Solar Dynamics Observatory On-Orbit Jitter Testing, Analysis, and Mitigation Plans

NASA Technical Reports Server (NTRS)

Liu, Kuo-Chia; Blaurock, Carl A.; Bourkland, Kristin L.; Morgenstern, Wendy M.; Maghami, Peiman G.

2011-01-01

The recently launched Solar Dynamics Observatory (SDO) has two science instruments onboard that required sub-arcsecond pointing stability. Significant effort has been spent pre-launch to characterize the disturbances sources and validating jitter level at the component, sub-assembly, and spacecraft levels. However, an end-to-end jitter test emulating the flight condition was not performed on the ground due to cost and risk concerns. As a result, the true jitter level experienced on orbit remained uncertain prior to launch. Based on the pre-launch analysis, several operational constraints were placed on the observatory aimed to minimize the instrument jitter levels. If the actual jitter is below the analysis predictions, these operational constraints can be relaxed to reduce the burden of the flight operations team. The SDO team designed a three-day jitter test, utilizing the instrument sensors to measure pointing jitter up to 256 Hz. The test results were compared to pre-launch analysis predictions, used to determine which operational constraints can be relaxed, and analyzed for setting the jitter mitigation strategies for future SDO operations.

Non-Gaussian statistics of soliton timing jitter induced by amplifier noise.

PubMed

Ho, Keang-Po

2003-11-15

Based on first-order perturbation theory of the soliton, the Gordon-Haus timing jitter induced by amplifier noise is found to be non-Gaussian distributed. Both frequency and timing jitter have larger tail probabilities than Gaussian distribution given by the linearized perturbation theory. The timing jitter has a larger discrepancy from Gaussian distribution than does the frequency jitter.

Tape recorder effects on jitter and shimmer extraction.

PubMed

Doherty, E T; Shipp, T

1988-09-01

To test for possible contamination of acoustic analyses by record/reproduce systems, five sine waves of fixed frequency and amplitude were sampled directly by a computer and recorded simultaneously on four different tape formats (audio and FM reel-to-reel, audio cassette, and video cassette using pulse code modulation). Recordings were digitized on playback and with the direct samples analyzed for fundamental frequency, amplitude, jitter, and shimmer using a zero crossing interpolation scheme. Distortion introduced by any of the data acquisition systems is negligible when extracting average fundamental frequency or average amplitude. For jitter and shimmer estimation, direct sampling or the use of a video cassette recorder with pulse code modulation are clearly superior. FM recorders, although not quite as accurate, provide a satisfactory alternative to those methods. Audio reel-to-reel recordings are marginally adequate for jitter analysis whereas audio cassette recorders can introduce jitter and shimmer values that are greater than some reported values for normal talkers.

Goodbye Critter Jitters

ERIC Educational Resources Information Center

Eidietis, Laura; Gray, Stacey; Riggs, Leela; West, Bridgette; Coffman, Margaret

2007-01-01

What invertebrates make the best classroom pets? How should we care for each invertebrate? What type of inquiry activities could invertebrates support? How do elementary students respond to invertebrates? These were the questions investigated in The Critter Project, a three-week project that aimed to help students conquer their "critter jitters"…

Spark gap with low breakdown voltage jitter

DOEpatents

Rohwein, G.J.; Roose, L.D.

1996-04-23

Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed. 13 figs.

An Adaptive Jitter Mechanism for Reactive Route Discovery in Sensor Networks

PubMed Central

Cordero, Juan Antonio; Yi, Jiazi; Clausen, Thomas

2014-01-01

This paper analyses the impact of jitter when applied to route discovery in reactive (on-demand) routing protocols. In multi-hop non-synchronized wireless networks, jitter—a small, random variation in the timing of message emission—is commonly employed, as a means to avoid collisions of simultaneous transmissions by adjacent routers over the same channel. In a reactive routing protocol for sensor and ad hoc networks, jitter is recommended during the route discovery process, specifically, during the network-wide flooding of route request messages, in order to avoid collisions. Commonly, a simple uniform jitter is recommended. Alas, this is not without drawbacks: when applying uniform jitter to the route discovery process, an effect called delay inversion is observed. This paper, first, studies and quantifies this delay inversion effect. Second, this paper proposes an adaptive jitter mechanism, designed to alleviate the delay inversion effect and thereby to reduce the route discovery overhead and (ultimately) allow the routing protocol to find more optimal paths, as compared to uniform jitter. This paper presents both analytical and simulation studies, showing that the proposed adaptive jitter can effectively decrease the cost of route discovery and increase the path quality. PMID:25111238

Corrective jitter motion shows similar individual frequencies for the arm and the finger.

PubMed

Noy, Lior; Alon, Uri; Friedman, Jason

2015-04-01

A characteristic of visuomotor tracking of non-regular oscillating stimuli are high-frequency jittery corrective motions, oscillating around the tracked stimuli. However, the properties of these corrective jitter responses are not well understood. For example, does the jitter response show an idiosyncratic signature? What is the relationship between stimuli properties and jitter properties? Is the jitter response similar across effectors with different inertial properties? To answer these questions, we measured participants' jitter frequencies in two tracking tasks in the arm and the finger. Thirty participants tracked the same set of eleven non-regular oscillating stimuli, vertically moving on a screen, once with forward-backward arm movements (holding a tablet stylus) and once with upward-downward index finger movements (with a motion tracker attached). Participants' jitter frequencies and tracking errors varied systematically as a function of stimuli frequency and amplitude. Additionally, there were clear individual differences in average jitter frequencies between participants, ranging from 0.7 to 1.15 Hz, similar to values reported previously. A comparison of individual jitter frequencies in the two tasks showed a strong correlation between participants' jitter frequencies in the finger and the arm, despite the very different inertial properties of the two effectors. This result suggests that the corrective jitter response stems from common neural processes.

UARS in-flight jitter study for EOS

NASA Technical Reports Server (NTRS)

Molnar, John; Garnek, Mike

1993-01-01

Response data collected from gyroscopes on board the Upper Atmosphere Research Satellite (UARS) provided a unique opportunity to analyze actual flight pointing jitter data. Flight modal frequencies and damping values are derived from the measured data using an Eigensystem Realization Algorithm (ERA). Flight frequencies at various solar array positions are compared to analytical predictions obtained with a Finite Element Model. The solar array modal frequencies change with position due to the modes acting about different spacecraft inertial axes. Higher order modes were difficult to identify due to the limited instrumentation. Future flight jitter studies on other spacecraft would be significantly aided by additional instrumentation. Spacecraft jitter due to continuous disturbance sources such as the 1.6 meter scanning microwave antenna, the solar array drive, and reaction wheels is presented. The solar array drive disturbance dominates the spacecraft response during normal operation.

Influence of the platform jitter on intensity fluctuation for laser launch system

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Qiao, Chunhong; Huang, Tong; Zhang, Jinghui; Fan, Chengyu

2017-10-01

The jitter of the transmitting system can cause the light intensity fluctuation at the target position of the laser transmission, which affects the performance of the laser communication, imaging and the adaptive optical system. In this paper, the platform jitter is modeled by Gaussian random fluctuation phase and the analytic expression of the system jitter effect on the fluctuation of light intensity is obtained under the vacuum condition based on extended Huygens-Fresnel principle. The numerical simulation is compared with the theoretical expression and the consistency is obtained. At the same time, the influence of the jitter of the launch system on the intensity fluctuation of the target system under different turbulence conditions is analyzed by numerical simulation. The result show that normalized intensity fluctuation variance induced by platform jitter seems to be unrestricted. The jitter of the transmitting system has a more important influence on the fluctuation of the target position caused by the atmospheric turbulence, as the jitter increase. This result provides a reference for the application of the actual laser transmission system.

Image jitter enhances visual performance when spatial resolution is impaired.

PubMed

Watson, Lynne M; Strang, Niall C; Scobie, Fraser; Love, Gordon D; Seidel, Dirk; Manahilov, Velitchko

2012-09-06

Visibility of low-spatial frequency stimuli improves when their contrast is modulated at 5 to 10 Hz compared with stationary stimuli. Therefore, temporal modulations of visual objects could enhance the performance of low vision patients who primarily perceive images of low-spatial frequency content. We investigated the effect of retinal-image jitter on word recognition speed and facial emotion recognition in subjects with central visual impairment. Word recognition speed and accuracy of facial emotion discrimination were measured in volunteers with AMD under stationary and jittering conditions. Computer-driven and optoelectronic approaches were used to induce retinal-image jitter with duration of 100 or 166 ms and amplitude within the range of 0.5 to 2.6° visual angle. Word recognition speed was also measured for participants with simulated (Bangerter filters) visual impairment. Text jittering markedly enhanced word recognition speed for people with severe visual loss (101 ± 25%), while for those with moderate visual impairment, this effect was weaker (19 ± 9%). The ability of low vision patients to discriminate the facial emotions of jittering images improved by a factor of 2. A prototype of optoelectronic jitter goggles produced similar improvement in facial emotion discrimination. Word recognition speed in participants with simulated visual impairment was enhanced for interjitter intervals over 100 ms and reduced for shorter intervals. Results suggest that retinal-image jitter with optimal frequency and amplitude is an effective strategy for enhancing visual information processing in the absence of spatial detail. These findings will enable the development of novel tools to improve the quality of life of low vision patients.

Zero-crossing detector with sub-microsecond jitter and crosstalk

NASA Technical Reports Server (NTRS)

Dick, G. John; Kuhnle, Paul F.; Sydnor, Richard L.

1990-01-01

A zero-crossing detector (ZCD) was built and tested with a new circuit design which gives reduced time jitter compared to previous designs. With the new design, time jitter is reduced for the first time to a value which approaches that due to noise in the input amplifying stage. Additionally, with fiber-optic transmission of the output signal, crosstalk between units has been eliminated. The measured values are in good agreement with circuit noise calculations and approximately ten times lower than that for ZCD's presently installed in the JPL test facility. Crosstalk between adjacent units was reduced even more than the jitter.

Correcting spacecraft jitter in HiRISE images

USGS Publications Warehouse

Sutton, S. S.; Boyd, A.K.; Kirk, Randolph L.; Cook, Debbie; Backer, Jean; Fennema, A.; Heyd, R.; McEwen, A.S.; Mirchandani, S.D.; Wu, B.; Di, K.; Oberst, J.; Karachevtseva, I.

2017-01-01

Mechanical oscillations or vibrations on spacecraft, also called pointing jitter, cause geometric distortions and/or smear in high resolution digital images acquired from orbit. Geometric distortion is especially a problem with pushbroom type sensors, such as the High Resolution Imaging Science Experiment (HiRISE) instrument on board the Mars Reconnaissance Orbiter (MRO). Geometric distortions occur at a range of frequencies that may not be obvious in the image products, but can cause problems with stereo image correlation in the production of digital elevation models, and in measuring surface changes over time in orthorectified images. The HiRISE focal plane comprises a staggered array of fourteen charge-coupled devices (CCDs) with pixel IFOV of 1 microradian. The high spatial resolution of HiRISE makes it both sensitive to, and an excellent recorder of jitter. We present an algorithm using Fourier analysis to resolve the jitter function for a HiRISE image that is then used to update instrument pointing information to remove geometric distortions from the image. Implementation of the jitter analysis and image correction is performed on selected HiRISE images. Resulting corrected images and updated pointing information are made available to the public. Results show marked reduction of geometric distortions. This work has applications to similar cameras operating now, and to the design of future instruments (such as the Europa Imaging System).

Active suppression of acoustically induced jitter for the airborne laser

NASA Astrophysics Data System (ADS)

Glaese, Roger M.; Anderson, Eric H.; Janzen, Paul C.

2000-07-01

The Airborne Laser (ABL) system has extremely tight jitter requirements. Acoustic disturbances, such as those caused by the pressure recovery system of the high power laser, are a significant jitter source. Several technologies may be appropriate for reducing the acoustically induced jitter. The first choice for mitigation will be passive approaches, such as acoustic blankets. There is, however, some uncertainty whether these approaches will provide sufficient attenuation and there is concern about the weight of these approaches. A testbed that captured the fundamental physics of the ABL acoustically induced optical jitter problem was developed. This testbed consists of a flexure-mounted mirror exposed to an acoustic field that is generated outside a beam tube and then propagates within the tube. Both feedback and adaptive feedforward control topologies were implemented on the testbed using either of two actuators (a fast steering mirror and a secondary acoustic speaker located near the precision mirror), and a variety of sensors (microphones measuring the acoustic disturbance, accelerometers and microphones mounted on the precision optic, and an optical position sensing detector). This paper summarizes the results from these control topologies for reducing the acoustically induced jitter with some control topologies achieving in excess of 40 dB jitter reduction at a single frequency. This work was performed under an SBIR Phase I funded by the Air Force Research Laboratory Space Vehicles Directorate.

Somatosensory spatial attention modulates amplitudes, latencies, and latency jitter of laser-evoked brain potentials.

PubMed

Franz, Marcel; Nickel, Moritz M; Ritter, Alexander; Miltner, Wolfgang H R; Weiss, Thomas

2015-04-01

Several studies provided evidence that the amplitudes of laser-evoked potentials (LEPs) are modulated by attention. However, previous reports were based on across-trial averaging of LEP responses at the expense of losing information about intertrial variability related to attentional modulation. The aim of this study was to investigate the effects of somatosensory spatial attention on single-trial parameters (i.e., amplitudes, latencies, and latency jitter) of LEP components (N2 and P2). Twelve subjects participated in a sustained spatial attention paradigm while noxious laser stimuli (left hand) and noxious electrical stimuli (right hand) were sequentially delivered to the dorsum of the respective hand with nonnoxious air puffs randomly interspersed within the sequence of noxious stimuli. Participants were instructed to mentally count all stimuli (i.e., noxious and nonnoxious) applied to the attended location. Laser stimuli, presented to the attended hand (ALS), elicited larger single-trial amplitudes of the N2 component compared with unattended laser stimuli (ULS). In contrast, single-trial amplitudes of the P2 component were not significantly affected by spatial attention. Single-trial latencies of the N2 and P2 were significantly smaller for ALS vs. ULS. Additionally, the across-trial latency jitter of the N2 component was reduced for ALS. Conversely, the latency jitter of the P2 component was smaller for ULS compared with ALS. With the use of single-trial analysis, the study provided new insights into brain dynamics of LEPs related to spatial attention. Our results indicate that single-trial parameters of LEP components are differentially modulated by spatial attention. Copyright © 2015 the American Physiological Society.

Adaptive Filter Techniques for Optical Beam Jitter Control and Target Tracking

DTIC Science & Technology

2008-12-01

OPTICAL BEAM JITTER CONTROL AND TARGET TRACKING Michael J. Beerer Civilian, United States Air Force B.S., University of California Irvine, 2006...TECHNIQUES FOR OPTICAL BEAM JITTER CONTROL AND TARGET TRACKING by Michael J. Beerer December 2008 Thesis Advisor: Brij N. Agrawal Co...DATE December 2008 3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE Adaptive Filter Techniques for Optical Beam Jitter

Jitter Reduces Response-Time Variability in ADHD: An Ex-Gaussian Analysis.

PubMed

Lee, Ryan W Y; Jacobson, Lisa A; Pritchard, Alison E; Ryan, Matthew S; Yu, Qilu; Denckla, Martha B; Mostofsky, Stewart; Mahone, E Mark

2015-09-01

"Jitter" involves randomization of intervals between stimulus events. Compared with controls, individuals with ADHD demonstrate greater intrasubject variability (ISV) performing tasks with fixed interstimulus intervals (ISIs). Because Gaussian curves mask the effect of extremely slow or fast response times (RTs), ex-Gaussian approaches have been applied to study ISV. This study applied ex-Gaussian analysis to examine the effects of jitter on RT variability in children with and without ADHD. A total of 75 children, aged 9 to 14 years (44 ADHD, 31 controls), completed a go/no-go test with two conditions: fixed ISI and jittered ISI. ADHD children showed greater variability, driven by elevations in exponential (tau), but not normal (sigma) components of the RT distribution. Jitter decreased tau in ADHD to levels not statistically different than controls, reducing lapses in performance characteristic of impaired response control. Jitter may provide a nonpharmacologic mechanism to facilitate readiness to respond and reduce lapses from sustained (controlled) performance. © 2012 SAGE Publications.

A pattern jitter free AFC scheme for mobile satellite systems

NASA Technical Reports Server (NTRS)

Yoshida, Shousei

1993-01-01

This paper describes a scheme for pattern jitter free automatic frequency control (AFC) with a wide frequency acquisition range. In this scheme, equalizing signals fed to the frequency discriminator allow pattern jitter free performance to be achieved for all roll-off factors. In order to define the acquisition range, frequency discrimination characateristics are analyzed on a newly derived frequency domain model. As a result, it is shown that a sufficiently wide acquisition range over a given system symbol rate can be achieved independent of symbol timing errors. Additionally, computer simulation demonstrates that frequency jitter performance improves in proportion to E(sub b)/N(sub 0) because pattern-dependent jitter is suppressed in the discriminator output. These results show significant promise for applciation to mobile satellite systems, which feature relatively low symbol rate transmission with an approximately 0.4-0.7 roll-off factor.

Genomic instability and bystander effects: a paradigm shift in radiation biology?

NASA Technical Reports Server (NTRS)

Morgan, William F.

2002-01-01

A basic paradigm in radiobiology is that, following exposure to ionizing radiation, the deposition of energy in the cell nucleus and the resulting damage to DNA, the principal target, are responsible for the radiation's deleterious biological effects. Findings in two rapidly expanding fields of research--radiation-induced genomic instability and bystander effects--have caused us to reevaluate these central tenets. In this article, the potential influence of induced genomic instability and bystander effects on cellular injury after exposure to low-level radiation will be reviewed.

Voice Signals Produced With Jitter Through a Stochastic One-mass Mechanical Model.

PubMed

Cataldo, Edson; Soize, Christian

2017-01-01

The quasiperiodic oscillation of the vocal folds causes perturbations in the length of the glottal cycles, which are known as jitter. The observation of the glottal cycles variations suggests that jitter is a random phenomenon described by random deviations of the glottal cycle lengths in relation to a corresponding mean value and, in general, its values are expressed as a percentage of the duration of the glottal pulse. The objective of this paper is the construction of a stochastic model for jitter using a one-mass mechanical model of the vocal folds, which assumes complete right-left symmetry of the vocal folds, and which considers motions of the vocal folds only in the horizontal direction. The jitter has been the subject for researchers due to its important applications such as the identification of pathological voices (nodules in the vocal folds, paralysis of the vocal folds, or even, the vocal aging, among others). Large values for jitter variations can indicate a pathological characteristic of the voice. The corresponding stiffness of each vocal fold is considered as a stochastic process, and its modeling is proposed. The probability density function of the fundamental frequency related to the voice signals produced are constructed and compared for different levels of jitter. Some samples of synthesized voices in these cases are obtained. It is showed that jitter could be obtained using the model proposed. The Praat software was also used to verify the measures of jitter in the synthesized voice signals. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Remote distribution of a mode-locked pulse train with sub 40-as jitter

NASA Astrophysics Data System (ADS)

Chen, Yi-Fei; Jiang, Jie; Jones, David J.

2006-12-01

Remote transfer of an ultralow-jitter microwave frequency reference signal is demonstrated using the pulse trains generated by a mode-locked fiber laser. The timing jitter in a ~ 30-m fiber link is reduced to 38 attoseconds (as) integrated over a bandwidth from 1 Hz to 10 MHz via active stabilization which represents a significant improvement over previously reported jitter performance. Our approach uses an all-optical generation of the synchronization error signal and an accompanying out-of-loop optical detection technique to verify the jitter performance.

Physical mechanisms of timing jitter in photon detection by current-carrying superconducting nanowires

NASA Astrophysics Data System (ADS)

Sidorova, Mariia; Semenov, Alexej; Hübers, Heinz-Wilhelm; Charaev, Ilya; Kuzmin, Artem; Doerner, Steffen; Siegel, Michael

2017-11-01

We studied timing jitter in the appearance of photon counts in meandering nanowires with different fractional amount of bends. Intrinsic timing jitter, which is the probability density function of the random time delay between photon absorption in current-carrying superconducting nanowire and appearance of the normal domain, reveals two different underlying physical mechanisms. In the deterministic regime, which is realized at large photon energies and large currents, jitter is controlled by position-dependent detection threshold in straight parts of meanders. It decreases with the increase in the current. At small photon energies, jitter increases and its current dependence disappears. In this probabilistic regime jitter is controlled by Poisson process in that magnetic vortices jump randomly across the wire in areas adjacent to the bends.

Jitter Test Program and On-Orbit Mitigation Strategies for Solar Dynamic Observatory

NASA Technical Reports Server (NTRS)

Liu, Kuo-Chia; Kenney, Thomas; Maghami, Peiman; Mule, Pete; Blaurock, Carl; Haile, William B.

2007-01-01

The Solar Dynamic Observatory (SDO) aims to study the Sun's influence on the Earth, the source, storage, and release of the solar energy, and the interior structure of the Sun. During science observations, the jitter stability at the instrument focal plane must be maintained to less than a fraction of an arcsecond for two of the SDO instruments. To meet these stringent requirements, a significant amount of analysis and test effort has been devoted to predicting the jitter induced from various disturbance sources. This paper presents an overview of the SDO jitter analysis approach and test effort performed to date. It emphasizes the disturbance modeling, verification, calibration, and validation of the high gain antenna stepping mechanism and the reaction wheels, which are the two largest jitter contributors. This paper also describes on-orbit mitigation strategies to protect the system from analysis model uncertainties. Lessons learned from the SDO jitter analyses and test programs are included in the paper to share the knowledge gained with the community.

Jitter model and signal processing techniques for pulse width modulation optical recording

NASA Technical Reports Server (NTRS)

Liu, Max M.-K.

1991-01-01

A jitter model and signal processing techniques are discussed for data recovery in Pulse Width Modulation (PWM) optical recording. In PWM, information is stored through modulating sizes of sequential marks alternating in magnetic polarization or in material structure. Jitter, defined as the deviation from the original mark size in the time domain, will result in error detection if it is excessively large. A new approach is taken in data recovery by first using a high speed counter clock to convert time marks to amplitude marks, and signal processing techniques are used to minimize jitter according to the jitter model. The signal processing techniques include motor speed and intersymbol interference equalization, differential and additive detection, and differential and additive modulation.

Fully-Coupled Dynamical Jitter Modeling of Momentum Exchange Devices

NASA Astrophysics Data System (ADS)

Alcorn, John

A primary source of spacecraft jitter is due to mass imbalances within momentum exchange devices (MEDs) used for fine pointing, such as reaction wheels (RWs) and variable-speed control moment gyroscopes (VSCMGs). Although these effects are often characterized through experimentation in order to validate pointing stability requirements, it is of interest to include jitter in a computer simulation of the spacecraft in the early stages of spacecraft development. An estimate of jitter amplitude may be found by modeling MED imbalance torques as external disturbance forces and torques on the spacecraft. In this case, MED mass imbalances are lumped into static and dynamic imbalance parameters, allowing jitter force and torque to be simply proportional to wheel speed squared. A physically realistic dynamic model may be obtained by defining mass imbalances in terms of a wheel center of mass location and inertia tensor. The fully-coupled dynamic model allows for momentum and energy validation of the system. This is often critical when modeling additional complex dynamical behavior such as flexible dynamics and fuel slosh. Furthermore, it is necessary to use the fully-coupled model in instances where the relative mass properties of the spacecraft with respect to the RWs cause the simplified jitter model to be inaccurate. This thesis presents a generalized approach to MED imbalance modeling of a rigid spacecraft hub with N RWs or VSCMGs. A discussion is included to convert from manufacturer specifications of RW imbalances to the parameters introduced within each model. Implementations of the fully-coupled RW and VSCMG models derived within this thesis are released open-source as part of the Basilisk astrodynamics software.

Study of Magnetic Damping Effect on Convection and Solidification Under G-Jitter Conditions

NASA Technical Reports Server (NTRS)

Li, Ben Q.; deGroh, H. C., III

1999-01-01

As shown by NASA resources dedicated to measuring residual gravity (SAMS and OARE systems), g-jitter is a critical issue affecting space experiments on solidification processing of materials. This study aims to provide, through extensive numerical simulations and ground based experiments, an assessment of the use of magnetic fields in combination with microgravity to reduce the g-jitter induced convective flows in space processing systems. We have so far completed asymptotic analyses based on the analytical solutions for g-jitter driven flow and magnetic field damping effects for a simple one-dimensional parallel plate configuration, and developed both 2-D and 3-D numerical models for g-jitter driven flows in simple solidification systems with and without presence of an applied magnetic field. Numerical models have been checked with the analytical solutions and have been applied to simulate the convective flows and mass transfer using both synthetic g-jitter functions and the g-jitter data taken from space flight. Some useful findings have been obtained from the analyses and the modeling results. Some key points may be summarized as follows: (1) the amplitude of the oscillating velocity decreases at a rate inversely proportional to the g-jitter frequency and with an increase in the applied magnetic field; (2) the induced flow approximately oscillates at the same frequency as the affecting g-jitter, but out of a phase angle; (3) the phase angle is a complicated function of geometry, applied magnetic field, temperature gradient and frequency; (4) g-jitter driven flows exhibit a complex fluid flow pattern evolving in time; (5) the damping effect is more effective for low frequency flows; and (6) the applied magnetic field helps to reduce the variation of solutal distribution along the solid-liquid interface. Work in progress includes numerical simulations and ground-based measurements. Both 2-D and 3-D numerical simulations are being continued to obtain further

Reaction Wheel Disturbance Modeling, Jitter Analysis, and Validation Tests for Solar Dynamics Observatory

NASA Technical Reports Server (NTRS)

Liu,Kuo-Chia; Maghami, Peiman; Blaurock, Carl

2008-01-01

The Solar Dynamics Observatory (SDO) aims to study the Sun's influence on the Earth by understanding the source, storage, and release of the solar energy, and the interior structure of the Sun. During science observations, the jitter stability at the instrument focal plane must be maintained to less than a fraction of an arcsecond for two of the SDO instruments. To meet these stringent requirements, a significant amount of analysis and test effort has been devoted to predicting the jitter induced from various disturbance sources. One of the largest disturbance sources onboard is the reaction wheel. This paper presents the SDO approach on reaction wheel disturbance modeling and jitter analysis. It describes the verification and calibration of the disturbance model, and ground tests performed for validating the reaction wheel jitter analysis. To mitigate the reaction wheel disturbance effects, the wheels will be limited to operate at low wheel speeds based on the current analysis. An on-orbit jitter test algorithm is also presented in the paper which will identify the true wheel speed limits in order to ensure that the wheel jitter requirements are met.

A low timing jitter picosecond microchip laser pumped by pulsed LD

NASA Astrophysics Data System (ADS)

Wang, Sha; Wang, Yan-biao; Feng, Guoying; Zhou, Shou-huan

2016-07-01

SESAM passively Q-switched microchip laser is a very promising instrument to replace mode locked lasers to obtain picosecond pulses. The biggest drawback of a passively Q-switched microchip laser is its un-avoided large timing jitter, especially when the pump intensity is low, i.e. at low laser repetition rate range. In order to obtain a low timing jitter passively Q-switched picosecond microchip laser in the whole laser repetition rate range, a 1000 kHz pulsed narrow bandwidth Fiber Bragg Grating (FBG) stablized laser diode was used as the pump source. By tuning the pump intensity, we could control the output laser frequency. In this way, we achieved a very low timing jitter passively Q-switched picosecond laser at 2.13 mW, 111.1 kHz. The relative timing jitter was only 0.0315%, which was around 100 times smaller compared with a cw LD pumped microchip working at hundred kilohertz repetition rate frequency range.

Measuring the jitter of ring oscillators by means of information theory quantifiers

NASA Astrophysics Data System (ADS)

Antonelli, M.; De Micco, L.; Larrondo, H. A.

2017-02-01

Ring oscillators (RO's) are elementary blocks widely used in digital design. Jitter is unavoidable in RO's, its presence is an undesired behavior in many applications, as clock generators. On the contrary, jitter may be used as the noise source in RO-based true-random numbers generators (TRNG). Consequently, jitter measure is a relevant issue to characterize a RO, and it is the subject of this paper. The main contribution is the use of Information Theory Quantifiers (ITQ) as measures of RO's jitter. It is shown that among several ITQ evaluated, two of them emerge as good measures because they are independent of parameters used for their statistical determination. They turned out to be robust and may be implemented experimentally. We encountered that a dual entropy plane allows a visual comparison of results.

Reference-free, high-resolution measurement method of timing jitter spectra of optical frequency combs

PubMed Central

Kwon, Dohyeon; Jeon, Chan-Gi; Shin, Junho; Heo, Myoung-Sun; Park, Sang Eon; Song, Youjian; Kim, Jungwon

2017-01-01

Timing jitter is one of the most important properties of femtosecond mode-locked lasers and optical frequency combs. Accurate measurement of timing jitter power spectral density (PSD) is a critical prerequisite for optimizing overall noise performance and further advancing comb applications both in the time and frequency domains. Commonly used jitter measurement methods require a reference mode-locked laser with timing jitter similar to or lower than that of the laser-under-test, which is a demanding requirement for many laser laboratories, and/or have limited measurement resolution. Here we show a high-resolution and reference-source-free measurement method of timing jitter spectra of optical frequency combs using an optical fibre delay line and optical carrier interference. The demonstrated method works well for both mode-locked oscillators and supercontinua, with 2 × 10−9 fs2/Hz (equivalent to −174 dBc/Hz at 10-GHz carrier frequency) measurement noise floor. The demonstrated method can serve as a simple and powerful characterization tool for timing jitter PSDs of various comb sources including mode-locked oscillators, supercontinua and recently emerging Kerr-frequency combs; the jitter measurement results enabled by our method will provide new insights for understanding and optimizing timing noise in such comb sources. PMID:28102352

Least-squares deconvolution of evoked potentials and sequence optimization for multiple stimuli under low-jitter conditions.

PubMed

Bardy, Fabrice; Dillon, Harvey; Van Dun, Bram

2014-04-01

Rapid presentation of stimuli in an evoked response paradigm can lead to overlap of multiple responses and consequently difficulties interpreting waveform morphology. This paper presents a deconvolution method allowing overlapping multiple responses to be disentangled. The deconvolution technique uses a least-squared error approach. A methodology is proposed to optimize the stimulus sequence associated with the deconvolution technique under low-jitter conditions. It controls the condition number of the matrices involved in recovering the responses. Simulations were performed using the proposed deconvolution technique. Multiple overlapping responses can be recovered perfectly in noiseless conditions. In the presence of noise, the amount of error introduced by the technique can be controlled a priori by the condition number of the matrix associated with the used stimulus sequence. The simulation results indicate the need for a minimum amount of jitter, as well as a sufficient number of overlap combinations to obtain optimum results. An aperiodic model is recommended to improve reconstruction. We propose a deconvolution technique allowing multiple overlapping responses to be extracted and a method of choosing the stimulus sequence optimal for response recovery. This technique may allow audiologists, psychologists, and electrophysiologists to optimize their experimental designs involving rapidly presented stimuli, and to recover evoked overlapping responses. Copyright © 2013 International Federation of Clinical Neurophysiology. All rights reserved.

Finite Element Analysis of Magnetic Damping Effects on G-Jitter Induced Fluid Flow

NASA Technical Reports Server (NTRS)

Pan, Bo; Li, Ben Q.; deGroh, Henry C., III

1997-01-01

This paper reports some interim results on numerical modeling and analyses of magnetic damping of g-jitter driven fluid flow in microgravity. A finite element model is developed to represent the fluid flow, thermal and solute transport phenomena in a 2-D cavity under g-jitter conditions with and without an applied magnetic field. The numerical model is checked by comparing with analytical solutions obtained for a simple parallel plate channel flow driven by g-jitter in a transverse magnetic field. The model is then applied to study the effect of steady state g-jitter induced oscillation and on the solute redistribution in the liquid that bears direct relevance to the Bridgman-Stockbarger single crystal growth processes. A selection of computed results is presented and the results indicate that an applied magnetic field can effectively damp the velocity caused by g-jitter and help to reduce the time variation of solute redistribution.

Practical security analysis of continuous-variable quantum key distribution with jitter in clock synchronization

NASA Astrophysics Data System (ADS)

Xie, Cailang; Guo, Ying; Liao, Qin; Zhao, Wei; Huang, Duan; Zhang, Ling; Zeng, Guihua

2018-03-01

How to narrow the gap of security between theory and practice has been a notoriously urgent problem in quantum cryptography. Here, we analyze and provide experimental evidence of the clock jitter effect on the practical continuous-variable quantum key distribution (CV-QKD) system. The clock jitter is a random noise which exists permanently in the clock synchronization in the practical CV-QKD system, it may compromise the system security because of its impact on data sampling and parameters estimation. In particular, the practical security of CV-QKD with different clock jitter against collective attack is analyzed theoretically based on different repetition frequencies, the numerical simulations indicate that the clock jitter has more impact on a high-speed scenario. Furthermore, a simplified experiment is designed to investigate the influence of the clock jitter.

Coupled Optoelectronic Oscillators:. Application to Low-Jitter Pulse Generation

NASA Astrophysics Data System (ADS)

Yu, N.; Tu, M.; Maleki, L.

2002-04-01

Actively mode-locked Erbium-doped fiber lasers (EDFL) have been studied for generating stable ultra-fast pulses (< 2 ps) at high repetition rates (> 5 GHz) [1,2]. These devices can be compact and environmentally stable, quite suitable for fiber-based high-data-rate communications and optical ultra-fast analog-to-digital conversions (ADC) [3]. The pulse-to-pulse jitter of an EDFL-based pulse generator will be ultimately limited by the phase noise of the mode-locking microwave source (typically electronic frequency synthesizers). On the other hand, opto-electronic oscillators (OEO) using fibers have been demonstrated to generate ultra-low phase noise microwaves at 10 GHz and higher [4]. The overall phase noise of an OEO can be much lower than commercially available synthesizers at the offset-frequency range above 100 Hz. Clearly, ultra-low jitter pulses can be generated by taking advantage of the low phase noise of OEOs. In this paper, we report the progress in developing a new low-jitter pulse generator by combing the two technologies. In our approach, the optical oscillator (mode-locked EDFL) and the microwave oscillator (OEO) are coupled through a common Mach-Zehnder (MZ) modulator, thus named coupled opto-electronic oscillator (COEO) [5]. Based on the results of previous OEO study, we can expect a 10 GHz pulse train with jitters less than 10 fs.

Radial Velocities of Subgiant Stars and New Astrophysical Insights into RV Jitter

NASA Astrophysics Data System (ADS)

Luhn, Jacob; Bastien, Fabienne; Wright, Jason T.

2018-01-01

For nearly 20 years, the California Planet Search (CPS) has simultaneously monitored precise radial velocities and chromospheric activity levels of stars from Keck observatory to search for exoplanets. This sample provides a useful set of stars to better determine the dependence of RV jitter on flicker (which traces surface gravity) first shown in Bastien et al. (2014). We expand upon this initial work by examining a much larger sample of stars covering a much wider range of stellar parameters (effective temperature, surface gravity, and activity, among others). For more than 600 stars, there are enough RV measurements to distinguish this astrophysical jitter from accelerations due to orbital companions. To properly isolate RV jitter from these effects, we must first remove the RV signal due to these companions, including several previously unannounced giant planets around subgiant stars. We highlight some new results from our analysis of the CPS data. A more thorough understanding of the various sources of RV jitter and the underlying stellar phenomena that drive these intrinsic RV variations will enable more precise jitter estimates for RV follow-up targets such as those from K2 or the upcoming TESS mission.

Sub-femtosecond timing jitter, all-fiber, CNT-mode-locked Er-laser at telecom wavelength.

PubMed

Kim, Chur; Bae, Sangho; Kieu, Khanh; Kim, Jungwon

2013-11-04

We demonstrate a 490-attosecond timing jitter (integration bandwidth: 10 kHz - 39.4 MHz) optical pulse train from a 78.7-MHz repetition rate, all-fiber soliton Er laser mode-locked by a fiber tapered carbon nanotube saturable absorber (ft-CNT-SA). To achieve this jitter performance, we searched for a net cavity dispersion condition where the Gordon-Haus jitter is minimized while maintaining stable soliton mode-locking. Our result shows that optical pulse trains with well below a femtosecond timing jitter can be generated from a self-starting and robust all-fiber laser operating at telecom wavelength.

A low jitter PLL clock used for phase change memory

NASA Astrophysics Data System (ADS)

Xiao, Hong; Houpeng, Chen; Zhitang, Song; Daolin, Cai; Xi, Li

2013-02-01

A fully integrated low-jitter, precise frequency CMOS phase-locked loop (PLL) clock for the phase change memory (PCM) drive circuit is presented. The design consists of a dynamic dual-reset phase frequency detector (PFD) with high frequency acquisition, a novel low jitter charge pump, a CMOS ring oscillator based voltage-controlled oscillator (VCO), a 2nd order passive loop filter, and a digital frequency divider. The design is fabricated in 0.35 μm CMOS technology and consumes 20 mW from a supply voltage of 5 V. In terms of the PCM's program operation requirement, the output frequency range is from 1 to 140 MHz. For the 140 MHz output frequency, the circuit features a cycle-to-cycle jitter of 28 ps RMS and 250 ps peak-to-peak.

Study of Magnetic Damping Effect on Convection and Solidification Under G-Jitter Conditions

NASA Technical Reports Server (NTRS)

Li, Ben Q.; deGroh, H. C.

2001-01-01

As shown in space flight experiments, g-jitter is a critical issue affecting solidification processing of materials in microgravity. This study aims to provide, through extensive numerical simulations and ground based experiments, an assessment of the use of magnetic fields in combination with microgravity to reduce the g-jitter induced convective flows in space processing systems. Analytical solutions and 2-D and 3-D numerical models for g-jitter driven flows in simple solidification systems with and without the presence of an applied magnetic field have been developed and extensive analyses were carried out. A physical model was also constructed and PIV measurements compared reasonably well with predictions from numerical models. Some key points may be summarized as follows: (1) the amplitude of the oscillating velocity decreases at a rate inversely proportional to the g-jitter frequency and with an increase in the applied magnetic field; (2) the induced flow oscillates at approximately the same frequency as the affecting g-jitter, but out of a phase angle; (3) the phase angle is a complicated function of geometry, applied magnetic field, temperature gradient and frequency; (4) g-jitter driven flows exhibit a complex fluid flow pattern evolving in time; (5) the damping effect is more effective for low frequency flows; and (6) the applied magnetic field helps to reduce the variation of solutal distribution along the solid-liquid interface. Work in progress includes developing numerical models for solidification phenomena with the presence of both g-jitter and magnetic fields and developing a ground-based physical model to verify numerical predictions.

Quantitating Changes in Jitter and Spike Number Using Concentric Needle Electrodes in Amyotrophic Lateral Sclerosis Patients

PubMed Central

Liu, Ming-Sheng; Niu, Jing-Wen; Li, Yi; Guan, Yu-Zhou; Cui, Li-Ying

2016-01-01

Background: Single-fiber electromyography (SFEMG) has been suggested as a quantitative method for supporting chronic partial denervation in amyotrophic lateral sclerosis (ALS) by the revised EI Escorial criteria. Although concentric needle (CN) electrodes have been used to assess jitter in myasthenia gravis patients and healthy controls, there are few reports using CN electrodes to assess motor unit instability and denervation in neurogenic diseases. The aim of this study was to determine whether quantitative changes in jitter and spike number using CN electrodes could be used for ALS studies. Methods: Twenty-seven healthy controls and 23 ALS patients were studied using both CN and single-fiber needle (SFN) electrodes on the extensor digitorum communis muscle with an SFEMG program. The SFN-jitter and SFN-fiber density data were measured using SFN electrodes. The CN-jitter and spike number were measured using CN electrodes. Results: The mean CN-jitter was significantly increased in ALS patients (47.3 ± 17.0 μs) than in healthy controls (27.4 ± 3.3 μs) (P < 0.001). Besides, the mean spike number was significantly increased in ALS patients (2.5 ± 0.5) than in healthy controls (1.7 ± 0.3) (P < 0.001). The sensitivity and specificity in the diagnosis of ALS were 82.6% and 92.6% for CN-jitter (cut-off value: 32 μs), and 91.3% and 96.3% for the spike number (cut-off value: 2.0), respectively. There was no significant difference between the SFN-jitter and CN-jitter in ALS patients; meanwhile, there was no significant difference between the SFN-jitter and CN-jitter in healthy controls. Conclusion: CN-jitter and spike number could be used to quantitatively evaluate changes due to denervation-reinnervation in ALS. PMID:27098787

Explaining the morphology of supernova remnant (SNR) 1987A with the jittering jets explosion mechanism

NASA Astrophysics Data System (ADS)

Bear, Ealeal; Soker, Noam

2018-07-01

We find that the remnant of supernova (SN) 1987A shares some morphological features with four supernova remnants (SNRs) that have signatures of shaping by jets, and from that we strengthen the claim that jets played a crucial role in the explosion of SN 1987A. Some of the morphological features appear also in planetary nebulae (PNe) where jets are observed. The clumpy ejecta brings us to support the claim that the jittering jets explosion mechanism can account for the structure of the remnant of SN 1987A, i.e. SNR 1987A. We conduct a preliminary attempt to quantify the fluctuations in the angular momentum of the mass that is accreted on to the newly born neutron star via an accretion disc or belt. The accretion disc/belt launches jets that explode core collapse supernovae (CCSNe). The relaxation time of the accretion disc/belt is comparable to the duration of a typicalfigu jet-launching episode in the jittering jets explosion mechanism, and hence the disc/belt has no time to relax. We suggest that this might explain the two unequal opposite jets that later lead to the unequal sides of the elongated structures in some SNRs of CCSNe. We reiterate our earlier call for a paradigm shift from a neutrino-driven explosion to a jet-driven explosion of CCSNe.

Explaining the morphology of supernova remnant (SNR) 1987A with the jittering jets explosion mechanism

NASA Astrophysics Data System (ADS)

Bear, Ealeal; Soker, Noam

2018-04-01

We find that the remnant of supernova (SN) 1987A shares some morphological features with four supernova remnants (SNRs) that have signatures of shaping by jets, and from that we strengthen the claim that jets played a crucial role in the explosion of SN 1987A. Some of the morphological features appear also in planetary nebulae (PNe) where jets are observed. The clumpy ejecta bring us to support the claim that the jittering jets explosion mechanism can account for the structure of the remnant of SN 1987A, i.e., SNR 1987A. We conduct a preliminary attempt to quantify the fluctuations in the angular momentum of the mass that is accreted on to the newly born neutron star via an accretion disk or belt. The accretion disk/belt launches the jets that explode core collapse supernovae (CCSNe). The relaxation time of the accretion disk/belt is comparable to the duration of a typical jet-launching episode in the jittering jets explosion mechanism, and hence the disk/belt has no time to relax. We suggest that this might explain two unequal opposite jets that later lead to unequal sides of the elongated structures in some SNRs of CCSNe. We reiterate our earlier call for a paradigm shift from neutrino-driven explosion to a jet-driven explosion of CCSNe.

Jitter and phase noise of ADPLL due to PSN with deterministic frequency

NASA Astrophysics Data System (ADS)

Deng, Xiaoying; Yang, Jun; Wu, Jianhui

2011-09-01

In this article, jitter and phase noise of all-digital phase-locked loop due to power supply noise (PSN) with deterministic frequency are analysed. It leads to the conclusion that jitter and phase noise heavily depend on the noise frequency. Compared with jitter, phase noise is much less affected by the deterministic PSN. Our method is utilised to study a CMOS ADPLL designed and simulated in SMIC 0.13 µm standard CMOS process. A comparison between the results obtained by our method and those obtained by simulation and measurement proves the accuracy of the predicted model. When the digital controlled oscillator was corrupted by PSN with 100 mVpk-pk, the measured jitters were 33.9 ps at the rate of fG = 192 MHz and 148.5 ps at the rate of fG = 40 MHz. However, the measured phase noise was exactly the same except for two impulses appearing at 192 and 40 MHz, respectively.

Real-time operating system timing jitter and its impact on motor control

NASA Astrophysics Data System (ADS)

Proctor, Frederick M.; Shackleford, William P.

2001-12-01

General-purpose microprocessors are increasingly being used for control applications due to their widespread availability and software support for non-control functions like networking and operator interfaces. Two classes of real-time operating systems (RTOS) exist for these systems. The traditional RTOS serves as the sole operating system, and provides all OS services. Examples include ETS, LynxOS, QNX, Windows CE and VxWorks. RTOS extensions add real-time scheduling capabilities to non-real-time OSes, and provide minimal services needed for the time-critical portions of an application. Examples include RTAI and RTL for Linux, and HyperKernel, OnTime and RTX for Windows NT. Timing jitter is an issue in these systems, due to hardware effects such as bus locking, caches and pipelines, and software effects from mutual exclusion resource locks, non-preemtible critical sections, disabled interrupts, and multiple code paths in the scheduler. Jitter is typically on the order of a microsecond to a few tens of microseconds for hard real-time operating systems, and ranges from milliseconds to seconds in the worst case for soft real-time operating systems. The question of its significance on the performance of a controller arises. Naturally, the smaller the scheduling period required for a control task, the more significant is the impact of timing jitter. Aside from this intuitive relationship is the greater significance of timing on open-loop control, such as for stepper motors, than for closed-loop control, such as for servo motors. Techniques for measuring timing jitter are discussed, and comparisons between various platforms are presented. Techniques to reduce jitter or mitigate its effects are presented. The impact of jitter on stepper motor control is analyzed.

Measurement Techniques for Transmit Source Clock Jitter for Weak Serial RF Links

NASA Technical Reports Server (NTRS)

Lansdowne, Chatwin A.; Schlesinger, Adam M.

2010-01-01

Techniques for filtering clock jitter measurements are developed, in the context of controlling data modulation jitter on an RF carrier to accommodate low signal-to-noise ratio thresholds of high-performance error correction codes. Measurement artifacts from sampling are considered, and a tutorial on interpretation of direct readings is included.

Passive isolator design for jitter reduction in the Terrestrial Planet Finder Coronagraph

NASA Technical Reports Server (NTRS)

Blaurock, Carl; Liu, Kuo-Chia; Dewell, Larry; Alexander, James

2005-01-01

Terrestrial Planet Finder (TPF) is a mission to locate and study extrasolar Earth-like planets. The TPF Coronagraph (TPF-C), planned for launch in the latter half of the next decade, will use a coronagraphic mask and other optics to suppress the light of the nearby star in order to collect visible light from such planets. The required contrast ratio of 5e-11 can only be achieved by maintaining pointing accuracy to 4 milli-arcseconds, and limiting optics jitter to below 5 nm. Numerous mechanical disturbances act to induce jitter. This paper concentrates on passive isolation techniques to minimize the optical degradation introduced by disturbance sources. A passive isolation system, using compliant mounts placed at an energy bottleneck to reduce energy transmission above a certain frequency, is a low risk, flight proven design approach. However, the attenuation is limited, compared to an active system, so the feasibility of the design must be demonstrated by analysis. The paper presents the jitter analysis for the baseline TPF design, using a passive isolation system. The analysis model representing the dynamics of the spacecraft and telescope is described, with emphasis on passive isolator modeling. Pointing and deformation metrics, consistent with the TPF-C error budget, are derived. Jitter prediction methodology and results are presented. Then an analysis of the critical design parameters that drive the TPF-C jitter response is performed.

The Role of Perceived Speed in Vection: Does Perceived Speed Modulate the Jitter and Oscillation Advantages?

PubMed Central

Apthorp, Deborah; Palmisano, Stephen

2014-01-01

Illusory self-motion (‘vection’) in depth is strongly enhanced when horizontal/vertical simulated viewpoint oscillation is added to optic flow inducing displays; a similar effect is found for simulated viewpoint jitter. The underlying cause of these oscillation and jitter advantages for vection is still unknown. Here we investigate the possibility that perceived speed of motion in depth (MID) plays a role. First, in a 2AFC procedure, we obtained MID speed PSEs for briefly presented (vertically oscillating and smooth) radial flow displays. Then we examined the strength, duration and onset latency of vection induced by oscillating and smooth radial flow displays matched either for simulated or perceived MID speed. The oscillation advantage was eliminated when displays were matched for perceived MID speed. However, when we tested the jitter advantage in the same manner, jittering displays were found to produce greater vection in depth than speed-matched controls. In summary, jitter and oscillation advantages were the same across experiments, but slower MID speed was required to match jittering than oscillating stimuli. Thus, to the extent that vection is driven by perceived speed of MID, this effect is greater for oscillating than for jittering stimuli, which suggests that the two effects may arise from separate mechanisms. PMID:24651861

An Experimental Study of a Low-Jitter Pulsed Electromagnetic Plasma Accelerator

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Lee, Michael; Eskridge, Richard; Smith, James; Martin, Adam; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

An experimental plasma accelerator for a variety of applications under development at the NASA Marshall Space Flight Center is described. The accelerator is a pulsed plasma thruster and has been tested experimentally and plasma jet velocities of approximately 50 kilometers per second have been obtained. The plasma jet structure has been photographed with 10 ns exposure times to reveal a stable and repeatable plasma structure. Data for velocity profile information has been obtained using light pipes embedded in the gun walls to record the plasma transit at various barrel locations. Preliminary spatially resolved spectral data and magnetic field probe data are also presented. A high speed triggering system has been developed and tested as a means of reducing the gun "jitter". This jitter has been characterized and future work for second generation "ultra-low jitter" gun development is identified.

Photonic ADC: overcoming the bottleneck of electronic jitter.

PubMed

Khilo, Anatol; Spector, Steven J; Grein, Matthew E; Nejadmalayeri, Amir H; Holzwarth, Charles W; Sander, Michelle Y; Dahlem, Marcus S; Peng, Michael Y; Geis, Michael W; DiLello, Nicole A; Yoon, Jung U; Motamedi, Ali; Orcutt, Jason S; Wang, Jade P; Sorace-Agaskar, Cheryl M; Popović, Miloš A; Sun, Jie; Zhou, Gui-Rong; Byun, Hyunil; Chen, Jian; Hoyt, Judy L; Smith, Henry I; Ram, Rajeev J; Perrott, Michael; Lyszczarz, Theodore M; Ippen, Erich P; Kärtner, Franz X

2012-02-13

Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical imaging, and communication systems. Aperture jitter has been a major bottleneck on the way towards higher speeds and better accuracy. Photonic ADCs, which perform sampling using ultra-stable optical pulse trains generated by mode-locked lasers, have been investigated for many years as a promising approach to overcome the jitter problem and bring ADC performance to new levels. This work demonstrates that the photonic approach can deliver on its promise by digitizing a 41 GHz signal with 7.0 effective bits using a photonic ADC built from discrete components. This accuracy corresponds to a timing jitter of 15 fs - a 4-5 times improvement over the performance of the best electronic ADCs which exist today. On the way towards an integrated photonic ADC, a silicon photonic chip with core photonic components was fabricated and used to digitize a 10 GHz signal with 3.5 effective bits. In these experiments, two wavelength channels were implemented, providing the overall sampling rate of 2.1 GSa/s. To show that photonic ADCs with larger channel counts are possible, a dual 20-channel silicon filter bank has been demonstrated.

Analysis of Optimal Jitter Buffer Size for VoIP QoS under WiMAX Power-Saving Mode

NASA Astrophysics Data System (ADS)

Kim, Hyungsuk; Kim, Taehyoun

VoIP service is expected as one of the key applications of Mobile WiMAX, but the speech quality of VoIP service often suffers deterioration due to the fluctuating transmission delay called jitter. This is commonly ameliorated by a de-jitter buffer, and we aim to find the optimal size of de-jitter buffer to achieve speech quality comparable to PSTN. We developed a new model of the packet drops at the de-jitter buffer and the end-to-end packet delay which takes account of the additional delay introduced by the WiMAX power-saving mode. Using our model, we analyzed the optimal size of the de-jitter buffer for various network parameters, and showed that the results obtained by analysis accord with simulation results.

Light gas gun with reduced timing jitter

DOEpatents

Laabs, Gary W.; Funk, David J.; Asay, Blaine W.

1998-01-01

Gas gun with reduced timing jitter. A gas gun having a prepressurized projectile held in place with a glass rod in compression is described. The glass rod is destroyed with an explosive at a precise time which allows a restraining pin to be moved and free the projectile.

Broadly tunable, low timing jitter, high repetition rate optoelectronic comb generator

PubMed Central

Metcalf, A. J.; Quinlan, F.; Fortier, T. M.; Diddams, S. A.; Weiner, A. M.

2016-01-01

We investigate the low timing jitter properties of a tunable single-pass optoelectronic frequency comb generator. The scheme is flexible in that both the repetition rate and center frequency can be continuously tuned. When operated with 10 GHz comb spacing, the integrated residual pulse-to-pulse timing jitter is 11.35 fs (1 Hz to 10 MHz) with no feedback stabilization. The corresponding phase noise at 1 Hz offset from the photodetected 10 GHz carrier is −100 dBc/Hz. PMID:26865734

Effects of G-Jitter on Interfacial Dynamics of Two Miscible Liquids: Application of MIM

NASA Technical Reports Server (NTRS)

Duval, Walter M. B.; Tryggvason, Bjarni V.

2000-01-01

We designed an experiment to examine the effects of g-jitter on mixing of two miscible liquids using the Microgravity Vibration Isolation Mount (MIM). The global bifurcation of the interface was observed with the MIM operating alternatively to either transmit the g-jitter, isolate from the g-jitter or to provide controlled vibration levels with well defined amplitude and frequency content. With the MIM in isolation mode, the interface remains stationary indicating buoyancy induced convection is negligibly small such that mixing occurs via intrinsic mass diffusion without the masking effect of vibration driven convection. Analytical and computational results are in agreement with the experimental findings. Operation of the MIM in forced mode with conditions typical of g-jitter shows that vibration induced convective flows can excite instability mechanisms such as Kelvin-Helmholtz to generate large amplitude quasi-stationary waves oriented vertically for various cases with Stokes-Reynolds number in the range of 0.003 to 0.5. The two and four mode quasi-stationary waves are also predicted with a mathematical model. Though unplanned, the effect of a primary thruster filing was captured and shown to cause a catastrophic bifurcation, enhancing local mass transport. In light of the findings, experiments planned for the International Space Station should consider the potential effects of g-jitter.

Light gas gun with reduced timing jitter

DOEpatents

Laabs, G.W.; Funk, D.J.; Asay, B.W.

1998-06-09

Gas gun with reduced timing jitter is disclosed. A gas gun having a prepressurized projectile held in place with a glass rod in compression is described. The glass rod is destroyed with an explosive at a precise time which allows a restraining pin to be moved and free the projectile. 4 figs.

Influence of P300 latency jitter on event related potential-based brain-computer interface performance

NASA Astrophysics Data System (ADS)

Aricò, P.; Aloise, F.; Schettini, F.; Salinari, S.; Mattia, D.; Cincotti, F.

