[Experimental study of the effects of impulse-electric discharge on chemotaxis and cytoadhesion of urinary infection pathogens].

PubMed

Kuderinov, S K; Azizov, I S; Turgunov, E M; Shambilova, N A

2006-01-01

The aim of the experimental study was to evaluate effects of impulse-electric discharge in liquid on chemotaxis and cytoadhesion of urinary infection pathogens. Chemotaxis was determined in respect to the lung, liver, spleen, kidney, ureter, urinary bladder, urethra of white mice by S. Likholetov's modified method. Cytoadhesion was assessed by V. Brilis. The experiments show that the impulse-electric discharge holds promise for urological practice.

Synthesis of Natural Electric and Magnetic Time Series Using Impulse Responses of Inter-station Transfer Functions and a Reference

NASA Astrophysics Data System (ADS)

Wang, H.; Cheng, J.

2017-12-01

A method to Synthesis natural electric and magnetic Time series is proposed whereby the time series of local site are derived using an Impulse Response and a reference (STIR). The method is based on the assumption that the external source of magnetic fields are uniform, and the electric and magnetic fields acquired at the surface satisfy a time-independent linear relation in frequency domain.According to the convolution theorem, we can synthesize natural electric and magnetic time series using the impulse responses of inter-station transfer functions with a reference. Applying this method, two impulse responses need to be estimated: the quasi-MT impulse response tensor and the horizontal magnetic impulse response tensor. These impulse response tensors relate the local horizontal electric and magnetic components with the horizontal magnetic components at a reference site, respectively. Some clean segments of times series are selected to estimate impulse responses by using least-square (LS) method. STIR is similar with STIN (Wang, 2017), but STIR does not need to estimate the inter-station transfer functions, and the synthesized data are more accurate in high frequency, where STIN fails when the inter-station transfer functions are contaminated severely. A test with good quality of MT data shows that synthetic time-series are similar to natural electric and magnetic time series. For contaminated AMT example, when this method is used to remove noise present at the local site, the scatter of MT sounding curves are clear reduced, and the data quality are improved. *This work is funded by National Key R&D Program of China(2017YFC0804105),National Natural Science Foundation of China (41604064, 51574250), State Key Laboratory of Coal Resources and Safe Mining ,China University of Mining & Technology,(SKLCRSM16DC09)

Overview on NASA's Advanced Electric Propulsion Concepts Activities

NASA Technical Reports Server (NTRS)

Frisbee, Robert H.

1999-01-01

Advanced electric propulsion research activities are currently underway that seek to addresses feasibility issues of a wide range of advanced concepts, and may result in the development of technologies that will enable exciting new missions within our solar system and beyond. Each research activity is described in terms of the present focus and potential future applications. Topics include micro-electric thrusters, electrodynamic tethers, high power plasma thrusters and related applications in materials processing, variable specific impulse plasma thrusters, pulsed inductive thrusters, computational techniques for thruster modeling, and advanced electric propulsion missions and systems studies.

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.

[Correlative interconnections between impulse activity of aminergic neurons of the brainstem and spectral components of electroencephalogram during action of bemitil].

PubMed

Kolotilova, O I; Pavlenko, V B; Koreniuk, I I; Kulychenko, O M; Fokina, Iu O

2007-01-01

Correlative interconnections between frequency of impulse activity of aminergic neurons and neocortex electrical activity during action of bemitil (50 mg/kg) were investigated in 5 cats. It was shown that bemitil affects correlations between frequency of impulses of aminergic neurons and electrical activity of neocortex.

Ion propulsion

NASA Technical Reports Server (NTRS)

Meserole, J. S.; Keefer, Dennis; Ruyten, Wilhelmus; Peng, Xiaohang

1995-01-01

An ion engine is a plasma thruster which produces thrust by extracting ions from the plasma and accelerating them to high velocity with an electrostatic field. The ions are then neutralized and leave the engine as high velocity neutral particles. The advantages of ion engines are high specific impulse and efficiency and their ability to operate over a wide range of input powers. In comparison with other electric thrusters, the ion engine has higher efficiency and specific impulse than thermal electric devices such as the arcjet, microwave, radiofrequency and laser heated thrusters and can operate at much lower current levels than the MPD thruster. However, the thrust level for an ion engine may be lower than a thermal electric thruster of the same operating power, consistent with its higher specific impulse, and therefore ion engines are best suited for missions which can tolerate longer duration propulsive phases. The critical issue for the ion engine is lifetime, since the prospective missions may require operation for several thousands of hours. The critical components of the ion engine, with respect to engine lifetime, are the screen and accelerating grid structures. Typically, these are large metal screens that must support a large voltage difference and maintain a small gap between them. Metallic whisker growth, distortion and vibration can lead to arcing, and over a long period of time ion sputtering will erode the grid structures and change their geometry. In order to study the effects of long time operation of the grid structure, we are developing computer codes based on the Particle-In-Cell (PIC) technique and Laser Induced Fluorescence (LIF) diagnostic techniques to study the physical processes which control the performance and lifetime of the grid structures.

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.

End-hall thrusters

NASA Technical Reports Server (NTRS)

Kaufman, H. R.; Robinson, R. S.; Day, M. L.; Haag, T. W.

1990-01-01

The end-Hall thruster can provide electric propulsion with fixed masses, specific impulses, and power-to-thrust ratios intermediate of an arcjet and a gridded (electrostatic) ion thruster. With these characteristics, this thruster is a candidate for missions of intermediate difficulty, such as the north-south stationkeeping of geostationary satellites.

Mission and system optimization of nuclear electric propulsion vehicles for lunar and Mars missions

NASA Technical Reports Server (NTRS)

Gilland, James H.

1991-01-01

The detailed mission and system optimization of low thrust electric propulsion missions is a complex, iterative process involving interaction between orbital mechanics and system performance. Through the use of appropriate approximations, initial system optimization and analysis can be performed for a range of missions. The intent of these calculations is to provide system and mission designers with simple methods to assess system design without requiring access or detailed knowledge of numerical calculus of variations optimizations codes and methods. Approximations for the mission/system optimization of Earth orbital transfer and Mars mission have been derived. Analyses include the variation of thruster efficiency with specific impulse. Optimum specific impulse, payload fraction, and power/payload ratios are calculated. The accuracy of these methods is tested and found to be reasonable for initial scoping studies. Results of optimization for Space Exploration Initiative lunar cargo and Mars missions are presented for a range of power system and thruster options.

An Overview of the Nuclear Electric Xenon Ion System (NEXIS) Activity

NASA Technical Reports Server (NTRS)

Randolph, Thomas M.; Polk, James E., Jr.

2004-01-01

The Nuclear Electric Xenon Ion System (NEXIS) research and development activity within NASA's Project Prometheus, was one of three proposals selected by NASA to develop thruster technologies for long life, high power, high specific impulse nuclear electric propulsion systems that would enable more robust and ambitious science exploration missions to the outer solar system. NEXIS technology represents a dramatic improvement in the state-of-the-art for ion propulsion and is designed to achieve propellant throughput capabilities >= 2000 kg and efficiencies >= 78% while increasing the thruster power to >= 20 kW and specific impulse to >= 6000 s. The NEXIS technology uses erosion resistant carbon-carbon grids, a graphite keeper, a new reservoir hollow cathode, a 65-cm diameter chamber masked to produce a 57-cm diameter ion beam, and a shared neutralizer architecture to achieve these goals. The accomplishments of the NEXIS activity so far include performance testing of a laboratory model thruster, successful completion of a proof of concept reservoir cathode 2000 hour wear test, structural and thermal analysis of a completed development model thruster design, fabrication of most of the development model piece parts, and the nearly complete vacuum facility modifications to allow long duration wear testing of high power ion thrusters.

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.;

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.

Electric Propulsion Technology Development for the Jupiter Icy Moons Orbiter Project

NASA Technical Reports Server (NTRS)

2004-01-01

During 2004, the Jupiter Icy Moons Orbiter project, a part of NASA's Project Prometheus, continued efforts to develop electric propulsion technologies. These technologies addressed the challenges of propelling a spacecraft to several moons of Jupiter. Specific challenges include high power, high specific impulse, long lived ion thrusters, high power/high voltage power processors, accurate feed systems, and large propellant storage systems. Critical component work included high voltage insulators and isolators as well as ensuring that the thruster materials and components could operate in the substantial Jupiter radiation environment. A review of these developments along with future plans is discussed.

Electric propulsion technology

NASA Technical Reports Server (NTRS)

Finke, R. C.

1980-01-01

The advanced electric propulsion program is directed towards lowering the specific impulse and increasing the thrust per unit of ion thruster systems. In addition, electrothermal and electromagnetic propulsion technologies are being developed to attempt to fill the gap between the conventional ion thruster and chemical rocket systems. Most of these new concepts are exagenous and are represented by rail accelerators, ablative Teflon thrusters, MPD arcs, Free Radicals, etc. Endogenous systems such as metallic hydrogen offer great promise and are also being pursued.

High-Power Krypton Hall Thruster Technology Being Developed for Nuclear-Powered Applications

NASA Technical Reports Server (NTRS)

Jacobson, David T.; Manzella, David H.

2004-01-01

The NASA Glenn Research Center has been performing research and development of moderate specific impulse, xenon-fueled, high-power Hall thrusters for potential solar electric propulsion applications. These applications include Mars missions, reusable tugs for low-Earth-orbit to geosynchronous-Earth-orbit transportation, and missions that require transportation to libration points. This research and development effort resulted in the design and fabrication of the NASA-457M Hall thruster that has been tested at input powers up to 95 kW. During project year 2003, NASA established Project Prometheus to develop technology in the areas of nuclear power and propulsion, which are enabling for deep-space science missions. One of the Project-Prometheus-sponsored Nuclear Propulsion Research tasks is to investigate alternate propellants for high-power Hall thruster electric propulsion. The motivation for alternate propellants includes the disadvantageous cost and availability of xenon propellant for extremely large scale, xenon-fueled propulsion systems and the potential system performance benefits of using alternate propellants. The alternate propellant krypton was investigated because of its low cost relative to xenon. Krypton propellant also has potential performance benefits for deep-space missions because the theoretical specific impulse for a given voltage is 20 percent higher than for xenon because of krypton's lower molecular weight. During project year 2003, the performance of the high-power NASA-457M Hall thruster was measured using krypton as the propellant at power levels ranging from 6.4 to 72.5 kW. The thrust produced ranged from 0.3 to 2.5 N at a discharge specific impulse up to 4500 sec.

[Nerve impulse in the 19th century: it's nature and the method of research].

PubMed

Ueda, Risa; Sugiyama, Shigeo

2003-01-01

We demonstrate in this paper how scientists in the 19th century did researches on the nervous system; some scientists tried to make the nature of "nerve impulse" clear only to fail, while others chose to investigate how the nervous system works, leaving the nature of the impulse unknown. A. Mosso and H. D. Rolleston, for example, attempted to detect heat produced in nerves with a view to elucidating the nature of the impulse. The heat, they believed, would suggest that "nerve impulse" was nothing but "a wave of chemical reaction" or "a wave of molecular vibration." On the other hand, C. S. Sherrington who introduced the term synapsis in 1897 to refer to the special connection between nerve cells--special in the sense it offers an opportunity for "nerve impulse" to change in its nature--refrained from examining the nature of the impulse. He believed that it was impossible for science at the time to elucidate the nature. He, therefore, focused his attention to reactions of muscles in an animal caused when various stimulations were applied on animal's skin in a remote area from the muscles. He did not probe into the working of the nerves running between the part where stimulation was given and the part where corresponding reaction occurred. He pursued his studies by using phenomenalistic approach. We call his approach "phenomenalistic" because his research focused only on contradictions of muscles easily seen without probing into minute arrangement in a body. Gotch and Horsley, like Sherrington, did not argue about the nature of "nerve impulse." But unlike Sherrington, they made experiments with electrical changes produced in nerves or a spinal cord, based on the idea that "nerve impulse" should accompany certain electrical changes. Making use of their electrical method effectively, they obtained a series of quantitative data as to the electrical changes. The data they collected allowed them to explore distribution of nerves deep in a body and even led them to contemplate the existence of "field of conjunction" in a spinal cord. They introduced the concept to explain decrease in quantity and delay in transmission time of the electrical change, which was observed when a nerve impulse traversed a certain part of the spinal cord. This idea was considerably similar to "synapse" introduced six years later by Sherrington.

Development of advanced inert-gas ion thrusters

NASA Technical Reports Server (NTRS)

Poeschel, R. L.

1983-01-01

Inert gas ion thruster technology offers the greatest potential for providing high specific impulse, low thrust, electric propulsion on large, Earth orbital spacecraft. The development of a thruster module that can be operated on xenon or argon propellant to produce 0.2 N of thrust at a specific impulse of 3000 sec with xenon propellant and at 6000 sec with argon propellant is described. The 30 cm diameter, laboratory model thruster is considered to be scalable to produce 0.5 N thrust. A high efficiency ring cusp discharge chamber was used to achieve an overall thruster efficiency of 77% with xenon propellant and 66% with argon propellant. Measurements were performed to identify ion production and loss processes and to define critical design criteria (at least on a preliminary basis).

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.

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.

The use of dual mode thermionic reactors in supporting Earth orbital and space exploration missions

NASA Astrophysics Data System (ADS)

Zubrin, Robert M.; Sulmeisters, Tal K.

1993-01-01

Missions requiring large amounts of electric power to support their payload functions can be enabled through the employment of nuclear electric power reactors, which in some cases can also assist the mission by making possible the employment of high specific impulse electric propulsion. However it is found that the practicality and versality of using a power reactor to provide advanced propulsion is enormously enhanced if the reactor is configured in such a way to allow it to generate a certain amount of direct thrust as well. The use of such a system allows the creation of a common bus upper stage that can provide both high power and high impulse (with short orbit transfer times). It is shown that such a system, termed an Integral Power and Propulsion Stage (IPAPS), is optimal for supporting many Earth, Lunar, planetary and asteroidal observation, exploration, and communication support missions, and it is therefore recommended that the nuclear power reactor ultimately selected by the government for development and production be one that can be configured for such a function.

Remote tire pressure sensing technique

NASA Technical Reports Server (NTRS)

Robinson, Howard H. (Inventor); Mcginnis, Timothy A. (Inventor); Daugherty, Robert H. (Inventor)

1993-01-01

A remote tire pressure sensing technique is provided which uses vibration frequency to determine tire pressure. A vibration frequency measuring device is attached to the external surface of a tire which is then struck with an object, causing the tire to vibrate. The frequency measuring device measures the vibrations and converts the vibrations into corresponding electrical impulses. The electrical impulses are then fed into the frequency analyzing system which uses the electrical impulses to determine the relative peaks of the vibration frequencies as detected by the frequency measuring device. The measured vibration frequency peaks are then compared to predetermined data describing the location of vibration frequency peaks for a given pressure, thereby determining the air pressure of the tire.

Electronic (fenceless) control of livestock.

Treesearch

A.R. Tiedemann; T.M. Quigley; L.D. White; et al.

1999-01-01

During June and August 1992, a new technology designed to exclude cattle from specific areas such as riparian zones was tested. The technology consisted of an eartag worn by an animal that provides an audio warning and electrical impulse to the ear as the animal approaches the zone of influence of a transmitter. The transmitter emits a signal that narrowly defines the...

Electrical engram: how deep brain stimulation affects memory.

PubMed

Lee, Hweeling; Fell, Jürgen; Axmacher, Nikolai

2013-11-01

Deep brain stimulation (DBS) is a surgical procedure involving implantation of a pacemaker that sends electric impulses to specific brain regions. DBS has been applied in patients with Parkinson's disease, depression, and obsessive-compulsive disorder (among others), and more recently in patients with Alzheimer's disease to improve memory functions. Current DBS approaches are based on the concept that high-frequency stimulation inhibits or excites specific brain regions. However, because DBS entails the application of repetitive electrical stimuli, it primarily exerts an effect on extracellular field-potential oscillations similar to those recorded with electroencephalography. Here, we suggest a new perspective on how DBS may ameliorate memory dysfunction: it may enhance normal electrophysiological patterns underlying long-term memory processes within the medial temporal lobe. Copyright © 2013 Elsevier Ltd. All rights reserved.

Radioisotope Electric Propulsion (REP): A Near-Term Approach to Nuclear Propulsion

NASA Technical Reports Server (NTRS)

Schmidt, George R.; Manzella, David H.; Kamhawi, Hani; Kremic, Tibor; Oleson, Steven R.; Dankanich, John W.; Dudzinski, Leonard A.

2009-01-01

Studies over the last decade have shown radioisotope-based nuclear electric propulsion to be enhancing and, in some cases, enabling for many potential robotic science missions. Also known as radioisotope electric propulsion (REP), the technology offers the performance advantages of traditional reactor-powered electric propulsion (i.e., high specific impulse propulsion at large distances from the Sun), but with much smaller, affordable spacecraft. Future use of REP requires development of radioisotope power sources with system specific powers well above that of current systems. The US Department of Energy and NASA have developed an advanced Stirling radioisotope generator (ASRG) engineering unit, which was subjected to rigorous flight qualification-level tests in 2008, and began extended lifetime testing later that year. This advancement, along with recent work on small ion thrusters and life extension technology for Hall thrusters, could enable missions using REP sometime during the next decade.

The QED engine spectrum - Fusion-electric propulsion for air-breathing to interstellar flight

NASA Technical Reports Server (NTRS)

Bussard, Robert W.; Jameson, Lorin W.

1993-01-01

A new inertial-electrostatic-fusion direct electric power source can be used to drive a relativistic e-beam to heat propellant. The resulting system is shown to yield specific impulse and thrust/mass ratio 2-3 orders of magnitude larger than from other advanced propulsion concepts. This QED system can be applied to aerospace vehicles from air-breathing to near-interstellar flight. Examples are given for Earth/Mars flight missions, that show transit times of 40 d with 20 percent payload in single-stage vehicles.

Myelin

MedlinePlus

... and fatty substances. This myelin sheath allows electrical impulses to transmit quickly and efficiently along the nerve cells. If myelin is damaged, these impulses slow down. This can cause diseases such as ...

Solar Electric Propulsion for Mars Exploration

NASA Technical Reports Server (NTRS)

Hack, Kurt J.

1998-01-01

Highly propellant-efficient electric propulsion is being combined with advanced solar power technology to provide a non-nuclear transportation option for the human exploration of Mars. By virtue of its high specific impulse, electric propulsion offers a greater change in spacecraft velocity for each pound of propellant than do conventional chemical rockets. As a result, a mission to Mars based on solar electric propulsion (SEP) would require fewer heavy-lift launches than a traditional all-chemical space propulsion scenario would. Performance, as measured by mass to orbit and trip time, would be comparable to the NASA design reference mission for human Mars exploration, which utilizes nuclear thermal propulsion; but it would avoid the issues surrounding the use of nuclear reactors in space.

Magnetospheric electric fields and currents

NASA Technical Reports Server (NTRS)

Mauk, B. H.; Zanetti, L. J.

1987-01-01

The progress made in the years 1983-1986 in understanding the character and operation of magnetospheric electric fields and electric currents is discussed, with emphasis placed on the connection with the interior regions. Special attention is given to determinations of global electric-field configurations, measurements of the response of magnetospheric particle populations to the electric-field configurations, and observations of the magnetospheric currents at high altitude and during northward IMF. Global simulations of current distributions are discussed, and the sources of global electric fields and currents are examined. The topics discussed in the area of impulsive and small-scale phenomena include substorm current systems, impulsive electric fields and associated currents, and field-aligned electrodynamics. A key finding of these studies is that the electric fields and currents are interrelated and cannot be viewed as separate entities.

Treatment of Atrial Fibrillation By The Ablation Of Localized Sources

PubMed Central

Narayan, Sanjiv M.; Krummen, David E.; Shivkumar, Kalyanam; Clopton, Paul; Rappel, Wouter-Jan; Miller, John M.

2012-01-01

Objectives We hypothesized that human atrial fibrillation (AF) may be sustained by localized sources (electrical rotors and focal impulses), whose elimination (Focal Impulse and Rotor Modulation, FIRM) may improve outcome from AF ablation. Background Catheter ablation for AF is a promising therapy, whose success is limited in part by uncertainty in the mechanisms that sustain AF. We developed a computational approach to map whether AF is sustained by several meandering waves (the prevailing hypothesis) or localized sources, then prospectively tested whether targeting patient-specific mechanisms revealed by mapping would improve AF ablation outcome. Methods We recruited 92 individuals during 107 consecutive ablation procedures for paroxysmal or persistent (72%) AF. Cases were prospectively treated, in a 2-arm 1:2 design, by ablation at sources (FIRM-Guided) followed by conventional ablation (n=36), or conventional ablation alone (n=71; FIRM-Blinded). Results Localized rotors or focal impulses were detected in 98 (97%) of 101 cases with sustained AF, each exhibiting 2.1±1.0 sources. The acute endpoint (AF termination or consistent slowing) was achieved in 86% of FIRM-guided versus 20% of FIRM-Blinded cases (p<0.001). FIRM ablation alone at the primary source terminated AF in 2.5 minutes (median; IQR 1.0–3.1). Total ablation time did not differ between groups (57.8±22.8 versus 52.1±17.8 minutes, p=0.16). During 273 days (median; IQR 132–681 days) after a single procedure, FIRM-Guided cases had higher freedom from AF (82.4% versus 44.9%; p<0.001) after a single procedure than FIRM-blinded cases with rigorous, often implanted, ECG monitoring. Adverse events did not differ between groups. CONCLUSIONS Localized electrical rotors and focal impulse sources are prevalent sustaining-mechanisms for human AF. FIRM ablation at patient-specific sources acutely terminated or slowed AF, and improved outcome. These results offer a novel mechanistic framework and treatment paradigm for AF. (ClinicalTrials.gov number, NCT01008722) PMID:22818076

Variable thrust/specific-impulse of multiplexed electrospray microthrusters

NASA Astrophysics Data System (ADS)

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

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

Singular value decomposition based impulsive noise reduction in multi-frequency phase-sensitive demodulation of electrical impedance tomography

NASA Astrophysics Data System (ADS)

Hao, Zhenhua; Cui, Ziqiang; Yue, Shihong; Wang, Huaxiang

2018-06-01

As an important means in electrical impedance tomography (EIT), multi-frequency phase-sensitive demodulation (PSD) can be viewed as a matched filter for measurement signals and as an optimal linear filter in the case of Gaussian-type noise. However, the additive noise usually possesses impulsive noise characteristics, so it is a challenging task to reduce the impulsive noise in multi-frequency PSD effectively. In this paper, an approach for impulsive noise reduction in multi-frequency PSD of EIT is presented. Instead of linear filters, a singular value decomposition filter is employed as the pre-stage filtering module prior to PSD, which has advantages of zero phase shift, little distortion, and a high signal-to-noise ratio (SNR) in digital signal processing. Simulation and experimental results demonstrated that the proposed method can effectively eliminate the influence of impulsive noise in multi-frequency PSD, and it was capable of achieving a higher SNR and smaller demodulation error.

A One-year, Short-Stay Crewed Mars Mission Using Bimodal Nuclear Thermal Electric Propulsion (BNTEP) - A Preliminary Assessment

NASA Technical Reports Server (NTRS)

Burke, Laura M.; Borowski, Stanley K.; McCurdy, David R.; Packard, Thomas W.

2013-01-01

A crewed mission to Mars poses a significant challenge in dealing with the physiological issues that arise with the crew being exposed to a near zero-gravity environment as well as significant solar and galactic radiation for such a long duration. While long surface stay missions exceeding 500 days are the ultimate goal for human Mars exploration, short round trip, short surface stay missions could be an important intermediate step that would allow NASA to demonstrate technology as well as study the physiological effects on the crew. However, for a 1-year round trip mission, the outbound and inbound hyperbolic velocity at Earth and Mars can be very large resulting in a significant propellant requirement for a high thrust system like Nuclear Thermal Propulsion (NTP). Similarly, a low thrust Nuclear Electric Propulsion (NEP) system requires high electrical power levels (10 megawatts electric (MWe) or more), plus advanced power conversion technology to achieve the lower specific mass values needed for such a mission. A Bimodal Nuclear Thermal Electric Propulsion (BNTEP) system is examined here that uses three high thrust Bimodal Nuclear Thermal Rocket (BNTR) engines allowing short departure and capture maneuvers. The engines also generate electrical power that drives a low thrust Electric Propulsion (EP) system used for efficient interplanetary transit. This combined system can help reduce the total launch mass, system and operational requirements that would otherwise be required for equivalent NEP or Solar Electric Propulsion (SEP) mission. The BNTEP system is a hybrid propulsion concept where the BNTR reactors operate in two separate modes. During high-thrust mode operation, each BNTR provides 10's of kilo-Newtons of thrust at reasonably high specific impulse (Isp) of 900 seconds for impulsive transplanetary injection and orbital insertion maneuvers. When in power generation/EP mode, the BNTR reactors are coupled to a Brayton power conversion system allowing each reactor to generate 100's of kWe of electrical power to a very high Isp (3000 s) EP thruster system for sustained vehicle acceleration and deceleration in heliocentric space.

69. Credit TCL. Housing of Pelton exciter impulse wheel and ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

69. Credit TCL. Housing of Pelton exciter impulse wheel and attached General Electric 60 kW exciter generator. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

Megawatt level electric propulsion perspectives

NASA Technical Reports Server (NTRS)

Jahn, Robert G.; Kelly, Arnold J.

1987-01-01

For long range space missions, deliverable payload fraction is an inverse exponential function of the propellant exhaust velocity or specific impulse of the propulsion system. The exhaust velocity of chemical systems are limited by their combustion chemistry and heat transfer to a few km/s. Nuclear rockets may achieve double this range, but are still heat transfer limited and ponderous to develop. Various electric propulsion systems can achieve exhaust velocities in the 10 km/s range, at considerably lower thrust densities, but require an external electrical power source. A general overview is provided of the currently available electric propulsion systems from the perspective of their characteristics as a terminal load for space nuclear systems. A summary of the available electric propulsion options is shown and generally characterized in the power vs. exhaust velocity plot. There are 3 general classes of electric thruster devices: neutral gas heaters, plasma devices, and space charge limited electrostatic or ion thrusters.

Trajectories for High Specific Impulse High Specific Power Deep Space Exploration

NASA Technical Reports Server (NTRS)

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

2002-01-01

Flight times and deliverable masses for electric and fusion propulsion systems are difficult to approximate. Numerical integration is required for these continuous thrust systems. Many scientists are not equipped with the tools and expertise to conduct interplanetary and interstellar trajectory analysis for their concepts. Several charts plotting the results of well-known trajectory simulation codes were developed and are contained in this paper. These charts illustrate the dependence of time of flight and payload ratio on jet power, initial mass, specific impulse and specific power. These charts are intended to be a tool by which people in the propulsion community can explore the possibilities of their propulsion system concepts. Trajectories were simulated using the tools VARITOP and IPOST. VARITOP is a well known trajectory optimization code that involves numerical integration based on calculus of variations. IPOST has several methods of trajectory simulation; the one used in this paper is Cowell's method for full integration of the equations of motion. An analytical method derived in the companion paper was also evaluated. The accuracy of this method is discussed in the paper.

Polypyrrole-chitosan conductive biomaterial synchronizes cardiomyocyte contraction and improves myocardial electrical impulse propagation.

PubMed

Cui, Zhi; Ni, Nathan C; Wu, Jun; Du, Guo-Qing; He, Sheng; Yau, Terrence M; Weisel, Richard D; Sung, Hsing-Wen; Li, Ren-Ke

2018-01-01

Background: The post-myocardial infarction (MI) scar interrupts electrical impulse propagation and delays regional contraction, which contributes to ventricular dysfunction. We investigated the potential of an injectable conductive biomaterial to restore scar tissue conductivity and re-establish synchronous ventricular contraction. Methods: A conductive biomaterial was generated by conjugating conductive polypyrrole (PPY) onto chitosan (CHI) backbones. Trypan blue staining of neonatal rat cardiomyocytes (CMs) cultured on biomaterials was used to evaluate the biocompatibility of the conductive biomaterials. Ca 2+ imaging was used to visualize beating CMs. A cryoablation injury rat model was used to investigate the ability of PPY:CHI to improve cardiac electrical propagation in the injured heart in vivo . Electromyography was used to evaluate conductivity of scar tissue ex vivo . Results: Cell survival and morphology were similar between cells cultured on biomaterials-coated and uncoated-control dishes. PPY:CHI established synchronous contraction of two distinct clusters of spontaneously-beating CMs. Intramyocardial PPY:CHI injection into the cryoablation-induced injured region improved electrical impulse propagation across the scarred tissue and decreased the QRS interval, whereas saline- or CHI-injected hearts continued to have delayed propagation patterns and significantly reduced conduction velocity compared to healthy controls. Ex vivo evaluation found that scar tissue from PPY:CHI-treated rat hearts had higher signal amplitude compared to those from saline- or CHI-treated rat heart tissue. Conclusions: The PPY:CHI biomaterial is electrically conductive, biocompatible and injectable. It improved synchronous contraction between physically separated beating CM clusters in vitro . Intra-myocardial injection of PPY:CHI following cardiac injury improved electrical impulse propagation of scar tissue in vivo .

High-Power Hall Thruster Technology Evaluated for Primary Propulsion Applications

NASA Technical Reports Server (NTRS)

Manzella, David H.; Jankovsky, Robert S.; Hofer, Richard R.

2003-01-01

High-power electric propulsion systems have been shown to be enabling for a number of NASA concepts, including piloted missions to Mars and Earth-orbiting solar electric power generation for terrestrial use (refs. 1 and 2). These types of missions require moderate transfer times and sizable thrust levels, resulting in an optimized propulsion system with greater specific impulse than conventional chemical systems and greater thrust than ion thruster systems. Hall thruster technology will offer a favorable combination of performance, reliability, and lifetime for such applications if input power can be scaled by more than an order of magnitude from the kilowatt level of the current state-of-the-art systems. As a result, the NASA Glenn Research Center conducted strategic technology research and development into high-power Hall thruster technology. During program year 2002, an in-house fabricated thruster, designated the NASA-457M, was experimentally evaluated at input powers up to 72 kW. These tests demonstrated the efficacy of scaling Hall thrusters to high power suitable for a range of future missions. Thrust up to nearly 3 N was measured. Discharge specific impulses ranged from 1750 to 3250 sec, with discharge efficiencies between 46 and 65 percent. This thruster is the highest power, highest thrust Hall thruster ever tested.

Feasibility of Colliding-beam fast-fission reactor via 238U80++238 U80+ --> 4 FF + 5n + 430 MeV beam with suppressed plutonium and direct conversion of fission fragment (FF) energy into electricity and/or Rocket propellant with high specific impulse

NASA Astrophysics Data System (ADS)

Maglich, Bogdan; Hester, Tim; Calsec Collaboration

2015-10-01

Uranium-uranium colliding beam experiment1, used fully ionized 238U92+ at energy 100GeV --> <-- 100 GeV, has measured total σ = 487 b. Reaction rate of colliding beams is proportional to neutron flux-squared. First functional Auto-Collider3-6, a compact Migma IV, 1 m in diameter, had self-colliding deuterons, D+, of 725 KeV --> <-- 725 KeV, resulting in copious production of T and 3He. U +U Autocollider``EXYDER'' will use strong-focusing magnet7, which would increase reaction rate by 104. 80 times ionized U ions accelerated through 3 MV accelerator, will collide beam 240 MeV --> <-- 240 MeV. Reaction is: 238U80+ +238 U80+ --> 4 FF + 5n + 430 MeV. Using a simple model1 fission σf ~ 100 b. Suppression of Pu by a factor of 106 will be achieved because NO thermal neutron fission can take place; only fast, 1-3 MeV, where σabs is negligible. Direct conversion of 95% of 430 MeV produced is carried by electrically charged FFs which are magnetically funneled for direct conversion of energy of FFs via electrostatic decelerators4,11. 90% of 930 MeV is electrically recoverable. Depending on the assumptions, we project electric _ power density production of 20 to 200 MWe m-3, equivalent to Thermal 1.3 - 13 GWthm-3. If one-half of unburned U is used for propulsion while rest powers system, heavy FF ion mass provides specific impulse Isp = 106 sec., 103 times higher than current rocket engines.

Optimal high- and low-thrust geocentric transfer

NASA Technical Reports Server (NTRS)

Sackett, L. L.; Edelbaum, T. N.

1974-01-01

A computer code which rapidly calculates time optimal combined high- and low-thrust transfers between two geocentric orbits in the presence of a strong gravitational field has been developed as a mission analysis tool. The low-thrust portion of the transfer can be between any two arbitrary ellipses. There is an option for including the effect of two initial high-thrust impulses which would raise the spacecraft from a low, initially circular orbit to the initial orbit for the low-thrust portion of the transfer. In addition, the effect of a single final impulse after the low-thrust portion of the transfer may be included. The total Delta V for the initial two impulses must be specified as well as the Delta V for the final impulse. Either solar electric or nuclear electric propulsion can be assumed for the low-thrust phase of the transfer.

ELECTRICAL LOAD ANTICIPATOR AND RECORDER

DOEpatents

Werme, J.E.

1961-09-01

A system is described in which an indication of the prevailing energy consumption in an electrical power metering system and a projected power demand for one demand in terval is provided at selected increments of time within the demand interval. Each watt-hour meter in the system is provided with an impulse generator that generates two impulses for each revolution of the meter disc. In each demand interval, for example, one half-hour, of the metering system, the total impulses received from all of the meters are continuously totaled for each 5-minute interval and multiplied by a number from 6 to 1 depending upon which 5- minute interval the impulses were received. This value is added to the total pulses received in the intervals preceding the current 5-minute interval within the half-hour demand interval tc thereby provide an indication of the projected power demand every 5 minutes in the demand interval.

Improved model of activation energy absorption for different electrical breakdowns in semi-crystalline insulating polymers

NASA Astrophysics Data System (ADS)

Sima, Wenxia; Jiang, Xiongwei; Peng, Qingjun; Sun, Potao

2018-05-01

Electrical breakdown is an important physical phenomenon in electrical equipment and electronic devices. Many related models and theories of electrical breakdown have been proposed. However, a widely recognized understanding on the following phenomenon is still lacking: impulse breakdown strength which varies with waveform parameters, decrease in the breakdown strength of AC voltage with increasing frequency, and higher impulse breakdown strength than that of AC. In this work, an improved model of activation energy absorption for different electrical breakdowns in semi-crystalline insulating polymers is proposed based on the Harmonic oscillator model. Simulation and experimental results show that, the energy of trapped charges obtained from AC stress is higher than that of impulse voltage, and the absorbed activation energy increases with the increase in the electric field frequency. Meanwhile, the frequency-dependent relative dielectric constant ε r and dielectric loss tanδ also affect the absorption of activation energy. The absorbed activation energy and modified trap level synergistically determine the breakdown strength. The mechanism analysis of breakdown strength under various voltage waveforms is consistent with the experimental results. Therefore, the proposed model of activation energy absorption in the present work may provide a new possible method for analyzing and explaining the breakdown phenomenon in semi-crystalline insulating polymers.

