankle push-off decreased both the hip flexion and extension moment impulses; body-weight unloading decreased both the hip extension and adduction moment impulses; the FitFlop™ sandal increased the sum of the hip flexion and extension moment impulses; long strides increased the hip extension moment impulse; and the use of a knee brace increased hip flexion moment impulse. Of note, none of the eligible studies included patients with hip osteoarthritis. The hip moment impulses can be modified by person-specific factors (ankle push-off and long strides) and external factors (body-weight unloading and use of the FitFlop™ sandals and a knee brace). Effects on the progression of hip osteoarthritis remain to be evaluated. Copyright © 2018 Elsevier B.V. All rights reserved.

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

ERIC Educational Resources Information Center

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

2010-01-01

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…

Development of a PPT for the EO-1 Spacecraft

NASA Technical Reports Server (NTRS)

Benson, Scott W.; Arrington, Lynn A.; Hoskins, W. Andrew; Meckel, Nicole J.

2000-01-01

A Pulsed Plasma Thruster (PPT) has been developed for use in a technology demonstration flight experiment on the Earth Observing 1 (EO-1) New Millennium Program mission. The thruster replaces the spacecraft pitch axis momentum wheel for control and momentum management during an experiment of a minimum three-day duration. The EO-1 PPT configuration is a combination of new technology and design heritage from similar systems flown in the 1970's and 1980's. Acceptance testing of the protoflight unit has validated readiness for flight, and integration with the spacecraft, including initial combined testing, has been completed. The thruster provides a range of capability from 90 microN-sec impulse bit at 650 sec specific impulse for 12 W input power, through 860 microN-sec impulse bit at 1400 see specific impulse for 70 W input power. Development of this thruster reinitiates technology research and development and re-establishes an industry base for production of flight hardware. This paper reviews the EO-1 PPT development, including technology selection, design and fabrication, acceptance testing, and initial spacecraft integration and test.

Is comorbidity in the eating disorders related to perceptions of parenting? Criterion validity of the revised Young Parenting Inventory.

PubMed

Sheffield, Alexandra; Waller, Glenn; Emanuelli, Francesca; Murray, James

2006-01-01

Recent studies support the reliability and validity of the Young Parenting Inventory-Revised (YPI-R) and its use in investigating the role of parenting in the aetiology and maintenance of eating pathology. However, criterion validity has yet to be fully established. To investigate one aspect of criterion validity, this study examines the association between parenting and comorbid problems in the eating disorders (including general psychopathology and impulsivity). The participants were 124 women with eating disorders. They completed the YPI-R and the Brief Symptom Inventory (BSI; a measure of general psychopathology). They were also interviewed about their use of a number of impulsive behaviours. YPI-R scales were significant predictors of one of the nine BSI scales, and distinguished those patients who did or did not use specific impulsive behaviours. The criterion validity of the YPI-R is partially supported with regards to general psychopathology and impulsivity. The findings highlight the specificity of the parenting styles measured by the YPI-R, and the need for further research using this tool.

Leg stiffness and expertise in men jumping.

PubMed

Laffaye, Guillaume; Bardy, Benoît G; Durey, Alain

2005-04-01

The aim of the present study is to investigate: a) the leg spring behavior in the one-leg vertical jump, b) the contribution of impulse parameters to this behavior, and c) the effect of jumping expertise on leg stiffness. Four categories of experts (handball, basketball, volleyball players, and Fosbury athletes), as well as novice subjects performed a run-and-jump test to touch a ball with the head. Five experimental conditions were tested from 55 to 95% of the maximum jump height. Kinematic and kinetic data were collected using six cameras and a force plate. The mechanical behavior of the musculoskeleton component of the human body can be modeled as a simple mass-spring system, from which leg stiffness values can be extracted to better understand energy transfer during running or jumping. The results indicate that leg stiffness (mean value of 11.5 kN.m) decreased with jumping height. Leg shortening at takeoff also increased with jumping height, whereas contact time decreased (-18%). No difference was found between experts and novices for leg stiffness. However, a principal components analysis (PCA) indicated the contribution of two main factors to the performance. The first factor emerged out of vertical force, stiffness, and duration of impulse. The second factor included leg shortening and jumping height. Differences between experts and novices were observed in terms of the contribution of leg stiffness to jump height, and more importantly, clear differences existed between experts in jumping parameters. The analysis performed on the sport categories indeed revealed different jumping profiles, characterized by specific, sport-related impulse parameters.

Tridimensional Personality Questionnaire data on alcoholic violent offenders: specific connections to severe impulsive cluster B personality disorders and violent criminality.

PubMed

Tikkanen, Roope; Holi, Matti; Lindberg, Nina; Virkkunen, Matti

2007-07-30

The validity of traditional categorical personality disorder diagnoses is currently re-evaluated from a continuous perspective, and the evolving DSM-V classification may describe personality disorders dimensionally. The utility of dimensional personality assessment, however, is unclear in violent offenders with severe personality pathology. The temperament structure of 114 alcoholic violent offenders with antisocial personality disorder (ASPD) was compared to 84 offenders without ASPD, and 170 healthy controls. Inclusion occurred during a court-ordered mental examination preceded by homicide, assault, battery, rape or arson. Participants underwent assessment of temperament with the Tridimensional Personality Questionnaire (TPQ) and were diagnosed with DSM-III-R criteria. The typical temperament profile in violent offender having ASPD comprised high novelty seeking, high harm avoidance, and low reward dependence. A 21% minority scored low in trait harm avoidance. Results, including the polarized harm avoidance dimension, are in accordance with Cloninger's hypothesis of dimensional description of ASPD. The low harm avoidance offenders committed less impulsive violence than high harm avoidance offenders. High harm avoidance was associated with comorbid antisocial personality disorder and borderline personality disorder. Results indicate that the DSM based ASPD diagnosis in alcoholic violent offenders associates with impulsiveness and high novelty seeking but comprises two different types of ASPD associated with distinct second-order traits that possibly explain differences in type of violent criminality. Low harm avoidance offenders have many traits in common with high scorers on the Hare Psychopathy Checklist-Revised (PCL-R). Results link high harm avoidance with broad personality pathology and argue for the usefulness of self-report questionnaires in clinical praxis.

Master-slave exponential synchronization of delayed complex-valued memristor-based neural networks via impulsive control.

PubMed

Li, Xiaofan; Fang, Jian-An; Li, Huiyuan

2017-09-01

This paper investigates master-slave exponential synchronization for a class of complex-valued memristor-based neural networks with time-varying delays via discontinuous impulsive control. Firstly, the master and slave complex-valued memristor-based neural networks with time-varying delays are translated to two real-valued memristor-based neural networks. Secondly, an impulsive control law is constructed and utilized to guarantee master-slave exponential synchronization of the neural networks. Thirdly, the master-slave synchronization problems are transformed into the stability problems of the master-slave error system. By employing linear matrix inequality (LMI) technique and constructing an appropriate Lyapunov-Krasovskii functional, some sufficient synchronization criteria are derived. Finally, a numerical simulation is provided to illustrate the effectiveness of the obtained theoretical results. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electrostatic Plasma Accelerator (EPA)

NASA Technical Reports Server (NTRS)

Brophy, John R.; Aston, Graeme

1989-01-01

The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass. The goal of the present program is to demonstrate feasibility of the EPA thruster concept through experimental and theoretical investigations of the EPA acceleration mechanism and discharge chamber performance. Experimental investigations will include operating the test bed ion (TBI) engine as an EPA thruster and parametrically varying the thruster geometry and operating conditions to quantify the electrostatic plasma acceleration effect. The theoretical investigations will include the development of a discharge chamber model which describes the relationships between the engine size, plasma properties, and overall performance. For the EPA thruster to be a viable propulsion concept, overall thruster efficiencies approaching 30% with specific impulses approaching 1000 s must be achieved.

Simplified procedures for correlation of experimentally measured and predicted thrust chamber performance

NASA Technical Reports Server (NTRS)

Powell, W. B.

1973-01-01

Thrust chamber performance is evaluated in terms of an analytical model incorporating all the loss processes that occur in a real rocket motor. The important loss processes in the real thrust chamber were identified, and a methodology and recommended procedure for predicting real thrust chamber vacuum specific impulse were developed. Simplified equations for the calculation of vacuum specific impulse are developed to relate the delivered performance (both vacuum specific impulse and characteristic velocity) to the ideal performance as degraded by the losses corresponding to a specified list of loss processes. These simplified equations enable the various performance loss components, and the corresponding efficiencies, to be quantified separately (except that interaction effects are arbitrarily assigned in the process). The loss and efficiency expressions presented can be used to evaluate experimentally measured thrust chamber performance, to direct development effort into the areas most likely to yield improvements in performance, and as a basis to predict performance of related thrust chamber configurations.

Specific cognitive-neurophysiological processes predict impulsivity in the childhood attention-deficit/hyperactivity disorder combined subtype.

PubMed

Bluschke, A; Roessner, V; Beste, C

2016-04-01

Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent neuropsychiatric disorders in childhood. Besides inattention and hyperactivity, impulsivity is the third core symptom leading to diverse and serious problems. However, the neuronal mechanisms underlying impulsivity in ADHD are still not fully understood. This is all the more the case when patients with the ADHD combined subtype (ADHD-C) are considered who are characterized by both symptoms of inattention and hyperactivity/impulsivity. Combining high-density electroencephalography (EEG) recordings with source localization analyses, we examined what information processing stages are dysfunctional in ADHD-C (n = 20) compared with controls (n = 18). Patients with ADHD-C made more impulsive errors in a Go/No-go task than healthy controls. Neurophysiologically, different subprocesses from perceptual gating to attentional selection, resource allocation and response selection processes are altered in this patient group. Perceptual gating, stimulus-driven attention selection and resource allocation processes were more pronounced in ADHD-C, are related to activation differences in parieto-occipital networks and suggest attentional filtering deficits. However, only response selection processes, associated with medial prefrontal networks, predicted impulsive errors in ADHD-C. Although the clinical picture of ADHD-C is complex and a multitude of processing steps are altered, only a subset of processes seems to directly modulate impulsive behaviour. The present findings improve the understanding of mechanisms underlying impulsivity in patients with ADHD-C and might help to refine treatment algorithms focusing on impulsivity.

Gender and Impulsivity: Effects on Cue-Induced Alcohol Craving.

PubMed

Yarmush, Devorah E; Manchery, Linda; Luehring-Jones, Peter; Erblich, Joel

2016-05-01

Numerous studies have demonstrated that trait impulsivity is linked to increased risk of developing alcohol-use disorders and other substance abuse. Impulsivity has also been shown in some studies to potentiate cue-induced drug cravings. Despite considerable evidence of gender differences in impulsivity and drug craving among individuals suffering from alcohol dependence and other drug use, little research has focused on these processes in healthy young men and women who may be at risk for developing alcohol-use disorders. The objective of this study was to investigate the relationship between impulsivity and cue-induced craving, as well as possible gender differences in these effects among healthy young adults. To that end, female (n = 22) and male (n = 14) social drinkers aged 18 to 25, recruited from an urban university campus, completed the Barratt Impulsiveness Scale and reported their alcohol cravings immediately before and after laboratory exposure to alcohol cues. Findings indicated that exposure to cues elicited increased alcohol cravings, but these effects did not differ by gender. Interestingly, a significant interaction of impulsivity and gender revealed that impulsivity predicted significantly higher cue-induced cravings in women, but not men. Findings underscore the importance of better understanding the interaction of situational factors (e.g., exposure to alcohol cues) and dispositional factors (e.g., impulsivity) as potential contributors to drinking motivation. Future prospective research is needed to identify gender-specific risk factors for the development of problem drinking. Copyright © 2016 by the Research Society on Alcoholism.

Distinct circuits underlie the effects of 5-HT1B receptors on aggression and impulsivity

PubMed Central

Nautiyal, Katherine M.; Tanaka, Kenji F.; Barr, Mary M.; Tritschler, Laurent; Le Dantec, Yannick; David, Denis J.; Gardier, Alain M.; Blanco, Carlos; Hen, René; Ahmari, Susanne E.

2015-01-01

Summary Impulsive and aggressive behaviors are both modulated by serotonergic signaling, specifically through the serotonin 1B receptor (5-HT1BR). 5-HT1BR knockout mice show increased aggression and impulsivity, and 5-HT1BR polymorphisms are associated with aggression and drug addiction in humans. To dissect the mechanisms by which the 5-HT1BR affects these phenotypes, we developed a mouse model to spatially and temporally regulate 5-HT1BR expression. Our results demonstrate that forebrain 5-HT1B heteroreceptors expressed during an early postnatal period contribute to the development of the neural systems underlying adult aggression. However, distinct heteroreceptors acting during adulthood are involved in mediating impulsivity. Correlating with the impulsivity, dopamine in the nucleus accumbens is elevated in the absence of 5-HT1BRs, and normalized following adult rescue of the receptor. Overall, these data show that while adolescent expression of 5-HT1BRs influences aggressive behavior, a distinct set of 5-HT1B receptors modulate impulsive behavior during adulthood. PMID:25892302

Impulse Control and Callous-Unemotional Traits Distinguish Patterns of Delinquency and Substance Use in Justice Involved Adolescents: Examining the Moderating Role of Neighborhood Context.

PubMed

Ray, James V; Thornton, Laura C; Frick, Paul J; Steinberg, Laurence; Cauffman, Elizabeth

2016-04-01

Both callous-unemotional (CU) traits and impulse control are known risk factors associated with delinquency and substance use. However, research is limited in how contextual factors such as neighborhood conditions influence the associations between these two dispositional factors and these two externalizing behaviors. The current study utilized latent class analysis (LCA) to identify unique classes of delinquency and substance use within an ethnically diverse sample (n = 1216) of justice-involved adolescents (ages 13 to 17) from three different sites. Neighborhood disorder, CU traits, and impulse control were all independently associated with membership in classes with more extensive histories of delinquency and substance use. The effects of CU traits and impulse control in distinguishing delinquent classes was invariant across levels of neighborhood disorder, whereas neighborhood disorder moderated the association between impulse control and substance use. Specifically, the probability of being in more severe substance using classes for those low in impulse control was stronger in neighborhoods with fewer indicators of social and physical disorder.

Sounds, Behaviour, and Auditory Receptors of the Armoured Ground Cricket, Acanthoplus longipes

PubMed Central

Kowalski, Kerstin; Lakes-Harlan, Reinhard

2010-01-01

The auditory sensory system of the taxon Hetrodinae has not been studied previously. Males of the African armoured ground cricket, Acanthoplus longipes (Orthoptera: Tettigoniidae: Hetrodinae) produce a calling song that lasts for minutes and consists of verses with two pulses. About three impulses are in the first pulse and about five impulses are in the second pulse. In contrast, the disturbance stridulation consists of verses with about 14 impulses that are not separated in pulses. Furthermore, the inter-impulse intervals of both types of sounds are different, whereas verses have similar durations. This indicates that the neuronal networks for sound generation are not identical. The frequency spectrum peaks at about 15 kHz in both types of sounds, whereas the hearing threshold has the greatest sensitivity between 4 and 10 kHz. The auditory afferents project into the prothoracic ganglion. The foreleg contains about 27 sensory neurons in the crista acustica; the midleg has 18 sensory neurons, and the hindleg has 14. The auditory system is similar to those of other Tettigoniidae. PMID:20569136

Ground Reaction Forces of the Lead and Trail Limbs when Stepping Over an Obstacle

PubMed Central

Bovonsunthonchai, Sunee; Khobkhun, Fuengfa; Vachalathiti, Roongtiwa

2015-01-01

Background Precise force generation and absorption during stepping over different obstacles need to be quantified for task accomplishment. This study aimed to quantify how the lead limb (LL) and trail limb (TL) generate and absorb forces while stepping over obstacle of various heights. Material/Methods Thirteen healthy young women participated in the study. Force data were collected from 2 force plates when participants stepped over obstacles. Two limbs (right LL and left TL) and 4 conditions of stepping (no obstacle, stepping over 5 cm, 20 cm, and 30 cm obstacle heights) were tested for main effect and interaction effect by 2-way ANOVA. Paired t-test and 1-way repeated-measure ANOVA were used to compare differences of variables between limbs and among stepping conditions, respectively. The main effects on the limb were found in first peak vertical force, minimum vertical force, propulsive peak force, and propulsive impulse. Results Significant main effects of condition were found in time to minimum force, time to the second peak force, time to propulsive peak force, first peak vertical force, braking peak force, propulsive peak force, vertical impulse, braking impulse, and propulsive impulse. Interaction effects of limb and condition were found in first peak vertical force, propulsive peak force, braking impulse, and propulsive impulse. Conclusions Adaptations of force generation in the LL and TL were found to involve adaptability to altered external environment during stepping in healthy young adults. PMID:26169293

Bifactor Models Show a Superior Model Fit: Examination of the Factorial Validity of Parent-Reported and Self-Reported Symptoms of Attention-Deficit/Hyperactivity Disorders in Children and Adolescents.

PubMed

Rodenacker, Klaas; Hautmann, Christopher; Görtz-Dorten, Anja; Döpfner, Manfred

2016-01-01

Various studies have demonstrated that bifactor models yield better solutions than models with correlated factors. However, the kind of bifactor model that is most appropriate is yet to be examined. The current study is the first to test bifactor models across the full age range (11-18 years) of adolescents using self-reports, and the first to test bifactor models with German subjects and German questionnaires. The study sample included children and adolescents aged between 6 and 18 years recruited from a German clinical sample (n = 1,081) and a German community sample (n = 642). To examine the factorial validity, we compared unidimensional, correlated factors and higher-order and bifactor models and further tested a modified incomplete bifactor model for measurement invariance. Bifactor models displayed superior model fit statistics compared to correlated factor models or second-order models. However, a more parsimonious incomplete bifactor model with only 2 specific factors (inattention and impulsivity) showed a good model fit and a better factor structure than the other bifactor models. Scalar measurement invariance was given in most group comparisons. An incomplete bifactor model would suggest that the specific inattention and impulsivity factors represent entities separable from the general attention-deficit/hyperactivity disorder construct and might, therefore, give way to a new approach to subtyping of children beyond and above attention-deficit/hyperactivity disorder. © 2016 S. Karger AG, Basel.

Modeling and Testing of Non-Nuclear, Highpower Simulated Nuclear Thermal Rocket Reactor Elements

NASA Technical Reports Server (NTRS)

Kirk, Daniel R.

2005-01-01

When the President offered his new vision for space exploration in January of 2004, he said, "Our third goal is to return to the moon by 2020, as the launching point for missions beyond," and, "With the experience and knowledge gained on the moon, we will then be ready to take the next steps of space exploration: human missions to Mars and to worlds beyond." A human mission to Mars implies the need to move large payloads as rapidly as possible, in an efficient and cost-effective manner. Furthermore, with the scientific advancements possible with Project Prometheus and its Jupiter Icy Moons Orbiter (JIMO), (these use electric propulsion), there is a renewed interest in deep space exploration propulsion systems. According to many mission analyses, nuclear thermal propulsion (NTP), with its relatively high thrust and high specific impulse, is a serious candidate for such missions. Nuclear rockets utilize fission energy to heat a reactor core to very high temperatures. Hydrogen gas flowing through the core then becomes superheated and exits the engine at very high exhaust velocities. The combination of temperature and low molecular weight results in an engine with specific impulses above 900 seconds. This is almost twice the performance of the LOX/LH2 space shuttle engines, and the impact of this performance would be to reduce the trip time of a manned Mars mission from the 2.5 years, possible with chemical engines, to about 12-14 months.

Right Anterior Cingulate Cortical Thickness and Bilateral Striatal Volume Correlate with CBCL Aggressive Behavior Scores in Healthy Children

PubMed Central

Ducharme, Simon; Hudziak, James J; Botteron, Kelly N; Ganjavi, Hooman; Lepage, Claude; Collins, D Louis; Albaugh, Matthew D.; Evans, Alan C; Karama, Sherif

2011-01-01

Background The anterior cingulate cortex (ACC), orbito-frontal cortex (OFC) and basal ganglia have been implicated in pathological aggression. This study aimed at identifying neuroanatomical correlates of impulsive aggression in healthy children. Methods Data from 193 representative 6–18 year-old healthy children were obtained from the NIH MRI Study of Normal Brain Development after a blinded quality control (1). Cortical thickness and subcortical volumes were obtained with automated software. Aggression levels were measured with the Aggressive Behavior scale (AGG) of the Child Behavior Checklist (CBCL). AGG scores were regressed against cortical thickness and basal ganglia volumes using first and second-order linear models while controlling for age, gender, scanner site and total brain volume. ‘Gender by AGG’ interactions were analyzed. Results There were positive associations between bilateral striatal volumes and AGG scores (right: r=0.238, p=0.001; left: r=0.188, p=0.01). A significant association was found with right ACC and subgenual ACC cortical thickness in a second-order linear model (p<0.05, corrected). High AGG scores were associated with a relatively thin right ACC cortex. An ‘AGG by gender’ interaction trend was found in bilateral OFC and ACC associations with AGG scores. Conclusion This study shows the existence of relationships between impulsive aggression in healthy children and the structure of the striatum and right ACC. It also suggests the existence of gender specific patterns of association in OFC/ACC grey matter. These results may guide research on oppositional-defiant and conduct disorders. PMID:21531391

Right anterior cingulate cortical thickness and bilateral striatal volume correlate with child behavior checklist aggressive behavior scores in healthy children.

PubMed

Ducharme, Simon; Hudziak, James J; Botteron, Kelly N; Ganjavi, Hooman; Lepage, Claude; Collins, D Louis; Albaugh, Matthew D; Evans, Alan C; Karama, Sherif

2011-08-01

The anterior cingulate cortex (ACC), orbitofrontal cortex (OFC), and basal ganglia have been implicated in pathological aggression. This study aimed at identifying neuroanatomical correlates of impulsive aggression in healthy children. Data from 193 representative 6- to 18-year-old healthy children were obtained from the National Institutes of Health Magnetic Resonance Imaging Study of Normal Brain Development after a blinded quality control. Cortical thickness and subcortical volumes were obtained with automated software. Aggression levels were measured with the Aggressive Behavior scale (AGG) of the Child Behavior Checklist. AGG scores were regressed against cortical thickness and basal ganglia volumes using first- and second-order linear models while controlling for age, gender, scanner site, and total brain volume. Gender by AGG interactions were analyzed. There were positive associations between bilateral striatal volumes and AGG scores (right: r = .238, p = .001; left: r = .188, p = .01). A significant association was found with right ACC and subgenual ACC cortical thickness in a second-order linear model (p < .05, corrected). High AGG scores were associated with a relatively thin right ACC cortex. An AGG by gender interaction trend was found in bilateral OFC and ACC associations with AGG scores. This study shows the existence of relationships between impulsive aggression in healthy children and the structure of the striatum and right ACC. It also suggests the existence of gender-specific patterns of association in OFC/ACC gray matter. These results may guide research on oppositional-defiant and conduct disorders. Copyright © 2011 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Theoretical Rocket Performance of Liquid Methane with Several Fluorine-Oxygen Mixtures Assuming Frozen Composition

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Kastner, Michael E

1958-01-01

Theoretical rocket performance for frozen composition during expansion was calculated for liquid methane with several fluorine-oxygen mixtures for a range of pressure ratios and oxidant-fuel ratios. The parameters included are specific impulse, combustion-chamber temperature, nozzle-exit temperature molecular weight, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, isentropic exponent, viscosity, and thermal conductivity. The maximum calculated value of specific impulse for a chamber pressure of 600 pounds per square inch absolute (40.827atm) and an exit pressure of 1 atmosphere is 315.3 for 79.67 percent fluorine in the oxidant.

Unique Contributions of Impulsivity and Inhibition to Prereading Skills in Preschoolers at Head Start

ERIC Educational Resources Information Center

Fuhs, Mary Wagner; Wyant, Autumn B.; Day, Jeanne D.

