WorldWideScience

Sample records for surface-atmosphere feedback mechanism

  1. Updating representation of land surface-atmosphere feedbacks in airborne campaign modeling analysis

    Science.gov (United States)

    Huang, M.; Carmichael, G. R.; Crawford, J. H.; Chan, S.; Xu, X.; Fisher, J. A.

    2017-12-01

    An updated modeling system to support airborne field campaigns is being built at NASA Ames Pleiades, with focus on adjusting the representation of land surface-atmosphere feedbacks. The main updates, referring to previous experiences with ARCTAS-CARB and CalNex in the western US to study air pollution inflows, include: 1) migrating the WRF (Weather Research and Forecasting) coupled land surface model from Noah to improved/more complex models especially Noah-MP and Rapid Update Cycle; 2) enabling the WRF land initialization with suitably spun-up land model output; 3) incorporating satellite land cover, vegetation dynamics, and soil moisture data (i.e., assimilating Soil Moisture Active Passive data using the ensemble Kalman filter approach) into WRF. Examples are given of comparing the model fields with available aircraft observations during spring-summer 2016 field campaigns taken place at the eastern side of continents (KORUS-AQ in South Korea and ACT-America in the eastern US), the air pollution export regions. Under fair weather and stormy conditions, air pollution vertical distributions and column amounts, as well as the impact from land surface, are compared. These help identify challenges and opportunities for LEO/GEO satellite remote sensing and modeling of air quality in the northern hemisphere. Finally, we briefly show applications of this system on simulating Australian conditions, which would explore the needs for further development of the observing system in the southern hemisphere and inform the Clean Air and Urban Landscapes (https://www.nespurban.edu.au) modelers.

  2. Assessing the influence of groundwater and land surface scheme in the modelling of land surface-atmosphere feedbacks over the FIFE area in Kansas, USA

    DEFF Research Database (Denmark)

    Larsen, Morten Andreas Dahl; Højmark Rasmussen, Søren; Drews, Martin

    2016-01-01

    by HIRHAM simulated precipitation. The last two simulations include iv) a standard HIRHAM simulation, and v) a fully coupled HIRHAM-MIKE SHE simulation locally replacing the land surface scheme by MIKE SHE for the FIFE area, while HIRHAM in standard configuration is used for the remaining model area......The land surface-atmosphere interaction is described differently in large scale surface schemes of regional climate models and small scale spatially distributed hydrological models. In particular, the hydrological models include the influence of shallow groundwater on evapotranspiration during dry...... experiments include five simulations. First MIKE SHE is forced by observed climate data in two versions i) with groundwater at a fixed uniform depth, and ii) with a dynamical groundwater component simulating shallow groundwater conditions in river valleys. iii) In a third simulation MIKE SHE is forced...

  3. Dynamic aspects of the tubuloglomerular feedback mechanism

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H

    1992-01-01

    the thick ascending limb of the loop of Henle (TAL) and the vascular pole of the glomerulus. The JGA includes the macula densa, a specialized plaque of cells in the TAL thought to be responsible for the sensing step in the feedback mechanism; the mesangial cells, a cushion of cells separating the macula...... densa from the vascular pole of the glomerulus; and the afferent arteriole, the main effector site for the TGF. An increase in the NaCl concentration at the macula densa elicits a response in the smooth muscle cells of the afferent arteriole increasing the hemodynamic resistance of the preglomerular...... vasculature. These changes will, through decreases in the GFR and the tubular flow rate, cause a decrease in the NaCl concentration at the macula densa. Thus, the system acts to stabilize the NaCl concentration at the macula densa. The purpose of the present study was to describe the dynamic characteristics...

  4. Social networks - an innovative feedback mechanism in management

    OpenAIRE

    Granchak, Tetiana

    2014-01-01

    In theses analyzes approaches to the use of social networking tools in the management; highlights the mechanisms ofMonitoring of social media information as a tool for feedback control system; possibility of personal accounts in social networks as a platform for feedback in management;reveals opportunities of social media as a tool for management of network type.

  5. Does Mechanism Matter? Student Recall of Electronic versus Handwritten Feedback

    Science.gov (United States)

    Osterbur, Megan E.; Hammer, Elizabeth Yost; Hammer, Elliott

    2015-01-01

    Student consumption and recall of feedback are necessary preconditions of successful formative assessment. Drawing on Sadler's (1998) definition of formative assessment as that which is intended to accelerate learning and improve performance through the providing of feedback, we examine how the mechanism of transmission may impact student…

  6. 78 FR 13057 - Agency Information Collection Activities; Information Collection; IT Dashboard Feedback Mechanism

    Science.gov (United States)

    2013-02-26

    ... Information Collection Activities; Information Collection; IT Dashboard Feedback Mechanism AGENCY: Office of... previously approved information collection requirement regarding IT Dashboard Feedback Mechanism. DATES... Collection 3090- 0285, IT Dashboard Feedback Mechanism, by any of the following methods: Regulations.gov...

  7. Feedback mechanism for smart nozzles and nebulizers

    Science.gov (United States)

    Montaser, Akbar [Potomac, MD; Jorabchi, Kaveh [Arlington, VA; Kahen, Kaveh [Kleinburg, CA

    2009-01-27

    Nozzles and nebulizers able to produce aerosol with optimum and reproducible quality based on feedback information obtained using laser imaging techniques. Two laser-based imaging techniques based on particle image velocimetry (PTV) and optical patternation map and contrast size and velocity distributions for indirect and direct pneumatic nebulizations in plasma spectrometry. Two pulses from thin laser sheet with known time difference illuminate droplets flow field. Charge coupled device (CCL)) captures scattering of laser light from droplets, providing two instantaneous particle images. Pointwise cross-correlation of corresponding images yields two-dimensional velocity map of aerosol velocity field. For droplet size distribution studies, solution is doped with fluorescent dye and both laser induced florescence (LIF) and Mie scattering images are captured simultaneously by two CCDs with the same field of view. Ratio of LIF/Mie images provides relative droplet size information, then scaled by point calibration method via phase Doppler particle analyzer.

  8. Short structured feedback training is equivalent to a mechanical feedback device in two-rescuer BLS: a randomised simulation study.

    Science.gov (United States)

    Pavo, Noemi; Goliasch, Georg; Nierscher, Franz Josef; Stumpf, Dominik; Haugk, Moritz; Breckwoldt, Jan; Ruetzler, Kurt; Greif, Robert; Fischer, Henrik

    2016-05-13

    Resuscitation guidelines encourage the use of cardiopulmonary resuscitation (CPR) feedback devices implying better outcomes after sudden cardiac arrest. Whether effective continuous feedback could also be given verbally by a second rescuer ("human feedback") has not been investigated yet. We, therefore, compared the effect of human feedback to a CPR feedback device. In an open, prospective, randomised, controlled trial, we compared CPR performance of three groups of medical students in a two-rescuer scenario. Group "sCPR" was taught standard BLS without continuous feedback, serving as control. Group "mfCPR" was taught BLS with mechanical audio-visual feedback (HeartStart MRx with Q-CPR-Technology™). Group "hfCPR" was taught standard BLS with human feedback. Afterwards, 326 medical students performed two-rescuer BLS on a manikin for 8 min. CPR quality parameters, such as "effective compression ratio" (ECR: compressions with correct hand position, depth and complete decompression multiplied by flow-time fraction), and other compression, ventilation and time-related parameters were assessed for all groups. ECR was comparable between the hfCPR and the mfCPR group (0.33 vs. 0.35, p = 0.435). The hfCPR group needed less time until starting chest compressions (2 vs. 8 s, p feedback or by using a mechanical audio-visual feedback device was similar. Further studies should investigate whether extended human feedback training could further increase CPR quality at comparable costs for training.

  9. The impact of feedback mechanisms on galaxy formation

    Science.gov (United States)

    Robertson, Brant Edward

    Feedback mechanisms regulate the dissipative processes that form the baryonic structures of galaxies. I examine the importance of energetic feedback from supernovae and accreting supermassive black holes for the formation of galaxies in the context of the hierarchical Λ-Cold Dark Matter (ΛCDM) cosmology. The formation of spiral galaxies in our hierarchical cosmology is innately tenuous as thin disks are structurally fragile and prone to dynamical instabilities. I demonstrate how supernovae feedback impacts disk galaxy formation by generating a multiphase interstellar medium (ISM). The hot, diffuse phase of the ISM sustained by supernovae acts to pressurize the effective ISM equation of state, stabilizes disks during their assembly, and regulates star formation by controlling the gas density. I demonstrate how these baryonic feedback processes allow for disk formation in cosmological environments and forward a new, merger-driven scenario for cosmological disk galaxy formation where the physics of the multiphase ISM and hierarchical structure formation can collaborate to form disks through early, gas-dominated mergers. If the ΛCDM cosmology is the correct model for our universe, our own Milky Way galaxy must have assembled hierarchically from smaller systems. I demonstrate how supernovae feedback sets the chemical abundance pattern of dwarf galaxies that disrupt to form the Milky Way stellar halo. The characteristic formation epoch and progenitor mass of the Galactic halo and supernovae feedback are shown to account for differences between the abundance pattern of metal-poor halo stars and surviving Milky Way satellite galaxies . The formation of elliptical galaxies by mergers of spiral galaxies has been posited for decades as a natural outcome of hierarchical structure formation. Using hundreds of simulations of disk galaxy mergers I demonstrate the importance of dissipative physical processes in the formation of realistic elliptical galaxies in mergers

  10. Learning from feedback: the neural mechanisms of feedback processing facilitating better performance.

    Science.gov (United States)

    Luft, Caroline Di Bernardi

    2014-03-15

    Different levels of feedback, from sensory signals to verbal advice, are needed not only for learning new skills, but also for monitoring performance. A great deal of research has focused on the electrophysiological correlates of feedback processing and how they relate to good learning. In this paper, studies on the EEG correlates of learning from feedback are reviewed. The main objective is to discuss these findings whilst also considering some key theoretical aspects of learning. The learning processes, its operational definition and the feedback characteristics are discussed and used as reference for integrating the findings in the literature. The EEG correlates of feedback processing for learning using various analytical approaches are discussed, including ERPs, oscillations and inter-site synchronization. How these EEG responses to feedback are related to learning is discussed, highlighting the gaps in the literature and suggesting future directions for understanding the neural underpinnings of learning from feedback. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Distributed force feedback in the spinal cord and the regulation of limb mechanics.

    Science.gov (United States)

    Nichols, T Richard

    2018-03-01

    This review is an update on the role of force feedback from Golgi tendon organs in the regulation of limb mechanics during voluntary movement. Current ideas about the role of force feedback are based on modular circuits linking idealized systems of agonists, synergists, and antagonistic muscles. In contrast, force feedback is widely distributed across the muscles of a limb and cannot be understood based on these circuit motifs. Similarly, muscle architecture cannot be understood in terms of idealized systems, since muscles cross multiple joints and axes of rotation and further influence remote joints through inertial coupling. It is hypothesized that distributed force feedback better represents the complex mechanical interactions of muscles, including the stresses in the musculoskeletal network born by muscle articulations, myofascial force transmission, and inertial coupling. Together with the strains of muscle fascicles measured by length feedback from muscle spindle receptors, this integrated proprioceptive feedback represents the mechanical state of the musculoskeletal system. Within the spinal cord, force feedback has excitatory and inhibitory components that coexist in various combinations based on motor task and integrated with length feedback at the premotoneuronal and motoneuronal levels. It is concluded that, in agreement with other investigators, autogenic, excitatory force feedback contributes to propulsion and weight support. It is further concluded that coexistent inhibitory force feedback, together with length feedback, functions to manage interjoint coordination and the mechanical properties of the limb in the face of destabilizing inertial forces and positive force feedback, as required by the accelerations and changing directions of both predator and prey.

  12. 78 FR 36190 - Agency Information Collection Activities; Submission for OMB Review; IT Dashboard Feedback Mechanism

    Science.gov (United States)

    2013-06-17

    ... Information Collection Activities; Submission for OMB Review; IT Dashboard Feedback Mechanism AGENCY: Office... to review and approve a previously approved information collection requirement regarding IT Dashboard... identified by Information Collection 3090- 0285, IT Dashboard Feedback Mechanism, by any of the following...

  13. Exploring A Thermal-Orbital Feedback Mechanism At Europa

    Science.gov (United States)

    Walker, Matthew; Mitchell, Jonathan L.; Bills, Bruce

    2016-10-01

    We present a geophysical model of the Europa system to describe it's structural, orbital, and thermal states. In doing so, we examine the potential for feedback mechanisms to occur which can produce oscillatory behavior in shell thickness, eccentricity, and heat flux, due to the coupled nature of the relevant processes. We implement a tidal heating model to describe the heat flux into the body. This model depends primarily on the shell structure as well as the orbital eccentricity. The model has the capacity to consider multilayered bodies for which the interior structure can evolve over time. Furthermore, the tidal heating model is fully three dimensionally resolved, having the ability to predict radial and lateral variations in heating throughout Europa. This allows us to predict particular locations on Europa that should have the maximum surface heat flux. This heating model is coupled to the orbital evolution as well. Tidal dissipation pulls energy out of the orbit, effectively reducing the semi-major axis and eccentricity, circularizing the orbit. This would slow, and even shut down, the tidal heating at Europa, however, the Galilean Satellites' Laplace resonance continuously transfers energy back into Europa's orbit, keeping the tidal dissipation active. We compare the tidal heat input to the heat conducted out of the ice shell, which is a function of shell thickness, among other things. Heat transfer into or out of the ice compensates any imbalance of heat. This heating, in turn, leads to structural variations of the shell. For example, if tidal heating is greater than the heat conducted out of the shell, the remaining balance goes into sensible and latent heats which thin the shell (thus increasing the surface heat output to balance that which is tidally input). Oppositely, when conducted heat output is greater than the tidal heating, the shell thickens. Shell thickness variations then result in global extension or contraction, due to the density difference

  14. effective feedback mechanism in the transfer and adoption of fish ...

    African Journals Online (AJOL)

    ABSTRACT. The study was aimed at identifying effective feedback processes from fish farmers to fish research institute, fish farmers to extension and extension to fish research institute in the transfer and adoption of fish technologies in South East Geo-political zone of Nigeria. Two states in the zone (Abia and Imo) which ...

  15. Kinetics of Inhibitory Feedback from Horizontal Cells to Photoreceptors: Implications for an Ephaptic Mechanism

    Science.gov (United States)

    Warren, Ted J.; Van Hook, Matthew J.; Tranchina, Daniel

    2016-01-01

    Inhibitory feedback from horizontal cells (HCs) to cones generates center-surround receptive fields and color opponency in the retina. Mechanisms of HC feedback remain unsettled, but one hypothesis proposes that an ephaptic mechanism may alter the extracellular electrical field surrounding photoreceptor synaptic terminals, thereby altering Ca2+ channel activity and photoreceptor output. An ephaptic voltage change produced by current flowing through open channels in the HC membrane should occur with no delay. To test for this mechanism, we measured kinetics of inhibitory feedback currents in Ambystoma tigrinum cones and rods evoked by hyperpolarizing steps applied to synaptically coupled HCs. Hyperpolarizing HCs stimulated inward feedback currents in cones that averaged 8–9 pA and exhibited a biexponential time course with time constants averaging 14–17 ms and 120–220 ms. Measurement of feedback-current kinetics was limited by three factors: (1) HC voltage-clamp speed, (2) cone voltage-clamp speed, and (3) kinetics of Ca2+ channel activation or deactivation in the photoreceptor terminal. These factors totaled ∼4–5 ms in cones meaning that the true fast time constants for HC-to-cone feedback currents were 9–13 ms, slower than expected for ephaptic voltage changes. We also compared speed of feedback to feedforward glutamate release measured at the same cone/HC synapses and found a latency for feedback of 11–14 ms. Inhibitory feedback from HCs to rods was also significantly slower than either measurement kinetics or feedforward release. The finding that inhibitory feedback from HCs to photoreceptors involves a significant delay indicates that it is not due to previously proposed ephaptic mechanisms. SIGNIFICANCE STATEMENT Lateral inhibitory feedback from horizontal cells (HCs) to photoreceptors creates center-surround receptive fields and color-opponent interactions. Although underlying mechanisms remain unsettled, a longstanding hypothesis proposes that

  16. The fundamental role of ecological feedback mechanisms for the adaptive management of seagrass ecosystems - a review

    DEFF Research Database (Denmark)

    Maxwell, Paul S.; Eklof, Johan S.; van Katwijk, Marieke M.

    2017-01-01

    Seagrass meadows are vital ecosystems in coastal zones worldwide, but are also under global threat. One of the major hurdles restricting the success of seagrass conservation and restoration is our limited understanding of ecological feedback mechanisms. In these ecosystems, multiple, self...... by modelling the interactions among two distinct above-and belowground feedbacks to demonstrate that interacting feedbacks are likely to be important for ecosystem resilience. On this basis, we propose a five-step adaptive management plan to address feedback dynamics for effective conservation and restoration...... of seagrass ecosystems. Here we review the causes and consequences of multiple feedbacks between seagrass and biotic and/or abiotic processes. We demonstrate how feedbacks have the potential to impose or reinforce regimes of either seagrass dominance or unvegetated substrate, and how the strength...

  17. Finite-time stabilisation of simple mechanical systems using continuous feedback

    Science.gov (United States)

    Sanyal, Amit K.; Bohn, Jan

    2015-04-01

    Stabilisation of simple mechanical systems in finite time with continuous state feedback is considered here. The dynamics are represented by generalised (local) coordinates. A general methodology to construct control Lyapunov functions that are Hölder continuous and that can be used to show finite-time stability of the feedback controlled system, is presented. This construction also gives the feedback control law, and results in the feedback system being Hölder continuous as well. Unlike Lipschitz continuous feedback control systems, the feedback control scheme given here converges to the desired equilibrium in finite time. Moreover, unlike discontinuous and hybrid control schemes, the feedback control law does not lead to chattering in the presence of measurement noise, does not excite unmodelled high-frequency dynamics, and can be implemented with actuators that can only deliver continuous control inputs. The advantages of continuous finite-time stabilisation over continuous asymptotic stabilisation of mechanical systems, has been described in some prior research on finite-time stabilisation of the double integrator. The finite-time stabilisation scheme given here generalises this prior research to multiple degree-of-freedom mechanical systems. A numerical comparison is carried out through numerical simulations on two example systems that are representative of a broad class of simple mechanical systems.

  18. Global Stability in Dynamical Systems with Multiple Feedback Mechanisms

    DEFF Research Database (Denmark)

    Andersen, Morten; Vinther, Frank; Ottesen, Johnny T.

    2016-01-01

    of the system. The proof relies on the contraction mapping theorem. Applications of this type of systems are numerous in biology, e.g., models of the hypothalamic-pituitary-adrenal axis and testosterone secretion. Some results important for modelling are: 1) Existence of an attractive trapping region....... This is a bounded set with non-negative elements where solutions cannot escape. All solutions are shown to converge to a “minimal” trapping region. 2) At least one fixed point exists. 3) Sufficient criteria for a unique fixed point are formulated. One case where this is fulfilled is when the feedbacks are negative....

  19. A dynamic model of the tubuloglomerular feedback mechanism

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H; Marsh, D J

    1990-01-01

    We have reported oscillations in proximal tubular pressure and flow and in distal tubular pressure and chloride concentration in halothane-anesthetized Sprague-Dawley rats. These variables oscillated at the same frequency in each animal, approximately 35 mHz, but were out of phase with each other....... We suggested that the oscillation arises within the tubuloglomerular feedback (TGF) system. As a test of this hypothesis, we have now developed a dynamic model to determine whether it can simulate the measured frequency and phase relationships with a realistic set of parameters. The model includes...... of mass. For a realistic set of parameter values the model accurately predicted oscillations with the same frequency and phase relationships among the oscillating variables as was found experimentally. Moreover, tubular NaCl handling significantly influenced the dynamic properties of the TGF system. Thus...

  20. Mechanical feedback coordinates cell wall expansion and assembly in yeast mating morphogenesis

    Science.gov (United States)

    2018-01-01

    The shaping of individual cells requires a tight coordination of cell mechanics and growth. However, it is unclear how information about the mechanical state of the wall is relayed to the molecular processes building it, thereby enabling the coordination of cell wall expansion and assembly during morphogenesis. Combining theoretical and experimental approaches, we show that a mechanical feedback coordinating cell wall assembly and expansion is essential to sustain mating projection growth in budding yeast (Saccharomyces cerevisiae). Our theoretical results indicate that the mechanical feedback provided by the Cell Wall Integrity pathway, with cell wall stress sensors Wsc1 and Mid2 increasingly activating membrane-localized cell wall synthases Fks1/2 upon faster cell wall expansion, stabilizes mating projection growth without affecting cell shape. Experimental perturbation of the osmotic pressure and cell wall mechanics, as well as compromising the mechanical feedback through genetic deletion of the stress sensors, leads to cellular phenotypes that support the theoretical predictions. Our results indicate that while the existence of mechanical feedback is essential to stabilize mating projection growth, the shape and size of the cell are insensitive to the feedback. PMID:29346368

  1. Parameter estimation in a stochastic model of the tubuloglomerular feedback mechanism in a rat nephron

    DEFF Research Database (Denmark)

    Ditlevsen, Susanne; Yip, Kay-Pong; Holstein-Rathlou, N.-H.

    2005-01-01

    A key parameter in the understanding of renal hemodynamics is the gain of the feedback function in the tubuloglomerular feedback mechanism. A dynamic model of autoregulation of renal blood flow and glomerular filtration rate has been extended to include a stochastic differential equations model...... analyzed, and the parameters characterizing the gain and the delay have been estimated. There was good agreement between the estimated values, and the values obtained for the same parameters in independent, previously published experiments....

  2. How mechanical context and feedback jointly determine the use of mechanical variables in length perception by dynamic touch

    NARCIS (Netherlands)

    Menger, Rudmer; Withagen, Rob

    2009-01-01

    Earlier studies have revealed that both mechanical context and feedback determine what mechanical invariant is used to perceive length by dynamic touch. In the present article, the authors examined how these two factors jointly constrain the informational variable that is relied upon. Participants

  3. Observed positive vegetation-rainfall feedbacks in the Sahel dominated by a moisture recycling mechanism.

    Science.gov (United States)

    Yu, Yan; Notaro, Michael; Wang, Fuyao; Mao, Jiafu; Shi, Xiaoying; Wei, Yaxing

    2017-11-30

    Classic, model-based theory of land-atmosphere interactions across the Sahel promote positive vegetation-rainfall feedbacks dominated by surface albedo mechanism. However, neither the proposed positive vegetation-rainfall feedback nor its underlying albedo mechanism has been convincingly demonstrated using observational data. Here, we present observational evidence for the region's proposed positive vegetation-rainfall feedback on the seasonal to interannual time scale, and find that it is associated with a moisture recycling mechanism, rather than the classic albedo-based mechanism. Positive anomalies of remotely sensed vegetation greenness across the Sahel during the late and post-monsoon periods favor enhanced evapotranspiration, precipitable water, convective activity and rainfall, indicative of amplified moisture recycling. The identified modest low-level cooling and anomalous atmospheric subsidence in response to positive vegetation greenness anomalies are counter to the responses expected through the classic vegetation-albedo feedback mechanism. The observational analysis further reveals enhanced dust emissions in response to diminished Sahel vegetation growth, potentially contributing to the positive vegetation-rainfall feedback.

  4. Accuracy of Evaluating Videotape Feedback and Defense Mechanisms.

    Science.gov (United States)

    Kipper, David A.; Ginot, Efrat

    1979-01-01

    Predicted that the accuracy of evaluating videotape replay of one's own behavior is related to the defense mechanism clusters of the evaluator. Results confirmed the prediction. Furthermore, subjects characterized by projection clusters tended to produce the greatest distortions, and those characterized by turning-against-self clusters evaluated…

  5. Effects of shrub and tree cover increase on the near-surface atmosphere in northern Fennoscandia

    Science.gov (United States)

    Rydsaa, Johanne H.; Stordal, Frode; Bryn, Anders; Tallaksen, Lena M.