Electrolysis Propulsion Provides High-Performance, Inexpensive, Clean Spacecraft Propulsion

NASA Technical Reports Server (NTRS)

deGroot, Wim A.

1999-01-01

An electrolysis propulsion system consumes electrical energy to decompose water into hydrogen and oxygen. These gases are stored in separate tanks and used when needed in gaseous bipropellant thrusters for spacecraft propulsion. The propellant and combustion products are clean and nontoxic. As a result, costs associated with testing, handling, and launching can be an order of magnitude lower than for conventional propulsion systems, making electrolysis a cost-effective alternative to state-of-the-art systems. The electrical conversion efficiency is high (>85 percent), and maximum thrust-to-power ratios of 0.2 newtons per kilowatt (N/kW), a 370-sec specific impulse, can be obtained. A further advantage of the water rocket is its dual-mode potential. For relatively high thrust applications, the system can be used as a bipropellant engine. For low thrust levels and/or small impulse bit requirements, cold gas oxygen can be used alone. An added innovation is that the same hardware, with modest modifications, can be converted into an energy-storage and power-generation fuel cell, reducing the spacecraft power and propulsion system weight by an order of magnitude.

Computational Electromagnetic Studies for Low-Frequency Compensation of the Reflector Impulse-radiating Antenna

DTIC Science & Technology

2015-03-26

COMPUTATIONAL ELECTROMAGNETIC STUDIES FOR LOW-FREQUENCY COMPENSATION OF THE REFLECTOR IMPULSE-RADIATING ANTENNA THESIS Casey E. Fillmore, Capt, USAF... ELECTROMAGNETIC STUDIES FOR LOW-FREQUENCY COMPENSATION OF THE REFLECTOR IMPULSE-RADIATING ANTENNA THESIS Presented to the Faculty Department of Electrical and...2015 DISTRIBUTION STATEMENT A APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. AFIT-ENG-MS-15-M-011 COMPUTATIONAL ELECTROMAGNETIC STUDIES FOR LOW

Space-to-Space Power Beaming Enabling High Performance Rapid Geocentric Orbit Transfer

NASA Technical Reports Server (NTRS)

Dankanich, John W.; Vassallo, Corinne; Tadge, Megan

2015-01-01

The use of electric propulsion is more prevalent than ever, with industry pursuing all electric orbit transfers. Electric propulsion provides high mass utilization through efficient propellant transfer. However, the transfer times become detrimental as the delta V transitions from near-impulsive to low-thrust. Increasing power and therefore thrust has diminishing returns as the increasing mass of the power system limits the potential acceleration of the spacecraft. By using space-to-space power beaming, the power system can be decoupled from the spacecraft and allow significantly higher spacecraft alpha (W/kg) and therefore enable significantly higher accelerations while maintaining high performance. This project assesses the efficacy of space-to-space power beaming to enable rapid orbit transfer while maintaining high mass utilization. Concept assessment requires integrated techniques for low-thrust orbit transfer steering laws, efficient large-scale rectenna systems, and satellite constellation configuration optimization. This project includes the development of an integrated tool with implementation of IPOPT, Q-Law, and power-beaming models. The results highlight the viability of the concept, limits and paths to infusion, and comparison to state-of-the-art capabilities. The results indicate the viability of power beaming for what may be the only approach for achieving the desired transit times with high specific impulse.

Method of measuring the dc electric field and other tokamak parameters

DOEpatents

Fisch, Nathaniel J.; Kirtz, Arnold H.

1992-01-01

A method including externally imposing an impulsive momentum-space flux to perturb hot tokamak electrons thereby producing a transient synchrotron radiation signal, in frequency-time space, and the inference, using very fast algorithms, of plasma parameters including the effective ion charge state Z.sub.eff, the direction of the magnetic field, and the position and width in velocity space of the impulsive momentum-space flux, and, in particular, the dc toroidal electric field.

Simulated Prompt Acceleration of Multi-MeV Electrons by the 17 March 2015 Interplanetary Shock

NASA Astrophysics Data System (ADS)

Hudson, Mary; Jaynes, Allison; Kress, Brian; Li, Zhao; Patel, Maulik; Shen, Xiao-Chen; Thaller, Scott; Wiltberger, Michael; Wygant, John

2017-10-01

Prompt enhancement of relativistic electron flux at L = 3-5 has been reported from Van Allen Probes Relativistic Electron Proton Telescope (REPT) measurements associated with the 17 March 2015 interplanetary shock compression of the dayside magnetosphere. Acceleration by ˜1 MeV is inferred on less than a drift timescale as seen in prior shock compression events, which launch a magnetosonic azimuthal electric field impulse tailward. This impulse propagates from the dayside around the flanks accelerating electrons in drift resonance at the dusk flank. Such longitudinally localized acceleration events produce a drift echo signature which was seen at >1 MeV energy on both Van Allen Probe spacecraft, with sustained observations by Probe B outbound at L = 5 at 2100 MLT at the time of impulse arrival, measured by the Electric Fields and Waves instrument. MHD test particle simulations are presented which reproduce drift echo features observed in the REPT measurements at Probe B, including the energy and pitch angle dependence of drift echoes observed. While the flux enhancement was short lived for this event due to subsequent inward motion of the magnetopause, stronger events with larger electric field impulses, as observed in March 1991 and the Halloween 2003 storm, produce enhancements which can be quantified by the inward radial transport and energization determined by the induction electric field resulting from dayside compression.

Round-Trip Solar Electric Propulsion Missions for Mars Sample Return

NASA Technical Reports Server (NTRS)

Bailey, Zachary J.; Sturm, Erick J.; Kowalkowski, Theresa D.; Lock, Robert E.; Woolley, Ryan C.; Nicholas, Austin K.

2014-01-01

Mars Sample Return (MSR) missions could benefit from the high specific impulse of Solar Electric Propulsion (SEP) to achieve lower launch masses than with chemical propulsion. SEP presents formulation challenges due to the coupled nature of launch vehicle performance, propulsion system, power system, and mission timeline. This paper describes a SEP orbiter-sizing tool, which models spacecraft mass & timeline in conjunction with low thrust round-trip Earth-Mars trajectories, and presents selected concept designs. A variety of system designs are possible for SEP MSR orbiters, with large dry mass allocations, similar round-trip durations to chemical orbiters, and reduced design variability between opportunities.

Simulation of Trajectories for High Specific Impulse Deep Space Exploration

NASA Technical Reports Server (NTRS)

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

2002-01-01

Difficulties in approximating flight times and deliverable masses for continuous thrust propulsion systems have complicated comparison and evaluation of proposed propulsion concepts. These continuous thrust propulsion systems are of interest to many groups, not the least of which are the electric propulsion and fusion communities. Several charts plotting the results of well-known trajectory simulation codes were developed and are contained in this paper. These charts illustrate the dependence of time of flight and payload ratio on jet power, initial mass, specific impulse and specific power. These charts are intended to be a tool by which people in the propulsion community can explore the possibilities of their propulsion system concepts. Trajectories were simulated using the tools VARITOP and IPOST. VARITOP is a well known trajectory optimization code that involves numerical integration based on calculus of variations. IPOST has several methods of trajectory simulation; the one used in this paper is Cowell's method for full integration of the equations of motion. The analytical method derived in the companion paper was also used to simulate the trajectory. The accuracy of this method is discussed in the paper.

Heart Anatomy

MedlinePlus

... aorta, your body’s largest artery. The Conduction System Electrical impulses from your heart muscle (the myocardium) cause your heart to contract. This electrical signal begins in the sinoatrial (SA) node, located ...

Nuclear electric power for multimegawatt orbit transfer vehicles

NASA Astrophysics Data System (ADS)

Casagrande, R. D.

Multimegawatt nuclear propulsion is an attractive option for orbit transfer vehicles. The masses of these platforms are expected to exceed the capability of a single launch from Earth necessitating assembly in space in a parking orbit. The OTV would transfer the platform from the parking orbit to the operational orbit and then return for the next mission. Electric propulsion is advantageous because of the high specific impulse achieved by the technology, 1000 to 5000 s and beyond, to reduce the propellant required. Nuclear power is attractive as the power system because of the weight savings over solar systems in the multimegawatt regime, and multimegawatts of power are required. A conceptual diagram is shown of an OTV with a command control module using electric thrusters powered from an SP-100 class nuclear reactor power system.

Study of electric field distorted by space charges under positive lightning impulse voltage

NASA Astrophysics Data System (ADS)

Wang, Zezhong; Geng, Yinan

2018-03-01

Actually, many insulation problems are related to electric fields. And measuring electric fields is an important research topic of high-voltage engineering. In particular, the electric field distortion caused by space charge is the basis of streamer theory, and thus quantitatively measuring the Poisson electric field caused by space charge is significant to researching the mechanism of air gap discharge. In this paper, we used our photoelectric integrated sensor to measure the electric field distribution in a 1-m rod-plane gap under positive lightning impulse voltage. To verify the reliability of this quantitative measurement, we compared the measured results with calculated results from a numerical simulation. The electric-field time domain waveforms on the axis of the 1-m rod-plane out of the space charge zone were measured with various electrodes. The Poisson electric fields generated by space charge were separated from the Laplace electric field generated by applied voltages, and the amplitudes and variations were measured for various applied voltages and at various locations. This work also supplies the feasible basis for directly measuring strong electric field under high voltage.

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

An Inversion Method for Reconstructing Hall Thruster Plume Parameters from the Line Integrated Measurements (Postprint)

DTIC Science & Technology

2007-07-01

Technical Paper 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER An Inversion Method for Reconstructing Hall Thruster Plume...298 (Rev. 8-98) Prescribed by ANSI Std. 239.18 An Inversion Method for Reconstructing Hall Thruster Plume Parameters from Line Integrated Measurements... Hall thruster is a high specific impulse electric thruster that produces a highly ionized plasma inside an annular chamber through the use of high

Performance trade studies of a solar electric orbit transfer mission

NASA Astrophysics Data System (ADS)

Sutton, D. M.; McLain, M. G.; Kechichian, J. A.

An analysis of several electric orbit transfer trade studies investigating the performance of a solar-powered electric orbit transfer vehicle (EOTV) is presented. One trade illustrates how the greatest payload capability for time-of-flight constrained transfers can be obtained by optimizing specific impulse. Various methods of reducing the accumulated fluence of charged particles during transit are evaluated in a second trade study. The reduction in fluence obtained by shaping the trajectory to avoid high radiation flux density regions is compared with reductions obtained by using a hybrid chemical/electric vehicle, by additional radiation-protective coverslide material added to the solar array, and by increasing the power of the vehicle. It is shown that a trajectory shaped to minimize fluence may be an advantage to the complete EOTV design. A final trade study shows how park orbit altitude influences the initial thrust-to-drag ratio of an EOTV.

14. POWERHOUSE INTERIOR, EXCITER No. 2 SHOWING GENERAL ELECTRIC INDUCTION ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

14. POWERHOUSE INTERIOR, EXCITER No. 2 SHOWING GENERAL ELECTRIC INDUCTION MOTOR IN SERIES BETWEEN PELTON-DOBLE IMPULSE WHEEL AND GENERAL ELECTRIC GENERATOR. VIEW TO EAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

Categories of Arrhythmias

MedlinePlus

... 60 beats per minute. It happens when the electrical impulse that signals the heart to contract is ... the ventricles. Instead, other areas along the lower electrical pathway take over the pacemaking role. Since the ...

Premature Ventricular Contractions (PVCs)

MedlinePlus

... This natural pacemaker produces the electrical impulses that trigger the normal heartbeat. From the sinus node, electrical ... occur? The reasons aren't always clear. Certain triggers, heart diseases or changes in the body can ...

Electric propulsion for lunar exploration and lunar base development

NASA Technical Reports Server (NTRS)

Palaszewski, Bryan

1992-01-01

Using electric propulsion to deliver materials to lunar orbit for the development and construction of a lunar base was investigated. Because the mass of the base and its life-cycle resupply mass are large, high specific impulse propulsion systems may significantly reduce the transportation system mass and cost. Three electric propulsion technologies (arcjet, ion, and magnetoplasmadynamic (MPD) propulsion) were compared with oxygen/hydrogen propulsion for a lunar base development scenario. Detailed estimates of the orbital transfer vehicles' (OTV's) masses and their propellant masses are presented. The fleet sizes for the chemical and electric propulsion systems are estimated. Ion and MPD propulsion systems enable significant launch mass savings over O2/H2 propulsion. Because of the longer trip time required for the low-thrust OTV's, more of them are required to perform the mission model. By offloading the lunar cargo from the manned O2/H2 OTV missions onto the electric propulsion OTV's, a significant reduction of the low Earth orbit (LEO) launch mass is possible over the 19-year base development period.

Feasibility demonstration of booster cross-over system for 3 1/2 inch SRB/MLP frangible nut system

NASA Technical Reports Server (NTRS)

1983-01-01

Recent testing of the SRB/MLP Frangible Nut System (SOS Part Number 114850-9/Boosters P/N 114848-3) at NASA indicated a need to reduce the function time between boosters (2) within a single frangible nut. These boosters are initiated separately by electrical impulse(s). Coupling the output of each detonator with an explosive cross-over would reduce the function time between boosters (independent of electrical impulse) while providing additional redundancy to the system. The objectives of this program were to: provide an explosive cross-over between boosters, reduce function time between boosters to less than one (1) millisecond within a given nut, reduce cost of boosters, be compatible with the existing frangible nut system, and meet requirements of USBI Spec's (nut 10SPC-0030, booster 10SPC-0031).

Electric Propulsion System Selection Process for Interplanetary Missions

NASA Technical Reports Server (NTRS)

Landau, Damon; Chase, James; Kowalkowski, Theresa; Oh, David; Randolph, Thomas; Sims, Jon; Timmerman, Paul

2008-01-01

The disparate design problems of selecting an electric propulsion system, launch vehicle, and flight time all have a significant impact on the cost and robustness of a mission. The effects of these system choices combine into a single optimization of the total mission cost, where the design constraint is a required spacecraft neutral (non-electric propulsion) mass. Cost-optimal systems are designed for a range of mass margins to examine how the optimal design varies with mass growth. The resulting cost-optimal designs are compared with results generated via mass optimization methods. Additional optimizations with continuous system parameters address the impact on mission cost due to discrete sets of launch vehicle, power, and specific impulse. The examined mission set comprises a near-Earth asteroid sample return, multiple main belt asteroid rendezvous, comet rendezvous, comet sample return, and a mission to Saturn.

Pulsed plasmoid electric propulsion

NASA Technical Reports Server (NTRS)

Bourque, Robert F.; Parks, Paul B.; Tamano, Teruo

1990-01-01

A method of electric propulsion is explored where plasmoids such as spheromaks and field reversed configurations (FRC) are formed and then allowed to expand down a diverging conducting shell. The plasmoids contain a toroidal electric current that provides both heating and a confining magnetic field. They are free to translate because there are no externally supplied magnetic fields that would restrict motion. Image currents in the diverging conducting shell keep the plasmoids from contacting the wall. Because these currents translate relative to the wall, losses due to magnetic flux diffusion into the wall are minimized. During the expansion of the plasma in the diverging cone, both the inductive and thermal plasma energy are converted to directed kinetic energy producing thrust. Specific impulses can be in the 4000 to 20000 sec range with thrusts from 0.1 to 1000 Newtons, depending on available power.

Status of Low Thrust Work at JSC

NASA Technical Reports Server (NTRS)

Condon, Gerald L.

2004-01-01

High performance low thrust (solar electric, nuclear electric, variable specific impulse magnetoplasma rocket) propulsion offers a significant benefit to NASA missions beyond low Earth orbit. As NASA (e.g., Prometheus Project) endeavors to develop these propulsion systems and associated power supplies, it becomes necessary to develop a refined trajectory design capability that will allow engineers to develop future robotic and human mission designs that take advantage of this new technology. This ongoing work addresses development of a trajectory design and optimization tool for assessing low thrust (and other types) trajectories. This work targets to advance the state of the art, enable future NASA missions, enable science drivers, and enhance education. This presentation provides a summary of the low thrust-related JSC activities under the ISP program and specifically, provides a look at a new release of a multi-gravity, multispacecraft trajectory optimization tool (Copernicus) along with analysis performed using this tool over the past year.

Electric field and space charge distribution measurement in transformer oil struck by impulsive high voltage

NASA Astrophysics Data System (ADS)

Sima, Wenxia; Guo, Hongda; Yang, Qing; Song, He; Yang, Ming; Yu, Fei

2015-08-01

Transformer oil is widely used in power systems because of its excellent insulation properties. The accurate measurement of electric field and space charge distribution in transformer oil under high voltage impulse has important theoretical and practical significance, but still remains challenging to date because of its low Kerr constant. In this study, the continuous electric field and space charge distribution over time between parallel-plate electrodes in high-voltage pulsed transformer oil based on the Kerr effect is directly measured using a linear array photoelectrical detector. Experimental results demonstrate the applicability and reliability of this method. This study provides a feasible approach to further study the space charge effects and breakdown mechanisms in transformer oil.

Magnetic Nozzle and Plasma Detachment Experiment

NASA Technical Reports Server (NTRS)

Chavers, Gregory; Dobson, Chris; Jones, Jonathan; Martin, Adam; Bengtson, Roger D.; Briezman, Boris; Arefiev, Alexey; Cassibry, Jason; Shuttpelz, Branwen; Deline, Christopher

2006-01-01

High power plasma propulsion can move large payloads for orbit transfer (such as the ISS), lunar missions, and beyond with large savings in fuel consumption owing to the high specific impulse. At high power, lifetime of the thruster becomes an issue. Electrodeless devices with magnetically guided plasma offer the advantage of long life since magnetic fields confine the plasma radially and keep it from impacting the material surfaces. For decades, concerns have been raised about the plasma remaining attached to the magnetic field and returning to the vehicle along the closed magnetic field lines. Recent analysis suggests that this may not be an issue of the magnetic field is properly shaped in the nozzle region and the plasma has sufficient energy density to stretch the magnetic field downstream. An experiment was performed to test the theory regarding the Magneto-hydrodynamic (MHD) detachment scenario. Data from this experiment will be presented. The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) being developed by the Ad Astra Rocket Company uses a magnetic nozzle as described above. The VASIMR is also a leading candidate for exploiting an electric propulsion test platform being considered for the ISS.

Rarefied gas electro jet (RGEJ) micro-thruster for space propulsion

NASA Astrophysics Data System (ADS)

Blanco, Ariel; Roy, Subrata

2017-11-01

This article numerically investigates a micro-thruster for small satellites which utilizes plasma actuators to heat and accelerate the flow in a micro-channel with rarefied gas in the slip flow regime. The inlet plenum condition is considered at 1 Torr with flow discharging to near vacuum conditions (<0.05 Torr). The Knudsen numbers at the inlet and exit planes are ~0.01 and ~0.1, respectively. Although several studies have been performed in micro-hallow cathode discharges at constant pressure, to our knowledge, an integrated study of the glow discharge physics and resulting fluid flow of a plasma thruster under these low pressure and low Knudsen number conditions is yet to be reported. Numerical simulations of the charge distribution due to gas ionization processes and the resulting rarefied gas flow are performed using an in-house code. The mass flow rate, thrust, specific impulse, power consumption and the thrust effectiveness of the thruster are predicted based on these results. The ionized gas is modelled using local mean energy approximation. An electrically induced body force and a thermal heating source are calculated based on the space separated charge distribution and the ion Joule heating, respectively. The rarefied gas flow with these electric force and heating source is modelled using density-based compressible flow equations with slip flow boundary conditions. The results show that a significant improvement of specific impulse can be achieved over highly optimized cold gas thrusters using the same propellant.

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.

Crosswell electromagnetic modeling from impulsive source: Optimization strategy for dispersion suppression in convolutional perfectly matched layer

PubMed Central

Fang, Sinan; Pan, Heping; Du, Ting; Konaté, Ahmed Amara; Deng, Chengxiang; Qin, Zhen; Guo, Bo; Peng, Ling; Ma, Huolin; Li, Gang; Zhou, Feng

2016-01-01

This study applied the finite-difference time-domain (FDTD) method to forward modeling of the low-frequency crosswell electromagnetic (EM) method. Specifically, we implemented impulse sources and convolutional perfectly matched layer (CPML). In the process to strengthen CPML, we observed that some dispersion was induced by the real stretch κ, together with an angular variation of the phase velocity of the transverse electric plane wave; the conclusion was that this dispersion was positively related to the real stretch and was little affected by grid interval. To suppress the dispersion in the CPML, we first derived the analytical solution for the radiation field of the magneto-dipole impulse source in the time domain. Then, a numerical simulation of CPML absorption with high-frequency pulses qualitatively amplified the dispersion laws through wave field snapshots. A numerical simulation using low-frequency pulses suggested an optimal parameter strategy for CPML from the established criteria. Based on its physical nature, the CPML method of simply warping space-time was predicted to be a promising approach to achieve ideal absorption, although it was still difficult to entirely remove the dispersion. PMID:27585538

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.

Integrated Studies of Electric Propulsion Engines during Flights in the Earth's Ionosphere

NASA Astrophysics Data System (ADS)

Marov, M. Ya.; Filatyev, A. S.

2018-03-01

Fifty years ago, on October 1, 1966, the first Yantar satellite laboratory with a gas plasma-ion electric propulsion was launched into orbit as part of the Yantar Soviet space program. In 1966-1971, the program launched a total of four laboratories with thrusters operating on argon, nitrogen, and air with jet velocities of 40, 120, and 140 km/s, respectively. These space experiments were the first to demonstrate the long-term stable operation of these thrusters, which exceed chemical rocket engines in specific impulse by an order of magnitude and provide effective jet charge compensation, under the conditions of a real flight at altitudes of 100-400 km. In this article, we have analyzed the potential modern applications of the scientific results obtained by the Yantar space program for the development of air-breathing electric propulsion that ensure the longterm operation of spacecraft in very low orbits.

Electric propulsion for near-Earth space missions

NASA Technical Reports Server (NTRS)

Terwilliger, C. H.; Smith, W. W.

1980-01-01

A set of missions was postulated that was considered to be representative of those likely to be desirable/feasible over the next three decades. The characteristics of these missions, and their payloads, that most impact the choice/design of the requisite propulsion system were determined. A system-level model of the near-Earth transportation process was constructed, which incorporated these mission/system characteristics, as well as the fundamental parameters describing the technology/performance of an ion bombardment based electric propulsion system. The model was used for sensitivity studies to determine the interactions between the technology descriptors and program costs, and to establish the most cost-effective directions for technology advancement. The most important factor was seen to be the costs associated with the duration of the mission, and this in turn makes the development of advanced electric propulsion systems having moderate to high efficiencies ( 50 percent) at intermediate ranges of specific impulse (approximately 1000 seconds) very desirable.

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.

Finite-element time-domain algorithms for modeling linear Debye and Lorentz dielectric dispersions at low frequencies.

PubMed

Stoykov, Nikolay S; Kuiken, Todd A; Lowery, Madeleine M; Taflove, Allen

2003-09-01

We present what we believe to be the first algorithms that use a simple scalar-potential formulation to model linear Debye and Lorentz dielectric dispersions at low frequencies in the context of finite-element time-domain (FETD) numerical solutions of electric potential. The new algorithms, which permit treatment of multiple-pole dielectric relaxations, are based on the auxiliary differential equation method and are unconditionally stable. We validate the algorithms by comparison with the results of a previously reported method based on the Fourier transform. The new algorithms should be useful in calculating the transient response of biological materials subject to impulsive excitation. Potential applications include FETD modeling of electromyography, functional electrical stimulation, defibrillation, and effects of lightning and impulsive electric shock.

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.

Piezoelectric-based self-powered electronic adjustable impulse switches

NASA Astrophysics Data System (ADS)

Rastegar, Jahangir; Kwok, Philip

2018-03-01

Novel piezoelectric-based self-powered impulse detecting switches are presented. The switches are designed to detect shock loading events resulting in acceleration or deceleration above prescribed levels and durations. The prescribed acceleration level and duration thresholds are adjustable. They are provided with false trigger protection logic. The impulse switches are provided with electronic and logic circuitry to detect prescribed impulse events and reject events such as high amplitude but short duration shocks, and transportation vibration and similar low amplitude and relatively long duration events. They can be mounted directly onto electronics circuit boards, thereby significantly simplifying the electrical and electronic circuitry, simplifying the assembly process and total cost, significantly reducing the occupied volume, and in some applications eliminating the need for physical wiring to and from the impulse switches. The design of prototypes and testing under realistic conditions are presented.

Impulse Plasma In Surface Engineering - a review

NASA Astrophysics Data System (ADS)

Zdunek, K.; Nowakowska-Langier, K.; Chodun, R.; Okrasa, S.; Rabinski, M.; Dora, J.; Domanowski, P.; Halarowicz, J.

2014-11-01

The article describes the view of the plasma surface engineering, assuming the role of non-thermal energy effects in the synthesis of materials and coatings deposition. In the following study it was underlined that the vapor excitation through the application of an electric field during coatings deposition gives new possibilities for coatings formation. As an example the IPD method was chosen. During the IPD (Impulse Plasma Deposition) the impulse plasma is generated in the coaxial accelerator by strong periodic electrical pulses. The impulse plasma is distributed in the form of energetic plasma pockets. Due to the almost completely ionization of gas, the nucleation of new phases takes place on ions directly in the plasma itself. As a result the coatings of metastable materials with nano-amorphous structure and excellent adhesion to the non-heated intentionally substrates could be deposited. Recently the novel way of impulse plasma generation during the coatings deposition was proposed and developed by our group. An efficient tool for plasma process control, the plasma forming gas injection to the interelectrode space was used. Periodic changing the gas pressure results in increasing both the degree of dispersion and the dynamics of the plasma pulses. The advantage of the new technique in deposition of coatings with exceptionally good properties has been demonstrated in the industrial scale not only in the case of the IPD method but also in the case of very well known magnetron sputtering method.

Design, fabrication, and operation of dished accelerator grids on a 30-cm ion thruster

NASA Technical Reports Server (NTRS)

Rawlin, V. K.; Banks, B. A.; Byers, D. C.

1972-01-01

Several closely-space dished accelerator grid systems were fabricated and tested on a 30-cm diameter mercury bombardment thruster and they appear to be a solution to the stringent requirements imposed by the near-term, high-thrust, low specific impulse electric propulsion missions. The grids were simultaneously hydroformed and then simultaneously stress relieved. The ion extraction capability and discharge chamber performance were studied as the total accelerating voltage, the ratio of net-to-total voltage, grid spacing, and dish direction were varied.

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.

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of the mylohyoid muscle in rabbits under conditions of hunger and satiety.

PubMed

Ignatova, Ju P; Kromin, A A

2011-03-01

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of mylohyoid muscle were studied in chronic experiments under conditions of hunger and satiety. Threshold stimulation of the lateral hypothalamus in starving and satiated rabbits in the absence of food induced searching behavior associated with burst-like impulse activity with a bimodal distribution of interpulse intervals. Regular spike burst in the mylohyoid muscle during stimulation of the lateral hypothalamus in the absence of food serves as an example of the anticipatory type reaction. Increased food motivation during threshold stimulation of the lateral hypothalamus in starving and satiated rabbits with food offered led to successful food-procuring behavior, during which the frequency of spike bursts in the mylohyoid muscle became comparable with that under conditions of natural foraging behavior stimulated by the need in nutrients. Our results suggest that temporal structure of mylohyoid muscle impulse activity reflects convergent interactions of food-motivation excitation with reinforcement excitation on neurons of the masticatory and deglutitive centers.

Voyager Uranus encounter 0.2lbf T/VA short pulse test report

NASA Technical Reports Server (NTRS)

1986-01-01

The attitude control thrusters on the Voyager spacecraft were tested for operation at electrical pulse widths of less than the current 10-millisecond minimum to reduce impulse bit and, therefore, reduce image smear of pictures taken during the Uranus encounter. Thrusters with the identical configuration of the units on the spacecraft were fired in an altitude chamber to characterize impulse bit and impulse bit variations as a function of electrical pulse widths and to determine if the short pulses decreased thruster life. Pulse widths of 4.0 milliseconds provide approximately 45 percent of the impulse provided by a 10-ms pulse, and thruster-to-thruster and pulse-to-pulse variation is approximately plus or minus 10 percent. Pulse widths shorter than 4 ms showed wide variation, and no pulse was obtained at 3 ms. Three thrusters were each subjected to 75,000 short pulses of 4 ms or less without performance degradation. A fourth thruster exhibited partial flow blockage after 13,000 short pulses, but this was attributed to prevous test history and not short pulse exposure. The Voyager attitude control thrusters should be considered flight qualified for short pulse operation at pulse widths of 4.0 ms or more.

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.

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.

The Air Force Phillips Laboratory multimegawatt quasi-steady MPD thruster facility

NASA Astrophysics Data System (ADS)

Castillo, Salvador; Tilley, Dennis L.

1992-07-01

The operational multimegawatt quasi-steady MPD thruster facility is described in terms of its general design emphasizing the impulse thrust stand and diagnostics capabilities. The vacuum, propellant, and electrical systems are discussed with schematic diagrams of the respective component configurations and explanations of the needs of MPD thruster testing. The impulse thrust stand comprises an accelerometer/pendulum-impulse stand which can be used to correlate thruster impulse with accelerometer readings and thereby reduce measurement uncertainties. The diagnostics of the terminal characteristics of the thruster operation are complemented by diagnostics platforms that study plasma properties in the plume and the thruster. Preliminary tests indicate that the MPD thruster facility is prepared for detailed investigations of MPD thruster performance and plume diagnostics.

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.

Experimental Study of Propulsion Performance by Single-Pulse Rotating Detonation with Gaseous Fuels-Oxygen Mixtures

NASA Astrophysics Data System (ADS)

Toshimitsu, Kazuhiko; Hara, Kosei; Mikajiri, Shuuto; Takiguchi, Naoki

2016-12-01

A rotating detonation engine (RDE) is one of candidates of aerospace engines for supersonic cruse, which is better for propulsion system than a pulse detonation engine (PDE) from the view of continuous thrust and simple structure. The propulsion performance of a proto-type RDE and a PDE by single pulse explosion with methane-oxygen is investigated. Furthermore, the performance of the RDE with acetylene-oxygen gas mixtures is investigated. Its impulse is estimated through ballistic pendulum method with maximum displacement and damping ratio. The comparison of specific impulses of the mixture gases at atmospheric pressure is shown. The specific impulses of the RDE and the PDE are almost same with methane-oxygen gas. Furthermore, the fuel-base specific impulse of the RDE with acetylene-oxygen gas is about over twice as large as one of methane-oxygen, and its maximum specific impulse is 1100 seconds.

Specific Impulse and Mass Flow Rate Error

NASA Technical Reports Server (NTRS)

Gregory, Don A.

2005-01-01

Specific impulse is defined in words in many ways. Very early in any text on rocket propulsion a phrase similar to .specific impulse is the thrust force per unit propellant weight flow per second. will be found.(2) It is only after seeing the mathematics written down does the definition mean something physically to scientists and engineers responsible for either measuring it or using someone.s value for it.

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.

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.

Source locations for impulsive electric signals seen in the night ionosphere of Venus

NASA Technical Reports Server (NTRS)

Russell, C. T.; Von Dornum, M.; Scarf, F. L.

1989-01-01

A mapping of the rate of occurrence of impulsive VLF noise bursts in Venus' dark low altitude ionosphere, which increases rapidly with decreasing altitude, as a function of latitude and longitude indicates enhanced occurrence rates over Atla. In a 30-sec observing period, there are impulsive signals 70 percent of the time at 160 km in the region of maximum occurrence; the occurrence rates, moreover, increase with decreasing latitude, so that the equatorial rate is of the order of 1.6 times that at 30 deg latitude. These phenomena are in keeping with lightning-generated wave sources.

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.

Novel high power impulse magnetron sputtering enhanced by an auxiliary electrical field

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

Li, Chunwei, E-mail: lcwnefu@126.com, E-mail: xiubotian@163.com; State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001; Tian, Xiubo, E-mail: lcwnefu@126.com, E-mail: xiubotian@163.com

2016-08-15

The high power impulse magnetron sputtering (HIPIMS) technique is a novel highly ionized physical vapor deposition method with a high application potential. However, the electron utilization efficiency during sputtering is rather low and the metal particle ionization rate needs to be considerably improved to allow for a large-scale industrial application. Therefore, we enhanced the HIPIMS technique by simultaneously applying an electric field (EF-HIPIMS). The effect of the electric field on the discharge process was studied using a current sensor and an optical emission spectrometer. Furthermore, the spatial distribution of the electric potential and electric field during the EF-HIPIMS process wasmore » simulated using the ANSYS software. The results indicate that a higher electron utilization efficiency and a higher particle ionization rate could be achieved. The auxiliary anode obviously changed the distribution of the electric potential and the electric field in the discharge region, which increased the plasma density and enhanced the degree of ionization of the vanadium and argon gas. Vanadium films were deposited to further compare both techniques, and the morphology of the prepared films was investigated by scanning electron microscopy. The films showed a smaller crystal grain size and a denser growth structure when the electric field was applied during the discharge process.« less

Foundational Methane Propulsion Related Technology Efforts, and Challenges for Applications to Human Exploration Beyond Earth Orbit

NASA Technical Reports Server (NTRS)

Brown, Thomas; Klem, Mark; McRight, Patrick

2016-01-01

Current interest in human exploration beyond earth orbit is driving requirements for high performance, long duration space transportation capabilities. Continued advancement in photovoltaic power systems and investments in high performance electric propulsion promise to enable solar electric options for cargo delivery and pre-deployment of operational architecture elements. However, higher thrust options are required for human in-space transportation as well as planetary descent and ascent functions. While high thrust requirements for interplanetary transportation may be provided by chemical or nuclear thermal propulsion systems, planetary descent and ascent systems are limited to chemical solutions due to their higher thrust to weight and potential planetary protection concerns. Liquid hydrogen fueled systems provide high specific impulse, but pose challenges due to low propellant density and the thermal issues of long term propellant storage. Liquid methane fueled propulsion is a promising compromise with lower specific impulse, higher bulk propellant density and compatibility with proposed in-situ propellant production concepts. Additionally, some architecture studies have identified the potential for commonality between interplanetary and descent/ascent propulsion solutions using liquid methane (LCH4) and liquid oxygen (LOX) propellants. These commonalities may lead to reduced overall development costs and more affordable exploration architectures. With this increased interest, it is critical to understand the current state of LOX/LCH4 propulsion technology and the remaining challenges to its application to beyond earth orbit human exploration. This paper provides a survey of NASA's past and current methane propulsion related technology efforts, assesses the accomplishments to date, and examines the remaining risks associated with full scale development.

Kerr electro-optic field mapping study of the effect of charge injection on the impulse breakdown strength of transformer oil

NASA Astrophysics Data System (ADS)

Zhang, X.; Zahn, M.