2014-06-01

Objective. Several ERP-based brain-computer interfaces (BCIs) that can be controlled even without eye movements (covert attention) have been recently proposed. However, when compared to similar systems based on overt attention, they displayed significantly lower accuracy. In the current interpretation, this is ascribed to the absence of the contribution of short-latency visual evoked potentials (VEPs) in the tasks performed in the covert attention modality. This study aims to investigate if this decrement (i) is fully explained by the lack of VEP contribution to the classification accuracy; (ii) correlates with lower temporal stability of the single-trial P300 potentials elicited in the covert attention modality. Approach. We evaluated the latency jitter of P300 evoked potentials in three BCI interfaces exploiting either overt or covert attention modalities in 20 healthy subjects. The effect of attention modality on the P300 jitter, and the relative contribution of VEPs and P300 jitter to the classification accuracy have been analyzed. Main results. The P300 jitter is higher when the BCI is controlled in covert attention. Classification accuracy negatively correlates with jitter. Even disregarding short-latency VEPs, overt-attention BCI yields better accuracy than covert. When the latency jitter is compensated offline, the difference between accuracies is not significant. Significance. The lower temporal stability of the P300 evoked potential generated during the tasks performed in covert attention modality should be regarded as the main contributing explanation of lower accuracy of covert-attention ERP-based BCIs.

An examination of anticipated g-jitter on Space Station and its effects on materials processes

NASA Technical Reports Server (NTRS)

Nelson, Emily

1992-01-01

Information on anticipated g-jitter on Space Station Freedom and the effect of the jitter on materials processes is given in viewgraph form. It was concluded that g-jitter will dominate the acceleration environment; that it is a 3D multifrequency phenomenon; and that it varies dramatically in orientation. Information is given on calculated or measured sources of residual acceleration, aerodynamic drag, Shuttle acceleration measurements, the Space Station environment, tolerable g-levels as a function of frequency, directional solidification, vapor crystal growth, protein crystal growth, float zones, and liquid bridges.

Sub-100 attosecond timing jitter from low-noise passively mode-locked solid-state laser at telecom wavelength.

PubMed

Portuondo-Campa, E; Paschotta, R; Lecomte, S

2013-08-01

We report on the ultralow timing jitter of the 100 MHz pulse trains generated by two identical passively mode-locked diode-pumped solid-state lasers (DPSSLs) emitting at 1556 nm. Ultralow timing jitter of 83 as (integrated from 10 kHz to 50 MHz) for one laser has been measured with a balanced optical cross-correlator as timing discriminator. Extremely low intensity noise has been measured as well. Several measurement techniques have been used and show similar jitter results. Different possible noise sources have been theoretically investigated and compared to the measured jitter power spectral density. It is found that although the measured integrated jitter is quite low, it is still significantly above the quantum limit in the considered frequency span. Therefore, there is a substantial potential for technical improvements that could make passively mode-locked DPSSL outperform fiber lasers as source of microwaves with low phase noise.

Radiation from Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Mizuno, Y.; Hardee, P.; Sol, H.; Medvedev, M.; Zhang, B.; Nordlund, A.; Frederiksen, J. T.; Fishman, G. J.; Preece, R.

2008-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations of relativistic electron-ion (electron-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In the presence of relativistic jets, instabilities such as the Buneman instability, other two-streaming instability, and the Weibel (filamentation) instability create collisionless shocks, which are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The 'jitter' radiation from deflected electrons in small-scale magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation, a case of diffusive synchrotron radiation, may be important to understand the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

A Paradigm shift to an Old Scheme for Outgoing Longwave Radiation

NASA Astrophysics Data System (ADS)

McDonald, Alastair B.

2016-04-01

There are many cases where the climate models do not agree with the empirical data. For instance, the data from radiosondes (and MSUs) do not show the amount of warming in the upper troposphere that is predicted by the models (Thorne et al. 2011). The current scheme for outgoing longwave radiation can be traced back to the great 19th Century French mathematician J-B Joseph Fourier. His anachronistic idea was that the radiation balance at the top of the atmosphere (TOA) is maintained by the conduction of heat from the surface (Fourier 1824). It was based on comparing the atmosphere to the 18th Century Swiss scientist H-B de Saussure's hotbox which he had invented to show that solar radiation is only slightly absorbed by the atmosphere. Saussure also showed that thermal radiation existed and argued that the warmth of the air near the surface of the Earth is due to absorption of that infra red radiation (Saussure 1786). Hence a paradigm shift to Saussure's scheme, where the thermal radiation is absorbed at the base of the atmosphere, rather than throughout the atmosphere as in Fourier's scheme, may solve many climate models problems. In this new paradigm the boundary layer continually exchanges radiation with the surface. Thus only at two instants during the day is there no net gain or loss of heat by the boundary layer from the surface, and so that layer is not in LTE. Moreover, since the absorption of outgoing longwave radiation is saturated within the boundary layer, it has little influence on the TOA balance. That balance is mostly maintained by changes in albedo, e.g. clouds and ice sheets. Use of this paradigm can explain why the excess warming in south western Europe was caused by water vapour close to the surface (Philipona et al. 2005), and may also explain why there are difficulties in closing the surface radiation balance (Wild et al. 2013) and in modelling abrupt climate change (White et al. 2013). References: Fourier, Joseph. 1824. 'Remarques G�

Integrated Modeling Activities for the James Webb Space Telescope: Optical Jitter Analysis

NASA Technical Reports Server (NTRS)

Hyde, T. Tupper; Ha, Kong Q.; Johnston, John D.; Howard, Joseph M.; Mosier, Gary E.

2004-01-01

This is a continuation of a series of papers on the integrated modeling activities for the James Webb Space Telescope(JWST). Starting with the linear optical model discussed in part one, and using the optical sensitivities developed in part two, we now assess the optical image motion and wavefront errors from the structural dynamics. This is often referred to as "jitter: analysis. The optical model is combined with the structural model and the control models to create a linear structural/optical/control model. The largest jitter is due to spacecraft reaction wheel assembly disturbances which are harmonic in nature and will excite spacecraft and telescope structural. The structural/optic response causes image quality degradation due to image motion (centroid error) as well as dynamic wavefront error. Jitter analysis results are used to predict imaging performance, improve the structural design, and evaluate the operational impact of the disturbance sources.

Micro-jitter attenuation of spaceborne cooler by using a blade-type hyperelastic shape memory alloy passive isolator

NASA Astrophysics Data System (ADS)

Kwon, Seong-Cheol; Jeon, Young-Hyeon; Oh, Hyun-Ung

2017-10-01

In this study, the primary design objective is to develop a passive isolator that can guarantee structural safety of the cooler assembly in a launch vibration environment without a launch locking mechanism, while effectively isolating the cooler-induced micro-jitter during the on-orbit operation of the cooler. To achieve the design objective, we focused on the utilization of characteristics of the hyperelastic shape memory effects. The major advantage of the isolator is that the micro-jitter isolation performance is much less sensitive to the aligned position of the isolator in comparison with the conventional isolator. Moreover, implementation of an additional 0g compensation device during a satellite level on-ground test, such as a jitter measurement test, is not required. In this study, the basic characteristics of the isolator were measured using the torque test and free vibration test. The micro-jitter attenuation capability and position sensitivity of the proposed isolator design were validated by the micro-jitter measurement test.

Sub-fs electron bunch generation with sub-10-fs bunch arrival-time jitter via bunch slicing in a magnetic chicane

NASA Astrophysics Data System (ADS)

Zhu, J.; Assmann, R. W.; Dohlus, M.; Dorda, U.; Marchetti, B.

2016-05-01

The generation of ultrashort electron bunches with ultrasmall bunch arrival-time jitter is of vital importance for laser-plasma wakefield acceleration with external injection. We study the production of 100-MeV electron bunches with bunch durations of subfemtosecond (fs) and bunch arrival-time jitters of less than 10 fs, in an S-band photoinjector by using a weak magnetic chicane with a slit collimator. The beam dynamics inside the chicane is simulated by using two codes with different self-force models. The first code separates the self-force into a three-dimensional (3D) quasistatic space-charge model and a one-dimensional coherent synchrotron radiation (CSR) model, while the other one starts from the first principle with a so-called 3D sub-bunch method. The simulations indicate that the CSR effect dominates the horizontal emittance growth and the 1D CSR model underestimates the final bunch duration and emittance because of the very large transverse-to-longitudinal aspect ratio of the sub-fs bunch. Particularly, the CSR effect is also strongly affected by the vertical bunch size. Due to the coupling between the horizontal and longitudinal phase spaces, the bunch duration at the entrance of the last dipole magnet of the chicane is still significantly longer than that at the exit of the chicane, which considerably mitigates the impact of space charge and CSR effects on the beam quality. Exploiting this effect, a bunch charge of up to 4.8 pC in a sub-fs bunch could be simulated. In addition, we analytically and numerically investigate the impact of different jitter sources on the bunch arrival-time jitter downstream of the chicane, and define the tolerance budgets assuming realistic values of the stability of the linac for different bunch charges and compression schemes.

Short-period terrestrial planets and radial velocity stellar jitter.

NASA Astrophysics Data System (ADS)

Dumusque, Xavier

2015-01-01

Stellar jitter is the main limitation to ultra-precise radial velocity (RV) measurements. It currently precludes our ability to detect a planet like the Earth. Short-period terrestrial planets present first the advantage of inducing a stronger RV signal. In addition, the signal produced by these planets have a period completely different than stellar activity. This allows us, when the observational strategy is adequate, to decorrelate the planetary signal from the jitter induced by the star using filtering techniques. I will show the examples of Kepler-78b and Corot-7b, where the amplitude of the planetary signal can be detected, despite the stellar activity jitter that is 5 and 3 times larger, respectively. The cases of Alpha Cen Bb will also be reviewed, with a new reduction of the published data that increases the significance of the planetary signal.This project is funded by ETAEARTH, a transnational collaboration between European countries and the US (the Swiss Space Office, the Harvard Origin of Life Initiative, the Scottish Universities Physics Alliance, the University of Geneva, the Smithsonian Astrophysical Observatory, the Italian National Astrophysical Institute, the University of St. Andrews, Queens University Belfast, and the University of Edinburgh) setup to optimize the synergy between space-and ground-based data whose scientific potential for the characterization of extrasolar planets can only be fully exploited when analyzed together.

PLL jitter reduction by utilizing a ferroelectric capacitor as a VCO timing element.

PubMed

Pauls, Greg; Kalkur, Thottam S

2007-06-01

Ferroelectric capacitors have steadily been integrated into semiconductor processes due to their potential as storage elements within memory devices. Polarization reversal within ferroelectric capacitors creates a high nonlinear dielectric constant along with a hysteresis profile. Due to these attributes, a phase-locked loop (PLL), when based on a ferroelectric capacitor, has the advantage of reduced cycle-to-cycle jitter. PLLs based on ferroelectric capacitors represent a new research area for reduction of oscillator jitter.

Modelling the RV jitter of early-M dwarfs using tomographic imaging

NASA Astrophysics Data System (ADS)

Hébrard, É. M.; Donati, J.-F.; Delfosse, X.; Morin, J.; Moutou, C.; Boisse, I.

2016-09-01

In this paper, we show how tomographic imaging (Zeeman-Doppler imaging, ZDI) can be used to characterize stellar activity and magnetic field topologies, ultimately allowing us to filter out the radial velocity (RV) activity jitter of M dwarf moderate rotators. This work is based on spectropolarimetric observations of a sample of five weakly active early-M dwarfs (GJ 205, GJ 358, GJ 410, GJ 479, GJ 846) with HARPS-Pol and NARVAL. These stars have v sin I and RV jitters in the range 1-2 km s-1 and 2.7-10.0 m s-1 rms, respectively. Using a modified version of ZDI applied to sets of phase-resolved least-squares deconvolved profiles of unpolarized spectral lines, we are able to characterize the distribution of active regions at the stellar surfaces. We find that dark spots cover less than 2 per cent of the total surface of the stars of our sample. Our technique is efficient at modelling the rotationally modulated component of the activity jitter, and succeeds at decreasing the amplitude of this component by typical factors of 2-3 and up to 6 in optimal cases. From the rotationally modulated time series of circularly polarized spectra and with ZDI, we also reconstruct the large-scale magnetic field topology. These fields suggest that bistability of dynamo processes observed in active M dwarfs may also be at work for moderately active M dwarfs. Comparing spot distributions with field topologies suggest that dark spots causing activity jitter concentrate at the magnetic pole and/or equator, to be confirmed with future data on a larger sample.

A voltage-division-type low-jitter self-triggered repetition-rate switch.

PubMed

Su, Jian-Cang; Zeng, Bo; Gao, Peng-Cheng; Li, Rui; Wu, Xiao-Long; Zhao, Liang

2016-10-01

A voltage-division-type (V/N) low-jitter self-triggered multi-stage switch is put forward. It comprises of a triggered corona gap, several quasi-uniform-field gaps, and an inversion inductor. When the corona gap is in the stage of self-breakdown, the multi-stage gaps are triggered and the switch is closed via an over-voltage. This type of V/N switch has the advantage of compact structure since the auxiliary components like the gas-blowing system and the triggered system are eliminated from the whole system. It also has advantages such as low breakdown jitter and high energy efficiency. The dependence of the self-triggered voltage on the over-voltage factor and the switch operating voltage is deduced. A switch of this type is designed and fabricated and experiments to research its characteristics are conducted. The results show that this switch can operate on a voltage of 1 MV at 50 Hz and can generate 1000 successive pulses with a jitter as low as 3% and an energy efficiency as high as 90%. This V/N switch can work under a high repetition rate with a long lifetime.

Ultralow-jitter and -amplitude-noise semiconductor-based actively mode-locked laser.

PubMed

Quinlan, Franklyn; Gee, Sangyoun; Ozharar, Sarper; Delfyett, Peter J

2006-10-01

We report a semiconductor-based, low-noise, 10.24 GHz actively mode-locked laser with 4.65 fs of relative timing jitter and a 0.0365% amplitude fluctuation (1 Hz to 100 MHz) of the optical pulse train. The keys to obtaining this result were the laser's high optical power and the low phase noise of the rf source used to mode lock the laser. The low phase noise of the rf source not only improves the absolute and relative timing jitter of the laser, but also prevents coupling of the rf source phase noise to the pulse amplitude fluctuations by the mode-locked laser.

Influence of group-delay ripple on timing jitter induced by SPM and IXPM in systems with dispersion compensated by CFBG

NASA Astrophysics Data System (ADS)

Qin, Xi; Cao, Jihong; Chen, Yong; Zhang, Feng; Jian, Shuisheng

2007-08-01

An analytical expression was proposed to analyze the influence of group-delay ripple (GDR) on timing jitter induced by self-phase modulation (SPM) and intra-channel cross-phase modulation (IXPM) in pseudo-linear transmission systems when dispersion was compensated by chirped fiber Bragg grating (CFBG). Effects of ripple amplitude, period, and phase on timing jitter were discussed by theoretical and numerical analysis in detail. The results show that the influence of GDR on timing jitter changes linearly with the amplitude of GDR and whether it decreases or increases the timing jitter relies on the ripple period and ripple phase. Timing jitter induced by SPM and IXPM could be suppressed totally by adjusting the relative phase between the center frequency of the pulse and the ripples.

A novel low-jitter plasma-jet triggered gas switch operated at a low working coefficient.

PubMed

Tie, Weihao; Liu, Shanhong; Liu, Xuandong; Zhang, Qiaogen; Pang, Lei; Liu, Longchen

2014-02-01

In this paper, we described the fabrication and testing of a novel plasma-jet triggered gas switch (PJTGS) operated at extremely low working coefficients with excellent triggered jitters. While the structure of the PJTGS is similar to that of a traditional three-electrode field-distortion gas switch, to improve its triggered performance we used a conical micro-plasma-gun with a needle-to-plate spark gap embedded in the trigger electrode. Applying a nanosecond pulse to the trigger electrode caused a spark discharge in the micro-plasma-gun. The electric field drove the discharge plasma to spray into the spark gap of the gas switch, causing fast breakdown. We tested the PJTGS with charging voltages of ±25 kV and a trigger voltage of +80 kV (5 ns rise time and 80 ns full width at half maximum) in two working modes. The PJTGS operated in Mode II had a lower triggered jitter and could be operated over a wider range of working coefficients than in Mode I under the same conditions. At working coefficients higher than 70%, we obtained sub-ns triggered jitters (<0.89 ns) from the PJTGS, at working coefficients lower than 50%, we obtained triggered jitters of 1.6-3.5 ns without no-fires or pre-fires. Even at a working coefficient of 27.4%, the PJTGS could still be triggered reliably with a delay time of 96.1 ns and a triggered jitter of 3.5 ns, respectively.

A novel trigger for pseudospark switch with high repetition rate, low jitter, and compact structure

NASA Astrophysics Data System (ADS)

Yan, Jiaqi; Shen, Saikang; Wang, Yanan; Zhang, Siyu; Cheng, Le; Ding, Weidong

2018-06-01

This paper presents the design and development of a trigger with a high repetition rate, low jitter, and compact structure for the pseudospark switch (PSS), which includes an improved Marx generator based on avalanche transistors and a corona-plasma trigger unit. The generator adopted a novel 3 × 12-stage Marx circuit based on avalanche transistors in which the failure rate of transistors in the first and second stages was significantly reduced by connecting the parallel capacitors compared to the previous similar generator. The reason for the improved performance was also discussed. The main parameters of output pulses were an amplitude of -7 kV, rise time of 6 ns, jitter of 0.2 ns, and repetition rate of 2 kHz. The corona-plasma trigger unit adopted BaTiO3 ceramics with high ɛr as the dielectric and was arranged in the hollow cathode of the PSS. The experiments of triggering a PSS prototype were conducted. The influence of anode voltage and pressure on the trigger delay and jitter was studied, and the minimum trigger jitter achieved <1 ns. This trigger worked for 107 shots at the repetition rate of 2 kHz continuously without obvious performance degradation and any failure of the generator. The main advantage of this trigger is the simultaneous combination of the high repetition rate, low jitter, long lifetime, and great simplicity in a compact structure.

The development of high-voltage repetitive low-jitter corona stabilized triggered switch

NASA Astrophysics Data System (ADS)

Geng, Jiuyuan; Yang, Jianhua; Cheng, Xinbing; Yang, Xiao; Chen, Rong

2018-04-01

The high-power switch plays an important part in a pulse power system. With the trend of pulse power technology toward modularization, miniaturization, and accuracy control, higher requirements on electrical trigger and jitter of the switch have been put forward. A high-power low-jitter corona-stabilized triggered switch (CSTS) is designed in this paper. This kind of CSTS is based on corona stabilized mechanism, and it can be used as a main switch of an intense electron-beam accelerator (IEBA). Its main feature was the use of an annular trigger electrode instead of a traditional needle-like trigger electrode, taking main and side trigger rings to fix the discharging channels and using SF6/N2 gas mixture as its operation gas. In this paper, the strength of the local field enhancement was changed by a trigger electrode protrusion length Dp. The differences of self-breakdown voltage and its stability, delay time jitter, trigger requirements, and operation range of the switch were compared. Then the effect of different SF6/N2 mixture ratio on switch performance was explored. The experimental results show that when the SF6 is 15% with the pressure of 0.2 MPa, the hold-off voltage of the switch is 551 kV, the operating range is 46.4%-93.5% of the self-breakdown voltage, the jitter is 0.57 ns, and the minimum trigger voltage requirement is 55.8% of the peak. At present, the CSTS has been successfully applied to an IEBA for long time operation.

The development of high-voltage repetitive low-jitter corona stabilized triggered switch.

PubMed

Geng, Jiuyuan; Yang, Jianhua; Cheng, Xinbing; Yang, Xiao; Chen, Rong

2018-04-01

The high-power switch plays an important part in a pulse power system. With the trend of pulse power technology toward modularization, miniaturization, and accuracy control, higher requirements on electrical trigger and jitter of the switch have been put forward. A high-power low-jitter corona-stabilized triggered switch (CSTS) is designed in this paper. This kind of CSTS is based on corona stabilized mechanism, and it can be used as a main switch of an intense electron-beam accelerator (IEBA). Its main feature was the use of an annular trigger electrode instead of a traditional needle-like trigger electrode, taking main and side trigger rings to fix the discharging channels and using SF 6 /N 2 gas mixture as its operation gas. In this paper, the strength of the local field enhancement was changed by a trigger electrode protrusion length Dp. The differences of self-breakdown voltage and its stability, delay time jitter, trigger requirements, and operation range of the switch were compared. Then the effect of different SF 6 /N 2 mixture ratio on switch performance was explored. The experimental results show that when the SF 6 is 15% with the pressure of 0.2 MPa, the hold-off voltage of the switch is 551 kV, the operating range is 46.4%-93.5% of the self-breakdown voltage, the jitter is 0.57 ns, and the minimum trigger voltage requirement is 55.8% of the peak. At present, the CSTS has been successfully applied to an IEBA for long time operation.

Biodosimetry as a New Paradigm for Determination of Radiation Risks and Risk-Mitigation in Astronauts Exposed to Space Radiation

NASA Technical Reports Server (NTRS)

Richmond, Robert; Cruz, Angela; Bors, Karen

2004-01-01

Predicting risk of cancer in astronauts exposed to space radiation is challenging partly because uncertainties of absorption of dose and the processing of dose-related damage at the cellular level degrade the confidence of predicting the expression of cancer. Cellular biodosimeters that simultaneously report: 1) the quantity of absorbed dose after exposure to ionizing radiation, 2) the quality of radiation delivering that dose, and 3) the macromolecular profiles related to malignant transformation in cells absorbing that dose would therefore be useful. An approach to such a multiparametric biodosimeter will be reported, This is the demonstration of two dose-responsive field-effects of enhanced protein-expression. In one case, expression of keratin 18 (K18) in cultures of human mammary epithelial cells (HMEC) irradiated with cesium-137 gamma-rays is enhanced following exposure of log phase cells to relatively low doses of 30 to 90 cGy. K18 has been reported by a marker for tumor staging and for apoptosis. In the second case, expression of connexin 43 (Cx43) is increased in irradiated stationary phase cultures of HMEC, indicating enhanced formation of gap junctions. Gap junctions have been reported to be involved in bystander effects following irradiation. It is a biodosimeter for assessing radiogenic damage. It is suggested further that such biomolecular dosimetry may introduce a new paradigm for assessing cancer risk and risk-mitigation in individuals, a requirement for managing radiation health in astronauts during extended missions in space. This new paradigm is built upon the statistical power provided by the use of functional genomics and proteomics represented in combined gene- and protein-expression assays.

Multi-megavolt low jitter multistage switch

DOEpatents

Humphreys, D.R.; Penn, K.J. Jr.

1985-06-19

It is one object of the present invention to provide a multistage switch capable of holding off numerous megavolts, until triggered, from a particle beam accelerator of the type used for inertial confinement fusion. The invention provides a multistage switch having low timing jitter and capable of producing multiple spark channels for spreading current over a wider area to reduce electrode damage and increase switch lifetime. The switch has fairly uniform electric fields and a short spark gap for laser triggering and is engineered to prevent insulator breakdowns.

Efficient modeling of phase jitter in dispersion-managed soliton systems.

PubMed

McKinstrie, C J; Xie, C; Lakoba, T I

2002-11-01

The variational method is used to derive correlation equations that model phase jitter in dispersion-managed soliton systems. The predictions of these correlation equations are consistent with numerical solutions of the nonlinear Schrödinger equation on which they are based.

Low jitter, low inductance solid dielectric switches.

PubMed

Guenther, A H; Strickland, D M; Bettis, J R

1979-11-01

It has been shown that the use of graded solid dielectric sandwiches in laser-triggered spark gaps (LTS) can lead to highly desirable multichannel operations while maintaining the low delay and jitter performance characteristics of LTS. As many as ten separate breakdown channels were observed when small circular or hexagonal aluminum inserts were inserted between two Mylar dielectric sheets stressed at 4.1 kV/mil. A reduction in rise time was noted for these multichannel switching events.

Avalanche buildup and propagation effects on photon-timing jitter in Si-SPAD with non-uniform electric field

NASA Astrophysics Data System (ADS)

Ingargiola, Antonino; Assanelli, Mattia; Gallivanoni, Andrea; Rech, Ivan; Ghioni, Massimo; Cova, Sergio

2009-05-01

Improving SPAD performances, such as dark count rate and quantum efficiency, without degrading the photontiming jitter is a challenging task that requires a clear understanding of the physical mechanisms involved. In this paper we investigate the contribution of the avalanche buildup statistics and the lateral avalanche propagation to the photon-timing jitter in silicon SPAD devices. Recent works on the buildup statistics focused on the uniform electric field case, however these results can not be applied to Si SPAD devices in which field profile is far from constant. We developed a 1-D Monte Carlo (MC) simulator using the real non-uniform field profiles derived from Secondary Ion Mass Spectroscopy (SIMS) measurements. Local and non-local models for impact ionization phenomena were considered. The obtained results, in particular the mean multiplication rate and jitter of the buildup filament, allowed us to simulate the statistical spread of the avalanche current on the device active area. We included space charge effects and a detailed lumped model for the external electronics and parasitics. We found that, in agreement with some experimental evidences, the avalanche buildup contribution to the total timing jitter is non-negligible in our devices. Moreover the lateral propagation gives an additional contribution that can explain the increasing trend of the photon-timing jitter with the comparator threshold.

Requirements Formulation and Dynamic Jitter Analysis for Fourier-Kelvin Stellar Interferometer

NASA Technical Reports Server (NTRS)

Liu, Kuo-Chia; Hyde, Tristram; Blaurock, Carl; Bolognese, Jeff; Howard, Joseph; Danchi, William

2004-01-01

The Fourier-Kelvin Stellar Interferometer (FKSI) has been proposed to detect and characterize extra solar giant planets. The baseline configuration for FKSI is a two- aperture, structurally connected nulling interferometer, capable of providing null depth less than lo4 in the infrared. The objective of this paper is to summarize the process for setting the top level requirements and the jitter analysis performed on FKSI to date. The first part of the paper discusses the derivation of dynamic stability requirements, necessary for meeting the FKSI nulling demands. An integrated model including structures, optics, and control systems has been developed to support dynamic jitter analysis and requirements verification. The second part of the paper describes how the integrated model is used to investigate the effects of reaction wheel disturbances on pointing and optical path difference stabilities.

Phase jitter in a differential phase experiment.

NASA Technical Reports Server (NTRS)

Tanenbaum, B. S.; Connolly, D. J.; Austin, G. L.

1973-01-01

Austin (1971) had concluded that, because of the 'phase jitter,' the differential phase experiment is useful over a more limited height range than the differential absorption experiment. Several observations are presented to show that this conclusion is premature. It is pointed out that the logical basis of the differential absorption experiment also requires that the O- and X-mode echoes, at a given time, come from the same irregularities. Austin's calculations are believed to contain a systematic error above 80 km.

Sloshing dynamics modulated fluid angular momentum and moment fluctuations driven by orbital gravity gradient and jitter accelerations in microgravity

NASA Technical Reports Server (NTRS)

Hung, R. J.; Pan, H. L.

1995-01-01

The dynamical behavior of spacecraft propellant affected by the asymmetric combined gravity gradient and jitter accelerations, in particular the effect of surface tension on partially-filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank has been investigated. Three different cases of orbital accelerations: (1) gravity gradient-dominated, (2) equally weighted between gravity gradient and jitter, and (3) gravity jitter-dominated accelerations are studied. The results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient-dominated accelerations provide a torsional moment with tidal motion of bubble oscillations in the rotating dewar. The results are clearly seen from the twisting shape of the bubble oscillations driven by gravity gradient-dominated acceleration. The results of slosh wave excitation along the liquid-vapor interface induced by gravity jitter-dominated acceleration indicate the results of bubble motion in a manner of down-and-up and leftward-and-rightward movement of oscillation when the bubble is rotating with respect to rotating dewar axis. Fluctuations of angular momentum, fluid moment and bubble mass center caused by slosh wave excitations driven by gravity gradient acceleration or gravity jitter acceleration are also investigated.

Reduction of timing jitter in passively Q-switched microchip lasers using self-injection seeding.

PubMed

Steinmetz, Alexander; Nodop, Dirk; Martin, Andreas; Limpert, Jens; Tünnermann, Andreas

2010-09-01

We present an efficient, simple, and passive technique for the reduction of timing jitter in passively Q-switched microchip lasers via self-injection seeding using a fiber delay line. The presented approach mitigates one inherent issue of passively Q-switched lasers without the need for active stabilization. At a repetition rate of a few hundred kilohertz and pulse duration of approximately 200 ps delivered by a microchip laser, the rms jitter is reduced from several nanoseconds down to 20 ps, hence, significantly below the pulse duration of the laser source.

Simulation of Relativistic Shocks and Associated Self-Consistent Radiation

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Mizuno, Y.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.;

RF Jitter Modulation Alignment Sensing

NASA Astrophysics Data System (ADS)

Ortega, L. F.; Fulda, P.; Diaz-Ortiz, M.; Perez Sanchez, G.; Ciani, G.; Voss, D.; Mueller, G.; Tanner, D. B.

2017-01-01

We will present the numerical and experimental results of a new alignment sensing scheme which can reduce the complexity of alignment sensing systems currently used, while maintaining the same shot noise limited sensitivity. This scheme relies on the ability of electro-optic beam deflectors to create angular modulation sidebands in radio frequency, and needs only a single-element photodiode and IQ demodulation to generate error signals for tilt and translation degrees of freedom in one dimension. It distances itself from current techniques by eliminating the need for beam centering servo systems, quadrant photodetectors and Gouy phase telescopes. RF Jitter alignment sensing can be used to reduce the complexity in the alignment systems of many laser optical experiments, including LIGO and the ALPS experiment.

Reduction of timing jitter and intensity noise in normal-dispersion passively mode-locked fiber lasers by narrow band-pass filtering.

PubMed

Qin, Peng; Song, Youjian; Kim, Hyoji; Shin, Junho; Kwon, Dohyeon; Hu, Minglie; Wang, Chingyue; Kim, Jungwon

2014-11-17

Fiber lasers mode-locked with normal cavity dispersion have recently attracted great attention due to large output pulse energy and femtosecond pulse duration. Here we accurately characterized the timing jitter of normal-dispersion fiber lasers using a balanced cross-correlation method. The timing jitter characterization experiments show that the timing jitter of normal-dispersion mode-locked fiber lasers can be significantly reduced by using narrow band-pass filtering (e.g., 7-nm bandwidth filtering in this work). We further identify that the timing jitter of the fiber laser is confined in a limited range, which is almost independent of cavity dispersion map due to the amplifier-similariton formation by insertion of the narrow bandpass filter. The lowest observed timing jitter reaches 0.57 fs (rms) integrated from 10 kHz to 10 MHz Fourier frequency. The rms relative intensity noise (RIN) is also reduced from 0.37% to 0.02% (integrated from 1 kHz to 5 MHz Fourier frequency) by the insertion of narrow band-pass filter.

Broadband noise limit in the photodetection of ultralow jitter optical pulses.

PubMed

Sun, Wenlu; Quinlan, Franklyn; Fortier, Tara M; Deschenes, Jean-Daniel; Fu, Yang; Diddams, Scott A; Campbell, Joe C

2014-11-14

Applications with optical atomic clocks and precision timing often require the transfer of optical frequency references to the electrical domain with extremely high fidelity. Here we examine the impact of photocarrier scattering and distributed absorption on the photocurrent noise of high-speed photodiodes when detecting ultralow jitter optical pulses. Despite its small contribution to the total photocurrent, this excess noise can determine the phase noise and timing jitter of microwave signals generated by detecting ultrashort optical pulses. A Monte Carlo simulation of the photodetection process is used to quantitatively estimate the excess noise. Simulated phase noise on the 10 GHz harmonic of a photodetected pulse train shows good agreement with previous experimental data, leading to the conclusion that the lowest phase noise photonically generated microwave signals are limited by photocarrier scattering well above the quantum limit of the optical pulse train.

Variable Delay Element For Jitter Control In High Speed Data Links

DOEpatents

Livolsi, Robert R.

2002-06-11

A circuit and method for decreasing the amount of jitter present at the receiver input of high speed data links which uses a driver circuit for input from a high speed data link which comprises a logic circuit having a first section (1) which provides data latches, a second section (2) which provides a circuit generates a pre-destorted output and for compensating for level dependent jitter having an OR function element and a NOR function element each of which is coupled to two inputs and to a variable delay element as an input which provides a bi-modal delay for pulse width pre-distortion, a third section (3) which provides a muxing circuit, and a forth section (4) for clock distribution in the driver circuit. A fifth section is used for logic testing the driver circuit.

LANDSAT-D MSS/TM tuned orbital jitter analysis model LDS900

NASA Technical Reports Server (NTRS)

Pollak, T. E.

1981-01-01

The final LANDSAT-D orbital dynamic math model (LSD900), comprised of all test validated substructures, was used to evaluate the jitter response of the MSS/TM experiments. A dynamic forced response analysis was performed at both the MSS and TM locations on all structural modes considered (thru 200 Hz). The analysis determined the roll angular response of the MSS/TM experiments to improve excitation generated by component operation. Cross axis and cross experiment responses were also calculated. The excitations were analytically represented by seven and nine term Fourier series approximations, for the MSS and TM experiment respectively, which enabled linear harmonic solution techniques to be applied to response calculations. Single worst case jitter was estimated by variations of the eigenvalue spectrum of model LSD 900. The probability of any worst case mode occurrence was investigated.

Astrometric Jitter of the Sun as a Star

DTIC Science & Technology

2010-05-01

active, fast-rotating stars. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology...as the Sun is not affected by star spot noise, but the prospects for more active stars may be limited to giant planets. Subject headings: open clusters ...nearby dwarfs should be as amenable to exoplanet detection as the Sun. The aim of this paper is to determine the solar astrometric jitter directly

Multifrequency zero-jitter delay-locked loop

NASA Astrophysics Data System (ADS)

Efendovich, Avner; Afek, Yachin; Sella, Coby; Bikowsky, Zeev

1994-01-01

The approach of an all-digital phase locked loop is used in this delay-locked loop circuit. This design is designated to a system with two processing units, a master CPU and a slave system chip, that share the same bus. It allows maximum utilization of the bus, as the minimal skew between the clocks of the two components significantly reduces idle periods, and also set-up and hold times. Changes in the operating frequency are possible, without falling out of synchronization. Due to the special lead-lag phase detector, the jitter of the clock is zero, when the loop is locked, under any working conditions.

Intracavity dispersion effect on timing jitter of ultralow noise mode-locked semiconductor based external-cavity laser.

PubMed

Gee, S; Ozharar, S; Plant, J J; Juodawlkis, P W; Delfyett, P J

2009-02-01

We report the generation of optical pulse trains with 380 as of residual timing jitter (1 Hz-1 MHz) from a mode-locked external-cavity semiconductor laser, through a combination of optimizing the intracavity dispersion and utilizing a high-power, low-noise InGaAsP quantum-well slab-coupled optical waveguide amplifier gain medium. This is, to our knowledge, the lowest residual timing jitter reported to date from an actively mode-locked laser.

Effect of Magnetic Fields on g-jitter Induced Convection and Solute Striation During Space Processing of Single Crystals

NASA Technical Reports Server (NTRS)

deGroh, H. C.; Li, K.; Li, B. Q.

2002-01-01

A 2-D finite element model is presented for the melt growth of single crystals in a microgravity environment with a superimposed DC magnetic field. The model is developed based on the deforming finite element methodology and is capable of predicting the phenomena of the steady and transient convective flows, heat transfer, solute distribution, and solid-liquid interface morphology associated with the melt growth of single crystals in microgravity with and without an applied magnetic field. Numerical simulations were carried out for a wide range of parameters including idealized microgravity conditions, the synthesized g-jitter and the real g-jitter data taken by on-board accelerometers during space flights. The results reveal that the time varying g-jitter disturbances, although small in magnitude, cause an appreciable convective flow in the liquid pool, which in turn produces detrimental effects during the space processing of single crystal growth. An applied magnetic field of appropriate strength, superimposed on microgravity, can be very effective in suppressing the deleterious effects resulting from the g-jitter disturbances.

Effects of g-Jitter on Diffusion in Binary Liquids

NASA Technical Reports Server (NTRS)

Duval, Walter M. B.

1999-01-01

The microgravity environment offers the potential to measure the binary diffusion coefficients in liquids without the masking effects introduced by buoyancy-induced flows due to Earth s gravity. However, the background g-jitter (vibrations from the shuttle, onboard machinery, and crew) normally encountered in many shuttle experiments may alter the benefits of the microgravity environment and introduce vibrations that could offset its intrinsic advantages. An experiment during STS-85 (August 1997) used the Microgravity Vibration Isolation Mount (MIM) to isolate and introduce controlled vibrations to two miscible liquids inside a cavity to study the effects of g-jitter on liquid diffusion. Diffusion in a nonhomogeneous liquid system is caused by a nonequilibrium condition that results in the transport of mass (dispersion of the different kinds of liquid molecules) to approach equilibrium. The dynamic state of the system tends toward equilibrium such that the system becomes homogeneous. An everyday example is the mixing of cream and coffee (a nonhomogeneous system) via stirring. The cream diffuses into the coffee, thus forming a homogeneous system. At equilibrium the system is said to be mixed. However, during stirring, simple observations show complex flow field dynamics-stretching and folding of material interfaces, thinning of striation thickness, self-similar patterns, and so on. This example illustrates that, even though mixing occurs via mass diffusion, stirring to enhance transport plays a major role. Stirring can be induced either by mechanical means (spoon or plastic stirrer) or via buoyancy-induced forces caused by Earth s gravity. Accurate measurements of binary diffusion coefficients are often inhibited by buoyancy-induced flows. The microgravity environment minimizes the effect of buoyancy-induced flows and allows the true diffusion limit to be achieved. One goal of this experiment was to show that the microgravity environment suppresses buoyancy

Simulation of Combustion Systems with Realistic g-jitter

NASA Technical Reports Server (NTRS)

Mell, William E.; McGrattan, Kevin B.; Baum, Howard R.

2003-01-01

In this project a transient, fully three-dimensional computer simulation code was developed to simulate the effects of realistic g-jitter on a number of combustion systems. The simulation code is capable of simulating flame spread on a solid and nonpremixed or premixed gaseous combustion in nonturbulent flow with simple combustion models. Simple combustion models were used to preserve computational efficiency since this is meant to be an engineering code. Also, the use of sophisticated turbulence models was not pursued (a simple Smagorinsky type model can be implemented if deemed appropriate) because if flow velocities are large enough for turbulence to develop in a reduced gravity combustion scenario it is unlikely that g-jitter disturbances (in NASA's reduced gravity facilities) will play an important role in the flame dynamics. Acceleration disturbances of realistic orientation, magnitude, and time dependence can be easily included in the simulation. The simulation algorithm was based on techniques used in an existing large eddy simulation code which has successfully simulated fire dynamics in complex domains. A series of simulations with measured and predicted acceleration disturbances on the International Space Station (ISS) are presented. The results of this series of simulations suggested a passive isolation system and appropriate scheduling of crew activity would provide a sufficiently "quiet" acceleration environment for spherical diffusion flames.

Wide tracking range, auto ranging, low jitter phase lock loop for swept and fixed frequency systems

DOEpatents

Kerner, Thomas M.

2001-01-01

The present invention provides a wide tracking range phase locked loop (PLL) circuit that achieves minimal jitter in a recovered clock signal, regardless of the source of the jitter (i.e. whether it is in the source or the transmission media). The present invention PLL has automatic harmonic lockout detection circuitry via a novel lock and seek control logic in electrical communication with a programmable frequency discriminator and a code balance detector. (The frequency discriminator enables preset of a frequency window of upper and lower frequency limits to derive a programmable range within which signal acquisition is effected. The discriminator works in combination with the code balance detector circuit to minimize the sensitivity of the PLL circuit to random data in the data stream). In addition, the combination of a differential loop integrator with the lock and seek control logic obviates a code preamble and guarantees signal acquisition without harmonic lockup. An adaptive cable equalizer is desirably used in combination with the present invention PLL to recover encoded transmissions containing a clock and/or data. The equalizer automatically adapts to equalize short haul cable lengths of coaxial and twisted pair cables or wires and provides superior jitter performance itself. The combination of the equalizer with the present invention PLL is desirable in that such combination permits the use of short haul wires without significant jitter.

Influence of G-jitter on the characteristics of a non-premixed flame: Experimental approach

NASA Astrophysics Data System (ADS)

Joulain, Pierre; Cordeiro, Pierre; Rouvreau, Sébastien; Legros, Guillaume; Fuentes, Andres; Torero, José L.

2005-03-01

The combustion of a flat plate in a boundary layer under microgravity conditions, which was first described by Emmons, is studied using a gas burner. Magnitude of injection and blowing velocities are chosen to be characteristic of pyrolyzing velocity of solid fuels, and of ventilation systems in space stations. These velocities are about 0.1 m/s for oxidiser flow and 0.004m/s for fuel flow. In this configuration, flame layout results from a coupled interaction between oxidiser flow, fuel flow and thermal expansion. Influences of these parameters are studied experimentally by means of flame length and standoff distance measurements using CH* chemiluminescence's and visible emission of the flame. Flow was also studied with Particle Image Velocimetry (PIV). Inert flows, with and without injection, and reacting flow in a microgravity environment were considered to distinguish aerodynamic from thermal effect. Thermal expansion effects have been shown by means of the acceleration of oxidiser flow. Three-dimensional effects, which are strongly marked for high injection velocities were studied. Three-dimensional tools adaptability to parabolic flights particular conditions were of concern. Flame sensitivity to g-jitters was investigated according to g-jitters frequency and range involved by parabolic flights. It appears that flame location (standoff distance), flame characteristics (length, thickness, brightness) and the aerodynamic field of the low velocity reacting flow are very much affected by the fluctuation of the gravity level or g-jitter. The lower the g-jitter frequency is, the higher the perturbation. Consequently it is difficult to perform relevant experiments for a main flow velocity lower than 0.05m/s. DNS calculations confirm the present observations, but most of the results are presented elsewhere.

Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Mizuno, Y.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.;

High performance thyratron driver with low jitter.

PubMed

Verma, Rishi; Lee, P; Springham, S V; Tan, T L; Rawat, R S

2007-08-01

We report the design and development of insulated gate bipolar junction transistor based high performance driver for operating thyratrons in grounded grid mode. With careful design, the driver meets the specification of trigger output pulse rise time less than 30 ns, jitter less than +/-1 ns, and time delay less than 160 ns. It produces a -600 V pulse of 500 ns duration (full width at half maximum) at repetition rate ranging from 1 Hz to 1.14 kHz. The developed module also facilitates heating and biasing units along with protection circuitry in one complete package.

GABAergic excitation of spider mechanoreceptors increases information capacity by increasing entropy rather than decreasing jitter.

PubMed

Pfeiffer, Keram; French, Andrew S

2009-09-02

Neurotransmitter chemicals excite or inhibit a range of sensory afferents and sensory pathways. These changes in firing rate or static sensitivity can also be associated with changes in dynamic sensitivity or membrane noise and thus action potential timing. We measured action potential firing produced by random mechanical stimulation of spider mechanoreceptor neurons during long-duration excitation by the GABAA agonist muscimol. Information capacity was estimated from signal-to-noise ratio by averaging responses to repeated identical stimulation sequences. Information capacity was also estimated from the coherence function between input and output signals. Entropy rate was estimated by a data compression algorithm and maximum entropy rate from the firing rate. Action potential timing variability, or jitter, was measured as normalized interspike interval distance. Muscimol increased firing rate, information capacity, and entropy rate, but jitter was unchanged. We compared these data with the effects of increasing firing rate by current injection. Our results indicate that the major increase in information capacity by neurotransmitter action arose from the increased entropy rate produced by increased firing rate, not from reduction in membrane noise and action potential jitter.

Low-sensitivity H ∞ filter design for linear delta operator systems with sampling time jitter

NASA Astrophysics Data System (ADS)

Guo, Xiang-Gui; Yang, Guang-Hong

2012-04-01

This article is concerned with the problem of designing H ∞ filters for a class of linear discrete-time systems with low-sensitivity to sampling time jitter via delta operator approach. Delta-domain model is used to avoid the inherent numerical ill-condition resulting from the use of the standard shift-domain model at high sampling rates. Based on projection lemma in combination with the descriptor system approach often used to solve problems related to delay, a novel bounded real lemma with three slack variables for delta operator systems is presented. A sensitivity approach based on this novel lemma is proposed to mitigate the effects of sampling time jitter on system performance. Then, the problem of designing a low-sensitivity filter can be reduced to a convex optimisation problem. An important consideration in the design of correlation filters is the optimal trade-off between the standard H ∞ criterion and the sensitivity of the transfer function with respect to sampling time jitter. Finally, a numerical example demonstrating the validity of the proposed design method is given.

Note: A new method for directly reducing the sampling jitter noise of the digital phasemeter

NASA Astrophysics Data System (ADS)

Liang, Yu-Rong

2018-03-01

The sampling jitter noise is one non-negligible noise source of the digital phasemeter used for space gravitational wave detection missions. This note provides a new method for directly reducing the sampling jitter noise of the digital phasemeter, by adding a dedicated signal of which the frequency, amplitude, and initial phase should be pre-set. In contrast to the phase correction using the pilot-tone in the work of Burnett, Gerberding et al., Liang et al., Ales et al., Gerberding et al., and Ware et al. [M.Sc. thesis, Luleå University of Technology, 2010; Classical Quantum Gravity 30, 235029 (2013); Rev. Sci. Instrum. 86, 016106 (2015); Rev. Sci. Instrum. 86, 084502 (2015); Rev. Sci. Instrum. 86, 074501 (2015); and Proceedings of the Earth Science Technology Conference (NASA, USA, 2006)], the new method is intrinsically additive noise suppression. The experiment results validate that the new method directly reduces the sampling jitter noise without data post-processing and provides the same phase measurement noise level (10-6 rad/Hz1/2 at 0.1 Hz) as the pilot-tone correction.

The effect of jitter on the performance of space coherent optical communication system with Costas loop

NASA Astrophysics Data System (ADS)

Li, Xin; Hong, Yifeng; Wang, Jinfang; Liu, Yang; Sun, Xun; Li, Mi

2018-01-01

Numerous communication techniques and optical devices successfully applied in space optical communication system indicates a good portability of it. With this good portability, typical coherent demodulation technique of Costas loop can be easily adopted in space optical communication system. As one of the components of pointing error, the effect of jitter plays an important role in the communication quality of such system. Here, we obtain the probability density functions (PDF) of different jitter degrees and explain their essential effect on the bit error rate (BER) space optical communication system. Also, under the effect of jitter, we research the bit error rate of space coherent optical communication system using Costas loop with different system parameters of transmission power, divergence angle, receiving diameter, avalanche photodiode (APD) gain, and phase deviation caused by Costas loop. Through a numerical simulation of this kind of communication system, we demonstrate the relationship between the BER and these system parameters, and some corresponding methods of system optimization are presented to enhance the communication quality.

Reorientation of rotating fluid in microgravity environment with and without gravity jitters

NASA Technical Reports Server (NTRS)

Hung, R. J.; Lee, C. C.; Shyu, K. L.

1990-01-01

In a spacecraft design, the requirements of settled propellant are different for tank pressurization, engine restart, venting, or propellant transfer. The requirement to settle or to position liquid fuel over the outlet end of the spacecraft propellant tank prior main engine restart poses a microgravity fluid behavior problem. In this paper, the dynamical behavior of liquid propellant, fluid reorientation, and propellant resettling have been carried out through the execution of supercomputer CRAY X-MP to simulate the fluid management in a microgravity environment. Results show that the resettlement of fluid can be accomplished more efficiently for fluid in rotating tank than in nonrotating tank, and also better performance for gravity jitters imposed on fluid settlement than without gravity jitters based on the amount of time needed to carry out resettlement period of time between the initiation and termination of geysering.

Attitude determination for high-accuracy submicroradian jitter pointing on space-based platforms

NASA Astrophysics Data System (ADS)

Gupta, Avanindra A.; van Houten, Charles N.; Germann, Lawrence M.

1990-10-01

A description of the requirement definition process is given for a new wideband attitude determination subsystem (ADS) for image motion compensation (IMC) systems. The subsystem consists of either lateral accelerometers functioning in differential pairs or gas-bearing gyros for high-frequency sensors using CCD-based star trackers for low-frequency sensors. To minimize error the sensor signals are combined so that the mixing filter does not allow phase distortion. The two ADS models are introduced in an IMC simulation to predict measurement error, correction capability, and residual image jitter for a variety of system parameters. The IMC three-axis testbed is utilized to simulate an incoming beam in inertial space. Results demonstrate that both mechanical and electronic IMC meet the requirements of image stabilization for space-based observation at submicroradian-jitter levels. Currently available technology may be employed to implement IMC systems.

Superior bit error rate and jitter due to improved switching field distribution in exchange spring magnetic recording media

PubMed Central

Suess, D.; Fuger, M.; Abert, C.; Bruckner, F.; Vogler, C.

2016-01-01

We report two effects that lead to a significant reduction of the switching field distribution in exchange spring media. The first effect relies on a subtle mechanism of the interplay between exchange coupling between soft and hard layers and anisotropy that allows significant reduction of the switching field distribution in exchange spring media. This effect reduces the switching field distribution by about 30% compared to single-phase media. A second effect is that due to the improved thermal stability of exchange spring media over single-phase media, the jitter due to thermal fluctuation is significantly smaller for exchange spring media than for single-phase media. The influence of this overall improved switching field distribution on the transition jitter in granular recording and the bit error rate in bit-patterned magnetic recording is discussed. The transition jitter in granular recording for a distribution of Khard values of 3% in the hard layer, taking into account thermal fluctuations during recording, is estimated to be a = 0.78 nm, which is similar to the best reported calculated jitter in optimized heat-assisted recording media. PMID:27245287

Biological Complexities in Radiation Carcinogenesis and Cancer Radiotherapy: Impact of New Biological Paradigms

PubMed Central

Mozdarani, Hossein

2012-01-01

Although radiation carcinogenesis has been shown both experimentally and epidemiologically, the use of ionizing radiation is also one of the major modalities in cancer treatment. Various known cellular and molecular events are involved in carcinogenesis. Apart from the known phenomena, there could be implications for carcinogenesis and cancer prevention due to other biological processes such as the bystander effect, the abscopal effect, intrinsic radiosensitivity and radioadaptation. Bystander effects have consequences for mutation initiated cancer paradigms of radiation carcinogenesis, which provide the mechanistic justification for low-dose risk estimates. The abscopal effect is potentially important for tumor control and is mediated through cytokines and/or the immune system (mainly cell-mediated immunity). It results from loss of growth and stimulatory and/or immunosuppressive factors from the tumor. Intrinsic radiosensitivity is a feature of some cancer prone chromosomal breakage syndromes such as ataxia telangectiasia. Radiosensitivity is manifested as higher chromosomal aberrations and DNA repair impairment is now known as a good biomarker for breast cancer screening and prediction of prognosis. However, it is not yet known whether this effect is good or bad for those receiving radiation or radiomimetic agents for treatment. Radiation hormesis is another major concern for carcinogenesis. This process which protects cells from higher doses of radiation or radio mimic chemicals, may lead to the escape of cells from mitotic death or apoptosis and put cells with a lower amount of damage into the process of cancer induction. Therefore, any of these biological phenomena could have impact on another process giving rise to genome instability of cells which are not in the field of radiation but still receiving a lower amount of radiation. For prevention of radiation induced carcinogenesis or risk assessment as well as for successful radiation therapy, all these

On the effects of phase jitter on QPSK lock detection

NASA Technical Reports Server (NTRS)

Mileant, A.; Hinedi, S.

1993-01-01

The performance of a QPSK (quadrature phase-shift keying) lock detector is described, taking into account the degradation due to carrier phase jitter. Such an analysis is necessary for accurate performance prediction purposes in scenarios where both the loop SNR is low and the estimation period is short. The derived formulas are applicable to several QPSK loops and are verified using computer simulations.

Data Reduction of Jittered Infrared Images Using the ORAC Pipeline

NASA Astrophysics Data System (ADS)

Currie, Malcolm; Wright, Gillian; Bridger, Alan; Economou, Frossie

We relate our experiences using the ORAC data reduction pipeline for jittered images of stars and galaxies. The reduction recipes currently combine applications from several Starlink packages with intelligent Perl recipes to cater to UKIRT data. We describe the recipes and some of the algorithms used, and compare the quality of the resultant mosaics and photometry with the existing facilities.

ISAAC Photometric Comparison of ECLIPSE Jitter and the ORAC-DR Equivalent Recipe for ISAAC

NASA Astrophysics Data System (ADS)

Currie, M. J.

2005-12-01

Motivated by a request from astronomers demanding accurate and consistent infrared photometry, I compare the photometry and quality of mosaics generated by the ECLIPSE jitter task and the ORAC-DR JITTER_SELF_FLAT recipe in two fields. The current (v4.9.0) ECLIPSE produces photometry a few percent fainter than ORAC-DR; the systematic trend with magnitude seen in v4.4.1 is now removed. Random errors arising from poor flat-fielding are not resolved. ECLIPSE generates noisier mosaics; ORAC-DR has poorer bias removal in crowded fields and defaults to larger mosaics. ORAC-DR runs a few times slower than ECLIPSE, but its recipe development is measured in weeks, not years.

Acquisition and Initial Analysis of H+- and H--Beam Centroid Jitter at LANSCE

NASA Astrophysics Data System (ADS)

Gilpatrick, J. D.; Bitteker, L.; Gulley, M. S.; Kerstiens, D.; Oothoudt, M.; Pillai, C.; Power, J.; Shelley, F.

2006-11-01

During the 2005 Los Alamos Neutron Science Center (LANSCE) beam runs, beam current and centroid-jitter data were observed, acquired, analyzed, and documented for both the LANSCE H+ and H- beams. These data were acquired using three beam position monitors (BPMs) from the 100-MeV Isotope Production Facility (IPF) beam line and three BPMs from the Switchyard transport line at the end of the LANSCE 800-MeV linac. The two types of data acquired, intermacropulse and intramacropulse, were analyzed for statistical and frequency characteristics as well as various other correlations including comparing their phase-space like characteristics in a coordinate system of transverse angle versus transverse position. This paper will briefly describe the measurements required to acquire these data, the initial analysis of these jitter data, and some interesting dilemmas these data presented.

A compact, low jitter, nanosecond rise time, high voltage pulse generator with variable amplitude.