    2017-09-01

    Increased shrub and tree cover in high latitudes is a widely observed response to climate change that can lead to positive feedbacks to the regional climate. In this study we evaluate the sensitivity of the near-surface atmosphere to a potential increase in shrub and tree cover in the northern Fennoscandia region. We have applied the Weather Research and Forecasting (WRF) model with the Noah-UA land surface module in evaluating biophysical effects of increased shrub cover on the near-surface atmosphere at a fine resolution (5.4 km × 5.4 km). Perturbation experiments are performed in which we prescribe a gradual increase in taller vegetation in the alpine shrub and tree cover according to empirically established bioclimatic zones within the study region. We focus on the spring and summer atmospheric response. To evaluate the sensitivity of the atmospheric response to inter-annual variability in climate, simulations were conducted for two contrasting years, one warm and one cold. We find that shrub and tree cover increase leads to a general increase in near-surface temperatures, with the highest influence seen during the snowmelt season and a more moderate effect during summer. We find that the warming effect is stronger in taller vegetation types, with more complex canopies leading to decreases in the surface albedo. Counteracting effects include increased evapotranspiration, which can lead to increased cloud cover, precipitation, and snow cover. We find that the strength of the atmospheric feedback is sensitive to snow cover variations and to a lesser extent to summer temperatures. Our results show that the positive feedback to high-latitude warming induced by increased shrub and tree cover is a robust feature across inter-annual differences in meteorological conditions and will likely play an important role in land-atmosphere feedback processes in the future.

  6. An exploratory pilot study of mechanisms of action within normative feedback for adult drinkers

    Directory of Open Access Journals (Sweden)

    Alexis Kuerbis

    2016-06-01

    Full Text Available Background. Normative feedback (NF, or receiving information about one’s drinking compared to peer drinking norms, is one of the most widely used brief interventions for prevention and intervention for hazardous alcohol use. NF has demonstrated predominantly small but significant effect sizes for intention to change and other drinking related outcomes. Identifying mechanisms of action may improve the effectiveness of NF; however, few studies have examined NF’s mechanisms of action, particularly among adults. Objective. This study is an exploratory analysis of two theorized mechanisms of NF: discrepancy (specifically personal dissonance—the affective response to feedback and belief in the accuracy of feedback. Method. Using Amazon’s Mechanical Turk, 87 men (n = 56 and women (n = 31 completed an online survey during which they were asked about their perceptions about their drinking and actual drinking behaviors. Then participants were provided tailored NF and evaluated for their reactions. Severity of discrepancy was measured by the difference between one’s estimated percentile ranking of drinking compared to peers and actual percentile ranking. Surprise and worry reported due to the discrepancy were proxies for personal dissonance. Participants were also asked if they believed the feedback and if they had any plans to change their drinking. Mediation analyses were implemented, exploring whether surprise, worry, or belief in the accuracy of feedback mediated severity of discrepancy’s impact on plan for change. Results. Among this sample of adult drinkers, severity of discrepancy did not predict plan for change, and personal dissonance did not mediate severity of discrepancy. Severity of discrepancy was mediated by belief in the accuracy of feedback. In addition, viewing one’s drinking as a problem prior to feedback and post-NF worry both predicted plan for change independently. Conclusions. Results revealed that NF may not work to

  7. Failure of feedback as a putative common mechanism of spreading depolarizations in migraine and stroke

    Science.gov (United States)

    Dahlem, Markus A.; Schneider, Felix M.; Schöll, Eckehard

    2008-06-01

    The stability of cortical function depends critically on proper regulation. Under conditions of migraine and stroke a breakdown of transmembrane chemical gradients can spread through cortical tissue. A concomitant component of this emergent spatio-temporal pattern is a depolarization of cells detected as slow voltage variations. The propagation velocity of ˜3mm/min indicates a contribution of diffusion. We propose a mechanism for spreading depolarizations (SD) that rests upon a nonlocal or noninstantaneous feedback in a reaction-diffusion system. Depending upon the characteristic space and time scales of the feedback, the propagation of cortical SD can be suppressed by shifting the bifurcation line, which separates the parameter regime of pulse propagation from the regime where a local disturbance dies out. The optimization of this feedback is elaborated for different control schemes and ranges of control parameters.

  8. Patterns of intermuscular inhibitory force feedback across cat hindlimbs suggest a flexible system for regulating whole limb mechanics.

    Science.gov (United States)

    Lyle, Mark A; Nichols, T Richard

    2018-02-01

    Prior work has suggested that Golgi tendon organ feedback, via its distributed network linking muscles spanning all joints, could be used by the nervous system to help regulate whole limb mechanics if appropriately organized. We tested this hypothesis by characterizing the patterns of intermuscular force-dependent feedback between the primary extensor muscles spanning the knee, ankle, and toes in decerebrate cat hindlimbs. Intermuscular force feedback was evaluated by stretching tendons of selected muscles in isolation and in pairwise combinations and then measuring the resulting force-dependent intermuscular interactions. The relative inhibitory feedback between extensor muscles was examined, as well as symmetry of the interactions across limbs. Differences in the directional biases of inhibitory feedback were observed across cats, with three patterns identified as points on a spectrum: pattern 1, directional bias of inhibitory feedback onto the ankle extensors and toe flexors; pattern 2, convergence of inhibitory feedback onto ankle extensors and mostly balanced inhibitory feedback between vastus muscle group and flexor hallucis longus, and pattern 3, directional bias of inhibitory feedback onto ankle and knee extensors. The patterns of inhibitory feedback, while different across cats, were symmetric across limbs of individual cats. The variable but structured distribution of force feedback across cat hindlimbs provides preliminary evidence that inhibitory force feedback could be a regulated neural control variable. We propose the directional biases of inhibitory feedback observed experimentally could provide important task-dependent benefits, such as directionally appropriate joint compliance, joint coupling, and compensation for nonuniform inertia. NEW & NOTEWORTHY Feedback from Golgi tendon organs project widely among extensor motor nuclei in the spinal cord. The distributed nature of force feedback suggests these pathways contribute to the global regulation

  9. The fundamental role of ecological feedback mechanisms for the adaptive management of seagrass ecosystems - a review.

    Science.gov (United States)

    Maxwell, Paul S; Eklöf, Johan S; van Katwijk, Marieke M; O'Brien, Katherine R; de la Torre-Castro, Maricela; Boström, Christoffer; Bouma, Tjeerd J; Krause-Jensen, Dorte; Unsworth, Richard K F; van Tussenbroek, Brigitta I; van der Heide, Tjisse

    2017-08-01

    Seagrass meadows are vital ecosystems in coastal zones worldwide, but are also under global threat. One of the major hurdles restricting the success of seagrass conservation and restoration is our limited understanding of ecological feedback mechanisms. In these ecosystems, multiple, self-reinforcing feedbacks can undermine conservation efforts by masking environmental impacts until the decline is precipitous, or alternatively they can inhibit seagrass recovery in spite of restoration efforts. However, no clear framework yet exists for identifying or dealing with feedbacks to improve the management of seagrass ecosystems. Here we review the causes and consequences of multiple feedbacks between seagrass and biotic and/or abiotic processes. We demonstrate how feedbacks have the potential to impose or reinforce regimes of either seagrass dominance or unvegetated substrate, and how the strength and importance of these feedbacks vary across environmental gradients. Although a myriad of feedbacks have now been identified, the co-occurrence and likely interaction among feedbacks has largely been overlooked to date due to difficulties in analysis and detection. Here we take a fundamental step forward by modelling the interactions among two distinct above- and belowground feedbacks to demonstrate that interacting feedbacks are likely to be important for ecosystem resilience. On this basis, we propose a five-step adaptive management plan to address feedback dynamics for effective conservation and restoration strategies. The management plan provides guidance to aid in the identification and prioritisation of likely feedbacks in different seagrass ecosystems. © 2016 Cambridge Philosophical Society.

  10. Modelling feedback mechanisms in the carbon cycle: balancing the carbon budget

    Science.gov (United States)

    Rotmans, J.; den Elzen, M. G. J.

    1993-09-01

    Within the carbon cycle feedback, mechanisms that amplify or dampen the exchange of carbon dioxide between the different reservoirs to enhance concentrations of carbon dioxide and increase temperature from anthropogenic perturbations, play a crucial rôle. Quite a lot of these feedbacks are known, but most of them only potentially. This article evaluates the role of a number of these feedback processes within the carbon cycle. In order to assess their impact, some terrestrial feedbacks have been built into a coupled carbon cycle and climate model, as part of the integrated climate assessment model IMAGE. A number of simulation experiments have been performed with this coupled carbon cycle/climate model to compare historical atmospheric concentration values of carbon dioxide with simulated values. Also global biospheric and oceanic carbon fluxes were validated against other modelling estimates. Based on the assumptions of the IPCC's 1990 Business-as-Usual (BaU-1990) scenario, future projections of the carbon dioxide concentration have been made. A key principle in this is that we have used the modelled feedbacks in order to balance the past and present carbon budget. For atmospheric carbon dioxide, this results in substantially lower projections than the IPCC-estimates: the difference in 2100 is approximately 16% from the 1990 level. Furthermore, the IPCC's 'best guess' or 'central estimate' value of the CO2 concentration in 2100 falls outside the uncertainty range estimated with our balanced modelling approach. Sensitivity experiments with the model have been performed to quantify to what extent the terrestrial feedback processes and oceanic fluxes influence the global carbon balance in the model. It is shown that a historical and present carbon balance can be obtained in many different ways, resulting in different biospheric fluxes and thus in considerably different atmospheric CO2 projections.

  11. SAFCM: A Security-Aware Feedback Control Mechanism for Distributed Real-Time Embedded Systems

    DEFF Research Database (Denmark)

    Ma, Yue; Jiang, Wei; Sang, Nan

    2012-01-01

    for the whole system. We propose a "security level" metric based on an evolution of cryptography algorithms used in embedded systems. Experimental results demonstrate that SAFCM not only has the excellent adaptivity compared to open-loop mechanism, but also has a better overall performance than PID control...... the real-time requirements. This paper proposes a Security-Aware Feedback Control Mechanism (SAFCM) which has the ability to dynamically change the security level to guarantee soft real-time requirements and make the security protection as strong as possible. In order to widely support distributed real......-time systems, a multi-input multi-output feedback loop is designed and a model predictive controller is deployed based on an equation model that describes the dynamic behavior of the DRE systems. This control loop uses security level scaling to globally control the CPU utilization and security performance...

  12. Effect of chyme viscosity and nutrient feedback mechanism on gastric emptying.

    Science.gov (United States)

    Moxon, Thomas E; Nimmegeers, Philippe; Telen, Dries; Fryer, Peter J; Van Impe, Jan; Bakalis, Serafim

    2017-11-02

    A comprehensive mathematical model of the digestive processes in humans could allow for better design of functional foods which may play a role in stemming the prevalence of food related diseases around the world. This work presents a mathematical model for a nutrient based feedback mechanism controlling gastric emptying, which has been identified in vivo by numerous researchers. The model also takes into account the viscosity of nutrient meals upon gastric secretions and emptying. The results show that modelling the nutrient feedback mechanism as an on/off system, with an initial emptying rate dependent upon the secretion rate (which is a function of the gastric chyme viscosity) provides a good fit to the trends of emptying rate for liquid meals of low and high nutrient content with varying viscosity.

  13. Effects of mechanical feedback on the stability of cardiac scroll waves: A bidomain electro-mechanical simulation study.

    Science.gov (United States)

    Colli Franzone, P; Pavarino, L F; Scacchi, S

    2017-09-01

    In this work, we investigate the influence of cardiac tissue deformation on re-entrant wave dynamics. We have developed a 3D strongly coupled electro-mechanical Bidomain model posed on an ideal monoventricular geometry, including fiber direction anisotropy and stretch-activated currents (SACs). The cardiac mechanical deformation influences the bioelectrical activity with two main mechanical feedback: (a) the geometric feedback (GEF) due to the presence of the deformation gradient in the diffusion coefficients and in a convective term depending on the deformation rate and (b) the mechano-electric feedback (MEF) due to SACs. Here, we investigate the relative contribution of these two factors with respect to scroll wave stability. We extend the previous works [Keldermann et al., Am. J. Physiol. Heart Circ. Physiol. 299, H134-H143 (2010) and Hu et al., PLoS One 8(4), e60287 (2013)] that were based on the Monodomain model and a simple non-selective linear SAC, while here we consider the full Bidomain model and both selective and non-selective components of SACs. Our simulation results show that the stability of cardiac scroll waves is influenced by MEF, which in case of low reversal potential of non-selective SACs might be responsible for the onset of ventricular fibrillation; GEF increases the scroll wave meandering but does not determine the scroll wave stability.

  14. On the dynamic forcing of short-term climate fluctuations by feedback mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Reiter, E.R.

    1979-09-01

    The energies involved in the general circulation of the atmosphere, especially the zonal available potential energy, show considerable interannual variability, suggesting the presence of various internal feedback mechanisms in the ocean-atmosphere system. Sea-surface temperature (SST) variations appear to have some effect on the hydrological cycle. The possible existence of feedback mechanisms between ocean and atmosphere seem to be evident in some of the data from the North Pacific and North Atlantic. One of these proposed mechanisms involves the variation in the convergence between the North and South Pacific trade-wind systems and is strongly reflected in rainfall variability within the dry region of the equatorial Pacific. Similar variations appear in low-latitude SST anomalies. The convergence between the two trade-wind systems in the Atlantic region also undergoes marked interannual variations. This quasi-biennial oscillation (QBO) in trade-wind convergence over the Atlantic appears to be tied to the global QBO of equatorial stratospheric winds and to regional rainfall regimes in the dry region of northeastern Brazil. A variability pattern of SST's with a QBO has been detected off the coast of Senegal, in the Gulf of Guinea and even in the Gulf Stream as it leaves the North American continental shelf. Possible physical connections between some of these QBO's are pointed out by a hypothetical feedback model. It is also suggested that interaction of a QBO with the annual cycle may lead to beating frequencies resembling climatic trends of a duration of several years.

  15. Can interactive educational technologies support the link between ultrasound theory and practice via feedback mechanisms?

    Science.gov (United States)

    Dickson, Diane

    2015-05-01

    Linking theory to practice is an area of concern for ultrasound students, clinical mentors and academic staff. The link between theory and practice requires a robust clinical mentorship scheme in addition to careful curricula design considerations to improve student outcomes. The introduction of interactive technology in education provides ripe opportunity to improve feedback to students to support the link between theory and practice. A series of three interactive learning and teaching activities were designed and delivered to a PostGraduate Ultrasound cohort, after which, evaluation was performed to answer the research question: Which interactive technologies support the link between theory and practice through improved feedback mechanisms? An action research methodology was adopted involving an enquiry based literature review, planning, design and action process. Data were collected following action of three interactive teaching and learning sessions within the Medical Ultrasound cohort of 2013/2014 at Glasgow Caledonian University via a paper based questionnaire. A 100% response rate was achieved (n = 14). All three interactive learning and teaching sessions were considered with 100% highest point agreement to support the link between ultrasound theory and practice via feedback. Students found all three designed and facilitated sessions valuable and relevant to their learning, which in turn provided positive experiences which were perceived to support the link between theory and practice through feedback. These activities can be considered valuable in Postgraduate Ultrasound education.

  16. Block backstepping design of nonlinear state feedback control law for underactuated mechanical systems

    CERN Document Server

    Rudra, Shubhobrata; Maitra, Madhubanti

    2017-01-01

    This book presents a novel, generalized approach to the design of nonlinear state feedback control laws for a large class of underactuated mechanical systems based on application of the block backstepping method. The control law proposed here is robust against the effects of model uncertainty in dynamic and steady-state performance and addresses the issue of asymptotic stabilization for the class of underactuated mechanical systems. An underactuated system is defined as one for which the dimension of space spanned by the configuration vector is greater than that of the space spanned by the control variables. Control problems concerning underactuated systems currently represent an active field of research due to their broad range of applications in robotics, aerospace, and marine contexts. The book derives a generalized theory of block backstepping control design for underactuated mechanical systems, and examines several case studies that cover interesting examples of underactuated mechanical systems. The math...

  17. Feedback mechanisms control coexistence in a stem cell model of acute myeloid leukaemia.

    Science.gov (United States)

    Crowell, Helena L; MacLean, Adam L; Stumpf, Michael P H

    2016-07-21

    Haematopoietic stem cell dynamics regulate healthy blood cell production and are disrupted during leukaemia. Competition models of cellular species help to elucidate stem cell dynamics in the bone marrow microenvironment (or niche), and to determine how these dynamics impact leukaemia progression. Here we develop two models that target acute myeloid leukaemia with particular focus on the mechanisms that control proliferation via feedback signalling. It is within regions of parameter space permissive of coexistence that the effects of competition are most subtle and the clinical outcome least certain. Steady state and linear stability analyses identify parameter regions that allow for coexistence to occur, and allow us to characterise behaviour near critical points. Where analytical expressions are no longer informative, we proceed statistically and sample parameter space over a coexistence region. We find that the rates of proliferation and differentiation of healthy progenitors exert key control over coexistence. We also show that inclusion of a regulatory feedback onto progenitor cells promotes healthy haematopoiesis at the expense of leukaemia, and that - somewhat paradoxically - within the coexistence region feedback increases the sensitivity of the system to dominance by one lineage over another. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  18. Role of the Qinghai-Xizang plateau in feedback mechanisms affecting the planetary circulation

    Energy Technology Data Exchange (ETDEWEB)

    Reiter, E.R.; Yi-Hui, D.

    1980-01-01

    It has been recognized for some time that the Qinghai-Xizang plateau is of great importance in generating planetary long-waves which, in resonance with similar waves induced by the Rocky Mountains, lead to the familiar pattern of quasi-stationary Rossby waves observed on monthly-mean upper level pressure charts. Seasonal forcing of flow patterns also appears to be particularly strong in the Qinghai-Xizang plateau region. Recent investigations suggest that the Qinghai-Xizang plateau may also be involved in feedback mechanisms which control in an important way the interannual variability of the general circulation of the atmosphere. It appears that the effects of the Qinghai-Xizang plateau on the interannual variability of the atmospheric circulation over Asia are but one important manifestation of a network of feedback mechanisms, ranging from the El Nino problems along the Peruvian coast to droughts in the Sahel region. A better understanding of each of the mechanisms involved will lead us closer to successful long-range forecasting of some of the weather phenomena which have a considerable effect on local and regional economics.

  19. The Richness of Open-ended Play - Rules, feedback and adaptation mechanisms in intelligent play environments

    Directory of Open Access Journals (Sweden)

    Pepijn Rijnbout

    2015-11-01

    Full Text Available How can we design intelligent play environments for open-ended play that support richness in play? Rich play can be described as ongoing play that changes over time in character, form and nature. This paper elaborates on our initial insights on how rules and goals develop from interaction opportunities of the system, based on two pilot studies with an interactive play environment for open-ended play. Furthermore we will discuss the roles of feedback and adaptation mechanisms in the environment. Those system properties will change the interaction opportunities to match with the current situation in the play environment and to support richness in play.

  20. Investigation of Reactivity Feedback Mechanism of Axial and Radial Expansion Effect of Metal-Fueled Sodium-Cooled Fast Reactor

    International Nuclear Information System (INIS)

    Seong, Seung-Hwan; Choi, Chi-Woong; Jeong, Tae-Kyung; Ha, Gi-Seok

    2015-01-01

    The major inherent reactivity feedback models for a ceramic fuel used in a conventional light water reactor are Doppler feedback and moderator feedback. The metal fuel has these two reactivity feedback mechanisms previously mentioned. In addition, the metal fuel has two more reactivity feedback models related to the thermal expansion phenomena of the metal fuel. Since the metal fuel has a good capability to expand according to the temperature changes of the core, two more feedback mechanisms exist. These additional two feedback mechanism are important to the inherent safety of metal fuel and can make metal-fueled SFR safer than oxide-fueled SFR. These phenomena have already been applied to safety analysis on design extended condition. In this study, the effect of these characteristics on power control capability was examined through a simple load change operation. The axial expansion mechanism is induced from the change of the fuel temperature according to the change of the power level of PGSFR. When the power increases, the fuel temperatures in the metal fuel will increase and then the reactivity will decrease due to the axial elongation of the metal fuel. To evaluate the expansion effect, 2 cases were simulated with the same scenario by using MMS-LMR code developed at KAERI. The first simulation was to analyze the change of the reactor power according to the change of BOP power without the reactivity feedback model of the axial and radial expansion of the core during the power transient event. That is to say, the core had only two reactivity feedback mechanism of Doppler and coolant temperature

  1. A mechanical-biochemical feedback loop regulates remodeling in the actin cytoskeleton.

    Science.gov (United States)

    Stachowiak, Matthew R; Smith, Mark A; Blankman, Elizabeth; Chapin, Laura M; Balcioglu, Hayri E; Wang, Shuyuan; Beckerle, Mary C; O'Shaughnessy, Ben

    2014-12-09

    Cytoskeletal actin assemblies transmit mechanical stresses that molecular sensors transduce into biochemical signals to trigger cytoskeletal remodeling and other downstream events. How mechanical and biochemical signaling cooperate to orchestrate complex remodeling tasks has not been elucidated. Here, we studied remodeling of contractile actomyosin stress fibers. When fibers spontaneously fractured, they recoiled and disassembled actin synchronously. The disassembly rate was accelerated more than twofold above the resting value, but only when contraction increased the actin density to a threshold value following a time delay. A mathematical model explained this as originating in the increased overlap of actin filaments produced by myosin II-driven contraction. Above a threshold overlap, this mechanical signal is transduced into accelerated disassembly by a mechanism that may sense overlap directly or through associated elastic stresses. This biochemical response lowers the actin density, overlap, and stresses. The model showed that this feedback mechanism, together with rapid stress transmission along the actin bundle, spatiotemporally synchronizes actin disassembly and fiber contraction. Similar actin remodeling kinetics occurred in expanding or contracting intact stress fibers but over much longer timescales. The model accurately described these kinetics, with an almost identical value of the threshold overlap that accelerates disassembly. Finally, we measured resting stress fibers, for which the model predicts constant actin overlap that balances disassembly and assembly. The overlap was indeed regulated, with a value close to that predicted. Our results suggest that coordinated mechanical and biochemical signaling enables extended actomyosin assemblies to adapt dynamically to the mechanical stresses they convey and direct their own remodeling.

  2. Distributed mechanical feedback in arthropods and robots simplifies control of rapid running on challenging terrain.

    Science.gov (United States)

    Spagna, J C; Goldman, D I; Lin, P-C; Koditschek, D E; Full, R J

    2007-03-01

    Terrestrial arthropods negotiate demanding terrain more effectively than any search-and-rescue robot. Slow, precise stepping using distributed neural feedback is one strategy for dealing with challenging terrain. Alternatively, arthropods could simplify control on demanding surfaces by rapid running that uses kinetic energy to bridge gaps between footholds. We demonstrate that this is achieved using distributed mechanical feedback, resulting from passive contacts along legs positioned by pre-programmed trajectories favorable to their attachment mechanisms. We used wire-mesh experimental surfaces to determine how a decrease in foothold probability affects speed and stability. Spiders and insects attained high running speeds on simulated terrain with 90% of the surface contact area removed. Cockroaches maintained high speeds even with their tarsi ablated, by generating horizontally oriented leg trajectories. Spiders with more vertically directed leg placement used leg spines, which resulted in more effective distributed contact by interlocking with asperities during leg extension, but collapsing during flexion, preventing entanglement. Ghost crabs, which naturally lack leg spines, showed increased mobility on wire mesh after the addition of artificial, collapsible spines. A bioinspired robot, RHex, was redesigned to maximize effective distributed leg contact, by changing leg orientation and adding directional spines. These changes improved RHex's agility on challenging surfaces without adding sensors or changing the control system.

  3. RADIATIVE AND MOMENTUM-BASED MECHANICAL ACTIVE GALACTIC NUCLEUS FEEDBACK IN A THREE-DIMENSIONAL GALAXY EVOLUTION CODE

    International Nuclear Information System (INIS)

    Choi, Ena; Ostriker, Jeremiah P.; Naab, Thorsten; Johansson, Peter H.

    2012-01-01

    We study the growth of black holes (BHs) in galaxies using three-dimensional smoothed particle hydrodynamic simulations with new implementations of the momentum mechanical feedback, and restriction of accreted elements to those that are gravitationally bound to the BH. We also include the feedback from the X-ray radiation emitted by the BH, which heats the surrounding gas in the host galaxies, and adds radial momentum to the fluid. We perform simulations of isolated galaxies and merging galaxies and test various feedback models with the new treatment of the Bondi radius criterion. We find that overall the BH growth is similar to what has been obtained by earlier works using the Springel, Di Matteo, and Hernquist algorithms. However, the outflowing wind velocities and mechanical energy emitted by winds are considerably higher (v w ∼ 1000-3000 km s –1 ) compared to the standard thermal feedback model (v w ∼ 50-100 km s –1 ). While the thermal feedback model emits only 0.1% of BH released energy in winds, the momentum feedback model emits more than 30% of the total energy released by the BH in winds. In the momentum feedback model, the degree of fluctuation in both radiant and wind output is considerably larger than in standard treatments. We check that the new model of BH mass accretion agrees with analytic results for the standard Bondi problem.