2013-10-01

The smart use of charge injection to improve breakdown strength in transformer oil is demonstrated in this paper. Hypothetically, bipolar homo-charge injection with reduced electric field at both electrodes may allow higher voltage operation without insulation failure, since electrical breakdown usually initiates at the electrode-dielectric interfaces. To find experimental evidence, the applicability and limitation of the hypothesis is first analyzed. Impulse breakdown tests and Kerr electro-optic field mapping measurements are then conducted with different combinations of parallel-plate aluminum and brass electrodes stressed by millisecond duration impulse. It is found that the breakdown voltage of brass anode and aluminum cathode is ˜50% higher than that of aluminum anode and brass cathode. This can be explained by charge injection patterns from Kerr measurements under a lower voltage, where aluminum and brass electrodes inject negative and positive charges, respectively. This work provides a feasible approach to investigating the effect of electrode material on breakdown strength.

Detecting electroporation by assessing the time constants in the exponential response of human skin to voltage controlled impulse electrical stimulation.

PubMed

Bîrlea, Sinziana I; Corley, Gavin J; Bîrlea, Nicolae M; Breen, Paul P; Quondamatteo, Fabio; OLaighin, Gearóid

2009-01-01

We propose a new method for extracting the electrical properties of human skin based on the time constant analysis of its exponential response to impulse stimulation. As a result of this analysis an adjacent finding has arisen. We have found that stratum corneum electroporation can be detected using this analysis method. We have observed that a one time-constant model is appropriate for describing the electrical properties of human skin at low amplitude applied voltages (<30V), and a two time-constant model best describes skin electrical properties at higher amplitude applied voltages (>30V). Higher voltage amplitudes (>30V) have been proven to create pores in the skin's stratum corneum which offer a new, lower resistance, pathway for the passage of current through the skin. Our data shows that when pores are formed in the stratum corneum they can be detected, in-vivo, due to the fact that a second time constant describes current flow through them.

High Power Electric Propulsion Using The VASIMR VX-200: A Flight Technology Prototype

NASA Astrophysics Data System (ADS)

Bering, Edgar, III; Longmier, Benjamin; Glover, Tim; Chang-Diaz, Franklin; Squire, Jared; Brukardt, Michael

2008-11-01

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is a high power magnetoplasma rocket, capable of Isp/thrust modulation at constant power. The plasma is produced by a helicon discharge. The bulk of the energy is added by ion cyclotron resonance heating (ICRH.) Axial momentum is obtained by adiabatic expansion of the plasma in a magnetic nozzle. Thrust/specific impulse ratio control in the VASIMR is primarily achieved by the partitioning of the RF power to the helicon and ICRH systems, with the proper adjustment of the propellant flow. Ion dynamics in the exhaust were studied using probes, gridded energy analyzers (RPA's), microwave interferometry and optical techniques. Results are summarize from high power ICRH experiments performed on the VX-100 using argon plasma during 2007, and on the VX-200 using argon plasma during 2008. The VX-100 has demonstrated ICRH antenna efficiency >90% and a total coupling efficiency of ˜75%. The rocket performance parameters inferred by integrating the moments of the ion energy distribution corresponds to a thrust of 2 N at an exhaust velocity of 20 km/s with the VX-100 device. The new VX-200 machine is described.

Magnetic Field Tailored Annular Hall Thruster with Anode Layer

NASA Astrophysics Data System (ADS)

Lee, Seunghun; Kim, Holak; Kim, Junbum; Lim, Youbong; Choe, Wonho; Korea Institute of Materials Science Collaboration

2016-09-01

Plasma propulsion system is one of the key components for advanced missions of satellites as well as deep space exploration. A typical plasma propulsion system is Hall effect thruster that uses crossed electric and magnetic fields to ionize a propellant gas and to accelerate the ionized gas to generate momentum. In Hall thruster plasmas, magnetic field configuration is important due to the fact that electron confinement in the electromagnetic fields affects both plasma and ion beam characteristics as well as thruster performance parameters including thrust, specific impulse, power efficiency, and life time. In this work, development of an anode layer Hall thruster (TAL) with magnetic field tailoring has been attempted. The TAL is possible to keep discharge in 1 to 2 kilovolts of anode voltage, which is useful to obtain high specific impulse. The magnetic field tailoring is used to minimize undesirable heat dissipation and secondary electron emission from the wall surrounding the plasma. We will report 3 W and 200 W thrusters performances measured by a pendulum thrust stand according to the magnetic field configuration. Also, the measured result will be compared with the plasma diagnostics conducted by an angular Faraday probe, a retarding potential analyzer, and a ExB probe.

Study on the influences of ionization region material arrangement on Hall thruster channel discharge characteristics

NASA Astrophysics Data System (ADS)

Xiang, HU; Ping, DUAN; Jilei, SONG; Wenqing, LI; Long, CHEN; Xingyu, BIAN

2018-02-01

There exists strong interaction between the plasma and channel wall in the Hall thruster, which greatly affects the discharge performance of the thruster. In this paper, a two-dimensional physical model is established based on the actual size of an Aton P70 Hall thruster discharge channel. The particle-in-cell simulation method is applied to study the influences of segmented low emissive graphite electrode biased with anode voltage on the discharge characteristics of the Hall thruster channel. The influences of segmented electrode placed at the ionization region on electric potential, ion number density, electron temperature, ionization rate, discharge current and specific impulse are discussed. The results show that, when segmented electrode is placed at the ionization region, the axial length of the acceleration region is shortened, the equipotential lines tend to be vertical with wall at the acceleration region, thus radial velocity of ions is reduced along with the wall corrosion. The axial position of the maximal electron temperature moves towards the exit with the expansion of ionization region. Furthermore, the electron-wall collision frequency and ionization rate also increase, the discharge current decreases and the specific impulse of the Hall thruster is slightly enhanced.

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.

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

Characteristics of corona impulses from insulated wires subjected to high ac voltages

NASA Technical Reports Server (NTRS)

Doreswamy, C. V.; Crowell, C. S.

1976-01-01

Corona discharges arise due to ionization of air or gas subject to high electric fields. The free electrons and ions contained in these discharges interact with molecules of insulating materials, resulting in chemical changes and destroying the electrical insulating properties. The paper describes some results of measurements aimed at determining corona pulse waveforms, their repetition rate, and amplitude distribution during various randomly-sampled identical time periods of a 60-Hz high-voltage wave. Described are properties of positive and negative corona impulses generated from typical conductors at various test high voltages. A possible method for calculating the energies, densities, and electromagnetic interferences by making use of these results is suggested.

Study on the streamer inception characteristics under positive lightning impulse voltage

NASA Astrophysics Data System (ADS)

Wang, Zezhong; Geng, Yinan

2017-11-01

The streamer is the main process in an air gap discharge, and the inception characteristics of streamers have been widely applied in engineering. Streamer inception characteristics under DC voltage have been studied by many researchers, but the inception characteristics under impulse voltage, and particularly under lightning impulse voltage with a high voltage rise rate have rarely been studied. A measurement system based on integrated optoelectronic technology has been proposed in this paper, and the streamer inception characteristics in a 1-m-long rod-plane air gap that was energized by a positive lightning impulse voltage have been researched. We have also measured the streamer inception electric field using electrodes with different radii of curvature and different voltage rise rates. As a result, a modified empirical criterion for the streamer inception electric field that considers the voltage rise rate has been proposed, and the wide applicability of this criterion has been proved. Based on the streamer inception time-lag obtained, we determined that the field distribution obeys a Rayleigh distribution, which explains the change law of the streamer inception time-lag. The characteristic parameter of the Rayleigh distribution lies in the range from 0.6 to 2.5 when the radius of curvature of the electrode head is in the range from 0.5 cm to 2.5 cm and the voltage rise rate ranges from 80 kV/μs to 240kV/μs under positive lightning impulse voltage.

100-Lb(f) LO2/LCH4 Reaction Control Engine Technology Development for Future Space Vehicles

NASA Technical Reports Server (NTRS)

Robinson, Philip J.; Veith, Eric M.; Hurlbert, Eric A.; Jimenez, Rafael; Smith, Timothy D.

2008-01-01

The National Aeronautics and Space Administration (NASA) has identified liquid oxygen (LO2)/liquid methane (LCH4) propulsion systems as promising options for some future space vehicles. NASA issued a contract to Aerojet to develop a 100-lbf (445 N) LO2/LCH4 Reaction Control Engine (RCE) aimed at reducing the risk of utilizing a cryogenic reaction control system (RCS) on a space vehicle. Aerojet utilized innovative design solutions to develop an RCE that can ignite reliably over a broad range of inlet temperatures, perform short minimum impulse bits (MIB) at small electrical pulse widths (EPW), and produce excellent specific impulse (Isp) across a range of engine mixture ratios (MR). These design innovations also provide a start transient with a benign MR, ensuring good thrust chamber compatibility and long life. In addition, this RCE can successfully operate at MRs associated with main engines, enabling the RCE to provide emergency backup propulsion to minimize vehicle propellant load and overall system mass.

100-LBF LO2/LCH4 - Reaction Control Engine Technology Development for Future Space Vehicles

NASA Technical Reports Server (NTRS)

Robinson, Philip J.; Veith, Eric M.; Hurlbert, Eric A.; Jimenez, Rafael; Smith, Timothy D.

2008-01-01

The National Aeronautics and Space Administration (NASA) has identified liquid oxygen (LO2)/liquid methane (LCH4) propulsion systems as promising options for some future space vehicles. NASA issued a contract to Aerojet to develop a 100-lbf (445 N) LO2/LCH4 Reaction Control Engine (RCE) aimed at reducing the risk of utilizing a cryogenic reaction control system (RCS) on a space vehicle. Aerojet utilized innovative design solutions to develop an RCE that can ignite reliably over a broad range of inlet temperatures, perform short minimum impulse bits (MIB) at small electrical pulse widths (EPW), and produce excellent specific impulse (Isp) across a range of engine mixture ratios (MR). These design innovations also provide a start transient with a benign MR, ensuring good thrust chamber compatibility and long life. In addition, this RCE can successfully operate at MRs associated with main engines, enabling the RCE to provide emergency backup propulsion to minimize vehicle propellant load and overall system mass.

A theoretical and experimental investigation of the linear and nonlinear impulse responses from a magnetoplasma column

NASA Technical Reports Server (NTRS)

Grody, N. C.

1973-01-01

Linear and nonlinear responses of a magnetoplasma resulting from inhomogeneity in the background plasma density are studied. The plasma response to an impulse electric field was measured and the results are compared with the theory of an inhomogeneous cold plasma. Impulse responses were recorded for the different plasma densities, static magnetic fields, and neutral pressures and generally appeared as modulated, damped oscillations. The frequency spectra of the waveforms consisted of two separated resonance peaks. For weak excitation, the results correlate with the linear theory of a cold, inhomogeneous, cylindrical magnetoplasma. The damping mechanism is identified with that of phase mixing due to inhomogeneity in plasma density. With increasing excitation voltage, the nonlinear impulse responses display stronger damping and a small increase in the frequency of oscillation.

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

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.

High Voltage Discharge Profile on Soil Breakdown Using Impulse Discharge

NASA Astrophysics Data System (ADS)

Fajingbesi, F. E.; Midi, N. S.; Elsheikh, E. M. A.; Yusoff, S. H.

2017-06-01

Grounding terminals are mandatory in electrical appliance design as they provide safety route during overvoltage faults. The soil (earth) been the universal ground is assumed to be at zero electric potential. However, due to properties like moisture, pH and available nutrients; the electric potential may fluctuate between positive and negative values that could be harmful for internally connected circuits on the grounding terminal. Fluctuations in soil properties may also lead to current crowding effect similar to those seen at the emitters of semiconductor transistors. In this work, soil samples are subjected to high impulse voltage discharge and the breakdown characteristics was profiled. The results from profiling discharge characteristics of soil in this work will contribute to the optimization of grounding protection system design in terms of electrode placement. This would also contribute to avoiding grounding electrode current crowding, ground potential rise fault and electromagnetic coupling faults.

Electrical Manipulation of Spin Qubits in Li-doped Si

NASA Astrophysics Data System (ADS)

Petukhov, Andre; Pendo, Luke; Handberg, Erin; Smelyanskiy, Vadim

2011-03-01

We propose a complete quantum computing scheme based on Li donors in Si under external biaxial stress. The qubits are encoded on the ground state Zeeman doublets and coupled via long-range spin-spin interaction mediated by acoustic phonons. This interaction is unique for Li donors in Si due to their inverted electronic structure. Our scheme takes advantage of the fact that the energy level spacing in 1 s Li-donor manifold is comparable with the magnitude of the spin-orbit interaction. As a result the Li spin qubits can be placed 100 nm apart and manipulated by a combination of external electric field and microwave field impulses. We present a specially-designed sequence of the electric field impulses which allows for a typical time of a two-qubit gate ~ ~1~ μ s and a quality factor ~10-6 . These estimates are derived from detailed microscopic calculations of the quadratic Stark effect and electron-phonon decoherence times.

Integrated propulsion for near-Earth space missions. Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

Dailey, C. L.; Meissinger, H. F.; Lovberg, R. H.; Zafran, S.

1981-01-01

Tradeoffs between electric propulsion system mass ratio and transfer time from LEO to GEO were conducted parametrically for various thruster efficiency, specific impulse, and other propulsion parameters. A computer model was developed for performing orbit transfer calculations which included the effects of aerodynamic drag, radiation degradation, and occultation. The tradeoff results showed that thruster technology areas for integrated propulsion should be directed towards improving primary thruster efficiency in the range from 1500 to 2500 seconds, and be continued towards reducing specific mass. Comparison of auxiliary propulsion systems showed large total propellant mass savings with integrated electric auxiliary propulsion. Stationkeeping is the most demanding on orbit propulsion requirement. At area densities above 0.5 sq m/kg, East-West stationkeeping requirements from solar pressure exceed North-South stationkeeping requirements from gravitational forces. A solar array pointing strategy was developed to minimize the effects of atmospheric drag at low altitude, enabling electric propulsion to initiate orbit transfer at Shuttle's maximum cargo carrying altitude. Gravity gradient torques are used during ascent to sustain the spacecraft roll motion required for optimum solar array illumination. A near optimum cover glass thickness of 6 mils was established for LEO to GEO transfer.

Extending Ion Engine Technology to NEXT and Beyond

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.; Patterson, Michael J.; Foster, John E.; Rawlin, Vince K.; Soulas, George C.; Sovey, James S.; Kovaleski, Scott D.; Roman, Robert F.; Williams, George J., Jr.; Lyons, Valerie J. (Technical Monitor)

2002-01-01

Extending ion engine technology beyond the current state-of-the art primary interplanetary electric propulsion system, the 2.3-kW NASA Solar Electric Propulsion Technology and Applications Readiness (NSTAR) system, will require thrusters with improved propellant throughput and total impulse capability. Many of the design choices that culminated in the NSTAR thrusters must be revisited, and their application to next generation ion engine technology must be evaluated. The concept of derating, which was successfully employed in NSTAR, has been applied to the 40 cm NASA Evolutionary Xenon Thruster (NEXT) currently under development at NASA Glenn Research Center (GRC). At 5-kW, NEXT operates with the same average beam current density as NSTAR, and at 10-kW, the peak beam current density is only ten percent greater than NSTAR. The result is that similar Ion optics technology is expected to yield comparable lifetime. Thick-accelerator- grid ion optics are also being tested to realize additional lifetime benefits. A 40-A discharge cathode is being developed for NEXT based on scaling the NSTAR design. Nevertheless, the experiences of the NSTAR ground tests and the thruster on the Deep Space One spacecraft indicate that the discharge cathode wear must be studied experimentally and theoretically to ensure that it meets the lifetime requirements. Although NEXT is in its infancy, investigations have already begun to examine possible modifications to engine design for even higher-power and higher-specific impulse engines. Ion optics using alternate materials such as titanium, graphite, or carbon-carbon composite are currently being investigated due to their low sputter yields at high voltage. To avoid the difficulties encountered using electrodes at high-currents, the use of a microwave-based ion thruster is under investigation for potential high-power ion thruster systems requiring long lifetimes. Additionally, alternative propellants are being considered for applications requiring high-specific impulse (>> 5000 s) and extremely long-life (>> 15,000 hr). Testing requirements make condensable propellants attractive for high-power engines. Although the NSTAR ion engine demonstrated the flight maturity of ion thruster technology, many challenges remain for the development of thrusters with improved propellant throughput and power handling capabilities.

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.

Exhaust Plume Measurements of the VASIMR VX-200

NASA Astrophysics Data System (ADS)

Longmier, Benjamin; Bering, Edgar, III; Squire, Jared; Glover, Tim; Chang-Diaz, Franklin; Brukardt, Michael

2008-11-01

Recent progress is discussed in the development of an advanced RF electric propulsion concept: the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) VX-200 engine, a 200 kW flight-technology prototype. Results from high power Helicon only and Helicon with ICRH experiments are performed on the VX-200 using argon plasma. Recent measurements of axial plasma density and potential profiles, magnetic field-line shaping, charge exchange, and force measurements taken in the plume of the VX-200 exhaust are made within a new 125 cubic meter cryo-pumped vacuum chamber and are presented in the context of RF plasma thruster physics.

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 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.

Prediction of fundamental properties of ionic liquid electrospray thrusters using molecular dynamics.

PubMed

Borner, Arnaud; Li, Zheng; Levin, Deborah A

2013-06-06

Molecular dynamics (MD) simulations are performed to model an electrospray thruster for the ionic liquid (IL) EMIM-BF4 using two coarse-grained (CG) potentials. Different equilibrium properties were obtained for the two potentials and then both were used to study the electrical extrusion of the IL for different electric field strengths and mass flow rates. The MD simulations provide the first insight into the atomistic modeling of a capillary-tip-extractor system, the basic elements of an electrospray thruster. One of the CG potentials was found to predict the formation of the Taylor cone, the cone-jet, and other extrusion modes for similar electric fields and mass flow rates observed in experiments of a IL fed capillary-tip-extractor system. Current distributions and anion and cation behavior were characterized and estimates of thrust and specific impulse are presented and compare reasonably well with measurements. Moreover, the role of inhomogeneities in the electric field as well as that of the IL space-charge most likely will improve agreement between modeling and experiment.

Electric Propulsion Space Experiment (ESEX): Spacecraft design issues for high-power electric propulsion

NASA Astrophysics Data System (ADS)

Kriebel, Mary M.; Sanks, Terry M.

1992-02-01

Electric propulsion provides high specific impulses, and low thrust when compared to chemical propulsion systems. Therefore, electric propulsion offers improvements over chemical systems such as increased station-keeping time, prolonged on-orbit maneuverability, low acceleration of large structures, and increased launch vehicle flexibility. The anticipated near-term operational electric propulsion system for an electric orbit transfer vehicle is an arcjet propulsion system. Towards this end, the USAF's Phillips Laboratory (PL) has awarded a prime contract to TRW Space & Technology Group to design, build, and space qualify a 30-kWe class arcjet as well as develop and demonstrate, on the ground, a flight-qualified arcjet propulsion flight unit. The name of this effort is the 30 kWe Class Arcjet Advanced Technology Transition Demonstration (Arcjet ATTD) program. Once the flight unit has completed its ground qualification test, it will be given to the Space Test and Transportation Program Office of the Air Force's Space Systems Division (ST/T) for launch vehicle integration and space test. The flight unit's space test is known as the Electric Propulsion Space Experiment (ESEX). ESEX's mission scenario is 10 firings of 15 minutes each. The objectives of the ESEX flight are to measure arcjet plume deposition, electromagnetic interference, thermal radiation, and acceleration in space. Plume deposition, electromagnetic interference, and thermal radiation are operational issues that are primarily being answered for operational use. This paper describes the Arcjet ATTD flight unit design and identifies specifically how the diagnostic data will be collected as part of the ESEX program.

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.

Status of a Power Processor for the Prometheus-1 Electric Propulsion System

NASA Technical Reports Server (NTRS)

Pinero, Luis R.; Hill, Gerald M.; Aulisio, Michael; Gerber, Scott; Griebeler, Elmer; Hewitt, Frank; Scina, Joseph

2006-01-01

NASA is developing technologies for nuclear electric propulsion for proposed deep space missions in support of the Exploration initiative under Project Prometheus. Electrical power produced by the combination of a fission-based power source and a Brayton power conversion and distribution system is used by a high specific impulse ion propulsion system to propel the spaceship. The ion propulsion system include the thruster, power processor and propellant feed system. A power processor technology development effort was initiated under Project Prometheus to develop high performance and lightweight power-processing technologies suitable for the application. This effort faces multiple challenges including developing radiation hardened power modules and converters with very high power capability and efficiency to minimize the impact on the power conversion and distribution system as well as the heat rejection system. This paper documents the design and test results of the first version of the beam supply, the design of a second version of the beam supply and the design and test results of the ancillary supplies.

The NASA GSFC MEMS Colloidal Thruster

NASA Technical Reports Server (NTRS)

Cardiff, Eric H.; Jamieson, Brian G.; Norgaard, Peter C.; Chepko, Ariane B.

2004-01-01

A number of upcoming missions require different thrust levels on the same spacecraft. A highly scaleable and efficient propulsion system would allow substantial mass savings. One type of thruster that can throttle from high to low thrust while maintaining a high specific impulse is a Micro-Electro-Mechanical System (MEMS) colloidal thruster. The NASA GSFC MEMS colloidal thruster has solved the problem of electrical breakdown to permit the integration of the electrode on top of the emitter by a novel MEMS fabrication technique. Devices have been successfully fabricated and the insulation properties have been tested to show they can support the required electric field. A computational finite element model was created and used to verify the voltage required to successfully operate the thruster. An experimental setup has been prepared to test the devices with both optical and Time-Of-Flight diagnostics.

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

Permanent magnetic field, direct electric field, and infrared to reduce blood glucose level and hepatic function in mus musculus with diabetic mellitus

NASA Astrophysics Data System (ADS)

Suhariningsih; Basuki Notobroto, Hari; Winarni, Dwi; Achmad Hussein, Saikhu; Anggono Prijo, Tri

2017-05-01

Blood contains several electrolytes with positive (cation) and negative (anion) ion load. Both electrolytes deliver impulse synergistically adjusting body needs. Those electrolytes give specific effect to external disturbance such as electric, magnetic, even infrared field. A study has been conducted to reduce blood glucose level and liver function, in type 2 Diabetes Mellitus patients, using Biophysics concept which uses combination therapy of permanent magnetic field, electric field, and infrared. This study used 48 healthy mice (mus musculus), male, age 3-4 weeks, with approximately 25-30 g in weight. Mice was fed with lard as high fat diet orally, before Streptozotocin (STZ) induction become diabetic mice. Therapy was conducted by putting mice in a chamber that emits the combination of permanent magnetic field, electric field, and infrared, every day for 1 hour for 28 days. There were 4 combinations of therapy/treatment, namely: (1) permanent magnetic field, direct electric field, and infrared; (2) permanent magnetic field, direct electric field, without infrared; (3) permanent magnetic field, alternating electric field, and infrared; and (4) permanent magnetic field, alternating electric field, without infrared. The results of therapy show that every combination is able to reduce blood glucose level, AST, and ALT. However, the best result is by using combination of permanent magnetic field, direct electric field, and infrared.

Lightning Impulse Breakdown Characteristics and Electrodynamic Process of Insulating Vegetable Oil-Based Nanofluid

NASA Astrophysics Data System (ADS)

Li, Jian; Zhang, Zhao-Tao; Zou, Ping; Du, Bin; Liao, Rui-Jin

2012-06-01

Insulating vegetable oils are considered environment-friendly and fire-resistant substitutes for insulating mineral oils. This paper presents the lightning impulse breakdown characteristic of insulating vegetable oil and insulating vegetable oil-based nanofluids. It indicates that Fe3O4 nanoparticles can increase the negative lightning impulse breakdown voltages of insulating vegetable oil by 11.8% and positive lightning impulse breakdown voltages by 37.4%. The propagation velocity of streamer is reduced by the presence of nanoparticles. The propagation velocities of streamer to positive and negative lightning impulse breakdown in the insulating vegetable oil-based nanofluids are 21.2% and 14.4% lesser than those in insulating vegetable oils, respectively. The higher electrical breakdown strength and lower streamer velocity is explained by the charging dynamics of nanoparticles in insulating vegetable oil. Space charge build-up and space charge distorted filed in point-sphere gap is also described. The field strength is reduced at the streamer tip due to the low mobility of negative nanoparticles.

Compulsory DNA Sampling of Service Members for Inclusion in the DOD DNA Registry: Remains Identification With a Risk

DTIC Science & Technology

1996-04-01

for Tay-Sachs disease, cystic fibrosis, Huntingtons disease, Duchenne muscular dystrophy , 26alcoholism, and susceptibility to certain types of cancer...and an increased risk of infection and injury to muscle , nerves, and blood vessels was sufficiently compelling to outweigh the state’s interest in...them into electrical impulses. These surgically implanted devices could produce electronic impulses to induce paralyzed muscles to contract and

Multi-User Performance Issues in Wireless Impulse Radio Networks

DTIC Science & Technology

2004-01-01

Performance Issues in Wireless Impulse Radio Networks 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR( S ) 5d. PROJECT...NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME( S ) AND ADDRESS(ES) North Carolina State University,Department of...Electrical and Computer Engineering,Raleigh,NC,27695 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME( S ) AND ADDRESS(ES) 10

Conducted electrical weapons or stun guns: a review of 46 cases examined in casualty.

PubMed

Becour, Bertrand

2013-06-01

Low-lethality weapons are intended to neutralize a person with maximum security and with minimal risk of injury or death to the user of the weapon, the person arrested, and the witnesses. Under the same circumstances, the use of a firearm is causing mortality of 50%. Marketed since 1974, the Taser X26 is currently staffing services in the French police and gendarmerie. The Taser device has 3 damaging mechanisms: the direct effect of electric current on the tissues, the conversion of electrical energy into thermal energy, and the injuries caused by the general muscle contraction and resulting fall. The study aimed to analyze the specificities of the conducted electrical weapon-related injuries treated in a emergency department on a series of 46 cases. The study population was predominantly middle-aged men. The circumstances of use of the Taser X26 were most often related to an arrest. The frequency of consultation after a shot by Taser X26 was stable. The management is essentially an outpatient because of frequent and benign lesions. The impacts of electrical impulse mainly affect the chest and abdomen. This distribution of impact zones is inhomogeneous, depending on the circumstances of use.

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)

A Flight Demonstration of Plasma Rocket Propulsion

NASA Technical Reports Server (NTRS)

Petro, Andrew; Chang-Diaz, Franklin; Schwenterly, WIlliam; Hitt, Michael; Lepore, Joseph

2000-01-01

The Advanced Space Propulsion Laboratory at the NASA Johnson Space Center has been engaged in the development of a variable specific impulse magnetoplasma rocket (V ASIMR) for several years. This type of rocket could be used in the future to propel interplanetary spacecraft and has the potential to open the entire solar system to human exploration. One feature of this propulsion technology is the ability to vary its specific impulse so that it can be operated in a mode that maximizes propellant efficiency or a mode that maximizes thrust. Variation of specific impulse and thrust enhances the ability to optimize interplanetary trajectories and results in shorter trip times and lower propellant requirements than with a fixed specific impulse. In its ultimate application for interplanetary travel, the VASIMR would be a multi-megawatt device. A much lower power system is being designed for demonstration in the 2004 timeframe. This first space demonstration would employ a lO-kilowatt thruster aboard a solar powered spacecraft in Earth orbit. The 1O-kilowatt V ASIMR demonstration unit would operate for a period of several months with hydrogen or deuterium propellant with a specific impulse of 10,000 seconds.

Stationary plasma thruster evaluation in Russia

NASA Technical Reports Server (NTRS)

Brophy, John R.

1992-01-01

A team of electric propulsion specialists from U.S. government laboratories experimentally evaluated the performance of a 1.35-kW Stationary Plasma Thruster (SPT) at the Scientific Research Institute of Thermal Processes in Moscow and at 'Fakel' Enterprise in Kaliningrad, Russia. The evaluation was performed using a combination of U.S. and Russian instrumentation and indicated that the actual performance of the thruster appears to be close to the claimed performance. The claimed performance was a specific impulse of 16,000 m/s, an overall efficiency of 50 percent, and an input power of 1.35 kW, and is superior to the performance of western electric thrusters at this specific impulse. The unique performance capabilities of the stationary plasma thruster, along with claims that more than fifty of the 660-W thrusters have been flown in space on Russian spacecraft, attracted the interest of western spacecraft propulsion specialists. A two-phase program was initiated to evaluate the stationary plasma thruster performance and technology. The first phase of this program, to experimentally evaluate the performance of the thruster with U.S. instrumentation in Russia, is described in this report. The second phase objective is to determine the suitability of the stationary plasma thruster technology for use on western spacecraft. This will be accomplished by bringing stationary plasma thrusters to the U.S. for quantification of thruster erosion rates, measurements of the performance variation as a function of long-duration operation, quantification of the exhaust beam divergence angle, and determination of the non-propellant efflux from the thruster. These issues require quantification in order to maximize the probability for user application of the SPT technology and significantly increase the propulsion capabilities of U.S. spacecraft.

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

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.

Influence of High-Current-Density Impulses on the Compression Behavior: Experiments with Iron and a Nickel-Based Alloy

NASA Astrophysics Data System (ADS)

Demler, E.; Gerstein, G.; Dalinger, A.; Epishin, A.; Rodman, D.; Nürnberger, F.

2017-01-01

Difficulties of processing of high strength and/or brittle materials by plastic deformation, e.g., by forging, require to develop new industrial technologies. In particular, the feasible deformation rates are limited for low-ductile metallic materials. For this reason, processes were investigated to improve the deformability in which electrical impulses are to be applied to lower the yield strength. However, owing to the impulse duration and low current densities, concomitant effects always occur, e.g., as a result of Joule heating. Current developments in power electronics allow now to transmit high currents as short pulses. By reducing the impulse duration and increasing the current density, the plasticity of metallic materials can be correspondingly increased. Using the examples of polycrystalline iron and a single-crystal, nickel-based alloy (PWA 1480), current advances in the development of methods for forming materials by means of high-current-density impulses are demonstrated. For this purpose, appropriate specimens were loaded in compression and, using novel testing equipment, subjected to a current strength of 10 kA with an impulse duration of 2 ms. For a pre-defined strain, the test results show a significant decrease in the compressive stress during the compression test and a significant change in the dislocation distribution following the current impulse treatment.

Response of a grounded dielectric slab to an impulse line source using leaky modes

NASA Technical Reports Server (NTRS)

Duffy, Dean G.

1994-01-01

This paper describes how expansions in leaky (or improper) modes may be used to represent the continuous spectrum in an open radiating waveguide. The technique requires a thorough knowledge of the life history of the improper modes as they migrate from improper to proper Riemann surfaces. The method is illustrated by finding the electric field resulting from an impulsively forced current located in the free space above a grounded dielectric slab.

Applied-field MPD thruster geometry effects

NASA Technical Reports Server (NTRS)

Myers, Roger M.

1991-01-01

Eight MPD thruster configurations were used to study the effects of applied field strength, propellant, and facility pressure on thruster performance. Vacuum facility background pressures higher than approx. 0.12 Pa were found to greatly influence thruster performance and electrode power deposition. Thrust efficiency and specific impulse increased monotonically with increasing applied field strength. Both cathode and anode radii fundamentally influenced the efficiency specific impulse relationship, while their lengths influence only the magnitude of the applied magnetic field required to reach a given performance level. At a given specific impulse, large electrode radii result in lower efficiencies for the operating conditions studied. For all test conditions, anode power deposition was the largest efficiency loss, and represented between 50 and 80 pct. of the input power. The fraction of the input power deposited into the anode decreased with increasing applied field and anode radii. The highest performance measured, 20 pct. efficiency at 3700 seconds specific impulse, was obtained using hydrogen propellant.

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.

Pulsed Electric Propulsion Thrust Stand Calibration Method

NASA Technical Reports Server (NTRS)

Wong, Andrea R.; Polzin, Kurt A.; Pearson, J. Boise

2011-01-01

The evaluation of the performance of any propulsion device requires the accurate measurement of thrust. While chemical rocket thrust is typically measured using a load cell, the low thrust levels associated with electric propulsion (EP) systems necessitate the use of much more sensitive measurement techniques. The design and development of electric propulsion thrust stands that employ a conventional hanging pendulum arm connected to a balance mechanism consisting of a secondary arm and variable linkage have been reported in recent publications by Polzin et al. These works focused on performing steady-state thrust measurements and employed a static analysis of the thrust stand response. In the present work, we present a calibration method and data that will permit pulsed thrust measurements using the Variable Amplitude Hanging Pendulum with Extended Range (VAHPER) thrust stand. Pulsed thrust measurements are challenging in general because the pulsed thrust (impulse bit) occurs over a short timescale (typically 1 micros to 1 millisecond) and cannot be resolved directly. Consequently, the imparted impulse bit must be inferred through observation of the change in thrust stand motion effected by the pulse. Pulsed thrust measurements have typically only consisted of single-shot operation. In the present work, we discuss repetition-rate pulsed thruster operation and describe a method to perform these measurements. The thrust stand response can be modeled as a spring-mass-damper system with a repetitive delta forcing function to represent the impulsive action of the thruster.

An Overview of Electric Propulsion Activities at NASA

NASA Technical Reports Server (NTRS)

Dunning, John W., Jr.; Hamley, John A.; Jankovsky, Robert S.; Oleson, Steven R.

2004-01-01

This paper provides an overview of NASA s activities in the area of electric propulsion with an emphasis on project directions, recent progress, and a view of future project directions. The goals of the electric propulsion programs are to develop key technologies to enable new and ambitious science missions and to transfer these technologies to industry. Activities include the development of gridded ion thruster technology, Hall thruster technology, pulsed plasma thruster technology, and very high power electric propulsion technology, as well as systems technology that supports practical implementation of these advanced concepts. The performance of clusters of ion and Hall thrusters is being revisited. Mission analyses, based on science requirements and preliminary mission specifications, guide the technology projects and introduce mission planners to new capabilities. Significant in-house activity, with strong industrial/academia participation via contracts and grants, is maintained to address these development efforts. NASA has initiated a program covering nuclear powered spacecraft that includes both reactor and radioisotope power sources. This has provided an impetus to investigate higher power and higher specific impulse thruster systems. NASA continues to work closely with both supplier and user communities to maximize the understanding and acceptance of new technology in a timely and cost-effective manner. NASA s electric propulsion efforts are closely coordinated with Department of Defense and other national programs to assure the most effective use of available resources. Several NASA Centers are actively involved in these electric propulsion activities, including, the Glenn Research Center, Jet Propulsion Laboratory, Johnson Space Center, and Marshall Space Flight Center.

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.