PubMed

Mao, Jiubing; Wang, Xin; Tang, Dan; Lv, Huayi; Li, Chengxin; Shao, Yanhua; Qin, Lan

2012-07-01

In this paper, a compact, low jitter, nanosecond rise time, command triggered, high peak power, gas-switch pulse generator system is developed for high energy physics experiment. The main components of the system are a high voltage capacitor, the spark gap switch and R = 50 Ω load resistance built into a structure to obtain a fast high power pulse. The pulse drive unit, comprised of a vacuum planar triode and a stack of avalanche transistors, is command triggered by a single or multiple TTL (transistor-transistor logic) level pulses generated by a trigger pulse control unit implemented using the 555 timer circuit. The control unit also accepts user input TTL trigger signal. The vacuum planar triode in the pulse driving unit that close the first stage switches is applied to drive the spark gap reducing jitter. By adjusting the charge voltage of a high voltage capacitor charging power supply, the pulse amplitude varies from 5 kV to 10 kV, with a rise time of <3 ns and the maximum peak current up to 200 A (into 50 Ω). The jitter of the pulse generator system is less than 1 ns. The maximum pulse repetition rate is set at 10 Hz that limited only by the gas-switch and available capacitor recovery time.

Microscopic Processes On Radiation from Accelerated Particles in Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P. E.; Mizuno, Y.; Medvedev, M.; Zhang, B.; Sol, H.; Niemiec, J.; Pohl, M.; Nordlund, A.; Fredriksen, J.;

An examination of anticipated g-jitter on Space Station and its effects on materials processes

NASA Technical Reports Server (NTRS)

Nelson, Emily S.

1994-01-01

This study is concerned with the effects of g-jitter, the residual acceleration aboard spacecraft, on selected classes of materials processes. In particular, the anticipated acceleration environment aboard Space Station Freedom (SSF) and its potential effects are analyzed, but the topic is covered with a sufficient level of generality as to apply to other processes and to other vehicles as well. Some of the key findings of this study include: The present acceleration specifications for SSF are inadequate to assure a quality level low-g environment. The local g vector orientation is an extremely sensitive parameter for certain key processes, but can not be controlled to within the desired tolerance. Therefore, less emphasis should be placed upon achieving a tight control of SSF attitude, but more emphasis should be focused on reducing the overall level of the g-jitter magnitude. Melt-based crystal growth may not be successfully processed in the relatively noisy environment of a large inhabited space structure. Growth from vapor or from solution appears more favorable. A smaller space structure and/or a free flyer can provide better alternatives in terms of g-jitter considerations. A high priority (including budgetary) should be given to coordinated efforts among researchers, SSF designers, and equipment contractors, to develop practical experiment-specific sensitivity requirements. Combined focused numerical simulations and experiments with well-resolved acceleration measurements should be vigorously pursued for developing reliable experiment-specific sensitivity data. Appendices provide an extensive cross-referenced bibliography, a discussion of the merits offered by g-jitter analysis techniques, as well as definitions of relevant nondimensional quantities and a brief description of available accelerometry hardware.

Note: Design and implementation of a home-built imaging system with low jitter for cold atom experiments

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

Hachtel, A. J.; Gillette, M. C.; Clements, E. R.

A novel home-built system for imaging cold atom samples is presented using a readily available astronomy camera which has the requisite sensitivity but no timing-control. We integrate the camera with LabVIEW achieving fast, low-jitter imaging with a convenient user-defined interface. We show that our system takes precisely timed millisecond exposures and offers significant improvements in terms of system jitter and readout time over previously reported home-built systems. Our system rivals current commercial “black box” systems in performance and user-friendliness.

A 250 MHz, high power mode-locked Nd:GdVO4 oscillator with low timing jitter under 879 nm direct pumping

NASA Astrophysics Data System (ADS)

Zhang, F. F.; Zuo, J. W.; Wang, Z. M.; Yang, J.; Cheng, H. L.; Zong, N.; Yang, F.; Peng, Q. J.; Xu, Z. Y.

2013-04-01

We developed a high power mode-locked Nd:GdVO4 oscillator with low timing jitter directly pumped by an 879 nm diode. Under the absorbed pump power of 13.8 W, a maximum output power of 5.68 W at 1063 nm was obtained with a repetition rate of ˜250 MHz, corresponding to a slope efficiency of 78.7%. The measured pulse width and root mean square timing jitter at the output power of 5.35 W were 7.4 ps and 286 fs, respectively. To the best of our knowledge, this is the highest output power for a picosecond Nd:GdVO4 oscillator with low timing jitter.

G-jitter Effects on Transport and Pattern Formation

NASA Technical Reports Server (NTRS)

Schatz, Michael F.

2003-01-01

The research performed under this grant has led to an number of new insights into two general categories of fluid flows in the presence of time-dependent acceleration, as outlined briefly below. These results have been widely communicated in the scientific community through seven presentations at international conferences (4 invited, 3 contributed), five published papers (4 journal articles and 1 conference proceeding), and images from the research featured on the cover of all 2003 editions of the research journal, Nonlinearity. The work performed under this proposal also contained a substantial educational component by contributed significantly to the scientific training of one postdoctoral associate, one Ph.D. student and five undergraduate researchers. One main area of focus in this research was convective flow with time-dependent acceleration. Convection is one class of behavior that can arise from g-jitter effects. Our research focused on studies of Rayleigh-Benard system, which is an important model for understanding thermal convection; studies of this problem in the presence of acceleration modulations provided insight into the nature of g-jitter induced flow and of the effects of modulation and noise on non-equilibrium pattern formation. Our experiments on vertically vibrated Rayleigh-Benard convection demonstrated the existence of two classes of pure flow patterns (synchronous & subharmonic) patterns) that had long been predicted by theory but never before observed experimentally. Detailed studies of ranges of parameters where both classes of patterns exist simultaneously led to the discovery of a new type of patterns (called superlattices) in systems driven out of thermodynamic equilibrium.

100 km differential phase shift quantum key distribution experiment with low jitter up-conversion detectors

NASA Astrophysics Data System (ADS)

Diamanti, Eleni; Takesue, Hiroki; Langrock, Carsten; Fejer, M. M.; Yamamoto, Yoshihisa

2006-12-01

We present a quantum key distribution experiment in which keys that were secure against all individual eavesdropping attacks allowed by quantum mechanics were distributed over 100 km of optical fiber. We implemented the differential phase shift quantum key distribution protocol and used low timing jitter 1.55 µm single-photon detectors based on frequency up-conversion in periodically poled lithium niobate waveguides and silicon avalanche photodiodes. Based on the security analysis of the protocol against general individual attacks, we generated secure keys at a practical rate of 166 bit/s over 100 km of fiber. The use of the low jitter detectors also increased the sifted key generation rate to 2 Mbit/s over 10 km of fiber.

Gigahertz repetition rate, sub-femtosecond timing jitter optical pulse train directly generated from a mode-locked Yb:KYW laser.

PubMed

Yang, Heewon; Kim, Hyoji; Shin, Junho; Kim, Chur; Choi, Sun Young; Kim, Guang-Hoon; Rotermund, Fabian; Kim, Jungwon

2014-01-01

We show that a 1.13 GHz repetition rate optical pulse train with 0.70 fs high-frequency timing jitter (integration bandwidth of 17.5 kHz-10 MHz, where the measurement instrument-limited noise floor contributes 0.41 fs in 10 MHz bandwidth) can be directly generated from a free-running, single-mode diode-pumped Yb:KYW laser mode-locked by single-wall carbon nanotube-coated mirrors. To our knowledge, this is the lowest-timing-jitter optical pulse train with gigahertz repetition rate ever measured. If this pulse train is used for direct sampling of 565 MHz signals (Nyquist frequency of the pulse train), the jitter level demonstrated would correspond to the projected effective-number-of-bit of 17.8, which is much higher than the thermal noise limit of 50 Ω load resistance (~14 bits).

Design of optical axis jitter control system for multi beam lasers based on FPGA

NASA Astrophysics Data System (ADS)

Ou, Long; Li, Guohui; Xie, Chuanlin; Zhou, Zhiqiang

2018-02-01

A design of optical axis closed-loop control system for multi beam lasers coherent combining based on FPGA was introduced. The system uses piezoelectric ceramics Fast Steering Mirrors (FSM) as actuator, the Fairfield spot detection of multi beam lasers by the high speed CMOS camera for optical detecting, a control system based on FPGA for real-time optical axis jitter suppression. The algorithm for optical axis centroid detecting and PID of anti-Integral saturation were realized by FPGA. Optimize the structure of logic circuit by reuse resource and pipeline, as a result of reducing logic resource but reduced the delay time, and the closed-loop bandwidth increases to 100Hz. The jitter of laser less than 40Hz was reduced 40dB. The cost of the system is low but it works stably.

Stochastic mechanical model of vocal folds for producing jitter and for identifying pathologies through real voices.

PubMed

Cataldo, E; Soize, C

2018-06-06

Jitter, in voice production applications, is a random phenomenon characterized by the deviation of the glottal cycle length with respect to a mean value. Its study can help in identifying pathologies related to the vocal folds according to the values obtained through the different ways to measure it. This paper aims to propose a stochastic model, considering three control parameters, to generate jitter based on a deterministic one-mass model for the dynamics of the vocal folds and to identify parameters from the stochastic model taking into account real voice signals experimentally obtained. To solve the corresponding stochastic inverse problem, the cost function used is based on the distance between probability density functions of the random variables associated with the fundamental frequencies obtained by the experimental voices and the simulated ones, and also on the distance between features extracted from the voice signals, simulated and experimental, to calculate jitter. The results obtained show that the model proposed is valid and some samples of voices are synthesized considering the identified parameters for normal and pathological cases. The strategy adopted is also a novelty and mainly because a solution was obtained. In addition to the use of three parameters to construct the model of jitter, it is the discussion of a parameter related to the bandwidth of the power spectral density function of the stochastic process to measure the quality of the signal generated. A study about the influence of all the main parameters is also performed. The identification of the parameters of the model considering pathological cases is maybe of all novelties introduced by the paper the most interesting. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dynamic/Jitter Assessment of Multiple Potential HabEx Structural Designs

NASA Technical Reports Server (NTRS)

Knight, J. Brent; Stahl, H. Philip; Singleton, Andrew William; Hunt, Ronald A.; Therrell, Melissa F.; Caldwell, Mary Kathryn; Garcia, Jay Clarke

2017-01-01

The 2020 Decadal Survey in Astronomy and Astrophysics will assess candidate large missions to follow James Webb Space Telescope (JWST) and Wide Field Infrared Space Telescope (WFIRST). One candidate mission is the Habitable ExoPlanet Imaging Mission (HabEx). This presentation describes two HabEx structural designs and results from structural dynamic analyses performed to predict Primary Mirror (PM) Secondary Mirror (SM) Line of Site (LOS) stability (jitter) due to Reaction Wheel Assembly (RWA) vibrations.

Removal of jitter noise in 3D shape recovery from image focus by using Kalman filter.

PubMed

Jang, Hoon-Seok; Muhammad, Mannan Saeed; Choi, Tae-Sun

2018-02-01

In regard to Shape from Focus, one critical factor impacting system application is mechanical vibration of the translational stage causing jitter noise along the optical axis. This noise is not detectable by simply observing the image. However, when focus measures are applied, inaccuracies in the depth occur. In this article, jitter noise and focus curves are modeled by Gaussian distribution and quadratic function, respectively. Then Kalman filter is designed and applied to eliminate this noise in the focus curves, as a post-processing step after the focus measure application. Experiments are implemented with simulated objects and real objects to show usefulness of proposed algorithm. © 2017 Wiley Periodicals, Inc.

Low-Timing-Jitter Near-Infrared Single-Photon-Sensitive 16-Channel Intensified-Photodiode Detector

NASA Technical Reports Server (NTRS)

Krainak, Michael A.; Lu, Wei; Yang, Guangning; Sun, Xiaoli; Sykora, Derek; Jurkovic, Mike; Aebi, Verle; Costello, Ken; Burns, Richard

2011-01-01

We developed a 16-channel InGaAsP photocathode intensified-photodiode (IPD) detector with 78 ps (1-sigma) timing-jitter, less than 500 ps FWHM impulse response, greater than 15% quantum efficiency at 1064 nm wavelength with 131 kcps dark counts at 15 C.

Jitter reduction of a reaction wheel by management of angular momentum using magnetic torquers in nano- and micro-satellites

NASA Astrophysics Data System (ADS)

Inamori, Takaya; Wang, Jihe; Saisutjarit, Phongsatorn; Nakasuka, Shinichi

2013-07-01

Nowadays, nano- and micro-satellites, which are smaller than conventional large satellites, provide access to space to many satellite developers, and they are attracting interest as an application of space development because development is possible over shorter time period at a lower cost. In most of these nano- and micro-satellite missions, the satellites generally must meet strict attitude requirements for obtaining scientific data under strict constraints of power consumption, space, and weight. In many satellite missions, the jitter of a reaction wheel degrades the performance of the mission detectors and attitude sensors; therefore, jitter should be controlled or isolated to reduce its effect on sensor devices. In conventional standard-sized satellites, tip-tilt mirrors (TTMs) and isolators are used for controlling or isolating the vibrations from reaction wheels; however, it is difficult to use these devices for nano- and micro-satellite missions under the strict power, space, and mass constraints. In this research, the jitter of reaction wheels is reduced by using accurate sensors, small reaction wheels, and slow rotation frequency reaction wheel instead of TTMs and isolators. The objective of a reaction wheel in many satellite missions is the management of the satellite's angular momentum, which increases because of attitude disturbances. If the magnitude of the disturbance is reduced in orbit or on the ground, the magnitude of the angular momentum that the reaction wheels gain from attitude disturbances in orbit becomes smaller; therefore, satellites can stabilize their attitude using only smaller reaction wheels or slow rotation speed, which cause relatively smaller vibration. In nano- and micro-satellite missions, the dominant attitude disturbance is a magnetic torque, which can be cancelled by using magnetic actuators. With the magnetic compensation, the satellite reduces the angular momentum that the reaction wheels gain, and therefore, satellites do

Temporary Blinding Limits versus Maximum Permissible Exposure - A Paradigm Change in Risk Assessment for Visible Optical Radiation

NASA Astrophysics Data System (ADS)

Reidenbach, Hans-Dieter

Safety considerations in the field of laser radiation have traditionally been restricted to maximum permissible exposure levels defined as a function of wavelength and exposure duration. But in Europe according to the European Directive 2006/25/EC on artificial optical radiation the employer has to include in his risk assessment indirect effects from temporary blinding. Whereas sufficient knowledge on various deterministic risks exists, only sparse quantitative data is available for the impairment of visual functions due to temporary blinding from visible optical radiation. The consideration of indirect effects corresponds to a paradigm change in risk assessment when situations have to be treated, where intrabeam viewing of low-power laser radiation is likely or other non-coherent visible radiation might influence certain visual tasks. In order to obtain a sufficient basis for the assessment of certain situations, investigations of the functional relationships between wavelength, exposure time and optical power and the resulting interference on visual functions have been performed and the results are reported. The duration of a visual disturbance is thus predictable. In addition, preliminary information on protective measures is given.

A novel fair active queue management algorithm based on traffic delay jitter

NASA Astrophysics Data System (ADS)

Wang, Xue-Shun; Yu, Shao-Hua; Dai, Jin-You; Luo, Ting

2009-11-01

In order to guarantee the quantity of data traffic delivered in the network, congestion control strategy is adopted. According to the study of many active queue management (AQM) algorithms, this paper proposes a novel active queue management algorithm named JFED. JFED can stabilize queue length at a desirable level by adjusting output traffic rate and adopting a reasonable calculation of packet drop probability based on buffer queue length and traffic jitter; and it support burst packet traffic through the packet delay jitter, so that it can traffic flow medium data. JFED impose effective punishment upon non-responsible flow with a full stateless method. To verify the performance of JFED, it is implemented in NS2 and is compared with RED and CHOKe with respect to different performance metrics. Simulation results show that the proposed JFED algorithm outperforms RED and CHOKe in stabilizing instantaneous queue length and in fairness. It is also shown that JFED enables the link capacity to be fully utilized by stabilizing the queue length at a desirable level, while not incurring excessive packet loss ratio.

Voice Loudness and Gender Effects on Jitter and Shimmer in Healthy Adults

ERIC Educational Resources Information Center

Brockmann, Meike; Storck, Claudio; Carding, Paul N.; Drinnan, Michael J.

2008-01-01

Purpose: The aim of this study was to investigate voice loudness and gender effects on jitter and shimmer in healthy young adults because previous descriptions have been inconsistent. Method: Fifty-seven healthy adults (28 women, 29 men) aged 20-40 years were included in this cross-sectional single-cohort study. Three phonations of /a/ at soft,…

All fiber-coupled, long-term stable timing distribution for free-electron lasers with few-femtosecond jitter

PubMed Central

Şafak, K.; Xin, M.; Callahan, P. T.; Peng, M. Y.; Kärtner, F. X.

2015-01-01

We report recent progress made in a complete fiber-optic, high-precision, long-term stable timing distribution system for synchronization of next generation X-ray free-electron lasers. Timing jitter characterization of the master laser shows less than 170-as RMS integrated jitter for frequencies above 10 kHz, limited by the detection noise floor. Timing stabilization of a 3.5-km polarization-maintaining fiber link is successfully achieved with an RMS drift of 3.3 fs over 200 h of operation using all fiber-coupled elements. This all fiber-optic implementation will greatly reduce the complexity of optical alignment in timing distribution systems and improve the overall mechanical and timing stability of the system. PMID:26798814

Pointing and Jitter Control for the USNA Multi-Beam Combining System

DTIC Science & Technology

2013-05-10

previous work, an adaptive H-infinity optimal controller has been developed to control a single beam using a beam position detector for feedback... turbulence and airborne particles, platform jitter, lack of feedback from the target , and current laser technology represent just a few of these...lasers. Solid state lasers, however, cannot currently provide high enough power levels to destroy a target using a single beam. On solid-state

Low-jitter high-power thyristor array pulse driver and generator

DOEpatents

Hanks, Roy L.

2002-01-01

A method and apparatus for generating low-jitter, high-voltage and high-current pulses for driving low impedance loads such as detonator fuses uses a MOSFET driver which, when triggered, discharges a high-voltage pre-charged capacitor into the primary of a toroidal current-multiplying transformer with multiple isolated secondary windings. The secondary outputs are suitable for driving an array of thyristors that discharge a precharged high-voltage capacitor and thus generating the required high-voltage and high-current pulse.

Jitter-correction for IR/UV-XUV pump-probe experiments at the FLASH free-electron laser

DOE PAGES

Savelyev, Evgeny; Boll, Rebecca; Bomme, Cedric; ...

2017-04-10

In pump-probe experiments employing a free-electron laser (FEL) in combination with a synchronized optical femtosecond laser, the arrival-time jitter between the FEL pulse and the optical laser pulse often severely limits the temporal resolution that can be achieved. Here, we present a pump-probe experiment on the UV-induced dissociation of 2,6-difluoroiodobenzene C 6H 3F 2I) molecules performed at the FLASH FEL that takes advantage of recent upgrades of the FLASH timing and synchronization system to obtain high-quality data that are not limited by the FEL arrival-time jitter. Here, we discuss in detail the necessary data analysis steps and describe the originmore » of the time-dependent effects in the yields and kinetic energies of the fragment ions that we observe in the experiment.« less

G-Jitter Effects in Protein Crystal Growth - A Numerical Study

NASA Technical Reports Server (NTRS)

Ramachandran, N.; Baugher, C. R.

1995-01-01

The impact of spacecraft acceleration environment on Protein Crystal Growth (PCG) is studied. A brief overview of the Space Shuttle acceleration environment is provided followed by a simple scaling procedure used to obtain estimates of the flow and concentration field characteristics in PCG. A detailed two-dimensional numerical model is then used to simulate the PCG system response to different disturbance scenarios; viz. residual g effects, impulse type disturbances and oscillatory inputs. The results show that PCG is susceptible to g-jitter and is a good candidate for vibration isolation.

Femtosecond timing-jitter between photo-cathode laser and ultra-short electron bunches by means of hybrid compression

NASA Astrophysics Data System (ADS)

Pompili, R.; Anania, M. P.; Bellaveglia, M.; Biagioni, A.; Castorina, G.; Chiadroni, E.; Cianchi, A.; Croia, M.; Di Giovenale, D.; Ferrario, M.; Filippi, F.; Gallo, A.; Gatti, G.; Giorgianni, F.; Giribono, A.; Li, W.; Lupi, S.; Mostacci, A.; Petrarca, M.; Piersanti, L.; Di Pirro, G.; Romeo, S.; Scifo, J.; Shpakov, V.; Vaccarezza, C.; Villa, F.

2016-08-01

The generation of ultra-short electron bunches with ultra-low timing-jitter relative to the photo-cathode (PC) laser has been experimentally proved for the first time at the SPARC_LAB test-facility (INFN-LNF, Frascati) exploiting a two-stage hybrid compression scheme. The first stage employs RF-based compression (velocity-bunching), which shortens the bunch and imprints an energy chirp on it. The second stage is performed in a non-isochronous dogleg line, where the compression is completed resulting in a final bunch duration below 90 fs (rms). At the same time, the beam arrival timing-jitter with respect to the PC laser has been measured to be lower than 20 fs (rms). The reported results have been validated with numerical simulations.

Young Nearby Suns and Stellar Jitter Dependence on Age

NASA Astrophysics Data System (ADS)

Cabrera, Nicole; White, Russel; Delfosse, Xavier; Noah Quinn, Samuel; Latham, David W.

2015-01-01

Finding the nearest young planets offers the most direct way to improve our understanding of how planets form, how they migrate, and how they evolve. However, most radial velocity (RV) surveys have avoided young stars because of their problematic characteristics, including high levels of stellar activity. Recent advancements in infrared (IR) detectors as well as wavelength calibration methods have provided new ways of pursuing high-precision RV measurements of young stars. While this work has been successfully applied to many young late-K and M dwarfs, much less RV work has been done on young Sun-like stars, with the very recent exception of adolescent stars (~600 Myr) in open clusters. In order to better understand the dynamical and structural forces that shaped our own Solar system, we must begin to explore the more massive realm of Sun-like stars.We present precision optical radial velocity data of 5 young, nearby, Sun-like stars in AB Dor and assess our ability to detect young planets with current spectroscopic methods. The data were obtained with the TRES spectrograph on the 1.5-m Tillinghast Reflector at the Fred L. Whipple Observatory and with SOPHIE on the 1.95 m Telescope at the Observatoire de Haute Provence. We obtained a RV precision of ~8 m/s with TRES and ~7 m/s precision with SOPHIE; average observed dispersions are 38 m/s and 33 m/s, respectively. We combine our results with spectroscopic data of Sun-like stars spanning a broad range of youthful ages (< 1 Gyr) from the literature to investigate the relationship between stellar jitter and stellar age. The results suggest that the jitter of Sun-like stars decreases below 100 m/s for stars older than ~30 Myr, which would enable the discovery of hot Jupiters orbiting these adolescent age stars.

A simple high-voltage high current spark gap with subnanosecond jitter triggered by femtosecond laser filamentation

NASA Astrophysics Data System (ADS)

Arantchouk, L.; Houard, A.; Brelet, Y.; Carbonnel, J.; Larour, J.; André, Y.-B.; Mysyrowicz, A.

2013-04-01

We describe a simple, sturdy, and reliable spark gap operating with air at atmospheric pressure and able to switch currents in excess of 10 kA with sub-nanosecond jitter. The spark gap is remotely triggered by a femtosecond laser filament.

Reliable jitter and shimmer measurements in voice clinics: the relevance of vowel, gender, vocal intensity, and fundamental frequency effects in a typical clinical task.

PubMed

Brockmann, Meike; Drinnan, Michael J; Storck, Claudio; Carding, Paul N

2011-01-01

The aims of this study were to examine vowel and gender effects on jitter and shimmer in a typical clinical voice task while correcting for the confounding effects of voice sound pressure level (SPL) and fundamental frequency (F(0)). Furthermore the relative effect sizes of vowel, gender, voice SPL, and F(0) were assessed, and recommendations for clinical measurements were derived. With this cross-sectional single cohort study, 57 healthy adults (28 women, 29 men) aged 20-40 years were investigated. Three phonations of /a/, /o/, and /i/ at "normal" voice loudness were analyzed using Praat (software). The effects of vowel, gender, voice SPL, and F(0) on jitter and shimmer were assessed using descriptive and inferential (analysis of covariance) statistics. The effect sizes were determined with the eta-squared statistic. Vowels, gender, voice SPL, and F(0), each had significant effects either on jitter or on shimmer, or both. Voice SPL was the most important factor, whereas vowel, gender, and F(0) effects were comparatively small. Because men had systematically higher voice SPL, the gender effects on jitter and shimmer were smaller when correcting for SPL and F(0). Surprisingly, in clinical assessments, voice SPL has the single biggest impact on jitter and shimmer. Vowel and gender effects were clinically important, whereas fundamental frequency had a relatively small influence. Phonations at a predefined voice SPL (80 dB minimum) and vowel (/a/) would enhance measurement reliability. Furthermore, gender-specific thresholds applying these guidelines should be established. However, the efficiency of these measures should be verified and tested with patients. Copyright © 2011 The Voice Foundation. All rights reserved.

A review on high-resolution CMOS delay lines: towards sub-picosecond jitter performance.

PubMed

Abdulrazzaq, Bilal I; Abdul Halin, Izhal; Kawahito, Shoji; Sidek, Roslina M; Shafie, Suhaidi; Yunus, Nurul Amziah Md

2016-01-01

A review on CMOS delay lines with a focus on the most frequently used techniques for high-resolution delay step is presented. The primary types, specifications, delay circuits, and operating principles are presented. The delay circuits reported in this paper are used for delaying digital inputs and clock signals. The most common analog and digitally-controlled delay elements topologies are presented, focusing on the main delay-tuning strategies. IC variables, namely, process, supply voltage, temperature, and noise sources that affect delay resolution through timing jitter are discussed. The design specifications of these delay elements are also discussed and compared for the common delay line circuits. As a result, the main findings of this paper are highlighting and discussing the followings: the most efficient high-resolution delay line techniques, the trade-off challenge found between CMOS delay lines designed using either analog or digitally-controlled delay elements, the trade-off challenge between delay resolution and delay range and the proposed solutions for this challenge, and how CMOS technology scaling can affect the performance of CMOS delay lines. Moreover, the current trends and efforts used in order to generate output delayed signal with low jitter in the sub-picosecond range are presented.

Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter

NASA Astrophysics Data System (ADS)

Martínez-Arnáiz, R.; Maldonado, J.; Montes, D.; Eiroa, C.; Montesinos, B.

2010-09-01

Context. Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles, and their perturbations alter the line centroids creating a radial velocity jitter that might “contaminate” the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims: We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d ≤ 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e., Ca ii H & K lines, to others that hold noteworthy advantages. Methods: We used high resolution (~50 000) echelle optical spectra. Standard data reduction was performed using the IRAF echelle package. To determine the chromospheric emission of the stars in the sample, we used the spectral subtraction technique. We measured the equivalent widths of the chromospheric emission lines in the subtracted spectrum and transformed them into fluxes by applying empirical equivalent width and flux relationships. Rotational velocities were determined using the cross-correlation technique. To infer activity-related radial velocity (RV) jitter, we used empirical relationships between this jitter and the R'_HK index. Results: We measured chromospheric activity, as given by different indicators throughout the optical spectra, and projected rotational velocities for 371 nearby cool stars. We have built empirical relationships among the most important chromospheric emission lines. Finally, we used the measured chromospheric activity

a Novel Technique for Precision Geometric Correction of Jitter Distortion for the Europa Imaging System and Other Rolling-Shutter Cameras

NASA Astrophysics Data System (ADS)

Kirk, R. L.; Shepherd, M.; Sides, S. C.

2018-04-01

We use simulated images to demonstrate a novel technique for mitigating geometric distortions caused by platform motion ("jitter") as two-dimensional image sensors are exposed and read out line by line ("rolling shutter"). The results indicate that the Europa Imaging System (EIS) on NASA's Europa Clipper can likely meet its scientific goals requiring 0.1-pixel precision. We are therefore adapting the software used to demonstrate and test rolling shutter jitter correction to become part of the standard processing pipeline for EIS. The correction method will also apply to other rolling-shutter cameras, provided they have the operational flexibility to read out selected "check lines" at chosen times during the systematic readout of the frame area.

Detecting Motion from a Moving Platform; Phase 2: Lightweight, Low Power Robust Means of Removing Image Jitter

DTIC Science & Technology

2011-11-01

common housefly , Musca domestica. “Lightweight, Low Power Robust Means of Removing Image Jitter,” (AFRL-RX-TY-TR-2011-0096-02) develops an optimal...biological vision system of the common housefly , Musca domestica. Several variations of this sensor were designed, simulated extensively, and hardware

Practical application of cross correlation technique to measure jitter of master-oscillator-power-amplifier laser system

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

Młyńczak, J.; Sawicz-Kryniger, K.; Fry, A. R.

2014-01-01

The Linac coherent light source (LCLS) at the SLAC National Accelerator Laboratory (SLAC) is the world’s first hard X-ray free electron laser (XFEL) and is capable of producing high-energy, femtosecond duration X-ray pulses. A common technique to study fast timescale physical phenomena, various “pump/probe” techniques are used. In these techniques there are two lasers, one optical and one X-ray, that work as a pump and as a probe to study dynamic processes in atoms and molecules. In order to resolve phenomena that occur on femtosecond timescales, it is imperative to have very precise timing between the optical lasers and X-raysmore » (on the order of ~ 20 fs or better). The lasers are synchronized to the same RF source that drives the accelerator and produces the X-ray laser. However, elements in the lasers cause some drift and time jitter, thereby de-synchronizing the system. This paper considers cross-correlation technique as a way to quantify the drift and jitter caused by the regenerative amplifier of the ultrafast optical laser.« less

Particle Acceleration and Radiation associated with Magnetic Field Generation from Relativistic Collisionless Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, K.; Hardee, P. E.; Richardson, G. A.; Preece, R. D.; Sol, H.; Fishman, G. J.

2003-01-01

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. While some Fermi acceleration may occur at the jet front, the majority of electron acceleration takes place behind the jet front and cannot be characterized as Fermi acceleration. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron s transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

The measurement of solute diffusion coefficients in dilute liquid alloys: the influence of unit gravity and g-jitter on buoyancy convection.

PubMed

Smith, R W; Yang, B J; Huang, W D

2004-11-01

Liquid diffusion experiments conducted on the MIR space station using the Canadian Space Agency QUELD II processing facility and the microgravity isolation mount (MIM) showed that g-jitter significantly increased the measured solute diffusion coefficients. In some experiments, milli-g forced vibration was superimposed on the sample when isolated from the ambient g-jitter; this resulted in markedly increased solute transport. To further explore the effects arising in these long capillary diffusion couples from the absence of unit-gravity and the presence of the forced g-jitter, the effects of a 1 milli-g forcing vibration on the mass transport in a 1.5 mm diameter long capillary diffusion couple have been simulated. In addition, to increase understanding of the role of unit gravity in determining the extent to which gravity can influence measured diffusion coefficient values, comparative experiments involving gold, silver, and antimony diffusing in liquid lead have been carried out using a similar QUELD II facility to that employed in the QUELD II/MIM/MIR campaign but under terrestrial conditions. It was found that buoyancy-driven convection may still persist in the liquid even when conditions are arranged for a continuously decreasing density gradient up the axis of a vertical long capillary diffusion couple due to the presence of small radial temperature gradients.

Design of a Sub-Picosecond Jitter with Adjustable-Range CMOS Delay-Locked Loop for High-Speed and Low-Power Applications

PubMed Central

Abdulrazzaq, Bilal I.; Ibrahim, Omar J.; Kawahito, Shoji; Sidek, Roslina M.; Shafie, Suhaidi; Yunus, Nurul Amziah Md.; Lee, Lini; Halin, Izhal Abdul

2016-01-01

A Delay-Locked Loop (DLL) with a modified charge pump circuit is proposed for generating high-resolution linear delay steps with sub-picosecond jitter performance and adjustable delay range. The small-signal model of the modified charge pump circuit is analyzed to bring forth the relationship between the DLL’s internal control voltage and output time delay. Circuit post-layout simulation shows that a 0.97 ps delay step within a 69 ps delay range with 0.26 ps Root-Mean Square (RMS) jitter performance is achievable using a standard 0.13 µm Complementary Metal-Oxide Semiconductor (CMOS) process. The post-layout simulation results show that the power consumption of the proposed DLL architecture’s circuit is 0.1 mW when the DLL is operated at 2 GHz. PMID:27690040

Few-femtosecond-resolution characterization and suppression of excess timing jitter and drift in indoor atmospheric frequency comb transfer.

PubMed

Kang, Jinho; Shin, Junho; Kim, Chur; Jung, Kwangyun; Park, Suhyeon; Kim, Jungwon

2014-10-20

We characterize the timing jitter spectral density of the time-of-flight (TOF) in the indoor atmospheric transfer of optical pulse train over 10 decades of Fourier frequency range (10 μHz - 100 kHz) with sub-100-as resolution using a balanced optical cross-correlator (BOC). Based on the well-known theory for atmospheric transfer of a laser beam, we could fit the measured timing jitter power spectral density to the theory and analyze it with a fairly good agreement from 20 mHz to 10 Hz Fourier frequency range. Moreover, we demonstrate that the BOC-based timing stabilization method can suppress the excess fluctuations in timing from >200 fs (rms) to 2.6 fs (rms) maintained over 130 hours when an optical pulse train is transferred over a 76.2-m long free-space beam path in laboratory environment. The demonstrated stabilization result corresponds to 4 × 10(-20) overlapping Allan deviation at 117,000 s averaging time.

Agile Blocker and Clock Jitter Tolerant Low-Power Frequency Selective Receiver with Energy Harvesting Capability.

PubMed

Hasan, Abul; Helaoui, Mohamed; Ghannouchi, Fadhel M

2017-08-29

In this article, a novel tunable, blocker and clock jitter tolerant, low power, quadrature phase shift frequency selective (QPS-FS) receiver with energy harvesting capability is proposed. The receiver's design embraces and integrates (i) the baseband to radio frequency (RF) impedance translation concept to improve selectivity over that of conventional homodyne receiver topologies and (ii) broadband quadrature phase shift circuitry in the RF path to remove an active multi-phase clock generation circuit in passive mixer (PM) receivers. The use of a single local oscillator clock signal with a passive clock division network improves the receiver's robustness against clock jitter and reduces the source clock frequency by a factor of N, compared to PM receivers using N switches (N≥4). As a consequence, the frequency coverage of the QPS-FS receiver is improved by a factor of N, given a clock source of maximum frequency; and, the power consumption of the whole receiver system can eventually be reduced. The tunable QPS-FS receiver separates the wanted RF band signal from the unwanted blockers/interferers. The desired RF signal is frequency down-converted to baseband, while the undesired blocker/interferer signals are reflected by the receiver, collected and could be energy recycled using an auxiliary energy harvesting device.

Effect of signal jitter on the spectrum of rotor impulsive noise

NASA Technical Reports Server (NTRS)

Brooks, Thomas F.

1987-01-01

The effect of randomness or jitter of the acoustic waveform on the spectrum of rotor impulsive noise is studied because of its importance for data interpretation. An acoustic waveform train is modelled representing rotor impulsive noise. The amplitude, shape, and period between occurrences of individual pulses are allowed to be randomized assuming normal probability distributions. Results, in terms of the standard deviations of the variable quantities, are given for the autospectrum as well as special processed spectra designed to separate harmonic and broadband rotor noise components. Consideration is given to the effect of accuracy in triggering or keying to a rotor one per revolution signal. An example is given showing the resultant spectral smearing at the high frequencies due to the pulse signal period variability.

Effect of signal jitter on the spectrum of rotor impulsive noise

NASA Technical Reports Server (NTRS)

Brooks, Thomas F.

1988-01-01

The effect of randomness or jitter of the acoustic waveform on the spectrum of rotor impulsive noise is studied because of its importance for data interpretation. An acoustic waveform train is modeled representing rotor impulsive noise. The amplitude, shape, and period between occurrences of individual pulses are allowed to be randomized assuming normal probability distributions. Results, in terms of the standard deviations of the variable quantities, are given for the autospectrum as well as special processed spectra designed to separate harmonic and broadband rotor noise components. Consideration is given to the effect of accuracy in triggering or keying to a rotor one per revolution signal. An example is given showing the resultant spectral smearing at the high frequencies due to the pulse signal period variability.

Dynamic/Jitter Assessment of Multiple Potential HabEx Structural Designs

NASA Technical Reports Server (NTRS)

Knight, J. Brent; Stahl, H. Philip; Singleton, Andy; Hunt, Ron; Therrell, Melissa; Caldwell, Kate; Garcia, Jay; Baysinger, Mike

2017-01-01

One of the driving structural requirements of the Habitable Exo-Planet (HabEx) telescope is to maintain Line Of Sight (LOS) stability between the Primary Mirror (PM) and Secondary Mirror (SM) of = 5 mas. Dynamic analyses of two configurations of a proposed (HabEx) 4 meter off-axis telescope structure were performed to predict effects of jitter on primary/secondary mirror alignment. The dynamic disturbance used as the forcing function was the James Webb Space Telescope reaction wheel assembly vibration emission specification level. The objective of these analyses was to predict "order-of-magnitude" performance for various structural configurations which will roll into efforts to define the HabEx structural design's global architecture. Two variations of the basic architectural design were analyzed. Relative motion between the PM and the SM for each design configuration are reported.

A new Gamma Knife radiosurgery paradigm: Tomosurgery

NASA Astrophysics Data System (ADS)

Hu, Xiaoliang

The Leksell (Elekta, Stockholm, Sweden) Gamma Knife(TM) (LGK) is the worldwide standard-of-care for the radiosurgical treatment of a wide variety of intracranial lesions. The current LGK utilizes a step-and-shoot dose delivery mechanism where the centroid of each conformal radiation dose (i.e., the shot isocenter) requires repositioning the patient outside of the irradiation field. Perhaps the greatest challenge the LGK treatment team faces is planning the treatment of large and/or complexly shaped lesions that may be in close proximity to critical neural or vascular structures. The standard manual treatment planning approach is a time consuming procedure where additional time spent does not guarantee the identification of an increasingly optimal treatment plan. I propose a new radiosurgery paradigm which I refer to as "Tomosurgery". The Tomosurgery paradigm begins with the division of the target volume into a series of adjacent treatment slices, each with a carefully determined optimal thickness. The use of a continuously moving disk-shaped radiation shot that moves through the lesion in a raster-scanning pattern is expected to improve overall radiation dose conformality and homogeneity. The Tomosurgery treatment planning algorithm recruits a two-stage optimization strategy, which first plans each treatment slice as a simplified 2D problem and secondly optimally assembles the 2D treatment plans into the final 3D treatment plan. Tested on 11 clinical LGK cases, the automated inversely-generated Tomosurgery treatment plans performed as well or better than the neurosurgeon's manually created treatment plans across all criteria: (a) dose volume histograms, (b) dose homogeneity, (c) dose conformality, and (d) critical structure damage, where applicable. LGK Tomosurgery inverse treatment planning required much less time than standard of care, manual (i.e., forward) LGK treatment planning procedures. These results suggest that Tomosurgery might provide an improvement

GNSS software receiver sampling noise and clock jitter performance and impact analysis

NASA Astrophysics Data System (ADS)

Chen, Jian Yun; Feng, XuZhe; Li, XianBin; Wu, GuangYao

2015-02-01

In the design of a multi-frequency multi-constellation GNSS software defined radio receivers is becoming more and more popular due to its simple architecture, flexible configuration and good coherence in multi-frequency signal processing. It plays an important role in navigation signal processing and signal quality monitoring. In particular, GNSS software defined radio receivers driving the sampling clock of analogue-to-digital converter (ADC) by FPGA implies that a more flexible radio transceiver design is possible. According to the concept of software defined radio (SDR), the ideal is to digitize as close to the antenna as possible. Whereas the carrier frequency of GNSS signal is of the frequency of GHz, converting at this frequency is expensive and consumes more power. Band sampling method is a cheaper, more effective alternative. When using band sampling method, it is possible to sample a RF signal at twice the bandwidth of the signal. Unfortunately, as the other side of the coin, the introduction of SDR concept and band sampling method induce negative influence on the performance of the GNSS receivers. ADC's suffer larger sampling clock jitter generated by FPGA; and low sampling frequency introduces more noise to the receiver. Then the influence of sampling noise cannot be neglected. The paper analyzes the sampling noise, presents its influence on the carrier noise ratio, and derives the ranging error by calculating the synchronization error of the delay locked loop. Simulations aiming at each impact factors of sampling-noise-induced ranging error are performed. Simulation and experiment results show that if the target ranging accuracy is at the level of centimeter, the quantization length should be no less than 8 and the sampling clock jitter should not exceed 30ps.

Electro-Optic Time-to-Space Converter for Optical Detector Jitter Mitigation

NASA Technical Reports Server (NTRS)

Birnbaum, Kevin; Farr, William

2013-01-01

A common problem in optical detection is determining the arrival time of a weak optical pulse that may comprise only one to a few photons. Currently, this problem is solved by using a photodetector to convert the optical signal to an electronic signal. The timing of the electrical signal is used to infer the timing of the optical pulse, but error is introduced by random delay between the absorption of the optical pulse and the creation of the electrical one. To eliminate this error, a time-to-space converter separates a sequence of optical pulses and sends them to different photodetectors, depending on their arrival time. The random delay, called jitter, is at least 20 picoseconds for the best detectors capable of detecting the weakest optical pulses, a single photon, and can be as great as 500 picoseconds. This limits the resolution with which the timing of the optical pulse can be measured. The time-to-space converter overcomes this limitation. Generally, the time-to-space converter imparts a time-dependent momentum shift to the incoming optical pulses, followed by an optical system that separates photons of different momenta. As an example, an electro-optic phase modulator can be used to apply longitudinal momentum changes (frequency changes) that vary in time, followed by an optical spectrometer (such as a diffraction grating), which separates photons with different momenta into different paths and directs them to impinge upon an array of photodetectors. The pulse arrival time is then inferred by measuring which photodetector receives the pulse. The use of a time-to-space converter mitigates detector jitter and improves the resolution with which the timing of an optical pulse is determined. Also, the application of the converter enables the demodulation of a pulse position modulated signal (PPM) at higher bandwidths than using previous photodetector technology. This allows the creation of a receiver for a communication system with high bandwidth and high bits

Picosecond 1064-nm fiber laser with tunable pulse width and low timing jitter

NASA Astrophysics Data System (ADS)

Tian, Wenyan; Zhang, Shukui

2018-02-01

We report an all-fiber, linearly polarized, 1.1-W, 1064-nm fiber laser based on a two-stage Ytterbium-doped fiber amplifier seeded by a gain-switched diode laser with tunable pulse width from 21 to 200 ps at repetition rates of 0.5-1.5 GHz. Timing jitter of our 1064-nm fiber laser was measured to be 0.60 ps over 10 Hz-40 MHz when the gain-switched diode laser was operated at a repetition rate of 0.5, 1, and 1.5 GHz. The fiber laser offers an excellent long term power stability of +/- 0.3% and wavelength stability of +/- 0.01 nm over 8 hours

Carrier-envelope phase stabilization with sub-10 as residual timing jitter.

PubMed

Borchers, B; Koke, S; Husakou, A; Herrmann, J; Steinmeyer, G

2011-11-01

We demonstrate carrier-envelope phase (CEP) stabilization of a mode-locked Ti:sapphire oscillator with unprecedented timing jitter of eight attoseconds. The stabilization performance is obtained by a combination of two different stabilization approaches. In a first step the drift of the CEP is stabilized with a conventional feedback loop by means of controlling the oscillator pump power with an acousto-optic modulator (AOM). In a second step we utilize a recently developed feed-forward type stabilization scheme which has a much higher control bandwith. Here an acousto-optic frequency shifter (AOFS) produces the stabilized output in the first diffraction order. Moreover, we present numerical results on the optimization of the length of the photonic crystal fiber, which is used to generate an octave-spanning spectrum, in order to optimize the sensitivity in the f-to-2f interferometers.

Instantaneous speed jitter detection via encoder signal and its application for the diagnosis of planetary gearbox

NASA Astrophysics Data System (ADS)

Zhao, Ming; Jia, Xiaodong; Lin, Jing; Lei, Yaguo; Lee, Jay

2018-01-01

In modern rotating machinery, rotary encoders have been widely used for the purpose of positioning and dynamic control. The study in this paper indicates that, the encoder signal, after proper processing, can be also effectively used for the health monitoring of rotating machines. In this work, a Kurtosis-guided local polynomial differentiator (KLPD) is proposed to estimate the instantaneous angular speed (IAS) of rotating machines based on the encoder signal. Compared with the central difference method, the KLPD is more robust to noise and it is able to precisely capture the weak speed jitters introduced by mechanical defects. The fault diagnosis of planetary gearbox has proven to be a challenging issue in both industry and academia. Based on the proposed KLPD, a systematic method for the fault diagnosis of planetary gearbox is proposed. In this method, residual time synchronous time averaging (RTSA) is first employed to remove the operation-related IAS components that come from normal gear meshing and non-stationary load variations, KLPD is then utilized to detect and enhance the speed jitter from the IAS residual in a data-driven manner. The effectiveness of proposed method has been validated by both simulated data and experimental data. The results demonstrate that the proposed KLPD-RTSA could not only detect fault signatures but also identify defective components, thus providing a promising tool for the health monitoring of planetary gearbox.

HAT-P-32b AND HAT-P-33b: TWO HIGHLY INFLATED HOT JUPITERS TRANSITING HIGH-JITTER STARS

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

Hartman, J. D.; Bakos, G. A.; Torres, G.

2011-11-20

We report the discovery of two exoplanets transiting high-jitter stars. HAT-P-32b orbits the bright V = 11.289 late-F-early-G dwarf star GSC 3281-00800, with a period P = 2.150008 {+-} 0.000001 d. The stellar and planetary masses and radii depend on the eccentricity of the system, which is poorly constrained due to the high-velocity jitter ({approx}80 m s{sup -1}). Assuming a circular orbit, the star has a mass of 1.16 {+-} 0.04 M{sub Sun} and radius of 1.22 {+-} 0.02 R{sub Sun }, while the planet has a mass of 0.860 {+-} 0.164 M{sub J} and a radius of 1.789 {+-}more » 0.025 R{sub J}. The second planet, HAT-P-33b, orbits the bright V = 11.188 late-F dwarf star GSC 2461-00988, with a period P = 3.474474 {+-} 0.000001 d. As for HAT-P-32, the stellar and planetary masses and radii of HAT-P-33 depend on the eccentricity, which is poorly constrained due to the high jitter ({approx}50 m s{sup -1}). In this case, spectral line bisector spans (BSs) are significantly anti-correlated with the radial velocity residuals, and we are able to use this correlation to reduce the residual rms to {approx}35 m s{sup -1}. We find that the star has a mass of 1.38 {+-} 0.04 M{sub Sun} and a radius of 1.64 {+-} 0.03 R{sub Sun} while the planet has a mass of 0.762 {+-} 0.101 M{sub J} and a radius of 1.686 {+-} 0.045 R{sub J} for an assumed circular orbit. Due to the large BS variations exhibited by both stars we rely on detailed modeling of the photometric light curves to rule out blend scenarios. Both planets are among the largest radii transiting planets discovered to date.« less

Inside-in, alternative paradigms for sound spatialization

NASA Astrophysics Data System (ADS)

Bahn, Curtis; Moore, Stephan

2003-04-01

Arrays of widely spaced mono-directional loudspeakers (P.A.-style stereo configurations or ``outside-in'' surround-sound systems) have long provided the dominant paradigms for electronic sound diffusion. So prevalent are these models that alternatives have largely been ignored and electronic sound, regardless of musical aesthetic, has come to be inseparably associated with single-channel speakers, or headphones. We recognize the value of these familiar paradigms, but believe that electronic sound can and should have many alternative, idiosyncratic voices. Through the design and construction of unique sound diffusion structures, one can reinvent the nature of electronic sound; when allied with new sensor technologies, these structures offer alternative modes of interaction with techniques of sonic computation. This paper describes several recent applications of spherical speakers (multichannel, outward-radiating geodesic speaker arrays) and Sensor-Speaker-Arrays (SenSAs: combinations of various sensor devices with outward-radiating multi-channel speaker arrays). This presentation introduces the development of four generations of spherical speakers-over a hundred individual speakers of various configurations-and their use in many different musical situations including live performance, recording, and sound installation. We describe the design and construction of these systems, and, more generally, the new ``voices'' they give to electronic sound.

Improving carrier-envelope phase stability in optical parametric chirped-pulse amplifiers by control of timing jitter.

PubMed

Hädrich, S; Rothhardt, J; Krebs, M; Demmler, S; Limpert, J; Tünnermann, A

2012-12-01

It is shown that timing jitter in optical parametric chirped-pulse amplification induces spectral drifts that transfer to carrier-envelope phase (CEP) instabilities via dispersion. Reduction of this effect requires temporal synchronization, which is realized with feedback obtained from the angularly dispersed idler. Furthermore, a novel method to measure the CEP drifts by utilizing parasitic second harmonic generation within parametric amplifiers is presented. Stabilization of the timing allows the obtainment of a CEP stability of 86 mrad over 40 min at 150 kHz repetition rate.

The identification of credit card encoders by hierarchical cluster analysis of the jitters of magnetic stripes.

PubMed

Leung, S C; Fung, W K; Wong, K H

1999-01-01

The relative bit density variation graphs of 207 specimen credit cards processed by 12 encoding machines were examined first visually, and then classified by means of hierarchical cluster analysis. Twenty-nine credit cards being treated as 'questioned' samples were tested by way of cluster analysis against 'controls' derived from known encoders. It was found that hierarchical cluster analysis provided a high accuracy of identification with all 29 'questioned' samples classified correctly. On the other hand, although visual comparison of jitter graphs was less discriminating, it was nevertheless capable of giving a reasonably accurate result.

Detecting vocal fatigue in student singers using acoustic measures of mean fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio

NASA Astrophysics Data System (ADS)

Sisakun, Siphan

2000-12-01

The purpose of this study is to explore the ability of four acoustic parameters, mean fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio, to detect vocal fatigue in student singers. The participants are 15 voice students, who perform two distinct tasks, data collection task and vocal fatiguing task. The data collection task includes the sustained vowel /a/, reading a standard passage, and self-rate on a vocal fatigue form. The vocal fatiguing task is the vocal practice of musical scores for a total of 45 minutes. The four acoustic parameters are extracted using the software EZVoicePlus. The data analyses are performed to answer eight research questions. The first four questions relate to correlations of the self-rating scale and each of the four parameters. The next four research questions relate to differences in the parameters over time using one-factor repeated measures analysis of variance (ANOVA). The result yields a proposed acoustic profile of vocal fatigue in student singers. This profile is characterized by increased fundamental frequency; slightly decreased jitter; slightly decreased shimmer; and slightly increased harmonics-to-noise ratio. The proposed profile requires further investigation.

Asymmetric dual-loop feedback to suppress spurious tones and reduce timing jitter in self-mode-locked quantum-dash lasers emitting at 155 μm

NASA Astrophysics Data System (ADS)

Asghar, Haroon; McInerney, John G.

2017-09-01

We demonstrate an asymmetric dual-loop feedback scheme to suppress external cavity side-modes induced in self-mode-locked quantum-dash lasers with conventional single and dual-loop feedback. In this letter, we achieved optimal suppression of spurious tones by optimizing the length of second delay time. We observed that asymmetric dual-loop feedback, with large (~8x) disparity in cavity lengths, eliminates all external-cavity side-modes and produces flat RF spectra close to the main peak with low timing jitter compared to single-loop feedback. Significant reduction in RF linewidth and reduced timing jitter was also observed as a function of increased second feedback delay time. The experimental results based on this feedback configuration validate predictions of recently published numerical simulations. This interesting asymmetric dual-loop feedback scheme provides simplest, efficient and cost effective stabilization of side-band free optoelectronic oscillators based on mode-locked lasers.

Problems in Microgravity Fluid Mechanics: G-Jitter Convection

NASA Technical Reports Server (NTRS)

Homsy, G. M.

2005-01-01

This is the final report on our NASA grant, Problems in Microgravity Fluid Mechanics NAG3-2513: 12/14/2000 - 11/30/2003, extended through 11/30/2004. This grant was made to Stanford University and then transferred to the University of California at Santa Barbara when the PI relocated there in January 2001. Our main activity has been to conduct both experimental and theoretical studies of instabilities in fluids that are relevant to the microgravity environment, i.e. those that do not involve the action of buoyancy due to a steady gravitational field. Full details of the work accomplished under this grant are given below. Our work has focused on: (i) Theoretical and computational studies of the effect of g-jitter on instabilities of convective states where the convection is driven by forces other than buoyancy (ii) Experimental studies of instabilities during displacements of miscible fluid pairs in tubes, with a focus on the degree to which these mimic those found in immiscible fluids. (iii) Theoretical and experimental studies of the effect of time dependent electrohydrodynamic forces on chaotic advection in drops immersed in a second dielectric liquid. Our objectives are to acquire insight and understanding into microgravity fluid mechanics problems that bear on either fundamental issues or applications in fluid physics. We are interested in the response of fluids to either a fluctuating acceleration environment or to forces other than gravity that cause fluid mixing and convection. We have been active in several general areas.

Revisiting the radiative vertical velocity paradigm in the TTL

NASA Astrophysics Data System (ADS)

Bolot, Maximilien; Moyer, Elisabeth

2015-04-01

We demonstrate that uplift rates in the TTL (tropical tropopause layer) may be commonly overestimated. The mass balance of any tracer in the TTL depends on the vertical speed of large-scale uplift and the rate of convective detrainment from overshoots. Generally, uplift velocity is retrieved from the conservation of energy, assuming that the only significant factor is radiative heating.1,2 The detrainment rate is then computed from the convergence of the uplift flux, with the assumption that detrainment dominates over entrainment in the TTL. We show that this commonly calculated 'radiative vertical velocity' and the associated rate of detrainment are necessarily flawed for either of two mutually exclusive reasons. If radiative heating is the sole diabatic term in the energy budget, then significant convective entrainment must occur at TTL levels. If detrainment dominates over entrainment, then the heat budget must include the cooling rate from the export of sensible heat deficit in overshooting convection. We illustrate the calculations using tropical values of radiative heating rates and large-scale divergence fluxes from ERA-Interim reanalysis. For undilute convection, the export of heat deficit in detrained overshoots would substantially offset radiative heating, lowering the resulting assumed vertical velocity at 16 km by a factor of three. The computed detrainment rate at this altitude also increases significantly, by a factor of five. Because these changes would alter interpretation of tracer profiles, it is important to include all terms in the heat budget in tracer studies. Conversely, tracer transport properties can be used to help constrain the impact of convection on the TTL heat budget.3 [1] Folkins, I. et al., J. Geophys. Res., 111, D23304, (2006). [2] Read, W. G. et al., Atmos. Chem. Phys., 8, 6051-6067, (2008). [3] Kuang, Z. and Bretherton, C. S., J. Atmos. Sci., 61, 2919-2927, (2004)

Clarifying the Narrative Paradigm.

ERIC Educational Resources Information Center

Fisher, Walter R.