  4. Tunable Coupling to a Mechanical Oscillator Circuit Using a Coherent Feedback Network

    Directory of Open Access Journals (Sweden)

    Joseph Kerckhoff

    2013-06-01

    Full Text Available We demonstrate a fully cryogenic microwave feedback network composed of modular superconducting devices connected by transmission lines and designed to control a mechanical oscillator that is coupled to one of the devices. The network features an electromechanical device and a tunable controller that coherently receives, processes, and feeds back continuous microwave signals that modify the dynamics and readout of the mechanical state. While previous electromechanical systems represent some compromise between efficient control and efficient readout of the mechanical state, as set by the electromagnetic decay rate, the tunable controller produces a closed-loop network that can be dynamically and continuously tuned between both extremes much faster than the mechanical response time. We demonstrate that the microwave decay rate may be modulated by at least a factor of 10 at a rate greater than 10^{4} times the mechanical response rate. The system is easy to build and suggests that some useful functions may arise most naturally at the network level of modular, quantum electromagnetic devices.

  5. Modeling land-surface/atmosphere dynamics for CHAMMP

    International Nuclear Information System (INIS)

    Gutowski, W.J. Jr.

    1993-01-01

    Project progress is described on a DOE CHAMP project to model the land-surface/atmosphere coupling in a heterogeneous environment. This work is a collaboration between scientists at Iowa State University and the University of New Hampshire. Work has proceeded in two areas: baseline model coupling and data base development for model validation. The core model elements (land model, atmosphere model) have been ported to the Principal Investigator's computing system and baseline coupling has commenced. The initial target data base is the set of observations from the FIFE field campaign, which is in the process of being acquired. For the remainder of the project period, additional data from the region surrounding the FIFE site and from other field campaigns will be acquired to determine how to best extrapolate results from the initial target region to the rest of the globe. In addition, variants of the coupled model will be used to perform experiments examining resolution requirements and coupling strategies for land-atmosphere coupling in a heterogeneous environment

  6. Indirect adaptive output feedback control of a biorobotic AUV using pectoral-like mechanical fins

    International Nuclear Information System (INIS)

    Naik, Mugdha S; Singh, Sahjendra N; Mittal, Rajat

    2009-01-01

    This paper treats the question of servoregulation of autonomous underwater vehicles (AUVs) in the yaw plane using pectoral-like mechanical fins. The fins attached to the vehicle have oscillatory swaying and yawing motion. The bias angle of the angular motion of the fin is used for the purpose of control. Of course, the design approach considered here is applicable to AUVs for other choices of oscillation patterns of the fins, which produce periodic forces and moments. It is assumed that the vehicle parameters, hydrodynamic coefficients, as well the fin forces and moments are unknown. For the trajectory control of the yaw angle, a sampled-data indirect adaptive control system using output (yaw angle) feedback is derived. The control system has a modular structure, which includes a parameter identifier and a stabilizer. For the control law derivation, an internal model of the exosignals (reference signal (constant or ramp) and constant disturbance) is included. Unlike the direct adaptive control scheme, the derived control law is applicable to minimum as well as nonminimum phase biorobotic AUVs (BAUVs). This is important, because for most of the fin locations on the vehicle, the model is a nonminimum phase. In the closed-loop system, the yaw angle trajectory tracking error converges to zero and the remaining state variables remain bounded. Simulation results are presented which show that the derived modular control system accomplishes precise set point yaw angle control and turning maneuvers in spite of the uncertainties in the system parameters using only yaw angle feedback

  7. Expression of Ski can act as a negative feedback mechanism on retinoic acid signaling.

    Science.gov (United States)

    Melling, Meaghan A; Friendship, Charlotte R C; Shepherd, Trevor G; Drysdale, Thomas A

    2013-06-01

    Retinoic acid signaling is essential for many aspects of early development in vertebrates. To control the levels of signaling, several retinoic acid target genes have been identified that act to suppress retinoic acid signaling in a negative feedback loop. The nuclear protein Ski has been extensively studied for its ability to suppress transforming growth factor-beta (TGF-β) signaling but has also been implicated in the repression of retinoic acid signaling. We demonstrate that ski expression is up-regulated in response to retinoic acid in both early Xenopus embryos and in human cell lines. Blocking retinoic acid signaling using a retinoic acid antagonist results in a corresponding decrease in the levels of ski mRNA. Finally, overexpression of SKI in human cells results in reduced levels of CYP26A1 mRNA, a known target of retinoic acid signaling. Our results, coupled with the known ability of Ski to repress retinoic acid signaling, demonstrate that Ski expression is a novel negative feedback mechanism acting on retinoic acid signaling. Copyright © 2013 Wiley Periodicals, Inc.

  8. Inhibition of Receptor Dimerization as a Novel Negative Feedback Mechanism of EGFR Signaling.

    Directory of Open Access Journals (Sweden)

    Malgorzata Kluba

    Full Text Available Dimerization of the epidermal growth factor receptor (EGFR is crucial for initiating signal transduction. We employed raster image correlation spectroscopy to continuously monitor the EGFR monomer-dimer equilibrium in living cells. EGFR dimer formation upon addition of EGF showed oscillatory behavior with a periodicity of about 2.5 min, suggesting the presence of a negative feedback loop to monomerize the receptor. We demonstrated that monomerization of EGFR relies on phospholipase Cγ, protein kinase C, and protein kinase D (PKD, while being independent of Ca2+ signaling and endocytosis. Phosphorylation of the juxtamembrane threonine residues of EGFR (T654/T669 by PKD was identified as the factor that shifts the monomer-dimer equilibrium of ligand bound EGFR towards the monomeric state. The dimerization state of the receptor correlated with the activity of an extracellular signal-regulated kinase, downstream of the EGFR. Based on these observations, we propose a novel, negative feedback mechanism that regulates EGFR signaling via receptor monomerization.

  9. Modulation of LTP/LTD balance in STDP by an activity-dependent feedback mechanism.

    Science.gov (United States)

    Kubota, Shigeru; Rubin, Jonathan; Kitajima, Tatsuo

    2009-01-01

    Spike-timing-dependent plasticity (STDP) has been suggested to play a role in the development of functional neuronal connections. However, for STDP to contribute to the synaptic organization, its learning curve should satisfy a requirement that the magnitude of long-term potentiation (LTP) is approximately the same as that of long-term depression (LTD). Without such balance between LTP and LTD, all the synapses are potentiated toward the upper limit or depressed toward the lower limit. Therefore, in this study, we explore the mechanisms by which the LTP/LTD balance in STDP can be modulated adequately. We examine a plasticity model that incorporates an activity-dependent feedback (ADFB) mechanism, wherein LTP induction is suppressed by higher postsynaptic activity. In this model, strengthening an ADFB function gradually decreases the temporal average of the ratio of the magnitude of LTP to that of LTD, whereas enhancing background inhibition augments this ratio. Additionally, correlated inputs can be strengthened or weakened depending on whether the correlation time is shorter or longer than a threshold value, respectively, suggesting that STDP may lead to either Hebbian or anti-Hebbian plasticity outcomes. At an intermediate range of correlation times, the reversal between the two distinct plasticity regimes can occur by changing the level of ADFB modulation and inhibition, providing a physiological mechanism for neurons to select from functionally different forms of learning rules.

  10. Evaluating the negative or valuing the positive? Neural mechanisms supporting feedback-based learning across development.

    Science.gov (United States)

    van Duijvenvoorde, Anna C K; Zanolie, Kiki; Rombouts, Serge A R B; Raijmakers, Maartje E J; Crone, Eveline A

    2008-09-17

    How children learn from positive and negative performance feedback lies at the foundation of successful learning and is therefore of great importance for educational practice. In this study, we used functional magnetic resonance imaging (fMRI) to examine the neural developmental changes related to feedback-based learning when performing a rule search and application task. Behavioral results from three age groups (8-9, 11-13, and 18-25 years of age) demonstrated that, compared with adults, 8- to 9-year-old children performed disproportionally more inaccurately after receiving negative feedback relative to positive feedback. Additionally, imaging data pointed toward a qualitative difference in how children and adults use performance feedback. That is, dorsolateral prefrontal cortex and superior parietal cortex were more active after negative feedback for adults, but after positive feedback for children (8-9 years of age). For 11- to 13-year-olds, these regions did not show differential feedback sensitivity, suggesting that the transition occurs around this age. Pre-supplementary motor area/anterior cingulate cortex, in contrast, was more active after negative feedback in both 11- to 13-year-olds and adults, but not 8- to 9-year-olds. Together, the current data show that cognitive control areas are differentially engaged during feedback-based learning across development. Adults engage these regions after signals of response adjustment (i.e., negative feedback). Young children engage these regions after signals of response continuation (i.e., positive feedback). The neural activation patterns found in 11- to 13-year-olds indicate a transition around this age toward an increased influence of negative feedback on performance adjustment. This is the first developmental fMRI study to compare qualitative changes in brain activation during feedback learning across distinct stages of development.

  11. A new mechanical stellar wind feedback model for the Rosette Nebula

    Science.gov (United States)

    Wareing, C. J.; Pittard, J. M.; Wright, N. J.; Falle, S. A. E. G.

    2018-04-01

    The famous Rosette Nebula has an evacuated central cavity formed from the stellar winds ejected from the 2-6 Myr old codistant and comoving central star cluster NGC 2244. However, with upper age estimates of less than 110 000 yr, the central cavity is too young compared to NGC 2244 and existing models do not reproduce its properties. A new proper motion study herein using Gaia data reveals the ejection of the most massive star in the Rosette, HD 46223, from NGC 2244 occurred 1.73 (+0.34, -0.25) Myr (1σ uncertainty) in the past. Assuming this ejection was at the birth of the most massive stars in NGC 2244, including the dominant centrally positioned HD 46150, the age is set for the famous ionized region at more than 10 times that derived for the cavity. Here, we are able to reproduce the structure of the Rosette Nebula, through simulation of mechanical stellar feedback from a 40 M⊙ star in a thin sheet-like molecular cloud. We form the 135 000 M⊙ cloud from thermally unstable diffuse interstellar medium (ISM) under the influence of a realistic background magnetic field with thermal/magnetic pressure equilibrium. Properties derived from a snapshot of the simulation at 1.5 Myr, including cavity size, stellar age, magnetic field, and resulting inclination to the line of sight, match those derived from observations. An elegant explanation is thus provided for the stark contrast in age estimates based on realistic diffuse ISM properties, molecular cloud formation and stellar wind feedback.

  12. Mechanisms and Model Diversity of Trade-Wind Shallow Cumulus Cloud Feedbacks: A Review

    Science.gov (United States)

    Vial, Jessica; Bony, Sandrine; Stevens, Bjorn; Vogel, Raphaela

    2017-11-01

    Shallow cumulus clouds in the trade-wind regions are at the heart of the long standing uncertainty in climate sensitivity estimates. In current climate models, cloud feedbacks are strongly influenced by cloud-base cloud amount in the trades. Therefore, understanding the key factors controlling cloudiness near cloud-base in shallow convective regimes has emerged as an important topic of investigation. We review physical understanding of these key controlling factors and discuss the value of the different approaches that have been developed so far, based on global and high-resolution model experimentations and process-oriented analyses across a range of models and for observations. The trade-wind cloud feedbacks appear to depend on two important aspects: (1) how cloudiness near cloud-base is controlled by the local interplay between turbulent, convective and radiative processes; (2) how these processes interact with their surrounding environment and are influenced by mesoscale organization. Our synthesis of studies that have explored these aspects suggests that the large diversity of model responses is related to fundamental differences in how the processes controlling trade cumulus operate in models, notably, whether they are parameterized or resolved. In models with parameterized convection, cloudiness near cloud-base is very sensitive to the vigor of convective mixing in response to changes in environmental conditions. This is in contrast with results from high-resolution models, which suggest that cloudiness near cloud-base is nearly invariant with warming and independent of large-scale environmental changes. Uncertainties are difficult to narrow using current observations, as the trade cumulus variability and its relation to large-scale environmental factors strongly depend on the time and/or spatial scales at which the mechanisms are evaluated. New opportunities for testing physical understanding of the factors controlling shallow cumulus cloud responses using

  13. Ocean-atmosphere feedback mechanisms and climatic change. [Weather forecasting based on available 80-year data

    Energy Technology Data Exchange (ETDEWEB)

    Reiter, E.R.

    1978-01-01

    The North Pacific ocean north of 40/sup 0/N has undergone a quite dramatic cooling trend since approximately 1963. Lowest temperature anomalies were reached during 1976, presaging the cold winter of 1976/77 over the eastern United States. South of 40/sup 0/N no significant cooling trends could be detected in the Pacific surface waters. The North Atlantic ocean was subject to similar temperature trends. The North Pacific cooling trend of recent years is viewed in the context of long-period sea surface temperature (SST) records, dating back to 1900. The recent cooling trend, indeed, started in 1963, and was preceded by a slight cooling and then warming between the late 1940's and 1963. A warming trend seems to have provailed between 1928 and the late 1940's. At this time we do not know the precise cause of the cooling trend in the oceans of the northern hemisphere. The fact that the zonal component of the North Pacific trade winds underwent a secular trend provides a clue to the possible existence of a feedback mechanism between ocean and atmosphere. It appears that the secular trend in trade winds peaked between 1967 and 1969, whereas the North Pacific cooled, at least until 1976. We have not yet been able to establish a physical reason for a possible time lag of the order of 10 years between an atmosphere-ocean feedback. If such a lag could be established, either from past data or from physical reasoning, it would indicate that the North Pacific is on the brink of a warming trend.

  14. A feedback mechanism controlling SCRAMBLED receptor accumulation and cell-type pattern in Arabidopsis.

    Science.gov (United States)

    Kwak, Su-Hwan; Schiefelbein, John

    2008-12-23

    Cellular pattern formation in the root epidermis of Arabidopsis occurs in a position-dependent manner, generating root-hair (H) cells contacting two underlying cortical cells and nonhair (N) cells contacting one cortical cell. SCRAMBLED (SCM), a leucine-rich repeat receptor-like kinase (LRR-RLK), mediates this process through its effect on a downstream transcription factor regulatory network. After perception of a positional cue, the SCM signaling pathway is proposed to preferentially repress WEREWOLF (WER) transcription factor expression in H cells and thereby bias the outcome of mutual lateral inhibition acting between H and N cells. However, the molecular mechanism responsible for this preferential SCM signaling is unknown. Here, we analyze the distribution of the SCM receptor and the biological effect of altering its accumulation pattern. We find that SCM expression and accumulation in the epidermal cell layer is necessary and sufficient to direct the cell-type pattern. Further, SCM preferentially accumulates in H cells, and this accumulation pattern is dependent on the downstream transcription factors. Thus, SCM participates in an autoregulatory feedback loop, enabling cells engaged in SCM signaling to maintain high levels of SCM receptor, which provides a simple mechanism for reinforcing a bias in receptor-mediated signaling to ensure robust pattern formation.

  15. Mechanisms and Feedbacks Causing Changes in Upper Stratospheric Ozone in the 21st Century

    Science.gov (United States)

    Oman, Luke; Waugh, D. W.; Kawa, S. R.; Stolarski, R. S.; Douglass, A. R.; Newman, P. A.

    2009-01-01

    Stratospheric ozone is expected to increase during the 21st century as the abundance of halogenated ozone-depleting substances decrease to 1960 values. However, climate change will likely alter this "recovery" of stratospheric ozone by changing stratospheric temperatures, circulation, and abundance of reactive chemical species. Here we quantity the contribution of different mechanisms to changes in upper stratospheric ozone from 1960 to 2100 in the Goddard Earth Observing System Chemistry-Climate Model (GEOS CCM), using multiple linear regression analysis applied to simulations using either Alb or A2 greenhouse gas (GHG) scenarios. In both these scenarios upper stratospheric ozone has a secular increase over the 21st century. For the simulation using the Alb GHG scenario, this increase is determined by the decrease in halogen amounts and the greenhouse gas induced cooling, with roughly equal contributions from each mechanism. There is a larger cooling in the simulation using the A2 GHG scenario, but also enhanced loss from higher NOy and HOx concentrations, which nearly offsets the increase due to cooler temperatures. The resulting ozone evolutions are similar in the A2 and Alb simulations. The response of ozone due to feedbacks from temperature and HOx changes, related to changing halogen concentrations, are also quantified using simulations with fixed halogen concentrations.

  16. Nonlinear state feedback controller design for underactuated mechanical system: a modified block backstepping approach.

    Science.gov (United States)

    Rudra, Shubhobrata; Barai, Ranjit Kumar; Maitra, Madhubanti

    2014-03-01

    This paper presents the formulation of a novel block-backstepping based control algorithm to address the stabilization problem for a generalized nonlinear underactuated mechanical system. For the convenience of compact design, first, the state model of the underactuated system has been converted into the block-strict feedback form. Next, we have incorporated backstepping control action to derive the expression of the control input for the generic nonlinear underactuated system. The proposed block backstepping technique has further been enriched by incorporating an integral action additionally for enhancing the steady state performance of the overall system. Asymptotic stability of the overall system has been analyzed using Lyapunov stability criteria. Subsequently, the stability of the zero dynamics has also been analyzed to ensure the global asymptotic stability of the entire nonlinear system at its desired equilibrium point. The proposed control algorithm has been applied for the stabilization of a benchmarked underactuated mechanical system to verify the effectiveness of the proposed control law in real-time environment. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

  17. Understanding the differing governance of EU emissions trading and renewable: feedback mechanisms and policy entrepreneurs

    Energy Technology Data Exchange (ETDEWEB)

    Boasson, Elin Lerum; Wettestad, Joergen

    2010-04-15

    This paper presents a comparative study of two central EU climate policies: the revised Emissions Trading System (ETS), and the revised Renewable Energy Directive (RES). Both were originally developed in the early 2000s and revised policies were adopted in December 2008. While the ETS from 2013 on will have a quite centralized and market-streamlined design, the revised RES stands forward as a more decentralized and technology-focused policy. Differing institutional feed-back mechanisms and related roles of policy entrepreneurs can shed considerable light on these policy differences. Due to member states' cautiousness and contrary to the preferences of the Commission, the initial ETS was designed as a rather decentralized and 'politicized' market system, creating a malfunctioning institutional dynamic. In the revision process, the Commission skillfully highlighted this ineffective dynamic to win support for a much more centralized and market-streamlined approach. In the case of RES, national technology-specific support schemes and the strong links between the renewable industry and member states promoted the converse outcome: decentralization and technology development. Members of the European Parliament utilized these mechanisms through policy networking, while the Commission successfully used developments within the global climate regime to induce some degree of centralization. (Author)

  18. Gut feedback mechanisms and food intake: a physiological approach to slow carbohydrate bioavailability.

    Science.gov (United States)

    Zhang, Genyi; Hasek, Like Y; Lee, Byung-Hoo; Hamaker, Bruce R

    2015-04-01

    Glycemic carbohydrates in foods are an important macronutrient providing the biological fuel of glucose for a variety of physiological processes. A classification of glycemic carbohydrates into rapidly digestible carbohydrate (RDC) and slowly digestible carbohydrate (SDC) has been used to specify their nutritional quality related to glucose homeostasis that is essential to normal functioning of the brain and critical to life. Although there have been many studies and reviews on slowly digestible starch (SDS) and SDC, the mechanisms of their slow digestion and absorption were mostly investigated from the material side without considering the physiological processes of their in vivo digestion, absorption, and most importantly interactions with other food components and the gastrointestinal tract. In this article, the physiological processes modulating the bioavailability of carbohydrates, specifically the rate and extent of their digestion and absorption as well as the related locations, in a whole food context, will be discussed by focusing on the activities of the gastrointestinal tract including glycolytic enzymes and glucose release, sugar sensing, gut hormones, and neurohormonal negative feedback mechanisms. It is hoped that a deep understanding of these physiological processes will facilitate the development of innovative dietary approaches to achieve desired carbohydrate or glucose bioavailability for improved health.

  19. REDBACK: an Open-Source Highly Scalable Simulation Tool for Rock Mechanics with Dissipative Feedbacks

    Science.gov (United States)

    Poulet, T.; Veveakis, M.; Paesold, M.; Regenauer-Lieb, K.

    2014-12-01

    Multiphysics modelling has become an indispensable tool for geoscientists to simulate the complex behaviours observed in their various fields of study where multiple processes are involved, including thermal, hydraulic, mechanical and chemical (THMC) laws. This modelling activity involves simulations that are computationally expensive and its soaring uptake is tightly linked to the increasing availability of supercomputing power and easy access to powerful nonlinear solvers such as PETSc (http://www.mcs.anl.gov/petsc/). The Multiphysics Object-Oriented Simulation Environment (MOOSE) is a finite-element, multiphysics framework (http://mooseframework.org) that can harness such computational power and allow scientists to develop easily some tightly-coupled fully implicit multiphysics simulations that run automatically in parallel on large clusters. This open-source framework provides a powerful tool to collaborate on numerical modelling activities and we are contributing to its development with REDBACK (https://github.com/pou036/redback), a module for Rock mEchanics with Dissipative feedBACKs. REDBACK builds on the tensor mechanics finite strain implementation available in MOOSE to provide a THMC simulator where the energetic formulation highlights the importance of all dissipative terms in the coupled system of equations. We show first applications of fully coupled dehydration reactions triggering episodic fluid transfer through shear zones (Alevizos et al, 2014). The dimensionless approach used allows focusing on the critical underlying variables which are driving the resulting behaviours observed and this tool is specifically designed to study material instabilities underpinning geological features like faulting, folding, boudinage, shearing, fracturing, etc. REDBACK provides a collaborative and educational tool which captures the physical and mathematical understanding of such material instabilities and provides an easy way to apply this knowledge to realistic

  20. The actual structure of eBay’s feedback mechanism and early evidence on the effect of recent changes

    NARCIS (Netherlands)

    Klein, T.J.; Lambertz, C.; Spagnalo, G.; Stahl, K.O.

    2009-01-01

    eBay’s feedback mechanism is considered crucial to establishing and maintaining trust on the world’s largest trading platform. Yet, there is confusion among users about its exact institutional details, which changed substantially in May 2007. Most importantly, buyers now have the possibility to

  1. Oxidative stress in sepsis. Possible production of free radicals through an erythrocyte-mediated positive feedback mechanism

    Directory of Open Access Journals (Sweden)

    Yanaihara Pinchemel Amorim de Oliveira

    2017-01-01

    Conclusion: It was found that sepsis led to a high oxidative stress and to extensive modification of erythrocytes. It is proposed that a positive feedback mechanism, involving the activation of circulating leukocytes by these modified erythrocytes would maintain the pro-oxidative state even after the disappearance of bacteria.

  2. A Wearable-Based and Markerless Human-Manipulator Interface with Feedback Mechanism and Kalman Filters

    Directory of Open Access Journals (Sweden)

    Ping Zhang

    2015-11-01

    Full Text Available The objective of this paper is to develop a novel human-manipulator interface which incorporates wearable-based and markerless tracking to interact with the continuous movements of a human operator's hand. Unlike traditional approaches, which usually include contacting devices or physical markers to track the human-limb movements, this interface enables registration of natural movement through a wireless wearable watch and a leap motion sensor. Due to sensor error and tracking failure, the measurements are not made with sufficient accuracy. Two Kalman filters are employed to compensate the noisy and incomplete measurements in real time. Furthermore, due to perceptive limitations and abnormal state signals, the operator is unable to achieve high precision and efficiency in robot manipulation; an adaptive multispace transformation method (AMT is therefore introduced, which serves as a secondary treatment. In addition, in order to allow two-way human-robot interaction, the proposed method provides a vibration feedback mechanism triggered by the wearable watch to call the operator's attention to robot collision incidents or moments where the operator's hand is in a transboundary state. This improves teleoperation.

  3. Inflammation triggers emergency granulopoiesis through a density-dependent feedback mechanism.

    Directory of Open Access Journals (Sweden)

    Derek W Cain

    Full Text Available Normally, neutrophil pools are maintained by homeostatic mechanisms that require the transcription factor C/EBPα. Inflammation, however, induces neutrophilia through a distinct pathway of "emergency" granulopoiesis that is dependent on C/EBPβ. Here, we show in mice that alum triggers emergency granulopoiesis through the IL-1RI-dependent induction of G-CSF. G-CSF/G-CSF-R neutralization impairs proliferative responses of hematopoietic stem and progenitor cells (HSPC to alum, but also abrogates the acute mobilization of BM neutrophils, raising the possibility that HSPC responses to inflammation are an indirect result of the exhaustion of BM neutrophil stores. The induction of neutropenia, via depletion with Gr-1 mAb or myeloid-specific ablation of Mcl-1, elicits G-CSF via an IL-1RI-independent pathway, stimulating granulopoietic responses indistinguishable from those induced by adjuvant. Notably, C/EBPβ, thought to be necessary for enhanced generative capacity of BM, is dispensable for increased proliferation of HSPC to alum or neutropenia, but plays a role in terminal neutrophil differentiation during granulopoietic recovery. We conclude that alum elicits a transient increase in G-CSF production via IL-1RI for the mobilization of BM neutrophils, but density-dependent feedback sustains G-CSF for accelerated granulopoiesis.