A Pulsed Plasma Thruster Using Dimethyl Ether as Propellant

NASA Astrophysics Data System (ADS)

Masui, Souichi; Okada, Terumasa; Kitatomi, Makoto; Kakami, Akira; Tachibana, Takeshi

The pulsed plasma thruster (PPT), has attracted attention again as a micro-thruster because of its compactness, light weight, and comparatively low power consumption. On the other hand, the propellant utilization efficiency of a conventinal Teflon PPT is relatively low among electric propulsion devices because a propellant that originates from late-time ablation produces negligible thrust. The liquid propellant PPT (LP-PPT), in which water or ethanol is fed with an injector, was proposed to overcome these difficulties. Thrust measurements show that a LP-PPT provides higher specific impulses than a conventional PPT. However, water requires temperature management for propellant storage due to its relatively high freezing point. Moreover, even if ethanol, which has a sufficiently low freezing point, is used as propellant, a pressurant is necessary, as well as water, because the vapor pressures are insufficient for self-pressurization. In this study, we propose to use dimethyl ether (DME) as the propellant. DME, which has a freezing point of 131 K at 1 atm and a vapor pressure of 6 atm at 298 K, can be stored in tanks as a liquid, and requires no feeding pressurant. We designed a DME pulsed plasma thruster to evaluate performance. Thrust measurement yielded a specific impulse of 430 s for a coaxial type at a capacitor-stored energy of 13 J.

Changes in metal properties after thermal and electric impulse processing

NASA Astrophysics Data System (ADS)

Shaburova, N. A.

2015-04-01

The results of the experiments on processing metal melts by powerful electromagnetic impulses are given. The generator used in the experiments has the following characteristics: pulse height - 10KV, duration - 1ns, leading edge - 0.1ns, repetition rate - 1KHz, the output - 100KWt. The duration of the processing is 10-15min. The comparative analysis of the processed and unprocessed samples results in the changes of structure, increase of density, solidity, plasticity and resilience of cast metal. The result analysis of different external physical processing methods on alloys shows full agreement with the results of the ultrasonic processing of metals. The hypothesis of ultrasonic shock wave formation at the pulse front was adopted as the main mechanism of the electromagnetic impulse impact on alloys. The theoretical part of the research describes the transformation process of electromagnetic impulses into acoustic ones.

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

Response of ionospheric electric fields at mid-low latitudes during sudden commencements

NASA Astrophysics Data System (ADS)

Takahashi, N.; Kasaba, Y.; Shinbori, A.; Nishimura, Y.; Kikuchi, T.; Ebihara, Y.; Nagatsuma, T.

2015-06-01

Using in situ observations from the Republic of China Satellite-1 spacecraft, we investigated the time response and local time dependence of the ionospheric electric field at mid-low latitudes associated with geomagnetic sudden commencements (SCs) that occurred from 1999 to 2004. We found that the ionospheric electric field variation associated with SCs instantaneously responds to the preliminary impulse (PI) signature on the ground regardless of spacecraft local time. Our statistical analysis also supports the global instant transmission of electric field from the polar region. In contrast, the peak time detected in the ionospheric electric field is earlier than that of the equatorial geomagnetic field (~20 s before in the PI phase). Based on the ground-ionosphere waveguide model, this time lag can be attributed to the latitudinal difference of ionospheric conductivity. However, the local time distribution of the initial excursion of ionospheric electric field shows that dusk-to-dawn ionospheric electric fields develop during the PI phase. Moreover, the westward electric field in the ionosphere, which produces the preliminary reverse impulse of the geomagnetic field on the dayside feature, appears at 18-22 h LT where the ionospheric conductivity beyond the duskside terminator (18 h LT) is lower than on the dayside. The result of a magnetohydrodynamic simulation for an ideal SC shows that the electric potential distribution is asymmetric with respect to the noon-midnight meridian. This produces the local time distribution of ionospheric electric fields similar to the observed result, which can be explained by the divergence of the Hall current under nonuniform ionospheric conductivity.

The Video Head Impulse Test to Assess the Efficacy of Vestibular Implants in Humans

PubMed Central

Guinand, Nils; Van de Berg, Raymond; Cavuscens, Samuel; Ranieri, Maurizio; Schneider, Erich; Lucieer, Floor; Kingma, Herman; Guyot, Jean-Philippe; Pérez Fornos, Angélica

2017-01-01

The purpose of this study was to evaluate whether it is possible to restore the high-frequency angular vestibulo-ocular reflex (aVOR) in patients suffering from a severe bilateral vestibulopathy (BV) and implanted with a vestibular implant prototype. Three patients (S1–3) participated in the study. They received a prototype vestibular implant with one to three electrode branches implanted in the proximity of the ampullary branches of the vestibular nerve. Five electrodes were available for electrical stimulation: one implanted in proximity of the left posterior ampullary nerve in S1, one in the left lateral and another one in the superior ampullary nerves in S2, and one in the right lateral and another one in the superior ampullary nerves in S3. The high-frequency aVOR was assessed using the video head impulse test (EyeSeeCam; EyeSeeTec, Munich, Germany), while motion-modulated electrical stimulation was delivered via one of the implanted vestibular electrodes at a time. aVOR gains were compared to control measurements obtained in the same patients when the device was not activated. In three out of the five tested electrodes the aVOR gain increased monotonically with increased stimulation strength when head impulses were delivered in the plane of the implanted canal. In these cases, gains ranging from 0.4 to values above 1 were measured. A “reversed” aVOR could also be generated when inversed stimulation paradigms were used. In most cases, the gain for excitatory head impulses was superior to that recorded for inhibitory head impulses, consistent with unilateral vestibular stimulation. Improvements of aVOR gain were generally accompanied by a concomitant decrease of corrective saccades, providing additional evidence of an effective aVOR. High inter-electrode and inter-subject variability were observed. These results, together with previous research, demonstrate that it is possible to restore the aVOR in a broad frequency range using motion-modulated electrical stimulation of the vestibular afferents. This provides additional encouraging evidence of the possibility of achieving a useful rehabilitation alternative for patients with BV in the near future. PMID:29184530

Numerical analysis of real gas MHD flow on two-dimensional self-field MPD thrusters

NASA Astrophysics Data System (ADS)

Xisto, Carlos M.; Páscoa, José C.; Oliveira, Paulo J.

2015-07-01

A self-field magnetoplasmadynamic (MPD) thruster is a low-thrust electric propulsion space-system that enables the usage of magnetohydrodynamic (MHD) principles for accelerating a plasma flow towards high speed exhaust velocities. It can produce an high specific impulse, making it suitable for long duration interplanetary space missions. In this paper numerical results obtained with a new code, which is being developed at C-MAST (Centre for Mechanical and Aerospace Technologies), for a two-dimensional self-field MPD thruster are presented. The numerical model is based on the macroscopic MHD equations for compressible and electrically resistive flow and is able to predict the two most important thrust mechanisms that are associated with this kind of propulsion system, namely the thermal thrust and the electromagnetic thrust. Moreover, due to the range of very high temperatures that could occur during the operation of the MPD, it also includes a real gas model for argon.

Development of medical electronic devices in the APL space department

NASA Technical Reports Server (NTRS)

Newman, A. L.

1985-01-01

Several electronic devices for automatically correcting specific defects in a body's physiologic regulation and allowing approximately normal functioning are described. A self-injurious behavior inhibiting system (SIBIS) is fastened to the arm of a person with chronic self-injurious behavior patterns. An electric shock is delivered into the arm whenever the device senses above-threshold acceleration of the head such as occur with head-bangers. Sounding a buzzer tone with the shock eventually allows transference of the aversive stimulus to the buzzer so shocks are no longer necessary. A programmable implantable medication system features a solenoid pump placed beneath the skin and refueled by hypodermic needle. The pump functions are programmable and can deliver insulin, chemotherapy mixes and/or pain killers according to a preset schedule or on patient demand. Finally, an automatic implantible defibrillator has four electrodes attached directly to the heart for sensing electrical impulses or emitting them in response to cardiac fibrillation.

Compact Plasma Accelerator for Micropropulsion Applications

NASA Technical Reports Server (NTRS)

Foster, John E.

2001-01-01

There is a need for a low power, light-weight (compact), high specific impulse electric propulsion device to satisfy mission requirements for microsatellite (1 to 20 kg) class missions. Satisfying these requirements entails addressing the general problem of generating a sufficiently dense plasma within a relatively small volume and then accelerating it. In the work presented here, the feasibility of utilizing a magnetic cusp to generate a dense plasma over small length scales of order 1 mm is investigated. This approach could potentially mitigate scaling issues associated with conventional ion thruster plasma containment schemes. Plume and discharge characteristics were documented using a Faraday probe and a retarding potential analyzer.

Boeing Low-Thrust Geosynchronous Transfer Mission Experience

NASA Technical Reports Server (NTRS)

Poole, Mark; Ho, Monte

2007-01-01

Since 2000, Boeing 702 satellites have used electric propulsion for transfer to geostationary orbits. The use of the 25cm Xenon Ion Propulsion System (25cm XIPS) results in more than a tenfold increase in specific impulse with the corresponding decrease in propellant mass needed to complete the mission when compared to chemical propulsion[1]. In addition to more favorable mass properties, with the use of XIPS, the 702 has been able to achieve orbit insertions with higher accuracy than it would have been possible with the use of chemical thrusters. This paper describes the experience attained by using the 702 XIPS ascent strategy to transfer satellite to geosynchronous orbits.

Affordable Development of a Nuclear Cryogenic Propulsion Stage

NASA Technical Reports Server (NTRS)

Houts, M. G.; Borowski, S. K.; George, J. A.; Kim, T.; Emrich, W. J.; Hickman, R. R.; Broadway, J. W.; Gerrish, H. P.; Adams, R. B.

2012-01-01

The fundamental capability of Nuclear Thermal Propulsion (NTP) is game changing for space exploration. A first generation Nuclear Cryogenic Propulsion Stage (NCPS) based on NTP could provide high thrust at a specific impulse above 900 s, roughly double that of state of the art chemical engines. The foundation provided by development and utilization of a NCPS could enable development of extremely high performance systems. The role of the NCPS in the development of advanced nuclear propulsion systems could be analogous to the role of the DC-3 in the development of advanced aviation. Progress made under the NCPS project could help enable both advanced NTP and advanced Nuclear Electric Propulsion (NEP).

NASA's Nuclear Thermal Propulsion Project

NASA Technical Reports Server (NTRS)

Houts, Michael G.; Mitchell, Doyce P.; Kim, Tony; Emrich, William J.; Hickman, Robert R.; Gerrish, Harold P.; Doughty, Glen; Belvin, Anthony; Clement, Steven; Borowski, Stanley K.;

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.

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

Microwave emission from lead zirconate titanate induced by impulsive mechanical load

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

Aman, A., E-mail: alexander.aman@ovgu.de; Packaging Group, Institute of Micro- and Sensorsytems, Otto-von-Guericke University, Universitätsplatz 2, 39106 Magdeburg; Majcherek, S.

2015-10-28

This paper focuses on microwave emission from Lead zirconate titanate Pb [Zr{sub x}Ti{sub 1−x}] O{sub 3} (PZT) induced by mechanical stressing. The mechanical stress was initiated by impact of a sharp tungsten indenter on the upper surface of PZT ceramic. The sequences of microwave and current impulses, which flew from indenter to electric ground, were detected simultaneously. The voltage between the upper and lower surface of ceramic was measured to obtain the behavior of mechanical force acting on ceramic during the impact. It was found that the amplitude, form, and frequency of measured microwave impulses were different by compression andmore » restitution phase of impact. Two different mechanisms of electron emission, responsible for microwave impulse generation, were proposed based on the dissimilar impulse behavior. The field emission from tungsten indenter is dominant during compression, whereas ferroemission dominates during restitution phase. Indeed, it was observed that the direction of the current flow, i.e., sign of current impulses is changed by transitions from compression to restitution phase of impact. The observed dissimilar behavior of microwave impulses, caused by increasing and decreasing applied force, can be used to calculate the contact time and behavior of mechanical force during mechanical impact on ceramic surface. It is shown that the generation of microwave impulses exhibits high reproducibility, impulse intensity, a low damping factor, and high mechanical failure resistance. Based on these microwave emission properties of PZT, the development of new type of stress sensor with spatial resolution of few microns becomes possible.« less

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

21 CFR 888.1240 - AC-powered dynamometer.

Code of Federal Regulations, 2011 CFR

2011-04-01

... neuromuscular function or degree of neuromuscular blockage by measuring, with a force transducer (a device that translates force into electrical impulses), the grip-strength of a patient's hand. (b) Classification. Class...

21 CFR 888.1240 - AC-powered dynamometer.

Code of Federal Regulations, 2010 CFR

2010-04-01

... neuromuscular function or degree of neuromuscular blockage by measuring, with a force transducer (a device that translates force into electrical impulses), the grip-strength of a patient's hand. (b) Classification. Class...

Retina

MedlinePlus Videos and Cool Tools

... light enters the eye, it strikes the receptor cells of the retina called the rods and cones. A chemical reaction results in the formation of electric impulses, which then travel to the brain through the optic nerve.

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).

Atmospheric Mining in the Outer Solar System: Outer Planet Orbital Transfer and Lander Analyses

NASA Technical Reports Server (NTRS)

Palaszewski, Bryan

2016-01-01

High energy propellants for human lunar missions are analyzed, focusing on very advanced ozone and atomic hydrogen. One of the most advanced launch vehicle propulsion systems, such as the Space Shuttle Main Engine (SSME), used hydrogen and oxygen and had a delivered specific impulse of 453 seconds. In the early days of the space program, other propellants (or so called metapropellants) were suggested, including atomic hydrogen and liquid ozone. Theoretical and experimental studies of atomic hydrogen and ozone were conducted beginning in the late 1940s. This propellant research may have provided screenwriters with the idea of an atomic hydrogen-ozone rocket engine in the 1950 movie, Rocketship X-M. This paper presents analyses showing that an atomic hydrogen-ozone rocket engine could produce a specific impulse over a wide range of specific impulse values reaching as high as 1,600 seconds. A series of single stage and multistage rocket vehicle analyses were conducted to find the minimum specific impulse needed to conduct high energy round trip lunar missions.

Propulsion Estimates for High Energy Lunar Missions Using Future Propellants

NASA Technical Reports Server (NTRS)

Palaszewski, Bryan A.; Bennett, Gary L.

2016-01-01

High energy propellants for human lunar missions are analyzed, focusing on very advanced ozone and atomic hydrogen. One of the most advanced launch vehicle propulsion systems, such as the Space Shuttle Main Engine (SSME), used hydrogen and oxygen and had a delivered specific impulse of 453 seconds. In the early days of the space program, other propellants (or so called metapropellants) were suggested, including atomic hydrogen and liquid ozone. Theoretical and experimental studies of atomic hydrogen and ozone were conducted beginning in the late 1940s. This propellant research may have provided screenwriters with the idea of an atomic hydrogen-ozone rocket engine in the 1950 movie, Rocketship X-M. This paper presents analyses showing that an atomic hydrogen-ozone rocket engine could produce a specific impulse over a wide range of specific impulse values reaching as high as 1,600 s. A series of single stage and multistage rocket vehicle analyses were conducted to find the minimum specific impulse needed to conduct high energy round trip lunar missions.

Influence of electrical boundary conditions on molecular dynamics simulations of ionic liquid electrosprays.

PubMed

Borner, Arnaud; Wang, Pengxiang; Levin, Deborah A

2014-12-01

Molecular dynamics (MD) simulations are coupled to solutions of Poisson's equation to study the effects of the electrical boundary conditions on the emission modes of an electrospray thruster fed with an ionic liquid. A comparison of a new tip boundary condition with an analytical model based on a semihyperboloidal shape offers good agreement, although the analytical model overestimates the maximum value of the tangential electric field since it does not take into account the space charge that reduces the field at the liquid surface. It is found that a constant electric field model gives similar agreement to the more rigorous and computationally expensive tip boundary condition at lower flow rates. However, at higher mass flow rates the constant electric field produces extruded particles with higher Coulomb energy per ion, consistent with droplet formation. Furthermore, the MD simulations show that ion emission sites differ based on the boundary condition and snapshots offer an explanation as to why some boundary condition models will predict emission in a purely ionic mode, whereas others suggest a mixed ion-droplet regime. Finally, specific impulses and thrusts are compared for the different models and are found to vary up to 30% due to differences in the average charge to mass ratio.

Design Considerations for Clean QED Fusion Propulsion Systems

NASA Astrophysics Data System (ADS)

Bussard, Robert W.; Jameson, Lorin W.

1994-07-01

The direct production of electric power appears possible from fusion reactions between fuels whose products consist solely of charged particles and thus do not present radiation hazards from energetic neutron production, as do reactions involving deuteron-bearing fuels. Among these are the fuels p, 11B, 3He, and 6Li. All of these can be ``burned'' in inertial-electrostatic-fusion (IEF) devices to power QED fusion-electric rocket engines. These IEF sources provide direct-converted electrical power at high voltage (MeV) to drive e-beams for efficient propellant heating to extreme temperatures, with resulting high specific impulse performance capabilities. IEF/QED engine systems using p11B can outperform all other advanced concepts for controlled fusion propulsion by 2-3 orders of magnitude, while 6Li6Li fusion yields one order of magnitude less advance. Either of these fusion rocket propulsion systems can provide very rapid transit for solar system missions, with high payload fractions in single-stage vehicles. The 3He3He reaction can not be used practically for direct electric conversion because of the wide spread in energy of its fusion products. However, it may eventually prove useful for thermal/electrical power generation in central station power plants, or for direct-fusion-product (DFP) propellant heatingin advanced deep-space rocket engines.

Influence of electrical boundary conditions on molecular dynamics simulations of ionic liquid electrosprays

NASA Astrophysics Data System (ADS)

Borner, Arnaud; Wang, Pengxiang; Levin, Deborah A.

2014-12-01

Molecular dynamics (MD) simulations are coupled to solutions of Poisson's equation to study the effects of the electrical boundary conditions on the emission modes of an electrospray thruster fed with an ionic liquid. A comparison of a new tip boundary condition with an analytical model based on a semihyperboloidal shape offers good agreement, although the analytical model overestimates the maximum value of the tangential electric field since it does not take into account the space charge that reduces the field at the liquid surface. It is found that a constant electric field model gives similar agreement to the more rigorous and computationally expensive tip boundary condition at lower flow rates. However, at higher mass flow rates the constant electric field produces extruded particles with higher Coulomb energy per ion, consistent with droplet formation. Furthermore, the MD simulations show that ion emission sites differ based on the boundary condition and snapshots offer an explanation as to why some boundary condition models will predict emission in a purely ionic mode, whereas others suggest a mixed ion-droplet regime. Finally, specific impulses and thrusts are compared for the different models and are found to vary up to 30% due to differences in the average charge to mass ratio.

Discharge current distribution in stratified soil under impulse discharge

NASA Astrophysics Data System (ADS)

Eniola Fajingbesi, Fawwaz; Shahida Midi, Nur; Elsheikh, Elsheikh M. A.; Hajar Yusoff, Siti

2017-06-01

The mobility of charge particles traversing a material defines its electrical properties. Soil (earth) have long been the universal grounding before and after the inception of active ground systems for electrical appliance purpose due to it semi-conductive properties. The soil can thus be modelled as a single material exhibiting semi-complex inductive-reactive impedance. Under impulse discharge such as lightning strikes to soil this property of soil could result in electric potential level fluctuation ranging from ground potential rise/fall to electromagnetic pulse coupling that could ultimately fail connected electrical appliance. In this work we have experimentally model the soil and lightning discharge using point to plane electrode setup to observe the current distribution characteristics at different soil conductivity [mS/m] range. The result presented from this research indicate above 5% shift in conductivity before and after discharge which is significant for consideration when dealing with grounding designs. The current distribution in soil have also be successfully observed and analysed from experimental result using mean current magnitude in relation to electrode distance and location, current density variation with depth all showing strong correlation with theoretical assumptions of a semi-complex impedance material.

Electrical treeing behaviors in silicone rubber under an impulse voltage considering high temperature

NASA Astrophysics Data System (ADS)

Yunxiao, ZHANG; Yuanxiang, ZHOU; Ling, ZHANG; Zhen, LIN; Jie, LIU; Zhongliu, ZHOU

2018-05-01

In this paper, work was conducted to reveal electrical tree behaviors (initiation and propagation) of silicone rubber (SIR) under an impulse voltage with high temperature. Impulse frequencies ranging from 10 Hz to 1 kHz were applied and the temperature was controlled between 30 °C and 90 °C. Experimental results show that tree initiation voltage decreases with increasing pulse frequency, and the descending amplitude is different in different frequency bands. As the pulse frequency increases, more frequent partial discharges occur in the channel, increasing the tree growth rate and the final shape intensity. As for temperature, the initiation voltage decreases and the tree shape becomes denser as the temperature gets higher. Based on differential scanning calorimetry results, we believe that partial segment relaxation of SIR at high temperature leads to a decrease in the initiation voltage. However, the tree growth rate decreases with increasing temperature. Carbonization deposition in the channel under high temperature was observed under microscope and proven by Raman analysis. Different tree growth models considering tree channel characteristics are proposed. It is believed that increasing the conductivity in the tree channel restrains the partial discharge, holding back the tree growth at high temperature.

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.

Benefits of Nuclear Electric Propulsion for Outer Planet Exploration

NASA Technical Reports Server (NTRS)

Kos, Larry; Johnson, Les; Jones, Jonathan; Trausch, Ann; Eberle, Bill; Woodcock, Gordon; Brady, Hugh J. (Technical Monitor)

2002-01-01

Nuclear electric propulsion (NEP) offers significant benefits to missions for outer planet exploration. Reaching outer planet destinations, especially beyond Jupiter, is a struggle against time and distance. For relatively near missions, such as a Europa lander, conventional chemical propulsion and NEP offer similar performance and capabilities. For challenging missions such as a Pluto orbiter, neither chemical nor solar electric propulsion are capable while NEP offers acceptable performance. Three missions are compared in this paper: Europa lander, Pluto orbiter, and Titan sample return, illustrating how performance of conventional and advanced propulsion systems vary with increasing difficulty. The paper presents parametric trajectory performance data for NEP. Preliminary mass/performance estimates are provided for a Europa lander and a Titan sample return system, to derive net payloads for NEP. The NEP system delivers payloads and ascent/descent spacecraft to orbit around the target body, and for sample return, delivers the sample carrier system from Titan orbit to an Earth transfer trajectory. A representative scientific payload 500 kg was assumed, typical for a robotic mission. The resulting NEP systems are 100-kWe class, with specific impulse from 6000 to 9000 seconds.

a Permanent Magnet Hall Thruster for Satellite Orbit Maneuvering with Low Power

NASA Astrophysics Data System (ADS)

Ferreira, Jose Leonardo

Plasma thrusters are known to have some advantages like high specific impulse. Electric propulsion is already recognized as a successful technology for long duration space missions. It has been used as primary propulsion system on earth-moon orbit trnsfer missions, comets and asteroids exploration and on commercially geosyncronous satellite attitude control systems. Closed Drift Plasma Thrusters, also called Hall Thrusters or SPT (Stationary Plasma Thruster) was conceived inthe USSR and, since then, they have been developed in several countries such as France, USA, Japan and Brazil. In this work, introductory remarks are made with focus on the most significant contributions of the electric propulsion to the progress of space missions and its future role on the brazillian space program. The main features of an inedit Permanent Magnet Hall Thruster (PMHT) developed at the Plasma Laboratory of the University of Brasilia is presented. The idea of using an array of permanent magnets, instead of an eletromagnet, to produce a radial magnetic field inside the cylindrical plasma drift channel of the thruster is a very important improvement, because it allows the possibility of developing a Hall Thruster with electric power consumption low enough to be used in small and medium size satellites. The new Halĺplasma source characterization is presented with plasma density, temperature and potential space profiles. Ion temperature mesurements based on Doppler broadening of spectral lines and ion energy measurements of the ejected plasma plume are also shown. Based on the mesured parameters of the accelerated plasma we constructed a merit figure for the PMHT. We also perform numerical simulations of satellite orbit raising from an altitude of 700 km to 36000 km using a PMHT operating in the 100 mN to 500 mN thrust range. In order to perform these caculations, integration techniques of spacecraft trajectory were used. The main simulation parameters were: orbit raising time, propellant mass, total satellite mass, thrust, specific impulse and exaust velocity. We conclude comparing our results with results obtained in Hall Thrusters whose magnetic fields are produced by eletromagnets.

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

NASA Technical Reports Server (NTRS)

Williams, Craig Hamilton

1995-01-01

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

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.

Guide to Flow Measurement for Electric Propulsion Systems

NASA Technical Reports Server (NTRS)

Frieman, Jason D.; Walker, Mitchell L. R.; Snyder, Steve

2013-01-01

In electric propulsion (EP) systems, accurate measurement of the propellant mass flow rate of gas or liquid to the thruster and external cathode is a key input in the calculation of thruster efficiency and specific impulse. Although such measurements are often achieved with commercial mass flow controllers and meters integrated into propellant feed systems, the variability in potential propellant options and flow requirements amongst the spectrum of EP power regimes and devices complicates meter selection, integration, and operation. At the direction of the Committee on Standards for Electric Propulsion Testing, a guide was jointly developed by members of the electric propulsion community to establish a unified document that contains the working principles, methods of implementation and analysis, and calibration techniques and recommendations on the use of mass flow meters in laboratory and spacecraft electric propulsion systems. The guide is applicable to EP devices of all types and power levels ranging from microthrusters to high-power ion engines and Hall effect thrusters. The establishment of a community standard on mass flow metering will help ensure the selection of the proper meter for each application. It will also improve the quality of system performance estimates by providing comprehensive information on the physical phenomena and systematic errors that must be accounted for during the analysis of flow measurement data. This paper will outline the standard methods and recommended practices described in the guide titled "Flow Measurement for Electric Propulsion Systems."

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.

Effect of electric impulse for improved energy generation in mediatorless dual chamber microbial fuel cell through electroevolution of Escherichia coli.

PubMed

Nandy, Arpita; Kumar, Vikash; Kundu, Patit P

2016-05-15

The main emphasis of this study is to understand the electroactive behavior of a microbe in microbial fuel cell (MFC) under specific selection pressure. This study explores potential of a non-electrogenic microbe for power production in a mediatorless MFC under the influence of a specific stress. Electric pulse of specific magnitude has been applied to Escherichia coli cells in a MFC and compared the results with unpulsed (control) MFC. Maximum power density of 187.77 mW/m(2) and 284.44 mW/m(2) for the control and experimental MFC has been observed at corresponding current density of 1444.44 mA/m(2) and 1777.77 mA/m(2). The results show improved performance for the pulsed (experimental) system, despite of initial downfall with respect to the control system. This suggests bacterial adaptation against electrical pulses which leads to evolution of an efficient electrogen. This observation is further confirmed by analyzing the results of Cyclic Voltammetry (CV), Scanning Electron Microscopy (SEM) Electrochemical Impedence Spectroscopy (EIS), enlightening different attributes like electrochemical property, bacterial morphology and impedance. The study is focused on development of a microbial fuel cell catalysed by E. coli, through triggering electroactive property in the microbe by exposing it to external stress. This study is unique in nature as it is mediatorless, economical and describes about a new method of natural bacterial evolution. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Psychopathy and the prediction of alcohol-related physical aggression: the roles of impulsive antisociality and fearless dominance.

PubMed

Birkley, Erica L; Giancola, Peter R; Lance, Charles E

2013-02-01

It is well established that individual difference factors modulate aggression under the acute effects of alcohol. In this investigation, we tested the hypothesis that one core dimension of psychopathy, Impulsive Antisociality, would modulate intoxicated aggression, whereas another dimension, Fearless Dominance, would not. Participants were 516 young social drinkers (253 men and 263 women). Psychopathy was measured using the Psychopathic Personality Inventory (PPI; Lilienfeld and Andrews, 1996). Following the consumption of either an alcohol or a placebo beverage, aggression was measured with a task in which participants administered and received electric shocks to/from a fictitious opponent under the guise of a competitive reaction-time task. Hierarchical regression analyses supported our hypothesis: Impulsive Antisociality predicted aggression under alcohol, whereas Fearless Dominance did not. Persons who tend to endorse antisocial and impulsive externalizing behaviors appear to be at greater risk for aggression under the acute influence of alcohol. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Psychopathy and the Prediction of Alcohol-Related Physical Aggression: The Roles of Impulsive Antisociality and Fearless Dominance

PubMed Central

Birkley, Erica L.; Giancola, Peter R.; Lance, Charles E.

2012-01-01

Background It is well established that individual difference factors modulate aggression under the acute effects of alcohol. In this investigation, we tested the hypothesis that one core dimension of psychopathy, Impulsive Antisociality, would modulate intoxicated aggression, whereas another dimension, Fearless Dominance, would not. Methods Participants were 516 young social drinkers (253 men and 263 women). Psychopathy was measured using the Psychopathic Personality Inventory (PPI; Lilienfeld and Andrews, 1996). Following the consumption of either an alcohol or a placebo beverage, aggression was measured with a task in which participants administered and received electric shocks to/from a fictitious opponent under the guise of a competitive reaction-time task. Results Hierarchical regression analyses supported our hypothesis: Impulsive Antisociality predicted aggression under alcohol, whereas Fearless Dominance did not. Conclusions Persons who tend to endorse antisocial and impulsive externalizing behaviors appear to be at greater risk for aggression under the acute influence of alcohol. PMID:22959485

Ultra-sensitive transducer advances micro-measurement range

NASA Technical Reports Server (NTRS)

Rogallo, V. L.

1964-01-01

An ultrasensitive piezoelectric transducer, that converts minute mechanical forces into electrical impulses, measures the impact of micrometeoroids against space vehicles. It has uniform sensitivity over the entire target area and a high degree of stability.

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.

Method for enhancing low frequency output of impulsive type seismic energy sources and its application to a seismic energy source for use while drilling

DOEpatents

Radtke, Robert P; Stokes, Robert H; Glowka, David A

2014-12-02

A method for operating an impulsive type seismic energy source in a firing sequence having at least two actuations for each seismic impulse to be generated by the source. The actuations have a time delay between them related to a selected energy frequency peak of the source output. One example of the method is used for generating seismic signals in a wellbore and includes discharging electric current through a spark gap disposed in the wellbore in at least one firing sequence. The sequence includes at least two actuations of the spark gap separated by an amount of time selected to cause acoustic energy resulting from the actuations to have peak amplitude at a selected frequency.

Condition Assessment of Levees, U.S. Section of the International Boundary and Water Commission. Report 5: Flood Simulation Study of Retamal Levee, Lower Rio Grande Valley, Texas, Using Seismic and Electrical Geophysical Models

DTIC Science & Technology

2007-01-01

possessed impulsive , relatively high signal-to- noise first breaks that were picked automatically with a small percentage requiring manual adjustments...possessed greater signal-to- noise and more impulsive first arrivals than those observed on previous surveys at this site. For each compressional-wave...produced a higher signal-to- noise ratio. These differences between the two data collection events are attributed to the change in near-surface properties

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

Momentum and Heat Flux Measurements in the Exhaust of VASIMR using Helium Propellant

NASA Technical Reports Server (NTRS)

Chavers, D. Gregory; Chang-Diaz, Franklin R.; Irvine, Claude; Squire, Jared P.

2003-01-01

Interplanetary travel requires propulsion systems that can provide high specific impulse (Isp), while also having sufficient thrust to rapidly accelerate large payloads. One such propulsion system is the Variable Specific Impulse Magneto-plasma Rocket (VASIMR), which creates, heats, and ejects plasma to provide variable thrust and Isp, designed to optimally meet the mission requirements. The fraction of the total energy invested in creating the plasma, as compared to the plasma's total kinetic energy, is an important factor in determining the overall system efficiency. In VASIMR, this 'frozen flow loss' is appreciable when at high thrust, but negligible at high Isp. The loss applies to other electric thrusters as well. If some of this energy could be recovered through recombination processes, and reinjected as neutral kinetic energy, the efficiency of VASIMR, in its low Isp/high thrust mode may be improved. An experiment is being conducted to investigate the possibility of recovering some of the energy used to create the plasma by studying the flow characteristics of the charged and neutral particles in the exhaust of the thruster. This paper will cover the measurements of momentum flux and heat flux in the exhaust of the VASIMR test facility using helium as the propellant where the heat flux is comprised of both kinetic and plasma recombination energy. The flux measurements also assist in diagnosing and verifying the plasma conditions in the existing experiment.

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.

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.

A method for calculating transient thrust and flow-rate levels for Mariner type attitude control nitrogen gas jets

NASA Technical Reports Server (NTRS)

Ferrera, J. D.

1972-01-01

The purpose of this report is to define and program the transient pneumatic flow equations necessary to determine, for a given set of conditions (geometry, pressures, temperatures, valve on time, etc.), the total nitrogen impulse and mass flow per pulse for the single pulsing of a Mariner type reaction control assembly valve. The rates of opening and closing of the valves are modeled, and electrical pulse durations from 20 to 100 ms are investigated. In developing the transient flow analysis, maximum use was made of the steady-state analysis. The impulse results are also compared to an equivalent square-wave impulse for both the Mariner Mars 1971 (MM'71) and Mariner Mars 1964 (MM'64) systems. It is demonstrated that, whereas in the MM'64 system, the actual impulse was as much as 56 percent higher than an assumed impulse (which is the product of the steady-state thrust and value on time i.e., the square wave), in the MM'71 system, these two values were in error in the same direction by only approximately 4 percent because of the larger nozzle areas and shorter valve stroke used.

Solar thermal propulsion for planetary spacecraft

NASA Technical Reports Server (NTRS)

Sercel, J. C.

1985-01-01

Previous studies have shown that many desirable planetary exploration missions require large injection delta-V. Solar Thermal Rocket (STR) propulsion, under study for orbit-raising applications may enhance or enable such high-energy missions. The required technology of thermal control for liquid hydrogen propellant is available for the required storage duration. Self-deploying, inflatable solar concentrators are under study. The mass penalty for passive cryogenic thermal control, liquid hydrogen tanks and solar concentrators does not compromise the specific impulse advantage afforded by the STR as compared to chemical propulsion systems. An STR injection module is characterized and performance is evaluated by comparison to electric propulsion options for the Saturn Orbiter Titan Probe (SOTP) and Uranus Flyby Uranus Probe (UFUP) missions.

Safe, Affordable, Nuclear Thermal Propulsion Systems

NASA Technical Reports Server (NTRS)

Houts, M. G.; Kim, T.; Emrich, W. J.; Hickman, R. R.; Broadway, J. W.; Gerrish, H. P.; Doughty, G. E.

2014-01-01

The fundamental capability of Nuclear Thermal Propulsion (NTP) is game changing for space exploration. A first generation Nuclear Cryogenic Propulsion Stage (NCPS) based on NTP could provide high thrust at a specific impulse above 900 s, roughly double that of state of the art chemical engines. Characteristics of fission and NTP indicate that useful first generation systems will provide a foundation for future systems with extremely high performance. The role of the NCPS in the development of advanced nuclear propulsion systems could be analogous to the role of the DC-3 in the development of advanced aviation. Progress made under the NCPS project could help enable both advanced NTP and advanced Nuclear Electric Propulsion (NEP).