2011-01-01

The goal of this study was to explore the relationship between temperament (specifically impulsivity and inhibition) and prereading skills (letter knowledge and print concepts) in preschool children from disadvantaged backgrounds. The participants in the study were 111 preschool children with a mean age of 58.09 months (SD = 5.80) attending Head…

Comparison of Transmission Line Methods for Surface Acoustic Wave Modeling

NASA Technical Reports Server (NTRS)

Wilson, William; Atkinson, Gary

2009-01-01

Surface Acoustic Wave (SAW) technology is low cost, rugged, lightweight, extremely low power and can be used to develop passive wireless sensors. For these reasons, NASA is investigating the use of SAW technology for Integrated Vehicle Health Monitoring (IVHM) of aerospace structures. To facilitate rapid prototyping of passive SAW sensors for aerospace applications, SAW models have been developed. This paper reports on the comparison of three methods of modeling SAWs. The three models are the Impulse Response Method (a first order model), and two second order matrix methods; the conventional matrix approach, and a modified matrix approach that is extended to include internal finger reflections. The second order models are based upon matrices that were originally developed for analyzing microwave circuits using transmission line theory. Results from the models are presented with measured data from devices. Keywords: Surface Acoustic Wave, SAW, transmission line models, Impulse Response Method.

Scientific Discoveries: What Is Required for Lasting Impact.

PubMed

Lømo, Terje

2016-01-01

I have been involved in two scientific discoveries of some impact. One is the discovery of long-term potentiation (LTP), the phenomenon that brief, high-frequency impulse activity at synapses in the brain can lead to long-lasting increases in their efficiency of transmission. This finding demonstrated that synapses are plastic, a property thought to be necessary for learning and memory. The other discovery is that nerve-evoked muscle impulse activity, rather than putative trophic factors, controls the properties of muscle fibers. Here I describe how these two discoveries were made, the unexpected difficulties of reproducing the first discovery, and the controversies that followed the second discovery. I discuss why the first discovery took many years to become generally recognized, whereas the second caused an immediate sensation and entered textbooks and major reviews but is now largely forgotten. In the long run, discovering a new phenomenon has greater impact than falsifying a popular hypothesis.

Voltage-impulse-induced dual-range nonvolatile magnetization modulation in metglas/PZT heterostructure

NASA Astrophysics Data System (ADS)

Tang, Xiaoli; Su, Hua; Zhang, Huaiwu; Sun, Nian X.

2016-11-01

Dual-range, nonvolatile magnetization modulation induced by voltage impulses was investigated in the metglas/lead zirconate titanate (PZT) heterostructure at room temperature. The heterostructure was obtained by bonding a square metglas ribbon on the top electrode of the PZT substrate, which contained defect dipoles resulting from acceptor doping. The PZT substrate achieved two strain hysteretic loops with the application of specific voltage impulse excitation modes. Through strain-mediated magnetoelectric coupling between the metglas ribbon and the PZT substrate, two strain hysteretic loops led to a dual-range nonvolatile magnetization modulation in the heterostructure. Reversible and stable voltage-impulse-induced nonvolatile modulation in the ferromagnetic resonance field and magnetic hysteresis characteristics were also realized. This method provides a promising approach in reducing energy consumption in magnetization modulation and other related devices.

A pilot genetic study of the continuum between compulsivity and impulsivity in females: the serotonin transporter promoter polymorphism.

PubMed

Baca-García, Enrique; Salgado, Beatríz Rodríguez; Segal, Helen Dolengevich; Lorenzo, Concepción Vaquero; Acosta, Mercedes Navio; Romero, Manuel Arrojo; Hernández, Montserrat Díaz; Saiz-Ruiz, Jeronimo; Fernandez Piqueras, Jose; de Leon, Jose

2005-06-01

According to some authors the obsessive-compulsive (OC) spectrum includes on one extreme, the Obsessive-Compulsive Disorder (OCD) and on the other extreme the most impulsive behaviors. This is a controversial idea and other authors define the OC spectrum in different ways. The serotonin transporter (5-HTT) gene is one of the main genes that control serotonergic function. A polymorphism in the promoter area of this gene classifies subjects with low expression as S individuals (s/s or s/l) and subjects with high expression as L individuals (l/l). This polymorphism was studied in female OCD patients (n = 24), non-impulsive controls (n = 112) and impulsive suicidal patients (n = 118) to support the OC spectrum hypothesis from a genetic perspective. A linear association exists among the serotonin transporter promoter functional genotypes (S versus L individuals) (chi2 linear by linear association = 8.9; df = 1; p = 0.003). The frequency of S individuals (s/l or s/s) was lowest in OCD (54%, 13/24); intermediate in non-impulsive controls (71%, 80/112) and highest in impulsive suicide attempters (82%, 96/117). More importantly, future studies need to consider that genetics may be related to behavioral dimensions (compulsivity to impulsivity) instead of to specific psychiatric disorders defined in clinical terms.

Metallized gelled monopropellants

NASA Technical Reports Server (NTRS)

Nieder, Erin G.; Harrod, Charles E.; Rodgers, Frederick C.; Rapp, Douglas C.; Palaszewski, Bryan A.

1992-01-01

Thermochemical calculations of seven metallized monopropellants were conducted to quantify theoretical specific impulse and density specific impulse performance. On the basis of theoretical performance, commercial availability of formulation constituents, and anticipated viscometric behavior, two metallized monopropellants were selected for formulation characterization: triethylene glycol dinitrate, ammonium perchlorate, aluminum and hydrogen peroxide, aluminum. Formulation goals were established, and monopropellant formulation compatibility and hazard sensitivity were experimentally determined. These experimental results indicate that the friction sensitivity, detonation susceptibility, and material handling difficulties of the elevated monopropellant formulations and their constituents pose formidable barriers to their future application as metallized monopropellants.

NASA's 2004 Hall Thruster Program

NASA Technical Reports Server (NTRS)

Jacobson, David T.; Manzella, David H.; Hofer, Richard R.; Peterson, Peter Y.

2004-01-01

An overview of NASA's Hall thruster research and development tasks conducted during fiscal year 2004 is presented. These tasks focus on: raising the technology readiness level of high power Hall thrusters, developing a moderate-power/ moderate specific impulse Hall thruster, demonstrating high-power/high specific impulse Hall thruster operation, and addressing the fundamental technical challenges of emerging Hall thruster concepts. Programmatic background information, technical accomplishments and out year plans for each program element performed under the sponsorship of the In-Space Transportation Program, Project Prometheus, and the Energetics Project are provided.

Combustion Performance of a Staged Hybrid Rocket with Boron addition

NASA Astrophysics Data System (ADS)

Lee, D.; Lee, C.

2018-04-01

In this paper, the effect of boron on overall system specific impulse was investigated. Additionally, a series of combustion tests was carried out to analyze and evaluate the effect of boron addition on O/F variation and radial temperature profiles. To maintain the hybrid rocket engine advantages, upper limit of boron contents in solid fuel was set to be 10 wt%. The results also suggested that, when adding boron to solid fuel, it helped to provide more uniform radial temperature distribution and also to increase specific impulse by 3.2%.

Small Launch Vehicle Concept Development for Affordable Multi-Stage Inline Configurations

NASA Technical Reports Server (NTRS)

Beers, Benjamin R.; Waters, Eric D.; Philips, Alan D.; Threet, Grady E., Jr.

2014-01-01

The Advanced Concepts Office at NASA's George C. Marshall Space Flight Center conducted a study of two configurations of a three-stage, inline, liquid propellant small launch vehicle concept developed on the premise of maximizing affordability by targeting a specific payload capability range based on current and future industry demand. The initial configuration, NESC-1, employed liquid oxygen as the oxidizer and rocket propellant grade kerosene as the fuel in all three stages. The second and more heavily studied configuration, NESC-4, employed liquid oxygen and rocket propellant grade kerosene on the first and second stages and liquid oxygen and liquid methane fuel on the third stage. On both vehicles, sensitivity studies were first conducted on specific impulse and stage propellant mass fraction in order to baseline gear ratios and drive the focus of concept development. Subsequent sensitivity and trade studies on the NESC-4 concept investigated potential impacts to affordability due to changes in gross liftoff mass and/or vehicle complexity. Results are discussed at a high level to understand the impact severity of certain sensitivities and how those trade studies conducted can either affect cost, performance, or both.

Sex differences in impulsivity and brain morphometry in methamphetamine users

PubMed Central

Kogachi, Shannon; Chang, Linda; Alicata, Daniel; Cunningham, Eric; Ernst, Thomas

2016-01-01

Methamphetamine (METH) is an addictive stimulant, and METH users have abnormal brain structures and function. The aims of this study were to investigate the relationships between impulsivity, brain structures, and possible sex-specific differences between METH users and non-drug using Controls. Structural MRI and the Barratt Impulsiveness Scale (BIS) questionnaire were completed in 124 subjects: 62 METH (ages 41.2 ± 1.4 years, 34 males) and 62 Controls (ages 43.3 ± 2.3 years, 36 males). Independent and interactive effects of METH use status and sex were evaluated. Relationships between METH usage characteristics, brain morphometry, and impulsivity scores were examined. METH users had higher impulsivity scores, on both the Cognitive and Behavioral Factors from the BIS (p < 0.0001–0.0001). Compared with same-sex Controls, male METH users had larger, while female METH users had smaller, right superior frontal cortex (interaction-p = 0.0005). The male METH users with larger frontal volumes and female METH users with smaller or thinner frontal cortices had greater Cognitive impulsivity (interaction-p ≤ 0.05). Only female METH users showed relatively larger nucleus accumbens (interaction-p = 0.03). Greater impulsivity and thinner frontal cortices in METH users are validated. Larger superior frontal cortex in male METH users with greater cognitive impulsivity suggest decreased dendritic pruning during adolescence might have contributed to their impulsive and drug use behaviors. In the female METH users, smaller frontal cortices and the associated greater impulsivity suggest greater neurotoxicity to these brain regions, while their relatively larger nucleus accumbens suggest an estrogen-mediated neuroprotective glial response. Men and women may be affected differently by METH use. PMID:27095357

Objectively-measured impulsivity and attention-deficit/hyperactivity disorder (ADHD): testing competing predictions from the working memory and behavioral inhibition models of ADHD.

PubMed

Raiker, Joseph S; Rapport, Mark D; Kofler, Michael J; Sarver, Dustin E

2012-07-01

Impulsivity is a hallmark of two of the three DSM-IV ADHD subtypes and is associated with myriad adverse outcomes. Limited research, however, is available concerning the mechanisms and processes that contribute to impulsive responding by children with ADHD. The current study tested predictions from two competing models of ADHD-working memory (WM) and behavioral inhibition (BI)-to examine the extent to which ADHD-related impulsive responding was attributable to model-specific mechanisms and processes. Children with ADHD (n = 21) and typically developing children (n = 20) completed laboratory tasks that provided WM (domain-general central executive [CE], phonological/visuospatial storage/rehearsal) and BI indices (stop-signal reaction time [SSRT], stop-signal delay, mean reaction time). These indices were examined as potential mediators of ADHD-related impulsive responding on two objective and diverse laboratory tasks used commonly to assess impulsive responding (CPT: continuous performance test; VMTS: visual match-to-sample). Bias-corrected, bootstrapped mediation analyses revealed that CE processes significantly attenuated between-group impulsivity differences, such that the initial large-magnitude impulsivity differences were no longer significant on either task after accounting for ADHD-related CE deficits. In contrast, SSRT partially mediated ADHD-related impulsive responding on the CPT but not VMTS. This partial attenuation was no longer significant after accounting for shared variance between CE and SSRT; CE continued to attenuate the ADHD-impulsivity relationship after accounting for SSRT. These findings add to the growing literature implicating CE deficits in core ADHD behavioral and functional impairments, and suggest that cognitive interventions targeting CE rather than storage/rehearsal or BI processes may hold greater promise for alleviating ADHD-related impairments.

Temperament and impulsivity predictors of smoking cessation outcomes.

PubMed

López-Torrecillas, Francisca; Perales, José C; Nieto-Ruiz, Ana; Verdejo-García, Antonio

2014-01-01

Temperament and impulsivity are powerful predictors of addiction treatment outcomes. However, a comprehensive assessment of these features has not been examined in relation to smoking cessation outcomes. Naturalistic prospective study. Treatment-seeking smokers (n = 140) were recruited as they engaged in an occupational health clinic providing smoking cessation treatment between 2009 and 2013. Participants were assessed at baseline with measures of temperament (Temperament and Character Inventory), trait impulsivity (Barratt Impulsivity Scale), and cognitive impulsivity (Go/No Go, Delay Discounting and Iowa Gambling Task). The outcome measure was treatment status, coded as "dropout" versus "relapse" versus "abstinence" at 3, 6, and 12 months endpoints. Participants were telephonically contacted and reminded of follow-up face to face assessments at each endpoint. The participants that failed to answer the phone calls or self-reported discontinuation of treatment and failed to attend the upcoming follow-up session were coded as dropouts. The participants that self-reported continuing treatment, and successfully attended the upcoming follow-up session were coded as either "relapse" or "abstinence", based on the results of smoking behavior self-reports cross-validated with co-oximetry hemoglobin levels. Multinomial regression models were conducted to test whether temperament and impulsivity measures predicted dropout and relapse relative to abstinence outcomes. Higher scores on temperament dimensions of novelty seeking and reward dependence predicted poorer retention across endpoints, whereas only higher scores on persistence predicted greater relapse. Higher scores on the trait dimension of non-planning impulsivity but not performance on cognitive impulsivity predicted poorer retention. Higher non-planning impulsivity and poorer performance in the Iowa Gambling Task predicted greater relapse at 3 and 6 months and 6 months respectively. Temperament measures, and specifically novelty seeking and reward dependence, predict smoking cessation treatment retention, whereas persistence, non-planning impulsivity and poor decision-making predict smoking relapse.

Sex differences in impulsivity and brain morphometry in methamphetamine users.

PubMed

Kogachi, Shannon; Chang, Linda; Alicata, Daniel; Cunningham, Eric; Ernst, Thomas

2017-01-01

Methamphetamine (METH) is an addictive stimulant, and METH users have abnormal brain structures and function. The aims of this study were to investigate the relationships between impulsivity, brain structures, and possible sex-specific differences between METH users and non-drug using Controls. Structural MRI and the Barratt Impulsiveness Scale (BIS) questionnaire were completed in 124 subjects: 62 METH (ages 41.2 ± 1.4 years, 34 males) and 62 Controls (ages 43.3 ± 2.3 years, 36 males). Independent and interactive effects of METH use status and sex were evaluated. Relationships between METH usage characteristics, brain morphometry, and impulsivity scores were examined. METH users had higher impulsivity scores, on both the Cognitive and Behavioral Factors from the BIS (p < 0.0001-0.0001). Compared with same-sex Controls, male METH users had larger, while female METH users had smaller, right superior frontal cortex (interaction-p = 0.0005). The male METH users with larger frontal volumes and female METH users with smaller or thinner frontal cortices had greater Cognitive impulsivity (interaction-p ≤ 0.05). Only female METH users showed relatively larger nucleus accumbens (interaction-p = 0.03). Greater impulsivity and thinner frontal cortices in METH users are validated. Larger superior frontal cortex in male METH users with greater cognitive impulsivity suggest decreased dendritic pruning during adolescence might have contributed to their impulsive and drug use behaviors. In the female METH users, smaller frontal cortices and the associated greater impulsivity suggest greater neurotoxicity to these brain regions, while their relatively larger nucleus accumbens suggest an estrogen-mediated neuroprotective glial response. Men and women may be affected differently by METH use.

Association of ventral striatum monoamine oxidase-A binding and functional connectivity in antisocial personality disorder with high impulsivity: A positron emission tomography and functional magnetic resonance imaging study.

PubMed

Kolla, Nathan J; Dunlop, Katharine; Downar, Jonathan; Links, Paul; Bagby, R Michael; Wilson, Alan A; Houle, Sylvain; Rasquinha, Fawn; Simpson, Alexander I; Meyer, Jeffrey H

2016-04-01

Impulsivity is a core feature of antisocial personality disorder (ASPD) associated with abnormal brain function and neurochemical alterations. The ventral striatum (VS) is a key region of the neural circuitry mediating impulsive behavior, and low monoamine oxidase-A (MAO-A) level in the VS has shown a specific relationship to the impulsivity of ASPD. Because it is currently unknown whether phenotypic MAO-A markers can influence brain function in ASPD, we investigated VS MAO-A level and the functional connectivity (FC) of two seed regions, superior and inferior VS (VSs, VSi). Nineteen impulsive ASPD males underwent [(11)C] harmine positron emission tomography scanning to measure VS MAO-A VT, an index of MAO-A density, and resting-state functional magnetic resonance imaging that assessed the FC of bilateral seed regions in the VSi and VSs. Subjects also completed self-report impulsivity measures. Results revealed functional coupling of the VSs with bilateral dorsomedial prefrontal cortex (DMPFC) that was correlated with VS MAO-A VT (r=0.47, p=0.04), and functional coupling of the VSi with right hippocampus that was anti-correlated with VS MAO-A VT (r=-0.55, p=0.01). Additionally, VSs-DMPFC FC was negatively correlated with NEO Personality Inventory-Revised impulsivity (r=-0.49, p=0.03), as was VSi-hippocampus FC with Barratt Impulsiveness Scale-11 motor impulsiveness (r=-0.50, p=0.03). These preliminary results highlight an association of VS MAO-A level with the FC of striatal regions linked to impulsive behavior in ASPD and suggest that phenotype-based brain markers of ASPD have relevance to understanding brain function. Copyright © 2016 Elsevier B.V. and ECNP. All rights reserved.

Environmental context effects on craving among consumers of caffeinated alcohol beverages: Associations with aspects of impulsivity.

PubMed

Stamates, Amy L; Lau-Barraco, Cathy

2017-12-01

The present study primarily sought to (a) determine the effects of environmental context on subjective ratings of craving for alcohol and caffeinated alcohol beverages (CAB) and (b) test inhibitory control, a state behavioral aspect of impulsivity, as a mediator of the association between context and craving in a sample of consumers of CAB. A secondary aim was to examine the associations between trait impulsivity and subjective craving for alcohol and CAB. Participants were 143 (67.1% female) college CAB drinkers. Participants were randomized into either a simulated bar context condition or neutral context condition and completed measures of alcohol use, CAB use, trait impulsivity, inhibitory control on a go/no-go task, and subjective craving for alcohol and CAB. Findings revealed that participants in the simulated bar condition, as compared with those in the neutral condition, reported more subjective craving for alcohol and for CAB; however, alcohol and CAB-specific craving were not different overall or as a function of context. The association between context and subjective craving for alcohol was not mediated by inhibitory control. Trait impulsivity was positively associated with alcohol and CAB-specific craving at baseline and post context exposure, and this finding was similar across both conditions. Therefore, the current investigation suggests that consumers of CAB may be sensitive to alcohol contexts as indicated by greater responses in alcohol and CAB-specific craving. However, inhibitory control did not explain this association. Future research may benefit from examining other potential mechanisms that explain the relationship between context and craving among CAB consumers. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

The role of negative emotionality and impulsivity in depressive/anxiety disorders and alcohol dependence.

PubMed

Boschloo, L; Vogelzangs, N; van den Brink, W; Smit, J H; Beekman, A T F; Penninx, B W J H

2013-06-01

Much is still unclear about the role of personality in the structure of common psychiatric disorders such as depressive/anxiety disorders and alcohol dependence. This study will therefore examine whether various traits of negative emotionality and impulsivity showed shared or specific associations with these disorders. Method Cross-sectional data were used from the Netherlands Study of Depression and Anxiety (NESDA), including individuals with no DSM-IV psychiatric disorder (n = 460), depressive/anxiety disorder only (i.e. depressive and/or anxiety disorder; n = 1398), alcohol dependence only (n = 32) and co-morbid depressive/anxiety disorder plus alcohol dependence (n = 358). Aspects of negative emotionality were neuroticism, hopelessness, rumination, worry and anxiety sensitivity, whereas aspects of impulsivity included disinhibition, thrill/adventure seeking, experience seeking and boredom susceptibility. Aspects of negative emotionality formed a homogeneous dimension, which was unrelated to the more heterogeneous construct of impulsivity. Although all aspects of negative emotionality were associated with alcohol dependence only, associations were much stronger for depressive/anxiety disorder only and co-morbid depressive/anxiety disorder with alcohol dependence. The results for impulsivity traits were less profound and more variable, with disinhibition and boredom susceptibility showing modest associations with both depressive/anxiety disorder and alcohol dependence, whereas low thrill/adventure seeking and high disinhibition were more strongly related with the first and the latter, respectively. Our results suggest that depressive/anxiety disorder and alcohol dependence result from shared as well as specific aetiological pathways as they showed the same associations with all aspects of negative emotionality, disinhibition and boredom susceptibility as well as specific associations with thrill/adventure seeking and disinhibition.

Do lightning positive leaders really "step"?

NASA Astrophysics Data System (ADS)

Petersen, D.

2015-12-01

It has been known for some time that positive leaders exhibit impulsive charge motion and optical emissions as they extend. However, laboratory and field observations have not produced any evidence of a process analogous to the space leader mechanism of negative leader extension. Instead, observations have suggested that the positive leader tip undergoes a continuous to intermittent series of corona streamer bursts, each burst resulting in a small forward extension of the positive leader channel. Traditionally, it has been held that lightning positive leaders extend in a continuous or quasi-continuous fashion. Lately, however, many have become concerned that this position is incongruous with observations of impulsive activity during lightning positive leader extension. It is increasingly suggested that this impulsive activity is evidence that positive leaders also undergo "stepping". There are two issues that must be addressed. The first issue concerns whether or not the physical processes underlying impulsive extension in negative and positive leaders are distinct. We argue that these processes are in fact physically distinct, and offer new high-speed video evidence to support this position. The second issue regards the proper use of the term "step" as an identifier for the impulsive forward extension of a leader. Traditional use of this term has been applied only to negative leaders, due primarily to their stronger impulsive charge motions and photographic evidence of clearly discontinuous forward progression of the luminous channel. Recently, due to the increasing understanding of the distinct "space leader" process of negative leader extension, the term "step" has increasingly come to be associated with the space leader process itself. Should this emerging association, "step" = space leader attachment, be canonized? If not, then it seems reasonable to use the term "step" to describe impulsive positive leader extension. If, however, we do wish to associate the term "step" with space leader attachment, a process unique to negative leaders, should we devise a term for those process(es) that underly impulsive positive leader extension?

Hoarders Only Discount Consumables and Are More Patient for Money

PubMed Central

Vickers, Brian D.; Preston, Stephanie D.; Gonzalez, Richard; Angott, Andrea M.

2016-01-01

Individuals with hoarding disorder (HD) excessively acquire and retain goods while also exhibiting characteristics of impulsivity and addiction. However, HD individuals do not always perform impulsively in experiments, they do not appear interested in money, and they exhibit many features of risk-aversion and future-planning. To examine impulsivity in HD, we compared validated community participants high and low in hoarding tendencies on questionnaire measures of hoarding and impulsivity as well as a standard experimental measure of impulsivity (intertemporal discounting) that was modified to compare decisions about money, pens, and snacks. Common discounting effects were replicated. Compared to the low hoarding group, the high hoarding group was more impatient for consumables (pens and snacks) but they were more patient for money. This increased patience for money in high hoarding individuals is in contrast to all other studies on discounting in disordered populations, but consistent with the phenomenology of HD. HD does not appear to be driven by a fundamental inability to wait, but rather a specific, potent desire for consumable rewards. PMID:26973479

Future orientation, impulsivity, and problem behaviors: a longitudinal moderation model.

PubMed

Chen, Pan; Vazsonyi, Alexander T

2011-11-01

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; we also tested the moderating effects by future orientation on the impulsivity-problem behaviors link over time. Additionally, we examined future orientation operationalized by items measuring education, marriage, and life domains. Findings based on growth curve analyses provided evidence of longitudinal effects by education and life future orientation on both levels of and developmental changes in problem behaviors; the effect of marriage future orientation was not significant for either test. In addition, only life future orientation moderated the effect by impulsivity on levels of problem behaviors over time. More specifically, impulsivity had a weaker effect on levels of problem behaviors over time for adolescents who reported higher levels of life future orientation.

Impulsive versus premeditated aggression: implications for mens rea decisions.