1989-01-01

Replies to Rowland's article (same issue) on Fisher's views of the narrative paradigm. Clarifies the narrative paradigm by discussing three senses in which "narration" can be understood, and by indicating what the narrative paradigm is not. (SR)

A New Paradigm for Diagnosing Contributions to Model Aerosol Forcing Error

NASA Astrophysics Data System (ADS)

Jones, A. L.; Feldman, D. R.; Freidenreich, S.; Paynter, D.; Ramaswamy, V.; Collins, W. D.; Pincus, R.

2017-12-01

A new paradigm in benchmark absorption-scattering radiative transfer is presented that enables both the globally averaged and spatially resolved testing of climate model radiation parameterizations in order to uncover persistent sources of biases in the aerosol instantaneous radiative effect (IRE). A proof of concept is demonstrated with the Geophysical Fluid Dynamics Laboratory AM4 and Community Earth System Model 1.2.2 climate models. Instead of prescribing atmospheric conditions and aerosols, as in prior intercomparisons, native snapshots of the atmospheric state and aerosol optical properties from the participating models are used as inputs to an accurate radiation solver to uncover model-relevant biases. These diagnostic results show that the models' aerosol IRE bias is of the same magnitude as the persistent range cited ( 1 W/m2) and also varies spatially and with intrinsic aerosol optical properties. The findings underscore the significance of native model error analysis and its dispositive ability to diagnose global biases, confirming its fundamental value for the Radiative Forcing Model Intercomparison Project.

Effects of vibration (G-jitters) on convection in micro-gravity

NASA Technical Reports Server (NTRS)

Wang, Francis C.

1994-01-01

To obtain high quality crystals, it is desirable to maintain a diffusion-limited transport process in a planar solidification surface between the solid and the melt during the crystal growth process. Due to the presence of buoyancy-driven convection, however, this situation is difficult to maintain on Earth. The microgravity environment of an orbiting space laboratory presents an alternative worth pursuing. With reduced gravity, convections very much suppressed in a space laboratory, making the environment more conducive for growing crystals with better quality. However, a space laboratory is not immune from any undesirable disturbances. Nonuniform and transient accelerations such as vibrations, g-jitters, and impulsive accelerations exist as a result of crew activities, space maneuvering, and the operations of on-board equipment. Measurements conducted on-board a U.S. Spacelab mission showed the existence of vibrations in the frequency range of 1 to 100 Hz. It was reported that a dominant mode of 17 Hz and harmonics of 54 Hz were observed and these were attributed to antenna operations. The vibration is not limited to any single plane but exists in all directions. Some data from the Russian MIR space station indicates the existence of vibration also at this frequency range.

Emergence of life: Physical chemistry changes the paradigm.

PubMed

Spitzer, Jan; Pielak, Gary J; Poolman, Bert

2015-06-10

Origin of life research has been slow to advance not only because of its complex evolutionary nature (Franklin Harold: In Search of Cell History, 2014) but also because of the lack of agreement on fundamental concepts, including the question of 'what is life?'. To re-energize the research and define a new experimental paradigm, we advance four premises to better understand the physicochemical complexities of life's emergence: (1) Chemical and Darwinian (biological) evolutions are distinct, but become continuous with the appearance of heredity. (2) Earth's chemical evolution is driven by energies of cycling (diurnal) disequilibria and by energies of hydrothermal vents. (3) Earth's overall chemical complexity must be high at the origin of life for a subset of (complex) chemicals to phase separate and evolve into living states. (4) Macromolecular crowding in aqueous electrolytes under confined conditions enables evolution of molecular recognition and cellular self-organization. We discuss these premises in relation to current 'constructive' (non-evolutionary) paradigm of origins research - the process of complexification of chemical matter 'from the simple to the complex'. This paradigm artificially avoids planetary chemical complexity and the natural tendency of molecular compositions toward maximum disorder embodied in the second law of thermodynamics. Our four premises suggest an empirical program of experiments involving complex chemical compositions under cycling gradients of temperature, water activity and electromagnetic radiation.

Cranial Stereotactic Radiosurgery: Current Status of the Initial Paradigm Shifter

PubMed Central

Sheehan, Jason P.; Yen, Chun-Po; Lee, Cheng-Chia; Loeffler, Jay S.

2014-01-01

The concept of stereotactic radiosurgery (SRS) was first described by Lars Leksell in 1951. It was proposed as a noninvasive alternative to open neurosurgical approaches to manage a variety of conditions. In the following decades, SRS emerged as a unique discipline involving a collegial partnership among neurosurgeons, radiation oncologists, and medical physicists. SRS relies on the precisely guided delivery of high-dose ionizing radiation to an intracranial target. The focused convergence of multiple beams yields a potent therapeutic effect on the target and a steep dose fall-off to surrounding structures, thereby minimizing the risk of collateral damage. SRS is typically administered in a single session but can be given in as many as five sessions or fractions. By providing an ablative effect noninvasively, SRS has altered the treatment paradigms for benign and malignant intracranial tumors, functional disorders, and vascular malformations. Literature on extensive intracranial radiosurgery has unequivocally demonstrated the favorable benefit-to-risk profile that SRS affords for appropriately selected patients. In a departure from conventional radiotherapeutic strategies, radiosurgical principles have recently been extended to extracranial indications such as lung, spine, and liver tumors. The paradigm shift resulting from radiosurgery continues to alter the landscape of related fields. PMID:25113762

Cranial stereotactic radiosurgery: current status of the initial paradigm shifter.

PubMed

Sheehan, Jason P; Yen, Chun-Po; Lee, Cheng-Chia; Loeffler, Jay S

2014-09-10

The concept of stereotactic radiosurgery (SRS) was first described by Lars Leksell in 1951. It was proposed as a noninvasive alternative to open neurosurgical approaches to manage a variety of conditions. In the following decades, SRS emerged as a unique discipline involving a collegial partnership among neurosurgeons, radiation oncologists, and medical physicists. SRS relies on the precisely guided delivery of high-dose ionizing radiation to an intracranial target. The focused convergence of multiple beams yields a potent therapeutic effect on the target and a steep dose fall-off to surrounding structures, thereby minimizing the risk of collateral damage. SRS is typically administered in a single session but can be given in as many as five sessions or fractions. By providing an ablative effect noninvasively, SRS has altered the treatment paradigms for benign and malignant intracranial tumors, functional disorders, and vascular malformations. Literature on extensive intracranial radiosurgery has unequivocally demonstrated the favorable benefit-to-risk profile that SRS affords for appropriately selected patients. In a departure from conventional radiotherapeutic strategies, radiosurgical principles have recently been extended to extracranial indications such as lung, spine, and liver tumors. The paradigm shift resulting from radiosurgery continues to alter the landscape of related fields. © 2014 by American Society of Clinical Oncology.

Organizational Paradigm Shifts.

ERIC Educational Resources Information Center

National Association of College and University Business Officers, Washington, DC.

This collection of essays explores a new paradigm of higher education. The first essay, "Beyond Re-engineering: Changing the Organizational Paradigm" (L. Edwin Coate), suggests a model of quality process management and a structure for managing organizational change. "Thinking About Consortia" (Mary Jo Maydew) discusses…

An Integrative Paradigm

ERIC Educational Resources Information Center

Hammack, Phillip L.

2005-01-01

Through the application of life course theory to the study of sexual orientation, this paper specifies a new paradigm for research on human sexual orientation that seeks to reconcile divisions among biological, social science, and humanistic paradigms. Recognizing the historical, social, and cultural relativity of human development, this paradigm…

Managing piezoelectric sensor jitter: kinematic position tracking applications

NASA Astrophysics Data System (ADS)

Khomo, Malome T.

2016-02-01

Piezo-acoustic distance tracking sensors have challenges of reporting true distance readings. Challenges include directional anisotropy signal loss in transmission power and in receiver sensitivity, distance-related attenuation of signal and the phase shifts that result in jittery values, some preceding, and others succeeding the expected distance readings. There also exist signal time losses arising from dead time associated with processor latency, with carrier signal pulse length and with voltage rise-time delays in pulse detection. Together these factors cause distance under-reporting, and more critically, makes each reported value uncertain, which is unacceptable in distance-critical applications. Piezo-inertial accelerometers have equivalent if not more severe challenges in tri-axial configurations, for instance where a rotational tilt may happen under linear accelerative force. In the absence of tensor component adaptation to change of orientation, signal is lost until the next axial sensor detects it. Study paper focusses on piezo-acoustic transducers UCD1007 and 400SR160 (40kHz), used in a face-to-face configuration over a 600mm range. Within that range 10 successive phase shift wave fronts were identified, but it took 15 reconstructed wave fronts to uniquely identify a continuous end-to-end jitter-free and slippage-free kinematic data stream from the jittery sensor data. The additional 5 degrees of freedom were consumed by the 5-stage filter applied. The technique has remarkable combinatorial and projective geometry implications for digital sensor design. It is possible for the procedure to be applicable in 3-axis accelerometers and adapted into firmware for truly kinematic device driver interfaces so long as the reporting rates are matched with the user interface refresh rates. It is shown that acoustic transducer sensors require phase loop locking for kinematic continuity whereas gravimetric accelerometers demand better measurement time consistence in

Health Inequities: Evaluation of Two Paradigms

ERIC Educational Resources Information Center

Ashcroft, Rachelle

2010-01-01

Social work practice in health is shaped by underlying paradigms. To effectively target health inequities, practitioners need to consider appropriate paradigms. In this exploration of how six health paradigms shape theory and practice, the two health paradigms that most attended to health inequalities are social determinants of health and…

Method and apparatus for reducing spacecraft instrument induced jitter via multifrequency cancellation

NASA Technical Reports Server (NTRS)

Liu, Ketao (Inventor); Uetrecht, David S. (Inventor)

2002-01-01

A method, apparatus, article of manufacture, and a memory structure for compensating for instrument induced spacecraft jitter is disclosed. The apparatus comprises a spacecraft control processor for producing an actuator command signal, a signal generator, for producing a cancellation signal having at least one harmonic having a frequency and an amplitude substantially equal to that of a disturbance harmonic interacting with a spacecraft structural resonance and a phase substantially out of phase with the disturbance harmonic interacting with the spacecraft structural resonance, and at least one spacecraft control actuator, communicatively coupled to the spacecraft control processor and the signal generator for inducing satellite motion according to the actuator command signal and the cancellation signal. The method comprises the steps of generating a cancellation signal having at least one harmonic having a frequency and an amplitude substantially equal to that of a disturbance harmonic interacting with a spacecraft structural resonance and a phase substantially out of phase with the disturbance harmonic interacting with the spacecraft structural resonance, and providing the cancellation signal to a spacecraft control actuator. The apparatus comprises a storage device tangibly embodying the method steps described above.

The Investment Paradigm

ERIC Educational Resources Information Center

Perna, Mark C.

2005-01-01

Is marketing an expense or an investment? Most accountants will claim that marketing is an expense, and clearly that seems true when cutting the checks to fund these efforts. When it is done properly, marketing is the best investment. A key principle to Smart Marketing is the Investment Paradigm. The Investment Paradigm is understanding that every…

Simulation of sloshing dynamics induced forces and torques actuated on dewar container driven by gravity gradient and jitter accelerations in microgravity

NASA Technical Reports Server (NTRS)

Hung, R. J.; Pan, H. L.

1993-01-01

Some experimental spacecraft use superconducting sensors for gyro read-out and so must be maintained at a very low temperature. The boil-off from the cryogenic liquid used to cool the sensors can also be used, as the Gravity Probe B (GP-B) spacecraft does, as propellant to maintain attitude control and drag-free operation of the spacecraft. The cryogenic liquid for such spacecraft is, however, susceptible to both slosh-like motion and non-axisymmetric configurations under the influence of various kinds of gravity jitter and gravity gradient accelerations. Hence, it is important to quantify the magnitude of the liquid-induced perturbations on the spacecraft. We use the example of the GP-B to investigate such perturbations by numerical simulations. For this spacecraft disturbances can be imposed on the liquid by atmospheric drag, spacecraft attitude control maneuvers, and the earth's gravity gradient. More generally, onboard machinery vibrations and crew motion can also create disturbances. Recent studies suggest that high frequency disturbances are relatively unimportant in causing liquid motions in comparison to low frequency ones. The results presented here confirm this conclusion. After an initial calibration period, the GP-B spacecraft rotates in orbit at 0.1 rpm about the tank symmetry axis. For this rotation rate, the equilibrium liquid free surface shape is a 'doughnut' configuration for all residual gravity levels of 10(exp -6) g(sub 0) or less, as shown by experiments and by numerical simulations; furthermore, the superfluid behavior of the 1.8 K liquid helium used in GP-B eliminates temperature gradients and therefore such effects as Marangoni convection do not have to be considered. Classical fluid dynamics theory is used as the basis of the numerical simulations here, since Mason's experiments show that the theory is applicable for cryogenic liquid helium in large containers. To study liquid responses to various disturbances, we investigate and simulate

The Reception Learning Paradigm.

ERIC Educational Resources Information Center

Novak, Joseph D.

1979-01-01

Presented is a paradigm for science education research. The paradigm advances the reception learning theory, where regularities to be learned are presented explicitly to the learner. A tool for the study of knowledge production in science education, the Gowin "V," is presented. (RE)

Understanding paradigms used for nursing research.

PubMed

Weaver, Kathryn; Olson, Joanne K

2006-02-01

The aims of this paper are to add clarity to the discussion about paradigms for nursing research and to consider integrative strategies for the development of nursing knowledge. Paradigms are sets of beliefs and practices, shared by communities of researchers, which regulate inquiry within disciplines. The various paradigms are characterized by ontological, epistemological and methodological differences in their approaches to conceptualizing and conducting research, and in their contribution towards disciplinary knowledge construction. Researchers may consider these differences so vast that one paradigm is incommensurable with another. Alternatively, researchers may ignore these differences and either unknowingly combine paradigms inappropriately or neglect to conduct needed research. To accomplish the task of developing nursing knowledge for use in practice, there is a need for a critical, integrated understanding of the paradigms used for nursing inquiry. We describe the evolution and influence of positivist, postpositivist, interpretive and critical theory research paradigms. Using integrative review, we compare and contrast the paradigms in terms of their philosophical underpinnings and scientific contribution. A pragmatic approach to theory development through synthesis of cumulative knowledge relevant to nursing practice is suggested. This requires that inquiry start with assessment of existing knowledge from disparate studies to identify key substantive content and gaps. Knowledge development in under-researched areas could be accomplished through integrative strategies that preserve theoretical integrity and strengthen research approaches associated with various philosophical perspectives. These strategies may include parallel studies within the same substantive domain using different paradigms; theoretical triangulation to combine findings from paradigmatically diverse studies; integrative reviews; and mixed method studies. Nurse scholars are urged to

Macrostrategies: Creating Paradigm-versus-Paradigm Thinking.

ERIC Educational Resources Information Center

Hill, Larry K.

1991-01-01

Responds to "macrostrategies" concept in counseling advanced in previous articles by Herr, Ivey and Rigazio-DiGilio, and Dinkmeyer relative to broadening the service delivery perspective of the profession and thereby sustaining its heritage. Claims this work contributes significantly to strengthening a paradigm shift in that direction.…

Radiation hard programmable delay line for LHCb calorimeter upgrade

NASA Astrophysics Data System (ADS)

Mauricio, J.; Gascón, D.; Vilasís, X.; Picatoste, E.; Machefert, F.; Lefrancois, J.; Duarte, O.; Beigbeder, C.

2014-01-01

This paper describes the implementation of a SPI-programmable clock delay chip based on a Delay Locked Loop (DLL) in order to shift the phase of the LHC clock (25 ns) in steps of 1ns, with less than 5 ps jitter and 23 ps of DNL. The delay lines will be integrated into ICECAL, the LHCb calorimeter front-end analog signal processing ASIC in the near future. The stringent noise requirements on the ASIC imply minimizing the noise contribution of digital components. This is accomplished by implementing the DLL in differential mode. To achieve the required radiation tolerance several techniques are applied: double guard rings between PMOS and NMOS transistors as well as glitch suppressors and TMR Registers. This 5.7 mm2 chip has been implemented in CMOS 0.35 μm technology.

Full-custom design of split-set data weighted averaging with output register for jitter suppression

NASA Astrophysics Data System (ADS)

Jubay, M. C.; Gerasta, O. J.

2015-06-01

A full-custom design of an element selection algorithm, named as Split-set Data Weighted Averaging (SDWA) is implemented in 90nm CMOS Technology Synopsys Library. SDWA is applied in seven unit elements (3-bit) using a thermometer-coded input. Split-set DWA is an improved DWA algorithm which caters the requirement for randomization along with long-term equal element usage. Randomization and equal element-usage improve the spectral response of the unit elements due to higher Spurious-free dynamic range (SFDR) and without significantly degrading signal-to-noise ratio (SNR). Since a full-custom, the design is brought to transistor-level and the chip custom layout is also provided, having a total area of 0.3mm2, a power consumption of 0.566 mW, and simulated at 50MHz clock frequency. On this implementation, SDWA is successfully derived and improved by introducing a register at the output that suppresses the jitter introduced at the final stage due to switching loops and successive delays.

Paradigms for machine learning

NASA Technical Reports Server (NTRS)

Schlimmer, Jeffrey C.; Langley, Pat

1991-01-01

Five paradigms are described for machine learning: connectionist (neural network) methods, genetic algorithms and classifier systems, empirical methods for inducing rules and decision trees, analytic learning methods, and case-based approaches. Some dimensions are considered along with these paradigms vary in their approach to learning, and the basic methods are reviewed that are used within each framework, together with open research issues. It is argued that the similarities among the paradigms are more important than their differences, and that future work should attempt to bridge the existing boundaries. Finally, some recent developments in the field of machine learning are discussed, and their impact on both research and applications is examined.

Radiation Risk Assessment of the Individual Astronaut: A Complement to Radiation Interests at the NIH

NASA Technical Reports Server (NTRS)

Richmond, Robert C.

2004-01-01

Predicting human risks following exposure to space radiation is uncertain in part because of unpredictable distribution of high-LET and low-dose-derived damage amongst cells in tissues, unknown synergistic effects of microgravity upon gene- and protein-expression, and inadequately modeled processing of radiation-induced damage within cells to produce rare and late-appearing malignant cancers. Furthermore, estimation of risks of radiogenic outcome within small numbers of astronauts is not possible using classic epidemiologic study. It therefore seems useful to develop strategies of risk-assessment based upon large datasets acquired from correlated biological models useful for resolving radiogenic risk-assessment for irradiated individuals. In this regard, it is suggested that sensitive cellular biodosimeters that simultaneously report 1) the quantity of absorbed dose after exposure to ionizing radiation, 2) the quality of radiation delivering that dose, and 3) the biomolecular risk of malignant transformation be developed in order to resolve these NASA-specific challenges. Multiparametric cellular biodosimeters could be developed using analyses of gene-expression and protein-expression whereby large datasets of cellular response to radiation-induced damage are analyzed for markers predictive for acute response as well as cancer-risk. A new paradigm is accordingly addressed wherein genomic and proteomic datasets are registered and interrogated in order to provide statistically significant dose-dependent risk estimation in individual astronauts. This evaluation of the individual for assessment of radiogenic outcomes connects to NIH program in that such a paradigm also supports assignment of a given patient to a specific therapy, the diagnosis of response of that patient to therapy, and the prediction of risks accumulated by that patient during therapy - such as risks incurred by scatter and neutrons produced during high-energy Intensity-Modulated Radiation Therapy

Engineering paradigms and anthropogenic global change

NASA Astrophysics Data System (ADS)

Bohle, Martin

2016-04-01

This essay discusses 'paradigms' as means to conceive anthropogenic global change. Humankind alters earth-systems because of the number of people, the patterns of consumption of resources, and the alterations of environments. This process of anthropogenic global change is a composite consisting of societal (in the 'noosphere') and natural (in the 'bio-geosphere') features. Engineering intercedes these features; e.g. observing stratospheric ozone depletion has led to understanding it as a collateral artefact of a particular set of engineering choices. Beyond any specific use-case, engineering works have a common function; e.g. civil-engineering intersects economic activity and geosphere. People conceive their actions in the noosphere including giving purpose to their engineering. The 'noosphere' is the ensemble of social, cultural or political concepts ('shared subjective mental insights') of people. Among people's concepts are the paradigms how to shape environments, production systems and consumption patterns given their societal preferences. In that context, engineering is a means to implement a given development path. Four paradigms currently are distinguishable how to make anthropogenic global change happening. Among the 'engineering paradigms' for anthropogenic global change, 'adaptation' is a paradigm for a business-as-usual scenario and steady development paths of societies. Applying this paradigm implies to forecast the change to come, to appropriately design engineering works, and to maintain as far as possible the current production and consumption patterns. An alternative would be to adjust incrementally development paths of societies, namely to 'dovetail' anthropogenic and natural fluxes of matter and energy. To apply that paradigm research has to identify 'natural boundaries', how to modify production and consumption patterns, and how to tackle process in the noosphere to render alterations of common development paths acceptable. A further alternative

Limiting effects in double EEX beamline

NASA Astrophysics Data System (ADS)

Ha, G.; Power, J. G.; Conde, M.; Doran, D. S.; Gai, W.

2017-07-01

The double emittance exchange (EEX) beamline is suggested to overcome the large horizontal emittance and transverse jitter issues associated with the single EEX beamline while preserving its powerful phase-space manipulation capability. However, the double EEX beamline also has potential limitations due to coherent synchrotron radiation (CSR) and transverse jitter. The former limitation arises because double EEX uses twice as many bending magnets as single EEX which means stronger CSR effects degrading the beam quality. The latter limitation arises because a longitudinal jitter in front of the first EEX beamline is converted into a transverse jitter in the middle section (between the EEX beamlines) which can cause beam loss or beam degradation. In this paper, we numerically explore the effects of these two limitations on the emittance and beam transport.

Probabilistic model of nonlinear penalties due to collision-induced timing jitter for calculation of the bit error ratio in wavelength-division-multiplexed return-to-zero systems

NASA Astrophysics Data System (ADS)

Sinkin, Oleg V.; Grigoryan, Vladimir S.; Menyuk, Curtis R.

2006-12-01

We introduce a fully deterministic, computationally efficient method for characterizing the effect of nonlinearity in optical fiber transmission systems that utilize wavelength-division multiplexing and return-to-zero modulation. The method accurately accounts for bit-pattern-dependent nonlinear distortion due to collision-induced timing jitter and for amplifier noise. We apply this method to calculate the error probability as a function of channel spacing in a prototypical multichannel return-to-zero undersea system.

New paradigms and future challenges in Radiation Oncology: An Update of Biological Targets and Technology*

PubMed Central

Liauw, Stanley L.; Connell, Philip P.; Weichselbaum, Ralph R.

2013-01-01

The primary objective of radiation oncology is to exploit the biological interaction of radiation within tissue to promote tumor death while minimizing damage to surrounding normal tissue. The clinical delivery of radiation relies on principles of radiation physics that define how radiation energy is deposited in the body, as well as technology that facilitates accurate tumor targeting. This review will summarize the current landscape of recent biological and technological advances in radiation oncology, describe the challenges that exist, and offer potential avenues for improvement. PMID:23427246

Reduction of timing jitter in a Q-Switched Nd:YAG laser by direct bleaching of a Cr4+:YAG saturable absorber.

PubMed

Cole, Brian; Goldberg, Lew; Trussell, C Ward; Hays, Alan; Schilling, Bradley W; McIntosh, Chris

2009-02-02

A method for optical triggering of a Q-switched Nd:YAG laser by direct bleaching of a Cr:YAG saturable absorber is described. This method involves the bleaching of a thin sheet of the saturable absorber from a direction orthogonal to the lasing axis using a single laser diode bar, where the Cr:YAG transmission increased from a non-bleached value of 47% to a bleached value of 63%. For steady state operation of a passively Q-switched laser (PRF=10 Hz), the pulse-to-pulse timing jitter showed approximately 12X reduction in standard deviation, from 241 nsec for free running operation to 20 nsec with optical triggering.

Response to Elvira Panaiotidi, "The Nature of Paradigms and Paradigm Shifts in Music Education"

ERIC Educational Resources Information Center

Kurkul, Wenyi W.

2005-01-01

In her paper, Panaiotidi discusses the debate over the approaches in music education by Reimer and Elliott in the context of paradigm shifts. The term, "paradigm shift," was introduced by Thomas Kuhn in 1962 in his highly influential book, "The Structure of Scientific Revolutions." In this article, the author believes that what…

Transmission line transformer for reliable and low-jitter triggering of a railgap switch.

PubMed

Verma, Rishi; Mishra, Ekansh; Sagar, Karuna; Meena, Manraj; Shyam, Anurag

2014-09-01

The performance of railgap switch critically relies upon multichannel breakdown between the extended electrodes (rails) in order to ensure distributed current transfer along electrode length and to minimize the switch inductance. The initiation of several simultaneous arc channels along the switch length depends on the gap triggering technique and on the rate at which the electric field changes within the gap. This paper presents design, construction, and output characteristics of a coaxial cable based three-stage transmission line transformer (TLT) that is capable of initiating multichannel breakdown in a high voltage, low inductance railgap switch. In each stage three identical lengths of URM67 coaxial cables have been used in parallel and they have been wounded in separate cassettes to enhance the isolation of the output of transformer from the input. The cascaded output impedance of TLT is ~50 Ω. Along with multi-channel formation over the complete length of electrode rails, significant reduction in jitter (≤2 ns) and conduction delay (≤60 ns) has been observed by the realization of large amplitude (~80 kV), high dV/dt (~6 kV/ns) pulse produced by the indigenously developed TLT based trigger generator. The superior performance of TLT over conventional pulse transformer for railgap triggering application has been compared and demonstrated experimentally.

A new paradigm (Westphal-Paradigm) to study the neural correlates of panic disorder with agoraphobia.

PubMed

Wittmann, A; Schlagenhauf, F; John, T; Guhn, A; Rehbein, H; Siegmund, A; Stoy, M; Held, D; Schulz, I; Fehm, L; Fydrich, T; Heinz, A; Bruhn, H; Ströhle, A

2011-04-01

Agoraphobia (with and without panic disorder) is a highly prevalent and disabling anxiety disorder. Its neural complexity can be characterized by specific cues in fMRI studies. Therefore, we developed a fMRI paradigm with agoraphobia-specific stimuli. Pictures of potential agoraphobic situations were generated. Twenty-six patients, suffering from panic disorder and agoraphobia, and 22 healthy controls rated the pictures with respect to arousal, valence, and agoraphobia-related anxiety. The 96 pictures, which discriminated best between groups were chosen, split into two parallel sets and supplemented with matched neutral pictures from the International Affective Picture System. Reliability, criterion, and construct validity of the picture set were determined in a second sample (44 patients, 28 controls). The resulting event-related "Westphal-Paradigm" with cued and uncued pictures was tested in a fMRI pilot study with 16 patients. Internal consistency of the sets was very high; parallelism was given. Positive correlations of picture ratings with Mobility Inventory and Hamilton anxiety scores support construct validity. FMRI data revealed activations in areas associated with the fear circuit including amygdala, insula, and hippocampal areas. Psychometric properties of the Westphal-Paradigm meet necessary quality requirements for further scientific use. The paradigm reliably produces behavioral and fMRI patterns in response to agoraphobia-specific stimuli. To our knowledge, it is the first fMRI paradigm with these properties. This paradigm can be used to further characterize the functional neuroanatomy of panic disorder and agoraphobia and might be useful to contribute data to the differentiation of panic disorder and agoraphobia as related, but conceptually different clinical disorders.

Flexible robotics: a new paradigm.

PubMed

Aron, Monish; Haber, Georges-Pascal; Desai, Mihir M; Gill, Inderbir S

2007-05-01

The use of robotics in urologic surgery has seen exponential growth over the last 5 years. Existing surgical robots operate rigid instruments on the master/slave principle and currently allow extraluminal manipulations and surgical procedures. Flexible robotics is an entirely novel paradigm. This article explores the potential of flexible robotic platforms that could permit endoluminal and transluminal surgery in the future. Computerized catheter-control systems are being developed primarily for cardiac applications. This development is driven by the need for precise positioning and manipulation of the catheter tip in the three-dimensional cardiovascular space. Such systems employ either remote navigation in a magnetic field or a computer-controlled electromechanical flexible robotic system. We have adapted this robotic system for flexible ureteropyeloscopy and have to date completed the initial porcine studies. Flexible robotics is on the horizon. It has potential for improved scope-tip precision, superior operative ergonomics, and reduced occupational radiation exposure. In the near future, in urology, we believe that it holds promise for endoluminal therapeutic ureterorenoscopy. Looking further ahead, within the next 3-5 years, it could enable transluminal surgery.

Goal Structured Notation in a Radiation Hardening Safety Case for COTS-Based Spacecraft

NASA Technical Reports Server (NTRS)

Witulski, Arthur; Austin, Rebekah; Reed, Robert; Karsai, Gabor; Mahadevan, Nag; Sierawski, Brian; Evans, John; LaBel, Ken

2016-01-01

A systematic approach is presented to constructing a radiation assurance case using Goal Structured Notation (GSN) for spacecraft containing COTS parts. The GSN paradigm is applied to an SRAM single-event upset experiment board designed to fly on a CubeSat November 2016. Construction of a radiation assurance case without use of hardened parts or extensive radiation testing is discussed.

A new learning paradigm: learning using privileged information.

PubMed

Vapnik, Vladimir; Vashist, Akshay

2009-01-01

In the Afterword to the second edition of the book "Estimation of Dependences Based on Empirical Data" by V. Vapnik, an advanced learning paradigm called Learning Using Hidden Information (LUHI) was introduced. This Afterword also suggested an extension of the SVM method (the so called SVM(gamma)+ method) to implement algorithms which address the LUHI paradigm (Vapnik, 1982-2006, Sections 2.4.2 and 2.5.3 of the Afterword). See also (Vapnik, Vashist, & Pavlovitch, 2008, 2009) for further development of the algorithms. In contrast to the existing machine learning paradigm where a teacher does not play an important role, the advanced learning paradigm considers some elements of human teaching. In the new paradigm along with examples, a teacher can provide students with hidden information that exists in explanations, comments, comparisons, and so on. This paper discusses details of the new paradigm and corresponding algorithms, introduces some new algorithms, considers several specific forms of privileged information, demonstrates superiority of the new learning paradigm over the classical learning paradigm when solving practical problems, and discusses general questions related to the new ideas.

Correlation Analysis of Prompt Emission from Gamma Ray Bursts

NASA Astrophysics Data System (ADS)

Pothapragada, Sriharsha

Prompt emission from gamma-ray bursts (GRBs) exhibits very rapid, complicated temporal and spectral evolution. This diverse variability in the light-curves reflects the complicated nature of the underlying physics, in which inter-penetrating relativistic shells in the outflow are believed to generate strong magnetic fields that vary over very small scales. We use the theory of jitter radiation to model the emission from such regions and the resulting overall prompt gamma ray emission from a series of relativistic collisionless shocks. We present simulated GRB light-curves developed as a series of "pulses" corresponding to instantaneously illuminated "thin-shell" regions emitting via the jitter radiation mechanism. The effects of various geometries, viewing angles, and bulk Lorentz factor profiles of the radiating outflow jets on the spectral features and evolution of these light-curves are explored. Our results demonstrate how an anisotropic jitter radiation pattern, in conjunction with relativistic shock kinematics, can produce certain features observed in the GRB prompt emission spectra, such as the occurrence of hard, synchrotron violating spectra, the "tracking" of observed flux with spectral parameters, and spectral softening below peak energy within individual episodes of the light curve. We highlight predictions in the light of recent advances in the observational sphere of GRBs.

The search for understanding: the role of paradigms.

PubMed

Kelly, Marcella; Dowling, Maura; Millar, Michelle

2018-03-16

Kuhn's ( 1962 ) acknowledgement of a paradigm as a way that scientists make sense of their world and its reality gave recognition to the idea of 'paradigm shift'. This shift exposes the transience of paradigm development shaped by societal and scientific evolution. This ongoing evolutionary development provides the researcher with many paradigms to consider regarding how research is undertaken and the search for understanding achieved. An understanding of paradigm development is necessary when planning a study and can shape the search for understanding. It is hoped that the discussion presented here will assist novice and experienced researchers in articulating the rationales for their paradigm choices. An overview of the dominant paradigms is presented, reflecting ongoing paradigm development shaped by ontological, epistemological and methodological perspectives. Potential paradigm choices that shape research aims, objectives and focus in the search for understanding are considered. The inherent debates about paradigm shift, division, war and synthesis leave the researcher many perspectives to consider. Articulating the world views underpinning constructivism, interpretivism and pragmatism is particularly challenging because of the blurring of boundaries between them. The evolutionary nature of paradigmatic development has provided nurse researchers with the opportunity for methodological openness to the myriad research approaches, methods and designs that they may choose to answer their research question. However, it is imperative that researchers consider their ontological stances and the nature of their research questions. This is challenging in constructivism, interpretivism and pragmatism, where there is often an overlap of paradigm world views. ©2018 RCN Publishing Company Ltd. All rights reserved. Not to be copied, transmitted or recorded in any way, in whole or part, without prior permission of the publishers.

3-D RPIC Simulations of Relativistic Jets: Particle Acceleration, Magnetic Field Generation, and Emission

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Mizuno, Y.; Hardee, P.; Hededal, C. B.; Fishman, G. J.

2006-01-01

Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets into ambient plasmas show that acceleration occurs in relativistic shocks. The Weibel instability created in shocks is responsible for particle acceleration, and generation and amplification of highly inhomogeneous, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection in relativistic jets. The "jitter" radiation from deflected electrons has different properties than the synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understand the complex time evolution and spectral structure in relativistic jets and gamma-ray bursts. We will present recent PIC simulations which show particle acceleration and magnetic field generation. We will also calculate associated self-consistent emission from relativistic shocks.

An Eastern Paradigm of Evaluation

ERIC Educational Resources Information Center

Russon, Craig

2008-01-01

Teaching on the philosophies of evaluation as part of a pilot introductory course of a new diploma programme jointly sponsored by the United Nations (UN) Evaluation Group and the United Nations Staff College, the author compared and contrasted the "rationalistic" paradigm with the "naturalistic" paradigm on the basis of ontology, epistemology, and…

Ostracism Online: A social media ostracism paradigm.

PubMed

Wolf, Wouter; Levordashka, Ana; Ruff, Johanna R; Kraaijeveld, Steven; Lueckmann, Jan-Matthis; Williams, Kipling D

2015-06-01

We describe Ostracism Online, a novel, social media-based ostracism paradigm designed to (1) keep social interaction experimentally controlled, (2) provide researchers with the flexibility to manipulate the properties of the social situation to fit their research purposes, (3) be suitable for online data collection, (4) be convenient for studying subsequent within-group behavior, and (5) be ecologically valid. After collecting data online, we compared the Ostracism Online paradigm with the Cyberball paradigm (Williams & Jarvis Behavior Research Methods, 38, 174-180, 2006) on need-threat and mood questionnaire scores (van Beest & Williams Journal of Personality and Social Psychology 91, 918-928, 2006). We also examined whether ostracized targets of either paradigm would be more likely to conform to their group members than if they had been included. Using a Bayesian analysis of variance to examine the individual effects of the different paradigms and to compare these effects across paradigms, we found analogous effects on need-threat and mood. Perhaps because we examined conformity to the ostracizers (rather than neutral sources), neither paradigm showed effects of ostracism on conformity. We conclude that Ostracism Online is a cost-effective, easy to use, and ecologically valid research tool for studying the psychological and behavioral effects of ostracism.

Effort-Based Decision-Making Paradigms for Clinical Trials in Schizophrenia: Part 1—Psychometric Characteristics of 5 Paradigms

PubMed Central

Reddy, L. Felice; Horan, William P.; Barch, Deanna M.; Buchanan, Robert W.; Dunayevich, Eduardo; Gold, James M.; Lyons, Naomi; Marder, Stephen R.; Treadway, Michael T.; Wynn, Jonathan K.; Young, Jared W.; Green, Michael F.

2015-01-01

Impairments in willingness to exert effort contribute to the motivational deficits characteristic of the negative symptoms of schizophrenia. The current study evaluated the psychometric properties of 5 new or adapted paradigms to determine their suitability for use in clinical trials of schizophrenia. This study included 94 clinically stable participants with schizophrenia and 40 healthy controls. The effort-based decision-making battery was administered twice to the schizophrenia group (baseline, 4-week retest) and once to the control group. The 5 paradigms included 1 that assesses cognitive effort, 1 perceptual effort, and 3 that assess physical effort. Each paradigm was evaluated on (1) patient vs healthy control group differences, (2) test-retest reliability, (3) utility as a repeated measure (ie, practice effects), and (4) tolerability. The 5 paradigms showed varying psychometric strengths and weaknesses. The Effort Expenditure for Rewards Task showed the best reliability and utility as a repeated measure, while the Grip Effort Task had significant patient-control group differences, and superior tolerability and administration duration. The other paradigms showed weaker psychometric characteristics in their current forms. These findings highlight challenges in adapting effort and motivation paradigms for use in clinical trials. PMID:26142081

A scheme for a shot-to-shot, femtosecond-resolved pulse length and arrival time measurement of free electron laser x-ray pulses that overcomes the time jitter problem between the FEL and the laser

NASA Astrophysics Data System (ADS)

Juranić, P. N.; Stepanov, A.; Peier, P.; Hauri, C. P.; Ischebeck, R.; Schlott, V.; Radović, M.; Erny, C.; Ardana-Lamas, F.; Monoszlai, B.; Gorgisyan, I.; Patthey, L.; Abela, R.

2014-03-01

The recent entry of X-ray free electron lasers (FELs) to all fields of physics has created an enormous need, both from scientists and operators, for better characterization of the beam created by these facilities. Of particular interest is the measurement of the arrival time of the FEL pulse relative to a laser pump, for pump-probe experiments, and the measurement of the FEL pulse length. This article describes a scheme that corrects one of the major sources of uncertainty in these types of measurements, namely the jitter in the arrival time of the FEL relative to an experimental laser beam. The setup presented here uses a combination of THz streak cameras and a spectral encoding setup to reduce the effect of an FEL's jitter, leaving the pulse length as the only variable that can affect the accuracy of the pulse length and arrival time measurement. A discussion of underlying principles is also provided.

Paradigms for environmentally conscious manufacturing

NASA Astrophysics Data System (ADS)

Edinbarough, Immanuel A.; Wells, Wayne E.

2004-12-01

There are several stories involving the industries that pledge themselves for the environmentally conscious manufacturing practices. Paradigms for environmentally conscious manufacturing are associated with one of the aspects of environmental quality, protection, resource management, commitment or sustainability. The engineering rules of thumb that can easily be adopted by aspiring companies need identification. The underlying thread that unifies the efforts of environmentally conscious manufacturing companies, in offering the environmentally safe products to the world, is grouped and presented in the paper as paradigms for successful practices. The various ways in which a start up company, that wants to excel in environmentally conscious manufacturing, can position itself based on the paradigms is also discussed in the paper.

Goal Structuring Notation in a Radiation Hardening Assurance Case for COTS-Based Spacecraft

NASA Technical Reports Server (NTRS)

Witulski, Arthur; Austin, Rebekah; Evans, John; Mahadevan, Nag; Karsai, Gabor; Sierawski, Brian; LaBel, Ken; Reed, Robert; Schrimpf, Ron

2016-01-01

A systematic approach is presented to constructing a radiation assurance case using Goal Structuring Notation (GSN) for spacecraft containing commercial-off-the-shelf (COTS) parts. The GSN paradigm is applied to an SRAM single-event upset experiment board designed to fly on a CubeSat November 2016. Construction of a radiation assurance case without use of hardened parts or extensive radiation testing is discussed.

Information processing as a paradigm for decision making.

PubMed

Oppenheimer, Daniel M; Kelso, Evan

2015-01-03

For decades, the dominant paradigm for studying decision making--the expected utility framework--has been burdened by an increasing number of empirical findings that question its validity as a model of human cognition and behavior. However, as Kuhn (1962) argued in his seminal discussion of paradigm shifts, an old paradigm cannot be abandoned until a new paradigm emerges to replace it. In this article, we argue that the recent shift in researcher attention toward basic cognitive processes that give rise to decision phenomena constitutes the beginning of that replacement paradigm. Models grounded in basic perceptual, attentional, memory, and aggregation processes have begun to proliferate. The development of this new approach closely aligns with Kuhn's notion of paradigm shift, suggesting that this is a particularly generative and revolutionary time to be studying decision science.

A New Paradigm for Diagnosing Contributions to Model Aerosol Forcing Error: Diagnosing Model Aerosol Forcing Error

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

Jones, A. L.; Feldman, D. R.; Freidenreich, S.

A new paradigm in benchmark absorption-scattering radiative transfer is presented that enables both the globally averaged and spatially resolved testing of climate model radiation parameterizations in order to uncover persistent sources of biases in the aerosol instantaneous radiative effect (IRE). A proof of concept is demonstrated with the Geophysical Fluid Dynamics Laboratory AM4 and Community Earth System Model 1.2.2 climate models. Instead of prescribing atmospheric conditions and aerosols, as in prior intercomparisons, native snapshots of the atmospheric state and aerosol optical properties from the participating models are used as inputs to an accurate radiation solver to uncover model-relevant biases. Thesemore » diagnostic results show that the models' aerosol IRE bias is of the same magnitude as the persistent range cited (~1 W/m 2) and also varies spatially and with intrinsic aerosol optical properties. The findings presented here underscore the significance of native model error analysis and its dispositive ability to diagnose global biases, confirming its fundamental value for the Radiative Forcing Model Intercomparison Project.« less

A New Paradigm for Diagnosing Contributions to Model Aerosol Forcing Error: Diagnosing Model Aerosol Forcing Error

DOE PAGES

Jones, A. L.; Feldman, D. R.; Freidenreich, S.; ...

2017-12-07

A new paradigm in benchmark absorption-scattering radiative transfer is presented that enables both the globally averaged and spatially resolved testing of climate model radiation parameterizations in order to uncover persistent sources of biases in the aerosol instantaneous radiative effect (IRE). A proof of concept is demonstrated with the Geophysical Fluid Dynamics Laboratory AM4 and Community Earth System Model 1.2.2 climate models. Instead of prescribing atmospheric conditions and aerosols, as in prior intercomparisons, native snapshots of the atmospheric state and aerosol optical properties from the participating models are used as inputs to an accurate radiation solver to uncover model-relevant biases. Thesemore » diagnostic results show that the models' aerosol IRE bias is of the same magnitude as the persistent range cited (~1 W/m 2) and also varies spatially and with intrinsic aerosol optical properties. The findings presented here underscore the significance of native model error analysis and its dispositive ability to diagnose global biases, confirming its fundamental value for the Radiative Forcing Model Intercomparison Project.« less

Polarization Radiation with Turbulent Magnetic Fields from X-Ray Binaries

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

Zhang, Jian-Fu; Xiang, Fu-Yuan; Lu, Ju-Fu, E-mail: jfzhang@xtu.edu.cn, E-mail: fyxiang@xtu.edu.cn, E-mail: lujf@xmu.edu.cn

2017-02-10

We study the properties of polarized radiation in turbulent magnetic fields from X-ray binary jets. These turbulent magnetic fields are composed of large- and small-scale configurations, which result in the polarized jitter radiation when the characteristic length of turbulence is less than the non-relativistic Larmor radius. On the contrary, the polarized synchrotron emission occurs, corresponding to a large-scale turbulent environment. We calculate the spectral energy distributions and the degree of polarization for a general microquasar. Numerical results show that turbulent magnetic field configurations can indeed provide a high degree of polarization, which does not mean that a uniform, large-scale magneticmore » field structure exists. The model is applied to investigate the properties of polarized radiation of the black-hole X-ray binary Cygnus X-1. Under the constraint of multiband observations of this source, our studies demonstrate that the model can explain the high polarization degree at the MeV tail and predict the highly polarized properties at the high-energy γ -ray region, and that the dominant small-scale turbulent magnetic field plays an important role for explaining the highly polarized observation at hard X-ray/soft γ -ray bands. This model can be tested by polarization observations of upcoming polarimeters at high-energy γ -ray bands.« less

Transmission line transformer for reliable and low-jitter triggering of a railgap switch

NASA Astrophysics Data System (ADS)

Verma, Rishi; Mishra, Ekansh; Sagar, Karuna; Meena, Manraj; Shyam, Anurag

2014-09-01

The performance of railgap switch critically relies upon multichannel breakdown between the extended electrodes (rails) in order to ensure distributed current transfer along electrode length and to minimize the switch inductance. The initiation of several simultaneous arc channels along the switch length depends on the gap triggering technique and on the rate at which the electric field changes within the gap. This paper presents design, construction, and output characteristics of a coaxial cable based three-stage transmission line transformer (TLT) that is capable of initiating multichannel breakdown in a high voltage, low inductance railgap switch. In each stage three identical lengths of URM67 coaxial cables have been used in parallel and they have been wounded in separate cassettes to enhance the isolation of the output of transformer from the input. The cascaded output impedance of TLT is ˜50 Ω. Along with multi-channel formation over the complete length of electrode rails, significant reduction in jitter (≤2 ns) and conduction delay (≤60 ns) has been observed by the realization of large amplitude (˜80 kV), high dV/dt (˜6 kV/ns) pulse produced by the indigenously developed TLT based trigger generator. The superior performance of TLT over conventional pulse transformer for railgap triggering application has been compared and demonstrated experimentally.

Effort-Based Decision-Making Paradigms for Clinical Trials in Schizophrenia: Part 1—Psychometric Characteristics of 5 Paradigms.

PubMed

Reddy, L Felice; Horan, William P; Barch, Deanna M; Buchanan, Robert W; Dunayevich, Eduardo; Gold, James M; Lyons, Naomi; Marder, Stephen R; Treadway, Michael T; Wynn, Jonathan K; Young, Jared W; Green, Michael F

2015-09-01

Impairments in willingness to exert effort contribute to the motivational deficits characteristic of the negative symptoms of schizophrenia. The current study evaluated the psychometric properties of 5 new or adapted paradigms to determine their suitability for use in clinical trials of schizophrenia. This study included 94 clinically stable participants with schizophrenia and 40 healthy controls. The effort-based decision-making battery was administered twice to the schizophrenia group (baseline, 4-week retest) and once to the control group. The 5 paradigms included 1 that assesses cognitive effort, 1 perceptual effort, and 3 that assess physical effort. Each paradigm was evaluated on (1) patient vs healthy control group differences, (2) test-retest reliability, (3) utility as a repeated measure (ie, practice effects), and (4) tolerability. The 5 paradigms showed varying psychometric strengths and weaknesses. The Effort Expenditure for Rewards Task showed the best reliability and utility as a repeated measure, while the Grip Effort Task had significant patient-control group differences, and superior tolerability and administration duration. The other paradigms showed weaker psychometric characteristics in their current forms. These findings highlight challenges in adapting effort and motivation paradigms for use in clinical trials. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center 2015.

Fuzzy Hybrid Deliberative/Reactive Paradigm (FHDRP)

NASA Technical Reports Server (NTRS)

Sarmadi, Hengameth

2004-01-01

This work aims to introduce a new concept for incorporating fuzzy sets in hybrid deliberative/reactive paradigm. After a brief review on basic issues of hybrid paradigm the definition of agent-based fuzzy hybrid paradigm, which enables the agents to proceed and extract their behavior through quantitative numerical and qualitative knowledge and to impose their decision making procedure via fuzzy rule bank, is discussed. Next an example performs a more applied platform for the developed approach and finally an overview of the corresponding agents architecture enhances agents logical framework.

Large Diameter, Radiative Extinction Experiments with Decane Droplets in Microgravity

NASA Technical Reports Server (NTRS)

Easton, John; Tien, James; Dietrich, Daniel

1999-01-01

The extinction of a diffusion flame is of fundamental interest in combustion science. Linan, Law, and Chung and Law analytically and experimentally determined an extinction boundary in terms of droplet diameter and pressure for a single droplet due to Damkohler, or blowoff, extinction. More recently, other researchers demonstrated extinction due to finite rate kinetics in reduced gravity for free droplets of heptane. Chao modeled the effect of radiative heat loss on a quasi-steady spherically symmetric single droplet burning in the absence of buoyancy. They determined that for increasing droplet diameter, a second limit can be reached such that combustion is no longer possible. This second, larger droplet diameter limit arises due to radiative heat loss, which increases with increasing droplet and flame diameter. This increase in radiative heat loss arises due to an increase in the surface area of the flame. Recently, Marchese modeled fuel droplets with detailed chemistry and radiative effects, and compared the results to other work. The modeling also showed the importance of radiative loss and radiative extinction Experiments examined the behavior of a large droplet of decane burning in reduced gravity onboard the NASA Lewis DC-9 aircraft, but did not show a radiative extinction boundary due to g-jitter (Variations in gravitational level and direction) effects. Dietrich conducted experiments in the reduced gravity environment of the Space Shuttle. This work showed that the extinction diameter of methanol droplets increased when the initial diameter of the droplets was large (in this case, approximately 5 mm). Theoretical results agreed with these experimental results only when the theory included radiative effects . Radiative extinction was experimentally verified by Nayagam in a later Shuttle mission. The following work focuses on the combustion and extinction of a single fuel droplet. The goal is to experimentally determine a large droplet diameter limit that

Non-Targeted Effects Induced by Ionizing Radiation: Mechanisms and Potential Impact on Radiation Induced Health Effects

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

Morgan, William F.; Sowa, Marianne B.

Not-targeted effects represent a paradigm shift from the "DNA centric" view that ionizing radiation only elicits biological effects and subsequent health consequences as a result of an energy deposition event in the cell nucleus. While this is likely true at higher radiation doses (> 1Gy), at low doses (< 100mGy) non-targeted effects associated with radiation exposure might play a significant role. Here definitions of non-targeted effects are presented, the potential mechanisms for the communication of signals and signaling networks from irradiated cells/tissues are proposed, and the various effects of this intra- and intercellular signaling are described. We conclude with speculationmore » on how these observations might lead to and impact long-term human health outcomes.« less

G-Jitter Induced Magnetohydrodynamics Flow of Nanofluid with Constant Convective Thermal and Solutal Boundary Conditions

PubMed Central

Uddin, Mohammed J.; Khan, Waqar A.; Ismail, Ahmad Izani Md.

2015-01-01

Taking into account the effect of constant convective thermal and mass boundary conditions, we present numerical solution of the 2-D laminar g-jitter mixed convective boundary layer flow of water-based nanofluids. The governing transport equations are converted into non-similar equations using suitable transformations, before being solved numerically by an implicit finite difference method with quasi-linearization technique. The skin friction decreases with time, buoyancy ratio, and thermophoresis parameters while it increases with frequency, mixed convection and Brownian motion parameters. Heat transfer rate decreases with time, Brownian motion, thermophoresis and diffusion-convection parameters while it increases with the Reynolds number, frequency, mixed convection, buoyancy ratio and conduction-convection parameters. Mass transfer rate decreases with time, frequency, thermophoresis, conduction-convection parameters while it increases with mixed convection, buoyancy ratio, diffusion-convection and Brownian motion parameters. To the best of our knowledge, this is the first paper on this topic and hence the results are new. We believe that the results will be useful in designing and operating thermal fluids systems for space materials processing. Special cases of the results have been compared with published results and an excellent agreement is found. PMID:25933066

Improvement of dem Generation from Aster Images Using Satellite Jitter Estimation and Open Source Implementation

NASA Astrophysics Data System (ADS)

Girod, L.; Nuth, C.; Kääb, A.

2015-12-01

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system embarked on the Terra (EOS AM-1) satellite has been a source of stereoscopic images covering the whole globe at a 15m resolution at a consistent quality for over 15 years. The potential of this data in terms of geomorphological analysis and change detection in three dimensions is unrivaled and needs to be exploited. However, the quality of the DEMs and ortho-images currently delivered by NASA (ASTER DMO products) is often of insufficient quality for a number of applications such as mountain glacier mass balance. For this study, the use of Ground Control Points (GCPs) or of other ground truth was rejected due to the global "big data" type of processing that we hope to perform on the ASTER archive. We have therefore developed a tool to compute Rational Polynomial Coefficient (RPC) models from the ASTER metadata and a method improving the quality of the matching by identifying and correcting jitter induced cross-track parallax errors. Our method outputs more accurate DEMs with less unmatched areas and reduced overall noise. The algorithms were implemented in the open source photogrammetric library and software suite MicMac.

80-GHz AlGaInAs/InP 1.55 μm colliding-pulse mode-locked laser with low divergence angle and timing jitter

NASA Astrophysics Data System (ADS)

Hou, L. P.; Haji, M.; Li, C.; Qiu, B. C.; Bryce, A. C.

2011-07-01

We present an 80-GHz λ ~ 1.55 μm passively colliding-pulse mode-locked laser based on a novel AlGaInAs/InP epitaxial structure, which consists of a strained 3-quantum-well active layer incorporated with a passive far-field reduction layer. The device generated 910 fs pulses with a state-of-art timing jitter value of 190 fs (4 - 80 MHz), while demonstrating a low divergence angle (12.7°×26.3°) with two fold butt coupling efficiency to a flat cleaved single mode fiber when compared with the conventional mode-locked laser.

Black hole radiation with modified dispersion relation in tunneling paradigm: Static frame

NASA Astrophysics Data System (ADS)

Tao, Jun; Wang, Peng; Yang, Haitang

2017-09-01

To study possible deviations from the Hawking's prediction, we assume that the dispersion relations of matter fields are modified at high energies and use the Hamilton-Jacobi method to investigate the corresponding effects on the Hawking radiation in this paper. The preferred frame is the static frame of the black hole. The dispersion relation adopted agrees with the relativistic one at low energies but is modified near the Planck mass mp. We calculate the corrections to the Hawking temperature for massive and charged particles to O (mp-2) and massless and neutral particles to all orders. Our results suggest that the thermal spectrum of radiations near horizon is robust, e.g. corrections to the Hawking temperature are suppressed by mp. After the spectrum of radiations near the horizon is obtained, we use the brick wall model to compute the thermal entropy of a massless scalar field near the horizon of a 4D spherically symmetric black hole. We find that the subleading logarithmic term of the entropy does not depend on how the dispersion relations of matter fields are modified. Finally, the luminosities of black holes are computed by using the geometric optics approximation.

Paradigm Shifts in Ophthalmic Diagnostics*

PubMed Central

Sebag, J.; Sadun, Alfredo A.; Pierce, Eric A.