The Nuclear Cryogenic Propulsion Stage

NASA Technical Reports Server (NTRS)

Houts, Michael G.; Kim, Tony; Emrich, William J.; Hickman, Robert R.; Broadway, Jeramie W.; Gerrish, Harold P.; Doughty, Glen; Belvin, Anthony; Borowski, Stanley K.; Scott, John

2014-01-01

The fundamental capability of Nuclear Thermal Propulsion (NTP) is game changing for space exploration. A first generation Nuclear Cryogenic Propulsion Stage (NCPS) based on NTP could provide high thrust at a specific impulse above 900 s, roughly double that of state of the art chemical engines. Characteristics of fission and NTP indicate that useful first generation systems will provide a foundation for future systems with extremely high performance. The role of the NCPS in the development of advanced nuclear propulsion systems could be analogous to the role of the DC-3 in the development of advanced aviation. Progres made under the NCPS project could help enable both advanced NTP and advanced Nuclear Electric Propulsion (NEP).

Nuclear Cryogenic Propulsion Stage for Mars Exploration

NASA Technical Reports Server (NTRS)

Houts, M. G.; Borowski, S. K.; George, J. A.; Kim, T.; Emrich, W. J.; Hickman, R. R.; Broadway, J. W.; Gerrish, H. P.; Adams, R. B.

2012-01-01

The fundamental capability of Nuclear Thermal Propulsion (NTP) is game changing for space exploration. A first generation Nuclear Cryogenic Propulsion Stage (NCPS) based on NTP could provide high thrust at a specific impulse above 900 s, roughly double that of state of the art chemical engines. Characteristics of fission and NTP indicate that useful first generation systems will provide a foundation for future systems with extremely high performance. The role of the NCPS in the development of advanced nuclear propulsion systems could be analogous to the role of the DC-3 in the development of advanced aviation. Progress made under the NCPS project could help enable both advanced NTP and advanced Nuclear Electric Propulsion (NEP).

Nuclear Thermal Propulsion for Advanced Space Exploration

NASA Technical Reports Server (NTRS)

Houts, M. G.; Borowski, S. K.; George, J. A.; Kim, T.; Emrich, W. J.; Hickman, R. R.; Broadway, J. W.; Gerrish, H. P.; Adams, R. B.

2012-01-01

The fundamental capability of Nuclear Thermal Propulsion (NTP) is game changing for space exploration. A first generation Nuclear Cryogenic Propulsion Stage (NCPS) based on NTP could provide high thrust at a specific impulse above 900 s, roughly double that of state of the art chemical engines. Characteristics of fission and NTP indicate that useful first generation systems will provide a foundation for future systems with extremely high performance. The role of the NCPS in the development of advanced nuclear propulsion systems could be analogous to the role of the DC-3 in the development of advanced aviation. Progress made under the NCPS project could help enable both advanced NTP and advanced Nuclear Electric Propulsion (NEP).

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).

Urinary Incontinence Surgery: When Other Treatments Aren't Enough

MedlinePlus

... surgery. Certain procedures to treat overactive bladder involve stimulation — using small, electrical impulses — of the nerves that signal the need to urinate. Sacral nerve stimulation. Your surgeon implants a small, pacemaker-like device ...

Recommended Practices in Thrust Measurements

NASA Technical Reports Server (NTRS)

Polk, James E.; Pancotti, Anthony; Haag, Thomas; King, Scott; Walker, Mitchell; Blakely, Joseph; Ziemer, John

2013-01-01

Accurate, direct measurement of thrust or impulse is one of the most critical elements of electric thruster characterization, and one of the most difficult measurements to make. The American Institute of Aeronautics and Astronautics has started an initiative to develop standards for many important measurement processes in electric propulsion, including thrust measurements. This paper summarizes recommended practices for the design, calibration, and operation of pendulum thrust stands, which are widely recognized as the best approach for measuring micro N- to mN-level thrust and micro Ns-level impulse bits. The fundamentals of pendulum thrust stand operation are reviewed, along with its implementation in hanging pendulum, inverted pendulum, and torsional balance configurations. Methods of calibration and recommendations for calibration processes are presented. Sources of error are identified and methods for data processing and uncertainty analysis are discussed. This review is intended to be the first step toward a recommended practices document to help the community produce high quality thrust measurements.

MEMS-Based Solid Propellant Rocket Array Thruster

NASA Astrophysics Data System (ADS)

Tanaka, Shuji; Hosokawa, Ryuichiro; Tokudome, Shin-Ichiro; Hori, Keiichi; Saito, Hirobumi; Watanabe, Masashi; Esashi, Masayoshi

The prototype of a solid propellant rocket array thruster for simple attitude control of a 10 kg class micro-spacecraft was completed and tested. The prototype has 10×10 φ0.8 mm solid propellant micro-rockets arrayed at a pitch of 1.2 mm on a 20×22 mm substrate. To realize such a dense array of micro-rockets, each ignition heater is powered from the backside of the thruster through an electrical feedthrough which passes along a propellant cylinder wall. Boron/potassium nitrate propellant (NAB) is used with/without lead rhodanide/potassium chlorate/nitrocellulose ignition aid (RK). Impulse thrust was measured by a pendulum method in air. Ignition required electric power of at least 3 4 W with RK and 4 6 W without RK. Measured impulse thrusts were from 2×10-5 Ns to 3×10-4 Ns after the calculation of compensation for air dumping.

Impulsive penetration : a viable mechanism for plasma entry across the magnetopause ?

NASA Astrophysics Data System (ADS)

De Keyser, Johan; Echim, Marius; Darrouzet, Fabien; Gunell, Herbert

Density inhomogeneities in the solar wind may cross the bow shock, and retain an excess earthward momentum in the magnetosheath upon approaching the magnetopause. Also, the bow shock dynamics as well as the behaviour of the magnetopause itself may introduce spatial inhomogeneities in the magnetosheath density and/or flow. Plasma entities with excess momentum may penetrate across the magnetopause, by the impulsive penetration mechanism. This plasma entry mechanism requires the existence of a polarization electric field in the moving blob, that is sustained by charge separation layers in the interfaces at the flanks of the blob. Both direct observation and simulation of plasma entry across the magnetopause following the impulsive penetration mechanism are hard. It is difficult to prove that observed plasma entry is really due to the impulsive penetration mechanism since the required charge separation layers or the resulting polarization electric field are hard to measure directly. Simply assessing the geometry is not easy, although multi-spacecraft missions like Cluster have resolved many of the ambiguities inherent in single-spacecraft measurements. Impulsive penetration is difficult to simulate as it operates on the fluid, the ion, and the electron scales simultaneously. It requires not only a high spatial resolution, but also a high precision to properly represent the charge imbalance in the flank interfaces. We have modelled impulsive penetration with a kinetic model, by simplifying the problem. The fully kinetic model is 3-dimensional in velocity space, but we consider spatial structure only along a single spatial dimension, namely the coordinate transverse to the blob’s direction of motion. We thereby assume that the blob is elongated both along the magnetic field and in the direction of motion. The model is semi-analytic and is able to represent the charge imbalance in the blob edges very well. In a second modelling step, we consider a slow, quasi-static change of this structure as the blob penetrates deeper into the magnetosphere, resulting in a description of the evolution of the penetrating plasma blob as a consequence of both adiabatic and non-adiabatic deceleration. Although the simulation considers this a simplified geometry, it sheds some light on some fundamental aspects of this plasma entry mechanism.

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.

Effects of RTV coating on the electrical performance of polymer insulator under lightning impulse voltage condition.

PubMed

Jamaludin, Farah Adilah; Ab-Kadir, Mohd Zainal Abidin; Izadi, Mahdi; Azis, Norhafiz; Jasni, Jasronita; Abd-Rahman, Muhammad Syahmi

2017-01-01

Located near the equator, Malaysia is a country with one of the highest lightning densities in the world. Lightning contributes to 70% of the power outages in Malaysia and affects power equipment, automated network systems, causes data losses and monetary losses in the nation. Therefore, consideration of insulator evaluation under lightning impulses can be crucial to evaluate and attempt to overcome this issue. This paper presents a new approach to increase the electrical performance of polymer insulators using a Room Temperature Vulcanisation (RTV) coating. The evaluation involves three different settings of polymer insulator, namely uncoated, RTV type 1, and RTV type 2 upper surface coatings. All the insulators were tested under three different conditions as dry, clean wet and salty under different impulse polarities using the even-rising test method. The voltage breakdown for each test was recorded. From the experiment, it was found that the effectiveness of the RTV coating application became apparent when tested under salty or polluted conditions. It increased the voltage withstand capabilities of the polymer insulator up to 50% from the basic uncoated insulator. Under dry and clean conditions, the RTV coating provided just a slight increase of the breakdown voltage. The increase in voltage breakdown capability decreased the probability of surface discharge and dry band arcing that could cause degradation of the polymeric material housing. The RTV type 1 coating was found to be more effective when performing under a lightning impulse. The findings might help the utility companies improve the performance of their insulators in order to increase power system reliability.

Effects of RTV coating on the electrical performance of polymer insulator under lightning impulse voltage condition

PubMed Central

Jamaludin, Farah Adilah; Ab-Kadir, Mohd Zainal Abidin; Izadi, Mahdi; Azis, Norhafiz; Jasni, Jasronita; Abd-Rahman, Muhammad Syahmi

2017-01-01

Located near the equator, Malaysia is a country with one of the highest lightning densities in the world. Lightning contributes to 70% of the power outages in Malaysia and affects power equipment, automated network systems, causes data losses and monetary losses in the nation. Therefore, consideration of insulator evaluation under lightning impulses can be crucial to evaluate and attempt to overcome this issue. This paper presents a new approach to increase the electrical performance of polymer insulators using a Room Temperature Vulcanisation (RTV) coating. The evaluation involves three different settings of polymer insulator, namely uncoated, RTV type 1, and RTV type 2 upper surface coatings. All the insulators were tested under three different conditions as dry, clean wet and salty under different impulse polarities using the even-rising test method. The voltage breakdown for each test was recorded. From the experiment, it was found that the effectiveness of the RTV coating application became apparent when tested under salty or polluted conditions. It increased the voltage withstand capabilities of the polymer insulator up to 50% from the basic uncoated insulator. Under dry and clean conditions, the RTV coating provided just a slight increase of the breakdown voltage. The increase in voltage breakdown capability decreased the probability of surface discharge and dry band arcing that could cause degradation of the polymeric material housing. The RTV type 1 coating was found to be more effective when performing under a lightning impulse. The findings might help the utility companies improve the performance of their insulators in order to increase power system reliability. PMID:29136025

Q-Thruster Breadboard Campaign Project

NASA Technical Reports Server (NTRS)

White, Harold

2014-01-01

Dr. Harold "Sonny" White has developed the physics theory basis for utilizing the quantum vacuum to produce thrust. The engineering implementation of the theory is known as Q-thrusters. During FY13, three test campaigns were conducted that conclusively demonstrated tangible evidence of Q-thruster physics with measurable thrust bringing the TRL up from TRL 2 to early TRL 3. This project will continue with the development of the technology to a breadboard level by leveraging the most recent NASA/industry test hardware. This project will replace the manual tuning process used in the 2013 test campaign with an automated Radio Frequency (RF) Phase Lock Loop system (precursor to flight-like implementation), and will redesign the signal ports to minimize RF leakage (improves efficiency). This project will build on the 2013 test campaign using the above improvements on the test implementation to get ready for subsequent Independent Verification and Validation testing at Glenn Research Center (GRC) and Jet Propulsion Laboratory (JPL) in FY 2015. Q-thruster technology has a much higher thrust to power than current forms of electric propulsion (7x Hall thrusters), and can significantly reduce the total power required for either Solar Electric Propulsion (SEP) or Nuclear Electric Propulsion (NEP). Also, due to the high thrust and high specific impulse, Q-thruster technology will greatly relax the specific mass requirements for in-space nuclear reactor systems. Q-thrusters can reduce transit times for a power-constrained architecture.

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.

Impacts of Interior Permanent Magnet Machine Technology for Electric Vehicles

DTIC Science & Technology

2012-01-01

corrosion constraints of magnets  Minimum gear and more direct drive  Regenerative braking and short charging cycle of batteries  Impulse...be found in limited applications such as, antilock braking system (ABS) of the vehicles. Considering the performance enhancement and reliability of... system forms the backbone of modern society. Electricity and its accessibility is one of the major engineering achievements. In order to maintain and

Islands of spatially discordant APD alternans underlie arrhythmogenesis by promoting electrotonic dyssynchrony in models of fibrotic rat ventricular myocardium

NASA Astrophysics Data System (ADS)

Majumder, Rupamanjari; Engels, Marc C.; de Vries, Antoine A. F.; Panfilov, Alexander V.; Pijnappels, Daniël A.

2016-04-01

Fibrosis and altered gap junctional coupling are key features of ventricular remodelling and are associated with abnormal electrical impulse generation and propagation. Such abnormalities predispose to reentrant electrical activity in the heart. In the absence of tissue heterogeneity, high-frequency impulse generation can also induce dynamic electrical instabilities leading to reentrant arrhythmias. However, because of the complexity and stochastic nature of such arrhythmias, the combined effects of tissue heterogeneity and dynamical instabilities in these arrhythmias have not been explored in detail. Here, arrhythmogenesis was studied using in vitro and in silico monolayer models of neonatal rat ventricular tissue with 30% randomly distributed cardiac myofibroblasts and systematically lowered intercellular coupling achieved in vitro through graded knockdown of connexin43 expression. Arrhythmia incidence and complexity increased with decreasing intercellular coupling efficiency. This coincided with the onset of a specialized type of spatially discordant action potential duration alternans characterized by island-like areas of opposite alternans phase, which positively correlated with the degree of connexinx43 knockdown and arrhythmia complexity. At higher myofibroblast densities, more of these islands were formed and reentrant arrhythmias were more easily induced. This is the first study exploring the combinatorial effects of myocardial fibrosis and dynamic electrical instabilities on reentrant arrhythmia initiation and complexity.

Dynamic range in the C. elegans brain network

NASA Astrophysics Data System (ADS)

Antonopoulos, Chris G.

2016-01-01

We study external electrical perturbations and their responses in the brain dynamic network of the Caenorhabditis elegans soil worm, given by the connectome of its large somatic nervous system. Our analysis is inspired by a realistic experiment where one stimulates externally specific parts of the brain and studies the persistent neural activity triggered in other cortical regions. In this work, we perturb groups of neurons that form communities, identified by the walktrap community detection method, by trains of stereotypical electrical Poissonian impulses and study the propagation of neural activity to other communities by measuring the corresponding dynamic ranges and Steven law exponents. We show that when one perturbs specific communities, keeping the rest unperturbed, the external stimulations are able to propagate to some of them but not to all. There are also perturbations that do not trigger any response. We found that this depends on the initially perturbed community. Finally, we relate our findings for the former cases with low neural synchronization, self-criticality, and large information flow capacity, and interpret them as the ability of the brain network to respond to external perturbations when it works at criticality and its information flow capacity becomes maximal.

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.

Electric propulsion options for 10 kW class earth space missions

NASA Technical Reports Server (NTRS)

Patterson, M. J.; Curran, Francis M.

1989-01-01

Five and 10 kW ion and arcjet propulsion system options for a near-term space demonstration experiment have been evaluated. Analyses were conducted to determine first-order propulsion system performance and system component mass estimates. Overall mission performance of the electric propulsion systems was quantified in terms of the maximum thrusting time, total impulse, and velocity increment capability available when integrated onto a generic spacecraft under fixed mission model assumptions. Maximum available thrusting times for the ion-propelled spacecraft options, launched on a DELTA II 6920 vehicle, range from approximately 8,600 hours for a 4-engine 10 kW system to more than 29,600 hours for a single-engine 5 kW system. Maximum total impulse values and maximum delta-v's range from 1.2x10(7) to 2.1x10(7) N-s, and 3550 to 6200 m/s, respectively. Maximum available thrusting times for the arcjet propelled spacecraft launched on the DELTA II 6920 vehicle range from approximately 528 hours for the 6-engine 10 kW hydrazine system to 2328 hours for the single-engine 5 kW system. Maximum total impulse values and maximum delta-v's range from 2.2x10(6) to 3.6x10(6) N-s, and approximately 662 to 1072 m/s, respectively.

Response of energetic particles to local magnetic dipolarization inside geosynchronous orbit

NASA Astrophysics Data System (ADS)

Motoba, T.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.

2017-12-01

Magnetic field dipolarization and energetic particle injections are the most distinct phenomena observed in the inner magnetosphere during the substorm expansion phase. Compared to a wealth of knowledge about the phenomenology of magnetic dipolarizations and particle injections at/outside geosynchronous orbit (GEO), our understanding of them inside GEO remains incomplete because of a very limited number of previous studies. In the present study, we statistically examine the response of 1-1000 keV energetic particles to local magnetic dipolarization by performing a superposed epoch analysis of energetic particle fluxes with the zero epoch defined as the dipolarization onset times. Based on data from the Van Allen Probes tail seasons in 2012-2016, we identified a total of 97 magnetic dipolarization events which occurred closer to the magnetic equator (i.e., BH, which is antiparallel to the Earth's dipole axis, is the dominant component of the local magnetic field at least for 5 min before the onset). For major ion species (hydrogen, helium, and oxygen ions), the relative flux intensity to the pre-onset level increases at > 50 keV and decreases at < 30 keV. The hydrogen and helium ion fluxes in the hundreds of keV range sharply increase within a minute after the onset and then decay. Compared to the short-lived nature of hydrogen and helium ion flux enhancements, oxygen ion fluxes are enhanced more gradually (on the order of several minutes). The relative ion flux intensity and peak energy generally tend to increase for stronger dipolarization-related impulsive westward electric field. This suggests that the impulsive electric field is responsible for the energization and/or transport of energetic ions inside GEO. On the other hand, the electron flux enhancement first appears from several tens of keV to a few hundreds of keV, and then exhibits an inverse energy dispersion. For dipolarizations with strong impulsive westward electric fields, the relative electron flux intensity increases up to 5-10 times, in particular most significant at several tens of keV. This result suggests that the impulsive electric field acts as an efficient factor in the rapid energization of the tens-of-keV electrons. We also discuss how the response of energetic particles to dipolarization depends on MLT, radial distance, and pitch angle.

Human aquaporin 4 gating dynamics under and after nanosecond-scale static and alternating electric-field impulses: a molecular dynamics study of field effects and relaxation.

PubMed

Reale, Riccardo; English, Niall J; Garate, José-Antonio; Marracino, Paolo; Liberti, Micaela; Apollonio, Francesca

2013-11-28

Water self-diffusion and the dipolar response of the selectivity filter within human aquaporin 4 have been studied using molecular dynamics (MD) simulations in the absence and presence of pulses of external static and alternating electric fields. The pulses were approximately 50 and 100 ns in duration and 0.0065 V/Å in (r.m.s.) intensity and were either static or else 2.45 or 100 GHz in frequency and applied both along and perpendicular to the channels. In addition, the relaxation of the aquaporin, water self-diffusion and gating dynamics following cessation of the impulses was studied. In previous work it was determined that switches in the dihedral angle of the selectivity filter led to boosting of water permeation events within the channels, in the presence of identical external static and alternating electric fields, although applied continuously. Here the application of field impulses (and subsequently, upon removal) has shown that it is the dipolar orientation of the histidine-201 residue in the selectivity filter which governs the dihedral angle, and hence influences water self-diffusion; this constitutes an appropriate order parameter. The dipolar response of this residue to the applied field leads to the adoption of four distinct states, which we modelled as time-homogeneous Markov jump processes, and may be distinguished in the potential of mean force (PMF) as a function of the dipolar orientation of histidine-201. The observations of enhanced "dipolar flipping" of H201 serve to explain increased levels of water self-diffusion within aquaporin channels during, and immediately following, field impulses, although the level of statistical certainty here is lower. Given the appreciable size of the energy barriers evident in PMFs computed directly from deterministic MD (whether in the absence or presence of external fields), metadynamics calculations were undertaken to explore the free-energy landscape of histidine-201 orientation with greater accuracy and precision. These indicate that electric fields do alter the free-energy profile of the H201 side-chain orientation, wherein a perturbation of the symmetric bimodal state evident in the zero-field case is observed. These effects are dependent on the field intensities.

Impulse Magnetization of Nd-Fe-B Sintered Magnets for Sensors

PubMed Central

Przybylski, Marek; Kapelski, Dariusz; Ślusarek, Barbara; Wiak, Sławomir

2016-01-01

Magnetization of large Nd-Fe-B sintered permanent magnets is still challenging. This type of permanent magnet is electrically conductive, so impulse magnetization causes a flow of eddy currents which prevent magnetization of the whole volume of the magnet. The paper deals with the impulse magnetization of sintered Nd-Fe-B permanent magnets and shows a method for the determination of suitable parameters for the supply system. The necessary magnetic field strength for magnetization of the magnet to saturation was determined. The optimal magnetizing fixture supply voltage for magnetization to saturation was determined from simulations in PSpice software, finite element analyses in Maxwell 15 and measurements. Measurements of magnetic induction on the surface of the Nd-Fe-B magnet are also presented to ensure that a magnet with 70 mm diameter and 20 mm in height is fully saturated. PMID:27110783

Impulse Magnetization of Nd-Fe-B Sintered Magnets for Sensors.

PubMed

Przybylski, Marek; Kapelski, Dariusz; Ślusarek, Barbara; Wiak, Sławomir

2016-04-21

Magnetization of large Nd-Fe-B sintered permanent magnets is still challenging. This type of permanent magnet is electrically conductive, so impulse magnetization causes a flow of eddy currents which prevent magnetization of the whole volume of the magnet. The paper deals with the impulse magnetization of sintered Nd-Fe-B permanent magnets and shows a method for the determination of suitable parameters for the supply system. The necessary magnetic field strength for magnetization of the magnet to saturation was determined. The optimal magnetizing fixture supply voltage for magnetization to saturation was determined from simulations in PSpice software, finite element analyses in Maxwell 15 and measurements. Measurements of magnetic induction on the surface of the Nd-Fe-B magnet are also presented to ensure that a magnet with 70 mm diameter and 20 mm in height is fully saturated.

On Whether Angular Momentum in Electric and Magnetic Fields Radiates to Infinity

NASA Technical Reports Server (NTRS)

Canning, Francis X.; Knudsen, Steven

2006-01-01

The Feynman Disk experiment and a related thought experiment with a static magnetic field and capacitor are studied. The mechanical torque integrated over time (angular impulse) is related to the angular momentum in the electric/magnetic field. This is not called an electromagnetic field since quasi-static as well as electromagnetic effects are included. The angular momentum in the electric/magnetic field is examined to determine its static and radiative components. This comparison was then examined to see if it clarified the Abraham-Minkowski paradox.

Selection and Prioritization of Advanced Propulsion Technologies for Future Space Missions

NASA Technical Reports Server (NTRS)

Eberle, Bill; Farris, Bob; Johnson, Les; Jones, Jonathan; Kos, Larry; Woodcock, Gordon; Brady, Hugh J. (Technical Monitor)

2002-01-01

The exploration of our solar system will require spacecraft with much greater capability than spacecraft which have been launched in the past. This is particularly true for exploration of the outer planets. Outer planet exploration requires shorter trip times, increased payload mass, and ability to orbit or land on outer planets. Increased capability requires better propulsion systems, including increased specific impulse. Chemical propulsion systems are not capable of delivering the performance required for exploration of the solar system. Future propulsion systems will be applied to a wide variety of missions with a diverse set of mission requirements. Many candidate propulsion technologies have been proposed but NASA resources do not permit development of a] of them. Therefore, we need to rationally select a few propulsion technologies for advancement, for application to future space missions. An effort was initiated to select and prioritize candidate propulsion technologies for development investment. The results of the study identified Aerocapture, 5 - 10 KW Solar Electric Ion, and Nuclear Electric Propulsion as high priority technologies. Solar Sails, 100 Kw Solar Electric Hall Thrusters, Electric Propulsion, and Advanced Chemical were identified as medium priority technologies. Plasma sails, momentum exchange tethers, and low density solar sails were identified as high risk/high payoff technologies.

Tutorial: Physics and modeling of Hall thrusters

NASA Astrophysics Data System (ADS)

Boeuf, Jean-Pierre

2017-01-01

Hall thrusters are very efficient and competitive electric propulsion devices for satellites and are currently in use in a number of telecommunications and government spacecraft. Their power spans from 100 W to 20 kW, with thrust between a few mN and 1 N and specific impulse values between 1000 and 3000 s. The basic idea of Hall thrusters consists in generating a large local electric field in a plasma by using a transverse magnetic field to reduce the electron conductivity. This electric field can extract positive ions from the plasma and accelerate them to high velocity without extracting grids, providing the thrust. These principles are simple in appearance but the physics of Hall thrusters is very intricate and non-linear because of the complex electron transport across the magnetic field and its coupling with the electric field and the neutral atom density. This paper describes the basic physics of Hall thrusters and gives a (non-exhaustive) summary of the research efforts that have been devoted to the modelling and understanding of these devices in the last 20 years. Although the predictive capabilities of the models are still not sufficient for a full computer aided design of Hall thrusters, significant progress has been made in the qualitative and quantitative understanding of these devices.

A high power ion thruster for deep space missions

NASA Astrophysics Data System (ADS)

Polk, James E.; Goebel, Dan M.; Snyder, John S.; Schneider, Analyn C.; Johnson, Lee K.; Sengupta, Anita

2012-07-01

The Nuclear Electric Xenon Ion System ion thruster was developed for potential outer planet robotic missions using nuclear electric propulsion (NEP). This engine was designed to operate at power levels ranging from 13 to 28 kW at specific impulses of 6000-8500 s and for burn times of up to 10 years. State-of-the-art performance and life assessment tools were used to design the thruster, which featured 57-cm-diameter carbon-carbon composite grids operating at voltages of 3.5-6.5 kV. Preliminary validation of the thruster performance was accomplished with a laboratory model thruster, while in parallel, a flight-like development model (DM) thruster was completed and two DM thrusters fabricated. The first thruster completed full performance testing and a 2000-h wear test. The second successfully completed vibration tests at the full protoflight levels defined for this NEP program and then passed performance validation testing. The thruster design, performance, and the experimental validation of the design tools are discussed in this paper.

A high power ion thruster for deep space missions.

PubMed

Polk, James E; Goebel, Dan M; Snyder, John S; Schneider, Analyn C; Johnson, Lee K; Sengupta, Anita

2012-07-01

The Nuclear Electric Xenon Ion System ion thruster was developed for potential outer planet robotic missions using nuclear electric propulsion (NEP). This engine was designed to operate at power levels ranging from 13 to 28 kW at specific impulses of 6000-8500 s and for burn times of up to 10 years. State-of-the-art performance and life assessment tools were used to design the thruster, which featured 57-cm-diameter carbon-carbon composite grids operating at voltages of 3.5-6.5 kV. Preliminary validation of the thruster performance was accomplished with a laboratory model thruster, while in parallel, a flight-like development model (DM) thruster was completed and two DM thrusters fabricated. The first thruster completed full performance testing and a 2000-h wear test. The second successfully completed vibration tests at the full protoflight levels defined for this NEP program and then passed performance validation testing. The thruster design, performance, and the experimental validation of the design tools are discussed in this paper.

Nuclear Thermal Rocket (NTR) Propulsion and Power Systems for Outer Planetary Exploration Missions

NASA Technical Reports Server (NTRS)

Borowski, S. K.; Cataldo, R. L.

2001-01-01

The high specific impulse (I (sub sp)) and engine thrust generated using liquid hydrogen (LH2)-cooled Nuclear Thermal Rocket (NTR) propulsion makes them attractive for upper stage applications for difficult robotic science missions to the outer planets. Besides high (I (sub sp)) and thrust, NTR engines can also be designed for "bimodal" operation allowing substantial amounts of electrical power (10's of kWe ) to be generated for onboard spacecraft systems and high data rate communications with Earth during the course of the mission. Two possible options for using the NTR are examined here. A high performance injection stage utilizing a single 15 klbf thrust engine can inject large payloads to the outer planets using a 20 t-class launch vehicle when operated in an "expendable mode". A smaller bimodal NTR stage generating approx. 1 klbf of thrust and 20 to 40 kWe for electric propulsion can deliver approx. 100 kg using lower cost launch vehicles. Additional information is contained in the original extended abstract.

Mass comparisons of electric propulsion systems for NSSK of geosynchronous spacecraft. [North-South Station Keeping

NASA Technical Reports Server (NTRS)

Rawlin, V. K.; Majcher, G. A.

1991-01-01

A model was developed and exercised to allow wet mass comparisons of three-axis stabilized communications satellites delivered to geosynchronous transfer orbit. The mass benefits of using advanced chemical propulsion for apogee injection and north-south stationkeeping (NSSK) functions or electric propulsion (hydrazine arcjets and xenon ion thrusters) for NSSK functions are documented. A large derated ion thruster is proposed which minimizes thruster lifetime concerns and qualification test times when compared to those of smaller ion thrusters planned for NSSK applications. The mass benefits, which depend on the spacecraft mass and mission duration, increase dramatically with arcjet specific impulse in the 500-600 s range, but are nearly constant for the derated ion thruster operated in the 2300-3000 s range. For a given mission, the mass benefits with an ion system are typically double those of the arcjet system; however, the total thrusting time with arcjets is less than one-third that with ion thrusters for the same thruster power.

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

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.

Orbital transfer of large space structures with nuclear electric rockets

NASA Technical Reports Server (NTRS)

Silva, T. H.; Byers, D. C.

1980-01-01

This paper discusses the potential application of electric propulsion for orbit transfer of a large spacecraft structure from low earth orbit to geosynchronous altitude in a deployed configuration. The electric power was provided by the spacecraft nuclear reactor space power system on a shared basis during transfer operations. Factors considered with respect to system effectiveness included nuclear power source sizing, electric propulsion thruster concept, spacecraft deployment constraints, and orbital operations and safety. It is shown that the favorable total impulse capability inherent in electric propulsion provides a potential economic advantage over chemical propulsion orbit transfer vehicles by reducing the number of Space Shuttle flights in ground-to-orbit transportation requirements.

A sensor for vector electric field measurements through a nonlinear anisotropic optical crystal

NASA Astrophysics Data System (ADS)

Barbieri, Luca; Gondola, Marco; Potenza, Marco; Villa, Andrea; Malgesini, Roberto

2017-11-01

Electrical applications require the development of electric field sensors that can reproduce vector electric field waveforms with a very large spectral width ranging from 50 Hz to at least 70 MHz. This makes it possible to measure both the normal operation modes of electrical components and abnormal behaviors such as the corona emission and partial discharges. In this work, we aim to develop a fully dielectric sensor capable of measuring two components of the electric field using a wide class of optical crystals including anisotropic ones, whereas most of the efforts in this field have been devoted to isotropic crystals. We report the results of the measurements performed at 50 Hz and with a lightning impulse, to validate the sensor.

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.

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.

Laboratory studies of near-grazing impulsive sound propagating over rough water.

PubMed

Qin, Qin; Lukaschuk, Sergei; Attenborough, Keith

2008-08-01

Acoustic impulses due to an electrical spark source (main acoustic energy near 15 kHz) have been measured after propagating near to the water surface in a shallow container resting on a vibrating platform. Control of the platform vibration enabled control of water wave amplitudes. Analysis of the results reveals systematic variations in the received acoustic waveforms as the mean trough-to-crest water wave amplitude is increased up to 7 mm. The amplitudes of the peaks corresponding to specular reflections are reduced and the variability in the tails of the waveforms is increased.

Instrumentation for investigation of corona discharges from insulated wires

NASA Technical Reports Server (NTRS)

Doreswamy, C. V.; Crowell, C. S.

1975-01-01

A coaxial cylinder configuration is used to investigate the effect of corona impulses on the deterioration of electrical insulation. The corona currents flowing through the resistance develop a voltage which is fed to the measuring set-up. The value of this resistance is made equal to the surge impedance of the coaxial cylinder set up to prevent reflections. This instrumentation includes a phase shifter and Schmidt trigger and is designed to sample, measure, and display corona impulses occurring during any predetermined sampling period of a randomly selectable half cycle of the 60 Hz high voltage wave.

Self-organization and self-limitation in high power impulse magnetron sputtering

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

Anders, Andre

The plasma over the racetrack in high power impulse magnetron sputtering develops in traveling ionization zones. Power densities can locally reach 10{sup 9} W/m{sup 2}, which is much higher than usually reported. Ionization zones move because ions are 'evacuated' by the electric field, exposing neutrals to magnetically confined, drifting electrons. Drifting secondary electrons amplify ionization of the same ionization zone where the primary ions came from, while sputtered and outgassing atoms are supplied to the following zone(s). Strong density gradients parallel to the target disrupt electron confinement: a negative feedback mechanism that stabilizes ionization runaway.

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

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.

The role of rotors in atrial fibrillation

PubMed Central

Swarup, Vijay; Narayan, Sanjiv M.

2015-01-01

Despite significant advances in our understanding of atrial fibrillation (AF) mechanisms in the last 15 years, ablation outcomes remain suboptimal. A potential reason is that many ablation techniques focus on anatomic, rather than patient-specific functional targets for ablation. Panoramic contact mapping, incorporating phase analysis, repolarization and conduction dynamics, and oscillations in AF rate, overcomes many prior difficulties with mapping AF. This approach provides evidence that the mechanisms sustaining human AF are deterministic, largely due to stable electrical rotors and focal sources in either atrium. Ablation of such sources (Focal Impulse and Rotor Modulation: FIRM ablation) has been shown to improve ablation outcome compared with conventional ablation alone; independent laboratories directly targeting stable rotors have shown similar results. Clinical trials examining the role of stand-alone FIRM ablation are in progress. Looking forward, translating insights from patient-specific mapping to evidence-based guidelines and clinical practice is the next challenge in improving patient outcomes in AF management. PMID:25713729

Technology Area Roadmap for In Space Propulsion Technologies

NASA Technical Reports Server (NTRS)

Johnson, Les; Meyer, Mike; Coote, David; Goebel, Dan; Palaszewski, Bryan; White, Sonny

2010-01-01

This slide presentation reviews the technology area (TA) roadmap to develop propulsion technologies that will be used to enable further exploration of the solar system, and beyond. It is hoped that development of the technologies within this TA will result in technical solutions that will improve thrust levels, specific impulse, power, specific mass, volume, system mass, system complexity, operational complexity, commonality with other spacecraft systems, manufacturability and durability. Some of the propulsion technologies that are reviewed include: chemical and non-chemical propulsion, and advanced propulsion (i.e., those with a Technology Readiness level of less than 3). Examples of these advanced technologies include: Beamed Energy, Electric Sail, Fusion, High Energy Density Materials, Antimatter, Advanced Fission and Breakthrough propulsion technologies. Timeframes for development of some of these propulsion technologies are reviewed, and top technical challenges are reviewed. This roadmap describes a portfolio of in-space propulsion technologies that can meet future space science and exploration needs.