PubMed

Barratt, Ernest S; Felthous, Alan R

2003-01-01

Science can provide more information about the nature of aggressive acts, and therefore the mens rea of criminal offenses, than is commonly assumed. For example, progress has been made in classifying aggression as impulsive or premeditated within the context of the role of conscious experience in controlling behavior. This review of the status of the scientific ability to distinguish conscious from unconscious acts and more specifically impulsive from premeditated aggressive acts is organized around four themes: (i) How is aggression defined and measured in general? (ii) How does the distinction between impulsive and premeditated aggression relate to the legal concept of mens rea? (iii) How do various scientific disciplines contribute to the mind/body discourse? (iv) What risk factors are associated with impulsive and premeditated aggression respectively? The authors conclude that the most promising approach to researching the nature of behavioral intention and motivation is to apply a discipline neutral model that integrates the data from multiple disciplines, collectively designated the cognitive neurosciences. Copyright 2003 John Wiley & Sons, Ltd.

Hoarders Only Discount Consumables and Are More Patient for Money.

PubMed

Vickers, Brian D; Preston, Stephanie D; Gonzalez, Richard; Angott, Andrea M

2016-01-01

Individuals with hoarding disorder (HD) excessively acquire and retain goods while also exhibiting characteristics of impulsivity and addiction. However, HD individuals do not always perform impulsively in experiments, they do not appear interested in money, and they exhibit many features of risk-aversion and future-planning. To examine impulsivity in HD, we compared validated community participants high and low in hoarding tendencies on questionnaire measures of hoarding and impulsivity as well as a standard experimental measure of impulsivity (intertemporal discounting) that was modified to compare decisions about money, pens, and snacks. Common discounting effects were replicated. Compared to the low hoarding group, the high hoarding group was more impatient for consumables (pens and snacks) but they were more patient for money. This increased patience for money in high hoarding individuals is in contrast to all other studies on discounting in disordered populations, but consistent with the phenomenology of HD. HD does not appear to be driven by a fundamental inability to wait, but rather a specific, potent desire for consumable rewards.

The influence of sex-linked genetic mechanisms on attention and impulsivity

PubMed Central

Trent, Simon; Davies, William

2012-01-01

It is now generally agreed that there are inherent sex differences in healthy individuals across a number of neurobiological domains (including brain structure, neurochemistry, and cognition). Moreover, there is a burgeoning body of evidence highlighting sex differences within neuropsychiatric populations (in terms of the rates of incidence, clinical features/progression, neurobiology and pathology). Here, we consider the extent to which attention and impulsivity are sexually dimorphic in healthy populations and the extent to which sex might modulate the expression of disorders characterised by abnormalities in attention and/or impulsivity such as attention deficit hyperactivity disorder (ADHD), autism and addiction. We then discuss general genetic mechanisms that might underlie sex differences in attention and impulsivity before focussing on specific positional and functional candidate sex-linked genes that are likely to influence these cognitive processes. Identifying novel sex-modulated molecular targets should ultimately enable us to develop more effective therapies in disorders associated with attentional/impulsive dysfunction. PMID:21983394

Modeling Attitude Dynamics in Simulink: A Study of the Rotational and Translational Motion of a Spacecraft Given Torques and Impulses Generated by RMS Hand Controllers

NASA Technical Reports Server (NTRS)

Mauldin, Rebecca H.

2010-01-01

In order to study and control the attitude of a spacecraft, it is necessary to understand the natural motion of a body in orbit. Assuming a spacecraft to be a rigid body, dynamics describes the complete motion of the vehicle by the translational and rotational motion of the body. The Simulink Attitude Analysis Model applies the equations of rigid body motion to the study of a spacecraft?s attitude in orbit. Using a TCP/IP connection, Matlab reads the values of the Remote Manipulator System (RMS) hand controllers and passes them to Simulink as specified torque and impulse profiles. Simulink then uses the governing kinematic and dynamic equations of a rigid body in low earth orbit (LE0) to plot the attitude response of a spacecraft for five seconds given known applied torques and impulses, and constant principal moments of inertia.

Optimal spatial filtering and transfer function for SAR ocean wave spectra

NASA Technical Reports Server (NTRS)

Beal, R. C.; Tilley, D. G.

1981-01-01

The impulse response of the SAR system is not a delta function and the spectra represent the product of the underlying image spectrum with the transform of the impulse response which must be removed. A digitally computed spectrum of SEASAT imagery of the Atlantic Ocean east of Cape Hatteras was smoothed with a 5 x 5 convolution filter and the trend was sampled in a direction normal to the predominant wave direction. This yielded a transform of a noise-like process. The smoothed value of this trend is the transform of the impulse response. This trend is fit with either a second- or fourth-order polynomial which is then used to correct the entire spectrum. A 16 x 16 smoothing of the spectrum shows the presence of two distinct swells. Correction of the effects of speckle is effected by the subtraction of a bias from the spectrum.

Low-energy Lunar Trajectories with Lunar Flybys

NASA Astrophysics Data System (ADS)

Wei, B. W.; Li, Y. S.

2017-09-01

The low-energy lunar trajectories with lunar flybys are investigated in the Sun-Earth-Moon bicircular problem (BCP). Accordingly, the characteristics of the distribution of trajectories in the phase space are summarized. To begin with, by using invariant manifolds of the BCP system, the low-energy lunar trajectories with lunar flybys are sought based on the BCP model. Secondly, through the treating time as an augmented dimension in the phase space of nonautonomous system, the state space map that reveals the distribution of these lunar trajectories in the phase space is given. As a result, it is become clear that low-energy lunar trajectories exist in families, and every moment of a Sun-Earth-Moon synodic period can be the departure date. Finally, the changing rule of departure impulse, midcourse impulse at Poincaré section, transfer duration, and system energy of different families are analyzed. Consequently, the impulse optimal family and transfer duration optimal family are obtained respectively.

Impulsiveness, postprandial blood glucose, and glucoregulation affect measures of behavioral flexibility.

PubMed

Riby, Leigh M; Lai Teik Ong, Derek; Azmie, Nurulnadia Binti Mohamad; Ooi, Ee Lyn; Regina, Caroline; Yeo, Eugene Ki Wai; Massa, Jacqueline; Aquili, Luca

2017-12-01

Behavioral flexibility (BF) performance is influenced by both psychological and physiological factors. Recent evidence suggests that impulsivity and blood glucose can affect executive function, of which BF is a subdomain. Here, we hypothesized that impulsivity, fasting blood glucose (FBG), glucose changes (ie, glucoregulation) from postprandial blood glucose (PBG) following the intake of a 15-g glucose beverage could account for variability in BF performance. The Stroop Color-Word Test and the Wisconsin Card Sorting Test (WCST) were used as measures of BF, and the Barratt Impulsiveness Scale (BIS-11) to quantify participants' impulsivity. In Study 1, neither impulsivity nor FBG could predict performance on the Stroop or the WCST. In Study 2, we tested whether blood glucose levels following the intake of a sugary drink, and absolute changes in glucose levels following the intake of the glucose beverage could better predict BF. Results showed that impulsivity and the difference in blood glucose between time 1 (postprandial) and time 2, but not blood glucose levels at time 2 per se could account for variation in performance on the WCST but not on the Stroop task. More specifically, lower impulsivity scores on the BIS-11, and smaller differences in blood glucose levels from time 1 to time 2 predicted a decrease in the number of total and perseverative errors on the WCST. Our results show that measures of impulsivity and glucoregulation can be used to predict BF. Importantly our data extend the work on glucose and cognition to a clinically relevant domain of cognition. Copyright © 2017 Elsevier Inc. All rights reserved.

Probing Compulsive and Impulsive Behaviors, from Animal Models to Endophenotypes: A Narrative Review

PubMed Central

Fineberg, Naomi A; Potenza, Marc N; Chamberlain, Samuel R; Berlin, Heather A; Menzies, Lara; Bechara, Antoine; Sahakian, Barbara J; Robbins, Trevor W; Bullmore, Edward T; Hollander, Eric

2010-01-01

Failures in cortical control of fronto-striatal neural circuits may underpin impulsive and compulsive acts. In this narrative review, we explore these behaviors from the perspective of neural processes and consider how these behaviors and neural processes contribute to mental disorders such as obsessive–compulsive disorder (OCD), obsessive–compulsive personality disorder, and impulse-control disorders such as trichotillomania and pathological gambling. We present findings from a broad range of data, comprising translational and human endophenotypes research and clinical treatment trials, focussing on the parallel, functionally segregated, cortico-striatal neural projections, from orbitofrontal cortex (OFC) to medial striatum (caudate nucleus), proposed to drive compulsive activity, and from the anterior cingulate/ventromedial prefrontal cortex to the ventral striatum (nucleus accumbens shell), proposed to drive impulsive activity, and the interaction between them. We suggest that impulsivity and compulsivity each seem to be multidimensional. Impulsive or compulsive behaviors are mediated by overlapping as well as distinct neural substrates. Trichotillomania may stand apart as a disorder of motor-impulse control, whereas pathological gambling involves abnormal ventral reward circuitry that identifies it more closely with substance addiction. OCD shows motor impulsivity and compulsivity, probably mediated through disruption of OFC-caudate circuitry, as well as other frontal, cingulate, and parietal connections. Serotonin and dopamine interact across these circuits to modulate aspects of both impulsive and compulsive responding and as yet unidentified brain-based systems may also have important functions. Targeted application of neurocognitive tasks, receptor-specific neurochemical probes, and brain systems neuroimaging techniques have potential for future research in this field. PMID:19940844

Impulse control disorders and levodopa-induced dyskinesias in Parkinson's disease: an update.

PubMed

Voon, Valerie; Napier, T Celeste; Frank, Michael J; Sgambato-Faure, Veronique; Grace, Anthony A; Rodriguez-Oroz, Maria; Obeso, Jose; Bezard, Erwan; Fernagut, Pierre-Olivier

2017-03-01

Dopaminergic medications used in the treatment of patients with Parkinson's disease are associated with motor and non-motor behavioural side-effects, such as dyskinesias and impulse control disorders also known as behavioural addictions. Levodopa-induced dyskinesias occur in up to 80% of patients with Parkinson's after a few years of chronic treatment. Impulse control disorders, including gambling disorder, binge eating disorder, compulsive sexual behaviour, and compulsive shopping occur in about 17% of patients with Parkinson's disease on dopamine agonists. These behaviours reflect the interactions of the dopaminergic medications with the individual's susceptibility, and the underlying neurobiology of Parkinson's disease. Parkinsonian rodent models show enhanced reinforcing effects of chronic dopaminergic medication, and a potential role for individual susceptibility. In patients with Parkinson's disease and impulse control disorders, impairments are observed across subtypes of decisional impulsivity, possibly reflecting uncertainty and the relative balance of rewards and losses. Impairments appear to be more specific to decisional than motor impulsivity, which might reflect differences in ventral and dorsal striatal engagement. Emerging evidence suggests impulse control disorder subtypes have dissociable correlates, which indicate that individual susceptibility predisposes towards the expression of different behavioural subtypes and neurobiological substrates. Therapeutic interventions to treat patients with Parkinson's disease and impulse control disorders have shown efficacy in randomised controlled trials. Large-scale studies are warranted to identify individual risk factors and novel therapeutic targets for these diseases. Mechanisms underlying impulse control disorders and dyskinesias could provide crucial insights into other behavioural symptoms in Parkinson's disease and addictions in the general population. Copyright © 2017 Elsevier Ltd. All rights reserved.

Genetic, Psychological, and Personal Network Factors Associated With Changes in Binge Drinking Over 2 Years Among Mexican Heritage Adolescents in the USA.

PubMed

Song, Sunmi; Marcum, Christopher Steven; Wilkinson, Anna V; Shete, Sanjay; Koehly, Laura M

2018-04-24

Despite prevalent binge drinking and alcohol-dependent symptoms among Hispanics, few studies have examined how multidimensional factors influence Hispanic adolescents' binge drinking. Purpose This study examines the effects of genetic, psychological, and social network factors on binge drinking over time among Mexican heritage adolescents in the USA and whether there are correlations among genetic variants that are associated with binge drinking and psychological and network characteristics. Mexican heritage adolescents (n = 731) participated in a longitudinal study, which included genetic testing at baseline, alcohol use assessments at first and second follow-ups, and questionnaires on sensation seeking, impulsivity, and peer and family network characteristics at second follow-up. Logistic regression and Spearman correlation analyses were performed. After adjusting for demographic characteristics, underlying genetic clustering, and binge drinking at first follow-up, two genetic variants on tryptophan hydroxylase 2 (TPH2; rs17110451, rs7963717), sensation seeking and impulsivity, and having a greater fraction of peers who drink or encourage drinking alcohol were associated with greater risk whereas another genetic variant on TPH2 (rs11178999) and having a greater fraction of close family relationships were associated with reduced risk for binge drinking at second follow-up. Genetic variants in TPH1 (rs591556) were associated with sensation seeking and impulsivity, while genetic variants in TPH2 (rs17110451) were associated with the fraction of drinkers in family. Results reveal that genetic variants in the serotonin pathway, behavioral disinhibition traits, and social networks exert joint influences on binge drinking in Mexican heritage adolescents in the USA.

Different neurodevelopmental symptoms have a common genetic etiology.

PubMed

Pettersson, Erik; Anckarsäter, Henrik; Gillberg, Christopher; Lichtenstein, Paul

2013-12-01

Although neurodevelopmental disorders are demarcated as discrete entities in the Diagnostic Statistical Manual of mental disorders, empirical evidence indicates that there is a high degree of overlap among them. The first aim of this investigation was to explore if a single general factor could account for the large degree of observed overlap among neurodevelopmental problems, and explore whether this potential factor was primarily genetic or environmental in origin. The second aim was to explore whether there was systematic covariation, either genetic or environmental, over and above that contributed by the potential general factor, unique to each syndrome. Parents of all Swedish 9- and 12-year-old twin pairs born between 1992 and 2002 were targeted for interview regarding problems typical of autism spectrum disorders, ADHD and other neurodevelopmental conditions (response rate: 80 percent). Structural equation modeling was conducted on 6,595 pairs to examine the genetic and environmental structure of 53 neurodevelopmental problems. One general genetic factor accounted for a large proportion of the phenotypic covariation among the 53 symptoms. Three specific genetic subfactors identified 'impulsivity,' 'learning problems,' and 'tics and autism,' respectively. Three unique environment factors identified 'autism,' 'hyperactivity and impulsivity,' and 'inattention and learning problems,' respectively. One general genetic factor was responsible for the wide-spread phenotypic overlap among all neurodevelopmental symptoms, highlighting the importance of addressing broad patient needs rather than specific diagnoses. The unique genetic factors may help guide diagnostic nomenclature, whereas the unique environmental factors may highlight that neurodevelopmental symptoms are responsive to change at the individual level and may provide clues into different mechanisms and treatments. Future research would benefit from assessing the general factor separately from specific factors to better understand observed overlap among neurodevelopmental problems. © 2013 The Authors. Journal of Child Psychology and Psychiatry © 2013 Association for Child and Adolescent Mental Health.

Near-Term Laser Launch Capability: The Heat Exchanger Thruster

NASA Astrophysics Data System (ADS)

Kare, Jordin T.

2003-05-01

The heat exchanger (HX) thruster concept uses a lightweight (up to 1 MW/kg) flat-plate heat exchanger to couple laser energy into flowing hydrogen. Hot gas is exhausted via a conventional nozzle to generate thrust. The HX thruster has several advantages over ablative thrusters, including high efficiency, design flexibility, and operation with any type of laser. Operating the heat exchanger at a modest exhaust temperature, nominally 1000 C, allows it to be fabricated cheaply, while providing sufficient specific impulse (~600 seconds) for a single-stage vehicle to reach orbit with a useful payload; a nominal vehicle design is described. The HX thruster is also comparatively easy to develop and test, and offers an extremely promising route to near-term demonstration of laser launch.

Design Evolutuion of Hot Isotatic Press Cans for NTP Cermet Fuel Fabrication

NASA Technical Reports Server (NTRS)

Mireles, O. R.; Broadway, J.; Hickman, R.

2014-01-01

Nuclear Thermal Propulsion (NTP) is under consideration for potential use in deep space exploration missions due to desirable performance properties such as a high specific impulse (> 850 seconds). Tungsten (W)-60vol%UO2 cermet fuel elements are under development, with efforts emphasizing fabrication, performance testing and process optimization to meet NTP service life requirements [1]. Fuel elements incorporate design features that provide redundant protection from crack initiation, crack propagation potentially resulting in hot hydrogen (H2) reduction of UO2 kernels. Fuel erosion and fission product retention barriers include W coated UO2 fuel kernels, W clad internal flow channels and fuel element external W clad resulting in a fully encapsulated fuel element design as shown.

Comparative assessment of out-of-core nuclear thermionic power systems

NASA Technical Reports Server (NTRS)

Estabrook, W. C.; Koenig, D. R.; Prickett, W. Z.

1975-01-01

The hardware selections available for fabrication of a nuclear electric propulsion stage for planetary exploration were explored. The investigation was centered around a heat-pipe-cooled, fast-spectrum nuclear reactor for an out-of-core power conversion system with sufficient detail for comparison with the in-core system studies completed previously. A survey of competing power conversion systems still indicated that the modular reliability of thermionic converters makes them the desirable choice to provide the 240-kWe end-of-life power for at least 20,000 full power hours. The electrical energy will be used to operate a number of mercury ion bombardment thrusters with a specific impulse in the range of about 4,000-5,000 seconds.

MPD thruster technology

NASA Technical Reports Server (NTRS)

Myers, Roger M.; Mantenieks, Maris A.; Lapointe, Michael R.

1991-01-01

MPD (MagnetoPlasmaDynamic) thrusters demonstrated between 2000 and 7000 seconds specific impulse at efficiencies approaching 40 percent, and were operated continuously at power levels over 500 kW. These demonstrated capabilities, combined with the simplicity and robustness of the thruster, make them attractive candidates for application to both unmanned and manned orbit raising, lunar, and planetary missions. To date, however, only a limited number of thruster configurations, propellants, and operating conditions were studied. The present status of MPD research is reviewed, including developments in the measured performance levels and electrode erosion rates. Theoretical studies of the thruster dynamics are also described. Significant progress was made in establishing empirical scaling laws, performance and lifetime limitations and in the development of numerical codes to simulate the flow field and electrode processes.

Impulsive Aggression as a Comorbidity of Attention-Deficit/Hyperactivity Disorder in Children and Adolescents

PubMed Central

Amann, Birgit H.

2016-01-01

Abstract Objective: This article examines the characteristics of impulsive aggression (IA) as a comorbidity in children and adolescents with attention-deficit/hyperactivity disorder (ADHD), focusing on its incidence, impact on ADHD outcomes, need for timely intervention, and limitations of current treatment practices. Methods: Relevant literature was retrieved with electronic searches in PubMed and PsycINFO using the search strategy of “ADHD OR attention deficit hyperactivity disorder” AND “impulsive aggression OR reactive aggression OR hostile aggression OR overt aggression” AND “pediatric OR childhood OR children OR pre-adolescent OR adolescent” with separate searches using review OR clinical trial as search limits. Key articles published before the 2007 Expert Consensus Report on IA were identified using citation analysis. Results: More than 50% of preadolescents with ADHD combined subtype reportedly display clinically significant aggression, with impulsive aggression being the predominant subtype. Impulsive aggression is strongly predictive of a highly unfavorable developmental trajectory characterized by the potential for persistent ADHD, increasing psychosocial burden, accumulating comorbidities, serious lifelong functional deficits across a broad range of domains, delinquency/criminality, and adult antisocial behavior. Impulsive aggression, which triggers peer rejection and a vicious cycle of escalating dysfunction, may be a key factor in unfavorable psychosocial outcomes attributed to ADHD. Because severe aggressive behavior does not remit in many children when treated with primary ADHD therapy (i.e., stimulants and behavioral therapy), a common practice is to add medication of a different class to specifically target aggressive behavior. Conclusions: Impulsive aggression in children and adolescents with ADHD is a serious clinical and public health problem. Although adjunctive therapy with an aggression-targeted agent is widely recommended when aggressive behaviors do not remit with primary ADHD therapy, empirical evidence does not currently support the use of any specific agent. Randomized controlled trials are needed to identify aggression-targeted agents with favorable benefit–risk profiles. PMID:26744906

Efficient solid rocket propulsion for access to space

NASA Astrophysics Data System (ADS)

Maggi, Filippo; Bandera, Alessio; Galfetti, Luciano; De Luca, Luigi T.; Jackson, Thomas L.

2010-06-01

Space launch activity is expected to grow in the next few years in order to follow the current trend of space exploitation for business purpose. Granting high specific thrust and volumetric specific impulse, and counting on decades of intense development, solid rocket propulsion is a good candidate for commercial access to space, even with common propellant formulations. Yet, some drawbacks such as low theoretical specific impulse, losses as well as safety issues, suggest more efficient propulsion systems, digging into the enhancement of consolidated techniques. Focusing the attention on delivered specific impulse, a consistent fraction of losses can be ascribed to the multiphase medium inside the nozzle which, in turn, is related to agglomeration; a reduction of agglomerate size is likely. The present paper proposes a model based on heterogeneity characterization capable of describing the agglomeration trend for a standard aluminized solid propellant formulation. Material microstructure is characterized through the use of two statistical descriptors (pair correlation function and near-contact particles) looking at the mean metal pocket size inside the bulk. Given the real formulation and density of a propellant, a packing code generates the material representative which is then statistically analyzed. Agglomerate predictions are successfully contrasted to experimental data at 5 bar for four different formulations.

Binge drinking and family history of alcoholism are associated with an altered developmental trajectory of impulsive choice across adolescence.

PubMed

Jones, Scott A; Steele, Joel S; Nagel, Bonnie J

2017-07-01

To test whether binge drinking, the density of familial alcoholism (FHD) and their interaction are associated with an altered developmental trajectory of impulsive choice across adolescence, and whether more life-time drinks are associated with a greater change in impulsive choice across age. Alcohol-naive adolescents, with varying degrees of FHD, were recruited as part of an ongoing longitudinal study on adolescent development, and were grouped based on whether they remained non-drinkers (n = 83) or initiated binge drinking (n = 33) during follow-up. During all visits, adolescents completed a monetary delay discounting task to measure impulsive choice. The effects of binge-drinking status, FHD and their interaction on impulsive choice across adolescence were tested. Developmental Brain Imaging Laboratory, Oregon Health & Science University, Portland, Oregon, USA. A total of 116 healthy male and female adolescents (ages 10-17 years at baseline) completed two to four visits between July 2008 and May 2016. Discounting rates were obtained based on adolescents' preference for immediate or delayed rewards. FHD was based on parent-reported prevalence of alcohol use disorder in the participant's first- and second-degree relatives. Binge-drinking status was determined based on the number of recent binge-drinking episodes. There was a significant interaction effect of binge-drinking status and FHD on impulsive choice across age (b = 1.090, P < 0.05, β = 0.298). In adolescents who remained alcohol-naive, greater FHD was associated with a steeper decrease in discounting rates across adolescence (b = -0.633, P < 0.05, β = -0.173); however, this effect was not present in binge-drinkers. Furthermore, total life-time drinks predicted escalated impulsive choice (b = 0.002, P < 0.05, β = 0.295) in binge-drinking adolescents. A greater degree of familial alcoholism is associated with a steeper decline in impulsive choice across adolescence, but only in those who remain alcohol-naive. Meanwhile, more life-time drinks during adolescence is associated with increases in impulsive choice across age. © 2017 Society for the Study of Addiction.

Excessive Eating and Compulsive Buying Behaviours in Women: An Empirical Pilot Study Examining Reward Sensitivity, Anxiety, Impulsivity, Self-Esteem and Social Desirability

ERIC Educational Resources Information Center

Davenport, Kate; Houston, James E.; Griffiths, Mark D.

2012-01-01

"Mall disorders" such as excessive eating and compulsive buying appear to be increasing, particularly among women. A battery of questionnaires was used in an attempt to determine this association between specific personality traits (i.e., reward sensitivity, impulsivity, cognitive and somatic anxiety, self-esteem, and social desirability) and…

Effect of Victimization on Impulse Control and Binge Drinking among Serious Juvenile Offenders from Adolescence to Young Adulthood.