2016-01-01

Purpose Future advances in ophthalmology will see a paradigm shift in diagnostics from a focus on dysfunction and disease to better measures of psychophysical function and health. Practical methods to define genotypes will be increasingly important and non-invasive nanotechnologies are needed to detect molecular changes that predate histopathology. Methods This is not a review nor meant to be comprehensive. Specific topics have been selected to illustrate the principles of important paradigm shifts that will influence the future of ophthalmic diagnostics. It is our impression that future evaluation of vision will go beyond visual acuity to assess ocular health in terms of psychophysical function. The definition of disease will incorporate genotype into what has historically been a phenotype-centric discipline. Non-invasive nanotechnologies will enable a paradigm shift from disease detection on a cellular level to a sub-cellular molecular level. Results Vision can be evaluated beyond visual acuity by measuring contrast sensitivity, color vision, and macular function, as these provide better insights into the impact of aging and disease. Distortions can be quantified and the psychophysical basis of vision can be better evaluated than in the past by designing tests that assess particular macular cell function(s). Advances in our understanding of the genetic basis of eye diseases will enable better characterization of ocular health and disease. Non-invasive nanotechnologies can assess molecular changes in the lens, vitreous, and macula that predate visible pathology. Oxygen metabolism and circulatory physiology are measurable indices of ocular health that can detect variations of physiology and early disease. Conclusions This overview of paradigm shifts in ophthalmology suggests that the future will see significant improvements in ophthalmic diagnostics. The selected topics illustrate the principles of these paradigm shifts and should serve as a guide to further

The Failure of Progressive Paradigm Reversal

ERIC Educational Resources Information Center

Guthrie, Gerard

2017-01-01

The student-centred, progressive paradigm has not had sustained success in changing teacher-centred, formalistic practices in "developing" country classrooms. Does "Gestalt-switch" and paradigm reversal demonstrate that progressive theory has realigned with formalistic reality, or has it remained axiomatic in the research and…

Rethinking School Effectiveness and Improvement: A Question of Paradigms

ERIC Educational Resources Information Center

Wrigley, Terry

2013-01-01

The purpose of this article is to contribute to progressive school change by developing a more systematic critique of school effectiveness (SE) and school improvement (SI) as paradigms. Diverse examples of paradigms and paradigm change in non-educational fields are used to create a model of paradigms for application to SE and SI, and to explore…

Biomedical and development paradigms in AIDS prevention.

PubMed Central

Wolffers, I.

2000-01-01

In the fight against the HIV/AIDS pandemic different approaches can be distinguished, reflecting professional backgrounds, world views and political interests. One important distinction is between the biomedical and the development paradigms. The biomedical paradigm is characterized by individualization and the concept of "risk". This again is related to the concept of the market where health is a product of services and progress a series of new discoveries that can be marketed. The development paradigm is characterized by participation of the different stakeholders and by community work. The concept "vulnerability" is important in the development paradigm and emphasis is placed on efforts to decrease this vulnerability in a variety of sustainable ways. Biomedical technology is definitely one of the tools in these efforts. In the beginning of the pandemic the biomedical approach was important for the discovery of the virus and understanding its epidemiology. Later, stakeholders became involved. In the light of absence of treatment or vaccines, the development paradigm became more important and the two approaches were more in balance. However, since the reports about effective treatment of AIDS and hope of development of vaccines, the biomedical paradigm has become a leading principle in many HIV/AIDS prevention programmes. There is a need for a better balance between the two paradigms. Especially in developing countries, where it is not realistic to think that sustainable biomedical interventions can be organized on a short-term basis, it would be counterproductive to base our efforts to deal with HIV/AIDS exclusively on the biomedical approach. PMID:10743300

Olfactory Cued Learning Paradigm.

PubMed

Liu, Gary; McClard, Cynthia K; Tepe, Burak; Swanson, Jessica; Pekarek, Brandon; Panneerselvam, Sugi; Arenkiel, Benjamin R

2017-05-05

Sensory stimulation leads to structural changes within the CNS (Central Nervous System), thus providing the fundamental mechanism for learning and memory. The olfactory circuit offers a unique model for studying experience-dependent plasticity, partly due to a continuous supply of integrating adult born neurons. Our lab has recently implemented an olfactory cued learning paradigm in which specific odor pairs are coupled to either a reward or punishment to study downstream circuit changes. The following protocol outlines the basic set up for our learning paradigm. Here, we describe the equipment setup, programming of software, and method of behavioral training.

The Cosmic Microwave Background Radiation and its Polarization

NASA Astrophysics Data System (ADS)

Wollack, Edward

2016-03-01

The cosmic microwave background (CMB) radiation and its faint polarization have provided a unique means to constrain the physical state of the early Universe. Continued advances in instrumentation, observation, and analysis have revealed polarized radiation signatures associated with gravitational lensing and have heightened the prospects for using precision polarimetry to experimentally confront the inflationary paradigm. Characterization of this relic radiation field has the power to constrain or reveal the detailed properties of astroparticle species and long wave gravitational radiation. On going and planned CMB polarization efforts from the ground, balloon, and space borne platforms will be briefly surveyed. Recent community activities by the Inflation Probe Science Interest Group (IPSIG) will also be summarized. NASA PCOS mini-symposium (invited IPSIG talk).

Superfluid helium sloshing dynamics induced oscillations and fluctuations of angular momentum, force and moment actuated on spacecraft driven by gravity gradient or jitter acceleration associated with slew motion

NASA Technical Reports Server (NTRS)

Hung, R. J.

1994-01-01

The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by the gravity gradient and jitter accelerations associated with slew motion for the purpose to perform scientific observation during the normal spacecraft operation are investigated. An example is given with the Advanced X-Ray Astrophysics Facility-Spectroscopy (AXAF-S) for slew motion which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics is based on the non-inertia frame spacecraft bound coordinate, and solve time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid-vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers have also been derived. Examples are also given for cases applicable to the AXAF-S spacecraft sloshing dynamics associated with slew motion.

The Underlying Social Dynamics of Paradigm Shifts.

PubMed

Rodriguez-Sickert, Carlos; Cosmelli, Diego; Claro, Francisco; Fuentes, Miguel Angel

2015-01-01

We develop here a multi-agent model of the creation of knowledge (scientific progress or technological evolution) within a community of researchers devoted to such endeavors. In the proposed model, agents learn in a physical-technological landscape, and weight is attached to both individual search and social influence. We find that the combination of these two forces together with random experimentation can account for both i) marginal change, that is, periods of normal science or refinements on the performance of a given technology (and in which the community stays in the neighborhood of the current paradigm); and ii) radical change, which takes the form of scientific paradigm shifts (or discontinuities in the structure of performance of a technology) that is observed as a swift migration of the knowledge community towards the new and superior paradigm. The efficiency of the search process is heavily dependent on the weight that agents posit on social influence. The occurrence of a paradigm shift becomes more likely when each member of the community attaches a small but positive weight to the experience of his/her peers. For this parameter region, nevertheless, a conservative force is exerted by the representatives of the current paradigm. However, social influence is not strong enough to seriously hamper individual discovery, and can act so as to empower successful individual pioneers who have conquered the new and superior paradigm.

The Underlying Social Dynamics of Paradigm Shifts

PubMed Central

Claro, Francisco; Fuentes, Miguel Angel

2015-01-01

We develop here a multi-agent model of the creation of knowledge (scientific progress or technological evolution) within a community of researchers devoted to such endeavors. In the proposed model, agents learn in a physical-technological landscape, and weight is attached to both individual search and social influence. We find that the combination of these two forces together with random experimentation can account for both i) marginal change, that is, periods of normal science or refinements on the performance of a given technology (and in which the community stays in the neighborhood of the current paradigm); and ii) radical change, which takes the form of scientific paradigm shifts (or discontinuities in the structure of performance of a technology) that is observed as a swift migration of the knowledge community towards the new and superior paradigm. The efficiency of the search process is heavily dependent on the weight that agents posit on social influence. The occurrence of a paradigm shift becomes more likely when each member of the community attaches a small but positive weight to the experience of his/her peers. For this parameter region, nevertheless, a conservative force is exerted by the representatives of the current paradigm. However, social influence is not strong enough to seriously hamper individual discovery, and can act so as to empower successful individual pioneers who have conquered the new and superior paradigm. PMID:26418255

Changing the Cultural Paradigm to Meet Emerging Requirements

NASA Technical Reports Server (NTRS)

Robbins, William W.

2007-01-01

This viewgraph presentation reviews changes that are required in Space Transportation. This new transportation paradigm from the reliance on the Space Shuttle to a mixture of space transportation vehicles, i.e., the Russian Progress, vehicle, the Japanese HTV, the European ATV and other commercial orbital transportation systems, requires a new cultural paradigm. This new paradigm is outlined, and reviewed.

Sloshing of Cryogenic Helium Driven by Lateral Impulse/Gravity Gradient-Dominated/or g-Jitter-Dominated Accelerations and Orbital Dynamics

NASA Technical Reports Server (NTRS)

Hung, R. J.; Long, Y. T.; Zu, G. J.

1996-01-01

The coupling of slosh dynamics within a partially filled rotating dewar of superfluid helium 11 with spacecraft orbital dynamics is investigated in response to the environmental disturbances of (a) lateral impulses, (b) gravity gradients and (c) g-jitter forces. The purpose of this study is to investigate how the coupling of helium 11 fluid slosh dynamics driven by three cases of environmental force with spacecraft dynamics can affect the bubble deformations and their associated fluid and spacecraft mass centre fluctuations. The numerical computation of slosh dynamics is based on a rotational frame, while the spacecraft dynamics is associated with a non-rotational frame. Results show that the major contribution of orbital dynamics is driven by coupling with slosh dynamics. Neglecting the effect of slosh dynamics acting on the spacecraft may lead to the wrong results for the development of orbital and attitude control techniques.

About hypotheses and paradigms: exploring the Discreetness-Chance Paradigm.

PubMed

Kaellis, Eugene

2006-01-01

Hypotheses generally conform to paradigms which, over time, change, usually tardily, after they have become increasingly difficult to sustain under the impact of non-conforming evidence and alternative hypotheses, but more important, when they no longer are comfortably ensconced in the surrounding social-economic-political-cultural milieu. It is asserted that this milieu is the most important factor in shaping scientific theorizing. Some examples are cited: the rejection of the evidence that the world orbits around the sun (suspected by Pythagoras) in favor of centuries-long firm adherence to the Ptolemaic geocentric system; the early acceptance of Natural Selection in spite of its tautological essence and only conjectural supporting evidence, because it justified contemporaneous social-political ideologies as typified by, e.g., Spencer and Malthus. Economic, social, and cultural factors are cited as providing the ground, i.e., ideational substrate, for what is cited as the Discreetness-Chance Paradigm (DCP), that has increasingly dominated physics, biology, and medicine for over a century and which invokes small, discrete packets of energy/matter (quanta, genes, microorganisms, aberrant cells) functioning within an environment of statistical, not determined, causality. There is speculation on a possible paradigmatic shift from the DCP, which has fostered the proliferation, parallel with ("splitting") taxonomy, of alleged individual disease entities, their diagnoses, and, when available, their specific remedies, something particularly prominent in, e.g., psychiatry's Diagnostic and Statistical Manual, a codified compendium of alleged mental and behavioral disorders, but evident in any textbook of diagnosis and treatment of physical ailments. This presumed paradigm shift may be reflected in Western medicine, presently increasingly empirical and atomized, towards a growing acceptance of a more generalized, subject-oriented, approach to health and disease, a non

A flow paradigm in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Yan, Li

2018-04-01

The success of hydrodynamics in high energy heavy-ion collisions leads to a flow paradigm, to understand the observed features of harmonic flow in terms of the medium collective expansion with respect to initial state geometrical properties. In this review, we present some essential ingredients in the flow paradigm, including the hydrodynamic modeling, the characterization of initial state geometry and the medium response relations. The extension of the flow paradigm to small colliding systems is also discussed. Supported by Natural Sciences and Engineering Research Council of Canada

Goal Structuring Notation in a Radiation Hardening Assurance Case for COTS-Based Spacecraft

NASA Technical Reports Server (NTRS)

Witulski, A.; Austin, R.; Evans, J.; Mahadevan, N.; Karsai, G.; Sierawski, B.; LaBel, K.; Reed, R.; Schrimpf, R.

2016-01-01

A systematic approach is presented to constructing a radiation assurance case using Goal Structuring Notation (GSN) for spacecraft containing COTS parts. The GSN paradigm is applied to an SRAM single-event upset experiment board designed to fly on a CubeSat in January 2017. A custom software language for development of a GSN assurance case is under development at Vanderbilt. Construction of a radiation assurance case without use of hardened parts or extensive radiation testing is discussed.

Paradigm Lost: The Human Chromosome Story.

ERIC Educational Resources Information Center

Unger, Lawrence; Blystone, Robert V.

1996-01-01

Discusses whether the discovery in 1956 that humans have a chromosome number of 46, as opposed to 47 or 48 as previously thought, fits into a paradigm shift of the Kuhnian type. Concludes that Kuhn probably would not have considered the chromosome number shift to be large enough to be a focus for one of his paradigms. (AIM)

Management of the Regional Lymph Nodes Following Breast-Conservation Therapy for Early-Stage Breast Cancer: An Evolving Paradigm

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

Warren, Laura E.G.; Punglia, Rinaa S.; Wong, Julia S.

2014-11-15

Radiation therapy to the breast following breast conservation surgery has been the standard of care since randomized trials demonstrated equivalent survival compared to mastectomy and improved local control and survival compared to breast conservation surgery alone. Recent controversies regarding adjuvant radiation therapy have included the potential role of additional radiation to the regional lymph nodes. This review summarizes the evolution of regional nodal management focusing on 2 topics: first, the changing paradigm with regard to surgical evaluation of the axilla; second, the role for regional lymph node irradiation and optimal design of treatment fields. Contemporary data reaffirm prior studies showingmore » that complete axillary dissection may not provide additional benefit relative to sentinel lymph node biopsy in select patient populations. Preliminary data also suggest that directed nodal radiation therapy to the supraclavicular and internal mammary lymph nodes may prove beneficial; publication of several studies are awaited to confirm these results and to help define subgroups with the greatest likelihood of benefit.« less

An evolving paradigm for the secretory pathway?

PubMed Central

Lippincott-Schwartz, Jennifer

2011-01-01

The paradigm that the secretory pathway consists of a stable endoplasmic reticulum and Golgi apparatus, using discrete transport vesicles to exchange their contents, gained important support from groundbreaking biochemical and genetic studies during the 1980s. However, the subsequent development of new imaging technologies with green fluorescent protein introduced data on dynamic processes not fully accounted for by the paradigm. As a result, we may be seeing an example of how a paradigm is evolving to account for the results of new technologies and their new ways of describing cellular processes. PMID:22039065

Understanding Mixed Emotions: Paradigms and Measures.

PubMed

Kreibig, Sylvia D; Gross, James J

2017-06-01

In this review, we examine the paradigms and measures available for experimentally studying mixed emotions in the laboratory. For eliciting mixed emotions, we describe a mixed emotions film library that allows for the repeated elicitation of a specific homogeneous mixed emotional state and appropriately matched pure positive, pure negative, and neutral emotional states. For assessing mixed emotions, we consider subjective and objective measures that fall into univariate, bivariate, and multivariate measurement categories. As paradigms and measures for objectively studying mixed emotions are still in their early stages, we conclude by outlining future directions that focus on the reliability, temporal dynamics, and response coherence of mixed emotions paradigms and measures. This research will build a strong foundation for future studies and significantly advance our understanding of mixed emotions.

The Soil Carbon Paradigm Shift: Triangulating Theories, Measurements, and Models

NASA Astrophysics Data System (ADS)

Blankinship, J. C.; Crow, S. E.; Schimel, J.; Sierra, C. A.; Schaedel, C.; Plante, A. F.; Thompson, A.; Berhe, A. A.; Druhan, J. L.; Heckman, K. A.; Keiluweit, M.; Lawrence, C. R.; Marin-Spiotta, E.; Rasmussen, C.; Wagai, R.; Wieder, W. R.

2016-12-01

Predicting global responses of soil carbon (C) to environmental change remains confounded by a number of paradigms that have emerged from separate approaches. A prevailing paradigm in biogeochemistry interprets soil C as discrete pools based on estimated or measured turnover times (e.g., CENTURY model). An alternative is emerging that envisions the stabilization of soil C in tension between decomposition by microbial agents and protection by physical and chemical mechanisms. We propose an approach to bridge the gap between different paradigms, and to improve soil C forecasting by conceptualizing each paradigm as a triangle composed of three nodes: theory, analytical measurement, and numerical model. Paradigms tend to emerge from what can either be represented in models or measured using analytical instruments. But they gain power when all three elements are integrated in a balanced trinity. Our goal was to compare how theory, measurement, and model fit together in our understanding of soil C to learn from past successes, evaluate the strengths and weaknesses of current paradigms, and guide development of new understanding. We used a case-study approach to analyze each corner of the paradigm-triangle: i) paradigms that have strong theory but are constrained by weak linkages with measurements or models, ii) paradigms with robust models that have weak linkages with theory or measurements, and iii) paradigms with many measurements but little theoretical support or ability to be parameterized in numerical models. We conclude that established models like CENTURY dominate because theory and measurements that underlie the model form strong linkages that previously created a balanced triangle. Evolving paradigms based on physical protection and microbial agency are still struggling to gain traction because the theory is challenging to represent in models. The explicit examination of the strengths of emerging paradigms can, therefore, help refine and accelerate our ability

Comparison of two paradigms for distributed shared memory

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

Levelt, W.G.; Kaashoek, M.F.; Bal, H.E.

1990-08-01

The paper compares two paradigms for Distributed Shared Memory on loosely coupled computing systems: the shared data-object model as used in Orca, a programming language specially designed for loosely coupled computing systems and the Shared Virtual Memory model. For both paradigms the authors have implemented two systems, one using only point-to-point messages, the other using broadcasting as well. They briefly describe these two paradigms and their implementations. Then they compare their performance on four applications: the traveling salesman problem, alpha-beta search, matrix multiplication and the all pairs shortest paths problem. The measurements show that both paradigms can be used efficientlymore » for programming large-grain parallel applications. Significant speedups were obtained on all applications. The unstructured Shared Virtual Memory paradigm achieves the best absolute performance, although this is largely due to the preliminary nature of the Orca compiler used. The structured shared data-object model achieves the highest speedups and is much easier to program and to debug.« less

Paradigms and Problem-Solving: A Literature Review.

ERIC Educational Resources Information Center

Berner, Eta S.

1984-01-01

Thomas Kuhn's conceptions of the influence of paradigms on the progress of science form the framework for analyzing how medical educators have approached research on medical problem solving. A new paradigm emphasizing multiple types of problems with varied solution strategies is proposed. (Author/MLW)

Using family paradigms to improve evidence-based practice.

PubMed

Hidecker, Mary Jo Cooley; Jones, Rebecca S; Imig, David R; Villarruel, Francisco A

2009-08-01

Evidence-based practice (EBP) describes clinical decision making using research, clinical experience, and client values. For family-centered practices, the client's family is integral to this process. This article proposes that using family paradigms, a family science framework, may help elicit and understand client/family values within family-centered EBP. This article describes the family paradigms framework: 4 classic paradigms of "closed," "random," "open," and "synchronous." Its applicability to family-centered EBP is proposed using augmentative and alternative communication examples. A family-centered approach to EBP requires families to be an integral part of clinical decision making, but some families may need assistance in enumerating their views and values. Family paradigms (which consider how a family uses its resources of time, space, energy, and material in the pursuit of its goals of control, affect, meaning, and content) may be a way to elicit family values and preferences relevant to clinical decisions. Family and client values can be incorporated throughout the EBP steps. Considering family paradigms may increase awareness and understanding of how families' views of their goals and resources affect clinical decisions. Further research is needed into both the processes and effectiveness of using family paradigms to conduct family-centered EBP.

The synthesis paradigm in genetics.

PubMed

Rice, William R

2014-02-01

Experimental genetics with model organisms and mathematically explicit genetic theory are generally considered to be the major paradigms by which progress in genetics is achieved. Here I argue that this view is incomplete and that pivotal advances in genetics--and other fields of biology--are also made by synthesizing disparate threads of extant information rather than generating new information from experiments or formal theory. Because of the explosive expansion of information in numerous "-omics" data banks, and the fragmentation of genetics into numerous subdisciplines, the importance of the synthesis paradigm will likely expand with time.

Understanding Mixed Emotions: Paradigms and Measures

PubMed Central

Kreibig, Sylvia D.; Gross, James J.

2017-01-01

In this review, we examine the paradigms and measures available for experimentally studying mixed emotions in the laboratory. For eliciting mixed emotions, we describe a mixed emotions film library that allows for the repeated elicitation of a specific homogeneous mixed emotional state and appropriately matched pure positive, pure negative, and neutral emotional states. For assessing mixed emotions, we consider subjective and objective measures that fall into univariate, bivariate, and multivariate measurement categories. As paradigms and measures for objectively studying mixed emotions are still in their early stages, we conclude by outlining future directions that focus on the reliability, temporal dynamics, and response coherence of mixed emotions paradigms and measures. This research will build a strong foundation for future studies and significantly advance our understanding of mixed emotions. PMID:28804752

Towards a New Paradigm of Moral Personhood

ERIC Educational Resources Information Center

Frimer, Jeremy A.; Walker, Lawrence J.

2008-01-01

Moral psychology is between paradigms. Kohlberg's model of moral rationality has proved inadequate in explaining action; yet its augmentation--moral personality--awaits empirical embodiment. This article addresses some critical issues in developing a comprehensive empirical paradigm of moral personhood. Is a first-person or a third-person…

Toward an Implementation Paradigm of Educational Change.

ERIC Educational Resources Information Center

Berman, Paul

Besides identifying current problems in educational change research, this document describes the inadequate paradigm on which past research has been based and outlines a currently emerging paradigm of educational innovation. The author asserts that previous research findings have been inconsistent and not comparable. Basic to the research problems…

An engineering paradigm in the biomedical sciences: Knowledge as epistemic tool.

PubMed

Boon, Mieke

2017-10-01

In order to deal with the complexity of biological systems and attempts to generate applicable results, current biomedical sciences are adopting concepts and methods from the engineering sciences. Philosophers of science have interpreted this as the emergence of an engineering paradigm, in particular in systems biology and synthetic biology. This article aims at the articulation of the supposed engineering paradigm by contrast with the physics paradigm that supported the rise of biochemistry and molecular biology. This articulation starts from Kuhn's notion of a disciplinary matrix, which indicates what constitutes a paradigm. It is argued that the core of the physics paradigm is its metaphysical and ontological presuppositions, whereas the core of the engineering paradigm is the epistemic aim of producing useful knowledge for solving problems external to the scientific practice. Therefore, the two paradigms involve distinct notions of knowledge. Whereas the physics paradigm entails a representational notion of knowledge, the engineering paradigm involves the notion of 'knowledge as epistemic tool'. Copyright © 2017 Elsevier Ltd. All rights reserved.

Is This the Paradigm Shift We Need?

ERIC Educational Resources Information Center

Mirvis, Jonathan

2012-01-01

Dr. Woocher's essay, states Mirvis, is seminal in the field of Jewish education. It proposes a new paradigm for Jewish education in North America. This proposed paradigm is supported by a comprehensive multi-disciplinary research drawing on literature from education, philosophy, history, sociology, psychology, and economics. The essay reflects a…

The use of repetition suppression paradigms in developmental cognitive neuroscience.

PubMed

Nordt, Marisa; Hoehl, Stefanie; Weigelt, Sarah

2016-07-01

Repetition suppression paradigms allow a more detailed look at brain functioning than classical paradigms and have been applied vigorously in adult cognitive neuroscience. These paradigms are well suited for studies in the field of developmental cognitive neuroscience as they can be applied without collecting a behavioral response and across all age groups. Furthermore, repetition suppression paradigms can be employed in various neuroscience techniques, such as functional magnetic resonance imaging (fMRI), functional near-infrared spectroscopy (fNIRS), electroencephalography (EEG) and magnetoencephalography (MEG). In the present article we review studies using repetition suppression paradigms in developmental cognitive neuroscience covering the age range from infancy to adolescence. Our first goal is to point out characteristics of developmental repetition suppression effects. In doing so, we discuss the relationship of the direction of repetition effects (suppression vs enhancement) with developmental factors, and address the question how the direction of repetition effects might be related to looking-time effects in behavioral infant paradigms, the most prominently used behavioral measure in infant research. To highlight the potential of repetition suppression paradigms, our second goal is to provide an overview on the insights recently obtained by applying repetition paradigms in neurodevelopmental studies, including research on children with autism spectrum disorders (ASDs). We conclude that repetition suppression paradigms are valuable tools for investigating neurodevelopmental processes, while at the same time we highlight the necessity for further studies that disentangle methodological and developmental factors. Copyright © 2016 Elsevier Ltd. All rights reserved.

[Nursing knowledge: the evolution of scientific philosophies and paradigm trends].

PubMed

Hung, Hsuan-Man; Wang, Hui-Ling; Chang, Yun-Hsuan; Chen, Chung-Hey

2010-02-01

Different aspects of philosophy are derived from different paradigms that contain various main points, some of which are repeated or overlap. Belief and practice are two components of a paradigm that provide perspective and framework and lead to nursing research. Changes in healthcare have popularized empirical and evidence-based research in the field of nursing research. However, the evidence-base study approach has given rise to a certain level of debate. Until now, no standard paradigm has been established for the nursing field, as different professionals use different paradigms in their studies. Such provides certain limitations as well as advantages. The quantitative aspects of a nursing paradigm were developed by Peplau and Henderson (1950) and Orem (1980). Such remained the standard until 1990, when Guba and Parse proposed qualitative viewpoints in contextual features. Therefore, the nursing paradigm has made great contributions to the development of knowledge in nursing care, although debate continues due to incomplete knowledge attributable to the presentation of knowledge and insight within individually developed paradigms. It is better to apply multiple paradigms to different research questions. It is suggested that better communication amongst experts regarding their individual points of view would help nursing members to integrate findings within the global pool of knowledge and allow replication over multiple studies.

Forest restoration paradigms

Treesearch

John Stanturf; Brian J. Palik; Mary I. Williams; R. Kasten Dumroese

2014-01-01

An estimated 2 billion ha of forests are degraded globally and global change suggests even greater need for forest restoration. Four forest restoration paradigms are identified and discussed: revegetation, ecological restoration, functional restoration, and forest landscape restoration. Restoration is examined in terms of a degraded starting point and an ending point...

A New Paradigm for Assessing the Role of Agriculture in the Climate System and in Climate Change

NASA Technical Reports Server (NTRS)

Pielke, Roger A., Sr.; Adegoke, Jimmy O.; Chase, Thomas N.; Marshall, Curtis H.; Matsui, Toshihisa; Niyogi, Dev

2007-01-01

This paper discusses the diverse climate forcings that impact agricultural systems, and contrasts the current paradigm of using global models downscaled to agricultural areas (a top-down approach) with a new paradigm that first assesses the vulnerability of agricultural activities to the spectrum of environmental risk including climate (a bottom-up approach). To illustrate the wide spectrum of climate forcings, regional climate forcings are presented including land-use/land-cover change and the influence of aerosols on radiative and biogeochemical fluxes and cloud/precipitation processes, as well as how these effects can be teleconnected globally. Examples are presented of the vulnerability perspective, along with a small survey of the perceived drought impacts in a local area, in which a wide range of impacts for the same precipitation deficits are found. This example illustrates why agricultural assessments of risk to climate change and variability and of other environmental risks should start with a bottom-up perspective.

Modulating Radiation Resistance: Novel Protection Paradigms Based on Defenses against Ionizing Radiation in the Extrempohile Deinococcus radiodurans

DTIC Science & Technology

2013-07-01

USA (2013); 2) Many environmental yeast are extremely radiation-resistant, accumulate nitrogenous Mn2+-Pi complexes, and highly resistant to...5 important in aerobic environments . Numerous organisms which accumulate “compatible solutes” fit this model, including representative archaea...cyanobacteria, lichens, alpine yeast, and tardigrades. 4.3 Knowns and Unknowns of Deinococcus Mn2+ Complexes It is worth reminding the reader

Auditory Pattern Memory

DTIC Science & Technology

1990-10-31

Creelman , 1962; Getty, 1975; Divenyi and Danner, kin et aL (1982) jitter-detection paradigm. An advantage of 1977; Divenyi and Sachs, 1978; and Allen...discrimination of tonal se- Creelman . C. D. (1962). "’Human discrimination ofauditory duration." 3. quences.’" J. Acoust. Soc. Am. 82.1218-1226. Acoust...single marked intervals (Abel, 1972a,b; Creelman , 1962; Getty, 1975; Divenyi and Danner, 1977; Divenyi and Sachs, 1978; Espinoza-Varas and Jamieson

Organizations, Paradigms, and People: The Challenge of KM Interventions

NASA Technical Reports Server (NTRS)

Bailey, Teresa; Burton, Yvette

1999-01-01

This paper presents viewgraphs on Knowledge Management (KM) and how these interventions are put into practice by organizations and society. The topics include: 1) The Multiple Paradigm Tool; 2) Four Paradigms: tool for the Analyzing Organizations; 3) Assumptions About the Nature of Social Science; 4) Assumptions About the Nature of Society; 5) Schools of Sociological and Organizational Theory; 6) Meaning and Metaphors in the Four Paradigms; and 7) Possibilities and Conclusions.

A Viable Paradigm for Quantum Reality

NASA Astrophysics Data System (ADS)

Srivastava, Jagdish

2010-10-01

After a brief discussion of the EPR paradox, Bell's inequality, and Aspect's experiment, arguments will be presented in favor of the following statements: ``As it stands, Quantum mechanics is incomplete. There is further hidden structure, which would involve variables. No influence can move faster than light. The wave function is one whole thing and any change in its structure instantly influences its outcomes. Bell's theorem has not been applied correctly. There is a better paradigm.'' The said paradigm will be presented.

A Practical Examination of Two Diverse Research Paradigms

ERIC Educational Resources Information Center

Brewer, Robert A.

2007-01-01

This manuscript examines the practical differences between quantitative and qualitative inquiry by comparing the differences between one article from each paradigm. Quantitative research differs greatly from qualitative inquiry in purpose, assumptions, methodology, and representation. While quantitative research has been the dominant paradigm for…

Seismic Overstatement: Challenging the Paradigm Shift in Composition.

ERIC Educational Resources Information Center

Bell, James

1995-01-01

Discusses Maxine Hairston's appropriation in 1982 of Thomas Kuhn's epistemology and his concept of "paradigm shift." Argues that the paradigm shift must be treated as an enabling fiction through which members of the professional can speculate on better ways to teach students. (SR)

Geographic Object-Based Image Analysis - Towards a new paradigm.

PubMed

Blaschke, Thomas; Hay, Geoffrey J; Kelly, Maggi; Lang, Stefan; Hofmann, Peter; Addink, Elisabeth; Queiroz Feitosa, Raul; van der Meer, Freek; van der Werff, Harald; van Coillie, Frieke; Tiede, Dirk

2014-01-01

The amount of scientific literature on (Geographic) Object-based Image Analysis - GEOBIA has been and still is sharply increasing. These approaches to analysing imagery have antecedents in earlier research on image segmentation and use GIS-like spatial analysis within classification and feature extraction approaches. This article investigates these development and its implications and asks whether or not this is a new paradigm in remote sensing and Geographic Information Science (GIScience). We first discuss several limitations of prevailing per-pixel methods when applied to high resolution images. Then we explore the paradigm concept developed by Kuhn (1962) and discuss whether GEOBIA can be regarded as a paradigm according to this definition. We crystallize core concepts of GEOBIA, including the role of objects, of ontologies and the multiplicity of scales and we discuss how these conceptual developments support important methods in remote sensing such as change detection and accuracy assessment. The ramifications of the different theoretical foundations between the ' per-pixel paradigm ' and GEOBIA are analysed, as are some of the challenges along this path from pixels, to objects, to geo-intelligence. Based on several paradigm indications as defined by Kuhn and based on an analysis of peer-reviewed scientific literature we conclude that GEOBIA is a new and evolving paradigm.

On the Transport and Radiative Properties of Plasmas with Small-Scale Electromagnetic Fluctuations

NASA Astrophysics Data System (ADS)

Keenan, Brett D.

Plasmas with sub-Larmor-scale ("small-scale") electromagnetic fluctuations are a feature of a wide variety of high-energy-density environments, and are essential to the description of many astrophysical/laboratory plasma phenomena. Radiation from particles, whether they be relativistic or non-relativistic, moving through small-scale electromagnetic turbulence has spectral characteristics distinct from both synchrotron and cyclotron radiation. The radiation, carrying information on the statistical properties of the turbulence, is also intimately related to the particle diffusive transport. We investigate, both theoretically and numerically, the transport of non-relativistic and transrelativistic particles in plasmas with high-amplitude isotropic sub-Larmor-scale magnetic turbulence---both with and without a mean field component---and its relation to the spectra of radiation simultaneously produced by these particles. Furthermore, the transport of particles through small-scale electromagnetic turbulence---under certain conditions---resembles the random transport of particles---via Coulomb collisions---in collisional plasmas. The pitch-angle diffusion coefficient, which acts as an effective "collision" frequency, may be substantial in these, otherwise, collisionless environments. We show that this effect, colloquially referred to as the plasma "quasi-collisionality", may radically alter the expected radiative transport properties of candidate plasmas. We argue that the modified magneto-optic effects in these plasmas provide an attractive, novel, diagnostic tool for the exploration and characterization of small-scale electromagnetic turbulence. Lastly, we speculate upon the manner in which quasi-collisions may affect inertial confinement fusion (ICF), and other laser-plasma experiments. Finally, we show that mildly relativistic jitter radiation, from laser-produced plasmas, may offer insight into the underlying electromagnetic turbulence. Here we investigate the

Paradigms of psychiatry: eclecticism and its discontents.

PubMed

Ghaemi, Seyyed Nassir

2006-11-01

To assess paradigms of psychiatry, assessing their strengths and limitations. The biopsychosocial model, and eclecticism in general, serves as the primary paradigm of mainstream contemporary psychiatry. In the past few decades, the biopsychosocial model served as a cease-fire between the biological and psychoanalytic extremism that characterized much of the 19th and 20th century history of psychiatry. Despite being broad and fostering an 'anything goes' mentality, it fails to provide much guidance as a model. In recent years, the biological school has gained prominence and now is under attack from many quarters. Critics tend toward dogmatism themselves, usually of postmodernist or libertarian varieties. Three alternate approaches include pragmatism, integrationism, and pluralism. Pluralism, as technically defined here based on the work of Karl Jaspers, rejects or accepts different methods but holds that some methods are better than others for specific circumstances or conditions. The compromise paradigm of biopsychosocial eclecticism has failed to sufficiently guide contemporary psychiatry. The concurrent revival of the biological model has led to postmodernist counter-reactions which, though valid in many specifics, promise to replace one ideological dogma with another. New paradigms are needed.

Behavioral Assessment of Listening Effort Using a Dual-Task Paradigm.

PubMed

Gagné, Jean-Pierre; Besser, Jana; Lemke, Ulrike

2017-01-01

Published investigations ( n = 29) in which a dual-task experimental paradigm was employed to measure listening effort during speech understanding in younger and older adults were reviewed. A summary of the main findings reported in the articles is provided with respect to the participants' age-group and hearing status. Effects of different signal characteristics, such as the test modality, on dual-task outcomes are evaluated, and associations with cognitive abilities and self-report measures of listening effort are described. Then, several procedural issues associated with the use of dual-task experiment paradigms are discussed. Finally, some issues that warrant future research are addressed. The review revealed large variability in the dual-task experimental paradigms that have been used to measure the listening effort expended during speech understanding. The differences in experimental procedures used across studies make it difficult to draw firm conclusions concerning the optimal choice of dual-task paradigm or the sensitivity of specific paradigms to different types of experimental manipulations. In general, the analysis confirmed that dual-task paradigms have been used successfully to measure differences in effort under different experimental conditions, in both younger and older adults. Several research questions that warrant further investigation in order to better understand and characterize the intricacies of dual-task paradigms were identified.

Behavioral Assessment of Listening Effort Using a Dual-Task Paradigm

PubMed Central

Besser, Jana; Lemke, Ulrike

2017-01-01

Published investigations (n = 29) in which a dual-task experimental paradigm was employed to measure listening effort during speech understanding in younger and older adults were reviewed. A summary of the main findings reported in the articles is provided with respect to the participants’ age-group and hearing status. Effects of different signal characteristics, such as the test modality, on dual-task outcomes are evaluated, and associations with cognitive abilities and self-report measures of listening effort are described. Then, several procedural issues associated with the use of dual-task experiment paradigms are discussed. Finally, some issues that warrant future research are addressed. The review revealed large variability in the dual-task experimental paradigms that have been used to measure the listening effort expended during speech understanding. The differences in experimental procedures used across studies make it difficult to draw firm conclusions concerning the optimal choice of dual-task paradigm or the sensitivity of specific paradigms to different types of experimental manipulations. In general, the analysis confirmed that dual-task paradigms have been used successfully to measure differences in effort under different experimental conditions, in both younger and older adults. Several research questions that warrant further investigation in order to better understand and characterize the intricacies of dual-task paradigms were identified. PMID:28091178

Microscopic Processes in Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P.; Mizuno, Y.; Medvedev, M.; Zhang, B.; Nordlund, A.; Fredricksen, J.; Sol, H.; Niemiec, J.; Lyubarsky, Y.;

New Relativistic Particle-In-Cell Simulation Studies of Prompt and Early Afterglows from GRBs

NASA Technical Reports Server (NTRS)

Nishikawa, Ken-ichi; Hardee, P.; Mizuno, Y.; Zhang, B.; Medvedev, M.; Hartmann, D.; Fishman, J. F.; Preece, R.

2008-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations of relativistic electron-ion (electro-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In the collisionless relativistic shock particle acceleration is due to plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel (filamentation) instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The 'jitter' radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Particle Acceleration, Magnetic Field Generation, and Associated Emission in Collisionless Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.

2007-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron)jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Particle Acceleration, Magnetic Field Generation and Associated Emission in Collisionless Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K. I.; Ramirez-Ruiz, E.; Hardee, P.; Mizuno, Y.; Fishman. G. J.

2007-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

The Poynting-Stokes Tensor And Radiative Transfer In Turbid Media: The Microphysical Paradigm

NASA Astrophysics Data System (ADS)

Mishchenko, M. I.

2010-12-01

This paper solves the long-standing problem of establishing the fundamental physical link between the radiative transfer theory and macroscopic electromagnetics in the case of elastic scattering by a sparse discrete random medium. The radiative transfer equation (RTE) is derived directly from the macroscopic Maxwell equations by computing theoretically the appropriately defined so-called Poynting-Stokes tensor carrying informa-tion on both the direction, magnitude, and polarization characteristics of lo-cal electromagnetic energy flow. Our derivation from first principles shows that to compute the local Poynting vector averaged over a sufficiently long period of time, one can solve the RTE for the direction-dependent specific intensity column vector and then integrate the direction-weighted specific intensity over all directions. Furthermore, we demonstrate that the specific intensity (or specific intensity column vector) can be measured with a well-collimated radiometer (photopolarimeter), which provides the ultimate physical justification for the use of such instruments in radiation-budget and particle-characterization applications. However, the specific intensity cannot be interpreted in phenomenological terms as signifying the amount of elec-tromagnetic energy transported in a given direction per unit area normal to this direction per unit time per unit solid angle. Also, in the case of a densely packed scattering medium the relation of the measurement with a well-collimated radiometer to the time-averaged local Poynting vector re-mains uncertain, and the theoretical modeling of this measurement is likely to require a much more complicated approach than solving an RTE.

A numerical and experimental investigation of the thermal control performance of a spaceborne compressor assembly

NASA Astrophysics Data System (ADS)

Oh, Hyun-Ung; Lee, Min-Kyu; Shin, Somin; Hong, Joo-Sung

2011-09-01

Spaceborne pulse tube type cryocoolers are widely used for providing cryogenic temperatures for sensitive infrared, gamma-ray and X-ray detectors. Thermal control for the compressor of the cryocooler is one of the important technologies for the cooling performance, mission life time, and jitter stability of the cooler. The thermal design of the compressor assembly proposed in this study is basically composed of a heat pipe, a radiator, and a heater. In the present work, a method for heat pipe implementation is proposed and investigated to ensure the jitter stability of the compressor under the condition that one heat pipe is not working. An optimal design of the radiator that uses ribs for effective use by minimizing the temperature gradient on the radiator and reducing its weight is introduced. The effectiveness of the thermal design of the compressor assembly is demonstrated by on-orbit thermal analysis using the correlated thermal model obtained from the thermal balance test that is performed under a space simulating environment.

Particle acceleration, magnetic field generation, and emission in relativistic pair jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Kouveliotou, C.; Fishman, G. J.; Mizuno, Y.

2005-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Recent simulations show that the Weibel instability created by relativistic pair jets is responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet propagating through an ambient plasma with and without initial magnetic fields. The growth rates of the Weibel instability depends on the distribution of pair jets. The Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. This instability is also responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron s transverse deflection behind the jet head. The jitter radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Cancer Vaccines: Moving Beyond Current Paradigms

PubMed Central

Schlom, Jeffrey; Arlen, Philip M.; Gulley, James L.

2008-01-01

The field of cancer vaccines is currently in an active state of preclinical and clinical investigations. While no therapeutic cancer vaccine has to date been approved by the FDA, several new paradigms are emerging from recent clinical findings in both the use of combination therapy approaches and, perhaps more importantly, in clinical trial design and endpoint analyses. This paper will review recent clinical trials involving several different cancer vaccines from which data are emerging contrasting classical “tumor response” (RECIST) criteria with “patient response” in the manifestation of increased patient survival post-vaccine therapy. Also described are several strategies in which cancer vaccines can be exploited in combination with other agents and therapeutic modalities that are quite unique when compared with “conventional” combination therapies. This is most likely due to the phenomena that (a) cancer vaccines initiate a dynamic immune process that can be exploited in subsequent therapies, and (b) both radiation and certain chemotherapeutic agents have been shown to alter the phenotype of tumor cells as to render them more susceptible to T-cell–mediated killing. Consequently, evidence is emerging from several studies in which patient cohorts who first receive a cancer vaccine (as contrasted with control cohorts) benefit clinically from subsequent therapies. PMID:17606707

Current external beam radiation therapy quality assurance guidance: does it meet the challenges of emerging image-guided technologies?

PubMed

Palta, Jatinder R; Liu, Chihray; Li, Jonathan G

2008-01-01

The traditional prescriptive quality assurance (QA) programs that attempt to ensure the safety and reliability of traditional external beam radiation therapy are limited in their applicability to such advanced radiation therapy techniques as three-dimensional conformal radiation therapy, intensity-modulated radiation therapy, inverse treatment planning, stereotactic radiosurgery/radiotherapy, and image-guided radiation therapy. The conventional QA paradigm, illustrated by the American Association of Physicists in Medicine Radiation Therapy Committee Task Group 40 (TG-40) report, consists of developing a consensus menu of tests and device performance specifications from a generic process model that is assumed to apply to all clinical applications of the device. The complexity, variation in practice patterns, and level of automation of high-technology radiotherapy renders this "one-size-fits-all" prescriptive QA paradigm ineffective or cost prohibitive if the high-probability error pathways of all possible clinical applications of the device are to be covered. The current approaches to developing comprehensive prescriptive QA protocols can be prohibitively time consuming and cost ineffective and may sometimes fail to adequately safeguard patients. It therefore is important to evaluate more formal error mitigation and process analysis methods of industrial engineering to more optimally focus available QA resources on process components that have a significant likelihood of compromising patient safety or treatment outcomes.

Underlying Paradigms in Student Affairs Research and Practice

ERIC Educational Resources Information Center

Guido, Florence M.; Chavez, Alicia Fedelina; Lincoln, Yvonna S.

2010-01-01

Student affairs professionals benefit from understanding paradigms, worldviews, and ways of being among diverse faculty, staff, and students. It is challenging to understand core differences of paradigms, design student affairs practice and research in congruence with or across specific philosophies, and work effectively with individuals operating…

The prevalence of disability among children: paradigms and estimates.

PubMed

Mudrick, Nancy R

2002-11-01

Every examination of disability among children must first grapple with definition of disability. The challenges to identifying disability among children involve not only determining the appropriate paradigm for defining disability, but also applying that paradigm to children in a meaningful way. This discussion of the prevalence of disability among children starts by examining the various paradigms utilized to identify disability and how they are interpreted when applied to children. Estimates of the prevalence of childhood disability, under different definitions of disability are presented. The goal of the discussion is to illustrate the sensitivity of the estimates of disability prevalence to the particular definition and data set used. Finally, the potential influence of the choice of paradigm on further measurement and service delivery is outlined.

Scaling, Similarity, and the Fourth Paradigm for Hydrology

NASA Technical Reports Server (NTRS)

Peters-Lidard, Christa D.; Clark, Martyn; Samaniego, Luis; Verhoest, Niko E. C.; van Emmerik, Tim; Uijlenhoet, Remko; Achieng, Kevin; Franz, Trenton E.; Woods, Ross

2017-01-01

In this synthesis paper addressing hydrologic scaling and similarity, we posit that roadblocks in the search for universal laws of hydrology are hindered by our focus on computational simulation (the third paradigm), and assert that it is time for hydrology to embrace a fourth paradigm of data-intensive science. Advances in information-based hydrologic science, coupled with an explosion of hydrologic data and advances in parameter estimation and modelling, have laid the foundation for a data-driven framework for scrutinizing hydrological scaling and similarity hypotheses. We summarize important scaling and similarity concepts (hypotheses) that require testing, describe a mutual information framework for testing these hypotheses, describe boundary condition, state flux, and parameter data requirements across scales to support testing these hypotheses, and discuss some challenges to overcome while pursuing the fourth hydrological paradigm. We call upon the hydrologic sciences community to develop a focused effort towards adopting the fourth paradigm and apply this to outstanding challenges in scaling and similarity.

Addiction: the urgent need for a paradigm shift.

PubMed

Alexander, Bruce K

2012-01-01

Severe addictions to drug use and to countless other habits are causing enormous harm around the globe. Massive expenditures and dedicated efforts of police, doctors, addiction therapists, and self-help groups have failed to bring the problem under control, although many individual addicts have been helped. What can society do when our best efforts continue to fail and a menacing problem continues to grow? This paper proposes that a major paradigm shift is required. The currently dominant paradigm assumes that addiction is either an individual disease or an individual moral breach. But this individually oriented paradigm has failed. Instead, addiction needs to be understood socially, as a way that large numbers of people adapt to the breakdown of psychologically sustaining culture under the global influence of free-market society. This new paradigm is based on the social thinking of Karl Polanyi and other social scientists rather than on the individual thinking of neuroscientists, doctors, or psychologists.

Policy Dispute and Paradigm Evaluation: A Response to Rowland.

ERIC Educational Resources Information Center

Lichtman, Allan J.; Rohrer, Daniel M.

1982-01-01

Responds to Rowland's article, (CS 705 841). Contends that policy systems analysis emerges as the only acceptable paradigm for competitive debate and that it satisfies the criteria for paradigm evaluation. (PD)

A comparison among several P300 brain-computer interface speller paradigms.

PubMed

Fazel-Rezai, Reza; Gavett, Scott; Ahmad, Waqas; Rabbi, Ahmed; Schneider, Eric

2011-10-01

Since the brain-computer interface (BCI) speller was first proposed by Farwell and Donchin, there have been modifications in the visual aspects of P300 paradigms. Most of the changes are based on the original matrix format such as changes in the number of rows and columns, font size, flash/ blank time, and flash order. The improvement in the resulting accuracy and speed of such systems has always been the ultimate goal. In this study, we have compared several different speller paradigms including row-column, single character flashing, and two region-based paradigms which are not based on the matrix format. In the first region-based paradigm, at the first level, characters and symbols are distributed over seven regions alphabetically, while in the second region-based paradigm they are distributed in the most frequently used order. At the second level, each one of the regions is further subdivided into seven subsets. The experimental results showed that the average accuracy and user acceptability for two region-based paradigms were higher than those for traditional paradigms such as row/column and single character.

A Case-Conference Exercise to Facilitate Understanding of Paradigms in Abnormal Psychology

ERIC Educational Resources Information Center

Lafosse, Jose M.; Zinser, Michael C.

2002-01-01

In this article we describe an in-class case-conference exercise designed to enhance the teaching of paradigms in abnormal psychology courses. The primary pedagogical goals are to increase awareness of how paradigms are applied in real-life settings; better distinguish between paradigms; and recognize how paradigms influence understanding of…

A NOVEL EMISSION SPECTRUM FROM A RELATIVISTIC ELECTRON MOVING IN A RANDOM MAGNETIC FIELD

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

Teraki, Yuto; Takahara, Fumio, E-mail: teraki@vega.ess.sci.osaka-u.ac.jp

2011-07-10

We numerically calculate the radiation spectrum from relativistic electrons moving in small-scale turbulent magnetic fields expected in high-energy astrophysical sources. Such a radiation spectrum is characterized by the strength parameter a = {lambda}{sub B} e|B|/mc {sup 2}, where {lambda}{sub B} is the length scale of the turbulent field. When a is much larger than the Lorentz factor of a radiating electron {gamma}, synchrotron radiation is realized, while a << 1 corresponds to the so-called jitter radiation regime. Because for 1 < a < {gamma} we cannot use either approximations, we should have recourse to the Lienard-Wiechert potential to evaluate themore » radiation spectrum, which is performed in this Letter. We generate random magnetic fields assuming Kolmogorov turbulence, inject monoenergetic electrons, solve the equation of motion, and calculate the radiation spectrum. We perform numerical calculations for several values of a with {gamma} = 10. We obtain various types of spectra ranging between jitter radiation and synchrotron radiation. For a {approx} 7, the spectrum takes a novel shape which had not been noticed up to now. It is like a synchrotron spectrum in the middle energy region, but in the low frequency region it is a broken power law and in the high frequency region an extra power-law component appears beyond the synchrotron cutoff. We give a physical explanation of these features.« less

Negative pressure darwinism: survival of the fittest paradigm.

PubMed

Miller, Michael; Bybordi, Farhad

2009-07-01

The use of negative pressure for wound healing has been based on a set of parameters and devices that until recently were combined into a single paradigm. Despite historical and more recent evidence providing viable alternative considerations, it is only recently that this paradigm and its tenets have come into question. As the understanding of the limits of the current paradigm and specific instances of its benefits and drawbacks are identified, shifts in the paradigm must take place if the therapy is to evolve, develop, and continue to be efficacious. The pertinence of the concept of survival of the fittest is used to explore the need for a paradigm shift in negative pressure wound therapy.

Bayesian evidence and predictivity of the inflationary paradigm

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

Gubitosi, Giulia; Lagos, Macarena; Magueijo, João

In this paper we consider the issue of paradigm evaluation by applying Bayes' theorem along the following nested hierarchy of progressively more complex structures: i) parameter estimation (within a model), ii) model selection and comparison (within a paradigm), iii) paradigm evaluation. In such a hierarchy the Bayesian evidence works both as the posterior's normalization at a given level and as the likelihood function at the next level up. Whilst raising no objections to the standard application of the procedure at the two lowest levels, we argue that it should receive a considerable modification when evaluating paradigms, when testability and fittingmore » data are equally important. By considering toy models we illustrate how models and paradigms that are difficult to falsify are always favoured by the Bayes factor. We argue that the evidence for a paradigm should not only be high for a given dataset, but exceptional with respect to what it would have been, had the data been different. With this motivation we propose a measure which we term predictivity , as well as a prior to be incorporated into the Bayesian framework, penalising unpredictivity as much as not fitting data. We apply this measure to inflation seen as a whole, and to a scenario where a specific inflationary model is hypothetically deemed as the only one viable as a result of information alien to cosmology (e.g. Solar System gravity experiments, or particle physics input). We conclude that cosmic inflation is currently hard to falsify, but that this could change were external/additional information to cosmology to select one of its many models. We also compare this state of affairs to bimetric varying speed of light cosmology.« less

Paradigms of School Change

ERIC Educational Resources Information Center

Wrigley, Terry

2011-01-01

This short paper points to some paradigm issues in the field of school development (leadership, effectiveness, improvement) and their relationship to social justice. It contextualises the dominant School Effectiveness and School Improvement models within neo-liberal marketisation, paying attention to their transformation through a "marriage of…

In Search of a Paradigm for Bilingual Education.

ERIC Educational Resources Information Center

Aquirre, Adalberto, Jr.

The success of a new paradigm depends upon the level of coherency and organization within its supporting community, and Thomas Kuhn's argument concerning the resistance to new paradigms and their power to change the existing order can be used in the context of bilingual education. Bilingual education programs have the potential to create a…

A new paradigm for predicting zonal-mean climate and climate change

NASA Astrophysics Data System (ADS)

Armour, K.; Roe, G.; Donohoe, A.; Siler, N.; Markle, B. R.; Liu, X.; Feldl, N.; Battisti, D. S.; Frierson, D. M.

2016-12-01

How will the pole-to-equator temperature gradient, or large-scale patterns of precipitation, change under global warming? Answering such questions typically involves numerical simulations with comprehensive general circulation models (GCMs) that represent the complexities of climate forcing, radiative feedbacks, and atmosphere and ocean dynamics. Yet, our understanding of these predictions hinges on our ability to explain them through the lens of simple models and physical theories. Here we present evidence that zonal-mean climate, and its changes, can be understood in terms of a moist energy balance model that represents atmospheric heat transport as a simple diffusion of latent and sensible heat (as a down-gradient transport of moist static energy, with a diffusivity coefficient that is nearly constant with latitude). We show that the theoretical underpinnings of this model derive from the principle of maximum entropy production; that its predictions are empirically supported by atmospheric reanalyses; and that it successfully predicts the behavior of a hierarchy of climate models - from a gray radiation aquaplanet moist GCM, to comprehensive GCMs participating in CMIP5. As an example of the power of this paradigm, we show that, given only patterns of local radiative feedbacks and climate forcing, the moist energy balance model accurately predicts the evolution of zonal-mean temperature and atmospheric heat transport as simulated by the CMIP5 ensemble. These results suggest that, despite all of its dynamical complexity, the atmosphere essentially responds to energy imbalances by simply diffusing latent and sensible heat down-gradient; this principle appears to explain zonal-mean climate and its changes under global warming.

The Global Imperatives for an Education Paradigm Shift.

ERIC Educational Resources Information Center

Bright, Larry K.; And Others

The future role of education is covered in a discussion concerning the shifting of the dominant social paradigm of the United States. It is noted that the paradigm is changing from one that requires social institutions to seek and develop human resources to maintain a position of competitive dominance, to an emerging view of world interdependence.…

The World Religions Paradigm Time for a Change

ERIC Educational Resources Information Center

Owen, Suzanne

2011-01-01

The teaching of religions has long relied on the World Religions paradigm to guide curricula throughout education, which has led to a widening gap, on the one hand, between what is taught in schools and in universities and, on the other, between research and teaching. While the World Religions paradigm has allowed the inclusion of non-Christian…

Cortex and Memory: Emergence of a New Paradigm

ERIC Educational Resources Information Center

Fuster, Joaquin M.