Low Cost Electric Propulsion Thruster for Deep Space Robotic Science Missions

NASA Technical Reports Server (NTRS)

Manzella, David

2008-01-01

Electric Propulsion (EP) has found widespread acceptance by commercial satellite providers for on-orbit station keeping due to the total life cycle cost advantages these systems offer. NASA has also sought to benefit from the use of EP for primary propulsion onboard the Deep Space-1 and DAWN spacecraft. These applications utilized EP systems based on gridded ion thrusters, which offer performance unequaled by other electric propulsion thrusters. Through the In-Space Propulsion Project, a lower cost thruster technology is currently under development designed to make electric propulsion intended for primary propulsion applications cost competitive with chemical propulsion systems. The basis for this new technology is a very reliable electric propulsion thruster called the Hall thruster. Hall thrusters, which have been flown by the Russians dating back to the 1970s, have been used by the Europeans on the SMART-1 lunar orbiter and currently employed by 15 other geostationary spacecraft. Since the inception of the Hall thruster, over 100 of these devices have been used with no known failures. This paper describes the latest accomplishments of a development task that seeks to improve Hall thruster technology by increasing its specific impulse, throttle-ability, and lifetime to make this type of electric propulsion thruster applicable to NASA deep space science missions. In addition to discussing recent progress on this task, this paper describes the performance and cost benefits projected to result from the use of advanced Hall thrusters for deep space science missions.

Impulse-Momentum Diagrams

ERIC Educational Resources Information Center

Rosengrant, David

2011-01-01

Multiple representations are a valuable tool to help students learn and understand physics concepts. Furthermore, representations help students learn how to think and act like real scientists. These representations include: pictures, free-body diagrams, energy bar charts, electrical circuits, and, more recently, computer simulations and…

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.

TAL Performance and Mission Analysis in a CDL Capacitor Powered Direct-Drive Configuration

NASA Technical Reports Server (NTRS)

Hrbud, Ivana; Rose, M. Frank; Oleson, Steve R.; Jenkins, Rhonald M.

1999-01-01

The goals of this research are (1) to prove the concept feasibility of a direct-drive electric propulsion system, and (2) to evaluate the performance and characteristics of a Russian TAL (Thruster with Anode Layer) operating in a long-pulse mode, powered by a capacitor-based power source developed at Space Power Institute. The TAL, designated D-55, is characterized by an external acceleration zone and is powered by a unique chemical double layer (CDL) capacitor bank with a capacitance of 4 F at a charge voltage of 400 V. Performance testing of this power supply on the TAL was conducted at NASA Lewis Research Center in Cleveland, OH. Direct thrust measurements of the TAL were obtained at CDL power levels ranging from 450 to 1750 W. The specific impulse encompassed a range from 1150 s to 2200 s, yielding thruster system efficiencies between 50 and 60%. Preliminary mission analysis of the CDL direct-drive concept and other electric propulsion options was performed for the ORACLE spacecraft in 6am/6pm and 12am/12pm, 300 km sun-synchronous orbits. The direct-drive option was competitive with the other systems by increasing available net mass between 5 and 42% and reducing two-year system wet mass between 18 and 63%. Overall, the electric propulsion power requirements for the satellite solar array were reduced between 57 and 91% depending oil the orbit evaluated The direct-drive, CDL capacitor-based concept in electric propulsion thus promises to be a highly-efficient, viable alternative for satellite operations in specific near-Earth missions.

High-frequency vibration energy harvesting from impulsive excitation utilizing intentional dynamic instability caused by strong nonlinearity

NASA Astrophysics Data System (ADS)

Remick, Kevin; Dane Quinn, D.; Michael McFarland, D.; Bergman, Lawrence; Vakakis, Alexander

2016-05-01

The authors investigate a vibration-based energy harvesting system utilizing essential (nonlinearizable) nonlinearities and electromagnetic coupling elements. The system consists of a grounded, weakly damped linear oscillator (primary system) subjected to a single impulsive load. This primary system is coupled to a lightweight, damped oscillating attachment (denoted as nonlinear energy sink, NES) via a neodymium magnet and an inductance coil, and a piano wire, which generates an essential geometric cubic stiffness nonlinearity. Under impulsive input, the transient damped dynamics of this system exhibit transient resonance captures (TRCs) causing intentional large-amplitude and high-frequency instabilities in the response of the NES. These TRCs result in strong energy transfer from the directly excited primary system to the light-weight attachment. The energy is harvested by the electromagnetic elements in the coupling and, in the present case, dissipated in a resistive element in the electrical circuit. The primary goal of this work is to numerically, analytically, and experimentally demonstrate the efficacy of employing this type of intentional high-frequency dynamic instability to achieve enhanced vibration energy harvesting under impulsive excitation.

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.

Two Temperature Modeling and Experimental Measurements of Laser Sustained Hydrogen Plasmas

DTIC Science & Technology

1993-05-01

4 1.3 Theoretical Background .................................................................. 7 1.4...typically produce low specific impulses with an upper limit of approximately 450 seconds. The theoretical chamber temperature in such a system can be as...systems are theoretically capable of producing moderate thrusts (> 1 kN) with specific impulses in excess of 1000 seconds for 10 MW input power. This

Influence of process conditions during impulsed electrostatic droplet formation on size distribution of hydrogel beads.

PubMed

Lewińska, Dorota; Rosiński, Stefan; Weryński, Andrzej

2004-02-01

In the medical applications of microencapsulation of living cells there are strict requirements concerning the high size uniformity and the optimal diameter, the latter dependent on the kind of therapeutic application, of manufactured gel beads. The possibility of manufacturing small size gel bead samples (diameter 300 microm and below) with a low size dispersion (less than 10%), using an impulsed voltage droplet generator, was examined in this work. The main topic was the investigation of the influence of values of electric parameters (voltage U, impulse time tau and impulse frequency f) on the quality of obtained droplets. It was concluded that, owing to the implementation of the impulse mode and regulation of tau and f values, it is possible to work in a controlled manner in the jet flow regime (U> critical voltage UC). It is also possible to obtain uniform bead samples with the average diameter, deff, significantly lower than the nozzle inner diameter dI (bead diameters 0.12-0.25 mm by dI equal to 0.3 mm, size dispersion 5-7%). Alterations of the physical parameters of the process (polymer solution physico-chemical properties, flow rate, distance between nozzle and gellifying bath) enable one to manufacture uniform gel beads in the wide range of diameters using a single nozzle.

Radioisotope Electric Propulsion Centaur Orbiter Spacecraft Design Overview

NASA Technical Reports Server (NTRS)

Oleson, Steve; McGuire, Melissa; Sarver-Verhey, Tim; Juergens, Jeff; Parkey, Tom; Dankanich, John; Fiehler, Doug; Gyekenyesi, John; Hemminger, Joseph; Gilland, Jim;

Evaluation of High-Power Solar Electric Propulsion using Advanced Ion, Hall, MPD, and PIT Thrusters for Lunar and Mars Cargo Missions

NASA Technical Reports Server (NTRS)

Frisbee, Robert H.

2006-01-01

This paper presents the results of mission analyses that expose the advantages and disadvantages of high-power (MWe-class) Solar Electric Propulsion (SEP) for Lunar and Mars Cargo missions that would support human exploration of the Moon and Mars. In these analyses, we consider SEP systems using advanced Ion thrusters (the Xenon [Xe] propellant Herakles), Hall thrusters (the Bismuth [Bi] propellant Very High Isp Thruster with Anode Layer [VHITAL], magnetoplasmadynamic (MPD) thrusters (the Lithium [Li] propellant Advanced Lithium-Fed, Applied-field Lorentz Force Accelerator (ALFA2), and pulsed inductive thruster (PIT) (the Ammonia [NH3] propellant Nuclear-PIT [NuPIT]). The analyses include comparison of the advanced-technology propulsion systems (VHITAL, ALFA2, and NuPIT) relative to state-of-theart Ion (Herakles) propulsion systems and quantify the unique benefits of the various technology options such as high power-per-thruster (and/or high power-per-thruster packaging volume), high specific impulse (Isp), high-efficiency, and tankage mass (e.g., low tankage mass due to the high density of bismuth propellant). This work is based on similar analyses for Nuclear Electric Propulsion (NEP) systems.

A performance comparison of ultrasonically aided electric propulsion extractor configurations

NASA Astrophysics Data System (ADS)

Dong, L.; Song, W.; Kang, X. M.; Zhao, W. S.

2012-08-01

As a novel propulsion technology, ultrasonically aided electric propulsion (UAEP) offers a high specific impulse and a high thrust density. In this paper, the effects of extractor grid configuration on performance of a UAEP thruster have been investigated by both experimental studies and numerical simulation. Relationships between spray current and operation parameters, including applied voltage, propellant flow rate, and vibration power and frequency, are explored for different extractor mesh sizes and shapes. Numerical simulation is also carried out for a better understanding of the formation of capillary standing waves as well as the electric field distribution in the acceleration zone. Experimental results show that compared with a circular shaped extractor, a reticular shaped extractor is able to produce a higher spray current. The current density increases with a denser mesh, which agrees well with the numerical simulation results. This phenomenon indicates that optimizing extractors with appropriate shapes and sizes can be an effective way to improve the performance of a UAEP system. A performance evaluation based on hydrodynamic and electrostatic calculations indicates that the present UAEP system can produce a thrust competitive to that of the colloid thruster with an emitter array.

Expendable Launch Vehicles Briefing and Basic Rocketry Physics

NASA Technical Reports Server (NTRS)

Delgado, Luis G.

2010-01-01

This slide presentation is composed of two parts. The first part shows pictures of launch vehicles and lift offs or in the case of the Pegasus launch vehicle separations. The second part discusses the basic physics of rocketry, starting with Newton's three physical laws that form the basis for classical mechanics. It includes a review of the basic equations that define the physics of rocket science, such as total impulse, specific impulse, effective exhaust velocity, mass ratio, propellant mass fraction, and the equations that combine to arrive at the thrust of the rocket. The effect of atmospheric pressure is reviewed, as is the effect of propellant mix on specific impulse.

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

Effect of amplitude and duration of impulsive pressure on endothelial permeability in in vitro fluid percussion trauma.

PubMed

Nakadate, Hiromichi; Inuzuka, Koji; Akanuma, Suguru; Kakuta, Akira; Aomura, Shigeru

2014-04-16

Intracranial pressure changes during head impact cause brain injuries such as vasogenic edema and cerebral contusion. However, the influence of impulsive pressure on endothelial function has not yet been fully studied in vitro. In this study, we developed a pressure loading device that produced positive and negative pressures by modifying an in vitro fluid percussion model and examined the effects of the amplitude and duration of the pressures on endothelial permeability. Human umbilical vein endothelial cells were subjected to three types of positive pressure (average amplitude/average duration of 352 kPa/23 ms, 73 kPa/27 ms, and 70 kPa/44 ms) and three types of negative pressure (-72 kPa/41 ms, -67 kPa/104 ms, and -91 kPa/108 ms), and the transendothelial electrical resistance (TEER) was measured between 15 min and 24 h after pressure loading for quantifying the formation of an integral monolayer of endothelial cells. After loading, vascular endothelial- (VE-) cadherin, an endothelium-specific cell-cell adhesion molecule involved in endothelial barrier function, was stained and observed using fluorescence microscopy. The pressure loading device could produce positive pressure pulses with amplitudes of 53-1348 kPa and durations of 9-29.1 ms and negative pressure pulses with amplitudes of -52 - -93 kPa and durations of 42.9-179.5 ms. The impulsive pressure reduced the TEER associated with the change in VE-cadherin localization. Additionally, TEER decreased considerably at 15 min and 6 h post-loading, with these changes being significant in positive pressure with larger amplitude and shorter duration and in all types of negative pressures compared to pre-loading. The changes in intracranial pressure during head impact impair endothelial barrier function by the disruption of the integrity of endothelial cell-cell junctions, and the degree of increase in endothelial permeability depends on the amplitude, duration, and direction (compressive and tensile) of the impulsive pressure.

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.

Response of ionospheric electric fields at mid-low latitudes during geomagnetic sudden commencements

NASA Astrophysics Data System (ADS)

Takahashi, N.; Kasaba, Y.; Shinbori, A.; Nishimura, Y.; Kikuchi, T.; Ebihara, Y.; Nagatsuma, T.

2014-12-01

Geomagnetic sudden commencements (SCs) are known as one of the distinct magnetospheric disturbance phenomena triggered by solar wind disturbances. Many previous studies have focused on the generation mechanism of SCs by using in-situ observations and simulations. However, the global evolution of ionospheric electric fields has primarily been estimated from the ionospheric current. Although a few studies utilized electric field data from radar observations, the coverage is limited in time, and limited component of the electric field is obtained. In this study, we investigated the response and local time dependence of the ionospheric electric field at mid-low latitudes associated with 203 SCs occurred from 1999 to 2004 by the in-situ observation of the ROCSAT-1 spacecraft. We found that the ionospheric electric field associated with SCs instantaneously responds to geomagnetic fields regardless of spacecraft local time. Our statistical analysis also showed the instantaneous response of the electric field, which indicates the global instant transmission of the electric field from polar region. In contrast, peak times in the preliminary impulse (PI) and main impulse (MI) phases were different between the ionospheric electric field and equatorial geomagnetic field (20 sec in the PI phase). Based on a comparison to the ground-ionosphere waveguide model by Kikuchi [2014], this time lag is suggested to be due to the latitudinal difference of the ionospheric conductivity. After constructing the local time distribution of the SC amplitude, we found that the dayside feature was seen at 18-22 h even the ionospheric conductivity is lower than that at dayside. We performed a magnetohydrodynamic (MHD) simulation for an ideal SC. The result of the simulation showed that the electric potential distribution is asymmetric with respect to the noon-midnight meridian, which is similar to our observational result. It appears to result from the divergence of the Hall current under the non-uniform ionospheric conductivity near the terminator as well as the auroral region.

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.

Trajectory Optimization of an Interstellar Mission Using Solar Electric Propulsion

NASA Technical Reports Server (NTRS)

Kluever, Craig A.

1996-01-01

This paper presents several mission designs for heliospheric boundary exploration using spacecraft with low-thrust ion engines as the primary mode of propulsion The mission design goal is to transfer a 200-kg spacecraft to the heliospheric boundary in minimum time. The mission design is a combined trajectory and propulsion system optimization problem. Trajectory design variables include launch date, launch energy, burn and coast arc switch times, thrust steering direction, and planetary flyby conditions. Propulsion system design parameters include input power and specific impulse. Both SEP and NEP spacecraft arc considered and a wide range of launch vehicle options are investigated. Numerical results are presented and comparisons with the all chemical heliospheric missions from Ref 9 are made.

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.

Hall Propulsion Technology Development, NASA Glenn Research Center: 50 kW Thruster Technology EXPRESS Ground/Space Correlation

NASA Technical Reports Server (NTRS)

Jankovsky, Robert; Elliott, Fred

2000-01-01

It is the goal of this activity to develop 50 kW class Hall thruster technology in support of cost and time critical mission applications such as orbit insertion. NASA Marshall Space Flight Center is tasked to develop technologies that enable cost and travel time reduction of interorbital transportation. Therefore, a key challenge is development of moderate specific impulse (2000-3000 s), high thrust-to-power electric propulsion. NASA Glenn Research Center is responsible for development of a Hall propulsion system to meet these needs. First-phase, sub-scale Hall engine development completed. A 10 kW engine designed, fabricated, and tested. Performance demonstrated >2400 s, >500 mN thrust over 1000 hours of operation documented.

Guidance, Navigation, and Control Considerations for Nuclear Thermal Propulsion

NASA Technical Reports Server (NTRS)

Houts, Michael G.; Mitchell, Doyce P.; Kim, Tony

2015-01-01

The fundamental capability of Nuclear Thermal Propulsion (NTP) is game changing for space exploration. A first generation NTP system could provide high thrust at a specific impulse above 900 s, roughly double that of state of the art chemical engines. Characteristics of fission and NTP indicate that useful first generation systems will provide a foundation for future systems with extremely high performance. The role of a first generation NTP in the development of advanced nuclear propulsion systems could be analogous to the role of the DC-3 in the development of advanced aviation. Progress made under the NTP project could also help enable high performance fission power systems and Nuclear Electric Propulsion (NEP). Guidance, navigation, and control of NTP may have some unique but manageable characteristics.

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

Large-eddy simulation, atmospheric measurement and inverse modeling of greenhouse gas emissions at local spatial scales

NASA Astrophysics Data System (ADS)

Nottrott, Anders Andelman

Multiferroic materials and devices have attracted intensified interests due to the demonstrated strong magnetoelectric coupling in new multiferroic materials, artificial multiferroic heterostructures and devices with unique functionalities and superior performance characteristics. This offers great opportunities for achieving compact, fast, energy-efficient and voltage tunable spintronic devices. In traditional magnetic materials based magnetic random access memories (MRAM) devices, the binary information is stored as magnetization. The high coercivity of the ferromagnetic media requires large magnetic fields for switching the magnetic states thus consuming large amount of energy. In modern MRAM information writing process, spin-torque technique is utilized for minimizing the large energy for generating magnetic field by passing through a spin-polarized current directly to the magnets. However, both methods still need large current/current density to toggle the magnetic bits which consume large amount of energy. With the presence of multiferroic or magnetoelectric materials, spin is controlled by electric field which opens new opportunities for power-efficient voltage control of magnetization in spintronic devices leading to magnetoelectric random access memories (MERAM) with ultra-low energy consumption. However, state of the art multiferroic materials still have difficulty of realizing nonvolatile 180° magnetization reversal, which is desired in realizing MERAM. In a strain-mediated multiferroic system, the typical modification of the magnetism of ferromagnetic phase as a function of bipolar electric field shows a "butterfly" like behavior. This is due to the linear piezoelectricity of ferroelectric phase which has a "butterfly" like piezostrain as a function of electric field curve resulting from ferroelectric domain wall switching. In this case, the magnetization state is volatile because of the vanishing of the piezostrain at zero electric field. However, the non-volatile switching of magnetization would be more promising for information storage or MERAM devices with lower energy consumption and the magnetic state can be further controlled by voltage impulse. In this work, we first study the equivalent of direct and converse magnetoelectric effects. The resonant direct and converse magnetoelectric (ME) effects have been investigated experimentally and theoretically in FeGa/PZT/FeGa sandwich laminate composites. The frequency responses of direct and converse magnetoelectric effects were measured under the same electric and magnetic bias conditions. The resonant direct ME effect (DME) occurs at an antiresonance frequency, while resonant converse ME effect (CME) occurs at a resonance frequency. The antiresonance and resonance frequencies have close but different values under identical bias conditions. The magnitudes of resonant effective ME coefficients for direct and converse ME effects are also not equal. Based on different sets of constitutive equations of the materials for DME and CME, a new model was developed to describe the frequency response of DME and CME in laminate composite, which was in good agreement with the experimental results. Inequivalence of resonant ME effects is ascribed to the different mechanical and electrical boundary conditions for DME and CME. On the other hand, similar bias E and H field dependence was observed for both DME and CME resonance frequencies and resonant coefficients, indicating consistency between DME and CME effects. In the study of the frequency response of DME and CME, the linear piezoelectric effect is used. However, this linear piezoelectric effect in converse magnetoelectric coupling would lead to "butter-fly" like magnetization vs. electric field curve which leads to a "volatile" behavior in magnetic memory system. In the presented study, a unique ferroelastic switching pathway in ferroelectric substrates is utilized to produce two distinct, reversible and stable lattice strain states which leads to the establish of two stable magnetization states of the ferromagnetic thin film. In this process, instead of complete 180° ferromagnetic domain switching, 71°/109° ferroelastic domain wall switching is involved, where the electric polarization is switching between in-plane and out-of-plane direction. A voltage impulse induced reversible bistable magnetization switching in FeGaB/lead zirconate titanate (PZT) multiferroic heterostructures at room temperature is first demonstrated. Two reversible and stable voltage-impulse induced mechanical strain states were obtained in the PZT by applying an electric field impulse with its amplitude smaller than the electric coercive field, which led to reversible voltage impulse induced bistable magnetization switching. Direct and converse magnetoelectric effects are carefully quantified.

An Impulse Electric Motor for Driving Recording Instruments

NASA Technical Reports Server (NTRS)

Joachim, W F

1923-01-01

The chief purpose in undertaking the development of this synchronous motor was the creation of a very small, compact power source, capable of driving the film drums of the recording aircraft instruments designed by the staff of the National Advisory Committee for Aeronautics.

Modeling Study of the Geospace System Response to the Solar Wind Dynamic Pressure Enhancement on 17 March 2015

NASA Astrophysics Data System (ADS)

Ozturk, D. S.; Zou, S.; Ridley, A. J.; Slavin, J. A.

2018-04-01

The global magnetosphere-ionosphere-thermosphere system is intrinsically coupled and susceptible to external drivers such as solar wind dynamic pressure enhancements. In order to understand the large-scale dynamic processes in the magnetosphere-ionosphere-thermosphere system due to the compression from the solar wind, the 17 March 2015 sudden commencement was studied in detail using global numerical models. This storm was one of the most geoeffective events of the solar cycle 24 with a minimum Dst of -222 nT. The Wind spacecraft recorded a 10-nPa increment in the solar wind dynamic pressure, while the interplanetary magnetic field BZ became further northward. The University of Michigan Block-Adaptive-Tree Solar wind Roe-type Upwind Scheme global magnetohydrodynamic code was utilized to study the generation and propagation of perturbations associated with the compression of the magnetosphere system. In addition, the high-resolution electric potential and auroral power output from the magnetohydrodynamic model was used to drive the global ionosphere-thermosphere model to investigate the ionosphere-thermosphere system response to pressure enhancement. During the compression, the electric potentials and convection patterns in the polar ionosphere were significantly altered when the preliminary impulse and main impulse field-aligned currents moved from dayside to nightside. As a result of enhanced frictional heating, plasma and neutral temperatures increased at the locations where the flow speeds were enhanced, whereas the electron density dropped at these locations. In particular, the region between the preliminary impulse and main impulse field-aligned currents experienced the most significant heating with 1000-K ion temperature increase and 20-K neutral temperature increase within 2 min. Comparison of the simulation results with the Poker Flat Incoherent Scatter Radar observations showed reasonable agreements despite underestimated magnitudes.

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.

ESCORT: A Pratt & Whitney nuclear thermal propulsion and power system for manned mars missions

NASA Astrophysics Data System (ADS)

Feller, Gerald J.; Joyner, Russell

1999-01-01

The purpose of this paper is to describe the conceptual design of an upgrade to the Pratt & Whitney ESCORT nuclear thermal rocket engine. The ESCORT is a bimodal engine capable of supporting a wide range of vehicle propulsive and electrical power requirements. The ESCORT engine is powered by a fast-spectrum beryllium-reflected CERMET-fueled nuclear reactor. In propulsive mode, the reactor is used to heat hot hydrogen to approximately 2700 K which is expanded through a converging/diverging nozzle to generate thrust. Heat pickup in the nozzle and the radial beryllium reflectors is used to drive the turbomachinery in the ESCORT expander cycle. In electrical mode, the reactor is used to heat a mixture of helium and xenon to drive a closed-loop Brayton cycle in order to generate electrical energy. This closed loop system has the additional function of a decay heat removal system after the propulsive mode operation is discontinued. The original ESCORT design was capable of delivering 4448.2 N (1000 lbf) of thrust at a vacuum impulse level of approximately 900 s. Design Reference Mission requirements (DRM) from NASA Johnson Space Center and NASA Lewis Research Center studies in 1997 and 1998 have detailed upgraded requirements for potential manned Mars missions. The current NASA DRM requires a nuclear thermal propulsion system capable of delivering total mission requirements of 200170 N (45000 lbf) thrust and 50 kWe of spacecraft electrical power. This is met assuming three engines capable of each delivering 66723 N (15000 lbf) of vacuum thrust and 25 kWe of electrical power. The individual engine requirements were developed assuming three out of three engine reliability for propulsion and two out of three engine reliability for spacecraft electrical power. The approximate target vacuum impulse is 925 s. The Pratt & Whitney ESCORT concept was upgraded to meet these requirements. The hexagonal prismatic fuel elements were modified to address the uprated power requirements while maintaining the peak fuel temperature below the 2880 K limit for W-UO2 CERMET fuels. A system integrated performance methodology was developed to assess the sensitivity to weight, thrust and impulse to the DRM requirements. Propellant tanks, shielding, and Brayton cycle power conversion unit requirements were included in this evaluation.

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.

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.

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

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.

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

An application area of C60: Overall improvement of insulating oil's electrical performance

NASA Astrophysics Data System (ADS)

Sun, Potao; Sima, Wenxia; Chen, Jiaqi; Zhang, Dingfei; Jiang, Xiongwei; Chen, Qiulin

2018-04-01

We prepared nano-C60 based insulating oil, which has the potential to overcome the application barriers of nanomodified insulating oil. We find that nano-C60 based insulating oil has an excellent stability. Its electrical performance increases by 17.9%, 9.3%, and 8.3% for AC and positive/negative lightning impulse voltage, respectively. We believe that C60 molecules have a strong capacity to absorb electrons and can capture photons in a streamer, which may weaken photoionization in the streamer and thereby improve the electrical performance of insulating oil.

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

Electric Propulsion Options for 10 kW Class Earth-Space Missions

NASA Technical Reports Server (NTRS)

Patterson, M. J.; Curran, Francis M.

1989-01-01

Five and 10 kW ion and arcjet propulsion system options for a near-term space demonstration experiment were evaluated. Analyses were conducted to determine first-order propulsion system performance and system component mass estimates. Overall mission performance of the electric propulsion systems was quantified in terms of the maximum thrusting time, total impulse, and velocity increment capability available when integrated onto a generic spacecraft under fixed mission model assumptions. Maximum available thrusting times for the ion-propelled spacecraft options, launched on a DELTA 2 6920 vehicle, range from approximately 8,600 hours for a 4-engine 10 kW system to more than 29,600 hours for a single-engine 5 kW system. Maximum total impulse values and maximum delta-v's range from 1.2x10 (exp 7) to 2.1x10 (exp 7) N-s, and 3550 to 6200 m/s, respectively. Maximum available thrusting times for the arcjet propelled spacecraft launched on the DELTA 2 6920 vehicle range from approximately 528 hours for the 6-engine 10 kW hydrazine system to 2328 hours for the single-engine 5 kW system. Maximum total impulse values and maximum delta-v's range from 2.2x10 (exp 6) to 3.6x10 (exp 6) N-s, and approximately 662 to 1072 m/s, respectively.

High-Energy Space Propulsion Based on Magnetized Target Fusion

NASA Technical Reports Server (NTRS)

Thio, Y. C. F.; Freeze, B.; Kirkpatrick, R. C.; Landrum, B.; Gerrish, H.; Schmidt, G. R.

1999-01-01

A conceptual study is made to explore the feasibility of applying magnetized target fusion (MTF) to space propulsion for omniplanetary travel. Plasma-jet driven MTF not only is highly amenable to space propulsion, but also has a number of very attractive features for this application: 1) The pulsed fusion scheme provides in situ a very dense hydrogenous liner capable of moderating the neutrons, converting more than 97% of the neutron energy into charged particle energy of the fusion plasma available for propulsion. 2) The fusion yield per pulse can be maintained at an attractively low level (< 1 GJ) despite a respectable gain in excess of 70. A compact, low-weight engine is the result. An engine with a jet power of 25 GW, a thrust of 66 kN, and a specific impulse of 77,000 s, can be achieved with an overall engine mass of about 41 metric tons, with a specific power density of 605 kW/kg, and a specific thrust density of 1.6 N/kg. The engine is rep-rated at 40 Hz to provide this power and thrust level. At a practical rep-rate limit of 200 Hz, the engine can deliver 128 GW jet power and 340 kN of thrust, at specific power and thrust density of 1,141 kW/kg and 3 N/kg respectively. 3) It is possible to operate the magnetic nozzle as a magnetic flux compression generator in this scheme, while attaining a high nozzle efficiency of 80% in converting the spherically radial momentum of the fusion plasma to an axial impulse. 4) A small fraction of the electrical energy generated from the flux compression is used directly to recharge the capacitor bank and other energy storage equipment, without the use of a highvoltage DC power supply. A separate electrical generator is not necessary. 5) Due to the simplicity of the electrical circuit and the components, involving mainly inductors, capacitors, and plasma guns, which are connected directly to each other without any intermediate equipment, a high rep-rate (with a maximum of 200 Hz) appears practicable. 6) All fusion related components are within the current state of the art for pulsed power technology. Experimental facilities with the required pulsed power capabilities already exist. 7) The scheme does not require prefabricated fuel target and liner hardware in any esoteric form or state. All necessary fuel and liner material are introduced into the engine in the form of ordinary matter in gaseous state at room temperature, greatly simplifying their handling on board. They are delivered into the fusion reaction chamber in a completely standoff manner.

Human Aquaporin 4 Gating Dynamics under Perpendicularly-Oriented Electric-Field Impulses: A Molecular Dynamics Study

PubMed Central

Marracino, Paolo; Liberti, Micaela; Trapani, Erika; Burnham, Christian J.; Avena, Massimiliano; Garate, José-Antonio; Apollonio, Francesca; English, Niall J.

2016-01-01

Human aquaporin 4 has been studied using molecular dynamics (MD) simulations in the absence and presence of pulses of external static electric fields. The pulses were 10 ns in duration and 0.012–0.065 V/Å in intensity acting along both directions perpendicular to the pores. Water permeability and the dipolar response of all residues of interest (including the selectivity filter) within the pores have been studied. Results showed decreased levels of water osmotic permeability within aquaporin channels during orthogonally-oriented field impulses, although care must be taken with regard to statistical certainty. This can be explained observing enhanced “dipolar flipping” of certain key residues, especially serine 211, histidine 201, arginine 216, histidine 95 and cysteine 178. These residues are placed at the extracellular end of the pore (serine 211, histidine 201, and arginine 216) and at the cytoplasm end (histidine 95 and cysteine 178), with the key role in gating mechanism, hence influencing water permeability. PMID:27428954

ELECTRICAL LOAD ANTICIPATOR AND RECORDER

DOEpatents

Russell, J.B.; Thomas, R.J.

1961-07-25

A system is descrbied in which an indication of the prevailing energy consumption in an electrical power metering system and a projected Power demand for one demand interval is provided at selected increments of time withm the demand interval. Each watthour meter in the system is provided with an impulse generator that generates two impulses for each revolution of the meter disc. The total pulses received frorn all the meters are continuously totaled and are fed to a plurality of parallel connected gated counters. Each counter has its gate opened at different sub-time intervals during the demand interval. A multiplier is connected to each of the gated counters except the last one and each multiplier is provided with a different multiplier constant so as to provide an estimate of the power to be drawn over the entire demand interval at the end of each of the different sub-time intervals. Means are provided for recording the ontputs from the different circuits in synchronism with the actuation oi each gate circuit.

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).

Drifting potential humps in ionization zones: The “propeller blades” of high power impulse magnetron sputtering

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

Anders, André; Ni, Pavel; Panjan, Matjaž

2013-09-30

Ion energy distribution functions measured for high power impulse magnetron sputtering show features, such as a broad peak at several 10 eV with an extended tail, as well as asymmetry with respect to E×B, where E and B are the local electric and magnetic field vectors, respectively. Here it is proposed that those features are due to the formation of a potential hump of several 10 V in each of the traveling ionization zones. Potential hump formation is associated with a negative-positive-negative space charge that naturally forms in ionization zones driven by energetic drifting electrons.

High power impulse magnetron sputtering and its applications

NASA Astrophysics Data System (ADS)

Yan, YUAN; Lizhen, YANG; Zhongwei, LIU; Qiang, CHEN

2018-04-01

High power impulse magnetron sputtering (HiPIMS) has attracted a great deal of attention because the sputtered material is highly ionized during the coating process, which has been demonstrated to be advantageous for better quality coating. Therefore, the mechanism of the HiPIMS technique has recently been investigated. In this paper, the current knowledge of HiPIMS is described. We focus on the mechanical properties of the deposited thin film in the latest applications, including hard coatings, adhesion enhancement, tribological performance, and corrosion protection layers. A description of the electrical, optical, photocatalytic, and functional coating applications are presented. The prospects for HiPIMS are also discussed in this work.

Determination of threshold and maximum operating electric stresses for selected high voltage insulations. Task 2: Investigation of oil-filled paper insulated cables

NASA Astrophysics Data System (ADS)

Sosnowski, M.; Eager, G. S., Jr.

1983-06-01

Threshold voltage of oil-impregnated paper insulated cables are investigaed. Experimental work was done on model cables specially manufactured for this project. The cables were impregnated with mineral and with synthetic oils. Standard impulse breakdown voltage tests and impulse voltage breakdown tests with dc prestressing were performed at room temperature and at 1000C. The most important result is the finding of very high level of threshold voltage stress for oil-impregnated paper insulated cables. This threshold voltage is approximately 1.5 times higher than the threshold voltage or crosslinked polyethylene insulated cables.

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.

Regional United States electric field and GIC hazard impacts (Invited)

NASA Astrophysics Data System (ADS)

Gannon, J. L.; Balch, C. C.; Trichtchenko, L.

2013-12-01

Geomagnetically Induced Currents (GICs) are primarily driven by impulsive geomagnetic disturbances created by the interaction between the Earth's magnetosphere and sharp velocity, density, and magnetic field enhancements in the solar wind. However, the magnitude of the induced electric field response at the ground level, and therefore the resulting hazard to the bulk power system, is determined not only by magnetic drivers, but also by the underlying geology. Convolution techniques are used to calculate surface electric fields beginning from the spectral characteristics of magnetic field drivers and the frequency response of the local geology. Using these techniques, we describe historical scenarios for regions across the United States, and the potential impact of large events on electric power infrastructure.

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.

Electromagnetic panel deployment and retraction using the geomagnetic field in LEO satellite missions

NASA Astrophysics Data System (ADS)

Inamori, Takaya; Sugawara, Yoshiki; Satou, Yasutaka

2015-12-01

Increasingly, spacecraft are installed with large-area structures that are extended and deployed post-launch. These extensible structures have been applied in several missions for power generation, thermal radiation, and solar propulsion. Here, we propose a deployment and retraction method using the electromagnetic force generated when the geomagnetic field interacts with electric current flowing on extensible panels. The panels are installed on a satellite in low Earth orbit. Specifically, electrical wires placed on the extensible panels generate magnetic moments, which interfere with the geomagnetic field. The resulting repulsive and retraction forces enable panel deployment and retraction. In the proposed method, a satellite realizes structural deployment using simple electrical wires. Furthermore, the satellite can achieve not only deployment but also retraction for avoiding damage from space debris and for agile attitude maneuvers. Moreover, because the proposed method realizes quasi-static deployment and the retraction of panels by electromagnetic forces, low impulsive force is exerted on fragile panels. The electrical wires can also be used to detect the panel deployment and retraction and generate a large magnetic moment for attitude control. The proposed method was assessed in numerical simulations based on multibody dynamics. Simulation results shows that a small cubic satellite with a wire current of 25 AT deployed 4 panels (20 cm × 20 cm) in 500 s and retracted 4 panels in 100 s.

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.

Implementation of a Low-Thrust Trajectory Optimization Algorithm for Preliminary Design

NASA Technical Reports Server (NTRS)

Sims, Jon A.; Finlayson, Paul A.; Rinderle, Edward A.; Vavrina, Matthew A.; Kowalkowski, Theresa D.