PubMed

Davis, Jordan P; Dumas, Tara M; Berey, Benjamin L; Merrin, Gabriel J; Cimpian, Joseph R; Roberts, Brent W

2017-07-01

A vast literature has found longitudinal effects of early life stress on substance use and self-regulatory processes. These associations may vary by period-specific development among youth involved in the juvenile justice system. The current study used an accelerated longitudinal design and auto-regressive latent trajectory with structure residuals (ALT-SR) model to examine the within-person cross-lagged associations between binge drinking, impulse control, and victimization from 15 to 25 years of age. A large sample (N = 1100) of justice-involved youth were followed longitudinally for 7 years (M age baseline  = 15.8, M age conclusion  = 22.8). In general, the sample was ethnically diverse (41% Black, 34% Hispanic, 21% White, 4.3% Other) and primarily male (87.2%). Participants reported on their frequency of binge drinking, impulse control, and frequency of victimization at each time point. The results indicated that, during adolescence, victimization and binge drinking attenuated impulse control, which resulted in more binge drinking and victimization during young adulthood. The current study highlights the importance of assessing developmental processes and period-specific transitions among at risk youth, especially for youth experiencing early life stress.

Characterizing Impulsivity in Mania

PubMed Central

Strakowski, Stephen M.; Fleck, David E.; DelBello, Melissa P.; Adler, Caleb M.; Shear, Paula K.; McElroy, Susan L.; Keck, Paul E.; Moss, Quinton; Cerullo, Michael A.; Kotwal, Renu; Arndt, Stephan

2008-01-01

Objective To determine whether specific aspects of impulsivity (response disinhibition, inability to delay gratification, inattention) differ between healthy and bipolar manic subjects, and whether these aspects of impulsivity were associated with each other and severity of affective symptoms. Methods Performance of 70 bipolar I manic or mixed patients was compared to that of 34 healthy subjects on three tasks specifically designed to study response inhibition, ability to delay gratification, and attention; namely a stop signal task, a delayed reward task, and a continuous performance task respectively. Correlations among tasks and with symptom ratings were also performed. Results Bipolar subjects demonstrated significant deficits on all three tasks as compared to healthy subjects. Performance on the three tasks was largely independent. Task performance was not significantly associated with the severity of affective symptom ratings. However, measures of response inhibition and attention were sensitive to medication effects. Differences in the delayed reward task were independent of medication effects or symptom ratings. During the delayed reward task, although bipolar patients made their choices more slowly than healthy subjects, they were significantly more likely to choose a smaller, but more quickly obtained reward. Moreover performance on this task was not associated with performance on the other impulsivity measures. Manic patients showed more impulsive responding than mixed patients. Conclusions Bipolar I manic patients demonstrate deficits on tests of various aspects of impulsivity as compared to healthy subjects. Some of these differences between groups may be mediated by medication effects. Findings suggested that inability to delay gratification (i.e., delayed reward task) was not simply a result of the speed of decision making or inattention, but rather that it reflected differences between bipolar and healthy subjects in the valuation of reward relative to delay. PMID:19133965

Impulsive choice behavior in four strains of rats: Evaluation of possible models of Attention Deficit/Hyperactivity Disorder

PubMed Central

Garcia, Ana; Kirkpatrick, Kimberly

2012-01-01

Several studies have examined impulsive choice behavior in spontaneously hypertensive rats (SHRs) as a possible pre-clinical model for Attention-Deficit/Hyperactivity Disorder (ADHD). However, this strain was not specifically selected for the traits of ADHD and as a result their appropriateness as a model has been questioned. The present study investigated whether SHRs would exhibit impulsive behavior in comparison to their control strain, Wistar Kyoto (WKY) rats. In addition, we evaluated a strain that has previously shown high levels of impulsive choice, the Lewis (LEW) rats and compared them with their source strain, Wistar (WIS) rats. In the first phase, rats could choose between a Smaller-sooner (SS) reward of 1 pellet after 10 s and a Larger-later (LL) reward of 2 pellets after 30 s. Subsequently, the rats were exposed to increases in LL reward magnitude and SS delay. These manipulations were designed to assess sensitivity to magnitude and delay within the choice task to parse out possible differences in using the strains as models of specific deficits associated with ADHD. The SHR and WKY strains did not differ in their choice behavior under either delay or magnitude manipulations. In comparison to WIS, LEW showed deficits in choice behavior in the delay manipulation, and to a lesser extent in the magnitude manipulation. An examination of individual differences indicated that the SHR strain may not be sufficiently homogeneous in their impulsive choice behavior to be considered as a viable model for impulse control disorders such as ADHD. The LEW strain may be worthy of further consideration for their suitability as an animal model. PMID:23085479

Impulsivity and test meal intake among women with bulimia nervosa

PubMed Central

Sysko, Robyn; Ojserkis, Rachel; Schebendach, Janet; Evans, Suzette M.; Hildebrandt, Tom; Walsh, B. Timothy

2017-01-01

Many patients with bulimia nervosa (BN) also meet criteria for a lifetime alcohol use disorder (AUD). In order to understand possible mechanisms contributing to the co-occurrence and perpetuation of these disorders, this study investigated the importance of impulsivity and test meal intake among patients with BN by comparing women with BN only (n = 18), BN and current/past AUDs (n = 13), and healthy controls (n = 12). All participants completed assessments of eating disorder symptoms, frequency of alcohol use, binge eating, and purging via questionnaires and semi-structured interviews over two sessions. Measures of impulsivity consisted of computerized and self-report measures, and laboratory test meals. Significant differences between individuals with BN with/without comorbid AUDs were not found for test meal intake, impulsivity measures, or self-reported psychological symptoms. As hypothesized, compared to healthy controls, individuals with BN had significantly higher scores on two subscales and the total score of the Barratt Impulsiveness Scale, a trait measure of impulsivity, and consumed significantly more calories in the binge instruction meal. Total Barratt Impulsiveness Scale scores were also significantly related to kcal consumed during the laboratory test meal when individuals were instructed to binge eat (BN groups). Data from this study add to the existing literature implicating impulsivity in the psychopathology of disorders of binge eating, including BN, and also support the use of laboratory meals as a symptom-specific measure of this trait in eating disorder populations. PMID:28077307

Impulsivity and test meal intake among women with bulimia nervosa.

PubMed

Sysko, Robyn; Ojserkis, Rachel; Schebendach, Janet; Evans, Suzette M; Hildebrandt, Tom; Walsh, B Timothy

2017-05-01

Many patients with bulimia nervosa (BN) also meet criteria for a lifetime alcohol use disorder (AUD). In order to understand possible mechanisms contributing to the co-occurrence and perpetuation of these disorders, this study investigated the importance of impulsivity and test meal intake among patients with BN by comparing women with BN only (n = 18), BN and current/past AUDs (n = 13), and healthy controls (n = 12). All participants completed assessments of eating disorder symptoms, frequency of alcohol use, binge eating, and purging via questionnaires and semi-structured interviews over two sessions. Measures of impulsivity consisted of computerized and self-report measures, and laboratory test meals. Significant differences between individuals with BN with/without comorbid AUDs were not found for test meal intake, impulsivity measures, or self-reported psychological symptoms. As hypothesized, compared to healthy controls, individuals with BN had significantly higher scores on two subscales and the total score of the Barratt Impulsiveness Scale, a trait measure of impulsivity, and consumed significantly more calories in the binge instruction meal. Total Barratt Impulsiveness Scale scores were also significantly related to kcal consumed during the laboratory test meal when individuals were instructed to binge eat (BN groups). Data from this study add to the existing literature implicating impulsivity in the psychopathology of disorders of binge eating, including BN, and also support the use of laboratory meals as a symptom-specific measure of this trait in eating disorder populations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Impulsivity moderates promotive environmental influences on adolescent delinquency: A comparison across family, school, and neighborhood contexts

PubMed Central

Chen, Pan; Jacobson, Kristen C.

2013-01-01

The present study examined moderating effects of impulsivity on the relationships between promotive factors from family (family warmth, parental knowledge), school (school connectedness), and neighborhood (neighborhood cohesion) contexts with delinquency using data collected from N = 2,978 sixth to eighth graders from 16 schools surrounding a major city in the Midwestern United States. More than half of the respondents were non-Caucasian (Mage = 12.48; 41.0% male). Multilevel modeling analyses were conducted to take into account the clustering of the participants within schools. Impulsivity was positively associated with adolescent delinquency. Additionally, family warmth, parental knowledge, and school connectedness, but not neighborhood cohesion, were independently and inversely related to adolescent delinquency. Finally, impulsivity moderated relationships between family warmth and parental knowledge with delinquency but not relationships between school attachment and neighborhood cohesion with delinquency. Specifically, the negative relationship between family warmth and delinquency was significant for adolescents with high levels of, but not for those with below-average levels of, impulsivity. In addition, parental knowledge had a stronger association with decreased levels of delinquency for adolescents reporting higher levels of impulsivity. The moderating effects of impulsivity did not differ for males and females or for minority and non-minority participants. Findings indicate that impulsivity may have greater impact on adolescents’ susceptibility to positive family influences than on their susceptibility to promotive factors from school or neighborhood contexts. Implications for future research and practice are discussed. PMID:23673971

Impulsivity moderates promotive environmental influences on adolescent delinquency: a comparison across family, school, and neighborhood contexts.

PubMed

Chen, Pan; Jacobson, Kristen C

2013-10-01

The present study examined moderating effects of impulsivity on the relationships between promotive factors from family (family warmth, parental knowledge), school (school connectedness), and neighborhood (neighborhood cohesion) contexts with delinquency using data collected from N = 2,978 sixth to eighth graders from 16 schools surrounding a major city in the Midwestern United States. More than half of the respondents were non-Caucasian (M age  = 12.48; 41.0 % male). Multilevel modeling analyses were conducted to take into account the clustering of the participants within schools. Impulsivity was positively associated with adolescent delinquency. Additionally, family warmth, parental knowledge, and school connectedness, but not neighborhood cohesion, were independently and inversely related to adolescent delinquency. Finally, impulsivity moderated relationships between family warmth and parental knowledge with delinquency but not relationships between school attachment and neighborhood cohesion with delinquency. Specifically, the negative relationship between family warmth and delinquency was significant for adolescents with high levels of, but not for those with below-average levels of, impulsivity. In addition, parental knowledge had a stronger association with decreased levels of delinquency for adolescents reporting higher levels of impulsivity. The moderating effects of impulsivity did not differ for males and females or for minority and non-minority participants. Findings indicate that impulsivity may have greater impact on adolescents' susceptibility to positive family influences than on their susceptibility to promotive factors from school or neighborhood contexts. Implications for future research and practice are discussed.

Women with elevated food addiction symptoms show accelerated reactions, but no impaired inhibitory control, in response to pictures of high-calorie food-cues.

PubMed

Meule, Adrian; Lutz, Annika; Vögele, Claus; Kübler, Andrea

2012-12-01

Addictive behaviors are accompanied by a lack of inhibitory control, specifically when individuals are confronted with substance-related cues. Thus, we expected women with symptoms of food addiction to be impaired in inhibitory control, when confronted with palatable, high-calorie food-cues. Female college students (N=50) were divided in low and high food addiction groups based on the symptom count of the Yale Food Addiction Scale. Participants performed a Go/No-go-task with high-calorie food-cues or neutral pictures presented behind the targets. Self-reported impulsivity was also assessed. The high food addiction group had faster reaction times in response to food-cues as compared to neutral cues and reported higher attentional impulsivity than the low food addiction group. Commission and omission errors did not differ between groups or picture types. Hence, women with food addiction symptoms reported higher attentional impulsivity and reacted faster in response to food-cues, although neither increased self-reported motor impulsivity nor impaired behavioral inhibition was found. Food addiction symptoms seem to be related to attentional aspects of impulsivity but not other facets of impulsivity. Copyright © 2012 Elsevier Ltd. All rights reserved.

An Exploration Of Fuel Optimal Two-impulse Transfers To Cyclers in the Earth-Moon System

NASA Astrophysics Data System (ADS)

Hosseinisianaki, Saghar

2011-12-01

This research explores the optimum two-impulse transfers between a low Earth orbit and cycler orbits in the Earth-Moon circular restricted three-body framework, emphasizing the optimization strategy. Cyclers are those types of periodic orbits that meet both the Earth and the Moon periodically. A spacecraft on such trajectories are under the influence of both the Earth and the Moon gravitational fields. Cyclers have gained recent interest as baseline orbits for several Earth-Moon mission concepts, notably in relation to human exploration. In this thesis it is shown that a direct optimization starting from the classic lambert initial guess may not be adequate for these problems and propose a three-step optimization solver to improve the domain of convergence toward an optimal solution. The first step consists of finding feasible trajectories with a given transfer time. I employ Lambert's problem to provide initial guess to optimize the error in arrival position. This includes the analysis of the liability of Lambert's solution as an initial guess. Once a feasible trajectory is found, the velocity impulse is only a function of transfer time, departure, and arrival points' phases. The second step consists of the optimization of impulse over transfer time which results in the minimum impulse transfer for fixed end points. Finally, the third step is mapping the optimal solutions as the end points are varied.

An Exploration Of Fuel Optimal Two-impulse Transfers To Cyclers in the Earth-Moon System

NASA Astrophysics Data System (ADS)

Hosseinisianaki, Saghar

This research explores the optimum two-impulse transfers between a low Earth orbit and cycler orbits in the Earth-Moon circular restricted three-body framework, emphasizing the optimization strategy. Cyclers are those types of periodic orbits that meet both the Earth and the Moon periodically. A spacecraft on such trajectories are under the influence of both the Earth and the Moon gravitational fields. Cyclers have gained recent interest as baseline orbits for several Earth-Moon mission concepts, notably in relation to human exploration. In this thesis it is shown that a direct optimization starting from the classic lambert initial guess may not be adequate for these problems and propose a three-step optimization solver to improve the domain of convergence toward an optimal solution. The first step consists of finding feasible trajectories with a given transfer time. I employ Lambert's problem to provide initial guess to optimize the error in arrival position. This includes the analysis of the liability of Lambert's solution as an initial guess. Once a feasible trajectory is found, the velocity impulse is only a function of transfer time, departure, and arrival points' phases. The second step consists of the optimization of impulse over transfer time which results in the minimum impulse transfer for fixed end points. Finally, the third step is mapping the optimal solutions as the end points are varied.

The effects of physical activity on impulsive choice: Influence of sensitivity to reinforcement amount and delay.

PubMed

Strickland, Justin C; Feinstein, Max A; Lacy, Ryan T; Smith, Mark A

2016-05-01

Impulsive choice is a diagnostic feature and/or complicating factor for several psychological disorders and may be examined in the laboratory using delay-discounting procedures. Recent investigators have proposed using quantitative measures of analysis to examine the behavioral processes contributing to impulsive choice. The purpose of this study was to examine the effects of physical activity (i.e., wheel running) on impulsive choice in a single-response, discrete-trial procedure using two quantitative methods of analysis. To this end, rats were assigned to physical activity or sedentary groups and trained to respond in a delay-discounting procedure. In this procedure, one lever always produced one food pellet immediately, whereas a second lever produced three food pellets after a 0, 10, 20, 40, or 80-s delay. Estimates of sensitivity to reinforcement amount and sensitivity to reinforcement delay were determined using (1) a simple linear analysis and (2) an analysis of logarithmically transformed response ratios. Both analyses revealed that physical activity decreased sensitivity to reinforcement amount and sensitivity to reinforcement delay. These findings indicate that (1) physical activity has significant but functionally opposing effects on the behavioral processes that contribute to impulsive choice and (2) both quantitative methods of analysis are appropriate for use in single-response, discrete-trial procedures. Copyright © 2016 Elsevier B.V. All rights reserved.

Multiply charged ion generation according to magnetic field configurations in Hall thruster plasmas

NASA Astrophysics Data System (ADS)

Kim, Holak; Lee, Seunghun; Kim, Junbum; Lim, Youbong; Choe, Wonho; KIMS Collaboration

2016-09-01

Plasma propulsion is the most promising techniques to operate satellites for low earth orbit as well as deep space exploration. A typical plasma propulsion system is Hall thruster (HT) that uses crossed electromagnetic fields to ionize a propellant gas and to accelerate the ionized gas. In HT the tailoring of magnetic fields is significant due to that the electron confinement in the electromagnetic fields affects thruster performances such as thrust force, specific impulse, power efficiency, and life time. We designed an anode layer HT (TAL) with the magnetic field tailoring. The TAL is possible to keep discharge in 1 2 kilovolts, which voltage is useful to obtain high specific impulse The magnetic field tailoring is adapted to minimize undesirable heat dissipations and secondary electron emissions at a wall surrounding plasma In presentation, we will report TAL performances including thrust force, specific impulse, and anode efficiency measured by a pendulum thrust stand. This mechanical measurement will be compared to the plasma diagnostics conducted by angular Faraday probe, retarding potential analyzer, and ExB probe Grant No. 2014M1A3A3A02034510.

An overview of the Nuclear Electric Xenon Ion System (NEXIS) program

NASA Technical Reports Server (NTRS)

Polk, Jay E.; Goebel, Don; Brophy, John R.; Beatty, John; Monheiser, J.; Giles, D.; Hobson, D.; Wilson, F.; Christensen, J.; De Pano, M.;

Auto-programmable impulse neural circuits

NASA Technical Reports Server (NTRS)

Watula, D.; Meador, J.

1990-01-01

Impulse neural networks use pulse trains to communicate neuron activation levels. Impulse neural circuits emulate natural neurons at a more detailed level than that typically employed by contemporary neural network implementation methods. An impulse neural circuit which realizes short term memory dynamics is presented. The operation of that circuit is then characterized in terms of pulse frequency modulated signals. Both fixed and programmable synapse circuits for realizing long term memory are also described. The implementation of a simple and useful unsupervised learning law is then presented. The implementation of a differential Hebbian learning rule for a specific mean-frequency signal interpretation is shown to have a straightforward implementation using digital combinational logic with a variation of a previously developed programmable synapse circuit. This circuit is expected to be exploited for simple and straightforward implementation of future auto-adaptive neural circuits.

A General Method for Automatic Computation of Equilibrium Compositions and Theoretical Rocket Performance of Propellants

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Zeleznik, Frank J.; Huff, Vearl N.

1959-01-01

A general computer program for chemical equilibrium and rocket performance calculations was written for the IBM 650 computer with 2000 words of drum storage, 60 words of high-speed core storage, indexing registers, and floating point attachments. The program is capable of carrying out combustion and isentropic expansion calculations on a chemical system that may include as many as 10 different chemical elements, 30 reaction products, and 25 pressure ratios. In addition to the equilibrium composition, temperature, and pressure, the program calculates specific impulse, specific impulse in vacuum, characteristic velocity, thrust coefficient, area ratio, molecular weight, Mach number, specific heat, isentropic exponent, enthalpy, entropy, and several thermodynamic first derivatives.

Design and Development of a 3 to 10 kW Ammonia Arcjet

NASA Technical Reports Server (NTRS)

Goodfellow, K. D.; Polk, J. E.

1993-01-01

An ammonia arcjet capable of throttling between 3 and 10 kW and producing a specific impulse of 600 s is required for the SSTAR flight experiment. Testing was performed to evaluate the performance of two nozzle configurations on ammonia arcjet performance over this power range. One of the objectives of these tests was to quantify the effect small nozzle changes have on performance. The smaller constrictor engine (2.54 mm diameter) produced a specific impulse of about 650 s over the range of 3 to 10 kW at a specific power of 60 kJ/g exceeding the 500-600 s requirement for the SSTAR flight experiment.

A functional neuroimaging study assessing gender differences in the neural mechanisms underlying the ability to resist impulsive desires.

PubMed

Diekhof, Esther K; Keil, Maria; Obst, Katrin U; Henseler, Ilona; Dechent, Peter; Falkai, Peter; Gruber, Oliver

2012-09-14

There is ample evidence of gender differences in neural processes and behavior. Differences in reward-related behaviors have been linked to either temporary or permanent organizational influences of gonadal hormones on the mesolimbic dopamine system and reward-related activation. Still, little is known about the association between biological gender and the neural underpinnings of the ability to resist reward-related impulses. Here we assessed with functional magnetic resonance imaging which neural processes enable men and women to successfully control their desire for immediate reward when this is required by a higher-order goal (i.e., during a 'desire-reason dilemma'; Diekhof and Gruber, 2010). Thirty-two participants (16 females) were closely matched for age, personality characteristics (e.g., novelty seeking) and behavioral performance in the 'desire-reason task'. On the neural level, men and women showed similarities in the general response of the nucleus accumbens and of the ventral tegmental area to predictors of immediate reward, but they differed in additional brain mechanisms that enabled self-controlled decisions against the preference for immediate reward. Firstly, men exhibited a stronger reduction of activation in the ventral pallidum, putamen, temporal pole and pregenual anterior cingulate cortex during the 'desire-reason dilemma'. Secondly, connectivity analyses revealed a significant change in the direction of the connectivity between anteroventral prefrontal cortex and nucleus accumbens during decisions counteracting the reward-related impulse when comparing men and women. Together, these findings support the view of a sexual dimorphism that manifested in the recruitment of gender-specific neural resources during the successful deployment of self-control. Copyright © 2012 Elsevier B.V. All rights reserved.

Tridimensional Personality Questionnaire data on alcoholic violent offenders: specific connections to severe impulsive cluster B personality disorders and violent criminality

PubMed Central

Tikkanen, Roope; Holi, Matti; Lindberg, Nina; Virkkunen, Matti

2007-01-01

Background The validity of traditional categorical personality disorder diagnoses is currently re-evaluated from a continuous perspective, and the evolving DSM-V classification may describe personality disorders dimensionally. The utility of dimensional personality assessment, however, is unclear in violent offenders with severe personality pathology. Methods The temperament structure of 114 alcoholic violent offenders with antisocial personality disorder (ASPD) was compared to 84 offenders without ASPD, and 170 healthy controls. Inclusion occurred during a court-ordered mental examination preceded by homicide, assault, battery, rape or arson. Participants underwent assessment of temperament with the Tridimensional Personality Questionnaire (TPQ) and were diagnosed with DSM-III-R criteria. Results The typical temperament profile in violent offender having ASPD comprised high novelty seeking, high harm avoidance, and low reward dependence. A 21% minority scored low in trait harm avoidance. Results, including the polarized harm avoidance dimension, are in accordance with Cloninger's hypothesis of dimensional description of ASPD. The low harm avoidance offenders committed less impulsive violence than high harm avoidance offenders. High harm avoidance was associated with comorbid antisocial personality disorder and borderline personality disorder. Conclusion Results indicate that the DSM based ASPD diagnosis in alcoholic violent offenders associates with impulsiveness and high novelty seeking but comprises two different types of ASPD associated with distinct second-order traits that possibly explain differences in type of violent criminality. Low harm avoidance offenders have many traits in common with high scorers on the Hare Psychopathy Checklist-Revised (PCL-R). Results link high harm avoidance with broad personality pathology and argue for the usefulness of self-report questionnaires in clinical praxis. PMID:17662159

FURTHER STUDY OF SOMA, DENDRITE, AND AXON EXCITATION IN SINGLE NEURONS

PubMed Central

Eyzaguirre, Carlos; Kuffler, Stephen W.