  4. Explaining the Most Energetic Supernovae with an Inefficient Jet-feedback Mechanism

    Science.gov (United States)

    Gilkis, Avishai; Soker, Noam; Papish, Oded

    2016-08-01

    We suggest that the energetic radiation from core-collapse super-energetic supernovae (SESNe) is due to a long-lasting accretion process onto the newly born neutron star (NS), resulting from an inefficient operation of the jet-feedback mechanism (JFM). The jets that are launched by the accreting NS or black hole maintain their axis due to a rapidly rotating pre-collapse core and do not manage to eject core material from near the equatorial plane. The jets are able to eject material from the core along the polar directions and reduce the gravity near the equatorial plane. The equatorial gas expands, and part of it falls back over a timescale of minutes to days to prolong the jet-launching episode. According to the model for SESNe proposed in the present paper, the principal parameter that distinguishes between the different cases of core-collapse supernova (CCSN) explosions, such as between normal CCSNe and SESNe, is the efficiency of the JFM. This efficiency, in turn, depends on the pre-collapse core mass, envelope mass, core convection, and, most of all, the angular momentum profile in the core. One prediction of the inefficient JFM for SESNe is the formation of a slow equatorial outflow in the explosion. The typical velocity and mass of this outflow are estimated to be v eq ≈ 1000 km s-1 and M eq ≳ 1 M ⊙, respectively, though quantitative values will have to be checked in future hydrodynamic simulations.

  5. Predictable 'meta-mechanisms' emerge from feedbacks between transpiration and plant growth and cannot be simply deduced from short-term mechanisms.

    Science.gov (United States)

    Tardieu, François; Parent, Boris

    2017-06-01

    Growth under water deficit is controlled by short-term mechanisms but, because of numerous feedbacks, the combination of these mechanisms over time often results in outputs that cannot be deduced from the simple inspection of individual mechanisms. It can be analysed with dynamic models in which causal relationships between variables are considered at each time-step, allowing calculation of outputs that are routed back to inputs for the next time-step and that can change the system itself. We first review physiological mechanisms involved in seven feedbacks of transpiration on plant growth, involving changes in tissue hydraulic conductance, stomatal conductance, plant architecture and underlying factors such as hormones or aquaporins. The combination of these mechanisms over time can result in non-straightforward conclusions as shown by examples of simulation outputs: 'over production of abscisic acid (ABA) can cause a lower concentration of ABA in the xylem sap ', 'decreasing root hydraulic conductance when evaporative demand is maximum can improve plant performance' and 'rapid root growth can decrease yield'. Systems of equations simulating feedbacks over numerous time-steps result in logical and reproducible emergent properties that can be viewed as 'meta-mechanisms' at plant level, which have similar roles as mechanisms at cell level. © 2016 John Wiley & Sons Ltd.

  6. Land-Surface-Atmosphere Coupling in Observations and Models

    Directory of Open Access Journals (Sweden)

    Alan K Betts

    2009-07-01

    Full Text Available The diurnal cycle and the daily mean at the land-surface result from the coupling of many physical processes. The framework of this review is largely conceptual; looking for relationships and information in the coupling of processes in models and observations. Starting from the surface energy balance, the role of the surface and cloud albedos in the shortwave and longwave fluxes is discussed. A long-wave radiative scaling of the diurnal temperature range and the night-time boundary layer is summarized. Several aspects of the local surface energy partition are presented: the role of soilwater availability and clouds; vector methods for understanding mixed layer evolution, and the coupling between surface and boundary layer that determines the lifting condensation level. Moving to larger scales, evaporation-precipitation feedback in models is discussed; and the coupling of column water vapor, clouds and precipitation to vertical motion and moisture convergence over the Amazon. The final topic is a comparison of the ratio of surface shortwave cloud forcing to the diabatic precipitation forcing of the atmosphere in ERA-40 with observations.

  7. Real-time feedback on knee abduction moment does not improve frontal-plane knee mechanics during jump landings.

    Science.gov (United States)

    Beaulieu, M L; Palmieri-Smith, R M

    2014-08-01

    Excessive knee abduction loading is a contributing factor to anterior cruciate ligament (ACL) injury risk. The purpose of this study was to determine whether a double-leg landing training program with real-time visual feedback improves frontal-plane mechanics during double- and single-leg landings. Knee abduction angles and moments and vertical ground reaction forces (GRF) of 21 recreationally active women were quantified for double- and single-leg landings before and after the training program. This program consisted of two sessions of double-leg jump landings with real-time visual feedback on knee abduction moments for the experimental group and without real-time feedback for the control group. No significant differences were found between training groups. In comparison with pre-training data, peak knee abduction moments decreased 12% post-training for both double- and single-leg landings; whereas peak vertical GRF decreased 8% post-training for double-leg landings only, irrespective of training group. Real-time feedback on knee abduction moments, therefore, did not significantly improve frontal-plane knee mechanics during landings. The effect of the training program on knee abduction moments, however, transferred from the double-leg landings (simple task) to single-leg landings (more complex task). Consequently, ACL injury prevention efforts may not need to focus on complex tasks during which injury occurs. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Evaluation of fuel-temperature feedback mechanisms in TRAC-PF1/MOD2/NESTLE

    International Nuclear Information System (INIS)

    Knepper, Paula L.; Feltus, Madeline; Hochreiter, L.E.; Ivanov, Kostadin

    1999-01-01

    the code feedback mechanisms. (author)

  9. Appearance and Disappearance of Quantum Correlations in Measurement-Based Feedback Control of a Mechanical Oscillator

    Directory of Open Access Journals (Sweden)

    V. Sudhir

    2017-01-01

    Full Text Available Quantum correlations between imprecision and backaction are a hallmark of continuous linear measurements. Here, we study how measurement-based feedback can be used to improve the visibility of quantum correlations due to the interaction of a laser field with a nanomechanical oscillator. Backaction imparted by the meter laser, due to radiation-pressure quantum fluctuations, gives rise to correlations between its phase and amplitude quadratures. These quantum correlations are observed in the experiment both as squeezing of the meter field fluctuations below the vacuum level in a homodyne measurement and as sideband asymmetry in a heterodyne measurement, demonstrating the common origin of both phenomena. We show that quantum feedback, i.e., feedback that suppresses measurement backaction, can be used to increase the visibility of the sideband asymmetry ratio. In contrast, by operating the feedback loop in the regime of noise squashing, where the in-loop photocurrent variance is reduced below the vacuum level, the visibility of the sideband asymmetry is reduced. This is due to backaction arising from vacuum noise in the homodyne detector. These experiments demonstrate the possibility, as well as the fundamental limits, of measurement-based feedback as a tool to manipulate quantum correlations.

  10. PROSPECTIVE RANDOMIZED TRIAL ASSESSING THE IMPACT OF FEEDBACK MECHANISMS ON PATIENT POSITIONING.

    Science.gov (United States)

    Dimopoulos, Spyridon; Vivell, Julian; Ziemssen, Focke; Bende, Thomas; Bartz-Schmidt, Karl Ulrich; Leitritz, Martin Alexander

    2017-12-20

    To investigate the use of a head-fixed feedback sensor to improve good positioning times after macular hole or retinal detachment surgery. The instructional methods, macular hole closure rates, and questionnaire responses were also evaluated. After randomization, sensor devices with different feedback types (none/acoustic/vibration) were fixed on the patients' heads. Two positioning recommendations (verbal/illustrated) were used. The posturing data were logged every 500 ms for 24 hours. Forty-eight data sets (24 per group) were evaluated. Using sensory feedback, the median time for face-down positioning after macular hole surgery (Group 1) was significantly boosted from 463 minutes (range: 61-1,168) to 1,257 minutes (range: 1,024-1,327). The side positioning time after retinal detachment surgery (Group 2) increased from a median of 1,032 minutes (range: 520-1,165) to 1,284 minutes (range: 1,231-1,437). The night-time alarm records were reduced; however, the instructional methods exhibited no noteworthy effects. The questionnaires indicated positive acceptance of the sensors. Sensory feedback may help in cases where face-down or side positioning is recommended. These constant reminders were superior to verbal or written reminders; however, further studies are required to assess the clinical impact of sensory feedback on patient positioning.

  11. Follower-Centered Perspective on Feedback: Effects of Feedback Seeking on Identification and Feedback Environment

    OpenAIRE

    Gong, Zhenxing; Li, Miaomiao; Qi, Yaoyuan; Zhang, Na

    2017-01-01

    In the formation mechanism of the feedback environment, the existing research pays attention to external feedback sources and regards individuals as objects passively accepting feedback. Thus, the external source fails to realize the individuals’ need for feedback, and the feedback environment cannot provide them with useful information, leading to a feedback vacuum. The aim of this study is to examine the effect of feedback-seeking by different strategies on the supervisor-feedback environme...

  12. Synergy of feedback mechanisms in gene regulation systems with promoter and repressor transcription factors

    Czech Academy of Sciences Publication Activity Database

    Šrobár, Fedor

    2008-01-01

    Roč. 6, č. 1 (2008), s. 38-44 ISSN 1895-1082 Institutional research plan: CEZ:AV0Z20670512 Keywords : biophysics * feedback * signal flow graphs Subject RIV: BO - Biophysics Impact factor: 0.448, year: 2008

  13. Evaluating the negative or valuing the positive? Neural mechanisms supporting feedback-based learning across development

    NARCIS (Netherlands)

    van Duijvenvoorde, A.C.K.; Zanolie, K.; Rombouts, S.A.R.B.; Raijmakers, M.E.J.; Crone, E.A.

    2008-01-01

    Howchildren learn from positive and negative performance feedback lies at the foundation of successful learning and is therefore of great importance for educational practice. In this study, we used functional magnetic resonance imaging (fMRI) to examine the neural developmental changes related to

  14. Evaluating the negative or valuing the positive? Neural mechanisms supporting feedback-based learning across development

    NARCIS (Netherlands)

    A.C.K. van Duijvenvoorde (Anna C.); K. Zanolie (Kiki); S.A.R.B. Rombouts (Serge); M.E.J. Raijmakers (Maartje E.); E.A. Crone (Eveline)

    2008-01-01

    textabstractHow children learn from positive and negative performance feedback lies at the foundation of successful learning and is therefore of great importance for educational practice. In this study, we used functional magnetic resonance imaging (fMRI) to examine the neural developmental changes

  15. Surface-atmosphere decoupling limits accumulation at Summit, Greenland.

    Science.gov (United States)

    Berkelhammer, Max; Noone, David C; Steen-Larsen, Hans Christian; Bailey, Adriana; Cox, Christopher J; O'Neill, Michael S; Schneider, David; Steffen, Konrad; White, James W C

    2016-04-01

    Despite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland.

  16. Production mechanisms of leptons, photons, and hadrons and their possible feedback close to lightning leaders

    DEFF Research Database (Denmark)

    Köhn, Christoph; Diniz, Gabriel; Harakeh, Muhsin N.

    2017-01-01

    It has been discussed that lightning flashes emit high-energy electrons, positrons, photons,and neutrons with single energies of several tens of MeV. In the first part of this paper we study the absorption of neutron beams in the atmosphere. We initiate neutron beams of initial energies of 350 ke...... and m2 are possibly detectable at ground, at 6 km, or at 500 km altitude. In the second part of the paper we discuss a feedback model involving the generation and motion of electrons, positrons, neutrons, protons, and photons close to the vicinity of lightning leaders. In contrast to other feedback...... models, we do not consider large-scale thundercloud fields but enhanced fields of lightning leaders. We launch different photon and electron beams upward at 4 km altitude. We present the spatial and energy distribution of leptons, hadrons,and photons after different times and see that leptons, hadrons...

  17. Reciprocal Markov modeling of feedback mechanisms between emotion and dietary choice using experience sampling data

    OpenAIRE

    Lu, Ji; Pan, Junhao; Zhang, Qiang; Dubé, Laurette; Ip, Edward H.

    2015-01-01

    With intensively collected longitudinal data, recent advances in Experience Sampling Method (ESM) benefit social science empirical research, but also pose important methodological challenges. As traditional statistical models are not generally well-equipped to analyze a system of variables that contain feedback loops, this paper proposes the utility of an extended hidden Markov model to model reciprocal relationship between momentary emotion and eating behavior. This paper revisited an ESM da...

  18. CGILS: Results from the First Phase of an International Project to Understand the Physical Mechanisms of Low Cloud Feedbacks in Single Column Models

    Science.gov (United States)

    Zhang, Minghua; Bretherton, Christopher S.; Blossey, Peter N.; Austin, Phillip H.; Bacmeister, Julio T.; Bony, Sandrine; Brient, Florent; Cheedela, Suvarchal K.; Cheng, Anning; DelGenio, Anthony; hide

    2013-01-01

    1] CGILS-the CFMIP-GASS Intercomparison of Large Eddy Models (LESs) and single column models (SCMs)-investigates the mechanisms of cloud feedback in SCMs and LESs under idealized climate change perturbation. This paper describes the CGILS results from 15 SCMs and 8 LES models. Three cloud regimes over the subtropical oceans are studied: shallow cumulus, cumulus under stratocumulus, and well-mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated negative cloud feedbacks, while models with active shallow convection generally simulated positive cloud feedbacks. In the shallow cumulus alone regime, this relationship is less clear, likely due to the changes in cloud depth, lateral mixing, and precipitation or a combination of them. The majority of LES models simulated negative cloud feedback in the well-mixed coastal stratus/stratocumulus regime, and positive feedback in the shallow cumulus and stratocumulus regime. A general framework is provided to interpret SCM results: in a warmer climate, the moistening rate of the cloudy layer associated with the surface-based turbulence parameterization is enhanced; together with weaker large-scale subsidence, it causes negative cloud feedback. In contrast, in the warmer climate, the drying rate associated with the shallow convection scheme is enhanced. This causes positive cloud feedback. These mechanisms are summarized as the "NESTS" negative cloud feedback and the "SCOPE" positive cloud feedback (Negative feedback from Surface Turbulence under weaker Subsidence-Shallow Convection PositivE feedback) with the net cloud feedback depending on how the two opposing effects counteract each other. The LES results are consistent with these interpretations

  19. Flexible switching of feedback control mechanisms allows for learning of different task dynamics.

    Science.gov (United States)

    White, Olivier; Diedrichsen, Jörn

    2013-01-01

    To produce skilled movements, the brain flexibly adapts to different task requirements and movement contexts. Two core abilities underlie this flexibility. First, depending on the task, the motor system must rapidly switch the way it produces motor commands and how it corrects movements online, i.e. it switches between different (feedback) control policies. Second, it must also adapt to environmental changes for different tasks separately. Here we show these two abilities are related. In a bimanual movement task, we show that participants can switch on a movement-by-movement basis between two feedback control policies, depending only on a static visual cue. When this cue indicates that the hands control separate objects, reactions to force field perturbations of each arm are purely unilateral. In contrast, when the visual cue indicates a commonly controlled object, reactions are shared across hands. Participants are also able to learn different force fields associated with a visual cue. This is however only the case when the visual cue is associated with different feedback control policies. These results indicate that when the motor system can flexibly switch between different control policies, it is also able to adapt separately to the dynamics of different environmental contexts. In contrast, visual cues that are not associated with different control policies are not effective for learning different task dynamics.

  20. Modal space three-state feedback control for electro-hydraulic servo plane redundant driving mechanism with eccentric load decoupling.

    Science.gov (United States)

    Zhao, Jinsong; Wang, Zhipeng; Zhang, Chuanbi; Yang, Chifu; Bai, Wenjie; Zhao, Zining

    2018-04-13

    The shaking table based on electro-hydraulic servo parallel mechanism has the advantage of strong carrying capacity. However, the strong coupling caused by the eccentric load not only affects the degree of freedom space control precision, but also brings trouble to the system control. A novel decoupling control strategy is proposed, which is based on modal space to solve the coupling problem for parallel mechanism with eccentric load. The phenomenon of strong dynamic coupling among degree of freedom space is described by experiments, and its influence on control design is discussed. Considering the particularity of plane motion, the dynamic model is built by Lagrangian method to avoid complex calculations. The dynamic equations of the coupling physical space are transformed into the dynamic equations of the decoupling modal space by using the weighted orthogonality of the modal main mode with respect to mass matrix and stiffness matrix. In the modal space, the adjustments of the modal channels are independent of each other. Moreover, the paper discusses identical closed-loop dynamic characteristics of modal channels, which will realize decoupling for degree of freedom space, thus a modal space three-state feedback control is proposed to expand the frequency bandwidth of each modal channel for ensuring their near-identical responses in a larger frequency range. Experimental results show that the concept of modal space three-state feedback control proposed in this paper can effectively reduce the strong coupling problem of degree of freedom space channels, which verify the effectiveness of the proposed model space state feedback control strategy for improving the control performance of the electro-hydraulic servo plane redundant driving mechanism. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

  1. Characterization of the dominant structural vibration of hearing aid receivers: Towards the moderation of mechanical feedback in hearing aids

    Science.gov (United States)

    Varanda, Brenno R.

    Presented are the results from the experimental, analytical, and computational analyses accomplished to characterize the mechanical vibration of hearing aid receivers, a key electro-acoustic component of hearing aids. The function of a receiver in a hearing aid is to provide an amplified sound signal into the ear canal. Unfortunately, as the receiver produces sound, it also undergoes vibration which can be transmitted through the hearing aid package to the microphones, resulting in undesirable feedback oscillations. To gain more knowledge and control on the source of these feedback oscillations, a dynamic rigid body model of the receiver is proposed. The rigid body model captures the essential dynamic features of the receiver. The model is represented by two hinged rigid bodies, under an equal and opposite dynamic moment load, and connected to each other by a torsional spring and damper. The mechanical coupling ratio between the two rigid bodies is proved to be acoustically independent. A method is introduced to estimate the parameters for the proposed model using experimental data. An equivalent finite element analysis model is established and tested against a known and characterized mechanical attachment. The simulated model successfully predicts the structural dynamic response showing excellent agreement between the finite element analysis and measured results.

  2. Mechanism of phytohormone involvement in feedback regulation of cotton leaf senescence induced by potassium deficiency.

    Science.gov (United States)

    Wang, Ye; Li, Bo; Du, Mingwei; Eneji, A Egrinya; Wang, Baomin; Duan, Liusheng; Li, Zhaohu; Tian, Xiaoli

    2012-10-01

    To elucidate the phytohormonal basis of the feedback regulation of leaf senescence induced by potassium (K) deficiency in cotton (Gossypium hirsutum L.), two cultivars contrasting in sensitivity to K deficiency were self- and reciprocally grafted hypocotyl-to-hypocotyl, using standard grafting (one scion grafted onto one rootstock), Y grafting (two scions grafted onto one rootstock), and inverted Y grafting (one scion grafted onto two rootstocks) at the seedling stage. K deficiency (0.03mM for standard and Y grafting, and 0.01mM for inverted Y grafting) increased the root abscisic acid (ABA) concentration by 1.6- to 3.1-fold and xylem ABA delivery rates by 1.8- to 4.6-fold. The K deficiency also decreased the delivery rates of xylem cytokinins [CKs; including the zeatin riboside (ZR) and isopentenyl adenosine (iPA) type] by 29-65% and leaf CK concentration by 16-57%. The leaf ABA concentration and xylem ABA deliveries were consistently greater in CCRI41 (more sensitive to K deficiency) than in SCRC22 (less sensitive to K deficiency) scions under K deficiency, and ZR- and iPA-type levels were consistently lower in the former than in the latter, irrespective of rootstock cultivar or grafting type, indicating that cotton shoot influences the levels of ABA and CKs in leaves and xylem sap. Because the scions had little influence on phytohormone levels in the roots (rootstocks) of all three types of grafts and rootstock xylem sap (collected below the graft union) of Y and inverted Y grafts, it appears that the site for basipetal feedback signal(s) involved in the regulation of xylem phytohormones is the hypocotyl of cotton seedlings. Also, the target of this feedback signal(s) is more likely to be the changes in xylem phytohormones within tissues of the hypocotyl rather than the export of phytohormones from the roots.

  3. Geo-ecology of surface atmosphere of Tomsk and methodology for the ecological risk calculation

    Science.gov (United States)

    Ivanova, E. V.; Anisimov, M. V.; Kuznetsova, U. N.; Taldonova, N. V.; Petrova, A. V.

    2018-01-01

    The present study presents new methodological approach of environmental assessment of surface atmosphere layer based on principles of non equilibrium dynamics. The role of natural and technogenic factors in forming areas of dust and airborne pollution is determined. The results of the study of ecological risk from atmosphere chemical pollution of the town are presented.

  4. Reciprocal Markov Modeling of Feedback Mechanisms Between Emotion and Dietary Choice Using Experience-Sampling Data.

    Science.gov (United States)

    Lu, Ji; Pan, Junhao; Zhang, Qiang; Dubé, Laurette; Ip, Edward H

    2015-01-01

    With intensively collected longitudinal data, recent advances in the experience-sampling method (ESM) benefit social science empirical research, but also pose important methodological challenges. As traditional statistical models are not generally well equipped to analyze a system of variables that contain feedback loops, this paper proposes the utility of an extended hidden Markov model to model reciprocal the relationship between momentary emotion and eating behavior. This paper revisited an ESM data set (Lu, Huet, & Dube, 2011) that observed 160 participants' food consumption and momentary emotions 6 times per day in 10 days. Focusing on the analyses on feedback loop between mood and meal-healthiness decision, the proposed reciprocal Markov model (RMM) can accommodate both hidden ("general" emotional states: positive vs. negative state) and observed states (meal: healthier, same or less healthy than usual) without presuming independence between observations and smooth trajectories of mood or behavior changes. The results of RMM analyses illustrated the reciprocal chains of meal consumption and mood as well as the effect of contextual factors that moderate the interrelationship between eating and emotion. A simulation experiment that generated data consistent with the empirical study further demonstrated that the procedure is promising in terms of recovering the parameters.

  5. External chest compressions using a mechanical feedback device : cross-over simulation study.

    Science.gov (United States)

    Skorning, M; Derwall, M; Brokmann, J C; Rörtgen, D; Bergrath, S; Pflipsen, J; Beuerlein, S; Rossaint, R; Beckers, S K

    2011-08-01

    External chest compressions (ECC) are essential components of resuscitation and are usually performed without any adjuncts in professional healthcare. Even for healthcare professionals during in-hospital and out-of-hospital resuscitation poor performance in ECC has been reported in recent years. Although several stand-alone devices have been developed none has been implemented as a standard in patient care. The aim of this study was to examine if the use of a mechanical device providing visual feedback and audible assistance during ECC improves performance of healthcare professionals following minimal and simplified instructions. In a prospective, randomized cross-over study 81 healthcare professionals performed ECC for 3 min (in the assumed setting of a secured airway) twice on a manikin (Skillreporter ResusciAnne®, with PC-Skillreporting System Version 1.3.0, Laerdal, Stavanger, Norway) in a mock cardiac arrest scenario. Group 1 (n=40) performed ECC with the device first followed by classic ECC and group 2 (n=41) in the opposite order. Minimal instructions were standardized and provided by video instruction (1 min 38 s). Endpoints were achievement of a mean compression rate between 90 and 110/min and a mean compression depth of 40-50 mm. In addition participants had to answer questionnaires about demographic data, professional experience and recent recommendations for ECC as well as their impression of the device concerning the ease of use and their personal level of confidence. Data were analyzed for group-related and inter-group differences using SAS (Version 9.1.3, SAS Institute, Cary, NC). A total of 81 healthcare professionals regularly involved in resuscitation attempts in pre-hospital or in-hospital settings took part in the study with no differences between the groups: females 35.8% (n=52), emergency medical technicians 32.1% (n=26), anesthesia nurses 32.1% (n=26), physicians (anesthesiology) 45% (n=29). In group 1 33 out of 40 (82.5%; 99.7±4

  6. Output feedback control of heat transport mechanisms in parabolic distributed solar collectors

    KAUST Repository

    Elmetennani, Shahrazed

    2016-08-05

    This paper presents an output feedback control for distributed parabolic solar collectors. The controller aims at forcing the outlet temperature to track a desired reference in order to manage the produced heat despite the external disturbances. The proposed control strategy is derived using the distributed physical model of the system to avoid the loss of information due to model approximation schemes. The system dynamics are driven to follow reference dynamics defined by a transport equation with a constant velocity, which allows to control the transient behavior and the response time of the closed loop. The designed controller depends only on the accessible measured variables which makes it easy for real time implementation and useful for industrial plants. Simulation results show the efficiency of the reference tracking closed loop under different working conditions.