2009-01-01

Converging evidence from humans and nonhuman primates is obliging us to abandon conventional models in favor of a radically different, distributed-network paradigm of cortical memory. Central to the new paradigm is the concept of memory network or cognit--that is, a memory or an item of knowledge defined by a pattern of connections between neuron…

Deconstructing Research: Paradigms Lost

ERIC Educational Resources Information Center

Trifonas, Peter Pericles

2009-01-01

In recent decades, proponents of naturalistic and/or critical modes of inquiry advocating the use of ethnographic techniques for the narrative-based study of phenomena within pedagogical contexts have challenged the central methodological paradigm of educational research: that is, the tendency among its practitioners to adhere to quantitative…

Alternative Evaluation Research Paradigm.

ERIC Educational Resources Information Center

Patton, Michael Quinn

This monograph is one of a continuing series initiated to provide materials for teachers, parents, school administrators, and governmental decision-makers that might encourage reexamination of a range of evaluation issues and perspectives about schools and schooling. This monograph is a description and analysis of two contrasting paradigms: one…

Paradigms: examples from the bacterium Xylella fastidiosa.

PubMed

Purcell, Alexander

2013-01-01

The history of advances in research on Xylella fastidiosa provides excellent examples of how paradigms both advance and limit our scientific understanding of plant pathogens and the plant diseases they cause. I describe this from a personal perspective, having been directly involved with many persons who made paradigm-changing discoveries, beginning with the discovery that a bacterium, not a virus, causes Pierce's disease of grape and other plant diseases in numerous plant species, including important crop and forest species.

Language-learning disabilities: Paradigms for the nineties.

PubMed

Wiig, E H

1991-01-01

We are beginning a decade, during which many traditional paradigms in education, special education, and speech-language pathology will undergo change. Among paradigms considered promising for speech-language pathology in the schools are collaborative language intervention and strategy training for language and communication. This presentation introduces management models for developing a collaborative language intervention process, among them the Deming Management Method for Total Quality (TQ) (Deming 1986). Implementation models for language assessment and IEP planning and multicultural issues are also introduced (Damico and Nye 1990; Secord and Wiig in press). While attention to processes involved in developing and implementing collaborative language intervention is paramount, content should not be neglected. To this end, strategy training for language and communication is introduced as a viable paradigm. Macro- and micro-level process models for strategy training are featured and general issues are discussed (Ellis, Deshler, and Schumaker 1989; Swanson 1989; Wiig 1989).

Voluntary saccadic eye movements in humans studied with a double-cue paradigm.

PubMed

Sheliga, B M; Brown, V J; Miles, F A

2002-07-01

In the classic double-step paradigm, subjects are required to make a saccade to a visual target that is briefly presented at one location and then shifted to a new location before the subject has responded. The saccades in this situation are "reflexive" in that they are made in response to the appearance of the target itself. In the present experiments we adapted the double-step paradigm to study "voluntary" saccades. For this, several identical targets were always visible and subjects were given a cue to indicate that they should make a saccade to one of them. This cue was then changed to indicate another of the targets before the subject had responded: double-cue (DC) paradigm. The saccadic eye movements in our DC paradigm had many features in common with those in the double-step paradigm and we show that apparent differences can be attributed to the spatio-temporal arrangements of the cues/targets rather than to any intrinsic differences in the programming of these two kinds of eye movements. For example, a feature of our DC paradigm that is not seen in the usual double-step paradigm is that the second cue could cause transient delays of the initial saccade, and these delays still occurred when the second cue was reflexive--provided that it was at the fovea (as in our DC paradigm) and not in the periphery (as in the usual double-step paradigm). Thus, the critical factor for the delay was the retinal (foveal) location of the second cue/target--not whether it was cognitive or reflexive--and we argue that the second cue/target is here acting as a distractor. We conclude that the DC paradigm can be used to study the programming of voluntary saccades in the same way that the double-step paradigm can be used to study reflexive saccades.

Muscle, bone, and the Utah paradigm: a 1999 overview.

PubMed

Frost, H M

2000-05-01

The still-evolving Utah paradigm of skeletal physiology supplements former ideas about the control of postnatal bone strength and "mass" in health and disease, on earth and in orbit, and as functions of physical activities including sports. In its view, peak muscle forces on bone dominate control of the biologic mechanisms that control changes in our postnatal whole-bone strength and mass. This contrasts with former ideas that chiefly nonmechanical factors dominate that control and mechanical factors have little influence on it. The newer view begs the question of how such a bone-muscle relationship would work, and the Utah paradigm offers plausible explanations for that. Whereas many biomechanicians, orthopedists, and sports medicine experts might find the newer view sensible, some people in other disciplines may not. This article summarizes some evidence that support the Utah paradigm and the above-stated view and explores some of the paradigm's features and implications.

Breast Imaging: A Paradigm for Accountable Care Organizations.

PubMed

Parikh, Jay R; Yang, Wei T

2016-02-01

Accountable care organizations (ACOs) are being promoted by the Centers of Medicare Services as alternative payment models for radiology reimbursement. Because of its clinical orientation, focus on prevention, standardized reporting, quality orientation through mandatory accreditation, and value demonstration through established outcome metrics, breast imaging offers a unique paradigm for the ACO model in radiology. In radiology, breast imaging represents the paradigm for ACOs.

Paradigms, Citations, and Maps of Science: A Personal History.

ERIC Educational Resources Information Center

Small, Henry

2003-01-01

Discusses mapping science and Kuhn's theories of paradigms and scientific development. Highlights include cocitation clustering; bibliometric definition of a paradigm; specialty dynamics; pathways through science; a new Web tool called Essential Science Indicators (ESI) for studying the structure of science; and microrevolutions. (Author/LRW)

Contemporary paradigms for research related to women's mental health.

PubMed

Doucet, Shelley Anne; Letourneau, Nicole Lyn; Stoppard, Janet M

2010-04-01

Mental health problems are serious health concerns that affect women across diverse settings internationally. Knowledge of this population historically has been informed by research using a positivist approach. This article is a critical examination of contemporary paradigms for research related to women's mental health. We begin the article with an introduction to women's mental health, followed by an overview of the postpositivist, critical theory, and constructivist paradigms. We then present a critical examination of the benefits and limitations of these paradigms in relation to the study of women's mental health. We conclude with implications for research and practice.

Paradigms for Realizing Machine Learning Algorithms.

PubMed

Agneeswaran, Vijay Srinivas; Tonpay, Pranay; Tiwary, Jayati

2013-12-01

The article explains the three generations of machine learning algorithms-with all three trying to operate on big data. The first generation tools are SAS, SPSS, etc., while second generation realizations include Mahout and RapidMiner (that work over Hadoop), and the third generation paradigms include Spark and GraphLab, among others. The essence of the article is that for a number of machine learning algorithms, it is important to look beyond the Hadoop's Map-Reduce paradigm in order to make them work on big data. A number of promising contenders have emerged in the third generation that can be exploited to realize deep analytics on big data.

[Reconstituting evaluation methods based on both qualitative and quantitative paradigms].

PubMed

Miyata, Hiroaki; Okubo, Suguru; Yoshie, Satoru; Kai, Ichiro

2011-01-01

Debate about the relationship between quantitative and qualitative paradigms is often muddled and confusing and the clutter of terms and arguments has resulted in the concepts becoming obscure and unrecognizable. In this study we conducted content analysis regarding evaluation methods of qualitative healthcare research. We extracted descriptions on four types of evaluation paradigm (validity/credibility, reliability/credibility, objectivity/confirmability, and generalizability/transferability), and classified them into subcategories. In quantitative research, there has been many evaluation methods based on qualitative paradigms, and vice versa. Thus, it might not be useful to consider evaluation methods of qualitative paradigm are isolated from those of quantitative methods. Choosing practical evaluation methods based on the situation and prior conditions of each study is an important approach for researchers.

A nonmusical paradigm for identifying absolute pitch possessors

NASA Astrophysics Data System (ADS)

Ross, David A.; Olson, Ingrid R.; Marks, Lawrence E.; Gore, John C.

2004-09-01

The ability to identify and reproduce sounds of specific frequencies is remarkable and uncommon. The etiology and defining characteristics of this skill, absolute pitch (AP), have been very controversial. One theory suggests that AP requires a specific type of early musical training and that the ability to encode and remember tones depends on these learned musical associations. An alternate theory argues that AP may be strongly dependent on hereditary factors and relatively independent of musical experience. To date, it has been difficult to test these hypotheses because all previous paradigms for identifying AP have required subjects to employ knowledge of musical nomenclature. As such, these tests are insensitive to the possibility of discovering AP in either nonmusicians or musicians of non-Western training. Based on previous literature in pitch memory, a paradigm is presented that is intended to distinguish between AP possessors and nonpossessors independent of the subjects' musical experience. The efficacy of this method is then tested with 20 classically defined AP possessors and 22 nonpossessors. Data from these groups strongly support the validity of the paradigm. The use of a nonmusical paradigm to identify AP may facilitate research into many aspects of this phenomenon.

A nonmusical paradigm for identifying absolute pitch possessors.

PubMed

Ross, David A; Olson, Ingrid R; Marks, Lawrence E; Gore, John C

2004-09-01

The ability to identify and reproduce sounds of specific frequencies is remarkable and uncommon. The etiology and defining characteristics of this skill, absolute pitch (AP), have been very controversial. One theory suggests that AP requires a specific type of early musical training and that the ability to encode and remember tones depends on these learned musical associations. An alternate theory argues that AP may be strongly dependent on hereditary factors and relatively independent of musical experience. To date, it has been difficult to test these hypotheses because all previous paradigms for identifying AP have required subjects to employ knowledge of musical nomenclature. As such, these tests are insensitive to the possibility of discovering AP in either nonmusicians or musicians of non-Western training. Based on previous literature in pitch memory, a paradigm is presented that is intended to distinguish between AP possessors and nonpossessors independent of the subjects' musical experience. The efficacy of this method is then tested with 20 classically defined AP possessors and 22 nonpossessors. Data from these groups strongly support the validity of the paradigm. The use of a nonmusical paradigm to identify AP may facilitate research into many aspects of this phenomenon.

Optimized Motor Imagery Paradigm Based on Imagining Chinese Characters Writing Movement.

PubMed

Qiu, Zhaoyang; Allison, Brendan Z; Jin, Jing; Zhang, Yu; Wang, Xingyu; Li, Wei; Cichocki, Andrzej

2017-07-01

motor imagery (MI) is a mental representation of motor behavior. The MI-based brain computer interfaces (BCIs) can provide communication for the physically impaired. The performance of MI-based BCI mainly depends on the subject's ability to self-modulate electroencephalogram signals. Proper training can help naive subjects learn to modulate brain activity proficiently. However, training subjects typically involve abstract motor tasks and are time-consuming. to improve the performance of naive subjects during motor imagery, a novel paradigm was presented that would guide naive subjects to modulate brain activity effectively. In this new paradigm, pictures of the left or right hand were used as cues for subjects to finish the motor imagery task. Fourteen healthy subjects (11 male, aged 22-25 years, and mean 23.6±1.16) participated in this study. The task was to imagine writing a Chinese character. Specifically, subjects could imagine hand movements corresponding to the sequence of writing strokes in the Chinese character. This paradigm was meant to find an effective and familiar action for most Chinese people, to provide them with a specific, extensively practiced task and help them modulate brain activity. results showed that the writing task paradigm yielded significantly better performance than the traditional arrow paradigm (p < 0.001). Questionnaire replies indicated that most subjects thought that the new paradigm was easier. the proposed new motor imagery paradigm could guide subjects to help them modulate brain activity effectively. Results showed that there were significant improvements using new paradigm, both in classification accuracy and usability.

The Fate of the Method of 'Paradigms' in Paleobiology.

PubMed

Rudwick, Martin J S

2017-11-02

An earlier article described the mid-twentieth century origins of the method of "paradigms" in paleobiology, as a way of making testable hypotheses about the functional morphology of extinct organisms. The present article describes the use of "paradigms" through the 1970s and, briefly, to the end of the century. After I had proposed the paradigm method to help interpret the ecological history of brachiopods, my students developed it in relation to that and other invertebrate phyla, notably in Euan Clarkson's analysis of vision in trilobites. David Raup's computer-aided "theoretical morphology" was then combined with my functional or adaptive emphasis, in Adolf Seilacher's tripartite "constructional morphology." Stephen Jay Gould, who had strongly endorsed the method, later switched to criticizing the "adaptationist program" he claimed it embodied. Although the explicit use of paradigms in paleobiology had declined by the end of the century, the method was tacitly subsumed into functional morphology as "biomechanics."

Exploring paradigms in postpartum depression research: the need for feminist pragmatism.

PubMed

Mollard, Elizabeth

2015-01-01

Postpartum depression (PPD) is an important area of women's health research internationally and across disciplines. There is no guiding paradigm, however, to ensure that PPD research results translate to women on a global level. This commentary builds on the work of Doucet, Letourneau, and Stoppard ( 2010 ) to determine a "best fit" paradigm with which to guide PPD research. Postpositivism, critical theory, constructivism, and pragmatism are combined with a feminist ideology and critiqued as potential guiding paradigms for PPD research. After thorough examination, I conclude the need for further use of a feminist pragmatist paradigm in PPD research.

Role of semantic paradigms for optimization of language mapping in clinical FMRI studies.

PubMed

Zacà, D; Jarso, S; Pillai, J J

2013-10-01

The optimal paradigm choice for language mapping in clinical fMRI studies is challenging due to the variability in activation among different paradigms, the contribution to activation of cognitive processes other than language, and the difficulties in monitoring patient performance. In this study, we compared language localization and lateralization between 2 commonly used clinical language paradigms and 3 newly designed dual-choice semantic paradigms to define a streamlined and adequate language-mapping protocol. Twelve healthy volunteers performed 5 language paradigms: Silent Word Generation, Sentence Completion, Visual Antonym Pair, Auditory Antonym Pair, and Noun-Verb Association. Group analysis was performed to assess statistically significant differences in fMRI percentage signal change and lateralization index among these paradigms in 5 ROIs: inferior frontal gyrus, superior frontal gyrus, middle frontal gyrus for expressive language activation, middle temporal gyrus, and superior temporal gyrus for receptive language activation. In the expressive ROIs, Silent Word Generation was the most robust and best lateralizing paradigm (greater percentage signal change and lateralization index than semantic paradigms at P < .01 and P < .05 levels, respectively). In the receptive region of interest, Sentence Completion and Noun-Verb Association were the most robust activators (greater percentage signal change than other paradigms, P < .01). All except Auditory Antonym Pair were good lateralizing tasks (the lateralization index was significantly lower than other paradigms, P < .05). The combination of Silent Word Generation and ≥1 visual semantic paradigm, such as Sentence Completion and Noun-Verb Association, is adequate to determine language localization and lateralization; Noun-Verb Association has the additional advantage of objective monitoring of patient performance.

Paradigms: How Far Does Research in Distributed Leadership "Stretch"?

ERIC Educational Resources Information Center

Hartley, David

2010-01-01

Burrell and Morgan's widely-cited "Sociological Paradigms and Organizational Analysis" is applied here to research on distributed leadership in education. Nearly all of the extant research is regulatory, not radical; and the evidence which it has generated falls broadly within the paradigm of interpretivism. Few studies have generated the…

The "New Environmental Paradigm"

ERIC Educational Resources Information Center

Dunlap, Riley E.; Van Liere, Kent D.

2008-01-01

The "New Environmental Paradigm" or NEP appears to have gained considerable popularity in academic and intellectual circles, as well as among many college students; however, very little is known concerning the degree to which the general public has come to accept the ideas embodied in it. Thus, although there have been dozens of studies…

Poverty eradication: a new paradigm.

PubMed

Pethe, V P

1998-08-01

This article offers a new paradigm for eradicating poverty in India. It was assumed incorrectly by Mahatma Gandhi that a good society without mass poverty would follow after independence. India copied Western models of development and developed giant factories, big dams, and megacities. Agriculture did not expand the number of jobs for people. The Western paradigm failed in India because of the false assumption of "trickle down" of income to the masses. The targeted programs to the poor did not directly benefit enough of the poor. Mega-industrialization led to reduced employment and higher skill needs. The model failed mainly because it was a proxy and relied on indirect ways of reaching the poor. The models failed to be adapted to conditions in India. The Swadeshi paradigm is a direct model for addressing mass poverty. Poverty is affected by immediate, intermediate, and ultimate determinants. Poverty begets social and economic problems, such as ignorance, ill health, high fertility, unemployment, and crime. In India and developing countries, mass poverty results from under use of human resources; lack of equal opportunities; and an outdated non-egalitarian social structure, an unjust global economic order, human cruelty, and erosion of ethical values. Indians are squandering their precious resources mimicking Western consumerism. Poverty leads to rapid population growth. People become productive assets with universal literacy, compulsory and free education, health services and sanitation, vocational training, and work ethics. India needs people-oriented policies with less emphasis on capital accumulation.

The Newtonian Mechanistic Paradigm, Special Education, and Contours of Alternatives: An Overview.

ERIC Educational Resources Information Center

Heshusius, Lous

1989-01-01

The article examines theoretical reorientations in special education away from the Newtonian mechanistic paradigm toward an emerging holistic paradigm. Recent literature is critiqued for renaming theories as paradigms, thereby providing an illusion of change while leaving fundamental mechanistic assumptions in place. (Author/DB)

Four paradigms: traffic safety in the twentieth-century United States.

PubMed

Norton, Peter

2015-04-01

Traffic safety, once neglected within the larger history of the automobile in the United States, has finally been getting the attention it always deserved. Nevertheless, historians still sometimes misappraise traffic safety in one era by the standards of another. Ahistorical assumptions have contributed to misinterpretations-for example, that Americans of the 1920s were extraordinarily tolerant of traffic casualties because they did not respond to them as more recent traffic-safety paradigms would prescribe. As a corrective, four paradigms, approximately sequential, are proposed: Safety First, Control, Crashworthiness, and Responsibility. Historians are invited to borrow, modify, or replace them, and to consider their applicability to other countries. Whether these particular paradigms survive review or not, historians who are alert to safety paradigms will produce more reliable scholarship on the history of traffic safety.

Paradigms, Exemplars and Social Change

ERIC Educational Resources Information Center

Lawson, Hal A.

2009-01-01

Researchers' social-cultural organization influences the scope, quality, quantity, coherence, dissemination, utilization and impact of research-based, theoretically sound knowledge. Five concepts--paradigm, exemplar, segment, network and gatekeeper--are salient to research on researchers' organization. Autobiographical reflections signal these…

Different Research Paradigms Concerning Giftedness and Gifted Education: Shall Ever They Meet?

ERIC Educational Resources Information Center

Heller, Kurt A.

2012-01-01

Knowledge regarding giftedness and gifted education is supplied by different sources of information and different research paradigms. Particularly relevant approaches are here the psychometric paradigm, the expert-novice paradigm, and the explanatory approaches from cognitive sciences, also the quasi-experimental social and developmental studies…

Toward a Quality-of-Life Paradigm for Sustainable Communities.

ERIC Educational Resources Information Center

Hyman, Drew

This paper suggests that current paradigms and world views guiding research for social action are inadequate for directing rural community change in a high-tech, global community. For several generations, the agrarian and industrial paradigms have been accepted as appropriate for guiding social change and development. However, there are problems…

The Learner-Centered Paradigm of Education: Roles for Technology

ERIC Educational Resources Information Center

Reigeluth, Charles M.

2014-01-01

The learner-centered paradigm of education requires very different roles for technology, as well as for teachers and students, compared with the teacher-centered paradigm. Rather than almost exclusively serving the teacher for teaching, technology primarily serves the student for learning. It does so through four major roles: (1) keeping records…

Interaction between Social Categories in the Composite Face Paradigm

ERIC Educational Resources Information Center

Chen, Wenfeng; Ren, Naixin; Young, Andrew W.; Liu, Chang Hong

2018-01-01

The composite face paradigm (Young, Hellawell, & Hay, 1987) is widely used to demonstrate holistic perception of faces (Rossion, 2013). In the paradigm, parts from different faces (usually the top and bottom halves) are recombined. The principal criterion for holistic perception is that responses involving the component parts of composites in…

Are leader stereotypes masculine? A meta-analysis of three research paradigms.

PubMed

Koenig, Anne M; Eagly, Alice H; Mitchell, Abigail A; Ristikari, Tiina

2011-07-01

This meta-analysis examined the extent to which stereotypes of leaders are culturally masculine. The primary studies fit into 1 of 3 paradigms: (a) In Schein's (1973) think manager-think male paradigm, 40 studies with 51 effect sizes compared the similarity of male and leader stereotypes and the similarity of female and leader stereotypes; (b) in Powell and Butterfield's (1979) agency-communion paradigm, 22 studies with 47 effect sizes compared stereotypes of leaders' agency and communion; and (c) in Shinar's (1975) masculinity-femininity paradigm, 7 studies with 101 effect sizes represented stereotypes of leadership-related occupations on a single masculinity-femininity dimension. Analyses implemented appropriate random and mixed effects models. All 3 paradigms demonstrated overall masculinity of leader stereotypes: (a) In the think manager-think male paradigm, intraclass correlation = .25 for the women-leaders similarity and intraclass correlation = .62 for the men-leaders similarity; (b) in the agency-communion paradigm, g = 1.55, indicating greater agency than communion; and (c) in the masculinity-femininity paradigm, g = 0.92, indicating greater masculinity than the androgynous scale midpoint. Subgroup and meta-regression analyses indicated that this masculine construal of leadership has decreased over time and was greater for male than female research participants. In addition, stereotypes portrayed leaders as less masculine in educational organizations than in other domains and in moderate- than in high-status leader roles. This article considers the relation of these findings to Eagly and Karau's (2002) role congruity theory, which proposed contextual influences on the incongruity between stereotypes of women and leaders. The implications for prejudice against women leaders are also considered.

Parallel Programming Paradigms

DTIC Science & Technology

1987-07-01

Unclassified IS.. DECLASSIFICATIONIOOWNGRADIN G 16. DISTRIBUTION STATEMENT (of this Report) Distribution of this report is unlimited. 17...8416878 and by the Office of Naval Research Contracts No. N00014-86-K-0264 and No. N00014-85- K-0328. 8 ?~~ O . G 1 49 II Parallel Programming Paradigms...processors -. "to fetch from the same memory cell (list head) and thus seems to favor a shared memory - g implementation [37). In this dissertation, we

[Artificial intelligence applied to radiation oncology].

PubMed

Bibault, J-E; Burgun, A; Giraud, P

2017-05-01

Performing randomised comparative clinical trials in radiation oncology remains a challenge when new treatment modalities become available. One of the most recent examples is the lack of phase III trials demonstrating the superiority of intensity-modulated radiation therapy in most of its current indications. A new paradigm is developing that consists in the mining of large databases to answer clinical or translational issues. Beyond national databases (such as SEER or NCDB), that often lack the necessary level of details on the population studied or the treatments performed, electronic health records can be used to create detailed phenotypic profiles of any patients. In parallel, the Record-and-Verify Systems used in radiation oncology precisely document the planned and performed treatments. Artificial Intelligence and machine learning algorithms can be used to incrementally analyse these data in order to generate hypothesis to better personalize treatments. This review discusses how these methods have already been used in previous studies. Copyright © 2017 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

Disability Is Not Measles: New Research Paradigms in Disability.

ERIC Educational Resources Information Center

Rioux, Marcia H., Ed.; Bach, Michael, Ed.

This book is the product of a forum titled New Research Directions and Paradigms, held at the Congress of the International Association for the Scientific Study of Mental Deficiency in Australia in August 1992. The book presents 13 chapters, all written within a critical paradigm for disability research which critiques the reification of…

Problems with a Play Paradigm: A Reply to Dansky.

ERIC Educational Resources Information Center

Simon, Tony; Smith, Peter K.

1986-01-01

In answer to points raised by Dansky (1985) about specific inferences from Simon and Smith's study (1985) and broader issues about a single-session paradigm used in play and problem solving studies, Simon and Smith argue that their study adequately demonstrated how methodological factors in paradigm can swamp the effects of any treatment…

Understanding and Implementing the CLT (Communicative Language Teaching) Paradigm

ERIC Educational Resources Information Center

Jacobs, George M.; Farell, Thomas S. C.

2003-01-01

The call to change seems to be a constant in education. In second language education, a constellation of changes have been proposed and, to some extent, implemented. This constellation of interconnected changes can perhaps best be termed a paradigm shift, with this paradigm fitting under the general umbrella of Communicative Language Teaching…

Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Pair Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Mizuno, Y.

2005-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created by relativistic pair jets are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet propagating through an ambient plasma with and without initial magnetic fields. The growth rates of the Weibel instability depends on the distribution of pair jets. Simulations show that the Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Pair Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K. I.; Hardee, P.; Hededal, C. B.; Richardson, G.; Sol, H.; Preece, R.; Fishman, G. J.

2004-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., Buneman, Weibel and other two-stream instabilities) created in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating into an ambient plasma. We find that the growth times depend on the Lorenz factors of jets. The jets with larger Lorenz factors grow slower. Simulations show that the Weibel instability created in the collisionless shock front accelerates jet and ambient particles both perpendicular and parallel to the jet propagation direction. The small scale magnetic field structure generated by the Weibel instability is appropriate to the generation of "jitter" radiation from deflected electrons (positrons) as opposed to synchrotron radiation. The jitter radiation resulting from small scale magnetic field structures may be important for understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources containing relativistic jets and relativistic collisionless shocks.

Paradigms in epidemiology textbooks: in the footsteps of Thomas Kuhn.

PubMed Central

Bhopal, R

1999-01-01

This article attempts to contribute to the debate on the future of epidemiology by combining Thomas Kuhn's ideas on scientific paradigms with the author's observations on some epidemiology textbooks. The author's interpretations were based on his readings of Kuhn's The Structure of Scientific Revolutions, epidemiology textbooks, and papers on the future of epidemiology. Thomas Kuhn's view is that sciences mostly work with a single paradigm driven by exemplars of successful work, and that proposals for paradigm change are resisted. Sciences that are maturing or changing do not have a dominant paradigm. Epidemiology textbooks showed diversity in their concepts, content, and approach. Most exemplars related to etiologic research rather than public health practice. One key focus of the recent controversy regarding the role of epidemiology has been the increasing inability of epidemiology to solve socially based public health problems. Kuhn's views help explain the polarization of views expressed. Kuhn's philosophy of science offers insights into controversies such as whether a paradigm shift is needed or imminent and the gap between epidemiology and public health practice. Interaction between science philosophers, epidemiologists, and public health practitioners may be valuable. PMID:10432899

Paradigms in epidemiology textbooks: in the footsteps of Thomas Kuhn.

PubMed

Bhopal, R

1999-08-01

This article attempts to contribute to the debate on the future of epidemiology by combining Thomas Kuhn's ideas on scientific paradigms with the author's observations on some epidemiology textbooks. The author's interpretations were based on his readings of Kuhn's The Structure of Scientific Revolutions, epidemiology textbooks, and papers on the future of epidemiology. Thomas Kuhn's view is that sciences mostly work with a single paradigm driven by exemplars of successful work, and that proposals for paradigm change are resisted. Sciences that are maturing or changing do not have a dominant paradigm. Epidemiology textbooks showed diversity in their concepts, content, and approach. Most exemplars related to etiologic research rather than public health practice. One key focus of the recent controversy regarding the role of epidemiology has been the increasing inability of epidemiology to solve socially based public health problems. Kuhn's views help explain the polarization of views expressed. Kuhn's philosophy of science offers insights into controversies such as whether a paradigm shift is needed or imminent and the gap between epidemiology and public health practice. Interaction between science philosophers, epidemiologists, and public health practitioners may be valuable.

The "extended mind" approach for a new paradigm of psychology.

PubMed

Kono, Tetsuya

2010-12-01

In this paper, I would like to propose the idea of "extended mind" for a new paradigm of psychology. Kohler (Integrative Psychology & Behavioral Science 44:39-57, 2010) correctly pointed out the serious problems of the machine paradigm, and proposed the "organic" view as a new paradigm. But the term "organic" signifying the processes inside the body, is inadequate to express the characteristic of human mind. The recent philosophy of mind suggests that the mind is realized neither only in the brain nor only in the body, but in the whole system of brain-body-environment, namely, in the "extended mind". The characteristic of human mind resides in the interaction with the mediating tools, artifacts, and the humanized environment. We should propose an "extended mind approach" or an "ecological approach to humanized environment" as a new paradigm for a psychology.

The Challenge of Infectious Diseases to the Biomedical Paradigm

ERIC Educational Resources Information Center

Foladori, Guillermo

2005-01-01

The resurgence of infectious diseases and the emergence of infectious diseases raise questions on how to cope with the situation. The germ or clinical approach is the hegemonic biomedical paradigm. In this article, the author argues that the spread of infectious diseases has posted a challenge to the biomedical paradigm and shows how lock-in…

Researching Style: Epistemology, Paradigm Shifts and Research Interest Groups

ERIC Educational Resources Information Center

Rayner, Stephen

2011-01-01

This paper identifies the need for a deliberate approach to theory building in the context of researching cognitive and learning style differences in human performance. A case for paradigm shift and a focus upon research epistemology is presented, building upon a recent critique of style research. A proposal for creating paradigm shift is made,…

Automation of learning-set testing - The video-task paradigm

NASA Technical Reports Server (NTRS)

Washburn, David A.; Hopkins, William D.; Rumbaugh, Duane M.

1989-01-01

Researchers interested in studying discrimination learning in primates have typically utilized variations in the Wisconsin General Test Apparatus (WGTA). In the present experiment, a new testing apparatus for the study of primate learning is proposed. In the video-task paradigm, rhesus monkeys (Macaca mulatta) respond to computer-generated stimuli by manipulating a joystick. Using this apparatus, discrimination learning-set data for 2 monkeys were obtained. Performance on Trial 2 exceeded 80 percent within 200 discrimination learning problems. These data illustrate the utility of the video-task paradigm in comparative research. Additionally, the efficient learning and rich data that were characteristic of this study suggest several advantages of the present testing paradigm over traditional WGTA testing.

A Tutoring and Student Modelling Paradigm for Gaming Environments.

ERIC Educational Resources Information Center

Burton, Richard R.; Brown, John Seely

This paper describes a paradigm for tutorial systems capable of automatically providing feedback and hints in a game environment. The paradigm is illustrated by a tutoring system for the PLATO game "How the West Was Won." The system uses a computer-based "Expert" player to evaluate a student's moves and construct a "differential model" of the…

Strategic Intellectual Capital Development: A Defining Paradigm for HRD?

ERIC Educational Resources Information Center

Holton, Elwood F., III; Yamkovenko, Bogdan

2008-01-01

The performance paradigm of human resource development (HRD) practice has served the field well, particularly in enhancing the relevance and impact of HRD interventions. However, in this article, it is argued that the time has come for a new defining paradigm to advance the field of HRD to a higher level of organizational impact. This article…

Challenging paradigms in estuarine ecology and management

NASA Astrophysics Data System (ADS)

Elliott, M.; Whitfield, A. K.

2011-10-01

For many years, estuarine science has been the 'poor relation' in aquatic research - freshwater scientists ignored estuaries as they tended to get confused by salt and tides, and marine scientists were more preoccupied by large open systems. Estuaries were merely regarded by each group as either river mouths or sea inlets respectively. For the past four decades, however, estuaries (and other transitional waters) have been regarded as being ecosystems in their own right. Although often not termed as such, this has led to paradigms being generated to summarise estuarine structure and functioning and which relate to both the natural science and management of these systems. This paper defines, details and affirms these paradigms that can be grouped into those covering firstly the science (definitions, scales, linkages, productivity, tolerances and variability) and secondly the management (pressures, valuation, health and services) of estuaries. The more 'science' orientated paradigms incorporate the development and types of ecotones, the nature of stressed and variable systems (with specific reference to resilience and redundancy), the relationship between generalists and specialists produced by environmental tolerance, the relevance of scale in relation to functioning and connectivity, the sources of production and degree of productivity, the biodiversity-ecosystem functioning and the stress-subsidy debates. The more 'management' targeted paradigms include the development and effects of exogenic unmanaged pressures and endogenic managed pressures, the perception of health and the ability to manage estuaries (related to internal and external influences), and the influence of all of these on the production of ecosystem services and societal benefits.

Paradigms and progress in vocal fold restoration.

PubMed

Ford, Charles N

2008-09-01

Science advances occur through orderly steps, puzzle-solving leaps, or divergences from the accepted disciplinary matrix that occasionally result in a revolutionary paradigm shift. Key advances must overcome bias, criticism, and rejection. Examples in biological science include use of embryonic stem cells, recognition of Helicobacter pylori in the etiology of ulcer disease, and the evolution of species. Our work in vocal fold restoration reflects these patterns. We progressed through phases of tissue replacement with fillers and biological implants, to current efforts at vocal fold regeneration through tissue engineering, and face challenges of a new "systems biology" paradigm embracing genomics and proteomics.

A Systems Approach to Radiation Carcinogenesis

NASA Astrophysics Data System (ADS)

Hlatky, Lynn

Understanding carcinogenesis risk is complicated by a number of factors, among these the lack of a common platform to integrate and analyze the available data, and the inherently systemsbiologic nature of the problem. We have investigated mechanistic approaches to radiogenic risk estimation that draw on unifying biological principles and incorporate data from multiscale sources. The resultant modeling takes into account that carcinogenesis is a multi-scale phenomenon, critically influenced by determinants not only at the molecular level, but at the cell and tissue-levels as well. To account for cell-level carcinogenesis progression as influenced by inter-tissue signaling, we have developed a dynamic carrying capacity construct that couples the growth of a tumor with the degree of induced vascularization. We have also characterized the molecular responses to radiation incorporating tissue-level angiogenesis implications, and have found striking radiation-quality-dependent responses. The molecular-level events of initiation and promotion are considered in our Two-Stage Logistic model, while incorporating in a rudimentary way the larger-scale growth-limiting role of cell-cell interactions. These and other recent studies undertaken to elaborate radiation-induced carcinogenesis are discussed, in pursuit of a more complete paradigm for understanding radiation induction of cancer and the consequent risk.

The virtual enhancements - solar proton event radiation (VESPER) model

NASA Astrophysics Data System (ADS)

Aminalragia-Giamini, Sigiava; Sandberg, Ingmar; Papadimitriou, Constantinos; Daglis, Ioannis A.; Jiggens, Piers

2018-02-01

A new probabilistic model introducing a novel paradigm for the modelling of the solar proton environment at 1 AU is presented. The virtual enhancements - solar proton event radiation model (VESPER) uses the European space agency's solar energetic particle environment modelling (SEPEM) Reference Dataset and produces virtual time-series of proton differential fluxes. In this regard it fundamentally diverges from the approach of existing SPE models that are based on probabilistic descriptions of SPE macroscopic characteristics such as peak flux and cumulative fluence. It is shown that VESPER reproduces well the dataset characteristics it uses, and further comparisons with existing models are made with respect to their results. The production of time-series as the main output of the model opens a straightforward way for the calculation of solar proton radiation effects in terms of time-series and the pairing with effects caused by trapped radiation and galactic cosmic rays.

Radiation and the regulatory landscape of neo2-Darwinism.

PubMed

Rollo, C David

2006-05-11

Several recently revealed features of eukaryotic genomes were not predicted by earlier evolutionary paradigms, including the relatively small number of genes, the very large amounts of non-functional code and its quarantine in heterochromatin, the remarkable conservation of many functionally important genes across relatively enormous phylogenetic distances, and the prevalence of extra-genomic information associated with chromatin structure and histone proteins. All of these emphasize a paramount role for regulatory evolution, which is further reinforced by recent perspectives highlighting even higher-order regulation governing epigenetics and development (EVO-DEVO). Modern neo2-Darwinism, with its emphasis on regulatory mechanisms and regulatory evolution provides new vision for understanding radiation biology, particularly because free radicals and redox states are central to many regulatory mechanisms and free radicals generated by radiation mimic and amplify endogenous signalling. This paper explores some of these aspects and their implications for low-dose radiation biology.

Implications of an Alternative Social Reform Paradigm for Educational Evaluation.

ERIC Educational Resources Information Center

DiCostanzo, James L.

A recent review of international literature revealed two basic social-change paradigms, equilibrium and conflict. These define ideological predispositions that influence the manner in which evaluations are conducted. Most current evaluations of educational reform can be classified under the equilibrium paradigm; the federally sponsored…

20th Space Simulation Conference: The Changing Testing Paradigm

NASA Technical Reports Server (NTRS)

Stecher, Joseph L., III (Compiler)

1998-01-01

The Institute of Environmental Sciences' Twentieth Space Simulation Conference, "The Changing Testing Paradigm" provided participants with a forum to acquire and exchange information on the state-of-the-art in space simulation, test technology, atomic oxygen, program/system testing, dynamics testing, contamination, and materials. The papers presented at this conference and the resulting discussions carried out the conference theme "The Changing Testing Paradigm."

Geographic Object-Based Image Analysis – Towards a new paradigm

PubMed Central

Blaschke, Thomas; Hay, Geoffrey J.; Kelly, Maggi; Lang, Stefan; Hofmann, Peter; Addink, Elisabeth; Queiroz Feitosa, Raul; van der Meer, Freek; van der Werff, Harald; van Coillie, Frieke; Tiede, Dirk

2014-01-01

The amount of scientific literature on (Geographic) Object-based Image Analysis – GEOBIA has been and still is sharply increasing. These approaches to analysing imagery have antecedents in earlier research on image segmentation and use GIS-like spatial analysis within classification and feature extraction approaches. This article investigates these development and its implications and asks whether or not this is a new paradigm in remote sensing and Geographic Information Science (GIScience). We first discuss several limitations of prevailing per-pixel methods when applied to high resolution images. Then we explore the paradigm concept developed by Kuhn (1962) and discuss whether GEOBIA can be regarded as a paradigm according to this definition. We crystallize core concepts of GEOBIA, including the role of objects, of ontologies and the multiplicity of scales and we discuss how these conceptual developments support important methods in remote sensing such as change detection and accuracy assessment. The ramifications of the different theoretical foundations between the ‘per-pixel paradigm’ and GEOBIA are analysed, as are some of the challenges along this path from pixels, to objects, to geo-intelligence. Based on several paradigm indications as defined by Kuhn and based on an analysis of peer-reviewed scientific literature we conclude that GEOBIA is a new and evolving paradigm. PMID:24623958

Conjugal conflict and violence: a review and theoretical paradigm.

PubMed

Smilkstein, G; Aspy, C B; Quiggins, P A

1994-02-01

Conjugal violence has been described as having multiple etiologies. The variables are so numerous that intervention and research protocols are difficult to effect. This paper proposes a paradigm that establishes conjugal conflict and violence as separate entities. According to the paradigm, conjugal conflict is viewed as "an inevitable part of human association," whereas conjugal violence is determined to be a learned behavioral tactic that is employed as a coping strategy when an individual's conflict threshold potential is exceeded. Evidence will be offered that violence is learned from family of origin and from observing what is common or accepted practice in the community. Use of this paradigm would give primacy to community education programs that advance the concept of conflict resolution through rational discourse.

Perceptual crossing: the simplest online paradigm

PubMed Central

Auvray, Malika; Rohde, Marieke

2012-01-01

Researchers in social cognition increasingly realize that many phenomena cannot be understood by investigating offline situations only, focusing on individual mechanisms and an observer perspective. There are processes of dynamic emergence specific to online situations, when two or more persons are engaged in a real-time interaction that are more than just the sum of the individual capacities or behaviors, and these require the study of online social interaction. Auvray et al.'s (2009) perceptual crossing paradigm offers possibly the simplest paradigm for studying such online interactions: two persons, a one-dimensional space, one bit of information, and a yes/no answer. This study has provoked a lot of resonance in different areas of research, including experimental psychology, computer/robot modeling, philosophy, psychopathology, and even in the field of design. In this article, we review and critically assess this body of literature. We give an overview of both behavioral experimental research and simulated agent modeling done using the perceptual crossing paradigm. We discuss different contexts in which work on perceptual crossing has been cited. This includes the controversy about the possible constitutive role of perceptual crossing for social cognition. We conclude with an outlook on future research possibilities, in particular those that could elucidate the link between online interaction dynamics and individual social cognition. PMID:22723776

Paradigm Shift: Understanding and Implementing Change in Second Language Education.

ERIC Educational Resources Information Center

Jacobs, George M.; Farrell, Thomas

2001-01-01

Describes eight changes that fit the paradigm shift in second language education toward what is often called communicative language teaching: learner autonomy, cooperative learning, curricular integration, focus on meaning, diversity, thinking skills, alternative assessment, and teachers as co-learners. The paradigm shift is examined as an element…

[New Paradigms? Current Trends within National and International Psychotherapy Research].

PubMed

Strauß, Bernhard

2015-09-01

This article is devoted to the question which paradigms currently determine psychotherapy and psychotherapy research, and if there are indicators of paradigm changes in this field. The question of the efficacy and effectiveness (including the effectiveness of a transfer of psychotherapeutic knowledge to service) is specifically focussed as well as the question of the central therapeutic factors and the significance of the person of the therapist. It is argued that there are really some signals of a paradigm switch, with a turn away from controlled outcome research, representing only a minor part of patients in need of psychotherapy, towards a more specific process oriented research, also considering differential effects of the therapist. The most prominent indicator of a paradigm change is reflected by an increasing influence of patient oriented psychotherapy research which - consequently - should also be supported by the insurances as well as the funding organisations. © Georg Thieme Verlag KG Stuttgart · New York.

Is the Linear No-Threshold Dose-Response Paradigm Still Necessary for the Assessment of Health Effects of Low Dose Radiation?

PubMed Central

2016-01-01

Inevitable human exposure to ionizing radiation from man-made sources has been increased with the proceeding of human civilization and consequently public concerns focus on the possible risk to human health. Moreover, Fukushima nuclear power plant accidents after the 2011 East-Japan earthquake and tsunami has brought the great fear and anxiety for the exposure of radiation at low levels, even much lower levels similar to natural background. Health effects of low dose radiation less than 100 mSv have been debated whether they are beneficial or detrimental because sample sizes were not large enough to allow epidemiological detection of excess effects and there was lack of consistency among the available experimental data. We have reviewed an extensive literature on the low dose radiation effects in both radiation biology and epidemiology, and highlighted some of the controversies therein. This article could provide a reasonable view of utilizing radiation for human life and responding to the public questions about radiation risk. In addition, it suggests the necessity of integrated studies of radiobiology and epidemiology at the national level in order to collect more systematic and profound information about health effects of low dose radiation. PMID:26908982

Quantum ergonomics: shifting the paradigm of the systems agenda.

PubMed

Walker, Guy H; Salmon, Paul M; Bedinger, Melissa; Stanton, Neville A

2017-02-01

A paradigm is an accepted world view. If we do not continually question our paradigm then wider trends and movements will overtake the discipline leaving it ill adapted to future challenges. This Special Issue is an opportunity to keep systems thinking at the forefront of ergonomics theory and practice. Systems thinking prompts us to ask whether ergonomics, as a discipline, has been too timid? Too preoccupied with the resolution of immediate problems with industrial-age methods when, approaching fast, are developments which could render these operating assumptions an irrelevance. Practical case studies are presented to show how abstract systems problems can be tackled head-on to deliver highly innovative and cost-effective insights. The strategic direction of the discipline foregrounds high-quality systems problems. These are something the discipline is well able to respond to provided that the appropriate operating paradigms are selected. Practitioner Summary: High-quality systems problems are the future of the discipline. How do we convert obtuse sounding systems concepts into practical interventions? In this paper, the essence of systems thinking is distilled and practical case studies used to demonstrate the benefits of this new paradigm.

Toward a patient-based paradigm for blood transfusion.

PubMed

Farrugia, Albert; Vamvakas, Eleftherios

2014-01-01

The current "manufacturing paradigm" of transfusion practice has detached transfusion from the clinical environment. As an example, fresh whole blood in large-volume hemorrhage may be superior to whole blood reconstituted from multiple components. Multicomponent apheresis can overcome logistical difficulties in matching patient needs with fresh component availability and can deliver the benefits of fresh whole blood. Because of the different transfusion needs of patients in emerging economies and the vulnerability of these blood systems to emerging infections, fresh whole blood and multicomponent apheresis can better meet patient needs when compared with transplants of the "manufacturing paradigm". We propose that patient blood management, along with panels of repeat, paid, accredited apheresis and fresh whole-blood donors can be used in emerging economies to support decentralized blood services. This alternative transfusion-medicine paradigm could eventually also be adopted by established economies to focus transfusion medicine on local patient needs and to alleviate the problem of the aging volunteer donor base.

Information processing psychology: A promising paradigm for research in science teaching

NASA Astrophysics Data System (ADS)

Stewart, James H.; Atkin, Julia A.

Three research paradigms, those of Ausubel, Gagné and Piaget, have received a great deal of attention in the literature of science education. In this article a fourth paradigm is presented - an information processing psychology paradigm. The article is composed of two sections. The first section describes a model of memory developed by information processing psychologists. The second section describes how such a model could be used to guide science education research on learning and problem solving.Received: 19 October 1981

A physiome standards-based model publication paradigm.

PubMed

Nickerson, David P; Buist, Martin L

2009-05-28

In this era of widespread broadband Internet penetration and powerful Web browsers on most desktops, a shift in the publication paradigm for physiome-style models is envisaged. No longer will model authors simply submit an essentially textural description of the development and behaviour of their model. Rather, they will submit a complete working implementation of the model encoded and annotated according to the various standards adopted by the physiome project, accompanied by a traditional human-readable summary of the key scientific goals and outcomes of the work. While the final published, peer-reviewed article will look little different to the reader, in this new paradigm, both reviewers and readers will be able to interact with, use and extend the models in ways that are not currently possible. Here, we review recent developments that are laying the foundations for this new model publication paradigm. Initial developments have focused on the publication of mathematical models of cellular electrophysiology, using technology based on a CellML- or Systems Biology Markup Language (SBML)-encoded implementation of the mathematical models. Here, we review the current state of the art and what needs to be done before such a model publication becomes commonplace.

Multiparametric Determination of Radiation Risk

NASA Technical Reports Server (NTRS)

Richmond, Robert C.

2003-01-01

Predicting risk of human cancer following exposure to ionizing space radiation is challenging in part because of uncertainties of low-dose distribution amongst cells, of unknown potentially synergistic effects of microgravity upon cellular protein-expression, and of processing dose-related damage within cells to produce rare and late-appearing malignant transformation, degrade the confidence of cancer risk-estimates. The NASA- specific responsibility to estimate the risks of radiogenic cancer in a limited number of astronauts is not amenable to epidemiologic study, thereby increasing this challenge. Developing adequately sensitive cellular biodosimeters that simultaneously report 1) the quantity of absorbed close after exposure to ionizing radiation, 2) the quality of radiation delivering that dose, and 3) the risk of developing malignant transformation by the cells absorbing that dose could be useful for resolving these challenges. Use of a multiparametric cellular biodosimeter is suggested using analyses of gene-expression and protein-expression whereby large datasets of cellular response to radiation-induced damage are obtained and analyzed for expression-profiles correlated with established end points and molecular markers predictive for cancer-risk. Analytical techniques of genomics and proteomics may be used to establish dose-dependency of multiple gene- and protein- expressions resulting from radiation-induced cellular damage. Furthermore, gene- and protein-expression from cells in microgravity are known to be altered relative to cells grown on the ground at 1g. Therefore, hypotheses are proposed that 1) macromolecular expression caused by radiation-induced damage in cells in microgravity may be different than on the ground, and 2) different patterns of macromolecular expression in microgravity may alter human radiogenic cancer risk relative to radiation exposure on Earth. A new paradigm is accordingly suggested as a national database wherein genomic and

20th Space Simulation Conference: The Changing Testing Paradigm

NASA Technical Reports Server (NTRS)

Stecher, Joseph L., III (Compiler)

1999-01-01

The Institute of Environmental Sciences and Technology's Twentieth Space Simulation Conference, "The Changing Testing Paradigm" provided participants with a forum to acquire and exchange information on the state-of-the-art in space simulation, test technology, atomic oxygen, program/system testing, dynamics testing, contamination, and materials. The papers presented at this conference and the resulting discussions carried out the conference theme "The Changing Testing Paradigm."

Horizon Mission Methodology - A tool for the study of technology innovation and new paradigms

NASA Technical Reports Server (NTRS)

Anderson, John L.

1993-01-01

The Horizon Mission (HM) methodology was developed to provide a means of identifying and evaluating highly innovative, breakthrough technology concepts (BTCs) and for assessing their potential impact on advanced space missions. The methodology is based on identifying new capabilities needed by hypothetical 'horizon' space missions having performance requirements that cannot be met even by extrapolating known space technologies. Normal human evaluation of new ideas such as BTCs appears to be governed (and limited) by 'inner models of reality' defined as paradigms. Thus, new ideas are evaluated by old models. This paper describes the use of the HM Methodology to define possible future paradigms that would provide alternatives to evaluation by current paradigms. The approach is to represent a future paradigm by a set of new BTC-based capabilities - called a paradigm abstract. The paper describes methods of constructing and using the abstracts for evaluating BTCs for space applications and for exploring the concept of paradigms and paradigm shifts as a representation of technology innovation.

Response to Elvira Panaiotidi, "The Nature of Paradigms and Paradigm Shifts in Music Education"

ERIC Educational Resources Information Center

Rodriguez, Carlos Xavier

2005-01-01

Elvira Panaiotidi has delivered a very useful and appealing paper on the topic of how the music education community decides it is time to change the way it thinks and acts. Her primary focus is whether the concept of "paradigms" proposed by Thomas Kuhn in The Structure of Scientific Revolutions reasonably explains how change occurs in…

Convergent paradigms for visual neuroscience and dissociative identity disorder.

PubMed

Manning, Mark L; Manning, Rana L

2009-01-01

Although dissociative identity disorder, a condition in which multiple individuals appear to inhabit a single body, is a recognized psychiatric disorder, patients may yet encounter health professionals who declare that they simply "do not believe in multiple personalities." This article explores the proposal that resistance to the disorder represents a failure to apply an appropriate paradigm from which the disorder should be interpreted. Trauma and sociocognitive explanations of dissociative identity disorder are contrasted. The trauma hypothesis is further differentiated into paradigms in which trauma affects a defense mechanism, and one in which trauma serves to inhibit the normal integration sequence of parallel processes of the self in childhood. This latter paradigm is shown to be broadly consistent with current models of cortical processing in another system, the cortical visual system.

Prediction of User Preference over Shared Control Paradigms for a Robotic Wheelchair

DTIC Science & Technology

2017-07-20

the experimentally -observed changes between subject groups and sessions, while providing unique insight into the relative contribution of task metrics...WHEELCHAIR, including the four tested shared- control paradigms. The correlation model and experimental results are provided in Sections IV and V. Section VI...paradigm-specific models. Moreover, we also observe differences between sub- ject groups —meaning that subjects’ evaluations of a control paradigm are

Sexual Violence through a Social Justice Paradigm: Framing and Applications

ERIC Educational Resources Information Center

Hong, Luoluo; Marine, Susan B.

2018-01-01

In this chapter, we explore the factors that support the occurrence of sexual violence, including the role of interlocking systems of oppression. Traditional conceptions of "prevention" are deconstructed, a social justice paradigm for addressing sexual violence is advanced, and examples of how the paradigm can be applied to practice are…

The Question of Work: Adolescent Literature and the Eriksonian Paradigm.

ERIC Educational Resources Information Center

Burgan, Mary

1988-01-01

Suggests that focusing on paradigms of work--the way it is described, together with the thematic implications it embodies--can be useful in teaching literature to young adults. Examines how examples from literature illustrate Erik H. Erikson's paradigm of the psychosocial stages of development in late childhood and adolescence. (MM)

Stroke mimics under the drip-and-ship paradigm.

PubMed

Mehta, Sonal; Vora, Nirav; Edgell, Randall C; Allam, Hesham; Alawi, Aws; Koehne, Jennifer; Kumar, Abhay; Feen, Eliahu; Cruz-Flores, Salvador; Alshekhlee, Amer

2014-01-01

Recent reports suggested better outcomes associated with the drip-and-ship paradigm for acute ischemic stroke (AIS) treated with thrombolysis. We hypothesized that a higher rate of stroke mimics (SM) among AIS treated in nonspecialized stroke centers that are transferred to comprehensive centers is responsible for such outcomes. Consecutive patients treated with thrombolysis according to the admission criteria were reviewed in a single comprehensive stroke center over 1 academic year (July 1, 2011 to June 30, 2012). Information on the basic demographic, hospital complications, psychiatric diagnoses, and discharge disposition was collected. We identified those patients who were treated at a facility and then transferred to the tertiary center (ie, drip-and-ship paradigm). In addition to comparative and adjusted analysis to identify predictors for SM, a stratified analysis by the drip-and-ship status was performed. One hundred twenty patients were treated with thrombolysis for AIS included in this analysis; 20 (16.7%) were discharged with the final diagnosis of SM; 14 of those had conversion syndrome and 6 patients had other syndromes (seizures, migraine, and hypoglycemia). Patients with SM were younger (55.6 ± 15.0 versus 69.4 ± 14.9, P = .0003) and more likely to harbor psychiatric diagnoses (45% versus 9%; P ≤ .0001). Eighteen of 20 SM patients (90%) had the drip-and-ship treatment paradigm compared with 65% of those with AIS (P = .02). None of the SM had hemorrhagic complications, and all were discharged to home. Predictors of SM on adjusted analysis included the drip-and-ship paradigm (odds ratio [OR] 12.8, 95% confidence interval [CI] 1.78, 92.1) and history of any psychiatric illness (OR 12.08; 95% CI 3.14, 46.4). Eighteen of 83 drip-and-ship patients (21.7%) were diagnosed with SM compared with 2 of 37 patients (5.4%) presented directly to the hub hospital (P = .02). The drip-and-ship paradigm and any psychiatric history predict the diagnosis of

Illustrating a Model-Game-Model Paradigm for Using Human Wargames in Analysis

DTIC Science & Technology

2017-02-01

Working Paper Illustrating a Model- Game -Model Paradigm for Using Human Wargames in Analysis Paul K. Davis RAND National Security Research...paper proposes and illustrates an analysis-centric paradigm (model- game -model or what might be better called model-exercise-model in some cases) for...to involve stakehold- ers in model development from the outset. The model- game -model paradigm was illustrated in an application to crisis planning

SAID-SAPS Paradigm: Beliefs and Reality

NASA Astrophysics Data System (ADS)

Mishin, E. V.

2016-12-01

Enhanced westward flows are the dominant feature of the plasma convection in the perturbed subauroral geospace. These include latitudinally-narrow "polarization jets" (PJ) or "subauroral ion drifts" (SAID) observed mainly in the premidnight MLT sector and broad flow channels on the duskside. The generic term "sub-auroral polarization streams" (SAPS) was introduced to unite both (narrow and broad) flows, taking for granted that their underlying mechanisms are quite similar, if not the same. The concept of voltage and current generators is believed to explain the SAPS major features. The generator paradigm treats hot, ≥1 keV, plasma sheet (PS) particles as single (test) particles driven by the dawn-to-dusk and co-rotation electric fields and gradient-curvature drift disregarding charge neutrality and concomitant polarization fields, inherent in slow plasma processes. In this approach, the inner boundary of the hot ion trajectories on the duskside extends earthward of that of the PS electrons by some distance increasing toward dusk. However, magnetically conjugate observations in the evening sector reveal that the generator paradigm fails to explain the substorm SAID features and that they are rather explained in terms of a short-circuiting of substorm-injected hot plasma jets over the plasmapause. This report presents multispacecraft magnetically conjugate observations of substorm-enhanced flows on the duskside showing that their features are hardly compatible with the (test particle) generator paradigm. It is suggested that they are causally related to the two-loop system of the westward traveling surge.