1955-01-01

The present investigation continues a previous study in which the soma-dendrite system of sensory neurons was excited by stretch deformation of the peripheral dendrite portions. Recording was done with intracellular leads which were inserted into the cell soma while the neuron was activated orthodromically or antidromically. The analysis was also extended to axon conduction. Crayfish, Procambarus alleni (Faxon) and Orconectes virilis (Hagen), were used. 1. The size and time course of action potentials recorded from the soma-dendrite complex vary greatly with the level of the cell's membrane potential. The latter can be changed over a wide range by stretch deformation which sets up a "generator potential" in the distal portions of the dendrites. If a cell is at its resting unstretched equilibrium potential, antidromic stimulation through the axon causes an impulse which normally overshoots the resting potential and decays into an afternegativity of 15 to 20 msec. duration. The postspike negativity is not followed by an appreciable hyperpolarization (positive) phase. If the membrane potential is reduced to a new steady level a postspike positivity appears and increases linearly over a depolarization range of 12 to 20 mv. in various cells. At those levels the firing threshold of the cell for orthodromic discharges is generally reached. 2. The safety factor for conduction between axon and cell soma is reduced under three unrelated conditions, (a) During the recovery period (2 to 3 msec.) immediately following an impulse which has conducted fully over the cell soma, a second impulse may be delayed, may invade the soma partially, or may be blocked completely. (b) If progressive depolarization is produced by stretch, it leads to a reduction of impulse height and eventually to complete block of antidromic soma invasion, resembling cathodal block, (c) In some cells, when the normal membrane potential is within several millivolts of the relaxed resting state, an antidromic impulse may be blocked and may set up within the soma a local potential only. The local potential can sum with a second one or it may sum with potential changes set up in the dendrites, leading to complete invasion of the soma. Such antidromic invasion block can always be relieved by appropriate stretch which shifts the membrane potential out of the "blocking range" nearer to the soma firing level. During the afterpositivity of an impulse in a stretched cell the membrane potential may fall below or near the blocking range. During that period another impulse may be delayed or blocked. 3. Information regarding activity and conduction in dendrites has been obtained indirectly, mainly by analyzing the generator action under various conditions of stretch. The following conclusions have been reached: The large dendrite branches have similar properties to the cell body from which they arise and carry the same kind of impulses. In the finer distal filaments of even lightly depolarized dendrites, however, no axon type all-or-none conduction occurs since the generator potential persists to a varying degree during antidromic invasion of the cell. With the membrane potential at its resting level the dendrite terminals contribute to the prolonged impulse afternegativity of the soma. 4. Action potentials in impaled axons and in cell bodies have been compared. It is thought that normally the over-all duration of axon impulses is shorter. Local activity during reduction of the safety margin for conduction was studied. 5. An analysis was made of high frequency grouped discharges which occasionally arise in cells. They differ in many essential aspects from the regular discharges set up by the generator action. It is proposed that grouped discharges occur only when invasion of dendrites is not synchronous, due to a delay in excitation spread between soma and dendrites. Each impulse in a group is assumed to be caused by an impulse in at least one of the large dendrite branches. Depolarization of dendrites abolishes the grouped activity by facilitating invasion of the large dendrite branches. PMID:13252238

Newton's second law and the multiplication of distributions

NASA Astrophysics Data System (ADS)

Sarrico, C. O. R.; Paiva, A.

2018-01-01

Newton's second law is applied to study the motion of a particle subjected to a time dependent impulsive force containing a Dirac delta distribution. Within this setting, we prove that this problem can be rigorously solved neither by limit processes nor by using the theory of distributions (limited to the classical Schwartz products). However, using a distributional multiplication, not defined by a limit process, a rigorous solution emerges.

Selected algorithms for measurement data processing in impulse-radar-based system for monitoring of human movements

NASA Astrophysics Data System (ADS)

Miękina, Andrzej; Wagner, Jakub; Mazurek, Paweł; Morawski, Roman Z.

2016-11-01

The importance of research on new technologies that could be employed in care services for elderly and disabled persons is highlighted. Advantages of impulse-radar sensors, when applied for non-intrusive monitoring of such persons in their home environment, are indicated. Selected algorithms for the measurement data preprocessing - viz. the algorithms for clutter suppression and echo parameter estimation, as well as for estimation of the twodimensional position of a monitored person - are proposed. The capability of an impulse-radar- based system to provide some application-specific parameters, viz. the parameters characterising the patient's health condition, is also demonstrated.

Personality differences in the susceptibility to stress-eating: The influence of emotional control and impulsivity.

PubMed

Van Blyderveen, Sherry; Lafrance, Adele; Emond, Michael; Kosmerly, Stacey; O'Connor, Megan; Chang, Felicia

2016-12-01

Stress has been associated with deviations from typical eating patterns, with respect to both food choice and overall caloric intake. Both increases and decreases in dietary intake have been previously noted in response to stress. The purpose of the present study was to determine whether the affect regulation strategies of emotional control and impulsivity predict susceptibility to eating in response to stress. Specifically, it was anticipated that emotional suppression would predict decreases in caloric intake, whereas impulsivity would predict increases in caloric intake, in response to a stressor. Participants were randomly assigned to view either a video designed to elicit stress or a control video. Food was provided during the video and the amount and type of food consumed was measured. Participants' nutritional intake was greater in the stress condition than in the control condition. One aspect of affect regulation, impulsivity, moderated this relationship, with a tendency for greater impulsivity to be associated with greater caloric intake in the stress condition. The degree of negative affect that participants experienced in the stress condition predicted food choice and overall caloric intake. Both emotional control and impulsivity moderated the relationship between negative affect and both food choice and caloric intake in the stress condition. The present study highlights the importance of considering the personality attributes of both impulsivity and emotional suppression in understanding stress eating. Copyright © 2016. Published by Elsevier Ltd.

Computation of Nonlinear Hydrodynamic Loads on Floating Wind Turbines Using Fluid-Impulse Theory: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kok Yan Chan, G.; Sclavounos, P. D.; Jonkman, J.

2015-04-02

A hydrodynamics computer module was developed for the evaluation of the linear and nonlinear loads on floating wind turbines using a new fluid-impulse formulation for coupling with the FAST program. The recently developed formulation allows the computation of linear and nonlinear loads on floating bodies in the time domain and avoids the computationally intensive evaluation of temporal and nonlinear free-surface problems and efficient methods are derived for its computation. The body instantaneous wetted surface is approximated by a panel mesh and the discretization of the free surface is circumvented by using the Green function. The evaluation of the nonlinear loadsmore » is based on explicit expressions derived by the fluid-impulse theory, which can be computed efficiently. Computations are presented of the linear and nonlinear loads on the MIT/NREL tension-leg platform. Comparisons were carried out with frequency-domain linear and second-order methods. Emphasis was placed on modeling accuracy of the magnitude of nonlinear low- and high-frequency wave loads in a sea state. Although fluid-impulse theory is applied to floating wind turbines in this paper, the theory is applicable to other offshore platforms as well.« less

Risk Estimation and Sexual Behaviour: A Longitudinal Study of 16- 21-year olds.

PubMed

Breakwell, G M; Breakwell, G M

1996-01-01

The relationships among risk estimation, impulsivity and patterns of sexual risk-taking in 16-21-year-olds are examined. A sample of 236 males and 340 females completed a postal questionnaire on three occasions at annual intervals. They reported their assessment of their own risk of HIV infection, the risk of HIV infection associated with six types of sexual activity, their likelihood of engaging in each of these activities, and whether they had participated in these activities between the first and second data collections. Impulsivity was indexed using a standard test. The data support the conclusion that strong social representations of sexual risks exist which do not markedly change during late adolescence. These risk estimates predict behavioural expectations, primarily for the riskiest behaviours, and for females (actual participation in vaginal sex); but for males, risk estimates fail to predict behaviour. Evidence here for a rational model of individual decision- making in relation to sexual risk- taking is sparse. Impulsivity was not a good predictor of expected or actual patterns of sexual behaviour, though higher impulsivity was associated with having more sexual partners and, in females, with starting to have sex younger.

Testing the Impulsiveness of Solar Flare Heating through Analysis of Dynamic Atmospheric Response

NASA Astrophysics Data System (ADS)

Newton, E. K.; Emslie, A. G.; Mariska, J. T.

1996-03-01

One crucial test of a solar flare energy transport model is its ability to reproduce the characteristics of the atmospheric motions inferred from soft X-ray line spectra. Using a recently developed diagnostic, the velocity differential emission measure (VDEM), we can obtain from observations a physical measure of the amount of soft X-ray mitting plasma flowing at each velocity, v, and hence the total momentum of the upflowing plasma, without approximation or parametric fitting. We have correlated solar hard X-ray emission profiles by the Yohkoh Hard X-ray telescope with the mass and momentum histories inferred from soft X-ray line profiles observed by the Yohkoh Bragg crystal spectrometers. For suitably impulsive hard X-ray emission, an analysis of the hydrodynamic equations predicts a proportionality between the hard X-ray intensity and the second time derivative of the soft X-ray mitting plasma's momentum. This relationship is borne out by an analysis of 18 disk-center impulsive flares of varying durations, thereby lending support to the hypothesis that a prompt energy deposition mechanism, such as an energetic electron flux, is indeed responsible for the soft X-ray response observed in the rise phase of sufficiently impulsive solar flares.

Selective and interactive effects of D2 receptor antagonism and positive allosteric mGluR4 modulation on waiting impulsivity.

PubMed

Isherwood, Sarah N; Robbins, Trevor W; Nicholson, Janet R; Dalley, Jeffrey W; Pekcec, Anton

2017-09-01

Metabotropic glutamate receptor 4 (mGluR4) and dopamine D 2 receptors are specifically expressed within the indirect pathway neurons of the striato-pallidal-subthalamic pathway. This unique expression profile suggests that mGluR4 and D 2 receptors may play a cooperative role in the regulation and inhibitory control of behaviour. We investigated this possibility by testing the effects of a functionally-characterised positive allosteric mGluR4 modulator, 4-((E)-styryl)-pyrimidin-2-ylamine (Cpd11), both alone and in combination with the D 2 receptor antagonist eticlopride, on two distinct forms of impulsivity. Rats were trained on the five-choice serial reaction time task (5-CSRTT) of sustained visual attention and segregated according to low, mid, and high levels of motor impulsivity (LI, MI and HI, respectively), with unscreened rats used as an additional control group. A separate group of rats was trained on a delay discounting task (DDT) to assess choice impulsivity. Systemic administration of Cpd11 dose-dependently increased motor impulsivity and impaired attentional accuracy on the 5-CSRTT in all groups tested. Eticlopride selectively attenuated the increase in impulsivity induced by Cpd11, but not the accompanying attentional impairment, at doses that had no significant effect on behavioural performance when administered alone. Cpd11 also decreased choice impulsivity on the DDT (i.e. increased preference for the large, delayed reward) and decreased locomotor activity. These findings demonstrate that mGluR4s, in conjunction with D 2 receptors, affect motor- and choice-based measures of impulsivity, and therefore may be novel targets to modulate impulsive behaviour associated with a number of neuropsychiatric syndromes. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Associations among types of impulsivity, substance use problems and neurexin-3 polymorphisms.

PubMed

Stoltenberg, Scott F; Lehmann, Melissa K; Christ, Christa C; Hersrud, Samantha L; Davies, Gareth E

2011-12-15

Some of the genetic vulnerability for addiction may be mediated by impulsivity. This study investigated relationships among impulsivity, substance use problems and six neurexin-3 (NRXN3) polymorphisms. Neurexins (NRXNs) are presynaptic transmembrane proteins that play a role in the development and function of synapses. Impulsivity was assessed with the Barratt Impulsiveness Scale Version 11 (BIS-11), the Boredom Proneness Scale (BPS) and the TIME paradigm; alcohol problems with the Michigan Alcoholism Screening Test (MAST); drug problems with the Drug Abuse Screening Test (DAST-20); and regular tobacco use with a single question. Participants (n=439 Caucasians, 64.7% female) donated buccal cells for genotyping. Six NRXN3 polymorphisms were genotyped: rs983795, rs11624704, rs917906, rs1004212, rs10146997 and rs8019381. A dual luciferase assay was conducted to determine whether allelic variation at rs917906 regulated gene expression. In general, impulsivity was significantly higher in those who regularly used tobacco and/or had alcohol or drug problems. In men, there were modest associations between rs11624704 and attentional impulsivity (p=0.005) and between rs1004212 and alcohol problems (p=0.009). In women, there were weak associations between rs10146997 and TIME estimation (p=0.03); and between rs1004212 and drug problems (p=0.03). The dual luciferase assay indicated that C and T alleles of rs917906 did not differentially regulate gene expression in vitro. Associations between impulsivity, substance use problems and polymorphisms in NRXN3 may be gender specific. Impulsivity is associated with substance use problems and may provide a useful intermediate phenotype for addiction. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

The High Power Electric Propulsion (HiPEP) Ion Thruster

NASA Technical Reports Server (NTRS)

Foster, John E.; Haag, Tom; Patterson, Michael; Williams, George J., Jr.; Sovey, James S.; Carpenter, Christian; Kamhawi, Hani; Malone, Shane; Elliot, Fred

2004-01-01

Practical implementation of the proposed Jupiter Icy Moon Orbiter (JIMO) mission, which would require a total delta V of approximately 38 km/s, will require the development of a high power, high specific impulse propulsion system. Initial analyses show that high power gridded ion thrusters could satisfy JIMO mission requirements. A NASA GRC-led team is developing a large area, high specific impulse, nominally 25 kW ion thruster to satisfy both the performance and the lifetime requirements for this proposed mission. The design philosophy and development status as well as a thruster performance assessment are presented.

Solar thermal rocket engine (STRE) thrust characteristics at the change of engine operation mode and of the flight vehicle attitude in the solar system

NASA Astrophysics Data System (ADS)

Kudrin, O. I.

1993-10-01

Relationships are presented which describe changes in the thrust and specific impulse of a solar thermal rocket engine due to a change in the flow rate of the working fluid (hydrogen). Expressions are also presented which describe the variation of the STRE thrust and specific impulse with the distance between the flight vehicle and the sun. Results of calculations are presented for an STRE with afterburning of the working fluid (hydrogen + oxygen) using hydrogen heating by solar energy to a temperature of 2360 K.

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

PubMed

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

2014-11-01

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. Copyright © 2013 Elsevier Ltd. All rights reserved.

Impulsivity-focused group intervention to reduce binge eating episodes in patients with binge eating disorder: study protocol of the randomised controlled IMPULS trial.

PubMed

Schag, Kathrin; Leehr, Elisabeth J; Martus, Peter; Bethge, Wolfgang; Becker, Sandra; Zipfel, Stephan; Giel, Katrin E

2015-12-18

The core symptom of binge eating disorder (BED) is recurrent binge eating that is accompanied by a sense of loss of control. BED is frequently associated with obesity, one of the main public health challenges today. Experimental studies deliver evidence that general trait impulsivity and disorder-specific food-related impulsivity constitute risk factors for BED. Cognitive-behavioural treatment (CBT) is deemed to be the most effective intervention concerning BED. We developed a group intervention based on CBT and especially focusing on impulsivity. We hypothesise that such an impulsivity-focused group intervention is able to increase control over impulsive eating behaviour, that is, reduce binge eating episodes, further eating pathology and impulsivity. Body weight might also be influenced in the long term. The present randomised controlled trial investigates the feasibility, acceptance and efficacy of this impulsivity-focused group intervention in patients with BED. We compare 39 patients with BED in the experimental group to 39 patients with BED in the control group at three appointments: before and after the group intervention and in a 3-month follow-up. Patients with BED in the experimental group receive 8 weekly sessions of the impulsivity-focused group intervention with 5-6 patients per group. Patients with BED in the control group receive no group intervention. The primary outcome is the binge eating frequency over the past 4 weeks. Secondary outcomes comprise further eating pathology, general impulsivity and food-related impulsivity assessed by eye tracking methodology, and body weight. Additionally, we assess binge eating and other impulsive behaviour weekly in process analyses during the time period of the group intervention. This study has been approved by the ethics committee of the medical faculty of Eberhard Karls University Tübingen and the University Hospital Tübingen. Data are monitored by the Centre of Clinical Studies, University Hospital Tübingen. German Clinical Trials Register, DRKS00007689, 14/01/2015, version from 11/06/2015, pre-results. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

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

PubMed Central

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

2014-01-01

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, dorsolateral and ventrolateral 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

Impulse control disorders and related behaviours (ICD-RBs) in Parkinson's disease patients: Assessment using "Questionnaire for impulsive-compulsive disorders in Parkinson's disease" (QUIP).

PubMed

Sharma, Ashish; Goyal, Vinay; Behari, Madhuri; Srivastva, Achal; Shukla, Garima; Vibha, Deepti

2015-01-01

There is limited data on the prevalence of impulse control disorder and related behaviors (ICD-RBs) in Indian patients with Parkinson's Disease (PD). In the context of potential genetic and environmental factors affecting the expression of ICD-RBs, studying other multiethnic populations may bring in-sights into the mechanisms of these disorders. To ascertain point prevalence estimate of ICD-RBs in Indian PD patients, using the validated "Questionnaire for Impulsive-Compulsive Disorders in Parkinson's disease (QUIP)" and to examine their association with Dopamine replacement therapy (DRT). This was a hospital based observational cross-sectional study. After taking informed consent, patients and their informants (spouse, or primary caregiver) were made to complete the QUIP, and were instructed to answer questions based on behaviors that occurred anytime during PD that lasted at least four consecutive weeks. Total of 299 patients participated in the study. At least one ICD-RB was present in 128 (42.8%), at least one Impulse control disorder (ICD) was present in 74 (24.75%) and at least one Impulse control related compulsive behaviour (ICRB) was present in 93 (31.1%) patients. Punding was the most frequent (12.4%) followed by hyper sexuality (11.04%), compulsive hobbyism (9.4%), compulsive shopping (8.4%), compulsive medication use (7.7%), compulsive eating (5.35%), walkabout (4%) and pathological gambling (3.3%). ≥ 2 ICD-RBs were observed in 15.7% of patients. After multivariate analysis, younger age of onset, being unmarried were specifically associated with presence of ICD. Longer disease duration was specifically associated with presence of ICRB. Whereas smoking and higher dopamine levodopa equivalent daily doses (DA LEDD) were associated with both presence of ICD and ICRB. Higher LD LEDD was specifically associated with presence of ICD-RB. Our study revealed a relatively higher frequency of ICD-RBs, probably because of the use of screening instrument and because we combined both ICDs and ICRBs. Also high proportion of DA use (81.6%) among our patients might be responsible. The role of genetic factors that might increase the risk of developing ICD-RBs in this population needs further exploration.

Modeling the state dependent impulse control for computer virus propagation under media coverage

NASA Astrophysics Data System (ADS)

Liang, Xiyin; Pei, Yongzhen; Lv, Yunfei

2018-02-01

A state dependent impulsive control model is proposed to model the spread of computer virus incorporating media coverage. By the successor function, the sufficient conditions for the existence and uniqueness of order-1 periodic solution are presented first. Secondly, for two classes of periodic solutions, the geometric property of successor function and the analogue of the Poincaré criterion are employed to obtain the stability results. These results show that the number of the infective computers is under the threshold all the time. Finally, the theoretic and numerical analysis show that media coverage can delay the spread of computer virus.

High speed cross-amplitude modulation in concatenated SOA-EAM-SOA.

PubMed

Cleary, Ciaran S; Manning, Robert J

2012-06-18

We observe a near-ideal high speed amplitude impulse response in an SOA-EAM-SOA configuration under optimum conditions. Full amplitude recovery times as low as 10 ps with modulation depths of 70% were observed in pump-probe measurements. System behavior could be controlled by the choice of signal wavelength, SOA current biases and EAM reverse bias voltages. Experimental data and impulse response modelling indicated that the slow tail in the gain response of first SOA was negated by a combination of cross-absorption modulation between pump and modulated CW probe, and self-gain modulation of the modulated CW probe in both the EAM and second SOA.

A Fast Method to Calculate the Spatial Impulse Response for 1-D Linear Ultrasonic Phased Array Transducers

PubMed Central

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

2016-01-01

A method is developed to accurately determine the spatial impulse response at the specifically discretized observation points in the radiated field of 1-D linear ultrasonic phased array transducers with great efficiency. In contrast, the previously adopted solutions only optimize the calculation procedure for a single rectangular transducer and required approximation considerations or nonlinear calculation. In this research, an algorithm that follows an alternative approach to expedite the calculation of the spatial impulse response of a rectangular linear array is presented. The key assumption for this algorithm is that the transducer apertures are identical and linearly distributed on an infinite rigid plane baffled with the same pitch. Two points in the observation field, which have the same position relative to two transducer apertures, share the same spatial impulse response that contributed from corresponding transducer, respectively. The observation field is discretized specifically to meet the relationship of equality. The analytical expressions of the proposed algorithm, based on the specific selection of the observation points, are derived to remove redundant calculations. In order to measure the proposed methodology, the simulation results obtained from the proposed method and the classical summation method are compared. The outcomes demonstrate that the proposed strategy can speed up the calculation procedure since it accelerates the speed-up ratio which relies upon the number of discrete points and the number of the array transducers. This development will be valuable in the development of advanced and faster linear ultrasonic phased array systems. PMID:27834799

The effects of violence exposure on the development of impulse control and future orientation across adolescence and early adulthood: Time-specific and generalized effects in a sample of juvenile offenders.

PubMed

Monahan, Kathryn C; King, Kevin M; Shulman, Elizabeth P; Cauffman, Elizabeth; Chassin, Laurie

2015-11-01

Impulse control and future orientation increase across adolescence, but little is known about how contextual factors shape the development of these capacities. The present study investigates how stress exposure, operationalized as exposure to violence, alters the developmental pattern of impulse control and future orientation across adolescence and early adulthood. In a sample of 1,354 serious juvenile offenders, higher exposure to violence was associated with lower levels of future orientation at age 15 and suppressed development of future orientation from ages 15 to 25. Increases in witnessing violence or victimization were linked to declines in impulse control 1 year later, but only during adolescence. Thus, beyond previous experiences of exposure to violence, witnessing violence and victimization during adolescence conveys unique risk for suppressed development of self-regulation.

The five-factor model of impulsivity-like traits and emotional lability in aggressive behavior.

PubMed

Dvorak, Robert D; Pearson, Matthew R; Kuvaas, Nicholas J

2013-01-01

Factors that increase automatic psychological processes may result in impulsive action and, consequently, aggressive behavior. The current cross-sectional study examined the association between the five-factor model of impulsivity-like traits (negative urgency, positive urgency, premeditation, perseverance, and sensation seeking), emotional lability, and physically aggressive behaviors among college students (n = 481) in a negative binomial hurdle model. In the logistic portion of the model, emotional lability was related to a higher likelihood of engaging in aggressive acts in the past 6 months. The association between emotional lability and the likelihood of aggressive behavior was moderated by two impulsivity-like traits: negative urgency and positive urgency. Specifically, emotional lability was related to engaging in aggressive acts among those with high negative urgency, and among those with low positive urgency. In the count portion of the model, emotional lability was uniquely related to the number of aggressive acts in the past 6 months. Our results indicate that emotional lability and facets of impulsivity interactively relate to engagement in aggressive behavior, suggesting that these variables be integrated into models of aggression. © 2013 Wiley Periodicals, Inc.

Elucidating Poor Decision-Making in a Rat Gambling Task

PubMed Central

Seriès, Peggy; Marchand, Alain R.; Dellu-Hagedorn, Françoise

2013-01-01

Although poor decision-making is a hallmark of psychiatric conditions such as attention deficit/hyperactivity disorder, pathological gambling or substance abuse, a fraction of healthy individuals exhibit similar poor decision-making performances in everyday life and specific laboratory tasks such as the Iowa Gambling Task. These particular individuals may provide information on risk factors or common endophenotypes of these mental disorders. In a rodent version of the Iowa gambling task – the Rat Gambling Task (RGT), we identified a population of poor decision makers, and assessed how these rats scored for several behavioral traits relevant to executive disorders: risk taking, reward seeking, behavioral inflexibility, and several aspects of impulsivity. First, we found that poor decision-making could not be well predicted by single behavioral and cognitive characteristics when considered separately. By contrast, a combination of independent traits in the same individual, namely risk taking, reward seeking, behavioral inflexibility, as well as motor impulsivity, was highly predictive of poor decision-making. Second, using a reinforcement-learning model of the RGT, we confirmed that only the combination of extreme scores on these traits could induce maladaptive decision-making. Third, the model suggested that a combination of these behavioral traits results in an inaccurate representation of rewards and penalties and inefficient learning of the environment. Poor decision-making appears as a consequence of the over-valuation of high-reward-high-risk options in the task. Such a specific psychological profile could greatly impair clinically healthy individuals in decision-making tasks and may predispose to mental disorders with similar symptoms. PMID:24339988

Elucidating poor decision-making in a rat gambling task.