  7. Effects of feedback reliability on feedback-related brain activity: A feedback valuation account.

    Science.gov (United States)

    Ernst, Benjamin; Steinhauser, Marco

    2018-04-06

    Adaptive decision making relies on learning from feedback. Because feedback sometimes can be misleading, optimal learning requires that knowledge about the feedback's reliability be utilized to adjust feedback processing. Although previous research has shown that feedback reliability indeed influences feedback processing, the underlying mechanisms through which this is accomplished remain unclear. Here we propose that feedback processing is adjusted by the adaptive, top-down valuation of feedback. We assume that unreliable feedback is devalued relative to reliable feedback, thus reducing the reward prediction errors that underlie feedback-related brain activity and learning. A crucial prediction of this account is that the effects of feedback reliability are susceptible to contrast effects. That is, the effects of feedback reliability should be enhanced when both reliable and unreliable feedback are experienced within the same context, as compared to when only one level of feedback reliability is experienced. To evaluate this prediction, we measured the event-related potentials elicited by feedback in two experiments in which feedback reliability was varied either within or between blocks. We found that the fronto-central valence effect, a correlate of reward prediction errors during reinforcement learning, was reduced for unreliable feedback. But this result was obtained only when feedback reliability was varied within blocks, thus indicating a contrast effect. This suggests that the adaptive valuation of feedback is one mechanism underlying the effects of feedback reliability on feedback processing.

  8. Audio Feedback -- Better Feedback?

    Science.gov (United States)

    Voelkel, Susanne; Mello, Luciane V.

    2014-01-01

    National Student Survey (NSS) results show that many students are dissatisfied with the amount and quality of feedback they get for their work. This study reports on two case studies in which we tried to address these issues by introducing audio feedback to one undergraduate (UG) and one postgraduate (PG) class, respectively. In case study one…

  9. Biogeomorphic feedbacks in the Southwestern USA: exploring the mechanisms of geomorphic change and the effectiveness of mitigation measures

    Science.gov (United States)

    Dean, D. J.; Diehl, R. M.; Topping, D. J.

    2017-12-01

    Water development and the proliferation of riparian plants have resulted in extensive geomorphic change to rivers worldwide. In many dryland rivers of the Southwestern U.S., these phenomena have contributed to conditions of sediment accumulation leading to channel narrowing, floodplain aggradation, and loss of fluvial habitat. Using a series of field and laboratory measurements, we demonstrate how biogeomorphic feedbacks have promoted channel contraction. Experimental evidence shows that vegetation can have a substantial effect on local hydraulics and sediment-transport fields, depending on plant morphology, but that the impact of plants on physical processes is mediated by flow and sediment supply. In the Little Colorado River in Arizona, water management practices, variations in climate/hydrology, and the resultant expansion of riparian vegetation have resulted in channel narrowing, increases in sinuosity and drag, and decreases in channel slope. These changes have created a biogeomorphic feedback by disrupting downstream flood conveyance; flood travel time has increased resulting in flow attenuation, declines in peak discharge, and continued sediment accumulation at large scales. In the Rio Grande in Big Bend National Park, channel narrowing and floodplain aggradation has led to the loss of channel capacity and an increase in overbank flooding even though discharges have declined. Vegetation expansion into channel environments has exacerbated this condition by reducing channel-margin flow velocities, increasing sediment deposition, and reducing bank erosion thereby creating a biogeomorphic feedback leading to additional narrowing. An understanding of the mechanisms that have driven geomorphic changes in river channels may help to formulate effective mitigation measures. Vegetation removal can have local and reach-scale effects on channel morphology; however, the effectiveness of these actions is dependent upon many variables including the flow regime and

  10. On the track of syncope induced by orthostatic stress - feedback mechanisms regulating the cardiovascular system

    DEFF Research Database (Denmark)

    Ottesen, Johnny T.

    2009-01-01

    A physiological realistic model of the controlled cardiovascular system is constructed and validated against clinical data. Special attention is paid to the heart rate control. Both sit-to-stand and head-up-tilt experiments are encapsulated by the model. The model may be used in studies of syncop....... Furthermore, the impact of the mechanical movement of diaphragm driving the respiration is considered. It turns out that this mechanical effect is significant....

  11. CGILS: Results from the First Phase of an International Project to Understand the Physical Mechanisms of Low Cloud Feedbacks in Single Column Models

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Minghua; Bretherton, Christopher S.; Blossey, Peter; Austin, Phillip A.; Bacmeister, J.; Bony, Sandrine; Brient, Florent; Cheedela, Suvarchal K.; Cheng, Anning; Del Genio, Anthony D.; De Roode, Stephan R.; Endo , Satoshi; Franklin, Charmaine N.; Golaz, Jean-Christophe; Hannay, Cecile; Heus, Thijs; Isotta, Francesco A.; Jean-Louis, Dufresne; Kang, In-Sik; Kawai, Hideaki; Koehler, M.; Larson, Vincent E.; Liu, Yangang; Lock, Adrian; Lohmann, U.; Khairoutdinov, Marat; Molod, Andrea M.; Neggers, Roel; Rasch, Philip J.; Sandu, Irina; Senkbeil, Ryan; Siebesma, A. P.; Siegenthaler-Le Drian, Colombe; Stevens, Bjorn; Suarez, Max; Xu, Kuan-Man; Von Salzen, Knut; Webb, Mark; Wolf, Audrey; Zhao, M.

    2013-12-26

    Large Eddy Models (LES) and Single Column Models (SCM) are used in a surrogate climate change 101 to investigate the physical mechanism of low cloud feedbacks in climate models. Enhanced surface-102 driven boundary layer turbulence and shallow convection in a warmer climate are found to be 103 dominant mechanisms in SCMs.

  12. Studying citizen science through adaptive management and learning feedbacks as mechanisms for improving conservation.

    Science.gov (United States)

    Jordan, Rebecca; Gray, Steven; Sorensen, Amanda; Newman, Greg; Mellor, David; Newman, Greg; Hmelo-Silver, Cindy; LaDeau, Shannon; Biehler, Dawn; Crall, Alycia

    2016-06-01

    Citizen science has generated a growing interest among scientists and community groups, and citizen science programs have been created specifically for conservation. We examined collaborative science, a highly interactive form of citizen science, which we developed within a theoretically informed framework. In this essay, we focused on 2 aspects of our framework: social learning and adaptive management. Social learning, in contrast to individual-based learning, stresses collaborative and generative insight making and is well-suited for adaptive management. Adaptive-management integrates feedback loops that are informed by what is learned and is guided by iterative decision making. Participants engaged in citizen science are able to add to what they are learning through primary data collection, which can result in the real-time information that is often necessary for conservation. Our work is particularly timely because research publications consistently report a lack of established frameworks and evaluation plans to address the extent of conservation outcomes in citizen science. To illustrate how our framework supports conservation through citizen science, we examined how 2 programs enacted our collaborative science framework. Further, we inspected preliminary conservation outcomes of our case-study programs. These programs, despite their recent implementation, are demonstrating promise with regard to positive conservation outcomes. To date, they are independently earning funds to support research, earning buy-in from local partners to engage in experimentation, and, in the absence of leading scientists, are collecting data to test ideas. We argue that this success is due to citizen scientists being organized around local issues and engaging in iterative, collaborative, and adaptive learning. © 2016 Society for Conservation Biology.

  13. Feedback and education improve physician compliance in use of lung-protective mechanical ventilation

    NARCIS (Netherlands)

    Wolthuis, Esther K.; Korevaar, Johanna C.; Spronk, Peter; Kuiper, Michael A.; Dzoljic, Misa; Vroom, Margreeth B.; Schultz, Marcus J.

    2005-01-01

    Objective: Use of lung-protective mechanical ventilation (MV) by applying lower tidal volumes is recommended in patients suffering from acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Recent data suggest that lung-protective MV may benefit non-ALI/ARDS patients as well. This

  14. On the contribution of local feedback mechanisms to the range of climate sensitivity in two GCM ensembles

    Energy Technology Data Exchange (ETDEWEB)

    Webb, M.J.; Senior, C.A.; Sexton, D.M.H.; Ingram, W.J.; Williams, K.D.; Ringer, M.A. [Hadley Centre for Climate Prediction and Research, Met Office, Exeter (United Kingdom); McAvaney, B.J.; Colman, R. [Bureau of Meteorology Research Centre (BMRC), Melbourne (Australia); Soden, B.J. [University of Miami, Rosenstiel School for Marine and Atmospheric Science, Miami, FL (United States); Gudgel, R.; Knutson, T. [Geophysical Fluid Dynamics Laboratory (GFDL), Princeton, NJ (United States); Emori, S.; Ogura, T. [National Institute for Environmental Studies (NIES), Tsukuba (Japan); Tsushima, Y. [Japan Agency for Marine-Earth Science and Technology, Frontier Research Center for Global Change (FRCGC), Kanagawa (Japan); Andronova, N. [University of Michigan, Department of Atmospheric, Oceanic and Space Sciences, Ann Arbor, MI (United States); Li, B. [University of Illinois at Urbana-Champaign (UIUC), Department of Atmospheric Sciences, Urbana, IL (United States); Musat, I.; Bony, S. [Institut Pierre Simon Laplace (IPSL), Paris (France); Taylor, K.E. [Program for Climate Model Diagnosis and Intercomparison (PCMDI), Livermore, CA (United States)

    2006-07-15

    Global and local feedback analysis techniques have been applied to two ensembles of mixed layer equilibrium CO{sub 2} doubling climate change experiments, from the CFMIP (Cloud Feedback Model Intercomparison Project) and QUMP (Quantifying Uncertainty in Model Predictions) projects. Neither of these new ensembles shows evidence of a statistically significant change in the ensemble mean or variance in global mean climate sensitivity when compared with the results from the mixed layer models quoted in the Third Assessment Report of the IPCC. Global mean feedback analysis of these two ensembles confirms the large contribution made by inter-model differences in cloud feedbacks to those in climate sensitivity in earlier studies; net cloud feedbacks are responsible for 66% of the inter-model variance in the total feedback in the CFMIP ensemble and 85% in the QUMP ensemble. The ensemble mean global feedback components are all statistically indistinguishable between the two ensembles, except for the clear-sky shortwave feedback which is stronger in the CFMIP ensemble. While ensemble variances of the shortwave cloud feedback and both clear-sky feedback terms are larger in CFMIP, there is considerable overlap in the cloud feedback ranges; QUMP spans 80% or more of the CFMIP ranges in longwave and shortwave cloud feedback. We introduce a local cloud feedback classification system which distinguishes different types of cloud feedbacks on the basis of the relative strengths of their longwave and shortwave components, and interpret these in terms of responses of different cloud types diagnosed by the International Satellite Cloud Climatology Project simulator. In the CFMIP ensemble, areas where low-top cloud changes constitute the largest cloud response are responsible for 59% of the contribution from cloud feedback to the variance in the total feedback. A similar figure is found for the QUMP ensemble. Areas of positive low cloud feedback (associated with reductions in low level

  15. The vicious cycle towards violence: focus on the negative feedback mechanisms of brain serotonin neurotransmission

    Directory of Open Access Journals (Sweden)

    Sietse De Boer

    2009-11-01

    Full Text Available Violence can be defined as a form of escalated aggressive behavior that is expressed out of context and out of inhibitory control, and apparently has lost its adaptive function in social communication. Little is known about the social and environmental factors as well as the underlying neurobiological mechanisms involved in the shift of normal adaptive aggression into violence. In an effort to model the harmful acts of aggression and violence in humans, we recently (redeveloped an animal model that is focused on engendering uncontrolled forms of maladaptive aggressive behavior in laboratory-bred feral rats and mice. We show that certain (8-12% constitutionally aggressive individuals gradually develop, over the course of repetitive exposures to victorious social conflicts, escalated (short-latency, high-frequency and ferocious attacks, persistent (lack of attack inhibition by defeat/submission signals and perseverance of the aggressive attack-biting bout, indiscriminating (attacking female and anesthetized male intruders and injurious (enhanced vulnerable-body region attacks and inflicted wounding forms of offensive aggression. Based on the neurobiological results obtained using this model, a revised view is presented on the key role of central serotonergic (autoregulatory mechanisms in this transition of normal aggression into violence.

  16. The vicious cycle towards violence: focus on the negative feedback mechanisms of brain serotonin neurotransmission.

    Science.gov (United States)

    de Boer, Sietse F; Caramaschi, Doretta; Natarajan, Deepa; Koolhaas, Jaap M

    2009-01-01

    Violence can be defined as a form of escalated aggressive behavior that is expressed out of context and out of inhibitory control, and apparently has lost its adaptive function in social communication. Little is known about the social and environmental factors as well as the underlying neurobiological mechanisms involved in the shift of normal adaptive aggression into violence. In an effort to model the harmful acts of aggression and violence in humans, we recently (re)developed an animal model that is focused on engendering uncontrolled forms of maladaptive aggressive behavior in laboratory-bred feral rats and mice. We show that certain (8-12%) constitutionally aggressive individuals gradually develop, over the course of repetitive exposures to victorious social conflicts, escalated (short-latency, high-frequency and ferocious attacks), persistent (lack of attack inhibition by defeat/submission signals and perseverance of the aggressive attack-biting bout), indiscriminating (attacking female and anesthetized male intruders) and injurious (enhanced vulnerable-body region attacks and inflicted wounding) forms of offensive aggression. Based on the neurobiological results obtained using this model, a revised view is presented on the key role of central serotonergic (auto)regulatory mechanisms in this transition of normal aggression into violence.

  17. Spatially explicit simulation of hydrologically controlled carbon and nitrogen cycles and associated feedback mechanisms in a boreal ecosystem

    Science.gov (United States)

    Govind, Ajit; Chen, Jing Ming; Ju, Weimin

    2009-06-01

    Ecosystem models that simulate biogeochemical processes usually ignore hydrological controls that govern them. It is quite possible that topographically driven water fluxes significantly influence the spatial distribution of C sources and sinks because of their large contribution to the local water balance. To investigate this, we simulated biogeochemical processes along with the associated feedback mechanisms in a boreal ecosystem using a spatially explicit hydroecological model, boreal ecosystem productivity simulator (BEPS)-TerrainLab V2.0, that has a tight coupling of ecophysiological, hydrological, and biogeochemical processes. First, the simulated dynamics of snowpack, soil temperature, net ecosystem productivity (NEP), and total ecosystem respiration (TER) were validated with high-frequency measurements for 2 years. The model was able to explain 80% of the variability in NEP and 84% of the variability in TER. Further, we investigated the influence of topographically driven subsurface base flow on soil C and N cycling and on the spatiotemporal patterns of C sources and sinks using three hydrological modeling scenarios that differed in hydrological conceptualizations. In general, the scenarios that had nonexplicit hydrological representation overestimated NEP, as opposed to the scenario that had an explicit (realistic) representation. The key processes controlling the NEP differences were attributed to the combined effects of variations in photosynthesis (due to changes in stomatal conductance and nitrogen (N) availability), heterotrophic respiration, and autotrophic respiration, all of which occur simultaneously affecting NEP. Feedback relationships were also found to exacerbate the differences. We identified six types of NEP differences (biases), of which the most commonly found was due to an underestimation of the existing C sources, highlighting the vulnerability of regional-scale ecosystem models that ignore hydrological processes.

  18. Depletion of retinoic acid receptors initiates a novel positive feedback mechanism that promotes teratogenic increases in retinoic acid.

    Directory of Open Access Journals (Sweden)

    Enrico D'Aniello

    Full Text Available Normal embryonic development and tissue homeostasis require precise levels of retinoic acid (RA signaling. Despite the importance of appropriate embryonic RA signaling levels, the mechanisms underlying congenital defects due to perturbations of RA signaling are not completely understood. Here, we report that zebrafish embryos deficient for RA receptor αb1 (RARαb1, a conserved RAR splice variant, have enlarged hearts with increased cardiomyocyte (CM specification, which are surprisingly the consequence of increased RA signaling. Importantly, depletion of RARαb2 or concurrent depletion of RARαb1 and RARαb2 also results in increased RA signaling, suggesting this effect is a broader consequence of RAR depletion. Concurrent depletion of RARαb1 and Cyp26a1, an enzyme that facilitates degradation of RA, and employment of a novel transgenic RA sensor line support the hypothesis that the increases in RA signaling in RAR deficient embryos are the result of increased embryonic RA coupled with compensatory RAR expression. Our results support an intriguing novel mechanism by which depletion of RARs elicits a previously unrecognized positive feedback loop that can result in developmental defects due to teratogenic increases in embryonic RA.

  19. Radio Tomography of Ionospheric Structures (probably) due to Underground-Surface-Atmosphere-Ionosphere Coupling

    Science.gov (United States)

    Kunitsyn, V.; Nesterov, I.; Andreeva, E.; Rekenthaler, D. A.

    2012-12-01

    Ionospheric radio-tomography (RT) utilizes radio signals transmitted from the global navigational satellite systems (GNSS), including low-orbiting (LO) navigational systems such as Transit, Tsikada, etc., and high-orbiting (HO) navigational systems such as GPS, GLONASS, Galileo, Beidou, etc. The signals that are transmitted from the LO navigational satellites and recorded by ground receiving chains can be inverted for almost instantaneous (5-8 min) 2D snapshots of electron density. The data from the networks of ground receivers that record the signals of the HO satellites are suitable for implementing high-orbital RT (HORT), i.e. reconstructing the 4D distributions of the ionospheric electron density (one 3D image every 20-30 min). In the regions densely covered by the GNSS receivers, it is currently possible to get a time step of 2-4 min. The LORT and HORT approaches have a common methodical basis: in both these techniques, the integrals of electron density along the ray between the satellite and the receiver are measured, and then the tomographic procedures are applied to reconstruct the distributions of electron density. We present several examples of the experiments on the ionospheric RT, which are related to the Underground-Surface-Atmosphere-Ionosphere (USAI) coupling. In particular, we demonstrate examples of RT images of the ionosphere after industrial explosions, rocket launches, and modification of the ionosphere by high-power radio waves. We also show RT cross sections reflecting ionospheric disturbances caused by the earthquakes (EQ) and tsunami waves. In these cases, there is an evident cause-and-effect relationship. The perturbations are transferred between the geospheres predominantly by acoustic gravity waves (AGW), whose amplitudes increase with increasing height. As far as EQ are concerned, the cause of the USAI coupling mechanism is not obvious. It is clear, however, that the regular RT studies can promote the solution of this challenging problem

  20. Feedback mechanisms of change: How problem alerts reported by youth clients and their caregivers impact clinician-reported session content

    Science.gov (United States)

    Douglas, Susan R.; Jonghyuk, Bae; de Andrade, Ana Regina Vides; Tomlinson, M. Michele; Hargraves, Ryan Pamela; Bickman, Leonard

    2015-01-01

    Objective This study explored how clinician-reported content addressed in treatment sessions was predicted by clinician feedback group and multi-informant cumulative problem alerts that appeared in computerized feedback reports for 299 clients aged 11 to 18 years receiving home-based community mental health treatment. Method Measures included a clinician-report of content addressed in sessions and additional measures of treatment progress and process (e.g., therapeutic alliance) completed by clinicians, clients, and their caregivers. Item responses in the top 25th percentile in severity from these measures appeared as ‘problem alerts’ on corresponding computerized feedback reports. Clinicians randomized to the feedback group received feedback weekly while the control group did not. Analyses were conducted using the Cox proportional hazards regression for recurrent events. Results For all content domains, the results of the survival analyses indicated a robust effect of the feedback group on addressing specific content in sessions, with feedback associated with shorter duration to first occurrence and increased likelihood of addressing or focusing on a topic compared to the non-feedback group. Conclusion There appears to be an important relationship between feedback and cumulative problem alerts reported by multiple informants as they influence session content. PMID:26337327

  1. Feedback Conversations: Creating Feedback Dialogues with a New Textual Tool for Industrial Design Student Feedback

    Science.gov (United States)

    Funk, Mathias; van Diggelen, Migchiel

    2017-01-01

    In this paper, the authors describe how a study of a large database of written university teacher feedback in the department of Industrial Design led to the development of a new conceptual framework for feedback and the design of a new feedback tool. This paper focuses on the translation of related work in the area of feedback mechanisms for…

  2. Leukemia Mediated Endothelial Cell Activation Modulates Leukemia Cell Susceptibility to Chemotherapy through a Positive Feedback Loop Mechanism.

    Directory of Open Access Journals (Sweden)

    Bahareh Pezeshkian

    Full Text Available In acute myeloid leukemia (AML, the chances of achieving disease-free survival are low. Studies have demonstrated a supportive role of endothelial cells (ECs in normal hematopoiesis. Here we show that similar intercellular relationships exist in leukemia. We demonstrate that leukemia cells themselves initiate these interactions by directly modulating the behavior of resting ECs through the induction of EC activation. In this inflammatory state, activated ECs induce the adhesion of a sub-set of leukemia cells through the cell adhesion molecule E-selectin. These adherent leukemia cells are sequestered in a quiescent state and are unaffected by chemotherapy. The ability of adherent cells to later detach and again become proliferative following exposure to chemotherapy suggests a role of this process in relapse. Interestingly, differing leukemia subtypes modulate this process to varying degrees, which may explain the varied response of AML patients to chemotherapy and relapse rates. Finally, because leukemia cells themselves induce EC activation, we postulate a positive-feedback loop in leukemia that exists to support the growth and relapse of the disease. Together, the data defines a new mechanism describing how ECs and leukemia cells interact during leukemogenesis, which could be used to develop novel treatments for those with AML.

  3. Neural cryptography with feedback.

    Science.gov (United States)

    Ruttor, Andreas; Kinzel, Wolfgang; Shacham, Lanir; Kanter, Ido

    2004-04-01

    Neural cryptography is based on a competition between attractive and repulsive stochastic forces. A feedback mechanism is added to neural cryptography which increases the repulsive forces. Using numerical simulations and an analytic approach, the probability of a successful attack is calculated for different model parameters. Scaling laws are derived which show that feedback improves the security of the system. In addition, a network with feedback generates a pseudorandom bit sequence which can be used to encrypt and decrypt a secret message.

  4. Giving feedback.

    Science.gov (United States)

    Thomas, Jane DeLima; Arnold, Robert M

    2011-02-01

    Giving feedback is a core element of medical education, one that is gaining attention but with a thin evidence base to guide medical educators. This review provides a definition of feedback and its purpose, selectively reviews the literature regarding educators' and learners' attitudes toward feedback, and provides an algorithm for giving feedback. The authors discuss the parallels between giving feedback and breaking bad news, emphasizing the importance of titrating the amount of information given, attending to affect, and making a plan for next steps. Special considerations for giving feedback in palliative care are highlighted, including the effect of heightened emotion in the clinical encounter and the difficulties of giving feedback about communication skills.

  5. Situated Formative Feedback

    DEFF Research Database (Denmark)

    Lukassen, Niels Bech; Wahl, Christian; Sorensen, Elsebeth Korsgaard

    This study addresses the conceptual challenge of providing students with good quality feedback to enhance student learning in an online community of practice (COP). The aim of the study is to identify feedback mechanisms in a virtual learning environment (VLE) and to create a full formative...... refer to this type of feedback as, Situated Formative Feedback (SFF). As a basis for exploring, identifying and discussing relevant aspects of SFF the paper analyses qualitative data from a Moodle dialogue. Data are embedded in the qualitative analytic program Nvivo and are analysed with a system...

  6. Comparing atmosphere-land surface feedbacks from models within the tropics (CALM). Part 1: Evaluation of CMIP5 GCMs to simulate the land surface-atmosphere feedback

    Science.gov (United States)

    Williams, C.; Allan, R.; Kniveton, D.

    2012-04-01

    Man-made transformations to the environment, and in particular the land surface, are having a large impact on the distribution (in both time and space) of rainfall, upon which all life is reliant. From global changes in the composition of the atmosphere, through the emission of greenhouse gases and aerosols, to more localised land use and land cover changes due to an expanding population with an increasing ecological footprint, human activity has a considerable impact on the processes controlling rainfall. This is of particular importance for environmentally vulnerable regions such as many of those in the tropics. Here, widespread poverty, an extensive disease burden and pockets of political instability has resulted in a low resilience and limited adaptative capacity to climate related shocks and stresses. Recently, the 5th Climate Modelling Intercomparison Project (CMIP5) has run a number of state-of-the-art climate models using various present-day and future emission scenarios of greenhouse gases, and therefore provides an unprecedented amount of simulated model data. This paper presents the results of the first stage of a larger project, aiming to further our understanding of how the interactions between tropical rainfall and the land surface are represented in some of the latest climate model simulations. Focusing on precipitation, soil moisture and near-surface temperature, this paper compares the data from all of these models, as well as blended observational-satellite data, to see how the interactions between rainfall and the land surface differs (or agrees) between the models and reality. Firstly, in an analysis of the processes from the "observed" data, the results suggest a strong positive relationship between precipitation and soil moisture at both daily and seasonal timescales. There is a weaker and negative relationship between precipitation and temperature, and likewise between soil moisture and temperature. For all variables, the correlations are stronger at the seasonal timescale. These results also suggest that there are "hotspots" of high linear gradients between precipitation and soil moisture, corresponding to regions experiencing heavy rainfall. Secondly, in a comparison of these relationships across all available models, preliminary results suggest that there is high variability in the ability of the models to reproduce the observed correlations between precipitation and soil moisture. All models show weaker correlations than in the observed at daily timescales. Finally, one of the models (namely HadGEM2-ES, from the UK Met Office Hadley Centre) will be focused upon as an example case study. Here, preliminary findings suggest a difference between the model and the observations in the timings of the correlations, with the model showing the highest positive correlations when precipitation leads soil moisture by one day.