2006-01-01

A tool developed for the preliminary design of low-thrust trajectories is described. The trajectory is discretized into segments and a nonlinear programming method is used for optimization. The tool is easy to use, has robust convergence, and can handle many intermediate encounters. In addition, the tool has a wide variety of features, including several options for objective function and different low-thrust propulsion models (e.g., solar electric propulsion, nuclear electric propulsion, and solar sail). High-thrust, impulsive trajectories can also be optimized.

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

An Overview of the CNES Propulsion Program for Spacecraft

NASA Astrophysics Data System (ADS)

Cadiou, A.; Darnon, F.; Gibek, I.; Jolivet, L.; Pillet, N.

2004-10-01

This paper presents an overview of the CNES spacecraft propulsion activities. The main existing and future projects corresponding to low earth orbit and geostationary platforms are described. These projects cover various types of propulsion subsystems: monopropellant, bipropellant and electric. Monopropellant is mainly used for low earth orbit applications such as earth observation (SPOT/Helios, PLEIADES) or scientific applications (minisatellite PROTEUS line and micro satellites MYRIADE line). Bipropellant is used for geostationary telecommunications satellites (@BUS). The field of application of electric propulsion is the station keeping of geostationary telecommunication satellites (@BUS), main propulsion for specific probes (SMART 1) and fine attitude control for dedicated micro satellites (MICROSCOPE). The preparation of the future and the associated Research and Technology program are also described in the paper. The future developments are mainly dedicated to the performance improvements of electric propulsion which leads to the development of thrusters with higher thrust and higher specific impulse than those existing today, the evaluation of the different low thrust technologies for formation flying applications, the development of new systems to pressurize the propellants (volatile liquid, micro pump), the research on green propellants and different actions concerning components such as over wrapped pressure vessels, valves, micro propulsion. A constant effort is also put on plume effect in chemical and electrical propulsion area (improvement of tools and test activities) in the continuity of the previous work. These different R &T activities are described in detail after a presentation of the different projects and of their propulsion subsystems. The scientific activity supporting the development of Hall thrusters is going on in the frame of the GDR (Groupement de Recherche) CNRS / Universities / CNES / SNECMA on Plasma Propulsion.

Electric Field Simulation of Surge Capacitors with Typical Defects

NASA Astrophysics Data System (ADS)

Zhang, Chenmeng; Mao, Yuxiang; Xie, Shijun; Zhang, Yu

2018-03-01

The electric field of power capacitors with different typical defects in DC working condition and impulse oscillation working condition is studied in this paper. According to the type and location of defects and considering the influence of space charge, two-dimensional models of surge capacitors with different typical defects are simulated based on ANSYS. The distribution of the electric field inside the capacitor is analyzed, and the concentration of electric field and its influence on the insulation performance are obtained. The results show that the type of defects, the location of defects and the space charge all affect the electric field distribution inside the capacitor in varying degrees. Especially the electric field distortion in the local area such as sharp corners and burrs is relatively larger, which increases the probability of partial discharge inside the surge capacitor.

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

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

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

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.

A Plasma Rocket Demonstration on the International Space Station

NASA Astrophysics Data System (ADS)

Petro, A.

2002-01-01

in the development of a magneto-plasma rocket for several years. This type of rocket could be used in the future to propel interplanetary spacecraft. One feature of this concept is the ability to vary its specific impulse so that it can be operated in a mode that maximizes propellant efficiency or a mode that maximizes thrust. For this reason the system is called the Variable Specific Impulse Magneto-plasma Rocket or VASIMR. This ability to vary specific impulse and thrust will allow for optimum low thrust interplanetary trajectories and results in shorter trip times than is possible with fixed specific impulse systems while preserving adequate payload margins. demonstrations are envisioned. A ground-based experiment of a low-power VASIMR prototype rocket is currently underway at the Advanced Space Propulsion Laboratory. The next step is a proposal to build and fly a 25-kilowatt VASIMR rocket as an external payload on the International Space Station. This experiment will provide an opportunity to demonstrate the performance of the rocket in space and measure the induced environment. The experiment will also utilize the space station for its intended purpose as a laboratory with vacuum conditions that cannot be matched by any laboratory on Earth. propulsion on the space station. An electric propulsion system like VASIMR, if provided with sufficient electrical power, could provide continuous drag force compensation for the space station. Drag compensation would eliminate the need for reboosting the station, an operation that will consume about 60 metric tons of propellant in a ten-year period. In contrast, an electric propulsion system would require very little propellant. In fact, a system like VASIMR can use waste hydrogen from the station's life support system as its propellant. This waste hydrogen is otherwise dumped overboard. Continuous drag compensation would also improve the microgravity conditions on the station. So electric propulsion can reduce propellant delivery requirements and thereby increase available payload capacity and at the same time improve the conditions for scientific research. and the space environment. This is a beneficial effect that prevents a charge buildup on the station. The station already operates two dedicated non-propulsive plasma contactor devices for this purpose. A VASIMR rocket would function as an additional plasma contactor. would be delivered to orbit in the Space Shuttle payload bay. It would be mounted on a standard payload attachment structure. After removal from the payload bay by the shuttle robotic arm, it would be handed to the space station robotic arm which would place it at an external payload attach site on the station truss. A mating device for power and data connections exists at the payload site. The experiment would receive one to three kilowatts of power from the station. About 600 watts would be used for cryogenic cooling and control devices. Additional power would be stored in a set of batteries. The VASIMR experiment would be operated for short periods when the batteries can provide power to the amplifiers that feed radio-frequency power to the thruster assembly. The thruster assembly is composed of an inner tube in which the neutral propellant is injected and ionized and a larger tube, which supports the radio frequency antennas, which ionize the gas and heat the plasma. Electromagnet coils that provide the magnetic field to constrain the flow of the plasma and form the magnetic exit nozzle surround these tubes. to this supply are planned for the experiment. The experiment will carry two dedicated propellant tanks which each have the capacity to store all the propellant needed for an experimental program lasting several months. With two propellant tanks, the opportunity exists to perform experiments with more than one type of propellant. Hydrogen is the primary choice for propellant but deuterium and helium are also of interest and might also be included. All the propellant is stored and used in gaseous form at ambient temperature. rocket. There is a superconducting electromagnet that will need to be maintained at cryogenic temperatures in order to operate properly. The magnet is in close proximity to the plasma so a combination of compact insulation and passive and active heat transport techniques will be employed. activity requirements. However, provisions will be included to capitalize on the presence of humans in case repairs or servicing is required. The batteries, propellant tanks, and electronic components will be designed for on-orbit removal and replacement, if necessary. could be located on the station to provide useful thrust for drag compensation. In order to provide power for continuous thrusting, it may be necessary to augment the power generation system for the station. Another attractive possibility is to develop an electric propulsion testbed for the space station. This testbed could be used for testing and certifying a variety of propulsion systems at various stages of maturity while providing thrust for the space station. This station facility would be a valuable asset for commercial and government space transportation programs. more powerful and capable propulsion systems that will be demonstrated on free-flying spacecraft in near-Earth space and eventually on missions to the planets.

Thought for Food

NASA Technical Reports Server (NTRS)

1977-01-01

Key to the integral heating system's efficiency is the "dish-oven", which doubles as a heating unit and serving plate. The dish-oven consists of a sealing frame (top) a plastic outer shell (center) and the ceramic inner dish. A special coating on the bottom of the inner dish transforms electrical impulses into heat

From Synaptic Transmission to Cognition: An Intermediary Role for Dendritic Spines

ERIC Educational Resources Information Center

Gonzalez-Burgos, Ignacio

2012-01-01

Dendritic spines are cytoplasmic protrusions that develop directly or indirectly from the filopodia of neurons. Dendritic spines mediate excitatory neurotransmission and they can isolate the electrical activity generated by synaptic impulses, enabling them to translate excitatory afferent information via several types of plastic changes, including…

Multi-Kilowatt Power Module for High-Power Hall Thrusters

NASA Technical Reports Server (NTRS)

Pinero, Luis R.; Bowers, Glen E.

2005-01-01

Future NASA missions will require high-performance electric propulsion systems. Hall thrusters are being developed at NASA Glenn for high-power, high-specific impulse operation. These thrusters operate at power levels up to 50 kW of power and discharge voltages in excess of 600 V. A parallel effort is being conducted to develop power electronics for these thrusters that push the technology beyond the 5kW state-of-the-art power level. A 10 kW power module was designed to produce an output of 500 V and 20 A from a nominal 100 V input. Resistive load tests revealed efficiencies in excess of 96 percent. Load current share and phase synchronization circuits were designed and tested that will allow connecting multiple modules in parallel to process higher power.

Heliocentric interplanetary low thrust trajectory optimization program, supplement 1, part 2

NASA Technical Reports Server (NTRS)

Mann, F. I.; Horsewood, J. L.

1978-01-01

The improvements made to the HILTOP electric propulsion trajectory computer program are described. A more realistic propulsion system model was implemented in which various thrust subsystem efficiencies and specific impulse are modeled as variable functions of power available to the propulsion system. The number of operating thrusters are staged, and the beam voltage is selected from a set of five (or less) constant voltages, based upon the application of variational calculus. The constant beam voltages may be optimized individually or collectively. The propulsion system logic is activated by a single program input key in such a manner as to preserve the HILTOP logic. An analysis describing these features, a complete description of program input quantities, and sample cases of computer output illustrating the program capabilities are presented.

Motor impulsivity in APP-SWE mice: a model of Alzheimer's disease.

PubMed

Adriani, Walter; Ognibene, Elisa; Heuland, Emilie; Ghirardi, Orlando; Caprioli, Antonio; Laviola, Giovanni

2006-09-01

Among transgenic mouse models of Alzheimer's disease, APP-SWE mice have been shown to develop beta-amyloid plaques and to exhibit progressive impairment of cognitive function. Human Alzheimer's disease, however, also includes secondary clinical manifestations, spanning from hyperactivity to agitation. The aim of this study was a better characterization of motor impulsivity in APP-SWE mice, observed at 12 months of age, when levels of soluble beta-amyloid are elevated and beta-amyloid neuritic plaques start to appear. Mice were tested for spatial learning abilities in the Morris water maze (seven daily sessions, four trials per day). The distance traveled to reach the hidden platform showed a learning curve in both groups. This profile, however, was somewhat delayed in APP-SWE mice, thus confirming slightly impaired spatial capacities. To evaluate motor impulsivity, animals were trained to nose-poke for a food reward, which was delivered after a waiting interval that increased over days (15-60 s). Further nose-poking during this signaled waiting interval resulted in food-reward loss and electric-shock punishment. APP-SWE mice received an increased quantity of punishment and were able to earn fewer food rewards, suggesting inability to wait already at the lowest delay. After the animals were killed, prefrontal cortex samples were assessed for neurochemical parameters. Serotonin turnover was elevated in the prefrontal cortex of APP-SWE mice compared with controls. The results clearly confirm cognitive deficits, and are consistent with the hypothesis of reduced behavioral-inhibition abilities. Together with recent findings, APP-SWE mice emerge as a suitable animal model, characterized by a number of specific behavioral alterations, resembling primary and secondary symptoms of human Alzheimer's disease.

Assessment of deep tissue hyperalgesia in the groin - a method comparison of electrical vs. pressure stimulation.

PubMed

Aasvang, E K; Werner, M U; Kehlet, H

2014-09-01

Deep pain complaints are more frequent than cutaneous in post-surgical patients, and a prevalent finding in quantitative sensory testing studies. However, the preferred assessment method - pressure algometry - is indirect and tissue unspecific, hindering advances in treatment and preventive strategies. Thus, there is a need for development of methods with direct stimulation of suspected hyperalgesic tissues to identify the peripheral origin of nociceptive input. We compared the reliability of an ultrasound-guided needle stimulation protocol of electrical detection and pain thresholds to pressure algometry, by performing identical test-retest sequences 10 days apart, in deep tissues in the groin region. Electrical stimulation was performed by five up-and-down staircase series of single impulses of 0.04 ms duration, starting from 0 mA in increments of 0.2 mA until a threshold was reached and descending until sensation was lost. Method reliability was assessed by Bland-Altman plots, descriptive statistics, coefficients of variance and intraclass correlation coefficients. The electrical stimulation method was comparable to pressure algometry regarding 10 days test-retest repeatability, but with superior same-day reliability for electrical stimulation (P < 0.05). Between-subject variance rather than within-subject variance was the main source for test variation. There were no systematic differences in electrical thresholds across tissues and locations (P > 0.05). The presented tissue-specific direct deep tissue electrical stimulation technique has equal or superior reliability compared with the indirect tissue-unspecific stimulation by pressure algometry. This method may facilitate advances in mechanism based preventive and treatment strategies in acute and chronic post-surgical pain states. © 2014 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

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.

High Power Ion Cyclotron Heating in the VASIMR

NASA Astrophysics Data System (ADS)

Longmier, B. W.; Brukardt, M. S.; Bering, E. A.; Chang Diaz, F.; Squire, J.

2009-12-01

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR®) is an electric propulsion system under development at Ad Astra Rocket Company that utilizes several processes of ion acceleration and heating that occur in the Birkeland currents of an auroral arc system. Among these processes are parallel electric field acceleration, lower hybrid resonance heating, and ion cyclotron resonance heating. The VASIMR® is capable of laboratory simulation of electromagnetic ion cyclotron wave heating during a single pass of ions through the resonance region. The plasma is generated by a helicon discharge of 35 kW then passes through a 176 kW RF booster stage that couples left hand polarized slow mode waves from the high field side of the resonance. VX-200 auroral simulation results from the past year are discussed. Ambipolar acceleration has been shown to produce 35eV argon ions in the helicon exhaust. The effects on the ion exhaust with an addition of 150-200 kW of ion cyclotron heating are presented. The changes to the VASIMR® experiment at Ad Astra Rocket Company's new facility in Webster, Texas will also be discussed, including the possibility of collaborative experiments.

Ion Cyclotron Waves in the VASIMR

NASA Astrophysics Data System (ADS)

Brukardt, M. S.; Bering, E. A.; Chang-Diaz, F. R.; Squire, J. P.; Longmier, B.

2008-12-01

The Variable Specific Impulse Magnetoplasma Rocket is an electric propulsion system under development at Ad Astra Rocket Company that utilizes several processes of ion acceleration and heating that occur in the Birkeland currents of an auroral arc system. Among these processes are parallel electric field acceleration, lower hybrid resonance heating, and ion cyclotron resonance heating. The VASIMR is capable of laboratory simulation of electromagnetic ion cyclotron wave heating during a single pass of the plasma through the resonance region. The plasma is generated by a helicon discharge of about 25 kW then passes through an RF booster stage that shoots left hand polarized slow mode waves from the high field side of the resonance. This paper will focus on the upgrades to the VX-200 test model over the last year. After summarizing the VX- 50 and VX-100 results, the new data from the VX-200 model will be presented. Lastly, the changes to the VASIMR experiment due to Ad Astra Rocket Company's new facility in Webster, Texas will also be discussed, including the possibility of collaborative experiments at the new facility.

Plasma Oscillation Characterization of NASA's HERMeS Hall Thruster via High Speed Imaging

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Kamhawi, Hani; Haag, Thomas W.

2016-01-01

For missions beyond low Earth orbit, spacecraft size and mass can be dominated by onboard chemical propulsion systems and propellants that may constitute more than 50 percent of the spacecraft mass. This impact can be substantially reduced through the utilization of Solar Electric Propulsion (SEP) due to its substantially higher specific impulse. Studies performed for NASA's Human Exploration and Operations Mission Directorate and Science Mission Directorate have demonstrated that a 50kW-class SEP capability can be enabling for both near term and future architectures and science missions. A high-power SEP element is integral to the Evolvable Mars Campaign, which presents an approach to establish an affordable evolutionary human exploration architecture. To enable SEP missions at the power levels required for these applications, an in-space demonstration of an operational 50kW-class SEP spacecraft has been proposed as a SEP Technology Demonstration Mission (TDM). In 2010 NASA's Space Technology Mission Directorate (STMD) began developing high-power electric propulsion technologies. The maturation of these critical technologies has made mission concepts utilizing high-power SEP viable.

Scaling of the VASIMR thruster first stage operation

NASA Astrophysics Data System (ADS)

Molvig, Kim; Batishchev, Oleg

2002-11-01

An effective helicon plasma source [1,2] is used in the variable high specific impulse VASIMR plasma thruster [3]. Experimental prototypes - VX-3 and recently up-scaled VX-10 [4] configurations operate with hydrogen, deuterium and helium plasmas. A set of models [5-7] has been developed to study VASIMR light gases helicon discharge. Using zero-dimensional model incorporating energy and mass balance equations we study scaling of the plasma source efficiency with the increased mass flow rate, applied electrical power and dimensions of the quartz tube. We compare theoretical results with existing experimental data. [1] M.A.Lieberman, A.J.Lihtenberg, 'Principles of ..', Wiley, 1994; [2] F.F.Chen, Plas. Phys. Contr. Fus. 33, 339, 1991; [3] F.Chang-Diaz et al, Bull. APS 45 (7) 129, 2000; [4] J.Squire et al., Bull. APS 45 (7) 130, 2000; [5] O.Batishchev, K.Molvig, AIAA technical paper 2000-3754, 2001; [6] O.Batishchev, K.Molvig, IEPC-01-208 paper, 27th Int. Electrical Propulsion Conf., 2001; [7] O.Batishchev, K.Molvig, AIAA technical paper 2002-0347, 2002.

Electrodeless plasma thrusters for spacecraft: A review

NASA Astrophysics Data System (ADS)

Bathgate, S. N.; Bilek, M. M. M.; McKenzie, D. R.

2017-08-01

The physics of electrodeless electric thrusters that use directed plasma to propel spacecraft without employing electrodes subject to plasma erosion is reviewed. Electrodeless plasma thrusters are potentially more durable than presently deployed thrusters that use electrodes such as gridded ion, Hall thrusters, arcjets and resistojets. Like other plasma thrusters, electrodeless thrusters have the advantage of reduced fuel mass compared to chemical thrusters that produce the same thrust. The status of electrodeless plasma thrusters that could be used in communications satellites and in spacecraft for interplanetary missions is examined. Electrodeless thrusters under development or planned for deployment include devices that use a rotating magnetic field; devices that use a rotating electric field; pulsed inductive devices that exploit the Lorentz force on an induced current loop in a plasma; devices that use radiofrequency fields to heat plasmas and have magnetic nozzles to accelerate the hot plasma and other devices that exploit the Lorentz force. Using metrics of specific impulse and thrust efficiency, we find that the most promising designs are those that use Lorentz forces directly to expel plasma and those that use magnetic nozzles to accelerate plasma.

An intersubject variable regional anesthesia simulator with a virtual patient architecture.

PubMed

Ullrich, Sebastian; Grottke, Oliver; Fried, Eduard; Frommen, Thorsten; Liao, Wei; Rossaint, Rolf; Kuhlen, Torsten; Deserno, Thomas M

2009-11-01

The main purpose is to provide an intuitive VR-based training environment for regional anesthesia (RA). The research question is how to process subject-specific datasets, organize them in a meaningful way and how to perform the simulation for peripheral regions. We propose a flexible virtual patient architecture and methods to process datasets. Image acquisition, image processing (especially segmentation), interactive nerve modeling and permutations (nerve instantiation) are described in detail. The simulation of electric impulse stimulation and according responses are essential for the training of peripheral RA and solved by an approach based on the electric distance. We have created an XML-based virtual patient database with several subjects. Prototypes of the simulation are implemented and run on multimodal VR hardware (e.g., stereoscopic display and haptic device). A first user pilot study has confirmed our approach. The virtual patient architecture enables support for arbitrary scenarios on different subjects. This concept can also be used for other simulators. In future work, we plan to extend the simulation and conduct further evaluations in order to provide a tool for routine training for RA.

Mass comparisons of electric propulsion systems for NSSK of geosynchronous spacecraft

NASA Technical Reports Server (NTRS)

Rawlin, Vincent K.; Majcher, Gregory A.

1991-01-01

A model was developed and exercised to allow wet mass comparisons of three axis stabilized communication satellites delivered to geosynchronous transfer orbit. The mass benefits of using advanced chemical propulsion for apogee injection and north-south stationkeeping (NSSK) functions or electric propulsion (hydrazine arcjets and xenon ion thrusters) for NSSK functions are documented. A large derated ion thrusters is proposed which minimizes thruster lifetime concerns and qualification test times when compared to those of smaller ion thrusters planned for NSSK applications. The mass benefits, which depend on the spacecraft mass and mission duration, increase dramatically with arcjet specific impulse in the 500 to 600 s range, but are nearly constant for the derated ion thruster operated in the 2300 to 3000 s range. For a given mission, the mass benefits with an ion system are typically double those of the arcjet system; however, the total thrusting time with arcjets is less than 1/3 that with ion thrusters for the same thruster power. The mass benefits may permit increases in revenue producing payload or reduce launch costs by allowing a move to a smaller launch vehicle.

High Power MPD Thruster Performance Measurements

NASA Technical Reports Server (NTRS)

LaPointe, Michael R.; Strzempkowski, Eugene; Pencil, Eric

2004-01-01

High power magnetoplasmadynamic (MPD) thrusters are being developed as cost effective propulsion systems for cargo transport to lunar and Mars bases, crewed missions to Mars and the outer planets, and robotic deep space exploration missions. Electromagnetic MPD thrusters have demonstrated, at the laboratory level, the ability to process megawatts of electrical power while providing significantly higher thrust densities than electrostatic electric propulsion systems. The ability to generate higher thrust densities permits a reduction in the number of thrusters required to perform a given mission, and alleviates the system complexity associated with multiple thruster arrays. The specific impulse of an MPD thruster can be optimized to meet given mission requirements, from a few thousand seconds with heavier gas propellants up to 10,000 seconds with hydrogen propellant. In support of programs envisioned by the NASA Office of Exploration Systems, Glenn Research Center is developing and testing quasi-steady MW-class MPD thrusters as a prelude to steady state high power thruster tests. This paper provides an overview of the GRC high power pulsed thruster test facility, and presents preliminary performance data for a quasi-steady baseline MPD thruster geometry.

Effect of applied magnetic nozzle on an MPD Thruster

NASA Astrophysics Data System (ADS)

Ando, Akira; Izawa, Yuki; Okawa, Kohei; Hashima, Yoko; Watanabe, Hiroshi; Tanaka, Nozomi

2012-10-01

Electric propulsion systems are suitable for long-term mission in space due to its higher specific impulse. An Magneto-Plasma-Dynamic Thruster (MPDT) is one of the promising thrusters of high power electric propulsion systems. It has been reported that the thrust performance of an MPDT can be improved by applying an axial magnetic field on it. In order to investigate the effect of applied field on an MPDT, we have investigated plume plasma parameters and thrust performance in an applied field MPDT. Different types of divergent magnetic nozzle were applied to an MPDT, and thrust was measured using a pendulum type thrust target. Experiments were performed with hydrogen, helium, and argon as propellant gas. Thrust increased with a discharge current up to 6kA and applied magnetic field up to 0.4T. Maximum thrust of 7N was obtained when the peak position of the applied magnetic field was set upstream of the muzzle of the MPDT. The highest thrust performance was obtained with hydrogen gas with divergent magnetic nozzle applied to the MPDT.

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.

Advanced Hall Electric Propulsion for Future In-space Transportation

NASA Technical Reports Server (NTRS)

Oleson, Steven R.; Sankovic, John M.

2001-01-01

The Hall thruster is an electric propulsion device used for multiple in-space applications including orbit raising, on-orbit maneuvers, and de-orbit functions. These in-space propulsion functions are currently performed by toxic hydrazine monopropellant or hydrazine derivative/nitrogen tetroxide bi-propellant thrusters. The Hall thruster operates nominally in the 1500 sec specific impulse regime. It provides greater thrust to power than conventional gridded ion engines, thus reducing trip times and operational life when compared to that technology in Earth orbit applications. The technology in the far term, by adding a second acceleration stage, has shown promise of providing over 4000s Isp, the regime of the gridded ion engine and necessary for deep space applications. The Hall thruster system consists of three parts, the thruster, the power processor, and the propellant system. The technology is operational and commercially available at the 1.5 kW power level and 5 kW application is underway. NASA is looking toward 10 kW and eventually 50 kW-class engines for ambitious space transportation applications. The former allows launch vehicle step-down for GEO missions and demanding planetary missions such as Europa Lander, while the latter allows quick all-electric propulsion LEO to GEO transfers and non-nuclear transportation human Mars missions.

Electro-optical effects in porous PET films filled with liquid crystal: new possibilities for fiber optics and THZ applications.

PubMed

Chopik, A; Pasechnik, S; Semerenko, D; Shmeliova, D; Dubtsov, A; Srivastava, A K; Chigrinov, V

2014-03-15

The results of investigation of electro-optical properties of porous polyethylene terephthalate films filled with a nematic liquid crystal (5 CB) are presented. It is established that the optical response of the samples on the applied voltage drastically depends on the frequency range. At low frequencies of applied electrical field (ffc) electric field induces an overall change in the light intensity, which is typical for an electro-optical response of a liquid crystal (LC) layer in a conventional "sandwich"-like cell. The dependences of critical frequency fc, threshold voltages, and characteristic times on a pore diameter d were established. The peculiarities of electro-optical effects can be explained in the framework of the approach which connects the variations of light intensity with the corresponding changes of the effective refractive index n(eff) of a composite LC media. The unusual behavior of the electro-optical response at low frequencies is assigned to the orienting action of the specific shear flow typical for electrokinetic phenomena in polar liquids.

13kW Advanced Electric Propulsion Flight System Development and Qualification

NASA Technical Reports Server (NTRS)

Jackson, Jerry; Allen, May; Myers, Roger; Soendker, Erich; Welander, Benjamin; Tolentino, Artie; Hablitzel, Sam; Yeatts, Chyrl; Xu, Steven; Sheehan, Chris;

Ultra High Voltage Propellant Isolators and Insulators for JIMO Ion Thrusters

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Gaier, James R.; Hung, Ching-Cheh; Walters, Patty A.; Sechkar, Ed; Panko, Scott; Kamiotis, Christina A.

2004-01-01

Within NASA's Project Prometheus, high specific impulse ion thrusters for electric propulsion of spacecraft for the proposed Jupiter Icy Moon Orbiter (JIMO) mission to three of Jupiter's moons: Callisto, Ganymede and Europa will require high voltage operation to meet mission propulsion. The anticipated approx.6,500 volt net ion energy will require electrical insulation and propellant isolation which must exceed that used successfully by the NASA Solar Electric Propulsion Technology Readiness (NSTAR) Deep Space 1 mission thruster by a factor of approx.6. Xenon propellant isolator prototypes that operate at near one atmosphere and prototypes that operate at low pressures (<100 Torr) have been designed and are being tested for suitability to the JIMO mission requirements. Propellant isolators must be durable to Paschen breakdown, sputter contamination, high temperature, and high voltage while operating for factors longer duration than for the Deep Space 1 Mission. Insulators used to mount the thrusters as well as those needed to support the ion optics have also been designed and are under evaluation. Isolator and insulator concepts, design issues, design guidelines, fabrication considerations and performance issues are presented. The objective of the investigation was to identify candidate isolators and insulators that are sufficiently robust to perform durably and reliably during the proposed JIMO mission.

Design of tapered arm impulse radiating antenna with log periodic lens system for skin cancer treatment.

PubMed

Petrishia, A; Sasikala, M

2014-04-01

A Prolate-Spheroidal Impulse Radiating Antenna (PSIRA) is used as a non-invasive technique for generating an electromagnetic implosion to kill melanoma cells. It can launch and focus fast (100 ps) high voltage (>50 KV) pulses into the biological targets. It can be used to obtain electromagnetic focusing on the target to reduce the damage to the tissue layers surrounding the target (skin). The main aim of this work is to improve the gain of the antenna, enhance the electric field intensity and to reduce the spot size at the focal point. In this work the PSIRA with tapered arm is designed to increase the gain of the antenna. The log periodic lens system is designed to enhance the electric field and reduce the spot size. The IRA with tapered arms located at the position of φ = 60° gives a gain improvement of 14.28% when compared to a traditional IRA. In this work a 10-layer dielectric lens system is designed to match the 100 ps pulses to the skin phantom. Simulation results show that the electric field is increased by a factor of 2. The spot size is reduced from 1 cm to 0.75 cm at the focal point where the target is placed. The proposed Log periodic lens system provides an increase in electric field amplitude and reduction in spot size.

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.

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.

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.

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

Effects of anchoring and arc structure on the control authority of a rail plasma actuator

NASA Astrophysics Data System (ADS)

Choi, Young-Joon; Gray, Miles; Sirohi, Jayant; Raja, Laxminarayan L.

2017-09-01

Experiments were conducted on a rail plasma actuator (RailPAc) with different electrode cross sections (rails or rods) to assess methods to improve the actuation authority, defined as the impulse generated for a given electrical input. The arc was characterized with electrical measurements and high-speed images, while impulse measurements quantified the actuation authority. A RailPAc power supply capable of delivering  ∼1 kA of current at  ∼100 V was connected to rod electrodes (free-floating with circular cross-section) and rail electrodes (flush-mounted in a flat plate with rectangular cross-section). High-speed images show that the rail electrodes cause the arc to anchor itself to the anode electrode and transit in discrete jumps, while rod electrodes permit the arc to transit smoothly without anchoring. The impulse measurements reveal that the anchoring reduces the actuation authority by  ∼21% compared to a smooth transit, and the effect of anchoring can be suppressed by reducing the gap between the rails to 2 mm. The study further demonstrates that if a smooth transit is achieved, the control authority can be increased with a larger gap and larger arc current. In conclusion, the actuation authority of a RailPAc can be maximized by carefully choosing a gap width that prevents anchoring. Further study is warranted to increase the RailPAc actuation authority by introducing multiple turns of wires beneath the RailPAc to augment the induced magnetic field.

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

Study of power-to-weight ratio of the electrothermal propulsion system of nanosatellite maneuvering satellite platform

NASA Astrophysics Data System (ADS)

Blinov, V. N.; Vavilov, I. S.; Kositsin, V. V.; Lukyanchik, A. I.; Ruban, V. I.; Shalay, V. V.

2018-01-01

The direction of the solution of the actual task of maneuvering satellite platforms (MSP) design for nanosatellite weighing up to 10 kg, power-to-weight ratio of PS up to 8 W (electrothermal micro engine (ETME) 5 W, vaporizer 2 W, electrovalve up to 1 W) and with characteristic velocity up to 60 m/s were considered on the basis of studies of the propulsion system(PS) with ETME. The aim of study is the confirmation of technical possibility of nanosatellites design with mass up to 10 kg, power-to-weight ratio up to 8 W and with characteristic velocity up to 60 m/s on the basis of PS prototype experimental studies. In the course of the research tasks were solved to determine the design of PS and ETME of nanosatellit’s MSP, determine the electric parameters of PS depending on power consumption that determining specific impulse of ETME, and estimate the implemented characteristic velocity of the nanosatellite. The PS constructive scheme of nanosatellite mass of 10 kg was design, PS experimental prototype was produced and PS experimental research on ammonia were conducted. The 200°C was reached per 900 s at 5 W ETME power consumption with nitrogen, that equivalent to specific impulse of ammonia ETME 124/136 s when entering the stationary mode. 2 W energy consumption of a two-thread liquid ammonia vaporizer is experimentally substantiated. The using of electrovelve stepped control cyclogram allowed to reduce the average power consumption to 1 W.

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.

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.

Earth-ionosphere transmission line model for an impulsive geomagnetic disturbance at the dayside geomagnetic equator

NASA Astrophysics Data System (ADS)

Kikuchi, T.

2004-12-01

The near instantaneous onset of a geomagnetic impulse such as the preliminary reverse impulse (PRI) of the geomagnetic sudden commencement at high latitude and at the dayside geomagnetic equator has been explained by means of the TM0 mode waves in the Earth-ionosphere waveguide (Kikuchi and Araki, J. Atmosph. Terrest. Phys., 41, 927-936, 1979). There is, on the other hand, a time lag of the order of 10 sec in the peak amplitude of the magnetic impulse at the dayside equator. To explain these two temporal aspects, we examine transmission of the TM0 mode in a finite-length Earth-ionosphere transmission line composed of a finitely conducting ionosphere and the perfectly conducting Earth, with a fixed electric potential at one end and null potential at the other end of the transmission line, corresponding to the foot of a field-aligned current on the dawn- or dusk-side in the polar cap and middle point on the noon-midnight meridian at low latitude, respectively. Successive transmission and reflection in the bounded transmission line lead to that the ionospheric currents start to grow instantaneously, but reach a steady state with a relaxation time proportional to the length of the transmission line and the ionospheric conductivity. The relaxation time is of the order of 10 sec when we give high conductivity applicable to the equatorial ionosphere, which matches the observed time lag in the peak amplitude of the equatorial geomagnetic impulse. Consequently, the TM0 mode in the finite-length Earth-ionosphere transmission line explains both the instantaneous onset and time lag in the peak amplitude of the geomagnetic impulse at the dayside geomagnetic equator.

I-SAVE: AN INTERACTIVE REAL-TIME MONITOR AND CONTROLLER TO INFLUENCE ENERGY CONSERVATION BEHAVIOR BY IMPULSE SAVING

EPA Science Inventory

Simulation-based model to explore the benefits of monitoring and control to energy saving opportunities in residential homes; an adaptive algorithm to predict the type of electrical loads; a prototype user friendly interface monitoring and control device to save energy; a p...

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.

[A physiological investigation of chronic electrical stimulation with scala tympani electrodes in kittens].

PubMed

Ni, D

1992-12-01

A physiological investigation of cochlear electrical stimulation was undertaken in six two-month-old kittens. The scala tympani electrodes were implanted and electrically stimulated using biphasic balanced electrical pulses for periods of 1000-1500h in four ears. Four ears received implants for same period but without electrical stimulation. The other two ears served as normal control. The results indicated: 1) Chronic electrical stimulation of the cochlea within electrochemically safe limits did not influence the hearing of kittens and the normal delivery of impulses evoked by acoustic and electrical signals on the auditory brainstem pathway. 2) The wave shapes of EABRs were similar to those of ABRs. The amplitudes of EABRs showed a significant increase following chronic electrical stimulation, resulting in a leftward shift in the input/output function. The absolute latencies and interwave latencies of waves II-III, III-IV and II-IV were significantly shorter than those of ABRs. These results imply that there was no adverse effect of chronic electrical stimulation on the maturing auditory systems of kittens using these electrical parameters and the mechanism of electrical hearing should be further studied.

A One-year, Short-Stay Crewed Mars Mission Using Bimodal Nuclear Thermal Electric Propulsion (BNTEP) - A Preliminary Assessment

NASA Technical Reports Server (NTRS)

Burke, Laura A.; Borowski, Stanley K.; McCurdy, David R.; Packard, Thomas W.