PubMed

Rivalan, Marion; Valton, Vincent; Seriès, Peggy; Marchand, Alain R; Dellu-Hagedorn, Françoise

2013-01-01

Although poor decision-making is a hallmark of psychiatric conditions such as attention deficit/hyperactivity disorder, pathological gambling or substance abuse, a fraction of healthy individuals exhibit similar poor decision-making performances in everyday life and specific laboratory tasks such as the Iowa Gambling Task. These particular individuals may provide information on risk factors or common endophenotypes of these mental disorders. In a rodent version of the Iowa gambling task--the Rat Gambling Task (RGT), we identified a population of poor decision makers, and assessed how these rats scored for several behavioral traits relevant to executive disorders: risk taking, reward seeking, behavioral inflexibility, and several aspects of impulsivity. First, we found that poor decision-making could not be well predicted by single behavioral and cognitive characteristics when considered separately. By contrast, a combination of independent traits in the same individual, namely risk taking, reward seeking, behavioral inflexibility, as well as motor impulsivity, was highly predictive of poor decision-making. Second, using a reinforcement-learning model of the RGT, we confirmed that only the combination of extreme scores on these traits could induce maladaptive decision-making. Third, the model suggested that a combination of these behavioral traits results in an inaccurate representation of rewards and penalties and inefficient learning of the environment. Poor decision-making appears as a consequence of the over-valuation of high-reward-high-risk options in the task. Such a specific psychological profile could greatly impair clinically healthy individuals in decision-making tasks and may predispose to mental disorders with similar symptoms.

Impulse oscillometry: a measure for airway obstruction.

PubMed

Vink, Geraldine R; Arets, Hubertus G M; van der Laag, Johan; van der Ent, Cornelis K

2003-03-01

The impulse oscillometry system (IOS) was introduced as a new technique to assess airflow obstruction in patients who are not able to perform forced breathing maneuvers, e.g., subjects with cerebral palsy or severe mental retardation, and young children. This study evaluates the sensitivity and specificity of IOS parameters to quantify changes in airflow obstruction in comparison with forced expiratory volume in the first second (FEV(1)) and peak expiratory flow (PEF) measurements. Measurements of FEV(1), PEF, and resistance (R) and reactance (X) at frequencies of 5-35 Hz were performed in 19 children with asthma before, during, and after methacholine challenge and subsequent bronchodilatation. All parameters changed significantly during tests. Values of R5 and R10 correlated with FEV(1) (r = -0.71 and -0.73, respectively, P < 0.001), as did values of X5 and X10 (r = 0.52 and 0.57, respectively, P < 0.01). Changes in R preceded changes in PEF and FEV(1) during methacholine challenge. The area under the receiver operating characteristic (ROC) curve to predict a 15% fall in FEV(1) showed better sensitivity and specificity for R5 (area under the curve, 0.85) compared to PEF (0.79) or R10 (0.73). We conclude that IOS parameters can be easily used as an indirect measure of airflow obstruction. This might be helpful in patients who are not able to perform forced breathing maneuvers. In individual subjects, R values measured at 5 Hz showed to be superior to PEF measurements in the detection of a 15% fall in FEV(1). Copyright 2003 Wiley-Liss, Inc.

Solar Thermal Propulsion Improvements at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Gerrish, Harold P.

2003-01-01

Solar Thermal Propulsion (STP) is a concept which operates by transferring solar energy to a propellant, which thermally expands through a nozzle. The specific impulse performance is about twice that of chemical combustions engines, since there is no need for an oxidizer. In orbit, an inflatable concentrator mirror captures sunlight and focuses it inside an engine absorber cavity/heat exchanger, which then heats the propellant. The primary application of STP is with upperstages taking payloads from low earth orbit to geosynchronous earth orbit or earth escape velocities. STP engines are made of high temperature materials since heat exchanger operation requires temperatures greater than 2500K. Refractory metals such as tungsten and rhenium have been examined. The materials must also be compatible with hot hydrogen propellant. MSFC has three different engine designs, made of different refractory metal materials ready to test. Future engines will be made of high temperature carbide materials, which can withstand temperatures greater than 3000K, hot hydrogen, and provide higher performance. A specific impulse greater than 1000 seconds greatly reduces the amount of required propellant. A special 1 OkW solar ground test facility was made at MSFC to test various STP engine designs. The heliostat mirror, with dual-axis gear drive, tracks and reflects sunlight to the 18 ft. diameter concentrator mirror. The concentrator then focuses sunlight through a vacuum chamber window to a small focal point inside the STP engine. The facility closely simulates how the STP engine would function in orbit. The flux intensity at the focal point is equivalent to the intensity at a distance of 7 solar radii from the sun.

Early age of e-cigarette use onset mediates the association between impulsivity and e-cigarette use frequency in youth.

PubMed

Bold, Krysten W; Morean, Meghan E; Kong, Grace; Simon, Patricia; Camenga, Deepa R; Cavallo, Dana A; Krishnan-Sarin, Suchitra

2017-12-01

Identifying risk factors for youth e-cigarette use is critical, given high rates of e-cigarette use and unknown health effects of long-term use. The current study examined whether an early age of onset of e-cigarette use mediates the association between impulsivity and e-cigarette frequency. Cross-sectional survey data of e-cigarette users (n=927) were collected from 8 high schools in southeastern Connecticut. The sample was 44.7% female (mean age 16.2 [SD=1.2], mean age of e-cigarette onset 14.7 [SD=1.6]). Two domains of self-reported, trait impulsivity were assessed using the abbreviated Barratt Impulsiveness Scale: impaired self-regulation (e.g., problems with concentration or self-control) and behavioral impulsivity (e.g., doing things without thinking). Mediation was tested with Mplus, and the model included school as a cluster variable and controlled for covariates related to e-cigarette use (i.e., sex, age, race, peer use, and other tobacco products ever tried). The hypothesized mediation was supported for both domains of impulsivity (impaired self-regulation a 1 b=0.09, SE=0.02, 95%CI [0.03-0.14], p=.002; behavioral impulsivity a 2 b=0.07, SE=0.03, 95%CI [.01-.14], p=0.03). Specifically, impaired self-regulation (B=-0.33, SE=0.06, p<0.001) and behavioral impulsivity (B=-0.26, SE=0.11, p=0.02) predicted trying e-cigarettes at an earlier age, and earlier initiation was associated with more days of e-cigarette use in the past month (B=-0.28, SE=0.08, p<0.001). Adolescents who endorse aspects of impulsivity, such as acting without thinking, are at greater risk for more frequent e-cigarette use through an early age of e-cigarette initiation. Further research is needed to evaluate these relationships longitudinally and to develop targeted e-cigarette interventions for impulsive youth. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of Laterally Wedged Insoles on the External Knee Adduction Moment across Different Reference Frames.

PubMed

Yamaguchi, Satoshi; Kitamura, Masako; Ushikubo, Tomohiro; Murata, Atsushi; Akagi, Ryuichiro; Sasho, Takahisa

2015-01-01

Biomechanical effects of laterally wedged insoles are assessed by reduction in the knee adduction moment. However, the degree of reduction may vary depending on the reference frame with which it is calculated. The purpose of this study was to clarify the effect of reference frame on the reduction in the knee adduction moment by laterally wedged insoles. Twenty-nine healthy participants performed gait trials with a laterally wedged insole and with a flat insole as a control. The knee adduction moment, including the first and second peaks and the angular impulse, were calculated using four different reference frames: the femoral frame, tibial frame, laboratory frame and the Joint Coordinate System. There were significant effects of reference frame on the knee adduction moment first and second peaks (P < 0.001 for both variables), while the effect was not significant for the angular impulse (P = 0.84). No significant interaction between the gait condition and reference frame was found in either of the knee adduction moment variables (P = 0.99 for all variables), indicating that the effects of laterally wedged insole on the knee adduction moments were similar across the four reference frames. On the other hand, the average percent changes ranged from 9% to 16% for the first peak, from 16% to 18% for the second peak and from 17% to 21% for the angular impulse when using the different reference frames. The effects of laterally wedged insole on the reduction in the knee adduction moment were similar across the reference frames. On the other hand, Researchers need to recognize that when the percent change was used as the parameter of the efficacy of laterally wedged insole, the choice of reference frame may influence the interpretation of how laterally wedged insoles affect the knee adduction moment.

An algorithm on simultaneous optimization of performance and mass parameters of open-cycle liquid-propellant engine of launch vehicles

NASA Astrophysics Data System (ADS)

Eskandari, M. A.; Mazraeshahi, H. K.; Ramesh, D.; Montazer, E.; Salami, E.; Romli, F. I.

2017-12-01

In this paper, a new method for the determination of optimum parameters of open-cycle liquid-propellant engine of launch vehicles is introduced. The parameters affecting the objective function, which is the ratio of specific impulse to gross mass of the launch vehicle, are chosen to achieve maximum specific impulse as well as minimum mass for the structure of engine, tanks, etc. The proposed algorithm uses constant integration of thrust with respect to time for launch vehicle with specific diameter and length to calculate the optimum working condition. The results by this novel algorithm are compared to those obtained from using Genetic Algorithm method and they are also validated against the results of existing launch vehicle.

Theoretical Performance of Liquid Hydrogen with Liquid Oxygen as a Rocket Propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; McBride, Bonnie J.

1959-01-01

Theoretical rocket performance for both equilibrium and frozen composition during expansion was calculated for the propellant combination liquid hydrogen and liquid oxygen at four chamber pressures (60, 150, 300, and 600 lb/sq in. abs) and a wide range of pressure ratios (1 to 4000) and oxidant-fuel ratios (1.190 to 39.683). Data are given to estimate performance parameters at chamber pressures other than those for which data are tabulated. The parameters included are specific impulse, specific impulse in vacuum, combustion-chamber temperature, nozzle-exit temperature, molecular weight, molecular-weight derivatives, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, isentropic exponent, viscosity, thermal conductivity, Mach number, and equilibrium gas compositions.

Impulsivity and eating behavior in males

PubMed

Jáuregui-Lobera, Ignacio; Santiago, María José

2017-02-01

Introduction: Impulsivity is a personality trait related with the control of behaviour and emotions and it is found in different psychopathological alterations, including those referred to eating behaviour. Objective: The aim of this study was to analyse the relationship among the infl uence of the aesthetic body shape model, eating behaviour (and risk for specific disorders), body mass index and impulsivity. Method: A total of 178 males were included in the study, with a mean age of 20.18 ± 2.48. Height and weight were assessed in order to obtain the body mass index. All participants fulfilled the following questionnaires: Barratt Impulsivity Scale (BIS-11), Questionnaire of Infl uences on the Body Shape Model for males (CIMEC-V) and the Eating Attitudes Test (EAT-40). Results: With respect to possible cases of eating disorders, 5.06% were found. Scores of some items of BIS-11 correlated significantly with the EAT-40 and CIMEC-V scores. Overweight participants (39.89%) showed higher level of impulsivity as well as those with EAT-40 scores above the cut-off point for that test. Conclusions: The assessment of impulsivity from a psychological point of view might be a preventive tool with regards to disordered eating behaviours. Respecting the patients with eating disorders/overweight/obesity, that assessment might be a relevant aspect in order to improve the therapeutical approach.

Suicidality in temporal lobe epilepsy: measuring the weight of impulsivity and depression.

PubMed

de Oliveira, Guilherme Nogueira M; Kummer, Arthur; Salgado, João Vinícius; Filho, Gerardo Maria de Araújo; David, Anthony S; Teixeira, Antônio Lúcio

2011-12-01

The aim of the work described here was to measure the role of psychopathological features, specifically impulsivity and depression, in suicidality in patients with temporal lobe epilepsy (TLE). Neuropsychiatric evaluation of 66 outpatients with TLE was performed with the following instruments: a structured clinical interview (Mini International Neuropsychiatric Interview Plus), the Barratt Impulsiveness Scale, the Hamilton Anxiety Scale, the Beck Depression Inventory, and the Brief Psychiatric Rating Scale. A current Axis I psychiatric diagnosis, mainly mood and anxiety disorders, was assigned to 37 subjects (56.1%) Presence of suicide risk was identified in 19 patients (28.8%), and 14 (21.2%) had attempted suicide. Frequency of seizures (P=0.012), current major depression (P=0.001), and motor impulsivity (P=0.005) were associated with suicide risk on univariate analysis. Logistic regression stressed the main relevance of major depression (OR=12.82, 95% CI=2.58-63.76, P=0.002) and motor impulsivity (OR=1.21, 95% CI=1.06-1.38, P=0.005) to suicide risk. Depression has a major influence on suicidality in epilepsy. Motor impulsivity is also relevant and may be an important component of depression in TLE associated with suicide risk. Copyright © 2011 Elsevier Inc. All rights reserved.

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

PubMed

Rickson, Daphne J

2006-01-01

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.

Correlates of Non-suicidal Self-Injury and Suicide Attempts in Bulimic Spectrum Disorders

PubMed Central

Gómez-Expósito, Alexandra; Wolz, Ines; Fagundo, Ana B.; Granero, Roser; Steward, Trevor; Jiménez-Murcia, Susana; Agüera, Zaida; Fernández-Aranda, Fernando

2016-01-01

Objective: The aim of this study was to examine the implication of personality, impulsivity, and emotion regulation difficulties in patients with a bulimic-spectrum disorder (BSD) and suicide attempts (SA), BSD patients with non-suicidal self-injury (NSSI), and BSD patients without these behaviors. Method: One hundred and twenty-two female adult BSD patients were assessed using self-report questionnaires. Patients were clustered post-hoc into three groups depending on whether they presented BSD without NSSI or SA (BSD), BSD with lifetime NSSI (BSD + NSSI) or BSD with lifetime SA (BSD + SA). Results: The BSD + NSSI and BSD + SA groups presented more emotion regulation difficulties, more eating and general psychopathology, and increased reward dependence in comparison with the BSD group. In addition, BSD + SA patients specifically showed problems with impulse control, while also presenting higher impulsivity than both the BSD and BSD + NSSI groups. No differences in impulsivity between the BSD and BSD + NSSI groups were found. Conclusions: The results show that BSD + NSSI and BSD + SA share a common profile characterized by difficulties in emotion regulation and low reward dependence, but differ in impulsivity and cooperativeness. This suggests that self-injury, in patients without a history of suicide attempts (i.e., BSD + NSSI), may have a regulatory role rather than being due to impulsivity. PMID:27597836

Psychometric Evaluation of the Substance Use Risk Profile Scale (SURPS) in an Inpatient Sample of Substance Users Using Cue-Reactivity Methodology

PubMed Central

Schlauch, Robert C.; Crane, Cory A.; Houston, Rebecca J.; Molnar, Danielle S.; Schlienz, Nicolas J.; Lang, Alan R.

2015-01-01

The current project sought to examine the psychometric properties of a personality based measure (Substance Use Risk Profile Scale; SURPS: introversion-hopelessness, anxiety sensitivity, impulsivity, and sensation seeking) designed to differentially predict substance use preferences and patterns by matching primary personality-based motives for use to the specific effects of various psychoactive substances. Specifically, we sought to validate the SURPS in a clinical sample of substance users using cue reactivity methodology to assess current inclinations to consume a wide range of psychoactive substances. Using confirmatory factor analysis and correlational analyses, the SURPS demonstrated good psychometric properties and construct validity. Further, impulsivity and sensation-seeking were associated with use of multiple substances but could be differentiated by motives for use and susceptibility to the reinforcing effects of stimulants (i.e., impulsivity) and alcohol (i.e. sensation-seeking). In contrast, introversion-hopelessness and anxiety sensitivity demonstrated a pattern of use more focused on reducing negative affect, but were not differentiated based on specific patterns of use. Taken together, results suggests that among those receiving inpatient treatment for substance use disorders, the SURPS is a valid instrument for measuring four distinct personality dimensions that may be sensitive to motivational susceptibilities to specific patterns of alcohol and drug use. PMID:26052180

A Twin Study of ADHD Symptoms in Early Adolescence: Hyperactivity-Impulsivity and Inattentiveness Show Substantial Genetic Overlap but Also Genetic Specificity

ERIC Educational Resources Information Center

Greven, Corina U.; Rijsdijk, Fruhling V.; Plomin, Robert

2011-01-01

A previous paper in this journal revealed substantial genetic overlap between the ADHD dimensions of hyperactivity-impulsivity and inattentiveness in a sample of 8-year old twins drawn from a UK-representative population sample. Four years later, when the twins were 12 years old, more than 5,500 pairs drawn from the same sample were rated again on…

Dietary restraint and impulsivity modulate neural responses to food in adolescents with obesity and healthy adolescents.

PubMed

Hofmann, Johannes; Ardelt-Gattinger, Elisabeth; Paulmichl, Katharina; Weghuber, Daniel; Blechert, Jens

2015-11-01

Despite alarming prevalence rates, surprisingly little is known about neural mechanisms underlying eating behavior in juveniles with obesity. To simulate reactivity to modern food environments, event-related potentials (ERP) to appetizing food images (relative to control images) were recorded in adolescents with obesity and healthy adolescents. Thirty-four adolescents with obesity (patients) and 24 matched healthy control adolescents watched and rated standardized food and object images during ERP recording. Personality (impulsivity) and eating styles (trait craving and dietary restraint) were assessed as potential moderators. Food relative to object images triggered larger early (P100) and late (P300) ERPs. More impulsive individuals had considerably larger food-specific P100 amplitudes in both groups. Controls with higher restraint scores showed reduced food-specific P300 amplitudes and subjective palatability ratings whereas patients with higher restraint scores showed increased P300 and palatability ratings. This first ERP study in adolescents with obesity and controls revealed impulsivity as a general risk factor in the current obesogenic environment by increasing food-cue salience. Dietary restraint showed paradoxical effects in patients, making them more vulnerable to visual food-cues. Salutogenic therapeutic approaches that deemphasize strict dietary restraint and foster healthy food choice might reduce such paradoxical effects. © 2015 The Obesity Society.

An interpretation of the polarization of microwave bursts. [solar emission

NASA Technical Reports Server (NTRS)

Kundu, M. R.; Vlahos, L.

1979-01-01

High-spatial-resolution (a few seconds of arc) observations of microwave bursts have demonstrated that only the impulsive phase of the burst is polarized; one observes only one polarity in the burst source if it is weak (Alissandrakis and Kundu) and both polarities if it is intense (Enome et al.). These results are interpreted in terms of an asymmetrical bipolar field structure of the loop in which the energetic electrons responsible for the radiation are contained. The role of unequal field strengths at the feet of the loop on the number of electrons trapped and their pitch angle distribution are discussed in a specific model. Computations of the polarized intensity originating from each foot of the loop seem to be consistent with the observations at present available.

Upper Stage Flight Experiment 10K Engine Design and Test Results

NASA Technical Reports Server (NTRS)

Ross, R.; Morgan, D.; Crockett, D.; Martinez, L.; Anderson, W.; McNeal, C.

2000-01-01

A 10,000 lbf thrust chamber was developed for the Upper Stage Flight Experiment (USFE). This thrust chamber uses hydrogen peroxide/JP-8 oxidizer/fuel combination. The thrust chamber comprises an oxidizer dome and manifold, catalyst bed assembly, fuel injector, and chamber/nozzle assembly. Testing of the engine was done at NASA's Stennis Space Center (SSC) to verify its performance and life for future upper stage or Reusable Launch Vehicle applications. Various combinations of silver screen catalyst beds, fuel injectors, and combustion chambers were tested. Results of the tests showed high C* efficiencies (97% - 100%) and vacuum specific impulses of 275 - 298 seconds. With fuel film cooling, heating rates were low enough that the silica/quartz phenolic throat experienced minimal erosion. Mission derived requirements were met, along with a perfect safety record.

The Relationship Between Social Affect and Restricted and Repetitive Behaviors Measured on the ADOS-2 and Maternal Stress.

PubMed

Schutte, Claire; Richardson, Wendy; Devlin, Morgan; Hill, Jeanna; Ghossainy, Maliki; Hewitson, Laura

2018-03-01

This study investigated categories of autism spectrum disorder (ASD) symptoms measured by the Autism Diagnostic Observation Schedule-Second Edition and their association with maternal stress. Social affect and restricted and repetitive behaviors were compared with levels of maternal stress, measured by the Parenting Stress Index, in 102 children with ASD ages 2-12 years of age. Results indicated that social affect and restricted and repetitive behaviors were associated with the mother's stress regarding acceptability of the child's condition. Additionally, restricted and repetitive behaviors were significantly related to stress involving the child's hyperactivity and impulsivity. These findings highlight specific areas of stress experienced by mothers of children with ASD that are related to the child's symptoms, providing information for caregiver support and intervention.

Nuclear electric propulsion stage requirements and description

NASA Technical Reports Server (NTRS)

Mondt, J. F.; Peelgren, M. L.; Nakashima, A. M.; Nsieh, T. M.; Phillips, W. M.; Kikin, G. M.

1974-01-01

The application of a nuclear electric propulsion (NEP) stage in the exploration of near-earth, cometary, and planetary space was discussed. The NEP stage is powered by a liquid-metal-cooled, fast spectrum thermionic reactor capable of providing 120 kWe for 20,000 hours. This power is used to drive a number of mercury ion bombardment thrusters with specific impulse in the range of 4000-5000 seconds. The NEP description, characteristics, and functional requirements are discussed. These requirements are based on a set of five coordinate missions, which are described in detail. These five missions are a representative part of a larger set of missions used as a basic for an advanced propulsion comparison study. Additionally, the NEP stage development plan and test program is outlined and a schedule presented.

Laser-energized MHD generator for hypersonic electric air-turborockets

NASA Technical Reports Server (NTRS)

Myrabo, L. N.; Rosa, R. J.; Moder, J. P.; Blandino, J. S.; Frazier, S. R.

1987-01-01

The analysis and design of an open cycle Faraday MHD generator suitable for use in an electric air-turborocket cycle, the MHD-fanjet, is presented. The working fluid for the generators is unseeded high temperature hydrogen, generated by a standing, laser-supported combustion wave. This study also examines the performance of an advanced combined-cycle engine, powered by beamed energy, proposed for use in future SSTO aerospacecraft. This innovative engine incorporates the MHD-fanjet for the acceleration role within the hypersonic flight regime, from about Mach 11 to above Mach 25. Performance results indicate that specific impulses could fall in the range of 10,000 to 16,000 seconds. This would enable propellant mass fractions as low as 6 percent to 9 percent for such advanced shuttlecraft flying SSTO missions to low earth orbit.

The Liquid Annular Reactor System (LARS) propulsion

NASA Technical Reports Server (NTRS)

Powell, James; Ludewig, Hans; Horn, Frederick; Lenard, Roger

1990-01-01

A concept for very high specific impulse (greater than 2000 seconds) direct nuclear propulsion is described. The concept, termed the liquid annular reactor system (LARS), uses liquid nuclear fuel elements to heat hydrogen propellant to very high temperatures (approximately 6000 K). Operating pressure is moderate (approximately 10 atm), with the result that the outlet hydrogen is virtually 100 percent dissociated to monatomic H. The molten fuel is contained in a solid container of its own material, which is rotated to stabilize the liquid layer by centripetal force. LARS reactor designs are described, together with neutronic and thermal-hydraulic analyses. Power levels are on the order of 200 megawatts. Typically, LARS designs use seven rotating fuel elements, are beryllium moderated, and have critical radii of approximately 100 cm (core L/D approximately equal to 1.5).

Advertising, marketing and purchase behavior for energy-related products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tiedemann, K.; Nelson, D.

Energy conservation programs have relied heavily on incentives and regulatory standards to reduce residential energy consumption. However, in the changing market environment characterized by competitive pressures, alternative mechanisms such as marketing and promotions may increase substantially in importance compared to the demand-side management programs which have been the focus of most research. This paper describes the role of marketing and promotions in encouraging energy efficiency at the household level in British Columbia. The paper examines three related issues: first, the purchase process for energy-related products; second, the criteria used by customers in making purchase decisions; and third, the impact andmore » effectiveness of alternative marketing tools. A key finding is the energy-related purchases do not fall into the impulse purchase category. There are two reasons for this: first, most of these products require installation and this requires a high level of commitment on the part of the purchaser; second, many energy-related products require a significant outlay of funds and this reduces impulse buying.« less

A new class of solar burst with MM-wave emission but only at the highest frequency (90 GHz)

NASA Technical Reports Server (NTRS)

Kaufmann, P.; Correia, E.; Costa, J. E. R.; Vaz, A. M. Z.; Dennis, B. R.

1984-01-01

High sensitivity and high time resolution solar observations at 90 GHz (lambda = 3.3 mm) have identified a unique impulsive burst on May 21, 1984 with emission that was more intense at this frequency than at lower frequencies. The first major time structure of the burst was over 10 times more intense at 90 GHz than at 30 GHz, 7 GHz, or 2.8 GHz.Only 6 seconds later, the 30 GHz impulsive structures started to be observed but still with lower intensity than at 90 GHz. Hard X-ray time structures at energies above 25 keV were almost identical to the 90 GHZ structures (to better than one second). All 90 GHz major time structures consisted of trains of multiple subsecond pulses with rise times as short as 0.03 sec and amplitudes large compared to the mean flux. When detectable, the 30 GHz subsecond pulses had smaller relative amplitude and were in phase with the corresponding 90 GHz pulses.