  7. Potential feedback mechanism between phytoplankton and upper ocean circulation with oceanic radiative transfer processes influenced by phytoplankton - Numerical ocean, general circulation models and an analytical solution

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; Kano, M.; PrasannaKumar, S.; Oberhuber, J.M.; Muneyama, K.; Ueyoshi, K.; Subrahmanyam, B.; Nakata, K.; Lai, C.A.; Frouin, R.

    and Dickey (1987) demonstrate that the at- tenuation of visible energy and photosynthetically available radiation (PAR) (Morel, 1978) are primarily functions of chlorophyll pigments. iturriaga and Potential Feedback Mechanism 257 Siegel (1989) reported... isoPYcnal coordinate (BPYC) general circulation model (Oberhuber, 1993), Nakamoto et al. (2001) showed that surface chlorophyll pigments in the equatorial Pacific not only influence vertical penetration of solar ra- diation, but also modify...

  8. Instability and breakdown of the coral-algae symbiosis upon exceedence of the interglacial pCO2 threshold (>260 ppmv): the "missing" Earth-System feedback mechanism

    Science.gov (United States)

    Wooldridge, Scott A.

    2017-12-01

    Changes in the atmospheric partial pressure of CO2 ( pCO2) leads to predictable impacts on the surface ocean carbonate system. Here, the importance of atmospheric pCO2 ecosystems. Indeed, it is concluded that this symbiotic threshold enacts a fundamental feedback mechanism needed to explain the characteristic dynamics (and drivers) of the coupled land-ocean-atmosphere carbon cycle of the Earth System since the mid-Miocene, some 25 million yr ago.

  9. The interleukin-6 and noradrenaline mediated inflammation-stress feedback mechanism is dysregulated in metabolic syndrome: Effect of exercise

    Directory of Open Access Journals (Sweden)

    Ortega Eduardo

    2011-05-01

    Full Text Available Abstract Background Metabolic syndrome (MS is a metabolic disorder associated with obesity, type-II diabetes, and "low grade inflammation", with the concomitant increased risk of cardiovascular events. Removal of the inflammatory mediator signals is a promising strategy to protect against insulin resistance, obesity, and other problems associated with MS such as cardiovascular disease. The aim of the present investigation was to determine the "inflammatory and stress status" in an experimental model of MS, and to evaluate the effect of a program of habitual exercise and the resulting training-induced adaptation to the effects of a single bout of acute exercise. Methods Obese Zucker rats (fa/fa were used as the experimental model of MS, and lean Zucker rats (Fa/fa were used for reference values. The habitual exercise (performed by the obese rats consisted of treadmill running: 5 days/week for 14 weeks, at 35 cm/s for 35 min in the last month. The acute exercise consisted of a single session of 25-35 min at 35 cm/s. Circulating concentrations of IL-6 (a cytokine that regulates the inflammatory and metabolic responses, CRP (a systemic inflammatory marker, and corticosterone (CTC (the main glucocorticoid in rats were determined by ELISA, and that of noradrenaline (NA was determined by HPLC. Glucose was determined by standard methods. Results The genetically obese animals showed higher circulating levels of glucose, IL-6, PCR, and NA compared with the control lean animals. The habitual exercise program increased the concentration of IL-6, PCR, NA, and glucose, but decreased that of CTC. Acute exercise increased IL-6, CRP, and NA in the sedentary obese animals, but not in the trained obese animals. CTC was increased after the acute exercise in the trained animals only. Conclusion Animals with MS present a dysregulation in the feedback mechanism between IL-6 and NA which can contribute to the systemic low-grade inflammation and/or hyperglycaemia of MS

  10. Closed-loop mechanical ventilation for lung injury: a novel physiological-feedback mode following the principles of the open lung concept.

    Science.gov (United States)

    Schwaiberger, David; Pickerodt, Philipp A; Pomprapa, Anake; Tjarks, Onno; Kork, Felix; Boemke, Willehad; Francis, Roland C E; Leonhardt, Steffen; Lachmann, Burkhard

    2017-06-26

    Adherence to low tidal volume (V T ) ventilation and selected positive end-expiratory pressures are low during mechanical ventilation for treatment of the acute respiratory distress syndrome. Using a pig model of severe lung injury, we tested the feasibility and physiological responses to a novel fully closed-loop mechanical ventilation algorithm based on the "open lung" concept. Lung injury was induced by surfactant washout in pigs (n = 8). Animals were ventilated following the principles of the "open lung approach" (OLA) using a fully closed-loop physiological feedback algorithm for mechanical ventilation. Standard gas exchange, respiratory- and hemodynamic parameters were measured. Electrical impedance tomography was used to quantify regional ventilation distribution during mechanical ventilation. Automatized mechanical ventilation provided strict adherence to low V T -ventilation for 6 h in severely lung injured pigs. Using the "open lung" approach, tidal volume delivery required low lung distending pressures, increased recruitment and ventilation of dorsal lung regions and improved arterial blood oxygenation. Physiological feedback closed-loop mechanical ventilation according to the principles of the open lung concept is feasible and provides low tidal volume ventilation without human intervention. Of importance, the "open lung approach"-ventilation improved gas exchange and reduced lung driving pressures by opening atelectasis and shifting of ventilation to dorsal lung regions.

  11. Dynamics of one- and two-dimensional fronts in a bistable equation with time-delayed global feedback: Propagation failure and control mechanisms

    International Nuclear Information System (INIS)

    Boubendir, Yassine; Mendez, Vicenc; Rotstein, Horacio G.

    2010-01-01

    We study the evolution of fronts in a bistable equation with time-delayed global feedback in the fast reaction and slow diffusion regime. This equation generalizes the Hodgkin-Grafstein and Allen-Cahn equations. We derive a nonlinear equation governing the motion of fronts, which includes a term with delay. In the one-dimensional case this equation is linear. We study the motion of one- and two-dimensional fronts, finding a much richer dynamics than for the previously studied cases (without time-delayed global feedback). We explain the mechanism by which localized fronts created by inhibitory global coupling loose stability in a Hopf bifurcation as the delay time increases. We show that for certain delay times, the prevailing phase is different from that corresponding to the system in the absence of global coupling. Numerical simulations of the partial differential equation are in agreement with the analytical predictions.

  12. Prolonged silicon carbide integrated circuit operation in Venus surface atmospheric conditions

    Directory of Open Access Journals (Sweden)

    Philip G. Neudeck

    2016-12-01

    Full Text Available The prolonged operation of semiconductor integrated circuits (ICs needed for long-duration exploration of the surface of Venus has proven insurmountably challenging to date due to the ∼ 460 °C, ∼ 9.4 MPa caustic environment. Past and planned Venus landers have been limited to a few hours of surface operation, even when IC electronics needed for basic lander operation are protected with heavily cumbersome pressure vessels and cooling measures. Here we demonstrate vastly longer (weeks electrical operation of two silicon carbide (4H-SiC junction field effect transistor (JFET ring oscillator ICs tested with chips directly exposed (no cooling and no protective chip packaging to a high-fidelity physical and chemical reproduction of Venus’ surface atmosphere. This represents more than 100-fold extension of demonstrated Venus environment electronics durability. With further technology maturation, such SiC IC electronics could drastically improve Venus lander designs and mission concepts, fundamentally enabling long-duration enhanced missions to the surface of Venus.

  13. Multi-station synthesis of early twentieth century surface atmospheric electricity measurements for upper tropospheric properties

    Directory of Open Access Journals (Sweden)

    R. G. Harrison

    2007-07-01

    Full Text Available The vertical columnar current density in the global atmospheric electrical circuit depends on the local columnar resistance. A simple model for the columnar resistance is suggested, which separates the local boundary layer component from the upper troposphere cosmic ray component, and calculates the boundary layer component from a surface measurement of air conductivity. This theory is shown to provide reasonable agreement with observations. One application of the simple columnar model theory is to provide a basis for the synthesis of surface atmospheric electrical measurements made simultaneously at several European sites. Assuming the ionospheric potential to be common above all the sites, the theoretical air-earth current density present in the absence of a boundary layer columnar resistance can be found by extrapolation. This is denoted the free troposphere limit air-earth current density, J0. Using early surface data from 1909 when no ionospheric potential data are available for corroboration, J0 is found to be ~6 pA m−2, although this is subject to uncertainties in the data and limitations in the theory. Later (1966–1971 European balloon and surface data give J0=2.4 pA m−2.

  14. Preface paper to the Semi-Arid Land-Surface-Atmosphere (SALSA) Program special issue

    Science.gov (United States)

    Goodrich, D.C.; Chehbouni, A.; Goff, B.; MacNish, B.; Maddock, T.; Moran, S.; Shuttleworth, W.J.; Williams, D.G.; Watts, C.; Hipps, L.H.; Cooper, D.I.; Schieldge, J.; Kerr, Y.H.; Arias, H.; Kirkland, M.; Carlos, R.; Cayrol, P.; Kepner, W.; Jones, B.; Avissar, R.; Begue, A.; Bonnefond, J.-M.; Boulet, G.; Branan, B.; Brunel, J.P.; Chen, L.C.; Clarke, T.; Davis, M.R.; DeBruin, H.; Dedieu, G.; Elguero, E.; Eichinger, W.E.; Everitt, J.; Garatuza-Payan, J.; Gempko, V.L.; Gupta, H.; Harlow, C.; Hartogensis, O.; Helfert, M.; Holifield, C.; Hymer, D.; Kahle, A.; Keefer, T.; Krishnamoorthy, S.; Lhomme, J.-P.; Lagouarde, J.-P.; Lo, Seen D.; Luquet, D.; Marsett, R.; Monteny, B.; Ni, W.; Nouvellon, Y.; Pinker, R.; Peters, C.; Pool, D.; Qi, J.; Rambal, S.; Rodriguez, J.; Santiago, F.; Sano, E.; Schaeffer, S.M.; Schulte, M.; Scott, R.; Shao, X.; Snyder, K.A.; Sorooshian, S.; Unkrich, C.L.; Whitaker, M.; Yucel, I.

    2000-01-01

    The Semi-Arid Land-Surface-Atmosphere Program (SALSA) is a multi-agency, multi-national research effort that seeks to evaluate the consequences of natural and human-induced environmental change in semi-arid regions. The ultimate goal of SALSA is to advance scientific understanding of the semi-arid portion of the hydrosphere-biosphere interface in order to provide reliable information for environmental decision making. SALSA approaches this goal through a program of long-term, integrated observations, process research, modeling, assessment, and information management that is sustained by cooperation among scientists and information users. In this preface to the SALSA special issue, general program background information and the critical nature of semi-arid regions is presented. A brief description of the Upper San Pedro River Basin, the initial location for focused SALSA research follows. Several overarching research objectives under which much of the interdisciplinary research contained in the special issue was undertaken are discussed. Principal methods, primary research sites and data collection used by numerous investigators during 1997-1999 are then presented. Scientists from about 20 US, five European (four French and one Dutch), and three Mexican agencies and institutions have collaborated closely to make the research leading to this special issue a reality. The SALSA Program has served as a model of interagency cooperation by breaking new ground in the approach to large scale interdisciplinary science with relatively limited resources.

  15. Effects of Near-Surface Atmospheric Stability and Moisture on Wildfire Behavior and Consequences for Haines Index

    Science.gov (United States)

    Ruiyu Sun; Mary Ann Jenkins

    2003-01-01

    Since the 1950s, extensive research has been conducted to investigate the relationship between near-surface atmospheric conditions and large wildfire growth and occurrence. Observational studies have demonstrated that near-surface dryness (e-g., Fahnestock 1965) and atmospheric instability (e-g., Brotak and Reifsnyder 1977) are correlated with large wildfire growth and...

  16. Reviews and syntheses : An empirical spatiotemporal description of the global surface-atmosphere carbon fluxes: Opportunities and data limitations

    NARCIS (Netherlands)

    Zscheischler, Jakob; Mahecha, Miguel D.; Avitabile, Valerio; Calle, Leonardo; Carvalhais, Nuno; Ciais, Philippe; Gans, Fabian; Gruber, Nicolas; Hartmann, Jens; Herold, Martin; Ichii, Kazuhito; Jung, Martin; Landschützer, Peter; Laruelle, Goulven G.; Lauerwald, Ronny; Papale, Dario; Peylin, Philippe; Poulter, Benjamin; Ray, Deepak; Regnier, Pierre; Rödenbeck, Christian; Roman-Cuesta, Rosa M.; Schwalm, Christopher R.; Tramontana, Gianluca; Tyukavina, Alexandra; Valentini, Riccardo; Van Der Werf, Guido; West, Tristram O.; Wolf, Julie E.; Reichstein, Markus

    2017-01-01

    Understanding the global carbon (C) cycle is of crucial importance to map current and future climate dynamics relative to global environmental change. A full characterization of C cycling requires detailed information on spatiotemporal patterns of surface-atmosphere fluxes. However, relevant C cycle

  17. Pilot study of laser induced breakdown spectroscopy for tissue differentiation by monitoring the plume created during laser surgery — An approach on a feedback Laser control mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Kanawade, Rajesh, E-mail: Rajesh.Kanawade@aot.uni-erlangen.de [Clinical Photonics Lab, Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 6, 91052 Erlangen (Germany); Institute of Photonics Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen (Germany); Mehari, Fanuel [Master Programme in Advanced Optical Technologies (MAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 6, 91052 Erlangen (Germany); Knipfer, Christian; Rohde, Maximilian [Department of Oral and Maxillofacial Surgery, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Glueckstrasse 11, 91054 Erlangen (Germany); Tangermann-Gerk, Katja [Bayerisches Laserzentrum GmbH, Konrad-Zuse-Strasse 2-6, 91052 Erlangen (Germany); Schmidt, Michael [Clinical Photonics Lab, Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 6, 91052 Erlangen (Germany); Institute of Photonics Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen (Germany); Bayerisches Laserzentrum GmbH, Konrad-Zuse-Strasse 2-6, 91052 Erlangen (Germany); and others

    2013-09-01

    This study focuses on tissue differentiation using ‘Laser Induced Breakdown Spectroscopy’ (LIBS) by monitoring the plasma plume created during laser surgery processes. This technique is aimed at controlling a laser surgery feedback system in real time. An Excimer laser (Ar-F 193 nm) was used for the ablation of tissue samples. Fat, muscle, nerve and skin tissue samples of bisected ex-vivo pig heads were prepared as test objects for the ablation procedure. A single fiber was used to collect emissions and deliver them to a spectrometer. The obtained LIBS spectra in the measured emissions were analyzed to determine each tissue type according to their chemical composition. The elements found in the samples and their emission spectra were in agreement with those described in literature. The collected LIBS spectra were analyzed to differentiate the tissues using statistical data analysis: Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and Receiver Operating Characteristics (ROC). The obtained preliminary results suggest a successful differentiation of the target tissues with high sensitivity and specificity. The main goal of this study was to qualitatively identify tissue types during laser ablation, which will provide a real time feedback mechanism for clinical Laser surgery applications to significantly improve the accuracy and safety of laser surgery procedures. - Graphical abstract: Skin, fat, muscle and nerve tissue differentiation. - Highlights: • Methods to differentiate tissues for the application in a laser surgery feedback control system • Successful differentiation of the target tissues with high sensitivity and specificity for laser surgery application • Real time feedback mechanism for clinical Laser surgery applications • Laser surgery requirements • Biomedical applications of LIBS.

  18. Thermal-chemical-mechanical feedback during fluid-rock interactions: Implications for chemical transport and scales of equilibria in the crust

    International Nuclear Information System (INIS)

    Dutrow, Barbara

    2008-01-01

    Our research evaluates the hypothesis that feedback amongst thermal-chemical-mechanical processes operative in fluid-rock systems alters the fluid flow dynamics of the system which, in turn, affects chemical transport and temporal and spatial scales of equilibria, thus impacting the resultant mineral textural development of rocks. Our methods include computational experimentation and detailed analyses of fluid-infiltrated rocks from well-characterized terranes. This work focuses on metamorphic rocks and hydrothermal systems where minerals and their textures are utilized to evaluate pressure (P), temperature (T), and time (t) paths in the evolution of mountain belts and ore deposits, and to interpret tectonic events and the timing of these events. Our work on coupled processes also extends to other areas where subsurface flow and transport in porous media have consequences such as oil and gas movement, geothermal system development, transport of contaminants, nuclear waste disposal, and other systems rich in fluid-rock reactions. Fluid-rock systems are widespread in the geologic record. Correctly deciphering the products resulting from such systems is important to interpreting a number of geologic phenomena. These systems are characterized by complex interactions involving time-dependent, non-linear processes in heterogeneous materials. While many of these interactions have been studied in isolation, they are more appropriately analyzed in the context of a system with feedback. When one process impacts another process, time and space scales as well as the overall outcome of the interaction can be dramatically altered. Our goals to test this hypothesis are: to develop and incorporate algorithms into our 3D heat and mass transport code to allow the effects of feedback to be investigated numerically, to analyze fluid infiltrated rocks from a variety of terranes at differing P-T conditions, to identify subtle features of the infiltration of fluids and/or feedback, and

  19. The spatiotemporal dynamics of microbes in the near-surface atmosphere

    Science.gov (United States)

    Bowers, Robert Michael

    With this dissertation, I present four culture independent studies examining the spatiotemporal distributions of microbial communities in the near-surface atmosphere. The goals of this dissertation work were to examine the biogeographical patterns that airborne microbes exhibit over a variety of spatiotemporal scales, and to determine the likely sources of bacteria to the near-surface environment. First I explored the short-term (two-week) changes in microbial community structure (bacteria, fungi and pollen) of the near surface atmosphere at the high elevation research site, Storm Peak Laboratory, located in northern Colorado, USA. This study revealed that the nearsurface atmosphere is abundant with microbes, and that the airborne communities are composed of taxa that are typical of cold environments. Additionally, the bacteria identified in the air samples showed high sequence similarity to bacterial lineages possessing the ice nucleating phenotype, suggesting the possibility of bacterial induced cloud formation. Second, I examined the spatial diversity of airborne bacterial communities across the three dominant land-use types of the Colorado Front Range: forests, suburban areas, and agricultural sites. The airborne communities exhibited significant community level shifts across the three land-use types, however the differences could not be attributed to the prevailing meteorological conditions, suggesting that the characteristics of the local terrestrial surfaces have a greater influence on the airborne communities than the prevailing meteorology. Overall, the airborne communities above the three land-use types appeared to be unique to potential source environments, however the taxa driving the land-use patterns were related to those taxa that were indicative of either soils or leaf surfaces. Third, I carried out a seasonal (summer and winter) study of the airborne bacterial communities of the Great Lakes region of the USA. The bacterial communities inhabiting

  20. Activation of parallel fiber feedback by spatially diffuse stimuli reduces signal and noise correlations via independent mechanisms in a cerebellum-like structure.

    Directory of Open Access Journals (Sweden)

    Benjamin Simmonds

    2015-01-01

    Full Text Available Correlations between the activities of neighboring neurons are observed ubiquitously across systems and species and are dynamically regulated by several factors such as the stimulus' spatiotemporal extent as well as by the brain's internal state. Using the electrosensory system of gymnotiform weakly electric fish, we recorded the activities of pyramidal cell pairs within the electrosensory lateral line lobe (ELL under spatially localized and diffuse stimulation. We found that both signal and noise correlations were markedly reduced (>40% under the latter stimulation. Through a network model incorporating key anatomical features of the ELL, we reveal how activation of diffuse parallel fiber feedback from granule cells by spatially diffuse stimulation can explain both the reduction in signal as well as the reduction in noise correlations seen experimentally through independent mechanisms. First, we show that burst-timing dependent plasticity, which leads to a negative image of the stimulus and thereby reduces single neuron responses, decreases signal but not noise correlations. Second, we show trial-to-trial variability in the responses of single granule cells to sensory input reduces noise but not signal correlations. Thus, our model predicts that the same feedback pathway can simultaneously reduce both signal and noise correlations through independent mechanisms. To test this prediction experimentally, we pharmacologically inactivated parallel fiber feedback onto ELL pyramidal cells. In agreement with modeling predictions, we found that inactivation increased both signal and noise correlations but that there was no significant relationship between magnitude of the increase in signal correlations and the magnitude of the increase in noise correlations. The mechanisms reported in this study are expected to be generally applicable to the cerebellum as well as other cerebellum-like structures. We further discuss the implications of such

  1. Atmospheric moisture supersaturation in the near-surface atmosphere at Dome C, Antarctic Plateau

    Science.gov (United States)

    Genthon, Christophe; Piard, Luc; Vignon, Etienne; Madeleine, Jean-Baptiste; Casado, Mathieu; Gallée, Hubert

    2017-01-01

    Supersaturation often occurs at the top of the troposphere where cirrus clouds form, but is comparatively unusual near the surface where the air is generally warmer and laden with liquid and/or ice condensation nuclei. One exception is the surface of the high Antarctic Plateau. One year of atmospheric moisture measurement at the surface of Dome C on the East Antarctic Plateau is presented. The measurements are obtained using commercial hygrometry sensors modified to allow air sampling without affecting the moisture content, even in the case of supersaturation. Supersaturation is found to be very frequent. Common unadapted hygrometry sensors generally fail to report supersaturation, and most reports of atmospheric moisture on the Antarctic Plateau are thus likely biased low. The measurements are compared with results from two models implementing cold microphysics parameterizations: the European Center for Medium-range Weather Forecasts through its operational analyses, and the Model Atmosphérique Régional. As in the observations, supersaturation is frequent in the models but the statistical distribution differs both between models and observations and between the two models, leaving much room for model improvement. This is unlikely to strongly affect estimations of surface sublimation because supersaturation is more frequent as temperature is lower, and moisture quantities and thus water fluxes are small anyway. Ignoring supersaturation may be a more serious issue when considering water isotopes, a tracer of phase change and temperature, largely used to reconstruct past climates and environments from ice cores. Because observations are easier in the surface atmosphere, longer and more continuous in situ observation series of atmospheric supersaturation can be obtained than higher in the atmosphere to test parameterizations of cold microphysics, such as those used in the formation of high-altitude cirrus clouds in meteorological and climate models.