2013-01-01

A crewed mission to Mars poses a signi cant challenge in dealing with the physiolog- ical issues that arise with the crew being exposed to a near zero-gravity environment as well as signi cant solar and galactic radiation for such a long duration. While long sur- face stay missions exceeding 500 days are the ultimate goal for human Mars exploration, short round trip, short surface stay missions could be an important intermediate step that would allow NASA to demonstrate technology as well as study the physiological e ects on the crew. However, for a 1-year round trip mission, the outbound and inbound hy- perbolic velocity at Earth and Mars can be very large resulting in a signi cant propellant requirement for a high thrust system like Nuclear Thermal Propulsion (NTP). Similarly, a low thrust Nuclear Electric Propulsion (NEP) system requires high electrical power lev- els (10 megawatts electric (MWe) or more), plus advanced power conversion technology to achieve the lower speci c mass values needed for such a mission. A Bimodal Nuclear Thermal Electric Propulsion (BNTEP) system is examined here that uses three high thrust Bimodal Nuclear Thermal Rocket (BNTR) engines allowing short departure and capture maneuvers. The engines also generate electrical power that drives a low thrust Electric Propulsion (EP) system used for ecient interplanetary transit. This combined system can help reduce the total launch mass, system and operational requirements that would otherwise be required for equivalent NEP or Solar Electric Propulsion (SEP) mission. The BNTEP system is a hybrid propulsion concept where the BNTR reactors operate in two separate modes. During high-thrust mode operation, each BNTR provides 10's of kilo- Newtons of thrust at reasonably high speci c impulse (Isp) of 900 seconds for impulsive trans-planetary injection and orbital insertion maneuvers. When in power generation / EP mode, the BNTR reactors are coupled to a Brayton power conversion system allowing each reactor to generate 100's of kWe of electrical power to a very high Isp (3000 s) EP thruster system for sustained vehicle acceleration and deceleration in heliocentric space.

Effect of amplitude and duration of impulsive pressure on endothelial permeability in in vitro fluid percussion trauma

PubMed Central

2014-01-01

Background Intracranial pressure changes during head impact cause brain injuries such as vasogenic edema and cerebral contusion. However, the influence of impulsive pressure on endothelial function has not yet been fully studied in vitro. In this study, we developed a pressure loading device that produced positive and negative pressures by modifying an in vitro fluid percussion model and examined the effects of the amplitude and duration of the pressures on endothelial permeability. Methods Human umbilical vein endothelial cells were subjected to three types of positive pressure (average amplitude/average duration of 352 kPa/23 ms, 73 kPa/27 ms, and 70 kPa/44 ms) and three types of negative pressure (−72 kPa/41 ms, −67 kPa/104 ms, and −91 kPa/108 ms), and the transendothelial electrical resistance (TEER) was measured between 15 min and 24 h after pressure loading for quantifying the formation of an integral monolayer of endothelial cells. After loading, vascular endothelial- (VE-) cadherin, an endothelium-specific cell-cell adhesion molecule involved in endothelial barrier function, was stained and observed using fluorescence microscopy. Results The pressure loading device could produce positive pressure pulses with amplitudes of 53–1348 kPa and durations of 9–29.1 ms and negative pressure pulses with amplitudes of −52–−93 kPa and durations of 42.9–179.5 ms. The impulsive pressure reduced the TEER associated with the change in VE-cadherin localization. Additionally, TEER decreased considerably at 15 min and 6 h post-loading, with these changes being significant in positive pressure with larger amplitude and shorter duration and in all types of negative pressures compared to pre-loading. Conclusions The changes in intracranial pressure during head impact impair endothelial barrier function by the disruption of the integrity of endothelial cell-cell junctions, and the degree of increase in endothelial permeability depends on the amplitude, duration, and direction (compressive and tensile) of the impulsive pressure. PMID:24739360

Impact of Steep-Front Short-Duration Impulse on Electric Power System Insulation. Phase 2. Laboratory Evaluation of Selected Power System Components

DTIC Science & Technology

1991-04-01

SEALS - _------ OIL LEVEL STAINLESS STEEL INDICATOR EXPANSION CHAMBER MULTIPLE COMPRESSION GASKET SPRINGS CONDUCTOR RO) UPPER PORCELAIN_ OIL...GENERATED WAVEFORM) FIELD Electric (E) 40 kV/m 50 kV/m 10 kV/m STRENGTH ( FREE SPACE) Magnetic(M) 300 A/m 1000 A/m 300 A/m Rise time 20-500 ns 10 ns 10 ns...Laboratory Interaction Note IN435, 1983. 4. P. R_ Barnes, "The Axial Current Induced on an Infinitely Long, Perfectly Conducting, Circular Cylinder in Free

Strategies for the sustained human exploration of Mars

NASA Astrophysics Data System (ADS)

Landau, Damon Frederick

A variety of mission scenarios are compared in this thesis to assess the strengths and weaknesses of options for Mars exploration. The mission design space is modeled along two dimensions: trajectory architectures and propulsion system technologies. Direct, semi-direct, stop-over, semi-cycler, and cycler architectures are examined, and electric propulsion, nuclear thermal rockets, methane and oxygen production on Mars, Mars water excavation, aerocapture, and reusable propulsion systems are included in the technology assessment. The mission sensitivity to crew size, vehicle masses, and crew travel time is also examined. The primary figure of merit for a mission scenario is the injected mass to low-Earth orbit (IMLEO), though technology readiness levels (TRL) are also included. Several elements in the architecture dimension are explored in more detail. The Earth-Mars semi-cycler architecture is introduced and five families of Earth-Mars semi-cycler trajectories are presented along with optimized itineraries. Optimized cycler trajectories are also presented. In addition to Earth-Mars semi-cycler and cycler trajectories, conjunction-class, free-return, Mars-Earth semi-cycler, and low-thrust trajectories are calculated. Design parameters for optimal DeltaV trajectories are provided over a range of flight times (from 120 to 270 days) and launch years (between 2009 and 2022). Unlike impulsive transfers, the mass-optimal low-thrust trajectory depends strongly on the thrust and specific impulse of the propulsion system. A low-thrust version of the rocket equation is provided where the initial mass or thrust may be minimized by varying the initial acceleration and specific impulse. Planet-centered operations are also examined. A method to rotate a parking orbit about the line of apsides to achieve the proper orientation at departure is discussed, thus coupling the effects of parking-orbit orientation with the interplanetary trajectories. Also, a guidance algorithm for rendezvous during flybys in semi-cycler and cycler missions is presented with a control law for final approach. A forty-year plan to establish a permanent base on Mars is detailed and methods to expand the base are discussed. Once a large base is established, one-, two-, or three-vehicle systems may sustain the colonization of Mars.

Auditory and behavioral responses of California sea lions (Zalophus californianus) to single underwater impulses from an arc-gap transducer.

PubMed

Finneran, James J; Dear, Randall; Carder, Donald A; Ridgway, Sam H

2003-09-01

A behavioral response paradigm was used to measure underwater hearing thresholds in two California sea lions (Zalophus californianus) before and after exposure to underwater impulses from an arc-gap transducer. Preexposure and postexposure hearing thresholds were compared to determine if the subjects experienced temporary shifts in their masked hearing thresholds (MTTS). Hearing thresholds were measured at 1 and 10 kHz. Exposures consisted of single underwater impulses produced by an arc-gap transducer referred to as a "pulsed power device" (PPD). The electrical charge of the PPD was varied from 1.32 to 2.77 kJ; the distance between the subject and the PPD was varied over the range 3.4 to 25 m. No MTTS was observed in either subject at the highest received levels: peak pressures of approximately 6.8 and 14 kPa, rms pressures of approximately 178 and 183 dB re: 1 microPa, and total energy fluxes of 161 and 163 dB re: 1 microPa2s for the two subjects. Behavioral reactions to the tests were observed in both subjects. These reactions primarily consisted of temporary avoidance of the site where exposure to the PPD impulse had previously occurred.

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.

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.

Surface Breakdown Characteristics of Silicone Oil for Electric Power Apparatus

NASA Astrophysics Data System (ADS)

Wada, Junichi; Nakajima, Akitoshi; Miyahara, Hideyuki; Takuma, Tadasu; Okabe, Shigemitu; Kohtoh, Masanori; Yanabu, Satoru

This paper describes the surface breakdown characteristics of the silicone oil which has the possibility of the application to innovative switchgear as an insulating medium. At the first step, we have experimentally studied on the impulse breakdown characteristics of the configuration with a triple-junction where a solid insulator is in contact with the electrode. The test configurations consist of solid material (Nomex and pressboard) and liquid insulation oil (silicone and mineral oil). We have discussed the experimental results based on the maximal electric field at a triple-junction. As the second step, we have studied the configuration which may improve the surface breakdown characteristics by lowering the electric field near the triple-junction.

Trajectories for High Specific Impulse High Specific Power Deep Space Exploration

NASA Technical Reports Server (NTRS)

Polsgrove, T.; Adams, R. B.; Brady, Hugh J. (Technical Monitor)

2002-01-01

Preliminary results are presented for two methods to approximate the mission performance of high specific impulse high specific power vehicles. The first method is based on an analytical approximation derived by Williams and Shepherd and can be used to approximate mission performance to outer planets and interstellar space. The second method is based on a parametric analysis of trajectories created using the well known trajectory optimization code, VARITOP. This parametric analysis allows the reader to approximate payload ratios and optimal power requirements for both one-way and round-trip missions. While this second method only addresses missions to and from Jupiter, future work will encompass all of the outer planet destinations and some interstellar precursor missions.

Power Reduction of the Air-Breathing Hall-Effect Thruster

NASA Astrophysics Data System (ADS)

Kim, Sungrae

Electric propulsion system is spotlighted as the next generation space propulsion system due to its benefits; one of them is specific impulse. While there are a lot of types in electric propulsion system, Hall-Effect Thruster, one of electric propulsion system, has higher thrust-to-power ratio and requires fewer power supplies for operation in comparison to other electric propulsion systems, which means it is optimal for long space voyage. The usual propellant for Hall-Effect Thruster is Xenon and it is used to be stored in the tank, which may increase the weight of the thruster. Therefore, one theory that uses the ambient air as a propellant has been proposed and it is introduced as Air-Breathing Hall-Effect Thruster. Referring to the analysis on Air-Breathing Hall-Effect Thruster, the goal of this paper is to reduce the power of the thruster so that it can be applied to real mission such as satellite orbit adjustment. To reduce the power of the thruster, two assumptions are considered. First one is changing the altitude for the operation, while another one is assuming the alpha value that is electron density to ambient air density. With assumptions above, the analysis was done and the results are represented. The power could be decreased to 10s˜1000s with the assumptions. However, some parameters that do not satisfy the expectation, which would be the question for future work, and it will be introduced at the end of the thesis.

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.

Electron dynamics in Hall thruster

NASA Astrophysics Data System (ADS)

Marini, Samuel; Pakter, Renato

2015-11-01

Hall thrusters are plasma engines those use an electromagnetic fields combination to confine electrons, generate and accelerate ions. Widely used by aerospace industries those thrusters stand out for its simple geometry, high specific impulse and low demand for electric power. Propulsion generated by those systems is due to acceleration of ions produced in an acceleration channel. The ions are generated by collision of electrons with propellant gas atoms. In this context, we can realize how important is characterizing the electronic dynamics. Using Hamiltonian formalism, we derive the electron motion equation in a simplified electromagnetic fields configuration observed in hall thrusters. We found conditions those must be satisfied by electromagnetic fields to have electronic confinement in acceleration channel. We present configurations of electromagnetic fields those maximize propellant gas ionization and thus make propulsion more efficient. This work was supported by CNPq.

Line-source excited impulsive EM field response of thin plasmonic metal films

NASA Astrophysics Data System (ADS)

Štumpf, Martin; Vandenbosch, Guy A. E.

2013-08-01

In this paper, reflection against and transmission through thin plasmonic metal films, basic building blocks of many plasmonic devices, are analytically investigated directly in the time domain for an impulsive electric and magnetic line-source excitation. The electromagnetic properties of thin metallic films are modeled via the Drude model. The problem is formulated with the help of approximate thin-sheet boundary conditions and the analysis is carried out using the Cagniard-DeHoop technique. Closed-form space-time expressions are found and discussed. The obtained time-domain analytical expressions reveal the existence of the phenomenon of transient oscillatory surface effects along a plasmonic metal thin sheet. Illustrative numerical examples of transmitted/reflected pulsed fields are provided.

Detecting Structural Failures Via Acoustic Impulse Responses

NASA Technical Reports Server (NTRS)

Bayard, David S.; Joshi, Sanjay S.

1995-01-01

Advanced method of acoustic pulse reflectivity testing developed for use in determining sizes and locations of failures within structures. Used to detect breaks in electrical transmission lines, detect faults in optical fibers, and determine mechanical properties of materials. In method, structure vibrationally excited with acoustic pulse (a "ping") at one location and acoustic response measured at same or different location. Measured acoustic response digitized, then processed by finite-impulse-response (FIR) filtering algorithm unique to method and based on acoustic-wave-propagation and -reflection properties of structure. Offers several advantages: does not require training, does not require prior knowledge of mathematical model of acoustic response of structure, enables detection and localization of multiple failures, and yields data on extent of damage at each location.

Dependence of positive and negative sprite morphology on lightning characteristics and upper atmospheric ambient conditions

NASA Astrophysics Data System (ADS)

Qin, Jianqi; Celestin, Sebastien; Pasko, Victor P.

2013-05-01

Carrot sprites, exhibiting both upward and downward propagating streamers, and columniform sprites, characterized by predominantly vertical downward streamers, represent two distinct morphological classes of lightning-driven transient luminous events in the upper atmosphere. It is found that positive cloud-to-ground lightning discharges (+CGs) associated with large charge moment changes (QhQ) tend to produce carrot sprites with the presence of a mesospheric region where the electric field exceeds the value 0.8Ek and persists for >˜2 ms, whereas those associated with small QhQ are only able to produce columniform sprites. Columniform sprites may also appear in the periphery of a sprite halo produced by +CGs associated with large QhQ. For a sufficiently large QhQ, the time dynamics of the QhQ determines the specific shape of the carrot sprites. In the case when the sufficiently large QhQ is produced mainly by an impulsive return stroke, strong electric field is produced at high altitudes and manifests as a bright halo, and the corresponding conductivity enhancement lowers/enhances the probability of streamer initiation inside/below the sprite halo. A more impulsive return stroke leads to a more significant conductivity enhancement (i.e., a brighter halo). This conductivity enhancement also leads to fast decay and termination of the upper diffuse region of carrot sprites because it effectively screens out the electric field at high altitudes. On the contrary, if the sufficiently large QhQ is produced by a weak return stroke (i.e., a dim halo) accompanied by intense continuing current, the lightning-induced electric field at high altitudes persists at a level that is comparable to Ek, and therefore an extensive upper diffuse region can develop. Furthermore, we demonstrate that `negative sprites' (produced by -CGs) should be necessarily carrot sprites and most likely accompanied by a detectable halo, since the initiation of upward positive streamers is always easier than that of downward negative streamers, and -CGs are usually associated with impulsive return stroke with no continuing current. We also conjecture that in some cases, fast decaying single-headed upward positive streamers produced by -CGs may appear as bright spots/patches. We show that the threshold charge moment changes of positive and negative sprites are, respectively, ~320 and ~500 C km under typical nighttime conditions assumed in this study. These different initiation thresholds, along with the different applied electric field required for stable propagation of positive and negative streamers and the fact that +CGs much more frequently produce large charge moment changes, represent three major factors in the polarity asymmetry of +CGs and -CGs in producing sprite streamers. We further demonstrate that lower mesospheric ambient conductivity leads to smaller threshold charge moment change required for the production of carrot sprites. We suggest that geographical and temporal conductivity variations in the lower ionosphere documented in earlier studies, along with the seasonal and inter-annual variations of thunderstorm activity that lead to different lightning characteristics in the troposphere, account for the different morphological features of sprites observed in different observation campaigns.

Domain IV voltage-sensor movement is both sufficient and rate limiting for fast inactivation in sodium channels.

PubMed

Capes, Deborah L; Goldschen-Ohm, Marcel P; Arcisio-Miranda, Manoel; Bezanilla, Francisco; Chanda, Baron

2013-08-01

Voltage-gated sodium channels are critical for the generation and propagation of electrical signals in most excitable cells. Activation of Na(+) channels initiates an action potential, and fast inactivation facilitates repolarization of the membrane by the outward K(+) current. Fast inactivation is also the main determinant of the refractory period between successive electrical impulses. Although the voltage sensor of domain IV (DIV) has been implicated in fast inactivation, it remains unclear whether the activation of DIV alone is sufficient for fast inactivation to occur. Here, we functionally neutralize each specific voltage sensor by mutating several critical arginines in the S4 segment to glutamines. We assess the individual role of each voltage-sensing domain in the voltage dependence and kinetics of fast inactivation upon its specific inhibition. We show that movement of the DIV voltage sensor is the rate-limiting step for both development and recovery from fast inactivation. Our data suggest that activation of the DIV voltage sensor alone is sufficient for fast inactivation to occur, and that activation of DIV before channel opening is the molecular mechanism for closed-state inactivation. We propose a kinetic model of sodium channel gating that can account for our major findings over a wide voltage range by postulating that DIV movement is both necessary and sufficient for fast inactivation.

Apollo 14 mission report. Supplement 5: Descent propulsion system final flight evaluation

NASA Technical Reports Server (NTRS)

Avvenire, A. T.; Wood, S. C.

1972-01-01

The performance of the LM-8 descent propulsion system during the Apollo 14 mission was evaluated and found to be satisfactory. The average engine effective specific impulse was 0.1 second higher than predicted, but well within the predicted l sigma uncertainty. The engine performance corrected to standard inlet conditions for the FTP portion of the burn at 43 seconds after ignition was as follows: thrust, 9802, lbf; specific impulse, 304.1 sec; and propellant mixture ratio, 1603. These values are + or - 0.8, -0.06, and + or - 0.3 percent different respectively, from the values reported from engine acceptance tests and were within specification limits.

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.

Fractional diffusion models of cardiac electrical propagation: role of structural heterogeneity in dispersion of repolarization

PubMed Central

Bueno-Orovio, Alfonso; Kay, David; Grau, Vicente; Rodriguez, Blanca; Burrage, Kevin

2014-01-01

Impulse propagation in biological tissues is known to be modulated by structural heterogeneity. In cardiac muscle, improved understanding on how this heterogeneity influences electrical spread is key to advancing our interpretation of dispersion of repolarization. We propose fractional diffusion models as a novel mathematical description of structurally heterogeneous excitable media, as a means of representing the modulation of the total electric field by the secondary electrical sources associated with tissue inhomogeneities. Our results, analysed against in vivo human recordings and experimental data of different animal species, indicate that structural heterogeneity underlies relevant characteristics of cardiac electrical propagation at tissue level. These include conduction effects on action potential (AP) morphology, the shortening of AP duration along the activation pathway and the progressive modulation by premature beats of spatial patterns of dispersion of repolarization. The proposed approach may also have important implications in other research fields involving excitable complex media. PMID:24920109

Intense transient electric field sensor based on the electro-optic effect of LiNbO3

NASA Astrophysics Data System (ADS)

Yang, Qing; Sun, Shangpeng; Han, Rui; Sima, Wenxia; Liu, Tong

2015-10-01

Intense transient electric field measurements are widely applied in various research areas. An optical intense E-field sensor for time-domain measurements, based on the electro-optic effect of lithium niobate, has been studied in detail. Principles and key issues in the design of the sensor are presented. The sensor is insulated, small in size (65 mm × 15 mm × 15 mm), and suitable for high-intensity (<801 kV/m) electric field measurements over a wide frequency band (10 Hz-10 MHz). The input/output characteristics of the sensor were obtained and the sensor calibrated. Finally, an application using this sensor in testing laboratory lightning impulses and in measuring transient electric fields during switch-on of a disconnector confirmed that the sensor is expected to find widespread use in transient intense electric field measurement applications.

An Innovative Manufacturing of CCC Ion Thruster Grids by North Carolina A&T's RTM Carbon/Carbon Process

NASA Technical Reports Server (NTRS)

Haag, Thomas W. (Technical Monitor); Shivakumar, Kunigal N.

2003-01-01

Electric ion thrusters are the preferred engines for deep space missions, because of very high specific impulse. The ion engine consists of screen and accelerator grids containing thousands of concentric very small holes. The xenon gas accelerates between the two grids, thus developing the impulse force. The dominant life-limiting mechanism in the state-of-the-art molybdenum thrusters is the xenon ion sputter erosion of the accelerator grid. Carbon/carbon composites (CCC) have shown to be have less than 1/7 the erosion rates than the molybdenum, thus for interplanetary missions CCC engines are inevitable. Early effort to develop CCC composite thrusters had a limited success because of limitations of the drilling technology and the damage caused by drilling. The proposed is an in-situ manufacturing of holes while the CCC is made. Special low CTE molds will be used along with the NC A&T s patented resin transfer molding (RTM) technology to manufacture the CCC grids. First, a manufacture process for 10-cm diameter thruster grids will be developed and verified. Quality of holes, density, CTE, tension, flexure, transverse fatigue and sputter yield properties will be measured. After establishing the acceptable quality and properties, the process will be scaled to manufacture 30-cm diameter grids. The properties of the two grid sizes are compared with each other.

9. INTERIOR OF KERN RIVER No. 1 POWERHOUSE BUILDING SHOWING ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

9. INTERIOR OF KERN RIVER No. 1 POWERHOUSE BUILDING SHOWING EXCITER No 2. Ca. 1930 GENERAL ELECTRIC ALTERNATING CURRENT MOTOR REPLACEMENT FOR ALLIS-CHALMERS IMPULSE WHEEL IS VISIBLE ON RIGHT ALONG WITH COUPLING TO EXCITER SHAFT. VIEW TO NORTHWEST. - Kern County No. 1 Hydroelectric System, Powerhouse Exciters, Kern River Canyon, Bakersfield, Kern County, CA

Hybrids of Solar Sail, Solar Electric, and Solar Thermal Propulsion for Solar-System Exploration

NASA Technical Reports Server (NTRS)

Wilcox, Brian H.

2012-01-01

Solar sails have long been known to be an attractive method of propulsion in the inner solar system if the areal density of the overall spacecraft (S/C) could be reduced to approx.10 g/sq m. It has also long been recognized that the figure (precise shape) of useful solar sails needs to be reasonably good, so that the reflected light goes mostly in the desired direction. If one could make large reflective surfaces with reasonable figure at an areal density of approx.10 g/sq m, then several other attractive options emerge. One is to use such sails as solar concentrators for solar-electric propulsion. Current flight solar arrays have a specific output of approx. 100W/kg at 1 Astronomical Unit (AU) from the sun, and near-term advances promise to significantly increase this figure. A S/C with an areal density of 10 g/sq m could accelerate up to 29 km/s per year as a solar sail at 1 AU. Using the same sail as a concentrator at 30 AU, the same spacecraft could have up to approx. 45 W of electric power per kg of total S/C mass available for electric propulsion (EP). With an EP system that is 50% power-efficient, exhausting 10% of the initial S/C mass per year as propellant, the exhaust velocity is approx. 119 km/s and the acceleration is approx. 12 km/s per year. This hybrid thus opens attractive options for missions to the outer solar system, including sample-return missions. If solar-thermal propulsion were perfected, it would offer an attractive intermediate between solar sailing in the inner solar system and solar electric propulsion for the outer solar system. In the example above, both the solar sail and solar electric systems don't have a specific impulse that is near-optimal for the mission. Solar thermal propulsion, with an exhaust velocity of the order of 10 km/s, is better matched to many solar system exploration missions. This paper derives the basic relationships between these three propulsion options and gives examples of missions that might be enabled by such hybrids.

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…

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%.

Laboratory Model 50 kW Hall Thruster

NASA Technical Reports Server (NTRS)

Manzella, David; Jankovsky, Robert; Hofer, Richard

2002-01-01

A 0.46 meter diameter Hall thruster was fabricated and performance tested at powers up to 72 kilowatts. Thrusts up to 2.9 Newtons were measured. Discharge specific impulses ranged from 1750 to 3250 seconds with discharge efficiencies between 46 and 65 percent. Overall specific impulses ranged from 1550 to 3050 seconds with overall efficiencies between 40 and 57 percent. Performance data indicated significant fraction of multiple-charged ions during operation at elevated power levels. Cathode mass flow rate was shown to be a significant parameter with regard to thruster efficiency.

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.

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.

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.

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

Measurement of impulse current using polarimetric fiber optic sensor

NASA Astrophysics Data System (ADS)

Ginter, Mariusz

2017-08-01

In the paper the polarimetric current sensing solution used for measurements of high amplitude currents and short durations is presented. This type of sensor does not introduce additional resistance and inductance into the circuit, which is a desirable phenomenon in this type of measurement. The magneto element is a fiber optic coil made of spun fiber optic. The fiber in which the core is twisted around its axis is characterized by a small effect of interfering magnitudes, ie mechanical vibrations and pressure changes on the polarimeter. The presented polarimetric current sensor is completely fiber optic. Experimental results of a proposed sensor construction solution operating at 1550 nm and methods of elimination of influence values on the fiber optic current sensor were presented. The sensor was used to measure the impulse current. The generated current pulses are characterized by a duration of 23μs and amplitudes ranging from 1 to 3.5 kA. The currents in the discharge circuit are shown. The measurement uncertainty of the amplitude of the electric current in the range of measured impulses was determined and estimated to be no more than 2%.

Evolution of rapid nerve conduction.

PubMed

Castelfranco, Ann M; Hartline, Daniel K

2016-06-15

Rapid conduction of nerve impulses is a priority for organisms needing to react quickly to events in their environment. While myelin may be viewed as the crowning innovation bringing about rapid conduction, the evolution of rapid communication mechanisms, including those refined and enhanced in the evolution of myelin, has much deeper roots. In this review, a sequence is traced starting with diffusional communication, followed by transport-facilitated communication, the rise of electrical signaling modalities, the invention of voltage-gated channels and "all-or-none" impulses, the emergence of elongate nerve axons specialized for communication and their fine-tuning to enhance impulse conduction speeds. Finally within the evolution of myelin itself, several innovations have arisen and have been interactively refined for speed enhancement, including the addition and sealing of layers, their limitation by space availability, and the optimization of key parameters: channel density, lengths of exposed nodes and lengths of internodes. We finish by suggesting several design principles that appear to govern the evolution of rapid conduction. This article is part of a Special Issue entitled SI: Myelin Evolution. Copyright © 2016. Published by Elsevier B.V.

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.

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.

Development priorities for in-space propulsion technologies

NASA Astrophysics Data System (ADS)

Johnson, Les; Meyer, Michael; Palaszewski, Bryan; Coote, David; Goebel, Dan; White, Harold

2013-02-01

During the summer of 2010, NASA's Office of Chief Technologist assembled 15 civil service teams to support the creation of a NASA integrated technology roadmap. The Aero-Space Technology Area Roadmap is an integrated set of technology area roadmaps recommending the overall technology investment strategy and prioritization for NASA's technology programs. The integrated set of roadmaps will provide technology paths needed to meet NASA's strategic goals. The roadmaps have been reviewed by senior NASA management and the National Research Council. With the exception of electric propulsion systems used for commercial communications satellite station-keeping and a handful of deep space science missions, almost all of the rocket engines in use today are chemical rockets; that is, they obtain the energy needed to generate thrust by combining reactive chemicals to create a hot gas that is expanded to produce thrust. A significant limitation of chemical propulsion is that it has a relatively low specific impulse. Numerous concepts for advanced propulsion technologies with significantly higher values of specific impulse have been developed over the past 50 years. Advanced in-space propulsion technologies will enable much more effective exploration of our solar system, near and far, and will permit mission designers to plan missions to "fly anytime, anywhere, and complete a host of science objectives at the destinations" with greater reliability and safety. With a wide range of possible missions and candidate propulsion technologies with very diverse characteristics, the question of which technologies are 'best' for future missions is a difficult one. A portfolio of technologies to allow optimum propulsion solutions for a diverse set of missions and destinations are described in the roadmap and herein.

A Small Modular Laboratory Hall Effect Thruster

NASA Astrophysics Data System (ADS)

Lee, Ty Davis

Electric propulsion technologies promise to revolutionize access to space, opening the door for mission concepts unfeasible by traditional propulsion methods alone. The Hall effect thruster is a relatively high thrust, moderate specific impulse electric propulsion device that belongs to the class of electrostatic thrusters. Hall effect thrusters benefit from an extensive flight history, and offer significant performance and cost advantages when compared to other forms of electric propulsion. Ongoing research on these devices includes the investigation of mechanisms that tend to decrease overall thruster efficiency, as well as the development of new techniques to extend operational lifetimes. This thesis is primarily concerned with the design and construction of a Small Modular Laboratory Hall Effect Thruster (SMLHET), and its operation on argon propellant gas. Particular attention was addressed at low-cost, modular design principles, that would facilitate simple replacement and modification of key thruster parts such as the magnetic circuit and discharge channel. This capability is intended to facilitate future studies of device physics such as anomalous electron transport and magnetic shielding of the channel walls, that have an impact on thruster performance and life. Preliminary results demonstrate SMLHET running on argon in a manner characteristic of Hall effect thrusters, additionally a power balance method was utilized to estimate thruster performance. It is expected that future thruster studies utilizing heavier though more expensive gases like xenon or krypton, will observe increased efficiency and stability.

Magnetic Nozzle Simulation Studies for Electric Propulsion

NASA Astrophysics Data System (ADS)

Tarditi, Alfonso

2010-11-01

Electric Propulsion has recently re-gained interest as one of the key technologies to enable NASA's long-range space missions. Options are being considered also in the field of aneutronic fusion propulsion for high-power electric thrusters. To support these goals the study of the exhaust jet in a plasma thruster acquires a critical importance because the need of high-efficiency generation of thrust. A model of the plasma exhaust has been developed with the 3D magneto-fluid NIMROD code [1] to study the physics of the plasma detachment in correlation with experimentally relevant configurations. The simulations show the role of the plasma diamagnetism and of the magnetic reconnection process in the formation of a detached plasma. Furthermore, in direct fusion-propulsion concepts high-energy (MeV range) fusion products have to be efficiently converted into a slower and denser plasma jet (with specific impulse down to few 1000's seconds, for realistic missions in the Solar System). For this purpose, a two-stage conversion process is being modeled where high-energy ions are non-adiabatically injected and confined into a magnetic duct leading to the magnetic nozzle, transferring most of their energy into their gyro-motion and drifting at slower speed along with the plasma propellant. The propellant acquires then thermal energy that gets converted into the direction of thrust by the magnetic nozzle. [1] C. R. Sovinec et al., J. Comput. Phys. 195, 355 (2004).

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.

100 GHz pulse waveform measurement based on electro-optic sampling

NASA Astrophysics Data System (ADS)

Feng, Zhigang; Zhao, Kejia; Yang, Zhijun; Miao, Jingyuan; Chen, He

2018-05-01

We present an ultrafast pulse waveform measurement system based on an electro-optic sampling technique at 1560 nm and prepare LiTaO3-based electro-optic modulators with a coplanar waveguide structure. The transmission and reflection characteristics of electrical pulses on a coplanar waveguide terminated with an open circuit and a resistor are investigated by analyzing the corresponding time-domain pulse waveforms. We measure the output electrical pulse waveform of a 100 GHz photodiode and the obtained rise times of the impulse and step responses are 2.5 and 3.4 ps, respectively.

A test technique for measuring lightning-induced voltages on aircraft electrical circuits

NASA Technical Reports Server (NTRS)

Walko, L. C.

1974-01-01

The development of a test technique used for the measurement of lightning-induced voltages in the electrical circuits of a complete aircraft is described. The resultant technique utilizes a portable device known as a transient analyzer capable of generating unidirectional current impulses similar to lightning current surges, but at a lower current level. A linear relationship between the magnitude of lightning current and the magnitude of induced voltage permitted the scaling up of measured induced values to full threat levels. The test technique was found to be practical when used on a complete aircraft.

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.

The X3: A 200 kW Class Nested Channel Hall Thruster

NASA Astrophysics Data System (ADS)

Sheehan, J. P.

2016-10-01

Electric propulsion has seen rapid adoption in recent years for commercial, scientific, and exploratory space missions. The X3 is a three channel nested channel Hall thruster, designed to push the boundaries of high power electric propulsion for cargo transfer to Mars and large military assets. It has been operated at thermal steady state up to 30 kW of power. Thrust measurements were made on an inverted pendulum thrust stand, indicating over 2000 s specific impulse and 65 mN/kW thrust to power ratio. Detailed plume measurements were made with Faraday and Langmuir probes. The multiple concentric channels provide better performance than the sum of the individual channel operations due to superior propellant utilization from its compact design. Using a high speed camera, the breathing and spoke mode instabilities were captured in all three channels. Spoke and breathing instabilities couple between the channels, indicating that complex plasma and neutral interactions are at play. Electron transport, both cross field and in the cathode plume, are well suited to be explored in a thruster of this size. Supported under NASA contract No. NNH16CP17C.

CVD Rhenium Engines for Solar-Thermal Propulsion Systems

NASA Technical Reports Server (NTRS)

Williams, Brian E.; Fortini, Arthur J.; Tuffias, Robert H.; Duffy, Andrew J.; Tucker, Stephen P.

1999-01-01

Solar-thermal upper-stage propulsion systems have the potential to provide specific impulse approaching 900 seconds, with 760 seconds already demonstrated in ground testing. Such performance levels offer a 100% increase in payload capability compared to state-of-the-art chemical upper-stage systems, at lower cost. Although alternatives such as electric propulsion offer even greater performance, the 6- to 18- month orbital transfer time is a far greater deviation from the state of the art than the one to two months required for solar propulsion. Rhenium metal is the only material that is capable of withstanding the predicted thermal, mechanical, and chemical environment of a solar-thermal propulsion device. Chemical vapor deposition (CVD) is the most well-established and cost-effective process for the fabrication of complex rhenium structures. CVD rhenium engines have been successfully constructed for the Air Force ISUS program (bimodal thrust/electricity) and the NASA Shooting Star program (thrust only), as well as under an Air Force SBIR project (thrust only). The bimodal engine represents a more long-term and versatile approach to solar-thermal propulsion, while the thrust-only engines provide a potentially lower weight/lower cost and more near-term replacement for current upper-stage propulsion systems.

Characteristics of return stroke electric fields produced by lightning flashes at distances of 1 to 15 kilometers

NASA Technical Reports Server (NTRS)

Hopf, CH.

1991-01-01

Electric field derivative signals from single and multiple lightning strokes are presented. For about 25 pct. of all acquired waveforms, produced by return strokes, stepped leaders or intracloud discharges, type and distance of the signal source are known from the observations by an all sky video camera system. The analysis of the electric field derivative waveforms in the time domain shows a significant difference in the impulse width between return stroke signals and those of stepped leaders and intracloud discharges. In addition, the computed amplitude density spectrum of return stroke waveforms lies by a factor of 10 above that of stepped leaders and intracloud discharges in the frequency range from 50 to 500 kHz.

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.

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.

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.