Female impulsive aggression: a sleep research perspective.

PubMed

Lindberg, Nina; Tani, Pekka; Putkonen, Hanna; Sailas, Eila; Takala, Pirjo; Eronen, Markku; Virkkunen, Matti

2009-01-01

The rate of violent crimes among girls and women appears to be increasing. One in every five female prisoners has been reported to have antisocial personality disorder. However, it has been quite unclear whether the impulsive, aggressive behaviour among women is affected by the same biological mechanisms as among men. Psychiatric sleep research has attempted to identify diagnostically sensitive and specific sleep patterns associated with particular disorders. Most psychiatric disorders are typically characterized by a severe sleep disturbance associated with decreased amounts of slow wave sleep (SWS), the physiologically significant, refreshing part of sleep. Among men with antisocial behaviour with severe aggression, on the contrary, increased SWS has been reported, reflecting either specific brain pathology or a delay in the normal development of human sleep patterns. In our preliminary study among medication-free, detoxified female homicidal offenders with antisocial personality disorder, the same profound abnormality in sleep architecture was found. From the perspective of sleep research, the biological correlates of severe impulsive aggression seem to share similar features in both sexes.

From Bethe–Salpeter Wave functions to Generalised Parton Distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mezrag, C.; Moutarde, H.; Rodríguez-Quintero, J.

2016-06-06

We review recent works on the modelling of Generalised Parton Distributions within the Dyson-Schwinger formalism. We highlight how covariant computations, using the impulse approximation, allows one to fulfil most of the theoretical constraints of the GPDs. A specific attention is brought to chiral properties and especially the so-called soft pion theorem, and its link with the Axial-Vector Ward-Takahashi identity. The limitation of the impulse approximation are also explained. Beyond impulse approximation computations are reviewed in the forward case. Finally, we stress the advantages of the overlap of lightcone wave functions, and possible ways to construct covariant GPD models within thismore » framework, in a two-body approximation« less

Personality correlates of aggression: evidence from measures of the five-factor model, UPPS model of impulsivity, and BIS/BAS.

PubMed

Miller, Joshua D; Zeichner, Amos; Wilson, Lauren F

2012-09-01

Although many studies of personality and aggression focus on multidimensional traits and higher order personality disorders (e.g., psychopathy), lower order, unidimensional traits may provide more precision in identifying specific aspects of personality that relate to aggression. The current study includes a comprehensive measurement of lower order personality traits in relation to three forms of aggression: reactive, proactive, and relational. Traits related to interpersonal antagonism and impulsivity, especially impulsive behavior in the context of negative affect, were consistently related to aggression across multiple indices. These findings suggest that certain lower order traits are of critical importance to understanding who engages in aggressive behavior and why this behavior occurs.

Negative urgency mediates the relationship between childhood maltreatment and problems with alcohol and cannabis in late adolescence

PubMed Central

Wardell, Jeffrey D.; Strang, Nicole M.; Hendershot, Christian S.

2017-01-01

Background Childhood maltreatment is an important risk factor for problems with alcohol and other drugs such as cannabis. Although this link has been well established, the mechanisms in this association require further study. High levels of impulsivity and difficulties with emotion regulation are often associated with childhood maltreatment. Negative urgency – an emotion-based facet of impulsivity – is a strong predictor of substance use problems and may be a particularly relevant facet of impulsivity in the link between childhood maltreatment and alcohol and cannabis outcomes. However, few studies have examined the specific mediational pathway from childhood maltreatment to alcohol and cannabis problems through negative urgency. Objectives We tested the hypothesis that the associations between history of childhood maltreatment and current alcohol and cannabis problems would be mediated by negative urgency, but not other facets of impulsivity. Methods Participants (N=232), who were in late adolescence (mean age=19.75), completed self-report measures of different facets of impulsivity, past childhood maltreatment, and current alcohol and cannabis use and problems. Results In analyses including several facets of impulsivity as simultaneous mediators, negative urgency was the only facet to mediate the associations of childhood maltreatment severity with alcohol and cannabis problems. Conclusions These findings provide support for negative urgency as a unique mediator of the association between childhood maltreatment and both alcohol and cannabis problems, suggesting that future work on mechanisms in this association should focus on mood-based impulsivity. PMID:26774820

BMI predicts emotion-driven impulsivity and cognitive inflexibility in adolescents with excess weight.

PubMed

Delgado-Rico, Elena; Río-Valle, Jacqueline S; González-Jiménez, Emilio; Campoy, Cristina; Verdejo-García, Antonio

2012-08-01

Adolescent obesity is increasingly viewed as a brain-related dysfunction, whereby reward-driven urges for pleasurable foods "hijack" response selection systems, such that behavioral control progressively shifts from impulsivity to compulsivity. In this study, we aimed to examine the link between personality factors (sensitivity to reward (SR) and punishment (SP), BMI, and outcome measures of impulsivity vs. flexibility in--otherwise healthy--excessive weight adolescents. Sixty-three adolescents (aged 12-17) classified as obese (n = 26), overweight (n = 16), or normal weight (n = 21) participated in the study. We used psychometric assessments of the SR and SP motivational systems, impulsivity (using the UPPS-P scale), and neurocognitive measures with discriminant validity to dissociate inhibition vs. flexibility deficits (using the process-approach version of the Stroop test). We tested the relative contribution of age, SR/SP, and BMI on estimates of impulsivity and inhibition vs. switching performance using multistep hierarchical regression models. BMI significantly predicted elevations in emotion-driven impulsivity (positive and negative urgency) and inferior flexibility performance in adolescents with excess weight--exceeding the predictive capacity of SR and SP. SR was the main predictor of elevations in sensation seeking and lack of premeditation. These findings demonstrate that increases in BMI are specifically associated with elevations in emotion-driven impulsivity and cognitive inflexibility, supporting a dimensional path in which adolescents with excess weight increase their proneness to overindulge when under strong affective states, and their difficulties to switch or reverse habitual behavioral patterns.

Dopamine D2/3- and μ-opioid receptor antagonists reduce cue-induced responding and reward impulsivity in humans.

PubMed

Weber, S C; Beck-Schimmer, B; Kajdi, M-E; Müller, D; Tobler, P N; Quednow, B B

2016-07-05

Increased responding to drug-associated stimuli (cue reactivity) and an inability to tolerate delayed gratification (reward impulsivity) have been implicated in the development and maintenance of drug addiction. Whereas data from animal studies suggest that both the dopamine and opioid system are involved in these two reward-related processes, their role in humans is less clear. Moreover, dopaminergic and opioidergic drugs have not been directly compared with regard to these functions, even though a deeper understanding of the underlying mechanisms might inform the development of specific treatments for elevated cue reactivity and reward impulsivity. In a randomized, double-blind, between-subject design we administered the selective dopamine D2/D3 receptor antagonist amisulpride (400 mg, n=41), the unspecific opioid receptor antagonist naltrexone (50 mg, n=40) or placebo (n=40) to healthy humans and measured cue-induced responding with a Pavlovian-instrumental transfer task and reward impulsivity with a delay discounting task. Mood was assessed using a visual analogue scale. Compared with placebo, amisulpride significantly suppressed cue-induced responding and reward impulsivity. The effects of naltrexone were similar, although less pronounced. Both amisulpride and naltrexone decreased average mood ratings compared with placebo. Our results demonstrate that a selective blockade of dopamine D2/D3 receptors reduces cue-induced responding and reward impulsivity in healthy humans. Antagonizing μ-opioid receptors has similar effects for cue-induced responding and to a lesser extent for reward impulsivity.

Associations Between Self-Control, Practice, and Skill Level in Sport Expertise Development.

PubMed

Tedesqui, Rafael A B; Young, Bradley W

2017-03-01

The purpose of this study was to test the association between self-control (SC) variables and (a) sport-specific practice amounts, (b) engagement in various practice contexts, (c) threats to commitment to one's sport, and (d) skill development using the Brief Self-Control Scale (BSCS) in a diverse sport sample. Two hundred forty-four athletes (47% female; M age  = 21.96 years, SD = 6.98 years; 68.8% individual sports and 31.2% team sports; 13.77 [SD = 8.12] hr/week of sport-specific practice) completed a survey composed of the BSCS and practice-related measures. Three skill groups (basic/intermediate, advanced, expert) were informed by athletes' self-reported highest level of competition. Separate analyses were conducted for juniors (aged 12-17 years) and seniors (aged 18-43 years). A 2-factor model (self-discipline and impulse control) fit the BSCS data. Fewer thoughts of quitting from one's sport were associated with higher self-discipline in juniors and seniors and were also related to higher impulse control in seniors. Greater practice amounts were associated with higher self-discipline; however, only seniors showed such associations in voluntary practice contexts. For juniors and seniors, impulse control was associated with more voluntary practicing. There were, however, no skill-group differences for levels of self-discipline or impulse control. Self-discipline and impulse control may be dispositional characteristics associated with how athletes engage in practice and avert conditions that threaten their sport commitment. SC dispositions may relate to practice amounts differently in juniors and seniors, depending on the requirements for self-regulation in a practice context.

Distinct dimensions defining the Adult ADHD Self-Report Scale: Implications for assessing inattentive and hyperactive/impulsive symptoms.

PubMed

Stanton, Kasey; Forbes, Miriam K; Zimmerman, Mark

2018-06-07

There has been growing interest in studying attention-deficit/hyperactivity disorder (ADHD) in adulthood as a result of research indicating that ADHD often persists into adulthood and frequently is comorbid with other psychiatric disorders. Adult ADHD symptoms are most commonly assessed via self-report, but prior research examining the structure of self-reported adult ADHD symptoms has yielded discrepant results. Explicating the factor structure of ADHD symptom measures is essential to determine if such self-report measures assess symptom dimensions showing distinctive relations with other psychopathology and psychosocial functioning. Consequently, we examined the structure of adult ADHD symptoms in a large sample of adult outpatients (N = 1,094). Symptoms were assessed via the Adult ADHD Self-Report Scale (ASRS; Kessler et al., 2005), which has become the most widely used self-report ADHD measure. Additionally, we extended prior research by examining the relations for emergent ADHD dimensions with other psychopathology and psychosocial impairment. Results indicated that the ASRS's items define a bifactor structure with specific dimensions of inattentiveness, motor hyperactivity/impulsivity, and verbal hyperactivity/impulsivity. Our results indicate that specific ADHD factors show distinctive relations in some ways. For example, verbal hyperactivity/impulsivity showed negative relations with major depressive disorder, whereas inattentiveness showed positive relations with major depression. These results highlight the need for future research determining the extent to which making distinctions among various ADHD symptom types (i.e., distinguishing motor and verbal hyperactivity/impulsivity) is empirically warranted and clinically useful. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Spatially adapted second-order total generalized variational image deblurring model under impulse noise

NASA Astrophysics Data System (ADS)

Zhong, Qiu-Xiang; Wu, Chuan-Sheng; Shu, Qiao-Ling; Liu, Ryan Wen

2018-04-01

Image deblurring under impulse noise is a typical ill-posed problem which requires regularization methods to guarantee high-quality imaging. L1-norm data-fidelity term and total variation (TV) regularizer have been combined to contribute the popular regularization method. However, the TV-regularized variational image deblurring model often suffers from the staircase-like artifacts leading to image quality degradation. To enhance image quality, the detailpreserving total generalized variation (TGV) was introduced to replace TV to eliminate the undesirable artifacts. The resulting nonconvex optimization problem was effectively solved using the alternating direction method of multipliers (ADMM). In addition, an automatic method for selecting spatially adapted regularization parameters was proposed to further improve deblurring performance. Our proposed image deblurring framework is able to remove blurring and impulse noise effects while maintaining the image edge details. Comprehensive experiments have been conducted to demonstrate the superior performance of our proposed method over several state-of-the-art image deblurring methods.

The pull in olympic weightlifting.

PubMed

Enoka, R M

1979-01-01

Data from five experienced weightlifters on the vertical forces applied to the barbell and system (barbell and lifter) during the pull were in excellent agreement with earlier displacement-time descriptions of the double knee bend as consisting of two stages of extension interrupted by a period of realignment (second knee bend). The vertical component of the ground reaction force (Rz) consisted of three phases: Weighting I, Unweighting, and Weighting II. The relative magnitude of the Rz impulse with respect to the system weight impulse (as an indicant of the proportion of the Rz impulse contributing to system acceleration) ranged from 118--141% for Weighting I, 74--89% for Unweighting, and 122--135% for Weighting II. In agreement with published theoretical calculations the most experienced and successful lifter produced the larger phase of positive acceleration first. The rebending of the knees was associated with the Unweighting phase. Although this latter interval corresponded to a phase of barbell deceleration, it appeared that the concomitant enhancement of the back, hip, and knee extensor activity outweighed any adverse effects.

Solar Flare Impulsive Phase Observations from SDO and Other Observatories

NASA Technical Reports Server (NTRS)

Chamberlin, Phillip C.; Woods, Thomas N.; Schrijver, Karel; Warren, Harry; Milligan, Ryan; Christe, Steven; Brosius, Jeffrey W.

2010-01-01

With the start of normal operations of the Solar Dynamics Observatory in May 2010, the Extreme ultraviolet Variability Experiment (EVE) and the Atmospheric Imaging Assembly (AIA) have been returning the most accurate solar XUV and EUV measurements every 10 and 12 seconds, respectively, at almost 100% duty cycle. The focus of the presentation will be the solar flare impulsive phase observations provided by EVE and AIA and what these observations can tell us about the evolution of the initial phase of solar flares. Also emphasized throughout is how simultaneous observations with other instruments, such as RHESSI, SOHO-CDS, and HINODE-EIS, will help provide a more complete characterization of the solar flares and the evolution and energetics during the impulsive phase. These co-temporal observations from the other solar instruments can provide information such as extending the high temperature range spectra and images beyond that provided by the EUV and XUV wavelengths, provide electron density input into the lower atmosphere at the footpoints, and provide plasma flows of chromospheric evaporation, among other characteristics.

The Effect of Citicoline Supplementation on Motor Speed and Attention in Adolescent Males.

PubMed

McGlade, Erin; Agoston, Anna Monica; DiMuzio, Jennifer; Kizaki, Miho; Nakazaki, Eri; Kamiya, Toshikazu; Yurgelun-Todd, Deborah

2015-07-15

This study assessed the effects of citicoline, a nutraceutical, on attention, psychomotor function, and impulsivity in healthy adolescent males. Seventy-five healthy adolescent males were randomly assigned to either the citicoline group (n = 51 with 250 or 500 mg citicoline) or placebo (n = 24). Participants completed the Ruff 2&7 Selective Attention Test, Finger Tap Test, and the Computerized Performance Test, Second Edition (CPT-II) at baseline and after 28 days of supplementation. Individuals receiving citicoline exhibited improved attention (p = 0.02) and increased psychomotor speed (p = 0.03) compared with those receiving placebo. Higher weight-adjusted dose significantly predicted increased accuracy on an attention task (p = 0.01), improved signal detectability on a computerized attention task (p = 0.03), and decreased impulsivity (p = 0.01). Adolescent males receiving 28 days of Cognizin® citicoline showed improved attention and psychomotor speed and reduced impulsivity compared to adolescent males who received placebo. © 2015 SAGE Publications.

Thin film eddy current impulse deicer

NASA Technical Reports Server (NTRS)

Smith, Samuel O.; Zieve, Peter B.

1990-01-01

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.

Impulse generation by detonation tubes

NASA Astrophysics Data System (ADS)

Cooper, Marcia Ann

Impulse generation with gaseous detonation requires conversion of chemical energy into mechanical energy. This conversion process is well understood in rocket engines where the high pressure combustion products expand through a nozzle generating high velocity exhaust gases. The propulsion community is now focusing on advanced concepts that utilize non-traditional forms of combustion like detonation. Such a device is called a pulse detonation engine in which laboratory tests have proven that thrust can be achieved through continuous cyclic operation. Because of poor performance of straight detonation tubes compared to conventional propulsion systems and the success of using nozzles on rocket engines, the effect of nozzles on detonation tubes is being investigated. Although previous studies of detonation tube nozzles have suggested substantial benefits, up to now there has been no systematic investigations over a range of operating conditions and nozzle configurations. As a result, no models predicting the impulse when nozzles are used exist. This lack of data has severely limited the development and evaluation of models and simulations of nozzles on pulse detonation engines. The first experimental investigation measuring impulse by gaseous detonation in plain tubes and tubes with nozzles operating in varying environment pressures is presented. Converging, diverging, and converging-diverging nozzles were tested to determine the effect of divergence angle, nozzle length, and volumetric fill fraction on impulse. The largest increases in specific impulse, 72% at an environment pressure of 100 kPa and 43% at an environment pressure of 1.4 kPa, were measured with the largest diverging nozzle tested that had a 12° half angle and was 0.6 m long. Two regimes of nozzle operation that depend on the environment pressure are responsible for these increases and were first observed from these data. To augment this experimental investigation, all data in the literature regarding partially filled detonation tubes was compiled and analyzed with models investigating concepts of energy conservation and unsteady gas dynamics. A model to predict the specific impulse was developed for partially filled tubes. The role of finite chemical kinetics in detonation products was examined through numerical simulations of the flow in nonsteady expansion waves.

Theoretical Performance of Hydrogen-Oxygen Rocket Thrust Chambers

NASA Technical Reports Server (NTRS)

Sievers, Gilbert K.; Tomazic, William A.; Kinney, George R.

1961-01-01

Data are presented for liquid-hydrogen-liquid-oxygen thrust chambers at chamber pressures from 15 to 1200 pounds per square inch absolute, area ratios to approximately 300, and percent fuel from about 8 to 34 for both equilibrium and frozen composition during expansion. Specific impulse in vacuum, specific impulse, combustion-chamber temperature, nozzle-exit temperature, characteristic velocity, and the ratio of chamber-to-nozzle-exit pressure are included. The data are presented in convenient graphical forms to allow quick calculation of theoretical nozzle performance with over- or underexpansion, flow separation, and introduction of the propellants at various initial conditions or heat loss from the combustion chamber.

Performance characteristics of quasi-steady MPD discharges. [spacecraft plasma propulsion thrust efficiency and specific impulse

NASA Technical Reports Server (NTRS)

Rudolph, L. K.; Jahn, R. G.; Clark, K. E.; Von Jaskowsky, W. F.

1976-01-01

The onset of voltage fluctuations in a multi-megawatt quasi-steady MPD accelerator, indicative of increased cathode ablation and a consequent degradation of performance, is found to be a function of cathode size. With longer cathodes, this onset shifts to substantially higher powers per unit mass flow and the plasma exhaust velocity can be increased to values previously thought inaccessible to accelerators of this class. Centerline velocities up to 30 km/sec have been measured in argon, which for the observed exhaust profiles translate into specific impulses up to 2400 sec and corresponding thrust efficiencies above 30%.

MHD Energy Bypass Scramjet Performance with Real Gas Effects

NASA Technical Reports Server (NTRS)

Park, Chul; Mehta, Unmeel B.; Bogdanoff, David W.

2000-01-01

The theoretical performance of a scramjet propulsion system incorporating an magneto-hydro-dynamic (MHD) energy bypass scheme is calculated. The one-dimensional analysis developed earlier, in which the theoretical performance is calculated neglecting skin friction and using a sudden-freezing approximation for the nozzle flow, is modified to incorporate the method of Van Driest for turbulent skin friction and a finite-rate chemistry calculation in the nozzle. Unlike in the earlier design, in which four ramp compressions occurred in the pitch plane, in the present design the first two ramp compressions occur in the pitch plane and the next two compressions occur in the yaw plane. The results for the simplified design of a spaceliner show that (1) the present design produces higher specific impulses than the earlier design, (2) skin friction substantially reduces thrust and specific impulse, and (3) the specific impulse of the MHD-bypass system is still better than the non-MHD system and typical rocket over a narrow region of flight speeds and design parameters. Results suggest that the energy management with MHD principles offers the possibility of improving the performance of the scramjet. The technical issues needing further studies are identified.

Investigation of very high energy rockets for future SSTO vehicles

NASA Astrophysics Data System (ADS)

Froning, H. D., Jr.

1989-04-01

Several new propulsion possibilities are being explored in the U.S.A. which might significantly increase the amount of payload that can be propelled into orbit for a given launch vehicle weight. As such, they might enable significant reduction in the future cost of transportation between earth and space. One possibility is the combustion of matter that is in an excited atomic or molecular state. Another possibility is the annihilation of matter by means of anti-matter (by matter with identical mass and opposite electrical charge). And if an appreciable fraction of the energies released by either of these processes could be converted into the useful kinetic energy of a rocket's exhaust, a 2-6-fold increase in its specific impulse might be achieved. This paper shows that a 2-6-fold increase in rocket specific impulse might enable a 4-12-fold reduction in aerospace vehicle weight. It also shows that the specific impulse potential of excited matter or anti-matter fuels might enable transport of heavy payloads into earth orbit by means of single-stage-to-orbit vehicles that would be no heavier than current commercial airline jets.

Granger causality--statistical analysis under a configural perspective.

PubMed

von Eye, Alexander; Wiedermann, Wolfgang; Mun, Eun-Young

2014-03-01

The concept of Granger causality can be used to examine putative causal relations between two series of scores. Based on regression models, it is asked whether one series can be considered the cause for the second series. In this article, we propose extending the pool of methods available for testing hypotheses that are compatible with Granger causation by adopting a configural perspective. This perspective allows researchers to assume that effects exist for specific categories only or for specific sectors of the data space, but not for other categories or sectors. Configural Frequency Analysis (CFA) is proposed as the method of analysis from a configural perspective. CFA base models are derived for the exploratory analysis of Granger causation. These models are specified so that they parallel the regression models used for variable-oriented analysis of hypotheses of Granger causation. An example from the development of aggression in adolescence is used. The example shows that only one pattern of change in aggressive impulses over time Granger-causes change in physical aggression against peers.

The interactions of normal and hyperactive children with their mothers in free play and structured tasks.

PubMed

Cunningham, C E; Barkley, R A

1979-03-01

Groups of 20 normal and 20 hyperactive boys ranging in age from 6 to 12 years were observed interacting with their mothers in 15-min free-play and 15-min structured-task situations. Using a 15-sec interval coding procedure, 1 observer recorded the mother's response to specific antecedent behaviors of the child while a second observer recorded the child's response to specific behaviors of the mother. Hyperactive boys proved more active, less compliant, and less likely to remain on task than nonhyperactive peers. Mothers of hyperactive boys were less likely to respond positively to the child's social interactions, solitary play activities, or compliant on-task behavior. In addition, mothers of hyperactive boys imposed more structure and control on the child's play, social interactions, and task-oriented activities. It is suggested that the controlling intrusive style observed among the mothers of hyperactive boys, while initially a response to the child's overactive, impulsive, inattentive style, may further contribute to the child's behavioral difficulties.

A model-based analysis of impulsivity using a slot-machine gambling paradigm

PubMed Central

Paliwal, Saee; Petzschner, Frederike H.; Schmitz, Anna Katharina; Tittgemeyer, Marc; Stephan, Klaas E.

2014-01-01

Impulsivity plays a key role in decision-making under uncertainty. It is a significant contributor to problem and pathological gambling (PG). 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 (BIs), machines switches (MS), casino switches (CS), and double-ups (DUs). 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 (RL) 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 the impulsive traits of an individual. 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 PG. PMID:25071497

ADHD symptoms in non-treatment seeking young adults: relationship with other forms of impulsivity.