  2. Atmospheric moisture supersaturatons in the near-surface atmosphere of Dome C, Antarctic Plateau

    Science.gov (United States)

    Genthon, Christophe; Piard, Luc; Vignon, Etienne; Madeleine, Jean-Baptiste; Casado, Mathieu; Gallée, Hubert

    2017-04-01

    Moisture supersaturations occur at the top of the troposphere where cirrus clouds form, but is comparatively unusual near the surface where the air is generally warmer and laden with liquid and/or ice condensation nuclei. One exception is the surface of the high antarctic plateau. This study presents one year of atmospheric moisture measurement at the surface of Dome C on the East Antarctic plateau. The measurements are obtained using commercial hygrometry sensors adapted to allow air sampling without affecting the moisture content even in case of supersaturation. Supersaturation is found to be very frequent. Common unadapted hygrometry sensors generally fail to report supersaturation, and most reports of atmospheric moisture on the antarctic plateau are thus likely biased low. The measurements are compared with results from 2 models with cold microphysics parametrizations: the European Center for Medium-range Weather Forecasts through its operational analyses, and the Model Atmosphérique Régional. As in the observations, supersaturation is frequent in the models but the statistical distribution differs both between models and observations and between the 2 models, leaving much room for model improvement. The representation of supersaturations is not critical for the estimations of surface sublimation since they are more frequent as temperature is lower i.e. as moisture quantities and water fluxes are small. However, ignoring near-surface supersaturation may be a more serious issue for the modeling of fog and when considering water isotopes, a tracer of phase change and temperature, largely used to reconstruct past climates and environments from ice cores. Because observations are easier in the surface atmosphere, longer and more continuous in situ observation series of atmospheric supersaturation can be obtained than higher in the atmosphere to test parameterizations of cold microphysics, such as those used in the formation of high altitude cirrus clouds in

  3. Seasonal variability in bacterial and fungal diversity of the near-surface atmosphere.

    Science.gov (United States)

    Bowers, Robert M; Clements, Nicholas; Emerson, Joanne B; Wiedinmyer, Christine; Hannigan, Michael P; Fierer, Noah

    2013-01-01

    Bacteria and fungi are ubiquitous throughout the Earth's lower atmosphere where they often represent an important component of atmospheric aerosols with the potential to impact human health and atmospheric dynamics. However, the diversity, composition, and spatiotemporal dynamics of these airborne microbes remain poorly understood. We performed a comprehensive analysis of airborne microbes across two aerosol size fractions at urban and rural sites in the Colorado Front Range over a 14-month period. Coarse (PM10-2.5) and fine (PM2.5) particulate matter samples were collected at weekly intervals with both bacterial and fungal diversity assessed via high-throughput sequencing. The diversity and composition of the airborne communities varied across the sites, between the two size fractions, and over time. Bacteria were the dominant type of bioaerosol in the collected air samples, while fungi and plants (pollen) made up the remainder, with the relative abundances of fungi peaking during the spring and summer months. As bacteria made up the majority of bioaerosol particles, we analyzed the bacterial communities in greater detail using a bacterial-specific 16S rRNA gene sequencing approach. Overall, bacterial taxonomic richness and the relative abundances of specific bacterial taxa exhibited significant patterns of seasonality. Likewise, airborne bacterial communities varied significantly between sites and across aerosol size fractions. Source-tracking analyses indicate that soils and leaves represented important sources of bacteria to the near-surface atmosphere across all locations with cow fecal bacteria also representing an important source of bioaerosols at the more rural sites during early fall and early spring. Together, these data suggest that a complex set of environmental factors, including changes in atmospheric conditions and shifts in the relative importance of available microbial sources, act to control the composition of microbial bioaerosols in rural and

  4. Airborne spectral measurements of surface-atmosphere anisotropy for several surfaces and ecosystems over southern Africa

    Science.gov (United States)

    Gatebe, Charles K.; King, Michael D.; Platnick, Steve; Arnold, G. Thomas; Vermote, Eric F.; Schmid, Beat

    2003-07-01

    The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft during the Southern Africa Regional Science Initiative 2000 (SAFARI 2000) dry season campaign and obtained measurements of bidirectional reflectance distribution function (BRDF) for a variety of natural surfaces and ecosystems in southern Africa. To measure the BRDF of the surface-atmosphere system, the University of Washington CV-580 banked at a roll angle of ˜20° and flew circles about 3 km in diameter above the surface, taking approximately 2 min. Multiple circular orbits were acquired over selected surfaces so that average BRDFs could be acquired, smoothing out small-scale surface and atmospheric inhomogeneities. In this paper, we present results of BRDFs taken over two Earth Observing System (EOS) validation sites: Skukuza tower, South Africa (25.0°S, 31.5°E) and Mongu tower, Zambia (15.4°S, 23.3°E). Additional sites are discussed and include the Maun tower, Botswana (20.0°S, 23.6°E), Sua Pan, Botswana (20.6°S, 25.9°E), Etosha Pan, Namibia (19.0°S, 16.0°E), and marine stratocumulus clouds off the west coast of Namibia (20.5°S, 13.1°E). Results clearly show anisotropy in reflected solar radiation over the various surfaces types: savanna, salt pans, and cloud. The greatest anisotropy is observed over marine stratus clouds, which exhibit strong forward scattering as well as important water cloud scattering features such as the rainbow and glory. The BRDF over savanna is characterized by a distinct backscattering peak in the principal plane and shows directional and spectral variations. Over the pans, the BRDF is more enhanced in the backscattering plane than forward scattering plane and shows little directional variation.

  5. Formativ Feedback

    DEFF Research Database (Denmark)

    Hyldahl, Kirsten Kofod

    Denne bog undersøger, hvordan lærere kan anvende feedback til at forbedre undervisningen i klasselokalet. I denne sammenhæng har John Hattie, professor ved Melbourne Universitet, udviklet en model for feedback, hvilken er baseret på synteser af meta-analyser. I 2009 udgav han bogen "Visible...

  6. Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Several Surfaces and Ecosystem over Southern Africa

    Science.gov (United States)

    Gatebe, C. K.; King, M. D.; Tsay, S.; Arnold, G. T.; Li, J. Y.

    2001-12-01

    The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft and took measurements on 23 flights between August 15 and September 16. On 12 of those flights, BRF measurements were obtained over different natural surfaces and ecosystem in southern Africa. The BRF measurements were done to characterize surface anisotropy in support of SAFARI 2000 science objectives principally to validate products from NASA's EOS satellites, and to parameterize and validate BRF models. In this paper we present results of BRFs taken over two EOS validation sites: Skukuza tower, South Africa (25.0 oS, 31.5 oE) and Mongu tower, Zambia (15.4 oS, 23.3 oE). Additional sites are also considered and include, Maun tower, Botswana (20.0 oS, 23.5 oE), Sowa Pan, Botswana (20.6 oS, 26.2 oE) and Etosha Pan, Namibia (19.0 oS, 16.0 oE). The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 μ m), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 μ m). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to bank at a comfortable roll angle of ~20 o and fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were

  7. VCP Is an integral component of a novel feedback mechanism that controls intracellular localization of catalase and H2O2 Levels.

    Science.gov (United States)

    Murakami, Katsuhiro; Ichinohe, Yuzuru; Koike, Masaaki; Sasaoka, Norio; Iemura, Shun-ichiro; Natsume, Tohru; Kakizuka, Akira

    2013-01-01

    Catalase is a key antioxidant enzyme that catalyzes the decomposition of hydrogen peroxide (H2O2) to water and oxygen, and it appears to shuttle between the cytoplasm and peroxisome via unknown mechanisms. Valosin-containing protein (VCP) belongs to the AAA class of ATPases and is involved in diverse cellular functions, e.g. cell cycle and protein degradation, etc. Here we show that VCP and PEX19, a protein essential for peroxisome biogenesis, interact with each other. Knockdown of either VCP or PEX19 resulted in a predominantly cytoplasmic redistribution of catalase, and loss of VCP ATPase activity also increased its cytoplasmic redistribution. Moreover, VCP knockdown decreased intracellular ROS levels in normal and H2O2-treated cells, and an oxidation-resistant VCP impaired the ROS-induced cytoplasmic redistribution of catalase. These observations reveal a novel feedback mechanism, in which VCP can sense H2O2 levels, and regulates them by controlling the localization of catalase.

  8. Positive feedback promotes oscillations in negative feedback loops.

    Science.gov (United States)

    Ananthasubramaniam, Bharath; Herzel, Hanspeter

    2014-01-01

    A simple three-component negative feedback loop is a recurring motif in biochemical oscillators. This motif oscillates as it has the three necessary ingredients for oscillations: a three-step delay, negative feedback, and nonlinearity in the loop. However, to oscillate, this motif under the common Goodwin formulation requires a high degree of cooperativity (a measure of nonlinearity) in the feedback that is biologically "unlikely." Moreover, this recurring negative feedback motif is commonly observed augmented by positive feedback interactions. Here we show that these positive feedback interactions promote oscillation at lower degrees of cooperativity, and we can thus unify several common kinetic mechanisms that facilitate oscillations, such as self-activation and Michaelis-Menten degradation. The positive feedback loops are most beneficial when acting on the shortest lived component, where they function by balancing the lifetimes of the different components. The benefits of multiple positive feedback interactions are cumulative for a majority of situations considered, when benefits are measured by the reduction in the cooperativity required to oscillate. These positive feedback motifs also allow oscillations with longer periods than that determined by the lifetimes of the components alone. We can therefore conjecture that these positive feedback loops have evolved to facilitate oscillations at lower, kinetically achievable, degrees of cooperativity. Finally, we discuss the implications of our conclusions on the mammalian molecular clock, a system modeled extensively based on the three-component negative feedback loop.

  9. Histone demethylase KDM5A is regulated by its reader domain through a positive-feedback mechanism

    Science.gov (United States)

    Torres, Idelisse Ortiz; Kuchenbecker, Kristopher M.; Nnadi, Chimno I.; Fletterick, Robert J.; Kelly, Mark J. S.; Fujimori, Danica Galonić

    2015-02-01

    The retinoblastoma binding protein KDM5A removes methyl marks from lysine 4 of histone H3 (H3K4). Misregulation of KDM5A contributes to the pathogenesis of lung and gastric cancers. In addition to its catalytic jumonji C domain, KDM5A contains three PHD reader domains, commonly recognized as chromatin recruitment modules. It is unknown whether any of these domains in KDM5A have functions beyond recruitment and whether they regulate the catalytic activity of the demethylase. Here using biochemical and nuclear magnetic resonance (NMR)-based structural studies, we show that the PHD1 preferentially recognizes unmethylated H3K4 histone tail, product of KDM5A-mediated demethylation of tri-methylated H3K4 (H3K4me3). Binding of unmodified H3 peptide to the PHD1 stimulates catalytic domain-mediated removal of methyl marks from H3K4me3 peptide and nucleosome substrates. This positive-feedback mechanism—enabled by the functional coupling between a reader and a catalytic domain in KDM5A—suggests a model for the spread of demethylation on chromatin.

  10. Iodothyronine deiodinase gene analysis of the Pacific oyster Crassostrea gigas reveals possible conservation of thyroid hormone feedback regulation mechanism in mollusks

    Science.gov (United States)

    Huang, Wen; Xu, Fei; Qu, Tao; Li, Li; Que, Huayong; Zhang, Guofan

    2015-07-01

    Iodothyronine deiodinase catalyzes the initiation and termination of thyroid hormones (THs) effects, and plays a central role in the regulation of thyroid hormone level in vertebrates. In non-chordate invertebrates, only one deiodinase has been identified in the scallop Chlamys farreri. Here, two deiodinases were cloned in the Pacific oyster Crassostrea gigas ( CgDx and CgDy). The characteristic in-frame TGA codons and selenocysteine insertion sequence elements in the oyster deiodinase cDNAs supported the activity of them. Furthermore, seven orthologs of deiodinases were found by a tblastn search in the mollusk Lottia gigantea and the annelid Capitella teleta. A phylogenetic analysis revealed that the deiodinase gene originated from an common ancestor and a clade-specific gene duplication occurred independently during the differentiation of the mollusk, annelid, and vertebrate lineages. The distinct spatiotemporal expression patterns implied functional divergence of the two deiodinases. The expression of CgDx and CgDy was influenced by L-thyroxine T4, and putative thyroid hormone responsive elements were found in their promoters, which suggested that the oyster deiodinases were feedback regulated by TH. Epinephrine stimulated the expression level of CgDx and CgDy, suggesting an interaction effect between different hormones. This study provides the first evidence for the existence of a conserved TH feedback regulation mechanism in mollusks, providing insights into TH evolution.

  11. Sphingoid bases and the serine catabolic enzyme CHA1 define a novel feedforward/feedback mechanism in the response to serine availability.

    Science.gov (United States)

    Montefusco, David J; Newcomb, Benjamin; Gandy, Jason L; Brice, Sarah E; Matmati, Nabil; Cowart, L Ashley; Hannun, Yusuf A

    2012-03-16

    Targets of bioactive sphingolipids in Saccharomyces cerevisiae were previously identified using microarray experiments focused on sphingolipid-dependent responses to heat stress. One of these heat-induced genes is the serine deamidase/dehydratase Cha1 known to be regulated by increased serine availability. This study investigated the hypothesis that sphingolipids may mediate the induction of Cha1 in response to serine availability. The results showed that inhibition of de novo synthesis of sphingolipids, pharmacologically or genetically, prevented the induction of Cha1 in response to increased serine availability. Additional studies implicated the sphingoid bases phytosphingosine and dihydrosphingosine as the likely mediators of Cha1 up-regulation. The yeast protein kinases Pkh1 and Pkh2, known sphingoid base effectors, were found to mediate CHA1 up-regulation via the transcription factor Cha4. Because the results disclosed a role for sphingolipids in negative feedback regulation of serine metabolism, we investigated the effects of disrupting this mechanism on sphingolipid levels and on cell growth. Intriguingly, exposure of the cha1Δ strain to high serine resulted in hyperaccumulation of endogenous serine and in turn a significant accumulation of sphingoid bases and ceramides. Under these conditions, the cha1Δ strain displayed a significant growth defect that was sphingolipid-dependent. Together, this work reveals a feedforward/feedback loop whereby the sphingoid bases serve as sensors of serine availability and mediate up-regulation of Cha1 in response to serine availability, which in turn regulates sphingolipid levels by limiting serine accumulation.

  12. Pilot study of laser induced breakdown spectroscopy for tissue differentiation by monitoring the plume created during laser surgery — An approach on a feedback Laser control mechanism

    Science.gov (United States)

    Kanawade, Rajesh; Mehari, Fanuel; Knipfer, Christian; Rohde, Maximilian; Tangermann-Gerk, Katja; Schmidt, Michael; Stelzle, Florian

    2013-09-01

    This study focuses on tissue differentiation using 'Laser Induced Breakdown Spectroscopy' (LIBS) by monitoring the plasma plume created during laser surgery processes. This technique is aimed at controlling a laser surgery feedback system in real time. An Excimer laser (Ar-F 193 nm) was used for the ablation of tissue samples. Fat, muscle, nerve and skin tissue samples of bisected ex-vivo pig heads were prepared as test objects for the ablation procedure. A single fiber was used to collect emissions and deliver them to a spectrometer. The obtained LIBS spectra in the measured emissions were analyzed to determine each tissue type according to their chemical composition. The elements found in the samples and their emission spectra were in agreement with those described in literature. The collected LIBS spectra were analyzed to differentiate the tissues using statistical data analysis: Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and Receiver Operating Characteristics (ROC). The obtained preliminary results suggest a successful differentiation of the target tissues with high sensitivity and specificity. The main goal of this study was to qualitatively identify tissue types during laser ablation, which will provide a real time feedback mechanism for clinical Laser surgery applications to significantly improve the accuracy and safety of laser surgery procedures.

  13. Perceived Insider Status and Feedback Reactions: A Dual Path of Feedback Motivation Attribution.

    Science.gov (United States)

    Chen, Xiao; Liao, JianQiao; Wu, Weijiong; Zhang, Wei

    2017-01-01

    Many studies have evaluated how the characteristics of feedback receiver, feedback deliverer and feedback information influence psychological feedback reactions of the feedback receiver while largely neglecting that feedback intervention is a kind of social interaction process. To address this issue, this study proposes that employees' perceived insider status (PIS), as a kind of employee-organization relationship, could also influence employees' reactions to supervisory feedback. In particular, this study investigates the influence of PIS focusing on affective and cognitive feedback reactions, namely feedback satisfaction and feedback utility. Surveys were conducted in a machinery manufacturing company in the Guangdong province of China. Samples were collected from 192 employees. Data analysis demonstrated that PIS and feedback utility possessed a U-shaped relationship, whereas PIS and feedback satisfaction exhibited positively linear relationships. The analysis identified two kinds of mediating mechanisms related to feedback satisfaction and feedback utility. Internal feedback motivation attribution partially mediated the relationship between PIS and feedback satisfaction but failed to do the same with respect to the relationship between PIS and feedback utility. In contrast, external feedback motivation attribution partially mediated the relationship between PIS and feedback utility while failing to mediate the relationship between PIS and feedback satisfaction. Theoretical contributions and practical implications of the findings are discussed at the end of the paper.

  14. Perceived Insider Status and Feedback Reactions: A Dual Path of Feedback Motivation Attribution

    Directory of Open Access Journals (Sweden)

    Weijiong Wu

    2017-05-01

    Full Text Available Many studies have evaluated how the characteristics of feedback receiver, feedback deliverer and feedback information influence psychological feedback reactions of the feedback receiver while largely neglecting that feedback intervention is a kind of social interaction process. To address this issue, this study proposes that employees’ perceived insider status (PIS, as a kind of employee-organization relationship, could also influence employees’ reactions to supervisory feedback. In particular, this study investigates the influence of PIS focusing on affective and cognitive feedback reactions, namely feedback satisfaction and feedback utility. Surveys were conducted in a machinery manufacturing company in the Guangdong province of China. Samples were collected from 192 employees. Data analysis demonstrated that PIS and feedback utility possessed a U-shaped relationship, whereas PIS and feedback satisfaction exhibited positively linear relationships. The analysis identified two kinds of mediating mechanisms related to feedback satisfaction and feedback utility. Internal feedback motivation attribution partially mediated the relationship between PIS and feedback satisfaction but failed to do the same with respect to the relationship between PIS and feedback utility. In contrast, external feedback motivation attribution partially mediated the relationship between PIS and feedback utility while failing to mediate the relationship between PIS and feedback satisfaction. Theoretical contributions and practical implications of the findings are discussed at the end of the paper.

  15. Qualitative tissue differentiation by analysing the intensity ratios of atomic emission lines using laser induced breakdown spectroscopy (LIBS): prospects for a feedback mechanism for surgical laser systems.

    Science.gov (United States)

    Kanawade, Rajesh; Mahari, Fanuel; Klämpfl, Florian; Rohde, Maximilian; Knipfer, Christian; Tangermann-Gerk, Katja; Adler, Werner; Schmidt, Michael; Stelzle, Florian

    2015-01-01

    The research work presented in this paper focuses on qualitative tissue differentiation by monitoring the intensity ratios of atomic emissions using 'Laser Induced Breakdown Spectroscopy' (LIBS) on the plasma plume created during laser tissue ablation. The background of this study is to establish a real time feedback control mechanism for clinical laser surgery systems during the laser ablation process. Ex-vivo domestic pig tissue samples (muscle, fat, nerve and skin) were used in this experiment. Atomic emission intensity ratios were analyzed to find a characteristic spectral line for each tissue. The results showed characteristic elemental emission intensity ratios for the respective tissues. The spectral lines and intensity ratios of these specific elements varied among the different tissue types. The main goal of this study is to qualitatively and precisely identify different tissue types for tissue specific laser surgery. © 2015 The Authors. Journal of Biophotonics published by WILEY-VCH Verlag.

  16. Transverse feedback

    CERN Document Server

    Cornelis, K; Sladen, Jonathan P H; CERN. Geneva. SPS and LEP Division

    1997-01-01

    The aim of these MD's was to set up the transverse feedback for damping in both planes, and to test the charge normalization and gain compensation. The latter is intended to reduce the gain of the feedback for small oscillations in order to improve compatibility with the Q loop. All work was done with 2 x 4 bunches, family A. In the first two MD's the feedback was set up for damping in both planes with charge normalization. In the third, gain compensation was commissioned in the vertical plane with Qv' set to -2. It was found either to increase the level of the m = 0 mode or to leave it unchanged. Under these conditions 6mA total current was accumulated.

  17. Simultaneous observation of seasonal variations of beryllium-7 and typical POPs in near-surface atmospheric aerosols in Guangzhou, China

    Science.gov (United States)

    Pan, Jing; Yang, Yong-Liang; Zhang, Gan; Shi, Jing-Lei; Zhu, Xiao-Hua; Li, Yong; Yu, Han-Qing

    2011-07-01

    Near-surface atmospheric aerosol samples were collected at the sampling frequency of 2-3 d per week for one year from August 2006 to August 2007 at a low latitude station in Tianhe District, Guangzhou, Guangdong Province of southern China. The samples were analyzed for cosmogenic nuclide 7Be and persistent organic pollutants, i.e. organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). The annual average 7Be concentration was 2.59 mBq m -3, with the maximum occurred in May (8.45 mBq m -3) and minimum in late August and early September (0.07 mBq m -3). Winter and spring were the seasons in which the 7Be concentrations were high while summer and autumn were the lower 7Be seasons. Spring peaks in 7Be in the near-surface atmospheric aerosols may have associated with the "spring leak maximum" episode. The annual average ∑OCPs concentration was 345.6 pg m -3, ∑ 33PCBs 317.6 pg m -3, and ∑ 31PBDEs 609.0 pg m -3. The variation trends in the time-series of 7Be, OCPs, PCBs, and PBDEs in near-surface atmospheric aerosol showed both common features and differences. Significant correlations ( R2 = 0.957 and 0.811. respectively, p = 0.01) were observed between the monthly average 7Be concentrations and those of ∑PCBs and ∑PBDEs in summer, autumn, and early winter. The difference between the seasonal variation features of OCPs and PCBs (and PBDEs) could be attributed to the different source functions and physical-chemical properties which could control the behaviors of these compounds in air-aerosol partitions as well as atmospheric transport.

  18. Designing feedback: multimodality and specificity

    NARCIS (Netherlands)

    Ludden, Geke Dina Simone; Sugiyama, Kazuo

    2013-01-01

    Now that many of us carry around devices that are equipped with sensors (e.g., smartphones with accelerometers) we can use these sensors to measure behavior. The data thus captured can be used to give someone feedback about this behavior. These feedback mechanisms are often used in so called smart

  19. Climate forcings and feedbacks

    Science.gov (United States)

    Hansen, James

    1993-01-01

    Global temperature has increased significantly during the past century. Understanding the causes of observed global temperature change is impossible in the absence of adequate monitoring of changes in global climate forcings and radiative feedbacks. Climate forcings are changes imposed on the planet's energy balance, such as change of incoming sunlight or a human-induced change of surface properties due to deforestation. Radiative feedbacks are radiative changes induced by climate change, such as alteration of cloud properties or the extent of sea ice. Monitoring of global climate forcings and feedbacks, if sufficiently precise and long-term, can provide a very strong constraint on interpretation of observed temperature change. Such monitoring is essential to eliminate uncertainties about the relative importance of various climate change mechanisms including tropospheric sulfate aerosols from burning of coal and oil smoke from slash and burn agriculture, changes of solar irradiance changes of several greenhouse gases, and many other mechanisms. The considerable variability of observed temperature, together with evidence that a substantial portion of this variability is unforced indicates that observations of climate forcings and feedbacks must be continued for decades. Since the climate system responds to the time integral of the forcing, a further requirement is that the observations be carried out continuously. However, precise observations of forcings and feedbacks will also be able to provide valuable conclusions on shorter time scales. For example, knowledge of the climate forcing by increasing CFC's relative to the forcing by changing ozone is important to policymakers, as is information on the forcing by CO2 relative to the forcing by sulfate aerosols. It will also be possible to obtain valuable tests of climate models on short time scales, if there is precise monitoring of all forcings and feedbacks during and after events such as a large volcanic eruption

  20. Testosterone interacts with the feedback mechanisms engaged by Tyr985 of the leptin receptor and diet-induced obesity.

    Science.gov (United States)

    Johnson, Joshua A; Calo, Sal; Nair, Lekshmi; IglayReger, Heidi B; Greenwald-Yarnell, Megan; Skorupski, Josh; Myers, Martin G; Bodary, Peter F

    2012-11-01

    Inhibitory signaling through Tyr985 of the leptin receptor contributes to the attenuation of anorectic leptin action in obese animals. Leptin receptor (LEPR-B) Tyr985Leu homozygote mutant mice (termed l/l) were previously generated to study Tyr985's contributions to inhibition of LEPR-B signaling; young female l/l mice display a lean, leptin-sensitive phenotype, while young male l/l are not significantly different from wild-type. We report here that testosterone (but not estrogen) determines the sex-specificity of the l/l phenotype. This provides additional insight into the cellular mechanism by which gonadal hormones determine central sensitivity to leptin, and may help elucidate the long-noted sex differences in leptin sensitivity. Additionally, we observed that Tyr985 signaling protects against a diet-dependent switch that exacerbates obesity with high fat feeding, such that the enhanced leptin sensitivity of l/l mice on a normal diet leads to increased adiposity in the face of chronic high-fat diet. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Alteration of immature sedimentary rocks on Earth and Mars. Recording Aqueous and Surface-atmosphere Processes

    Energy Technology Data Exchange (ETDEWEB)

    Cannon, Kenneth M. [Brown Univ., Providence, RI (United States); Mustard, John F. [Brown Univ., Providence, RI (United States); Salvatore, Mark R. [Arizona State Univ., Mesa, AZ (United States)

    2015-03-05

    The rock alteration and rind formation in analog environments like Antarctica may provide clues to rock alteration and therefore paleoclimates on Mars. Clastic sedimentary rocks derived from basaltic sources have been studied in situ by martian rovers and are likely abundant on the surface of Mars. Moreover, how such rock types undergo alteration when exposed to different environmental conditions is poorly understood compared with alteration of intact basaltic flows. Here we characterize alteration in the chemically immature Carapace Sandstone from Antarctica, a terrestrial analog for martian sedimentary rocks. We employ a variety of measurements similar to those used on previous and current Mars missions. Laboratory techniques included bulk chemistry, powder X-ray diffraction (XRD), hyperspectral imaging and X-ray absorption spectroscopy. Through these methods we find that primary basaltic material in the Carapace Sandstone is pervasively altered to hydrated clay minerals and palagonite as a result of water–rock interaction. A thick orange rind is forming in current Antarctic conditions, superimposing this previous aqueous alteration signature. The rind exhibits a higher reflectance at visible-near infrared wavelengths than the rock interior, with an enhanced ferric absorption edge likely due to an increase in Fe3+ of existing phases or the formation of minor iron (oxy)hydroxides. This alteration sequence in the Carapace Sandstone results from decreased water–rock interaction over time, and weathering in a cold, dry environment, mimicking a similar transition early in martian history. This transition may be recorded in sedimentary rocks on Mars through a similar superimposition mechanism, capturing past climate changes at the hand sample scale. These results also suggest that basalt-derived sediments could have sourced significant volumes of hydrated minerals on early Mars due to their greater permeability compared with intact igneous rocks.