Of Metaphors and Paradigms: Rejecting the "Commonsense" View of Reading.

ERIC Educational Resources Information Center

Weaver, Constance

For many years, methods of teaching reading have been based upon a mechanistic paradigm that something can be understood by reducing it to its most basic parts. This scientific paradigm has led to several misconceptions about reading: (1) that comprehension can be reduced to separately identifiable parts, (2) that meaning is contained within the…

Paradigm Shift: Understanding and Implementing Change in Second Language Education

ERIC Educational Resources Information Center

Jacobs, George M.; Farrell, Thomas S. C.

2001-01-01

Change seems to be a constant in education. We can better understand and implement change in second language education if we look for connections between changes. The concept of paradigm shift offers one means of making such connections. This article describes eight changes that fit with the paradigm shift in second language education toward what…

What's Past Is Prologue: The Evolving Paradigms of Student Affairs

ERIC Educational Resources Information Center

Taylor, Simone Himbeault

2008-01-01

The purpose of this article is to frame--and reframe--the work of student affairs. Evolving paradigms have defined and advanced this work, which is dedicated to total student development and the betterment of society. The article promotes integrative learning as a new framework for student affairs. This paradigm, grounded in theory, research, and…

A Paradigm for Learning in a World of Continuous Change

ERIC Educational Resources Information Center

Thompson, Scott

2014-01-01

Through ongoing rapid-fire changes in the nature of communications, the social, professional, and political landscapes of our time are rapidly transforming. But the prevailing paradigm in most schools and school systems is a relic of the industrial revolution. Schools and school systems must adopt a new paradigm for learning if they are to remain…

Think globally, research locally: paradigms and place in agroecological research.

PubMed

Reynolds, Heather L; Smith, Alex A; Farmer, James R

2014-10-01

Conducting science for practical ends implicates scientists, whether they wish it or not, as agents in social-ecological systems, raising ethical, economic, environmental, and political issues. Considering these issues helps scientists to increase the relevance and sustainability of research outcomes. As we rise to the worthy call to connect basic research with food production, scientists have the opportunity to evaluate alternative food production paradigms and consider how our research funds and efforts are best employed. In this contribution, we review some of the problems produced by science conducted in service of industrial agriculture and its associated economic growth paradigm. We discuss whether the new concept of "ecological intensification" can rescue the industrial agriculture/growth paradigm and present an emerging alternative paradigm of decentralized, localized, biodiversity-promoting agriculture for a steady-state economy. This "custom fit" agriculture engages constructively with complex and highly localized ecosystems, and we draw from examples of published work to demonstrate how ecologists can contribute by using approaches that acknowledge local agricultural practices and draw on community participation. © 2014 Botanical Society of America, Inc.

Staff Development: A Gestalt Paradigm.

ERIC Educational Resources Information Center

Parsons, Michael H.

Hagerstown Junior College, Maryland, has had a staff development program for the past five years. The major components have been evaluated, revised, and integrated into a gestalt paradigm--a total institutional thrust designed to insure that the goals of the college meet the challenges presented by the service area. Each component exists to foster…

MICROHABITAT REVIEWED: ANALYSIS OF A PARADIGM

EPA Science Inventory

Small mammal microhabitat partitioning research has greatly influenced vertebrate community ecologists. It is not a stretch to assert that there exists a 'microhabitat paradigm' among small mammal specialists; sympatry among small mammal species is enabled by differential use of...

3-D RPIC simulations of relativistic jets: Particle acceleration, magnetic field generation, and emission

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.

2006-01-01

Nonthermal radiation observed from astrophysical systems containing (relativistic) jets and shocks, e.g., supernova remnants, active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the .shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations which show particle acceleration in jets.

[Steroid hormones and pancreas: a new paradigm].

PubMed

Morales-Miranda, Angélica; Robles-Díaz, Guillermo; Díaz-Sánchez, Vicente

2007-01-01

The relation between steroid hormones and pancreatic function has been poorly discussed and not very well understood. In general, there is a lack of recognition among the scientific community about the importance of steroids in pancreatic function (current paradigm). In the present article we present basic, as well as clinic and epidemiologic data that demonstrate steroid synthesis and steroid biotransformation by pancreatic tissue, how exocrine and endocrine functions are modulated by steroids, the gender specific frequency and behavior of some tumors and the use of synthetic steroids and steroid action antagonists as therapeutic agents. With the available information it is possible to establish that: 1. Pancreatic tissue synthesize and transform steroid hormones. 2. Pancreatic tissue respond to steroid hormones and express steroid specific receptor molecules. 3. Some endocrine functions such as insulin synthesis and release are modulated by steroids. 4. Tumor growth is modulated by steroids and anti-steroid drugs. This set of data creates a new paradigm for the holistic study of pancreas and opens new research fields. The application of this new paradigm might result in an increase in the knowledge of pancreatic physiology, in the design of new and better diagnostic methods and eventually in the design of more effective medical treatments for the pancreatic cancers.

Uniting paradigms of connectivity in marine ecology.

PubMed

Brown, Christopher J; Harborne, Alastair R; Paris, Claire B; Mumby, Peter J

2016-09-01

The connectivity of marine organisms among habitat patches has been dominated by two independent paradigms with distinct conservation strategies. One paradigm is the dispersal of larvae on ocean currents, which suggests networks of marine reserves. The other is the demersal migration of animals from nursery to adult habitats, requiring the conservation of connected ecosystem corridors. Here, we suggest that a common driver, wave exposure, links larval and demersal connectivity across the seascape. To study the effect of linked connectivities on fish abundance at reefs, we parameterize a demographic model for The Bahamas seascape using maps of habitats, empirically forced models of wave exposure and spatially realistic three-dimensional hydrological models of larval dispersal. The integrated empirical-modeling approach enabled us to study linked connectivity on a scale not currently possible by purely empirical studies. We find sheltered environments not only provide greater nursery habitat for juvenile fish but larvae spawned on adjacent reefs have higher retention, thereby creating a synergistic increase in fish abundance. Uniting connectivity paradigms to consider all life stages simultaneously can help explain the evolution of nursery habitat use and simplifies conservation advice: Reserves in sheltered environments have desirable characteristics for biodiversity conservation and can support local fisheries through adult spillover. © 2016 by the Ecological Society of America.

Kappa and Rater Accuracy: Paradigms and Parameters.

PubMed

Conger, Anthony J

2017-12-01

Drawing parallels to classical test theory, this article clarifies the difference between rater accuracy and reliability and demonstrates how category marginal frequencies affect rater agreement and Cohen's kappa (κ). Category assignment paradigms are developed: comparing raters to a standard (index) versus comparing two raters to one another (concordance), using both nonstochastic and stochastic category membership. Using a probability model to express category assignments in terms of rater accuracy and random error, it is shown that observed agreement (Po) depends only on rater accuracy and number of categories; however, expected agreement (Pe) and κ depend additionally on category frequencies. Moreover, category frequencies affect Pe and κ solely through the variance of the category proportions, regardless of the specific frequencies underlying the variance. Paradoxically, some judgment paradigms involving stochastic categories are shown to yield higher κ values than their nonstochastic counterparts. Using the stated probability model, assignments to categories were generated for 552 combinations of paradigms, rater and category parameters, category frequencies, and number of stimuli. Observed means and standard errors for Po, Pe, and κ were fully consistent with theory expectations. Guidelines for interpretation of rater accuracy and reliability are offered, along with a discussion of alternatives to the basic model.

Levelling in the German Verb Paradigm

ERIC Educational Resources Information Center

Newman, John

1974-01-01

Levelling processes in the history of the German verb paradigm from Old High German to the present are discussed. It is asserted that the theory of transformational generative grammar provides a proper framework for the study of linguistic change. (RM)

Transforming Psychological Practice and Society: Policies that Reflect the New Paradigm.

ERIC Educational Resources Information Center

Gill, Carol J.; Kewman, Donald G.; Brannon, Ruth W.

2003-01-01

Understanding disability through a social paradigm offers opportunities to reframe the way psychologists define problems related to disability, develop more collaborative relationships between psychologists and people with disabilities, and adopt new professional responsibilities. Addresses the impact of the social paradigm on policies within…

Theory, Scientific Evidence, and the Communibiological Paradigm: Reflections on Misguided Criticism.

ERIC Educational Resources Information Center

Beatty, Michael J.; McCroskey, James C.

2000-01-01

Replies to C. M. Condit's responses to the authors' articles and comments advancing a communibiological paradigm. Argues that a general misidentification of the level of abstraction (paradigm not theory) drives Condit's complaints about communibiology, and outlines several misrepresentations of the authors' position. (SR)

Distance Learning and University Effectiveness: Changing Educational Paradigms for Online Learning

ERIC Educational Resources Information Center

Howard, Caroline; Schenk, Karen; Discenza, Richard

2004-01-01

"Distance Learning and University Effectiveness: Changing Educational Paradigms for Online Learning" addresses the challenges and opportunities associated with information and communication technologies (ICTs) as related to education. From discussing new and innovative educational paradigms and learning models resulting from ICTs to addressing…

The peopleware paradigm.

PubMed

Andrew, C G

1996-08-01

Manufacturing managements and practitioners alike are at long last realizing that the heartbeat of competitive advantage springs from peopleware, not hardware and software. But despite this heightened awareness the problem persists even among manufacturing professionals--they may talk a good game about priortizing people and quality, but all too many have precious little idea of how to go about it with constancy of purpose. This article bridges the gap and addresses the key issues in adopting the powerful new peopleware paradigm that provides the positive motivational climate for the improvement-change journey toward world-class performance through teamwork, innovation, and continuous improvement.

Experimental Psychopathology Paradigms for Alcohol Use Disorders: Applications for Translational Research

PubMed Central

Bujarski, Spencer; Ray, Lara A.

2016-01-01

In spite of high prevalence and disease burden, scientific consensus on the etiology and treatment of Alcohol Use Disorder (AUD) has yet to be reached. The development and utilization of experimental psychopathology paradigms in the human laboratory represents a cornerstone of AUD research. In this review, we describe and critically evaluate the major experimental psychopathology paradigms developed for AUD, with an emphasis on their implications, strengths, weaknesses, and methodological considerations. Specifically we review alcohol administration, self-administration, cue-reactivity, and stress-reactivity paradigms. We also provide an introduction to the application of experimental psychopathology methods to translational research including genetics, neuroimaging, pharmacological and behavioral treatment development, and translational science. Through refining and manipulating key phenotypes of interest, these experimental paradigms have the potential to elucidate AUD etiological factors, improve the efficiency of treatment developments, and refine treatment targets thus advancing precision medicine. PMID:27266992

Experimental psychopathology paradigms for alcohol use disorders: Applications for translational research.

PubMed

Bujarski, Spencer; Ray, Lara A

2016-11-01

In spite of high prevalence and disease burden, scientific consensus on the etiology and treatment of Alcohol Use Disorder (AUD) has yet to be reached. The development and utilization of experimental psychopathology paradigms in the human laboratory represents a cornerstone of AUD research. In this review, we describe and critically evaluate the major experimental psychopathology paradigms developed for AUD, with an emphasis on their implications, strengths, weaknesses, and methodological considerations. Specifically we review alcohol administration, self-administration, cue-reactivity, and stress-reactivity paradigms. We also provide an introduction to the application of experimental psychopathology methods to translational research including genetics, neuroimaging, pharmacological and behavioral treatment development, and translational science. Through refining and manipulating key phenotypes of interest, these experimental paradigms have the potential to elucidate AUD etiological factors, improve the efficiency of treatment developments, and refine treatment targets thus advancing precision medicine. Copyright © 2016 Elsevier Ltd. All rights reserved.

Radiation Detection for Homeland Security Applications

NASA Astrophysics Data System (ADS)

Ely, James

2008-05-01

In the past twenty years or so, there have been significant changes in the strategy and applications for homeland security. Recently there have been significant at deterring and interdicting terrorists and associated organizations. This is a shift in the normal paradigm of deterrence and surveillance of a nation and the `conventional' methods of warfare to the `unconventional' means that terrorist organizations resort to. With that shift comes the responsibility to monitor international borders for weapons of mass destruction, including radiological weapons. As a result, countries around the world are deploying radiation detection instrumentation to interdict the illegal shipment of radioactive material crossing international borders. These efforts include deployments at land, rail, air, and sea ports of entry in the US and in European and Asian countries. Radioactive signatures of concern include radiation dispersal devices (RDD), nuclear warheads, and special nuclear material (SNM). Radiation portal monitors (RPMs) are used as the main screening tool for vehicles and cargo at borders, supplemented by handheld detectors, personal radiation detectors, and x-ray imaging systems. This talk will present an overview of radiation detection equipment with emphasis on radiation portal monitors. In the US, the deployment of radiation detection equipment is being coordinated by the Domestic Nuclear Detection Office within the Department of Homeland Security, and a brief summary of the program will be covered. Challenges with current generation systems will be discussed as well as areas of investigation and opportunities for improvements. The next generation of radiation portal monitors is being produced under the Advanced Spectroscopic Portal program and will be available for deployment in the near future. Additional technologies, from commercially available to experimental, that provide additional information for radiation screening, such as density imaging equipment, will

The Predictive Processing Paradigm Has Roots in Kant.

PubMed

Swanson, Link R

2016-01-01

Predictive processing (PP) is a paradigm in computational and cognitive neuroscience that has recently attracted significant attention across domains, including psychology, robotics, artificial intelligence and philosophy. It is often regarded as a fresh and possibly revolutionary paradigm shift, yet a handful of authors have remarked that aspects of PP seem reminiscent of the work of 18th century philosopher Immanuel Kant. To date there have not been any substantive discussions of how exactly PP links back to Kant. In this article, I argue that several core aspects of PP were anticipated by Kant (1996/1787) in his works on perception and cognition. Themes from Kant active in PP include: (1) the emphasis on "top-down" generation of percepts; (2) the role of "hyperpriors"; (3) the general function of "generative models"; (4) the process of "analysis-by-synthesis"; and (5) the crucial role of imagination in perception. In addition to these, I also point out that PP echoes Kant's general project in that it aims to explain how minds track causal structure in the world using only sensory data, and that it uses a reverse-engineer or "top-down" method of analysis. I then locate a possible source of Kant's influence on PP by tracing the paradigm back to Hermann von Helmholtz, who saw himself as providing a scientific implementation of Kant's conclusions. I conclude by arguing that PP should not be regarded as a new paradigm, but is more appropriately understood as the latest incarnation of an approach to perception and cognition initiated by Kant and refined by Helmholtz.

Reductionism, Paradigm Shifts, and Learning Disabilities.

ERIC Educational Resources Information Center

Forness, Steven R.

1988-01-01

In response to two papers decrying reductionism and advocating holistic constructivism in models of learning disabilities, the article applauds trends toward a shifting paradigm in the field but warns against advocating any single approach as the only valid path to effective learning. (DB)

Animal to human translational paradigms relevant for approach avoidance conflict decision making.

PubMed

Kirlic, Namik; Young, Jared; Aupperle, Robin L

2017-09-01

Avoidance behavior in clinical anxiety disorders is often a decision made in response to approach-avoidance conflict, resulting in a sacrifice of potential rewards to avoid potential negative affective consequences. Animal research has a long history of relying on paradigms related to approach-avoidance conflict to model anxiety-relevant behavior. This approach includes punishment-based conflict, exploratory, and social interaction tasks. There has been a recent surge of interest in the translation of paradigms from animal to human, in efforts to increase generalization of findings and support the development of more effective mental health treatments. This article briefly reviews animal tests related to approach-avoidance conflict and results from lesion and pharmacologic studies utilizing these tests. We then provide a description of translational human paradigms that have been developed to tap into related constructs, summarizing behavioral and neuroimaging findings. Similarities and differences in findings from analogous animal and human paradigms are discussed. Lastly, we highlight opportunities for future research and paradigm development that will support the clinical utility of this translational work. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Lunar Magma Ocean (LMO) Paradigm Versus the Realities of Lunar Anorthosites

NASA Astrophysics Data System (ADS)

Treiman, A. H.; Gross, J.

2018-05-01

The paradigm of the Lunar Magma Ocean (LMO) is inconsistent with much chemical and compositional data on lunar anorthosites. The paradigm of serial anorthosite diapirism is more consistent, though not a panacea.

Population, poverty and social transformation: an alternative paradigm.

PubMed

Pethe, V P

1992-06-01

"In this paper I have proposed a new alternative paradigm on the interrelations between population, poverty and the related concerns [in India]. Its central thesis is that the population problem has also the concomitant social problems [of] unemployment, ill health, [and] crime, [with] (1) poverty as their 'immediate' determinant, (2) such evils as inequality, consumerism, military expenditure, defective planning...as their 'intermediate' determinants, and (3) out-moded non-egalitarian social structures, vicious human psyche and spiritual degradation as their 'ultimate' determinants. This new paradigm has implications for policy and programme logistics that are fundamentally different from official policy." excerpt

Use of a Passive Reaction Wheel Jitter Isolation System to Meet the Advanced X-Ray Astrophysics Facility Imaging Performance Requirements

NASA Technical Reports Server (NTRS)

Pendergast, Karl J.; Schauwecker, Christopher J.

1998-01-01

Third in the series of NASA great observatories, the Advanced X-Ray Astrophysics Facility (AXAF) is scheduled for launch from the Space Shuttle in November of 1998. Following in the path of the Hubble Space Telescope and the Compton Gamma Ray Observatory, this observatory will image light at X-ray wavelengths, facilitating the detailed study of such phenomena as supernovae and quasars. The AXAF project is sponsored by the Marshall Space Flight Center in Huntsville, Alabama. Because of exacting requirements on the performance of the AXAF optical system, it was necessary to reduce the transmission of reaction wheel jitter disturbances to the observatory. This reduction was accomplished via use of a passive mechanical isolation system to interface the reaction wheels with the spacecraft central structure. In addition to presenting a description of the spacecraft, the isolation system, and the key image quality requirement flowdown, this paper details the analyses performed in support of system-level imaging performance requirement verification. These analyses include the identification of system-level requirement suballocations, quantification of imaging and pointing performance, and formulation of unit-level isolation system transmissibility requirements. Given in comparison to the non-isolated system imaging performance, the results of these analyses clearly illustrate the effectiveness of an innovative reaction wheel passive isolation system.

Pins and posters: Paradigms for content publication on situated displays.

PubMed

José, Rui; Pinto, Hélder; Silva, Bruno; Melro, Ana

2013-01-01

Public-display systems are still far from being a medium for meeting people's diverse communication goals. Moving toward open displays will require publication paradigms that can overcome the challenges of meaningful engagement and enable users to fully understand and control the publication process. The metaphors of pins and posters have inspired two complementary paradigms for public displays. Researchers implemented these paradigms in the Instant Places system, which they deployed on 10 displays in diverse urban locations for six months. They collected user and system data regarding the users' practices. The findings improve the understanding of what might drive user-generated content in networks of urban displays. Such knowledge can inform the design of tools and procedures for situated publication in public displays.

Preoperative Single-Fraction Partial Breast Radiation Therapy: A Novel Phase 1, Dose-Escalation Protocol With Radiation Response Biomarkers

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

Horton, Janet K., E-mail: janet.horton@duke.edu; Blitzblau, Rachel C.; Yoo, Sua

should be tested in future clinical trials because it has the potential to challenge the current treatment paradigm and provide a path forward to identify radiation response biomarkers.« less

Active, passive, and motor imagery paradigms: component analysis to assess neurovascular coupling.

PubMed

Salinet, Angela S M; Robinson, Thompson G; Panerai, Ronney B

2013-05-15

The association between neural activity and cerebral blood flow (CBF) has been used to assess neurovascular coupling (NVC) in health and diseases states, but little attention has been given to the contribution of simultaneous changes in peripheral covariates. We used an innovative approach to assess the contributions of arterial blood pressure (BP), PaCO2, and the stimulus itself to changes in CBF velocities (CBFv) during active (MA), passive (MP), and motor imagery (MI) paradigms. Continuous recordings of CBFv, beat-to-beat BP, heart rate, and breath-by-breath end-tidal CO2 (EtCO2) were performed in 17 right-handed subjects before, during, and after motor-cognitive paradigms performed with the right arm. A multivariate autoregressive-moving average model was used to calculate the separate contributions of BP, EtCO2, and the neural activation stimulus (represented by a metronome on-off signal) to the CBFv response during paradigms. Differences were found in the bilateral CBFv responses to MI compared with MA and MP, due to the contributions of stimulation (P < 0.05). BP was the dominant contributor to the initial peaked CBFv response in all paradigms with no significant differences between paradigms, while the contribution of the stimulus explained the plateau phase and extended duration of the CBFv responses. Separating the neural activation contribution from the influences of other covariates, it was possible to detect differences between three paradigms often used to assess disease-related NVC. Apparently similar CBFv responses to different motor-cognitive paradigms can be misleading due to the contributions from peripheral covariates and could lead to inaccurate assessment of NVC, particularly during MI.

Stimulation of the human auditory nerve with optical radiation

NASA Astrophysics Data System (ADS)

Fishman, Andrew; Winkler, Piotr; Mierzwinski, Jozef; Beuth, Wojciech; Izzo Matic, Agnella; Siedlecki, Zygmunt; Teudt, Ingo; Maier, Hannes; Richter, Claus-Peter

2009-02-01

A novel, spatially selective method to stimulate cranial nerves has been proposed: contact free stimulation with optical radiation. The radiation source is an infrared pulsed laser. The Case Report is the first report ever that shows that optical stimulation of the auditory nerve is possible in the human. The ethical approach to conduct any measurements or tests in humans requires efficacy and safety studies in animals, which have been conducted in gerbils. This report represents the first step in a translational research project to initiate a paradigm shift in neural interfaces. A patient was selected who required surgical removal of a large meningioma angiomatum WHO I by a planned transcochlear approach. Prior to cochlear ablation by drilling and subsequent tumor resection, the cochlear nerve was stimulated with a pulsed infrared laser at low radiation energies. Stimulation with optical radiation evoked compound action potentials from the human auditory nerve. Stimulation of the auditory nerve with infrared laser pulses is possible in the human inner ear. The finding is an important step for translating results from animal experiments to human and furthers the development of a novel interface that uses optical radiation to stimulate neurons. Additional measurements are required to optimize the stimulation parameters.

An adaptive semantic matching paradigm for reliable and valid language mapping in individuals with aphasia.

PubMed

Wilson, Stephen M; Yen, Melodie; Eriksson, Dana K

2018-04-17

Research on neuroplasticity in recovery from aphasia depends on the ability to identify language areas of the brain in individuals with aphasia. However, tasks commonly used to engage language processing in people with aphasia, such as narrative comprehension and picture naming, are limited in terms of reliability (test-retest reproducibility) and validity (identification of language regions, and not other regions). On the other hand, paradigms such as semantic decision that are effective in identifying language regions in people without aphasia can be prohibitively challenging for people with aphasia. This paper describes a new semantic matching paradigm that uses an adaptive staircase procedure to present individuals with stimuli that are challenging yet within their competence, so that language processing can be fully engaged in people with and without language impairments. The feasibility, reliability and validity of the adaptive semantic matching paradigm were investigated in sixteen individuals with chronic post-stroke aphasia and fourteen neurologically normal participants, in comparison to narrative comprehension and picture naming paradigms. All participants succeeded in learning and performing the semantic paradigm. Test-retest reproducibility of the semantic paradigm in people with aphasia was good (Dice coefficient = 0.66), and was superior to the other two paradigms. The semantic paradigm revealed known features of typical language organization (lateralization; frontal and temporal regions) more consistently in neurologically normal individuals than the other two paradigms, constituting evidence for validity. In sum, the adaptive semantic matching paradigm is a feasible, reliable and valid method for mapping language regions in people with aphasia. © 2018 Wiley Periodicals, Inc.

ECOSYSTEM MANAGEMENT: DESPERATELY SEEKING A PARADIGM

EPA Science Inventory

Two competing views of ecosystem management have emerged. One is that ecosystem management is another stage in the continual evolution of the basic management paradigm - one that natural resource managers have followed in North America for a century. The other view is that ecosys...

The maturing of the quality improvement paradigm in the SEL

NASA Technical Reports Server (NTRS)

Basili, Victor R.

1993-01-01

The Software Engineering Laboratory uses a paradigm for improving the software process and product, called the quality improvement paradigm. This paradigm has evolved over the past 18 years, along with our software development processes and product. Since 1976, when we first began the SEL, we have learned a great deal about improving the software process and product, making a great many mistakes along the way. Quality improvement paradigm, as it is currently defined, can be broken up into six steps: characterize the current project and its environment with respect to the appropriate models and metrics; set the quantifiable goals for successful project performance and improvement; choose the appropriate process model and supporting methods and tools for this project; execute the processes, construct the products, and collect, validate, and analyze the data to provide real-time feedback for corrective action; analyze the data to evaluate the current practices, determine problems, record findings, and make recommendations for future project improvements; and package the experience gained in the form of updated and refined models and other forms of structured knowledge gained from this and prior projects and save it in an experience base to be reused on future projects.

The effect of changing the secondary task in dual-task paradigms for measuring listening effort.

PubMed

Picou, Erin M; Ricketts, Todd A

2014-01-01

The purpose of this study was to evaluate the effect of changing the secondary task in dual-task paradigms that measure listening effort. Specifically, the effects of increasing the secondary task complexity or the depth of processing on a paradigm's sensitivity to changes in listening effort were quantified in a series of two experiments. Specific factors investigated within each experiment were background noise and visual cues. Participants in Experiment 1 were adults with normal hearing (mean age 23 years) and participants in Experiment 2 were adults with mild sloping to moderately severe sensorineural hearing loss (mean age 60.1 years). In both experiments, participants were tested using three dual-task paradigms. These paradigms had identical primary tasks, which were always monosyllable word recognition. The secondary tasks were all physical reaction time measures. The stimulus for the secondary task varied by paradigm and was a (1) simple visual probe, (2) a complex visual probe, or (3) the category of word presented. In this way, the secondary tasks mainly varied from the simple paradigm by either complexity or depth of speech processing. Using all three paradigms, participants were tested in four conditions, (1) auditory-only stimuli in quiet, (2) auditory-only stimuli in noise, (3) auditory-visual stimuli in quiet, and (4) auditory-visual stimuli in noise. During auditory-visual conditions, the talker's face was visible. Signal-to-noise ratios used during conditions with background noise were set individually so word recognition performance was matched in auditory-only and auditory-visual conditions. In noise, word recognition performance was approximately 80% and 65% for Experiments 1 and 2, respectively. For both experiments, word recognition performance was stable across the three paradigms, confirming that none of the secondary tasks interfered with the primary task. In Experiment 1 (listeners with normal hearing), analysis of median reaction times

NASA Instep/mdmsc Jitter Suppression Experiment (JITTER)

NASA Technical Reports Server (NTRS)

White, Edward V.

1992-01-01

The objectives are the following: (1) to develop and demonstrate in-space performance of both passive and active damping systems for suppression of micro-amplitude vibration on an actual application structure and operate despite uncertain dynamics and uncertain disturbance characteristics; and (2) to correlate ground and in-space performance - the performance metric is vibration attenuation. The goals are to achieve vibration suppression equivalent to 5 percent passive damping in selected models and 15 percent active damping in selected modes. Various aspects of this experiment are presented in viewgraph form.

Too Hard, Too Soft or Just about Right: Paradigms in Music Teachers' Action Research

ERIC Educational Resources Information Center

Cain, Tim

2012-01-01

This article considers some paradigms of educational research, and their relation to teachers' action research in their classrooms or studios. The positivist/scientific paradigm and the interpretive/naturalist paradigm are examined, with reference to two cases of music teachers' action research studies. These studies are found to be flawed because…

Paradigms of mangroves in treatment of anthropogenic wastewater pollution.

PubMed

Ouyang, Xiaoguang; Guo, Fen

2016-02-15

Mangroves have been increasingly recognized for treating wastewater from aquaculture, sewage and other sources with the overwhelming urbanization trend. This study clarified the three paradigms of mangroves in disposing wastewater contaminants: natural mangroves, constructed wetlands (including free water surface and subsurface flow) and mangrove-aquaculture coupling systems. Plant uptake is the common major mechanism for nutrient removal in all the paradigms as mangroves are generally nitrogen and phosphorus limited. Besides, sediments accrete and provide substrates for microbial activities, thereby removing organic matter and nutrients from wastewater in natural mangroves and constructed wetlands. Among the paradigms, the mangrove-aquaculture coupling system was determined to be the optimal alternative for aquaculture wastewater treatment by multi-criterion decision making. Sensitivity analysis shows variability of alternative ranking but underpins the coupling system as the most environment-friendly and cost-efficient option. Mangrove restoration is expected to be achievable if aquaculture ponds are planted with mangrove seedlings, creating the coupling system. Copyright © 2015 Elsevier B.V. All rights reserved.

Competing Paradigms: The Dilemmas and Insights of an ELT Teacher Educator

ERIC Educational Resources Information Center

Yavuz, Aysun

2012-01-01

In this paper, the writer discusses the philosophical underpinnings of the two dominant research methods in social sciences; quantitative and qualitative paradigms. The natures of two paradigms are quite different so this leads many researchers to discuss these issues in a comparative way. This paper tackles the knowledge and understanding of…

Bonds or Bargains: Relationship Paradigms and Their Significance for Marital Therapy.

ERIC Educational Resources Information Center

Johnson, Sue

1986-01-01

Discusses contrasting conceptual paradigms describing the nature of intimate relationships. Relationships may be viewed in terms of a rational bargain or as an emotional bond. The implications of each paradigm for the process of marital therapy and the role of bonding and attachment in adult intimacy are prescribed. Implications for marital…

A Fractured Fable: "The Three Little Pigs" and Using Multiple Paradigms

ERIC Educational Resources Information Center

Hurt, Andrew C.; Callahan, Jamie L.

2013-01-01

Paradigms aid organizational researchers in their quest to find the "truth" of a particular event, phenomenon, activity, or topic and by providing them a framework with which to make assumptions about the nature of society and reality. According to Burrell and Morgan (1978), organizational researchers use one of four paradigms:…

Cancer research in need of a scientific revolution: Using 'paradigm shift' as a method of investigation.

PubMed

Wion, Didier; Appaix, Florence; Burruss, Meriwether; Berger, Francois; van der Sanden, Boudewijn

2015-09-01

Despite important human and financial resources and considerable accumulation of scientific publications, patents, and clinical trials, cancer research has been slow in achieving a therapeutic revolution similar to the one that occurred in the last century for infectious diseases. It has been proposed that science proceeds not only by accumulating data but also through paradigm shifts. Here, we propose to use the concept of 'paradigm shift' as a method of investigation when dominant paradigms fail to achieve their promises. The first step in using the 'paradigm shift' method in cancer research requires identifying its founding paradigms. In this review, two of these founding paradigms will be discussed: (i) the reification of cancer as a tumour mass and (ii) the translation of the concepts issued from infectious disease in cancer research. We show how these founding paradigms can generate biases that lead to over-diagnosis and over-treatment and also hamper the development of curative cancer therapies. We apply the 'paradigm shift' method to produce perspective reversals consistent with current experimental evidence. The 'paradigm shift' method enlightens the existence of a tumour physiologic-prophylactic-pathologic continuum. It integrates the target/antitarget concept and that cancer is also an extracellular disease. The 'paradigm shift' method has immediate implications for cancer prevention and therapy. It could be a general method of investigation for other diseases awaiting therapy.

Measuring listening effort: driving simulator vs. simple dual-task paradigm

PubMed Central

Wu, Yu-Hsiang; Aksan, Nazan; Rizzo, Matthew; Stangl, Elizabeth; Zhang, Xuyang; Bentler, Ruth

2014-01-01

Objectives The dual-task paradigm has been widely used to measure listening effort. The primary objectives of the study were to (1) investigate the effect of hearing aid amplification and a hearing aid directional technology on listening effort measured by a complicated, more real world dual-task paradigm, and (2) compare the results obtained with this paradigm to a simpler laboratory-style dual-task paradigm. Design The listening effort of adults with hearing impairment was measured using two dual-task paradigms, wherein participants performed a speech recognition task simultaneously with either a driving task in a simulator or a visual reaction-time task in a sound-treated booth. The speech materials and road noises for the speech recognition task were recorded in a van traveling on the highway in three hearing aid conditions: unaided, aided with omni directional processing (OMNI), and aided with directional processing (DIR). The change in the driving task or the visual reaction-time task performance across the conditions quantified the change in listening effort. Results Compared to the driving-only condition, driving performance declined significantly with the addition of the speech recognition task. Although the speech recognition score was higher in the OMNI and DIR conditions than in the unaided condition, driving performance was similar across these three conditions, suggesting that listening effort was not affected by amplification and directional processing. Results from the simple dual-task paradigm showed a similar trend: hearing aid technologies improved speech recognition performance, but did not affect performance in the visual reaction-time task (i.e., reduce listening effort). The correlation between listening effort measured using the driving paradigm and the visual reaction-time task paradigm was significant. The finding showing that our older (56 to 85 years old) participants’ better speech recognition performance did not result in reduced

The Predictive Processing Paradigm Has Roots in Kant

PubMed Central

Swanson, Link R.

2016-01-01

Predictive processing (PP) is a paradigm in computational and cognitive neuroscience that has recently attracted significant attention across domains, including psychology, robotics, artificial intelligence and philosophy. It is often regarded as a fresh and possibly revolutionary paradigm shift, yet a handful of authors have remarked that aspects of PP seem reminiscent of the work of 18th century philosopher Immanuel Kant. To date there have not been any substantive discussions of how exactly PP links back to Kant. In this article, I argue that several core aspects of PP were anticipated by Kant (1996/1787) in his works on perception and cognition. Themes from Kant active in PP include: (1) the emphasis on “top-down” generation of percepts; (2) the role of “hyperpriors”; (3) the general function of “generative models”; (4) the process of “analysis-by-synthesis”; and (5) the crucial role of imagination in perception. In addition to these, I also point out that PP echoes Kant’s general project in that it aims to explain how minds track causal structure in the world using only sensory data, and that it uses a reverse-engineer or “top-down” method of analysis. I then locate a possible source of Kant’s influence on PP by tracing the paradigm back to Hermann von Helmholtz, who saw himself as providing a scientific implementation of Kant’s conclusions. I conclude by arguing that PP should not be regarded as a new paradigm, but is more appropriately understood as the latest incarnation of an approach to perception and cognition initiated by Kant and refined by Helmholtz. PMID:27777555

Measuring the interrelations among multiple paradigms of visual attention: an individual differences approach.

PubMed

Huang, Liqiang; Mo, Lei; Li, Ying

2012-04-01

A large part of the empirical research in the field of visual attention has focused on various concrete paradigms. However, as yet, there has been no clear demonstration of whether or not these paradigms are indeed measuring the same underlying construct. We collected a very large data set (nearly 1.3 million trials) to address this question. We tested 257 participants on nine paradigms: conjunction search, configuration search, counting, tracking, feature access, spatial pattern, response selection, visual short-term memory, and change blindness. A fairly general attention factor was identified. Some of the participants were also tested on eight other paradigms. This general attention factor was found to be correlated with intelligence, visual marking, task switching, mental rotation, and Stroop task. On the other hand, a few paradigms that are very important in the attention literature (attentional capture, consonance-driven orienting, and inhibition of return) were found to be dissociated from this general attention factor.

Reviving Campbell's paradigm for attitude research.

PubMed

Kaiser, Florian G; Byrka, Katarzyna; Hartig, Terry

2010-11-01

Because people often say one thing and do another, social psychologists have abandoned the idea of a simple or axiomatic connection between attitude and behavior. Nearly 50 years ago, however, Donald Campbell proposed that the root of the seeming inconsistency between attitude and behavior lies in disregard of behavioral costs. According to Campbell, attitude- behavior gaps are empirical chimeras. Verbal claims and other overt behaviors regarding an attitude object all arise from one "behavioral disposition." In this article, the authors present the constituents of and evidence for a paradigm for attitude research that describes individual behavior as a function of a person's attitude level and the costs of the specific behavior involved. In the authors' version of Campbell's paradigm, they propose a formal and thus axiomatic rather than causal relationship between an attitude and its corresponding performances. The authors draw implications of their proposal for mainstream attitude theory, empirical research, and applications concerning attitudes.

Re-Visions of Psychology: Feminism as a Paradigm of Scientific Inquiry.

ERIC Educational Resources Information Center

Brownell, Arlene

An intellectual revolution is described in which the logic-centered, value-free model that has served as the foundation for paradigms in psychology is being reevaluated. As part of the intellectual revolution, feminism is presented as a paradigm of scientific inquiry meeting Thomas Kuhn's definition. The question is posed of whether psychologists…

Are Leader Stereotypes Masculine? A Meta-Analysis of Three Research Paradigms

ERIC Educational Resources Information Center

Koenig, Anne M.; Eagly, Alice H.; Mitchell, Abigail A.; Ristikari, Tiina

2011-01-01

This meta-analysis examined the extent to which stereotypes of leaders are culturally masculine. The primary studies fit into 1 of 3 paradigms: (a) In Schein's (1973) "think manager-think male paradigm", 40 studies with 51 effect sizes compared the similarity of male and leader stereotypes and the similarity of female and leader…

Communities of Practice: A Research Paradigm for the Mixed Methods Approach

ERIC Educational Resources Information Center

Denscombe, Martyn

2008-01-01

The mixed methods approach has emerged as a "third paradigm" for social research. It has developed a platform of ideas and practices that are credible and distinctive and that mark the approach out as a viable alternative to quantitative and qualitative paradigms. However, there are also a number of variations and inconsistencies within the mixed…

2014 Space Radiation Standing Review Panel

NASA Technical Reports Server (NTRS)

Steinberg, Susan

2015-01-01

The 2014 Space Radiation Standing Review Panel (from here on referred to as the SRP) participated in a WebEx/teleconference with members of the Space Radiation Program Element, representatives from the Human Research Program (HRP), the National Space Biomedical Research Institute (NSBRI), and NASA Headquarters on November 21, 2014 (list of participants is in Section XI of this report). The SRP reviewed the updated Research Plan for the Risk of Cardiovascular Disease and Other Degenerative Tissue Effects from Radiation Exposure (Degen Risk). The SRP also received a status update on the Risk of Acute and Late Central Nervous System Effects from Radiation Exposure (CNS Risk), the Risk of Acute Radiation Syndromes Due to Solar Particle Events (ARS Risk), and the Risk of Radiation Carcinogenesis (Cancer Risk). The SRP thought the teleconference was very informative and that the Space Radiation Program Element did a great job of outlining where the Element is with respect to our state of knowledge on the risks of carcinogenesis, central nervous system effects, and the risk of cardiovascular disease and other degenerative tissue effects from exposure to space radiation. The SRP was impressed with the quality of research that is being conducted and the progress the Space Radiation Program Element has made in the past year. While much work has been done, the SRP had a few remaining questions regarding the broad applicability of these findings to a manned deep space mission (in terms of cognitive function, the paradigms were still hippocampal based and also using Alzheimer disease models). The SRP believes that NASA should consider developing an approach to follow astronauts long-term (beyond retirement) for potential side-effects/risks of space exposure that may be unknown. Radiation toxicities often occur decades after exposure, and potential consequences would be missed if intensified exams stop after retirement of the astronauts. In addition, while cancer is one

Role of the area postrema in radiation-induced taste aversion learning and emesis in cats

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

Rabin, B.M.; Hunt, W.A.; Chedester, A.L.

1986-01-01

The role of the area postrema in radiation-induced emesis and taste aversion learning and the relationship between these behaviors were studied in cats. The potential involvement of neural factors which might be independent of the area postrema was minimized by using low levels of ionizing radiation (100 rads at a dose rate of 40 rads/min) to elicit a taste aversion, and by using body-only exposures (4500 and 6000 rads at 450 rads/min) to produce emesis. Lesions of the area postrema disrupted both taste aversion learning and emesis following irradiation. These results, which indicate that the area postrema is involved inmore » the mediation of both radiation-induced emesis and taste aversion learning in cats under these experimental conditions, are interpreted as being consistent with the hypotheses that similar mechanisms mediate both responses to exposure to ionizing radiation, and that the taste aversion learning paradigm can therefore serve as a model system for studying radiation-induced emesis.« less

The role of dental hygiene in caries management: a new paradigm.

PubMed

Young, Douglas A; Lyon, Lucinda; Azevedo, Shelly

2010-01-01

Dental caries is the most common disease of children and remains a significant oral health problem worldwide for both children and adults. The traditional paradigm of treating dental caries solely by "drilling and filling," brushing and flossing and lowering sugar intake has evolved. Current science in the management of dental caries suggests a clear focus on the reduction of responsible infectious agents, remineralization of non-cavitated lesions and minimally invasive restorative approaches whenever possible. The paradigm shift is away from a purely surgical approach toward more preventive and curative clinical protocols. This paper provides a review of this caries management methodology and explores the role of the dental hygienist in this paradigm change.

The word class effect in the picture–word interference paradigm

PubMed Central

Janssen, Niels; Melinger, Alissa; Mahon, Bradford Z.; Finkbeiner, Matthew; Caramazza, Alfonso

2010-01-01

The word class effect in the picture–word interference paradigm is a highly influential finding that has provided some of the most compelling support for word class constraints on lexical selection. However, methodological concerns called for a replication of the most convincing of those effects. Experiment 1 was a direct replication of Pechmann and Zerbst (2002; Experiment 4). Participants named pictures of objects in the context of noun and adverb distractors. Naming took place in bare noun and sentence frame contexts. A word class effect emerged in both bare noun and sentence frame naming conditions, suggesting a semantic origin of the effect. In Experiment 2, participants named objects in the context of noun and verb distractors whose word class relationship to the target and imageability were orthogonally manipulated. As before, naming took place in bare noun and sentence frame naming contexts. In both naming contexts, distractor imageability but not word class affected picture naming latencies. These findings confirm the sensitivity of the picture–word interference paradigm to distractor imageability and suggest the paradigm is not sensitive to distractor word class. The results undermine the use of the word class effect in the picture–word interference paradigm as supportive of word class constraints during lexical selection. PMID:19998070

Changing environments or shifting paradigms? Strategic decision making toward water protection in Helsinki, 1850-2000.

PubMed

Laakkonen, Simo; Laurila, Sari

2007-04-01

The study examines the history of strategic decision-making concerning water protection in Helsinki, 1850-2000. We identified five major strategic decisions that occurred during the study period. The results indicate that strategic decision-making evolves in long-term policy cycles that last on average 20-30 years. New policy cycles are caused by paradigm shifts. Paradigms are shared and predominant ways of understanding reality that help when groups must act to solve common and complex environmental problems. However the internal structure and external dynamics of paradigms are contradictory. Although paradigms serve initially as means to redefine problems and find creative solutions, as time goes by each paradigm seems to become also a barrier that restricts the introduction of new ways of thinking and acting. The power of paradigms lies in the fact that they can be defined as scientific but also social, political, or cultural agreements depending on the context.

Investigating true and false confessions within a novel experimental paradigm.

PubMed

Russano, Melissa B; Meissner, Christian A; Narchet, Fadia M; Kassin, Saul M

2005-06-01

The primary goal of the current study was to develop a novel experimental paradigm with which to study the influence of psychologically based interrogation techniques on the likelihood of true and false confessions. The paradigm involves guilty and innocent participants being accused of intentionally breaking an experimental rule, or "cheating." In the first demonstration of this paradigm, we explored the influence of two common police interrogation tactics: minimization and an explicit offer of leniency, or a "deal." Results indicated that guilty persons were more likely to confess than innocent persons, and that the use of minimization and the offer of a deal increased the rate of both true and false confessions. Police investigators are encouraged to avoid interrogation techniques that imply or directly promise leniency, as they appear to reduce the diagnostic value of any confession that is elicited.

Diet and Cancer: The Fourth Paradigm

Cancer.gov

Walter C. Willett, MD, DrPH, an international expert in diet and nutrition, with posts as a Professor of Epidemiology and Nutrition and Chairman of the Department of Nutrition at Harvard School of Public Health and as Professor of Medicine at Harvard Medical School, presented "Diet and Cancer: The Fourth Paradigm".

Turbomachinery computational fluid dynamics: asymptotes and paradigm shifts.

PubMed

Dawes, W N

2007-10-15

This paper reviews the development of computational fluid dynamics (CFD) specifically for turbomachinery simulations and with a particular focus on application to problems with complex geometry. The review is structured by considering this development as a series of paradigm shifts, followed by asymptotes. The original S1-S2 blade-blade-throughflow model is briefly described, followed by the development of two-dimensional then three-dimensional blade-blade analysis. This in turn evolved from inviscid to viscous analysis and then from steady to unsteady flow simulations. This development trajectory led over a surprisingly small number of years to an accepted approach-a 'CFD orthodoxy'. A very important current area of intense interest and activity in turbomachinery simulation is in accounting for real geometry effects, not just in the secondary air and turbine cooling systems but also associated with the primary path. The requirements here are threefold: capturing and representing these geometries in a computer model; making rapid design changes to these complex geometries; and managing the very large associated computational models on PC clusters. Accordingly, the challenges in the application of the current CFD orthodoxy to complex geometries are described in some detail. The main aim of this paper is to argue that the current CFD orthodoxy is on a new asymptote and is not in fact suited for application to complex geometries and that a paradigm shift must be sought. In particular, the new paradigm must be geometry centric and inherently parallel without serial bottlenecks. The main contribution of this paper is to describe such a potential paradigm shift, inspired by the animation industry, based on a fundamental shift in perspective from explicit to implicit geometry and then illustrate this with a number of applications to turbomachinery.

Comparison of fMRI paradigms assessing visuospatial processing: Robustness and reproducibility

PubMed Central

Herholz, Peer; Zimmermann, Kristin M.; Westermann, Stefan; Frässle, Stefan; Jansen, Andreas

2017-01-01

The development of brain imaging techniques, in particular functional magnetic resonance imaging (fMRI), made it possible to non-invasively study the hemispheric lateralization of cognitive brain functions in large cohorts. Comprehensive models of hemispheric lateralization are, however, still missing and should not only account for the hemispheric specialization of individual brain functions, but also for the interactions among different lateralized cognitive processes (e.g., language and visuospatial processing). This calls for robust and reliable paradigms to study hemispheric lateralization for various cognitive functions. While numerous reliable imaging paradigms have been developed for language, which represents the most prominent left-lateralized brain function, the reliability of imaging paradigms investigating typically right-lateralized brain functions, such as visuospatial processing, has received comparatively less attention. In the present study, we aimed to establish an fMRI paradigm that robustly and reliably identifies right-hemispheric activation evoked by visuospatial processing in individual subjects. In a first study, we therefore compared three frequently used paradigms for assessing visuospatial processing and evaluated their utility to robustly detect right-lateralized brain activity on a single-subject level. In a second study, we then assessed the test-retest reliability of the so-called Landmark task–the paradigm that yielded the most robust results in study 1. At the single-voxel level, we found poor reliability of the brain activation underlying visuospatial attention. This suggests that poor signal-to-noise ratios can become a limiting factor for test-retest reliability. This represents a common detriment of fMRI paradigms investigating visuospatial attention in general and therefore highlights the need for careful considerations of both the possibilities and limitations of the respective fMRI paradigm–in particular, when being

Evolving conservation paradigms for the Anthropocene

Treesearch

Ariel E. Lugo

2014-01-01

The Anthropocene will have fundamental effects on the species composition, function, and structure of the ecosystems of the world. Land management agencies such as the USDA Forest Service will need to adapt their policies and conservation activities to avoid engaging in continuous conflict with natural processes and unfamiliar biotic assemblages. Conservation paradigms...

Decision Making: New Paradigm for Education.

ERIC Educational Resources Information Center

Wales, Charles E.; And Others

1986-01-01

Defines education's new paradigm as schooling based on decision making, the critical thinking skills serving it, and the knowledge base supporting it. Outlines a model decision-making process using a hypothetical breakfast problem; a late riser chooses goals, generates ideas, develops an action plan, and implements and evaluates it. (4 references)…

Fiber-optic dosimeters for radiation therapy

NASA Astrophysics Data System (ADS)

Li, Enbang; Archer, James

2017-10-01

According to the figures provided by the World Health Organization, cancer is a leading cause of death worldwide, accounting for 8.8 million deaths in 2015. Radiation therapy, which uses x-rays to destroy or injure cancer cells, has become one of the most important modalities to treat the primary cancer or advanced cancer. The newly developed microbeam radiation therapy (MRT), which uses highly collimated, quasi-parallel arrays of x-ray microbeams (typically 50 μm wide and separated by 400 μm) produced by synchrotron sources, represents a new paradigm in radiotherapy and has shown great promise in pre-clinical studies on different animal models. Measurements of the absorbed dose distribution of microbeams are vitally important for clinical acceptance of MRT and for developing quality assurance systems for MRT, hence are a challenging and important task for radiation dosimetry. On the other hand, during the traditional LINAC based radiotherapy and breast cancer brachytherapy, skin dose measurements and treatment planning also require a high spatial resolution, tissue equivalent, on-line dosimeter that is both economical and highly reliable. Such a dosimeter currently does not exist and remains a challenge in the development of radiation dosimetry. High resolution, water equivalent, optical and passive x-ray dosimeters have been developed and constructed by using plastic scintillators and optical fibers. The dosimeters have peak edge-on spatial resolutions ranging from 50 to 500 microns in one dimension, with a 10 micron resolution dosimeter under development. The developed fiber-optic dosimeters have been test with both LINAC and synchrotron x-ray beams. This work demonstrates that water-equivalent and high spatial resolution radiation detection can be achieved with scintillators and optical fiber systems. Among other advantages, the developed fiber-optic probes are also passive, energy independent, and radiation hard.

The gap-startle paradigm to assess auditory temporal processing: Bridging animal and human research.

PubMed

Fournier, Philippe; Hébert, Sylvie

2016-05-01

The gap-prepulse inhibition of the acoustic startle (GPIAS) paradigm is the primary test used in animal research to identify gap detection thresholds and impairment. When a silent gap is presented shortly before a loud startling stimulus, the startle reflex is inhibited and the extent of inhibition is assumed to reflect detection. Here, we applied the same paradigm in humans. One hundred and fifty-seven normal-hearing participants were tested using one of five gap durations (5, 25, 50, 100, 200 ms) in one of the following two paradigms-gap-embedded in or gap-following-the continuous background noise. The duration-inhibition relationship was observable for both conditions but followed different patterns. In the gap-embedded paradigm, GPIAS increased significantly with gap duration up to 50 ms and then more slowly up to 200 ms (trend only). In contrast, in the gap-following paradigm, significant inhibition-different from 0--was observable only at gap durations from 50 to 200 ms. The finding that different patterns are found depending on gap position within the background noise is compatible with distinct mechanisms underlying each of the two paradigms. © 2016 Society for Psychophysiological Research.

Yakov Zeldovich and the Cosmic Web Paradigm

NASA Astrophysics Data System (ADS)

Einasto, Jaan

2016-10-01

I discuss the formation of the modern cosmological paradigm. In more detail I describe the early study of dark matter and cosmic web and the role of Yakov Zeldovich in the formation of the present concepts on these subjects.

Beyond desertification: New paradigms for dryland landscapes

USDA-ARS?s Scientific Manuscript database

The dryland desertification paradigm focuses on losses of ecosystem services accompanying transitions from grasslands to systems dominated by bare ground or woody plants unpalatable for domestic livestock. However, recent studies reveal complex transitions across a range of environmental conditions ...

After pluralism: towards a new, integrated psychoanalytic paradigm.

PubMed

Jiménez, Juan Pablo

2006-12-01

After a restatement of the isolationism of psychoanalysis from allied disciplines, and an examination of some of the reasons for the diversity of schools of thought and the fragmentation of psychoanalytic knowledge, the author suggests the need to adopt principles of correspondence or external coherence along with those of hermeneutic coherence to validate psychoanalytic hypotheses. Recent developments in neurocognitive science have come to the aid of psychoanalysis in this period of crisis, resulting in the proposition of integrating both areas to form a new paradigm for the construction of the theory of the mind. This emerging paradigm tries to integrate clinical knowledge with neurocognitive science, findings from studies on the process and outcome of psychotherapy, research into the early mother-infant relationship, and developmental psychopathology. The author examines theoretical- technical models based on the concept of drives and of relationships in the light of interdisciplinary findings. He concludes that the relational model has a broad empirical base, except when the concept of drives is discredited. Interdisciplinary findings have led to the positing of the replacement of the Freudian model of drives with a model of motivational systems centred on affective processes. He draws certain conclusions which have a bearing on the technique of psychoanalytic treatment. These arise from the adoption of the new integrated paradigm.

Old High German Nominal Morphology Revisited: A Fresh Look at Old Paradigms

ERIC Educational Resources Information Center

Luiten, Tyler V.

2011-01-01

This study employs a relational database consisting of thousands of Old High German (OHG) nominal attestations to reconstruct noun class paradigms found primarily in the four OHG texts extensive enough to provide complete nominal paradigms: "Isidor", "Benediktinerregel", "Tatian" and Otfrid von Weissenburg's "Evangelienbuch". This study captures…

More than Method?: A Discussion of Paradigm Differences within Mixed Methods Research

ERIC Educational Resources Information Center

Harrits, Gitte Sommer

2011-01-01

This article challenges the idea that mixed methods research (MMR) constitutes a coherent research paradigm and explores how different research paradigms exist within MMR. Tracing paradigmatic differences at the level of methods, ontology, and epistemology, two MMR strategies are discussed: nested analysis, recently presented by the American…

Radiation therapy: age-related macular degeneration.

PubMed

Mendez, Carlos A Medina; Ehlers, Justis P

2013-01-01

Age-related macular degeneration (AMD) is the leading cause of severe irreversible vision loss in patients over the age of 50 years in the developed world. Neovascular AMD (NVAMD) is responsible for 90% of the cases with severe visual loss. In the last decade, the treatment paradigm for NVAMD has been transformed by the advent of anti-vascular endothelial growth factor therapy. Despite the excellent results of anti-vascular endothelial growth factor therapy, frequent injections remain a necessity for most patients. The burden of these frequent visits as well as the cumulative risks of indefinite intravitreal injections demand continued pursuit of more enduring therapy that provides similar functional results. Radiotherapy has been studied for two decades as a potential therapy for NVAMD. Because of its antiangiogenic properties, radiation therapy remains a promising potential adjunctive resource for the treatment of choroidal neovascularization secondary to NVAMD. This review considers the past, present and future of radiation as a treatment or combination treatment of NVAMD. Copyright © 2013 S. Karger AG, Basel.