PubMed

Chamberlain, Samuel R; Ioannidis, Konstantinos; Leppink, Eric W; Niaz, Faiza; Redden, Sarah A; Grant, Jon E

2017-02-01

Attention-deficit hyperactivity disorder (ADHD) has been associated with various manifestations of impulsivity in adults, including elevated rates of other impulsive disorders, substance use, questionnaire-based impulsivity scores, and inhibitory dysregulation on neurocognitive tests. The relationship between ADHD and all these other forms of impulsivity has yet to be explored within the context of a single comprehensive study. A total of 423 young adults, who gambled ≥5 times in the preceding year, were recruited using media advertisements and undertook detailed assessment including structured psychiatric interview, questionnaires, and neurocognitive tests. Participants with ADHD symptoms were identified using the Adult ADHD Self-Report Scale Screener (ASRS-V1.1) and were compared to controls using multivariate analysis of variance (MANOVA). ADHD symptoms were found in 20.3% of the sample, but only 7.3% of these subjects had ever received a formal diagnosis. ADHD symptoms were associated with significantly lower quality of life, lower self-esteem, higher emotional dysregulation, higher impulsivity questionnaire scores, more problematic Internet use, greater occurrence of psychiatric disorders, and impaired stop-signal reaction times. Of these variables, stop-signal reaction times and Barratt attentional impulsiveness were the strongest predictors of group classification. ADHD symptoms are common and under-diagnosed in young adults who gamble, and are most strongly linked with certain other types of impulsivity (questionnaire- and cognitive-based measures) and with emotional dysregulation, suggesting that these are each important considerations in understanding the pathophysiology of the disorder, but also potential treatment targets. It is necessary to question whether treatment for adult ADHD could be enhanced by considering self-esteem, emotional reactivity, and impaired inhibitory control as specific treatment targets, in addition to the core diagnostic symptoms of the disorder.

Risk Propensity, Risk Perception, and Sensation Seeking in US Army Soldiers: A Preliminary Study of a Risk Assessment Task Battery

DTIC Science & Technology

2010-10-01

Specifically, if deployment is retrospectively perceived as very risky or dangerous , then the perceived risk of negative consequences of risky behaviors...preference for various types of risky activities. There are five sub-scales of the EVAR; self-control, danger seeking, energy, impulsiveness, and...the total and five sub-scale (self-control, danger seeking, energy, impulsiveness, and invincibility) scores were calculated. A repeated measures

Thermodynamic Cycle and CFD Analyses for Hydrogen Fueled Air-breathing Pulse Detonation Engines

NASA Technical Reports Server (NTRS)

Povinelli, Louis A.; Yungster, Shaye

2002-01-01

This paper presents the results of a thermodynamic cycle analysis of a pulse detonation engine (PDE) using a hydrogen-air mixture at static conditions. The cycle performance results, namely the specific thrust, fuel consumption and impulse are compared to a single cycle CFD analysis for a detonation tube which considers finite rate chemistry. The differences in the impulse values were indicative of the additional performance potential attainable in a PDE.

Classificaiton and Discrimination of Sources with Time-Varying Frequency and Spatial Spectra

DTIC Science & Technology

2007-04-01

sensitivity enhancement by impulse noise excision," in Proc. IEEE Nat. Radar Conf., pp. 252-256, 1997. [7] M. Turley, " Impulse noise rejection in HF...specific time-frequency points or regions, where one or more signals reside, enhances signal-to- noise ratio (SNR) and allows source discrimination and...source separation. The proposed algorithm is developed assuming deterministic signals with additive white complex Gaussian noise . 6. Estimation of FM

Negative urgency partially accounts for the relationship between major depressive disorder and marijuana problems.

PubMed

Gunn, Rachel L; Jackson, Kristina M; Borsari, Brian; Metrik, Jane

2018-01-01

To goal of this study was to better understand mechanisms underlying associations between Major Depressive Disorder (MDD) and marijuana use and problems. Specifically, it was hypothesized that negative urgency (NU), the tendency to act rashly while experiencing negative mood states, would uniquely (compared to other impulsivity traits: positive urgency, sensation seeking, premeditation, and perseverance) account for the relationship between MDD and marijuana use and problems. Data were collected from a sample ( N  = 357) of veterans ( M age = 33.63) recruited from a Veterans Affairs hospital who used marijuana at least once in their lifetime. Participants completed the SCID-NP to assess MDD, a marijuana problems scale, a Time-Line Follow-back to assess six-month marijuana use, and the UPPS-P Impulsive Behavior Scale for impulsivity. Path analysis was conducted using bootstrapped ( k  = 20,000) and bias-corrected 95% confidence intervals (CIs) to estimate mediation (indirect) effects, controlling for age, sex, and race. Analyses revealed a significant direct effect of MDD on NU and NU on marijuana problems. Regarding mediational analyses, there was a significant indirect effect of MDD on marijuana problems via NU. The direct effect of MDD on marijuana problems was reduced, but remained significant, suggesting partial mediation. No other impulsivity scales accounted for the relationship between MDD and marijuana problems. In predicting marijuana use, there were no significant indirect effects for any impulsivity traits, including NU, despite significant bivariate associations between use and NU and MDD. Results suggest that high levels of NU may partially explain associations between MDD and marijuana problems, but not marijuana use. No other facets of impulsivity accounted for the relationship between MDD and marijuana use or problems, underscoring the specificity of NU as a putative mechanism and the importance of assessing NU in treatment settings.

Ion Beam Deflection (AKA Push-Me/Pull-You)

NASA Technical Reports Server (NTRS)

Brophy, John

2013-01-01

The Ion Beam Deflection provides the following potential advantages over other asteroid deflection systems. Like the gravity tractor, it doesn't require despinning of the asteroid. Unlike the gravity tractor, it provides a significantly higher coupling force that is independent of the asteroid size. The concept could be tested as part of the baseline Asteroid Redirect Robotic Mission. The thrust and total impulse are entirely within the design of the SEP vehicle. The total impulse is potentially competitive with kinetic impactors and eliminates the need for a second rendezvous spacecraft.?Gridded ion thrusters provide beam divergence angles of a few degrees enabling long stand-off distances from the asteroid. Mitigating control issues. Minimizing back-sputter contamination risks

Macro-motion detection using ultra-wideband impulse radar.

PubMed

Xin Li; Dengyu Qiao; Ye Li

2014-01-01

Radar has the advantage of being able to detect hidden individuals, which can be used in homeland security, disaster rescue, and healthcare monitoring-related applications. Human macro-motion detection using ultra-wideband impulse radar is studied in this paper. First, a frequency domain analysis is carried out to show that the macro-motion yields a bandpass signal in slow-time. Second, the FTFW (fast-time frequency windowing), which has the advantage of avoiding the measuring range reduction, and the HLF (high-pass linear-phase filter), which can preserve the motion signal effectively, are proposed to preprocess the radar echo. Last, a threshold decision method, based on the energy detector structure, is presented.

Women with borderline personality disorder do not show altered BOLD responses during response inhibition.

PubMed

van Eijk, Julia; Sebastian, Alexandra; Krause-Utz, Annegret; Cackowski, Sylvia; Demirakca, Traute; Biedermann, Sarah V; Lieb, Klaus; Bohus, Martin; Schmahl, Christian; Ende, Gabriele; Tüscher, Oliver

2015-12-30

Impulsivity is central to borderline personality disorder (BPD). Response inhibition, addressing the ability to suppress or stop actions, is one aspect of behavioral impulse control which is frequently used to assess impulsivity. BPD patients display deficits in response inhibition under stress condition or negative emotions. We assessed whether response inhibition and its neural underpinnings are impaired in BPD when tested in an emotionally neutral setting and when co-morbid attention-deficit/hyperactivity disorder (ADHD) is excluded. To this end, we studied response inhibition in unmedicated BPD patients and healthy controls (HC) in two independent samples using functional magnetic resonance imaging during Simon-, Go/nogo-, and Stopsignal tasks. BPD patients and HC did not differ significantly in their performance in the Go/nogo and the Stopsignal tasks. Response interference in the Simon task was increased in BPD patients in one sample, but this could not be replicated in the second sample. In both samples, no significant differences in brain activation patterns during any of the tasks were present while the neural impulse control network was robustly activated during the inhibition tasks in both groups. Our results provide evidence that under emotionally neutral conditions response inhibition is not impaired in patients with BPD without co-occurring ADHD. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

The role of depression and impulsivity in the psychopathology of bulimia nervosa.

PubMed

Vaz-Leal, Francisco J; Rodríguez-Santos, Laura; García-Herráiz, M Angustias; Chimpén-López, Carlos A; Rojo-Moreno, Luís; Beato-Fernández, Luís; Ramos-Fuentes, María Isabel

2014-01-01

The study aimed to analyze the role of depression and impulsivity in the psychopathology of bulimia nervosa (BN). Seventy female patients with DSM-IV BN, purging subtype, were assessed for eating-related symptoms, body dissatisfaction, affective symptoms, impulsivity, and personality traits. Factor analysis and structural equation modeling methods were used for statistical analysis. BN appeared as a condition which incorporated 5 general dimensions: a) binge eating and compensatory behaviours; b) restrictive eating; c) body dissatisfaction; d) dissocial personality traits; and e) a cluster of features which was called «emotional instability» The 5 obtained dimensions can be grouped into 2 basic factors: body dissatisfaction/eating behaviour and personality traits/psychopathology. The first one contains the clinical items used for the definition of BN as a clinical condition in the DSM-V and the International Classification of Diseases 10, and reflects the morphology and the severity of the eating-related symptoms. The second dimension includes a cluster of symptoms (depressive symptoms, impulsivity, and borderline, self-defeating and dissocial personality traits) which could be regarded as the «psychopathological core» of BN and may be able to condition the course and the prognosis of BN. Copyright © 2013 SEP y SEPB. Published by Elsevier España. All rights reserved.

Are juvenile domestic pigs (Sus scrofa domestica) sensitive to the attentive states of humans?--The impact of impulsivity on choice behaviour.

PubMed

Nawroth, Christian; Ebersbach, Mirjam; von Borell, Eberhard

2013-06-01

Previous studies have shown that apes, dogs and horses seem to be able to attribute attentive states to humans. Subjects had to choose between two persons: one who was able to see the animal and one who was not. Using a similar paradigm, we tested a species that does not rely strongly on visual cues, the domestic pig (Sus scrofa domestica). Subjects could choose between two unfamiliar persons, with only one showing attention, in three different conditions (body, head away, body turned - head front). Subjects (n=16) only showed a tendency towards the attentive human in the head away condition. However, by pooling those two conditions where the position of the human head was the only salient cue, we found a significant preference for the attentive person. Moreover, two approach styles could be distinguished - an impulsive style with short response times and a non-impulsive style where response times were relatively long. With the second approach style, pigs chose the attentive person significantly more often than expected by chance level, which was not the case when subjects chose impulsively. These first results suggest that pigs are able to use head cues to discriminate between different attentive states of humans. Copyright © 2013 Elsevier B.V. All rights reserved.

Impulsivity in men with prescription of benzodiazepines and methadone in prison.

PubMed

Moreno-Ramos, Luis; Fernández-Serrano, María José; Pérez-García, Miguel; Verdejo-García, Antonio

2016-06-14

Benzodiazepines and methadone use has been associated with various neuropsychological impairments. However, to the best of our knowledge, no studies have been carried out on the effect of these substances (either separately or combined) on impulsive personality, including studies in prisoners. The aim of this study is to examine the impulsive personality of a sample of 134 male prisoners using the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (Torrubia, Avila, Molto, & Caseras, 2001) and the UPPS-P Scale (Cyders et al., 2007). Some of these were methadone users, methadone and benzodiazepines users, polydrug users in abstinence and non-dependent drug users. The results showed that drug users have greater sensitivity to reward, positive urgency, negative urgency and sensation seeking than non-dependent users. Methadone users showed more sensitivity to punishment and lack of perseverance with respect to other users. No differences were found between methadone+benzodiazepines users and other groups. The secondary aim is to examine which impulsive personality dimensions are related to the two motivational systems proposed by Gray (BIS-BAS) using exploratory factor analysis. Results showed two different components. One component was defined by the subscales sensitivity to reinforcement, positive urgency, negative urgency and sensation seeking. The second component was defined by the subscales sensitivity to punishment, lack of perseverance and lack of premeditation.

Genetic support for the dual nature of attention deficit hyperactivity disorder: substantial genetic overlap between the inattentive and hyperactive-impulsive components.

PubMed

McLoughlin, Gráinne; Ronald, Angelica; Kuntsi, Jonna; Asherson, Philip; Plomin, Robert

2007-12-01

Attention deficit hyperactivity disorder (ADHD) is a common, complex and highly heritable disorder, characterised by inattentive, impulsive and overactive behaviour. Evidence for the heritability of ADHD measures in twin population samples has come from the analysis of total scores that combine inattentive and hyperactive-impulsive symptoms subscales. This study investigated, in a community sample, the aetiology of ADHD-like traits and the aetiological overlap between the two dimensions that define the ADHD disorder. Parents of 6,222 approximately 8-year-old twin pairs from the Twins Early Development Study (TEDS) population sample completed the two subscales of the Conners' 18-item DSMIV checklist, a screening instrument for ADHD symptoms. Both subscales were highly heritable (hyperactive-impulsive: 88%; inattentive: 79%). Bivariate genetic modelling indicated substantial genetic overlap between the two components; however, there were significant independent genetic effects. These findings suggest that many genes associated with the hyperactivity-impulsivity dimension will also be associated with the inattentive dimension but that there is significant genetic heterogeneity as well. These results provide genetic support for combining the two behavioural dimensions that define ADHD, but also suggest that some symptom-specific genes will also be identified.

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

PubMed

Mantzios, Michail; Giannou, Kyriaki

2014-07-01

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. © 2014 The International Association of Applied Psychology.

Interactions between risky decisions, impulsiveness and smoking in young tattooed women

PubMed Central

2013-01-01

Background According to previous studies, one of the common problems of everyday life of persons with tattoos is risky behavior. However, direct examination of the decision making process, as well as factors which determine women’s risk-taking decisions to get tattoos, have not been conducted. This study investigates whether risk taking decision-making is associated with the self-assessment impulsiveness in tattooed women. Methods Young women (aged 18–35 years) with (N = 60) and without (N = 60) tattoos, performed the Iowa Gambling Task (IGT), as a measure of decision-making processes, as well as completing the Barratt Impulsivity Scale (BIS-11). Results Tattooed women showed significantly higher scores in the BIS-11 and preference for disadvantageous decks on the IGT compared to non-tattooed women. There was no significant correlation between risky decision-making in the IGT and BIS-11 impulsivity measures. A significantly higher rate of smoking was observed in the tattooed women. However, the analysis did not reveal a group effect after adjustment for smoking in the IGT and the BIS-11 measures. Conclusions The present study was specifically designed to resolve questions regarding associations between impulsiveness and risky decision-making in tattooed women. It shows that in tattooed women, risky decisions are not a direct result of their self-reported impulsiveness. Smoking does not explain the psychometric differences between tattooed women and controls. PMID:24180254

Sex differences in impulsivity: a meta-analysis.

PubMed

Cross, Catharine P; Copping, Lee T; Campbell, Anne

2011-01-01

Men are overrepresented in socially problematic behaviors, such as aggression and criminal behavior, which have been linked to impulsivity. Our review of impulsivity is organized around the tripartite theoretical distinction between reward hypersensitivity, punishment hyposensitivity, and inadequate effortful control. Drawing on evolutionary, criminological, developmental, and personality theories, we predicted that sex differences would be most pronounced in risky activities with men demonstrating greater sensation seeking, greater reward sensitivity, and lower punishment sensitivity. We predicted a small female advantage in effortful control. We analyzed 741 effect sizes from 277 studies, including psychometric and behavioral measures. Women were consistently more punishment sensitive (d = -0.33), but men did not show greater reward sensitivity (d = 0.01). Men showed significantly higher sensation seeking on questionnaire measures (d = 0.41) and on a behavioral risk-taking task (d = 0.36). Questionnaire measures of deficits in effortful control showed a very modest effect size in the male direction (d = 0.08). Sex differences were not found on delay discounting or executive function tasks. The results indicate a stronger sex difference in motivational rather than effortful or executive forms of behavior control. Specifically, they support evolutionary and biological theories of risk taking predicated on sex differences in punishment sensitivity. A clearer understanding of sex differences in impulsivity depends upon recognizing important distinctions between sensation seeking and impulsivity, between executive and effortful forms of control, and between impulsivity as a deficit and as a trait.

CSF and plasma testosterone in attempted suicide.

PubMed

Stefansson, Jon; Chatzittofis, Andreas; Nordström, Peter; Arver, Stefan; Åsberg, Marie; Jokinen, Jussi

2016-12-01

Very few studies have assessed testosterone levels in the cerebrospinal fluid in suicide attempters. Aggressiveness and impulsivity are common behavioural traits in suicide attempters. Dual-hormone serotonergic theory on human impulsive aggression implies high testosterone/cortisol ratio acting on the amygdala and low serotonin in the prefrontal cortex. Our aim was to examine the CSF and plasma testosterone levels in suicide attempters and in healthy volunteers. We also assessed the relationship between the testosterone/cortisol ratio, aggressiveness and impulsivity in suicide attempters. 28 medication-free suicide attempters and 19 healthy volunteers participated in the study. CSF and plasma testosterone sulfate and cortisol levels were assessed with specific radio-immunoassays. The Karolinska Scales of Personality was used to assess impulsivity and aggressiveness. All patients were followed up for cause of death. The mean follow-up period was 21 years. Male suicide attempters had higher CSF and plasma testosterone levels than age- matched male healthy volunteers. There were no significant differences in CSF testosterone levels in female suicide attempters and healthy female volunteers. Testosterone levels did not differ significantly in suicide victims compared to survivors. In male suicide attempters, the CSF testosterone/cortisol ratio showed a significant positive correlation with both impulsivity and aggressiveness. Higher CSF testosterone levels may be associated with attempted suicide in young men through association with both aggressiveness and impulsivity, a key endophenotype in young male suicide attempters. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impulsivity, aggression and brain structure in high and low lethality suicide attempters with borderline personality disorder.

PubMed

Soloff, Paul; White, Richard; Diwadkar, Vaibhav A

2014-06-30

Impulsivity and aggressiveness are trait dispositions associated with the vulnerability to suicidal behavior across diagnoses. They are associated with structural and functional abnormalities in brain networks involved in regulation of mood, impulse and behavior. They are also core characteristics of borderline personality disorder (BPD), a disorder defined, in part, by recurrent suicidal behavior. We assessed the relationships between personality traits, brain structure and lethality of suicide attempts in 51 BPD attempters using multiple regression analyses on structural MRI data. BPD was diagnosed by the Diagnostic Interview for Borderline Patients-revised, impulsivity by the Barratt Impulsiveness Scale (BIS), aggression by the Brown-Goodwin Lifetime History of Aggression (LHA), and high lethality by a score of 4 or more on the Lethality Rating Scale (LRS). Sixteen High Lethality attempters were compared to 35 Low Lethality attempters, with no significant differences noted in gender, co-morbidity, childhood abuse, BIS or LHA scores. Degree of medical lethality (LRS) was negatively related to gray matter volumes across multiple fronto-temporal-limbic regions. Effects of impulsivity and aggression on gray matter volumes discriminated High from Low Lethality attempters and differed markedly within lethality groups. Lethality of suicide attempts in BPD may be related to the mediation of these personality traits by specific neural networks. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Pathways to Peace: Promoting Non-Violent Learning Environments.

ERIC Educational Resources Information Center

Johnson, Celia E.; Templeton, Rosalyn Anstine; Wan, Guofang

This qualitative study explored the effects of the Second Step Curriculum, designed to teach the social skills necessary for children to peacefully solve problems and resolve conflicts through empathy training, impulse control, and anger management. The study focused on teachers' perceptions of the program: what they perceived to be the program…

Impulse control disorders and related behaviours (ICD-RBs) in Parkinson's disease patients: Assessment using “Questionnaire for impulsive-compulsive disorders in Parkinson's disease” (QUIP)

PubMed Central

Sharma, Ashish; Goyal, Vinay; Behari, Madhuri; Srivastva, Achal; Shukla, Garima; Vibha, Deepti

2015-01-01

Background: There is limited data on the prevalence of impulse control disorder and related behaviors (ICD-RBs) in Indian patients with Parkinson's Disease (PD). In the context of potential genetic and environmental factors affecting the expression of ICD-RBs, studying other multiethnic populations may bring in-sights into the mechanisms of these disorders. Objectives: To ascertain point prevalence estimate of ICD-RBs in Indian PD patients, using the validated “Questionnaire for Impulsive-Compulsive Disorders in Parkinson's disease (QUIP)” and to examine their association with Dopamine replacement therapy (DRT). Materials and Methods: This was a hospital based observational cross-sectional study. After taking informed consent, patients and their informants (spouse, or primary caregiver) were made to complete the QUIP, and were instructed to answer questions based on behaviors that occurred anytime during PD that lasted at least four consecutive weeks. Results: Total of 299 patients participated in the study. At least one ICD-RB was present in 128 (42.8%), at least one Impulse control disorder (ICD) was present in 74 (24.75%) and at least one Impulse control related compulsive behaviour (ICRB) was present in 93 (31.1%) patients. Punding was the most frequent (12.4%) followed by hyper sexuality (11.04%), compulsive hobbyism (9.4%), compulsive shopping (8.4%), compulsive medication use (7.7%), compulsive eating (5.35%), walkabout (4%) and pathological gambling (3.3%). ≥ 2 ICD-RBs were observed in 15.7% of patients. After multivariate analysis, younger age of onset, being unmarried were specifically associated with presence of ICD. Longer disease duration was specifically associated with presence of ICRB. Whereas smoking and higher dopamine levodopa equivalent daily doses (DA LEDD) were associated with both presence of ICD and ICRB. Higher LD LEDD was specifically associated with presence of ICD-RB. Conclusions: Our study revealed a relatively higher frequency of ICD-RBs, probably because of the use of screening instrument and because we combined both ICDs and ICRBs. Also high proportion of DA use (81.6%) among our patients might be responsible. The role of genetic factors that might increase the risk of developing ICD-RBs in this population needs further exploration. PMID:25745311

The relationship between impulse control disorders and obsessive-compulsive disorder: a current understanding and future research directions

PubMed Central

Potenza, Marc Nicholas; Koran, Lorrin Michael; Pallanti, Stefano

2009-01-01

Impulse control disorders (ICDs) constitute a heterogeneous group of conditions linked diagnostically by difficulties in resisting “the impulse, drive, or temptation to perform an act that is harmful to the person or to others.” Specific ICDs share clinical, phenomenological and biological features with obsessive-compulsive disorder (OCD) that have suggested that these disorders might be categorized together. However, other data suggest significant differences between OCD and ICDs. In this article, clinical, phenomenological and biological features of the formal ICDs are reviewed and compared and contrasted with those of OCD. Available data indicate substantial differences between ICDs and OCD that suggest independent categorizations. Existing research gaps are identified and avenues for future research suggested. PMID:19811840

Affective traits of psychopathy are linked to white-matter abnormalities in impulsive male offenders.

PubMed

Vermeij, Anouk; Kempes, Maaike M; Cima, Maaike J; Mars, Rogier B; Brazil, Inti A

2018-04-26

Psychopathy is a personality disorder typified by lack of empathy and impulsive antisocial behavior. Psychopathic traits may partly relate to disrupted connections between brain regions. The aim of the present study was to link abnormalities in microstructural integrity of white-matter tracts to the severity of different psychopathic traits in 15 male offenders with impulse control problems and 10 without impulse control problems. Psychopathic traits were assessed using the Psychopathy Checklist-revised (PCL-R). Diffusion-weighted MRI was used to examine white-matter tracts. Fractional anisotropy (FA), an index of white-matter integrity, was calculated for each voxel. Clusters of voxels showing a significant relationship with psychopathy severity were submitted to probabilistic tractography. No significant correlations between psychopathy severity and FA were present in the whole group of impulsive and nonimpulsive offenders. In impulsive offenders, interpersonal-affective traits (PCL-R Factor 1) were negatively correlated with FA in the anterior and posterior temporal lobe and orbitofrontal area. Further analyses indicated that elevated affective traits (PCL-R Facet 2) were specifically related to reduced FA in the right temporal lobe. Our findings suggest that white-matter abnormalities in temporal and frontotemporal tracts may be linked to the interpersonal-affective deficits of psychopathy in offenders with relatively severe impulse control problems. Our study offers novel insights into the relationships between the four facets of psychopathy and disrupted structural connectivity, and may provide new leads for further characterization of different subtypes of antisocial populations. (PsycINFO Database Record (c) 2018 APA, all rights reserved).