Rivaling paradigms in psychiatric neurosurgery: adjustability versus quick fix versus minimal-invasiveness.

PubMed

Müller, Sabine; Riedmüller, Rita; van Oosterhout, Ansel

2015-01-01

In the wake of deep brain stimulation (DBS) development, ablative neurosurgical procedures are seeing a comeback, although they had been discredited and nearly completely abandoned in the 1970s because of their unethical practice. Modern stereotactic ablative procedures as thermal or radiofrequency ablation, and particularly radiosurgery (e.g., Gamma Knife) are much safer than the historical procedures, so that a re-evaluation of this technique is required. The different approaches of modern psychiatric neurosurgery refer to different paradigms: microsurgical ablative procedures is based on the paradigm 'quick fix,' radiosurgery on the paradigm 'minimal-invasiveness,' and DBS on the paradigm 'adjustability.' From a mere medical perspective, none of the procedures is absolutely superior; rather, they have different profiles of advantages and disadvantages. Therefore, individual factors are crucial in decision-making, particularly the patients' social situation, individual preferences, and individual attitudes. The different approaches are not only rivals, but also enriching mutually. DBS is preferable for exploring new targets, which may become candidates for ablative microsurgery or radiosurgery.

A New Paradigm for Ovarian Sex Cord-Stromal Tumor Development

DTIC Science & Technology

2016-05-01

1 AWARD NUMBER: W81XWH-15-1-0082 TITLE: A New Paradigm for Ovarian Sex Cord-Stromal Tumor Development PRINCIPAL INVESTIGATOR: Qinglei Li...5a. CONTRACT NUMBER A New Paradigm for Ovarian Sex Cord-Stromal Tumor Development 5b. GRANT NUMBER W81XWH-15-1-0082 5c. PROGRAM ELEMENT NUMBER 6...role of sustained activation of oocyte TGFBR1 in ovarian tumor development using an in vitro approach. 2. Keywords Ovarian tumor, Sex cord

Reexamining Fourth Generation War as a Paradigm for Future War

DTIC Science & Technology

2014-12-04

Kuhn’s theory, a paradigm shift in science has far-reaching effects on the broader world . 4GW theorists embrace this aspect of Kuhn’s “paradigm...with the perplexing and hostile challenges of the chaotic post-Cold War world for which the ‘rules’ have not yet been written. The three-block war...events within its framework. In short, it was ready-made for military officers seeking a unifying frame for understanding the world and their experiences

Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P.; Hededal, C.; Mizuno, Yosuke; Fishman, G. Jerry; Hartmann, D. H.

2006-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), supernova remnants, and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that particle acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration' is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different spectral properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations of relativistic jets and try to make a connection with observations.

A movement ecology paradigm for unifying organismal movement research

PubMed Central

Nathan, Ran; Getz, Wayne M.; Revilla, Eloy; Holyoak, Marcel; Kadmon, Ronen; Saltz, David; Smouse, Peter E.

2008-01-01

Movement of individual organisms is fundamental to life, quilting our planet in a rich tapestry of phenomena with diverse implications for ecosystems and humans. Movement research is both plentiful and insightful, and recent methodological advances facilitate obtaining a detailed view of individual movement. Yet, we lack a general unifying paradigm, derived from first principles, which can place movement studies within a common context and advance the development of a mature scientific discipline. This introductory article to the Movement Ecology Special Feature proposes a paradigm that integrates conceptual, theoretical, methodological, and empirical frameworks for studying movement of all organisms, from microbes to trees to elephants. We introduce a conceptual framework depicting the interplay among four basic mechanistic components of organismal movement: the internal state (why move?), motion (how to move?), and navigation (when and where to move?) capacities of the individual and the external factors affecting movement. We demonstrate how the proposed framework aids the study of various taxa and movement types; promotes the formulation of hypotheses about movement; and complements existing biomechanical, cognitive, random, and optimality paradigms of movement. The proposed framework integrates eclectic research on movement into a structured paradigm and aims at providing a basis for hypothesis generation and a vehicle facilitating the understanding of the causes, mechanisms, and spatiotemporal patterns of movement and their role in various ecological and evolutionary processes. ”Now we must consider in general the common reason for moving with any movement whatever.“ (Aristotle, De Motu Animalium, 4th century B.C.) PMID:19060196

Degrading emotional memories induced by a virtual reality paradigm.

PubMed

Cuperus, Anne A; Laken, Maarten; van den Hout, Marcel A; Engelhard, Iris M

2016-09-01

In Eye Movement and Desensitization and Reprocessing (EMDR) therapy, a dual-task approach is used: patients make horizontal eye movements while they recall aversive memories. Studies showed that this reduces memory vividness and/or emotionality. A strong explanation is provided by working memory theory, which suggests that other taxing dual-tasks are also effective. Experiment 1 tested whether a visuospatial task which was carried out while participants were blindfolded taxes working memory. Experiment 2 tested whether this task degrades negative memories induced by a virtual reality (VR) paradigm. In experiment 1, participants responded to auditory cues with or without simultaneously carrying out the visuospatial task. In experiment 2, participants recalled negative memories induced by a VR paradigm. The experimental group simultaneously carried out the visuospatial task, and a control group merely recalled the memories. Changes in self-rated memory vividness and emotionality were measured. The slowing down of reaction times due to the visuospatial task indicated that its cognitive load was greater than the load of the eye movements task in previous studies. The task also led to reductions in emotionality (but not vividness) of memories induced by the VR paradigm. Weaknesses are that only males were tested in experiment 1, and the effectiveness of the VR fear/trauma induction was not assessed with ratings of mood or intrusions in experiment 2. The results suggest that the visuospatial task may be applicable in clinical settings, and the VR paradigm may provide a useful method of inducing negative memories. Copyright © 2016 Elsevier Ltd. All rights reserved.

Moral Developmental Science between Changing Paradigms

ERIC Educational Resources Information Center

Keller, Monika

2012-01-01

This review encompasses a time-span of about 50 years of research on morality and moral development. It discusses Kohlberg's (1984) work as a milestone that constituted the cognitive developmental viewpoint of morality and that dominated research for about three decades. In this paradigm the role of reasoning and deliberation was emphasized as the…

Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers.

PubMed

Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

2015-06-02

Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers.

Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers

PubMed Central

Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

2015-01-01

Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers. PMID:26035687

Research Paradigms and Their Use and Importance in Theological Inquiry and Education

ERIC Educational Resources Information Center

Mittwede, Steven K.

2012-01-01

A survey and analysis of four major research paradigms--positivism, postpositivism, critical theory and constructivism--reveal that all have been applied effectively in recent theological inquiry. Although these paradigms might resemble worldviews to some extent, they are not so all-encompassing. Rather, they are essentially matrices of deeply…

Implications for Teacher Effectiveness Research in Deaf Education from the Cognitive Paradigm.

ERIC Educational Resources Information Center

Mertens, Donna M.

The paper identifies a paradigm shift in research on teaching effectiveness from the process-product approach to explanations from cognitive psychology related to mediating variables which intervene between teacher behavior and pupil performance. Implications of this paradigm shift for research on the effectiveness of teachers of deaf students are…

Enabling a New Planning and Scheduling Paradigm

NASA Technical Reports Server (NTRS)

Jaap, John; Davis, Elizabeth

2004-01-01

The Flight Projects Directorate at NASA's Marshall Space Flight Center is developing a new planning and scheduling environment and a new scheduling algorithm to enable a paradigm shift in planning and scheduling concepts. Over the past 33 years Marshall has developed and evolved a paradigm for generating payload timelines for Skylab, Spacelab, various other Shuttle payloads, and the International Space Station. The current paradigm starts by collecting the requirements, called "tasks models," from the scientists and technologists for the tasks that they want to be done. Because of shortcomings in the current modeling schema, some requirements are entered as notes. Next a cadre with knowledge of vehicle and hardware modifies these models to encompass and be compatible with the hardware model; again, notes are added when the modeling schema does not provide a better way to represent the requirements. Finally, another cadre further modifies the models to be compatible with the scheduling engine. This last cadre also submits the models to the scheduling engine or builds the timeline manually to accommodate requirements that are expressed in notes. A future paradigm would provide a scheduling engine that accepts separate science models and hardware models. The modeling schema would have the capability to represent all the requirements without resorting to notes. Furthermore, the scheduling engine would not require that the models be modified to account for the capabilities (limitations) of the scheduling engine. The enabling technology under development at Marshall has three major components. (1) A new modeling schema allows expressing all the requirements of the tasks without resorting to notes or awkward contrivances. The chosen modeling schema is both maximally expressive and easy to use. It utilizes graphics methods to show hierarchies of task constraints and networks of temporal relationships. (2) A new scheduling algorithm automatically schedules the models

Perspectives on Emerging/Novel Computing Paradigms and Future Aerospace Workforce Environments

NASA Technical Reports Server (NTRS)

Noor, Ahmed K.

2003-01-01

The accelerating pace of the computing technology development shows no signs of abating. Computing power reaching 100 Tflop/s is likely to be reached by 2004 and Pflop/s (10(exp 15) Flop/s) by 2007. The fundamental physical limits of computation, including information storage limits, communication limits and computation rate limits will likely be reached by the middle of the present millennium. To overcome these limits, novel technologies and new computing paradigms will be developed. An attempt is made in this overview to put the diverse activities related to new computing-paradigms in perspective and to set the stage for the succeeding presentations. The presentation is divided into five parts. In the first part, a brief historical account is given of development of computer and networking technologies. The second part provides brief overviews of the three emerging computing paradigms grid, ubiquitous and autonomic computing. The third part lists future computing alternatives and the characteristics of future computing environment. The fourth part describes future aerospace workforce research, learning and design environments. The fifth part lists the objectives of the workshop and some of the sources of information on future computing paradigms.

Dynamic cerebral autoregulation during brain activation paradigms.

PubMed

Panerai, Ronney B; Moody, Michelle; Eames, Penelope J; Potter, John F

2005-09-01

Dynamic cerebral autoregulation (CA) describes the transient response of cerebral blood flow (CBF) to rapid changes in arterial blood pressure (ABP). We tested the hypothesis that the efficiency of dynamic CA is increased by brain activation paradigms designed to induce hemispheric lateralization. CBF velocity [CBFV; bilateral, middle cerebral artery (MCA)], ABP, ECG, and end-tidal Pco(2) were continuously recorded in 14 right-handed healthy subjects (21-43 yr of age), in the seated position, at rest and during 10 repeated presentations (30 s on-off) of a word generation test and a constructional puzzle. Nonstationarities were not found during rest or activation. Transfer function analysis of the ABP-CBFV (i.e., input-output) relation was performed for the 10 separate 51.2-s segments of data during activation and compared with baseline data. During activation, the coherence function below 0.05 Hz was significantly increased for the right MCA recordings for the puzzle tasks compared with baseline values (0.36 +/- 0.16 vs. 0.26 +/- 0.13, P < 0.05) and for the left MCA recordings for the word paradigm (0.48 +/- 0.23 vs. 0.29 +/- 0.16, P < 0.05). In the same frequency range, significant increases in gain were observed during the puzzle paradigm for the right (0.69 +/- 0.37 vs. 0.46 +/- 0.32 cm.s(-1).mmHg(-1), P < 0.05) and left (0.61 +/- 0.29 vs. 0.45 +/- 0.24 cm.s(-1).mmHg(-1), P < 0.05) hemispheres and during the word tasks for the left hemisphere (0.66 +/- 0.31 vs. 0.39 +/- 0.15 cm.s(-1).mmHg(-1), P < 0.01). Significant reductions in phase were observed during activation with the puzzle task for the right (-0.04 +/- 1.01 vs. 0.80 +/- 0.86 rad, P < 0.01) and left (0.11 +/- 0.81 vs. 0.57 +/- 0.51 rad, P < 0.05) hemispheres and with the word paradigm for the right hemisphere (0.05 +/- 0.87 vs. 0.64 +/- 0.59 rad, P < 0.05). Brain activation also led to changes in the temporal pattern of the CBFV step response. We conclude that transfer function analysis suggests

E-health beyond technology: analyzing the paradigm shift that lies beneath.

PubMed

Moerenhout, Tania; Devisch, Ignaas; Cornelis, Gustaaf C

2018-03-01

Information and computer technology has come to play an increasingly important role in medicine, to the extent that e-health has been described as a disruptive innovation or revolution in healthcare. The attention is very much focused on the technology itself, and advances that have been made in genetics and biology. This leads to the question: What is changing in medicine today concerning e-health? To what degree could these changes be characterized as a 'revolution'? We will apply the work of Thomas Kuhn, Larry Laudan, Michel Foucault and other philosophers-which offers an alternative understanding of progress and revolution in medicine to the classic discovery-oriented approach-to our analysis. Nowadays, the long-standing curative or reactive paradigm in medicine is facing a crisis due to an aging population, a significant increase in chronic diseases and the development of more expensive diagnostic tools and therapies. This promotes the evolution towards a new paradigm with an emphasis on preventive medicine. E-health constitutes an essential part of this new paradigm that seeks to solve the challenges presented by an aging population, skyrocketing costs and so forth. Our approach changes the focus from the technology itself toward the underlying paradigm shift in medicine. We will discuss the relevance of this approach by applying it to the surge in digital self-tracking through health apps and wearables: the recognition of the underlying paradigm shift leads to a more comprehensive understanding of self-tracking than a solely discovery-oriented or technology-focused view can provide.

Parallels between New Paradigms in Science and in Reading and Literary Theories.

ERIC Educational Resources Information Center

Weaver, Constance

Drawing upon research from a number of fields, this paper explores parallels between new paradigms in the sciences--particularly physics, chemistry, and biology--and new paradigms in reading and literary theory--particularly a socio- or psycholinguistic, semiotic, transactional view of reading and a transactional view of the literary experience.…

Treatment of Children with Speech Oral Placement Disorders (OPDs): A Paradigm Emerges

ERIC Educational Resources Information Center

Bahr, Diane; Rosenfeld-Johnson, Sara

2010-01-01

Epidemiological research was used to develop the Speech Disorders Classification System (SDCS). The SDCS is an important speech diagnostic paradigm in the field of speech-language pathology. This paradigm could be expanded and refined to also address treatment while meeting the standards of evidence-based practice. The article assists that process…

Changing the Paradigm of Air Pollution Monitoring

EPA Science Inventory

Historically, approaches for monitoring air pollution generally use expensive, complex, stationary equipment,^1,2 which limits who collects data, why data are collected, and how data are accessed. This paradigm is changing with the materialization of lower-cost, easy-to...

Effects of covert and overt paradigms in clinical language fMRI.

PubMed

Partovi, Sasan; Konrad, Florian; Karimi, Sasan; Rengier, Fabian; Lyo, John K; Zipp, Lisa; Nennig, Ernst; Stippich, Christoph

2012-05-01

The aim of this study was to assess the intrasubject and intersubject reproducibility of functional magnetic resonance imaging (fMRI) language paradigms on language localization and lateralization. Fourteen healthy volunteers were enrolled prospectively and underwent language fMRI using visually triggered covert and overt sentence generation (SG) and word generation (WG) paradigms. Semiautomated analysis of all functional data was performed using Brain Voyager on an individual basis. Regions of interest for Broca's area, Wernicke's area, and their contralateral homologues were drawn. The Euclidean coordinates of the center of gravidity (x, y, and z) of the respective blood oxygenation level-dependent (BOLD) activation cluster, and the correlation of the measured hemodynamic response to the applied reference function (r), relative BOLD signal change as BOLD signal characteristics were measured in each region of interest. Regional lateralization indexes were calculated for Broca's area, Wernicke's area, and their contralateral homologues separately. Wilcoxon's signed-rank test was applied for statistical comparisons (P values < .05 were considered significant). Ten of the 14 volunteers had three repeated measurements to test intrasession reproducibility and intersession reproducibility. Overall activation rates for the four paradigms were 89% for covert SG, 82% for overt SG, 89% for covert WG, and 100% for overt WG. When comparing covert and overt paradigms, language localization was significantly different in 17% (Euclidean coordinates) and 19% (BOLD signal characteristics), respectively. Language lateralization was significantly different in 75%. Intrasubject and intersubject reproducibility was excellent, with 3.3% significant differences among all five parameters for language localization and 0% significant differences for language lateralization using covert paradigms. Covert language paradigms (SG and WG) provided highly robust and reproducible localization and

An analysis of carrier phase jitter in an MPSK receiver utilizing map estimation. Ph.D. Thesis Semiannual Status Report, Jul. 1993 - Jan. 1994

NASA Technical Reports Server (NTRS)

Osborne, William P.

1994-01-01

The use of 8 and 16 PSK TCM to support satellite communications in an effort to achieve more bandwidth efficiency in a power-limited channel has been proposed. This project addresses the problem of carrier phase jitter in an M-PSK receiver utilizing the high SNR approximation to the maximum aposteriori estimation of carrier phase. In particular, numerical solutions to the 8 and 16 PSK self-noise and phase detector gain in the carrier tracking loop are presented. The effect of changing SNR on the loop noise bandwidth is also discussed. These data are then used to compute variance of phase error as a function of SNR. Simulation and hardware data are used to verify these calculations. The results show that there is a threshold in the variance of phase error versus SNR curves that is a strong function of SNR and a weak function of loop bandwidth. The M-PSK variance thresholds occur at SNR's in the range of practical interest for the use of 8 and 16-PSK TCM. This suggests that phase error variance is an important consideration in the design of these systems.

[Assistance to the climacteric woman: new paradigms].

PubMed

Lorenzi, Dino Roberto Soares De; Catan, Lenita Binelli; Moreira, Karen; Artico, Graziela Rech

2009-01-01

Population aging is a demographic reality for Brazil. Consequently, in the next years it is expected a progressive increase in seeking health care services in the country by women with complaints related to climacterium. Parallel to it, assistance at this part of woman's life has been going through a paradigm shift which has imposed to health professionals a change of attitude in relation to this stage of woman's life. Today it is acknowledged that the climacterium is influenced by biological, psychosocial and cultural factors, whose knowledge is fundamental for planning a more qualified and humanized care. This article proposes a reflection on the paradigm shifts in assistance at climacterium, highlighting important aspects as multidisciplinarity and interdisciplinarity, so as to serve better this portion of population, and provide it with more integrated and individualized care, bringing together knowledge and sensitivity, and always aiming at a better quality of life.

fMRI paradigm designing and post-processing tools

PubMed Central

James, Jija S; Rajesh, PG; Chandran, Anuvitha VS; Kesavadas, Chandrasekharan

2014-01-01

In this article, we first review some aspects of functional magnetic resonance imaging (fMRI) paradigm designing for major cognitive functions by using stimulus delivery systems like Cogent, E-Prime, Presentation, etc., along with their technical aspects. We also review the stimulus presentation possibilities (block, event-related) for visual or auditory paradigms and their advantage in both clinical and research setting. The second part mainly focus on various fMRI data post-processing tools such as Statistical Parametric Mapping (SPM) and Brain Voyager, and discuss the particulars of various preprocessing steps involved (realignment, co-registration, normalization, smoothing) in these software and also the statistical analysis principles of General Linear Modeling for final interpretation of a functional activation result. PMID:24851001

Moving alcohol prevention research forward-Part I: introducing a complex systems paradigm.

PubMed

Apostolopoulos, Yorghos; Lemke, Michael K; Barry, Adam E; Lich, Kristen Hassmiller

2018-02-01

The drinking environment is a complex system consisting of a number of heterogeneous, evolving and interacting components, which exhibit circular causality and emergent properties. These characteristics reduce the efficacy of commonly used research approaches, which typically do not account for the underlying dynamic complexity of alcohol consumption and the interdependent nature of diverse factors influencing misuse over time. We use alcohol misuse among college students in the United States as an example for framing our argument for a complex systems paradigm. A complex systems paradigm, grounded in socio-ecological and complex systems theories and computational modeling and simulation, is introduced. Theoretical, conceptual, methodological and analytical underpinnings of this paradigm are described in the context of college drinking prevention research. The proposed complex systems paradigm can transcend limitations of traditional approaches, thereby fostering new directions in alcohol prevention research. By conceptualizing student alcohol misuse as a complex adaptive system, computational modeling and simulation methodologies and analytical techniques can be used. Moreover, use of participatory model-building approaches to generate simulation models can further increase stakeholder buy-in, understanding and policymaking. A complex systems paradigm for research into alcohol misuse can provide a holistic understanding of the underlying drinking environment and its long-term trajectory, which can elucidate high-leverage preventive interventions. © 2017 Society for the Study of Addiction.

Globalization, technological changes and the search for a new paradigm for women's work.

PubMed

Mitter, S

1999-01-01

This paper comments on a conceptual paradigm that illustrates the context of the opportunities and challenges that the current technology-led globalization has brought to women's employment in Asia. The UN University Institute for New Technologies project provides the basis for this framework/paradigm. This paradigm helps in analyzing the consequences of an emerging techno-economic order that is imported and does not take into account the specific needs of women. It also acknowledged the liberating aspects of new technologies and modernization. At the same time, it emphasizes the role of the state, the family, and women workers' organizations in counteracting the negative consequences of current globalization. Finally, the paradigm was predicated on the belief that technologies, indigenous or foreign, are appropriate so long as women concerned are given a voice in their countries' policy dialogue.

Formal Solutions for Polarized Radiative Transfer. I. The DELO Family

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

Janett, Gioele; Carlin, Edgar S.; Steiner, Oskar

The discussion regarding the numerical integration of the polarized radiative transfer equation is still open and the comparison between the different numerical schemes proposed by different authors in the past is not fully clear. Aiming at facilitating the comprehension of the advantages and drawbacks of the different formal solvers, this work presents a reference paradigm for their characterization based on the concepts of order of accuracy , stability , and computational cost . Special attention is paid to understand the numerical methods belonging to the Diagonal Element Lambda Operator family, in an attempt to highlight their specificities.

Ethics in the Legal and Business Practices of Radiation Oncology.

PubMed

Wall, Terry J

2017-10-01

Ethical issues arise when a professional endeavor such as medicine, which seeks to place the well-being of others over the self-interest of the practitioner, meets granular business and legal decisions involved in making a livelihood out of a professional calling. The use of restrictive covenants, involvement in self-referral patterns, and maintaining appropriate comity among physicians while engaged in the marketplace are common challenges in radiation oncology practice. A paradigm of analysis is presented to help navigate these management challenges. Copyright © 2017 Elsevier Inc. All rights reserved.

Imaging with terahertz radiation

NASA Astrophysics Data System (ADS)

Chan, Wai Lam; Deibel, Jason; Mittleman, Daniel M.

2007-08-01

Within the last several years, the field of terahertz science and technology has changed dramatically. Many new advances in the technology for generation, manipulation, and detection of terahertz radiation have revolutionized the field. Much of this interest has been inspired by the promise of valuable new applications for terahertz imaging and sensing. Among a long list of proposed uses, one finds compelling needs such as security screening and quality control, as well as whimsical notions such as counting the almonds in a bar of chocolate. This list has grown in parallel with the development of new technologies and new paradigms for imaging and sensing. Many of these proposed applications exploit the unique capabilities of terahertz radiation to penetrate common packaging materials and provide spectroscopic information about the materials within. Several of the techniques used for terahertz imaging have been borrowed from other, more well established fields such as x-ray computed tomography and synthetic aperture radar. Others have been developed exclusively for the terahertz field, and have no analogies in other portions of the spectrum. This review provides a comprehensive description of the various techniques which have been employed for terahertz image formation, as well as discussing numerous examples which illustrate the many exciting potential uses for these emerging technologies.

Particle acceleration magnetic field generation, and emission in Relativistic pair jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Kouveliotou, C.; Fishman, G. J.

2005-01-01

Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) are responsible for particle acceleration in relativistic pair jets. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic pair jet propagating through a pair plasma. Simulations show that the Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. Simulation results show that this instability generates and amplifies highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The "jitter' I radiation from deflected electrons can have different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. The growth rate of the Weibel instability and the resulting particle acceleration depend on the magnetic field strength and orientation, and on the initial particle distribution function. In this presentation we explore some of the dependencies of the Weibel instability and resulting particle acceleration on the magnetic field strength and orientation, and the particle distribution function.

Advancing Clinical Proteomics via Analysis Based on Biological Complexes: A Tale of Five Paradigms.

PubMed

Goh, Wilson Wen Bin; Wong, Limsoon

2016-09-02

Despite advances in proteomic technologies, idiosyncratic data issues, for example, incomplete coverage and inconsistency, resulting in large data holes, persist. Moreover, because of naïve reliance on statistical testing and its accompanying p values, differential protein signatures identified from such proteomics data have little diagnostic power. Thus, deploying conventional analytics on proteomics data is insufficient for identifying novel drug targets or precise yet sensitive biomarkers. Complex-based analysis is a new analytical approach that has potential to resolve these issues but requires formalization. We categorize complex-based analysis into five method classes or paradigms and propose an even-handed yet comprehensive evaluation rubric based on both simulated and real data. The first four paradigms are well represented in the literature. The fifth and newest paradigm, the network-paired (NP) paradigm, represented by a method called Extremely Small SubNET (ESSNET), dominates in precision-recall and reproducibility, maintains strong performance in small sample sizes, and sensitively detects low-abundance complexes. In contrast, the commonly used over-representation analysis (ORA) and direct-group (DG) test paradigms maintain good overall precision but have severe reproducibility issues. The other two paradigms considered here are the hit-rate and rank-based network analysis paradigms; both of these have good precision-recall and reproducibility, but they do not consider low-abundance complexes. Therefore, given its strong performance, NP/ESSNET may prove to be a useful approach for improving the analytical resolution of proteomics data. Additionally, given its stability, it may also be a powerful new approach toward functional enrichment tests, much like its ORA and DG counterparts.

Community College Faculty: Making the Paradigm Shift.

ERIC Educational Resources Information Center

Van Ast, John

1999-01-01

Discusses the need for paradigm shifts during the next decade that address the following challenges: (1) the wider range of student ability and mastery; (2) high attrition rates; and (3) differing and often contradicting perceptions of students, faculty, and administration. Contains 180 references. (TGO)

A New Paradigm of Primary Health Care in Kazakhstan

PubMed Central

Sharman, Almaz

2014-01-01

This paper discusses the need for change from Kazakhstan’s current disease-centric healthcare paradigm to a new primary health and wellness-centric health care paradigm, technology-driven and based on personal relationships within a social context. While many different papers have been published about the importance of prevention and primary health care, few have focused on healthcare transition in Kazakhstan or other countries in Central Asia. The WHO’s historic 1978 Alma-Ata Declaration signed in Kazakhstan promoted the centrality of primary care to the provision of effective, efficient, and equitable health services. Modern technologies such as the Internet, social media, and portable medical devices democratize medicine, providing great opportunities to rethink the Alma-Ata Declaration and reinvent primary health care on an entirely new platform that is knowledge-based and technology-assisted. The new paradigm suggested for the future development of health in Central Asian region emphasizes personal relationships and encourages sustainable solutions created by communities. This paper also introduces HealthCity, a new project in Kazakhstan aiming at introducing private, community-based and standardized primary healthcare that is driven by SmartHealth innovative technology. PMID:29755891

Narrative research on mental health recovery: two sister paradigms.

PubMed

Spector-Mersel, Gabriela; Knaifel, Evgeny

2017-06-24

Despite the breadth of narrative studies on individuals with severe mental illness, the suitability of narrative inquiry to exploring mental health recovery (MHR) has not been examined. (1) Examining the appropriateness of narrative inquiry to studying MHR; (2) assessing the extent to which narrative studies on MHR conform to the unique features of narrative research, as a distinctive form of qualitative inquiry. Review of empirical, theoretical and methodological literature on recovery and narrative inquiry. Considering the perspectives of recovery and narrative as paradigms, the similarity between their ontology and epistemology is shown, evident in 10 common emphases: meaning, identity, change and development, agency, holism, culture, uniqueness, context, language and giving voice. The resemblance between these "sister" paradigms makes narrative methodology especially fruitful for accessing the experiences of individuals in recovery. Reviewing narrative studies on MHR suggests that, currently, narrative research's uniqueness, centered on the holistic principle, is blurred on the philosophical, methodological and textual levels. Well-established narrative research has major implications for practice and policy in recovery-oriented mental health care. The narrative inquiry paradigm offers a possible path to enhancing the distinctive virtues of this research, realizing its potential in understanding and promoting MHR.

Legislation on ethical issues: towards an interactive paradigm.

PubMed

van der Berg, W; Brom, F W A

2000-03-01

In this article, we sketch a new approach to law and ethics. The traditional paradigm, exemplified in the debate on liberal moralism, becomes increasingly inadequate. Its basic assumptions are that there are clear moral norms of positive or critical morality, and that making statutory norms is an effective methods to have citizens conform to those norms. However, for many ethical issues that are on the legislative agenda, e.g. with respect to bioethics and anti-discrimination law, the moral norms are controversial, vague or still evolving. Moreover, law proves not to be a very effective instrument. Therefore, we need a new paradigm, both for descriptive and for normative analysis. This interactive paradigm, as a normative position, can be summarised in two theses. The process of legislation on ethical issues should be structured as a process of interaction between the legislature and society, or relevant sectors of society, so that the development of new moral norms and the development of new legal norms may reinforce each other. And legislation on ethical issues should be designed in such a way that it is an effective form of communication which, moreover, facilitates an ongoing moral debate and an ongoing reflection of such issues, because this is the best method to ensure that the practice remains oriented to the ideals and values the law tries to realise.

Validity and reliability of four language mapping paradigms.

PubMed

Wilson, Stephen M; Bautista, Alexa; Yen, Melodie; Lauderdale, Stefanie; Eriksson, Dana K

2017-01-01

Language areas of the brain can be mapped in individual participants with functional MRI. We investigated the validity and reliability of four language mapping paradigms that may be appropriate for individuals with acquired aphasia: sentence completion, picture naming, naturalistic comprehension, and narrative comprehension. Five neurologically normal older adults were scanned on each of the four paradigms on four separate occasions. Validity was assessed in terms of whether activation patterns reflected the known typical organization of language regions, that is, lateralization to the left hemisphere, and involvement of the left inferior frontal gyrus and the left middle and/or superior temporal gyri. Reliability (test-retest reproducibility) was quantified in terms of the Dice coefficient of similarity, which measures overlap of activations across time points. We explored the impact of different absolute and relative voxelwise thresholds, a range of cluster size cutoffs, and limitation of analyses to a priori potential language regions. We found that the narrative comprehension and sentence completion paradigms offered the best balance of validity and reliability. However, even with optimal combinations of analysis parameters, there were many scans on which known features of typical language organization were not demonstrated, and test-retest reproducibility was only moderate for realistic parameter choices. These limitations in terms of validity and reliability may constitute significant limitations for many clinical or research applications that depend on identifying language regions in individual participants.

Particle Acceleration and Magnetic Field Generation in Electron-Positron Relativistic Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P.; Richardson, G.; Preece, R.; Sol, H.; Fishman, G. J.

2004-01-01

of "jitter" radiation from deflected electrons (positrons) as opposed to synchrotron radiation. The jitter radiation has different properties than synchrotron radiation calculated assuming a a uniform magnetic field. The jitter radiation resulting from small scale magnetic field structures may be important for understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources containing relativistic jets and relativistic collisionless shocks.

Particle Acceleration and Magnetic Field Generation in Electron-Positron Relativistic Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, K.-L.; Hardee, P.; Richardson, G.; Preece, R.; Sol, H.; Fishman, G. J.

2004-01-01

is appropriate to the generation of jitter radiation from deflected electrons (positrons) as opposed to synchrotron radiation. The jitter radiation has different properties than synchrotron radiation calculated assuming a a uniform magnetic field. The jitter radiation resulting from small scale magnetic field structures may be important for understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources containing relativistic jets and relativistic collisionless shocks.

Particle Acceleration and Magnetic Field Generation in Electron-Positron Relativistic Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P.; Richardson, G.; Preece, R.; Sol, H.; Fishman, G. J.

2005-01-01

small- scale magnetic field structure is appropriate to the generation of "jitter" radiation from deflected electrons (positrons) as opposed to synchrotron radiation. The jitter radiation has different properties than synchrotron radiation calculated assuming a uniform magnetic field. The jitter radiation resulting from small-scale magnetic field structures may be important for understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources containing relativistic jets and relativistic collisionless shocks.

Discrete diffusion Lyman α radiative transfer

NASA Astrophysics Data System (ADS)

Smith, Aaron; Tsang, Benny T.-H.; Bromm, Volker; Milosavljević, Miloš

2018-06-01

Due to its accuracy and generality, Monte Carlo radiative transfer (MCRT) has emerged as the prevalent method for Lyα radiative transfer in arbitrary geometries. The standard MCRT encounters a significant efficiency barrier in the high optical depth, diffusion regime. Multiple acceleration schemes have been developed to improve the efficiency of MCRT but the noise from photon packet discretization remains a challenge. The discrete diffusion Monte Carlo (DDMC) scheme has been successfully applied in state-of-the-art radiation hydrodynamics (RHD) simulations. Still, the established framework is not optimal for resonant line transfer. Inspired by the DDMC paradigm, we present a novel extension to resonant DDMC (rDDMC) in which diffusion in space and frequency are treated on equal footing. We explore the robustness of our new method and demonstrate a level of performance that justifies incorporating the method into existing Lyα codes. We present computational speedups of ˜102-106 relative to contemporary MCRT implementations with schemes that skip scattering in the core of the line profile. This is because the rDDMC runtime scales with the spatial and frequency resolution rather than the number of scatterings—the latter is typically ∝τ0 for static media, or ∝(aτ0)2/3 with core-skipping. We anticipate new frontiers in which on-the-fly Lyα radiative transfer calculations are feasible in 3D RHD. More generally, rDDMC is transferable to any computationally demanding problem amenable to a Fokker-Planck approximation of frequency redistribution.

Cost per quality-adjusted life year and disability-adjusted life years: the need for a new paradigm.

PubMed

Bevan, Gwyn; Hollinghurst, Sandra

2003-08-01

Two different paradigms have been proposed for setting priorities for access to healthcare: cost per quality-adjusted life year based on interventions, and disability-adjusted life years based on the burden of disease in a population. These formal paradigms make explicit the assumptions made implicitly every day in delivering and hence rationing access to healthcare. This paper outlines each paradigm's methodological problems and argues that each paradigm is incomplete in terms of providing the information necessary for making budgetary decisions on healthcare. It argues that a scientific revolution is required to create a new paradigm by combining the strengths of each.

Kappa and Rater Accuracy: Paradigms and Parameters

ERIC Educational Resources Information Center

Conger, Anthony J.

2017-01-01

Drawing parallels to classical test theory, this article clarifies the difference between rater accuracy and reliability and demonstrates how category marginal frequencies affect rater agreement and Cohen's kappa. Category assignment paradigms are developed: comparing raters to a standard (index) versus comparing two raters to one another…

A Novel Navigation Paradigm for XML Repositories.

ERIC Educational Resources Information Center

Azagury, Alain; Factor, Michael E.; Maarek, Yoelle S.; Mandler, Benny

2002-01-01

Discusses data exchange over the Internet and describes the architecture and implementation of an XML document repository that promotes a navigation paradigm for XML documents based on content and context. Topics include information retrieval and semistructured documents; and file systems as information storage infrastructure, particularly XMLFS.…

Converging technologies in higher education: paradigm for the "new" liberal arts?

PubMed

Balmer, Robert T

2006-12-01

This article discusses the historic relationship between the practical arts (technology) and the mental (liberal) arts, suggesting that Converging Technologies is a new higher education paradigm that integrates the arts, humanities, and sciences with modern technology. It explains that the paradigm really includes all fields in higher education from philosophy to art to music to modern languages and beyond. To implement a transformation of this magnitude, it is necessary to understand the psychology of change in academia. Union College in Schenectady, New York, implemented a Converging Technologies Educational Paradigm in five steps: (1) create a compelling vision, (2) communicate the vision, (3) empower the faculty, (4) create short-term successes, and (5) institutionalize the results. This case study of Union College demonstrates it is possible to build a pillar of educational excellence based on Converging Technologies.

The single lineup paradigm: A new way to manipulate target presence in eyewitness identification experiments.

PubMed

Oriet, Chris; Fitzgerald, Ryan J

2018-02-01

The suspect in eyewitness lineups may be guilty or innocent. These possibilities are traditionally simulated in eyewitness identification studies using a dual-lineup paradigm: All witnesses observe the same perpetrator and then receive one of two lineups. In this paradigm, the suspect's guilt is manipulated by including the perpetrator in one lineup and an innocent suspect in the other. The lineup is then filled with people matched to either the suspect (resulting in different fillers in perpetrator-present and perpetrator-absent lineups) or to the perpetrator (resulting in the same fillers in each lineup). An inescapable feature of the dual-lineup paradigm is that the perpetrator-present and perpetrator-absent lineups differ not only in the suspect's guilt, but also in their composition. Here, we describe a single-lineup paradigm: Subjects observe one of two perpetrators and then all subjects receive the same lineup containing one of the perpetrators. This alternative paradigm allows manipulation of the suspect's guilt without changing the lineup's composition. In three experiments, we applied the single-lineup paradigm to explore suspect-filler similarity and consistently found that increasing similarity reduced perpetrator identifications but did little to prevent innocent suspect misidentifications. Conversely, when fillers were matched to the perpetrator using a dual-lineup paradigm, increasing similarity reduced identification of perpetrators and innocent suspects. This finding suggests that the effect of filler similarity may depend on the person to whom the fillers are matched. We suggest that the single-lineup paradigm is a more ecologically valid and better controlled approach to creating suspect-matched lineups in laboratory investigations of eyewitness memory than existing procedures. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Co-"Lab"oration: A New Paradigm for Building a Management Information Systems Course

ERIC Educational Resources Information Center

Breimer, Eric; Cotler, Jami; Yoder, Robert

2010-01-01

We propose a new paradigm for building a Management Information Systems course that focuses on laboratory activities developed collaboratively using Computer-Mediated Communication and Collaboration tools. A highlight of our paradigm is the "practice what you preach" concept where the computer communication tools and collaboration…

A Self-Control Versus a Counterconditioning Paradigm for Systematic Desensitization: An Experimental Comparison

ERIC Educational Resources Information Center

Spiegler, Michael D.; And Others

1976-01-01

A comparison was made between the traditional counterconditioning paradigm and a self-control paradigm of systematic desensitization. College students reporting high test anxiety and indicating interest in receiving treatment were assigned to counterconditioning, self-control, or wait-list control conditions. As predicted, self-control procedures…

Treating Patients Who Strain the Research Psychotherapy Paradigm

PubMed Central

Markowitz, John C.; Kaplowitz, Matthew; Suh, Eun-Jung; Meehan, Kevin; Neria, Yuval; Jonker, Hanske; Rafaeli, Alexandra; Lovell, Karina

2013-01-01

Background Clinical trials of psychotherapy require diagnostic homogeneity, which implies a convergence of clinical presentations. Yet research study patients present diversely, and patients who do not fit a treatment paradigm may greatly complicate delivery of the study psychotherapy. The research literature has not addressed this issue. Methods The authors use case illustrations of three psychotherapies – Prolonged Exposure, Relaxation Therapy, and Interpersonal Psychotherapy – from an ongoing psychotherapy outcome trial of posttraumatic stress disorder to describe psychotherapeutic responses to complex, “atypical” patients who strain standard treatment paradigms. Results Therapists required flexibility, and occasionally deviations from strict protocol, in treating heterodox patients. Conclusions Such heterogeneity of presentation may have implications for psychotherapy outcome in research trials. Despite lack of discussion in the literature, many trials may face such issues. PMID:22759936

Multimission Software Reuse in an Environment of Large Paradigm Shifts

NASA Technical Reports Server (NTRS)

Wilson, Robert K.

1996-01-01

The ground data systems provided for NASA space mission support are discussed. As space missions expand, the ground systems requirements become more complex. Current ground data systems provide for telemetry, command, and uplink and downlink processing capabilities. The new millennium project (NMP) technology testbed for 21st century NASA missions is discussed. The program demonstrates spacecraft and ground system technologies. The paradigm shift from detailed ground sequencing to a goal oriented planning approach is considered. The work carried out to meet this paradigm for the Deep Space-1 (DS-1) mission is outlined.

Membrane paradigm of black holes in Chern-Simons modified gravity

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

Zhao, Tian-Yi; Wang, Towe, E-mail: zhaotianyi5566@foxmail.com, E-mail: twang@phy.ecnu.edu.cn

2016-06-01

The membrane paradigm of black hole is studied in the Chern-Simons modified gravity. Derived with the action principle a la Parikh-Wilczek, the stress tensor of membrane manifests a rich structure arising from the Chern-Simons term. The membrane stress tensor, if related to the bulk stress tensor in a special form, obeys the low-dimensional fluid continuity equation and the Navier-Stokes equation. This paradigm is applied to spherically symmetric static geometries, and in particular, the Schwarzschild black hole, which is a solution of a large class of dynamical Chern-Simons gravity.

Fluctuations with small numbers: Developing the perturbative paradigm for jet physics in the QGP at RHIC and LHC

NASA Astrophysics Data System (ADS)

Wicks, Simon

Many novel results have emerged from the experimental heavy ion program at the Relativistic Heavy Ion Collider. For some, these necessitate a new paradigm, a jump into the extra dimension of strongly coupled physics and AdS/CFT. This thesis takes the opposite view. Asymptotic weakly coupled arguments are of course inapplicable. Purely parametric relations are not sufficient as the temperatures are not hot enough, the jet energies not high enough, the lengths not long enough. However, perturbative techniques provide a strong foundation on which to build our explanations of data from RHIC and the upcoming LHC. This thesis presents the first detailed study of both collisional and radiative energy losses, applied to both light and heavy partonic jets at RHIC and LHC. The primary motivation is the heavy quark puzzle, observed through the surprisingly strong quenching of high momentum single non-photonic electrons at RHIC. Collisional energy loss is likely a non-negligible component of the energy loss of jets. It also provides a calculation in which to examine our assumptions about jet-medium interactions. For the quantities of interest, the soft interactions o, q << T are not dominant; the rarer, moderately hard collisions are more important. This impacts the choice of one collision calculation---a simple, first term in a hard thermal loop calculation does not include the necessary medium recoil kinematics---and of the multiple collision convolution---a simple, drag-diffusion scheme is insufficient for the short lengths of interest. This also motivates an opacity expansion evaluation of the radiative energy loss. This expansion is equivalent to Schrodinger-like equations used in some radiative models, and provides a suitable method of numerical solution to that equation. Presented here is a Monte Carlo numerical integration that can give results to ninth order in opacity and beyond. The results confirm that, for the lengths of interest at RHIC and LHC, the first order

Functional transcranial Doppler sonography and a spatial orientation paradigm identify the non-dominant hemisphere.

PubMed

Dorst, J; Haag, A; Knake, S; Oertel, W H; Hamer, H M; Rosenow, F

2008-10-01

Functional transcranial Doppler sonography (fTCD) during word generation is well established for language lateralization. In this study, we evaluated a fTCD paradigm to reliably identify the non-dominant hemisphere. Twenty-nine right-handed healthy subjects (27.1+/-7.6 years) performed the 'cube perspective test' [Stumpf, H., & Fay, E. (1983). Schlauchfiguren: Ein Test zur Beurteilung des räumlichen Vorstellungsvermögens. Verlag für Psychologie Dr. C. J. Hogrefe, Göttingen, Toronto, Zürich] a spatial orientation task, while the cerebral blood flow velocity (CBFV) was simultaneously measured in both middle cerebral arteries (MCAs). In addition, the established word generation paradigm for language lateralization was performed. Subjects with atypical language representation were excluded. Data were analysed offline with the software Average, which performed a heart-cycle integration and a baseline-correction and calculated a lateralization index (LI) with its standard error of the mean increase in CBFV separately for both MCAs. Twenty-one of 29 subjects (72.4%) lateralized to the right hemisphere (chi2=5.828, p=0.016). The mean LI of the spatial orientation paradigm pointed to the right hemisphere (x =-1.9+/-3.2) and was different from the LI of word generation (x =3.9+/-2.2;p<0.001). There was no correlation between the LI of spatial orientation and word generation (R=0.095, p=0.624). Age of the subjects did not correlate with the LI during spatial orientation (p>0.05) but negatively with the LI during word generation (R=-0.468, p=0.010). The maximum increase of CBFV was greater in the spatial orientation (14.0%+/-3.6%) than in the word generation paradigm (9.4%+/-4.0%; p<0.001). In more than two thirds of the subjects with left-sided language dominance, the spatial orientation paradigm was able to identify the non-dominant hemisphere. The results suggest both paradigms to be independent of each other. The spatial orientation paradigm, therefore, appears to be

A Paradigm for Student Learning Outcome Assessment in Information Systems Education: Continuous Improvement or Chasing Rainbows?

ERIC Educational Resources Information Center

Saulnier, Bruce

2014-01-01

A paradigm is presented for student learning outcome assessment in information systems education. Successful deployment of the paradigm is illustrated using the author's home institution. The paradigm is consistent with both the scholarship of teaching and learning and the scholarship of assessment. It is concluded that the deployment of the…

Colloidal paradigm in supercapattery electrode systems

NASA Astrophysics Data System (ADS)

Chen, Kunfeng; Xue, Dongfeng

2018-01-01

Among decades of development, electrochemical energy storage systems are now sorely in need of a new design paradigm at the nano size and ion level to satisfy the higher energy and power demands. In this review paper, we introduce a new colloidal electrode paradigm for supercapattery that integrates multiple-scale forms of matter, i.e. ion clusters, colloidal ions, and nanosized materials, into one colloid system, coupled with multiple interactions, i.e. electrostatic, van der Waals forces, and chemical bonding, thus leading to the formation of many redox reactive centers. This colloidal electrode not only keeps the original ionic nature in colloidal materials, but also creates a new attribute of high electroactivity. Colloidal supercapattery is a perfect application example of the novel colloidal electrode, leading to higher specific capacitance than traditional electrode materials. The high electroactivity of the colloidal electrode mainly comes from the contribution of exposed reactive centers, owing to the confinement effect of carbon and a binder matrix. Systematic and thorough research on the colloidal system will significantly promote the development of fundamental science and the progress of advanced energy storage technology.

Answer Set Programming and Other Computing Paradigms

ERIC Educational Resources Information Center

Meng, Yunsong

2013-01-01

Answer Set Programming (ASP) is one of the most prominent and successful knowledge representation paradigms. The success of ASP is due to its expressive non-monotonic modeling language and its efficient computational methods originating from building propositional satisfiability solvers. The wide adoption of ASP has motivated several extensions to…

Impression-Management in the Forced Compliance Paradigm.

ERIC Educational Resources Information Center

Saenz, Rogelio; Quigley-Fernandez, Barbara

In its original formulation, dissonance reduction was postulated as a mode for resolving behavior-attitude discrepancies. One mode of resolution has been demonstrated in the forced compliance paradigm, whereby a subject rectifies a counterattitudinal behavior with an actual belief, resulting in moderating beliefs. A forced compliance situation was…

Has the Education Paradigm Begun to Shift?

ERIC Educational Resources Information Center

Chadwick, Clifton B.

2014-01-01

The author reviews various elements of what may be considered as evidence that the long-awaited shift in the education paradigm is actually happening. Concepts like student-centered learning, attainment-based evaluation, knowledge-based constructivism, and effort-based intelligence are growing, are being more widely recognized as important, and…

Reinforcing the Afrocentric Paradigm: A Theoretical Project

ERIC Educational Resources Information Center

Sams, Timothy E.

2010-01-01

Thomas Kuhn's 1962 groundbreaking work, "The Scientific Revolution," established the process for creating, and the components of, a disciplinary paradigm. This "scientific revolution" has evolved to become the standard for determining a field's claim to disciplinary status. In 2001 and 2003, Ama Mazama, used Kuhn's model to establish the…

A new paradigm for clinical communication: critical review of literature in cancer care.

PubMed

Salmon, Peter; Young, Bridget

2017-03-01

To: (i) identify key assumptions of the scientific 'paradigm' that shapes clinical communication research and education in cancer care; (ii) show that, as general rules, these do not match patients' own priorities for communication; and (iii) suggest how the paradigm might change to reflect evidence better and thereby serve patients better. A critical review, focusing on cancer care. We identified assumptions about patients' and clinicians' roles in recent position and policy statements. We examined these in light of research evidence, focusing on inductive research that has not itself been constrained by those assumptions, and considering the institutionalised interests that the assumptions might serve. The current paradigm constructs patients simultaneously as needy (requiring clinicians' explicit emotional support) and robust (seeking information and autonomy in decision making). Evidence indicates, however, that patients generally value clinicians who emphasise expert clinical care rather than counselling, and who lead decision making. In denoting communication as a technical skill, the paradigm constructs clinicians as technicians; however, communication cannot be reduced to technical skills, and teaching clinicians 'communication skills' has not clearly benefited patients. The current paradigm is therefore defined by assumptions that that have not arisen from evidence. A paradigm for clinical communication that makes its starting point the roles that mortal illness gives patients and clinicians would emphasise patients' vulnerability and clinicians' goal-directed expertise. Attachment theory provides a knowledge base to inform both research and education. Researchers will need to be alert to political interests that seek to mould patients into 'consumers', and to professional interests that seek to add explicit psychological dimensions to clinicians' roles. New approaches to education will be needed to support clinicians' curiosity and goal-directed judgement

Verification of the Solar Dynamics Observatory High Gain Antenna Pointing Algorithm Using Flight Data

NASA Technical Reports Server (NTRS)

Bourkland, Kristin L.; Liu, Kuo-Chia

2011-01-01

The Solar Dynamics Observatory (SDO), launched in 2010, is a NASA-designed spacecraft built to study the Sun. SDO has tight pointing requirements and instruments that are sensitive to spacecraft jitter. Two High Gain Antennas (HGAs) are used to continuously send science data to a dedicated ground station. Preflight analysis showed that jitter resulting from motion of the HGAs was a cause for concern. Three jitter mitigation techniques were developed and implemented to overcome effects of jitter from different sources. These mitigation techniques include: the random step delay, stagger stepping, and the No Step Request (NSR). During the commissioning phase of the mission, a jitter test was performed onboard the spacecraft, in which various sources of jitter were examined to determine their level of effect on the instruments. During the HGA portion of the test, the jitter amplitudes from the single step of a gimbal were examined, as well as the amplitudes due to the execution of various gimbal rates. The jitter levels were compared with the gimbal jitter allocations for each instrument. The decision was made to consider implementing two of the jitter mitigating techniques on board the spacecraft: stagger stepping and the NSR. Flight data with and without jitter mitigation enabled was examined, and it is shown in this paper that HGA tracking is not negatively impacted with the addition of the jitter mitigation techniques. Additionally, the individual gimbal steps were examined, and it was confirmed that the stagger stepping and NSRs worked as designed. An Image Quality Test was performed to determine the amount of cumulative jitter from the reaction wheels, HGAs, and instruments during various combinations of typical operations. The HGA-induced jitter on the instruments is well within the jitter requirement when the stagger step and NSR mitigation options are enabled.

The Problem with Paradigms: Bateman's Worldview as a Case Study.

PubMed

Tang-Martinez, Zuleyma; Ryder, T Brandt

2005-11-01

Bateman's principles, their corollaries and predictions constitute a paradigm for the study of sexual selection theory, evolution of mating systems, parental investment theory, and sexual dimorphism in male and female behavior. Some aspects of this paradigm have been challenged in recent years, while others have been supported by empirical and theoretical research. We re-examine Bateman's 1948 paper in detail, including some methodological problems. Additionally, we review three areas in which an over-reliance on Bateman's predictions about sexual dynamics hindered our ability to understand the potential importance of certain behaviors: 1) male mate choice and sperm allocation; 2) the role of females in initiating and soliciting extra-pair copulations and fertilizations; and 3) the role of females in lekking systems, in which recent evidence suggests that copulations with multiple males (polyandrous behavior) may be common. We conclude this introduction to the symposium by emphasizing the heuristic value of Bateman's contributions, as well as the problems that arise when Bateman's paradigm is viewed through the lens of modern behavioral ecology and evolutionary theory.

Common Ground of Two Paradigms: Incorporating Critical Theory into Current Art Therapy Practices

ERIC Educational Resources Information Center

Nolan, Emily

2013-01-01

Clinical art therapy and studio-based community art therapy represent two major paradigms in art therapy practice. This viewpoint explores how critical theory can be incorporated into both paradigms and result in common ground between them. Critical theory encompasses an understanding of oppression in psychological, social, and cultural contexts…

Rapid Loss of Radiation Belt Relativistic Electrons by EMIC Waves

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

Su, Zhenpeng; Gao, Zhonglei; Zheng, Huinan

How relativistic electrons are lost is an important question surrounding the complex dynamics of the Earth's outer radiation belt. Radial loss to the magnetopause and local loss to the atmosphere are two main competing paradigms. Here on the basis of the analysis of a radiation belt storm event on 27 February 2014, we present new evidence for the electromagnetic ion cyclotron (EMIC) wave-driven local precipitation loss of relativistic electrons in the heart of the outer radiation belt. During the main phase of this storm, the radial profile of relativistic electron phase space density was quasi-monotonic, qualitatively inconsistent with the predictionmore » of radial loss theory. The local loss at low L shells was required to prevent the development of phase space density peak resulting from the radial loss process at high L shells. The rapid loss of relativistic electrons in the heart of outer radiation belt was observed as a dip structure of the electron flux temporal profile closely related to intense EMIC waves. Our simulations further confirm that the observed EMIC waves within a quite limited longitudinal region were able to reduce the off-equatorially mirroring relativistic electron fluxes by up to 2 orders of magnitude within about 1.5 h.« less

Rapid Loss of Radiation Belt Relativistic Electrons by EMIC Waves

DOE PAGES

Su, Zhenpeng; Gao, Zhonglei; Zheng, Huinan; ...

2017-08-31

How relativistic electrons are lost is an important question surrounding the complex dynamics of the Earth's outer radiation belt. Radial loss to the magnetopause and local loss to the atmosphere are two main competing paradigms. Here on the basis of the analysis of a radiation belt storm event on 27 February 2014, we present new evidence for the electromagnetic ion cyclotron (EMIC) wave-driven local precipitation loss of relativistic electrons in the heart of the outer radiation belt. During the main phase of this storm, the radial profile of relativistic electron phase space density was quasi-monotonic, qualitatively inconsistent with the predictionmore » of radial loss theory. The local loss at low L shells was required to prevent the development of phase space density peak resulting from the radial loss process at high L shells. The rapid loss of relativistic electrons in the heart of outer radiation belt was observed as a dip structure of the electron flux temporal profile closely related to intense EMIC waves. Our simulations further confirm that the observed EMIC waves within a quite limited longitudinal region were able to reduce the off-equatorially mirroring relativistic electron fluxes by up to 2 orders of magnitude within about 1.5 h.« less