  2. Alterations in glucocorticoid negative feedback following maternal Pb, prenatal stress and the combination: A potential biological unifying mechanism for their corresponding disease profiles

    International Nuclear Information System (INIS)

    Rossi-George, A.; Virgolini, M.B.; Weston, D.; Cory-Slechta, D.A.

    2009-01-01

    Combined exposures to maternal lead (Pb) and prenatal stress (PS) can act synergistically to enhance behavioral and neurochemical toxicity in offspring. Maternal Pb itself causes permanent dysfunction of the body's major stress system, the hypothalamic pituitary adrenal (HPA) axis. The current study sought to determine the potential involvement of altered negative glucocorticoid feedback as a mechanistic basis of the effects in rats of maternal Pb (0, 50 or 150 ppm in drinking water beginning 2 mo prior to breeding), prenatal stress (PS; restraint on gestational days 16-17) and combined maternal Pb + PS in 8 mo old male and female offspring. Corticosterone changes were measured over 24 h following an i.p. injection stress containing vehicle or 100 or 300 μg/kg (females) or 100 or 150 μg/kg (males) dexamethasone (DEX). Both Pb and PS prolonged the time course of corticosterone reduction following vehicle injection stress. Pb effects were non-monotonic, with a greater impact at 50 vs. 150 ppm, particularly in males, where further enhancement occurred with PS. In accord with these findings, the efficacy of DEX in suppressing corticosterone was reduced by Pb and Pb + PS in both genders, with Pb efficacy enhanced by PS in females, over the first 6 h post-administration. A marked prolongation of DEX effects was found in males. Thus, Pb, PS and Pb + PS, sometimes additively, produced hypercortisolism in both genders, followed by hypocortisolism in males, consistent with HPA axis dysfunction. These findings may provide a plausible unifying biological mechanism for the reported links between Pb exposure and stress-associated diseases and disorders mediated via the HPA axis, including obesity, hypertension, diabetes, anxiety, schizophrenia and depression. They also suggest broadening of Pb screening programs to pregnant women in high stress environments

  3. SsaA, a Member of a Novel Class of Transcriptional Regulators, Controls Sansanmycin Production in Streptomyces sp. Strain SS through a Feedback Mechanism

    Science.gov (United States)

    Li, Qinglian; Wang, Lifei; Xie, Yunying; Wang, Songmei; Chen, Ruxian

    2013-01-01

    Sansanmycins, produced by Streptomyces sp. strain SS, are uridyl peptide antibiotics with activities against Pseudomonas aeruginosa and multidrug-resistant Mycobacterium tuberculosis. In this work, the biosynthetic gene cluster of sansanmycins, comprised of 25 open reading frames (ORFs) showing considerable amino acid sequence identity to those of the pacidamycin and napsamycin gene cluster, was identified. SsaA, the archetype of a novel class of transcriptional regulators, was characterized in the sansanmycin gene cluster, with an N-terminal fork head-associated (FHA) domain and a C-terminal LuxR-type helix-turn-helix (HTH) motif. The disruption of ssaA abolished sansanmycin production, as well as the expression of the structural genes for sansanmycin biosynthesis, indicating that SsaA is a pivotal activator for sansanmycin biosynthesis. SsaA was proved to directly bind several putative promoter regions of biosynthetic genes, and comparison of sequences of the binding sites allowed the identification of a consensus SsaA binding sequence, GTMCTGACAN2TGTCAGKAC. The DNA binding activity of SsaA was inhibited by sansanmycins A and H in a concentration-dependent manner. Furthermore, sansanmycins A and H were found to directly interact with SsaA. These results indicated that SsaA strictly controls the production of sansanmycins at the transcriptional level in a feedback regulatory mechanism by sensing the accumulation of the end products. As the first characterized regulator of uridyl peptide antibiotic biosynthesis, the understanding of this autoregulatory process involved in sansanmycin biosynthesis will likely provide an effective strategy for rational improvements in the yields of these uridyl peptide antibiotics. PMID:23475969

  4. Feedback: How to Teach How.

    Science.gov (United States)

    Krovar, Susan K.; And Others

    1992-01-01

    To give definitive feedback, physical education teachers must be able to teach basic kinesiological and mechanical principles of movement and how they apply to specific sports skills. The article includes a chart with common kinesiological and mechanical principles applied to particular movements. Appropriate teaching cues are noted. (SM)

  5. Effects of strong earthquakes in variations of electrical and meteorological parameters of the near-surface atmosphere in Kamchatka region

    Science.gov (United States)

    Smirnov, S. E.; Mikhailova, G. A.; Mikhailov, Yu. M.; Kapustina, O. V.

    2017-09-01

    The diurnal variations in electrical (quasistatic electric field and electrical conductivity) and meteorological (temperature, pressure, relative humidity of the atmosphere, and wind speed) parameters, measured simultaneously before strong earthquakes in Kamchatka region (November 15, 2006, M = 8.3; January 13, 2007, M = 8.1; January 30, 2016, M = 7.2), are studied for the first time in detail. It is found that a successively anomalous increase in temperature, despite the negative regular trend in these winter months, was observed in the period of six-seven days before the occurrences of earthquakes. An anomalous temperature increase led to the formation of "winter thunderstorm" conditions in the near-surface atmosphere of Kamchatka region, which was manifested in the appearance of an anomalous, type 2 electrical signal, the amplification of and intensive variations in electrical conductivity, heavy precipitation (snow showers), high relative humidity of air, storm winds, and pressure changes. With the weak flow of natural heat radiation in this season, the observed dynamics of electric and meteorological processes can likely be explained by the appearance of an additional heat source of seismic nature.

  6. Beryllium-7 in near-surface atmospheric aerosols in mid-latitude (40 deg N) city Beijing, China

    International Nuclear Information System (INIS)

    Keyan Tan; Yongliang Yang; Xiaohua Zhu; Shu Chen; Xingchun Jiao; Nan Gai; Yi Huang

    2013-01-01

    A high-volume air sampler and a high-resolution gamma-ray spectrometer have been used to measure the activity of 7 Be in near-surface atmospheric aerosols at sampling frequency of 3 days week for 1 year from August 2009 to July 2010 at Beijing in the mid-latitude region of East Asia monsoon. The measurements indicate that the average concentration of 7 Be was 8.39 ± 0.49 mBq m -3 , which was significantly higher than values reported for other cities in the East Asia monsoon region and in the world during the same period. The maximum and minimum of the weekly means of 7 Be concentration were observed in September and May, respectively. The 7 Be concentrations varied in accordance with the monsoon phases. Low but frequent wet precipitation may have caused lower 7 Be observed in July when southeasterly was prevailing. Higher seasonal mean of 7 Be concentrations in autumn could be attributed to the abnormal atmospheric circulation in autumn 2009. (author)

  7. An automated analyzer to measure surface-atmosphere exchange fluxes of water soluble inorganic aerosol compounds and reactive trace gases.

    Science.gov (United States)

    Thomas, Rick M; Trebs, Ivonne; Otjes, René; Jongejan, Piet A C; Ten Brink, Harry; Phillips, Gavin; Kortner, Michael; Meixner, Franz X; Nemitz, Eiko

    2009-03-01

    Here, we present a new automated instrument for semicontinuous gradient measurements of water-soluble reactive trace gas species (NH3, HNO3, HONO, HCl, and SO2) and their related aerosol compounds (NH4+, NO3-, Cl-, SO4(2-)). Gas and aerosol samples are collected simultaneously at two heights using rotating wet-annular denuders and steam-jet aerosol collectors, respectively. Online (real-time) analysis using ion chromatography (IC) for anions and flow injection analysis (FIA) for NH4+ and NH3 provide a half-hourly averaged gas and aerosol gradients within each hour. Through the use of syringe pumps, IC preconcentration columns, and high-quality purified water, the system achieves detection limits (3sigma-definition) under field conditions of typically: 136/207,135/114, 29/ 22,119/92, and 189/159 ng m(-3) for NH3/NH4+, HNO3/NO3-, HONO/ NO2-, HCl/Cl- and SO2/SO4(2-), respectively. The instrument demonstrates very good linearity and accuracy for liquid and selected gas phase calibrations over typical ambient concentration ranges. As shown by examples from field experiments, the instrument provides sufficient precision (3-9%), even at low ambient concentrations, to resolve vertical gradients and calculate surface-atmosphere exchange fluxes undertypical meteorological conditions of the atmospheric surface layer using the aerodynamic gradient technique.

  8. Cortical electrophysiological network dynamics of feedback learning

    NARCIS (Netherlands)

    Cohen, M.X.; Wilmes, K.A.; van de Vijver, I.

    2011-01-01

    Understanding the neurophysiological mechanisms of learning is important for both fundamental and clinical neuroscience. We present a neurophysiologically inspired framework for understanding cortical mechanisms of feedback-guided learning. This framework is based on dynamic changes in systems-level

  9. Litter feedbacks, evolutionary change and exotic plant

    NARCIS (Netherlands)

    Eppinga, M.B.; Kaproth, M.A.; Collins, A.R.; Molofsky, J.

    2011-01-01

    1. Understanding the mechanisms driving exotic plant invasions is important for designing successful invader control strategies. Previous studies have highlighted different invasion mechanisms, including alteration of nutrient cycles through plant–soil feedback and evolutionary change toward more

  10. Use of the learning conversation improves instructor confidence in life support training: An open randomised controlled cross-over trial comparing teaching feedback mechanisms.

    Science.gov (United States)

    Baldwin, Lydia J L; Jones, Christopher M; Hulme, Jonathan; Owen, Andrew

    2015-11-01

    Feedback is vital for the effective delivery of skills-based education. We sought to compare the sandwich technique and learning conversation structured methods of feedback delivery in competency-based basic life support (BLS) training. Open randomised crossover study undertaken between October 2014 and March 2015 at the University of Birmingham, United Kingdom. Six-hundred and forty healthcare students undertaking a European Resuscitation Council (ERC) BLS course were enrolled, each of whom was randomised to receive teaching using either the sandwich technique or the learning conversation. Fifty-eight instructors were randomised to initially teach using either the learning conversation or sandwich technique, prior to crossing-over and teaching with the alternative technique after a pre-defined time period. Outcome measures included skill acquisition as measured by an end-of-course competency assessment, instructors' perception of teaching with each feedback technique and candidates' perception of the feedback they were provided with. Scores assigned to use of the learning conversation by instructors were significantly more favourable than for the sandwich technique across all but two assessed domains relating to instructor perception of the feedback technique, including all skills-based domains. No difference was seen in either assessment pass rates (80.9% sandwich technique vs. 77.2% learning conversation; OR 1.2, 95% CI 0.85-1.84; p=0.29) or any domain relating to candidates' perception of their teaching technique. This is the first direct comparison of two feedback techniques in clinical medical education using both quantitative and qualitative methodology. The learning conversation is preferred by instructors providing competency-based life support training and is perceived to favour skills acquisition. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  11. Self-regulated growth of supermassive black holes by a dual jet-heating active galactic nucleus feedback mechanism: methods, tests and implications for cosmological simulations

    Science.gov (United States)

    Dubois, Yohan; Devriendt, Julien; Slyz, Adrianne; Teyssier, Romain

    2012-03-01

    We develop a subgrid model for the growth of supermassive black holes (BHs) and their associated active galactic nucleus (AGN) feedback in hydrodynamical cosmological simulations. This model transposes previous attempts to describe BH accretion and AGN feedback with the smoothed particle hydrodynamics (SPH) technique to the adaptive mesh refinement framework. It also furthers their development by implementing a new jet-like outflow treatment of the AGN feedback which we combine with the heating mode traditionally used in the SPH approach. Thus, our approach allows one to test the robustness of the conclusions derived from simulating the impact of self-regulated AGN feedback on galaxy formation vis-à-vis the numerical method. Assuming that BHs are created in the early stages of galaxy formation, they grow by mergers and accretion of gas at a Eddington-limited Bondi accretion rate. However this growth is regulated by AGN feedback which we model using two different modes: a quasar-heating mode when accretion rates on to the BHs are comparable to the Eddington rate, and a radio-jet mode at lower accretion rates which not only deposits energy, but also deposits mass and momentum on the grid. In other words, our feedback model deposits energy as a succession of thermal bursts and jet outflows depending on the properties of the gas surrounding the BHs. We assess the plausibility of such a model by comparing our results to observational measurements of the co-evolution of BHs and their host galaxy properties, and check their robustness with respect to numerical resolution. We show that AGN feedback must be a crucial physical ingredient for the formation of massive galaxies as it appears to be able to efficiently prevent the accumulation of and/or expel cold gas out of haloes/galaxies and significantly suppress star formation. Our model predicts that the relationship between BHs and their host galaxy mass evolves as a function of redshift, because of the vigorous accretion

  12. Spatially explicit simulation of hydrologically controlled carbon and nitrogen cycles and associated feedback mechanisms in a boreal ecosystem in Eastern Canada.

    Science.gov (United States)

    Govind, A.; Chen, J. M.; Margolis, H.

    2007-12-01

    respiration and the resultant nitrogen mineralization which affects GPP and several other feedback mechanisms. These results suggest that lateral water flow does play a significant role in the terrestrial carbon distribution. Therefore, regional or global scale terrestrial carbon estimates could have significant errors if proper hydrological constrains are not considered for modeling ecological processes due to large topographic variations on the Earth's surface. For more info please visit: http://ajit.govind.googlepages.com/agu2007

  13. Reviews and syntheses: An empirical spatiotemporal description of the global surface-atmosphere carbon fluxes: opportunities and data limitations

    Science.gov (United States)

    Zscheischler, Jakob; Mahecha, Miguel D.; Avitabile, Valerio; Calle, Leonardo; Carvalhais, Nuno; Ciais, Philippe; Gans, Fabian; Gruber, Nicolas; Hartmann, Jens; Herold, Martin; Ichii, Kazuhito; Jung, Martin; Landschützer, Peter; Laruelle, Goulven G.; Lauerwald, Ronny; Papale, Dario; Peylin, Philippe; Poulter, Benjamin; Ray, Deepak; Regnier, Pierre; Rödenbeck, Christian; Roman-Cuesta, Rosa M.; Schwalm, Christopher; Tramontana, Gianluca; Tyukavina, Alexandra; Valentini, Riccardo; van der Werf, Guido; West, Tristram O.; Wolf, Julie E.; Reichstein, Markus

    2017-08-01

    Understanding the global carbon (C) cycle is of crucial importance to map current and future climate dynamics relative to global environmental change. A full characterization of C cycling requires detailed information on spatiotemporal patterns of surface-atmosphere fluxes. However, relevant C cycle observations are highly variable in their coverage and reporting standards. Especially problematic is the lack of integration of the carbon dioxide (CO2) exchange of the ocean, inland freshwaters and the land surface with the atmosphere. Here we adopt a data-driven approach to synthesize a wide range of observation-based spatially explicit surface-atmosphere CO2 fluxes from 2001 to 2010, to identify the state of today's observational opportunities and data limitations. The considered fluxes include net exchange of open oceans, continental shelves, estuaries, rivers, and lakes, as well as CO2 fluxes related to net ecosystem productivity, fire emissions, loss of tropical aboveground C, harvested wood and crops, as well as fossil fuel and cement emissions. Spatially explicit CO2 fluxes are obtained through geostatistical and/or remote-sensing-based upscaling, thereby minimizing biophysical or biogeochemical assumptions encoded in process-based models. We estimate a bottom-up net C exchange (NCE) between the surface (land, ocean, and coastal areas) and the atmosphere. Though we provide also global estimates, the primary goal of this study is to identify key uncertainties and observational shortcomings that need to be prioritized in the expansion of in situ observatories. Uncertainties for NCE and its components are derived using resampling. In many regions, our NCE estimates agree well with independent estimates from other sources such as process-based models and atmospheric inversions. This holds for Europe (mean ± 1 SD: 0.8 ± 0.1 PgC yr-1, positive numbers are sources to the atmosphere), Russia (0.1 ± 0.4 PgC yr-1), East Asia (1.6 ± 0.3 PgC yr-1), South Asia (0.3 ± 0

  14. Skriftlig feedback i engelskundervisningen

    DEFF Research Database (Denmark)

    Kjærgaard, Hanne Wacher

    2017-01-01

    The article describes useful feedback strategies in language teaching and describes the feedback practices of lower-seconday teachers in Denmark. The article is aimed at language teahcers in secondary schools.......The article describes useful feedback strategies in language teaching and describes the feedback practices of lower-seconday teachers in Denmark. The article is aimed at language teahcers in secondary schools....

  15. Student Engagement with Feedback

    Science.gov (United States)

    Scott, Jon; Shields, Cathy; Gardner, James; Hancock, Alysoun; Nutt, Alex

    2011-01-01

    This report considers Biological Sciences students' perceptions of feedback, compared with those of the University as a whole, this includes what forms of feedback were considered most useful and how feedback used. Compared with data from previous studies, Biological Sciences students gave much greater recognition to oral feedback, placing it on a…

  16. Computer-Generated Feedback on Student Writing

    Science.gov (United States)

    Ware, Paige

    2011-01-01

    A distinction must be made between "computer-generated scoring" and "computer-generated feedback". Computer-generated scoring refers to the provision of automated scores derived from mathematical models built on organizational, syntactic, and mechanical aspects of writing. In contrast, computer-generated feedback, the focus of this article, refers…

  17. Driver feedback mobile APP

    Energy Technology Data Exchange (ETDEWEB)

    Soriguera Marti, F.; Miralles Miquel, E.

    2016-07-01

    This paper faces the human factor in driving and its consequences for road safety. It presents the concepts behind the development of a smartphone app capable of evaluating drivers’ performance. The app provides feedback to the driver in terms of a grade (between 0 and 10) depending on the aggressiveness and risks taken while driving. These are computed from the cumulative probability distribution function of the jerks (i.e. the time derivative of acceleration), which are measured using the smartphones’ accelerometer. Different driving contexts (e.g. urban, freeway, congestion, etc.) are identified applying cluster analysis to the measurements, and treated independently. Using regression analysis, the aggressiveness indicator is related to the drivers' safety records and to the probability of having an accident, through the standard DBQ - Driving Behavior Questionnaire. Results from a very limited pilot test show a strong correlation between the 99th percentile of the jerk measurements and the DBQ results. A linear model is fitted. This allows quantifying the safe driving behavior only from smartphone measurements. Finally, this indicator is translated into a normalized grade and feedback to the driver. This feedback will challenge the driver to train and to improve his performance. The phone will be blocked while driving and will incorporate mechanisms to prevent bad practices, like competition in aggressive driving. The app is intended to contribute to the improvement of road safety, one of the major public health problems, by tackling the human factor which is the trigger of the vast majority of traffic accidents. Making explicit and quantifying risky behaviors is the first step towards a safer driving. (Author)

  18. Feedback on Feedback--Does It Work?

    Science.gov (United States)

    Speicher, Oranna; Stollhans, Sascha

    2015-01-01

    It is well documented that providing assessment feedback through the medium of screencasts is favourably received by students and encourages deeper engagement with the feedback given by the language teacher (inter alia Abdous & Yoshimura, 2010; Brick & Holmes, 2008; Cann, 2007; Stannard, 2007). In this short paper we will report the…

  19. Pulsed feedback defers cellular differentiation.

    Directory of Open Access Journals (Sweden)

    Joe H Levine

    2012-01-01

    Full Text Available Environmental signals induce diverse cellular differentiation programs. In certain systems, cells defer differentiation for extended time periods after the signal appears, proliferating through multiple rounds of cell division before committing to a new fate. How can cells set a deferral time much longer than the cell cycle? Here we study Bacillus subtilis cells that respond to sudden nutrient limitation with multiple rounds of growth and division before differentiating into spores. A well-characterized genetic circuit controls the concentration and phosphorylation of the master regulator Spo0A, which rises to a critical concentration to initiate sporulation. However, it remains unclear how this circuit enables cells to defer sporulation for multiple cell cycles. Using quantitative time-lapse fluorescence microscopy of Spo0A dynamics in individual cells, we observed pulses of Spo0A phosphorylation at a characteristic cell cycle phase. Pulse amplitudes grew systematically and cell-autonomously over multiple cell cycles leading up to sporulation. This pulse growth required a key positive feedback loop involving the sporulation kinases, without which the deferral of sporulation became ultrasensitive to kinase expression. Thus, deferral is controlled by a pulsed positive feedback loop in which kinase expression is activated by pulses of Spo0A phosphorylation. This pulsed positive feedback architecture provides a more robust mechanism for setting deferral times than constitutive kinase expression. Finally, using mathematical modeling, we show how pulsing and time delays together enable "polyphasic" positive feedback, in which different parts of a feedback loop are active at different times. Polyphasic feedback can enable more accurate tuning of long deferral times. Together, these results suggest that Bacillus subtilis uses a pulsed positive feedback loop to implement a "timer" that operates over timescales much longer than a cell cycle.

  20. Perceiving haptic feedback in virtual reality simulators.

    Science.gov (United States)

    Våpenstad, Cecilie; Hofstad, Erlend Fagertun; Langø, Thomas; Mårvik, Ronald; Chmarra, Magdalena Karolina

    2013-07-01

    To improve patient safety, training of psychomotor laparoscopic skills is often done on virtual reality (VR) simulators outside the operating room. Haptic sensations have been found to influence psychomotor performance in laparoscopy. The emulation of haptic feedback is thus an important aspect of VR simulation. Some VR simulators try to simulate these sensations with handles equipped with haptic feedback. We conducted a survey on how laparoscopic surgeons perceive handles with and without haptic feedback. Surgeons with different levels of experience in laparoscopy were asked to test two handles: Xitact IHP with haptic feedback and Xitact ITP without haptic feedback (Mentice AB, Gothenburg, Sweden), connected to the LapSim (Surgical Science AB, Sweden) VR simulator. They performed two tasks on the simulator before answering 12 questions regarding the two handles. The surgeons were not informed about the differences in the handles. A total of 85 % of the 20 surgeons who participated in the survey claimed that it is important that handles with haptic feedback feel realistic. Ninety percent of the surgeons preferred the handles without haptic feedback. The friction in the handles with haptic feedback was perceived to be as in reality (5 %) or too high (95 %). Regarding the handles without haptic feedback, the friction was perceived as in reality (45 %), too low (50 %), or too high (5 %). A total of 85 % of the surgeons thought that the handle with haptic feedback attempts to simulate the resistance offered by tissue to deformation. Ten percent thought that the handle succeeds in doing so. The surveyed surgeons believe that haptic feedback is an important feature on VR simulators; however, they preferred the handles without haptic feedback because they perceived the handles with haptic feedback to add additional friction, making them unrealistic and not mechanically transparent.

  1. Rateless feedback codes

    DEFF Research Database (Denmark)

    Sørensen, Jesper Hemming; Koike-Akino, Toshiaki; Orlik, Philip

    2012-01-01

    This paper proposes a concept called rateless feedback coding. We redesign the existing LT and Raptor codes, by introducing new degree distributions for the case when a few feedback opportunities are available. We show that incorporating feedback to LT codes can significantly decrease both...... the coding overhead and the encoding/decoding complexity. Moreover, we show that, at the price of a slight increase in the coding overhead, linear complexity is achieved with Raptor feedback coding....

  2. The Mythology of Feedback

    Science.gov (United States)

    Adcroft, Andy

    2011-01-01

    Much of the general education and discipline-specific literature on feedback suggests that it is a central and important element of student learning. This paper examines feedback from a social process perspective and suggests that feedback is best understood through an analysis of the interactions between academics and students. The paper argues…

  3. Fault Tolerant Feedback Control

    DEFF Research Database (Denmark)

    Stoustrup, Jakob; Niemann, H.

    2001-01-01

    An architecture for fault tolerant feedback controllers based on the Youla parameterization is suggested. It is shown that the Youla parameterization will give a residual vector directly in connection with the fault diagnosis part of the fault tolerant feedback controller. It turns out...... that there is a separation be-tween the feedback controller and the fault tolerant part. The closed loop feedback properties are handled by the nominal feedback controller and the fault tolerant part is handled by the design of the Youla parameter. The design of the fault tolerant part will not affect the design...

  4. Feedback and Incentives

    DEFF Research Database (Denmark)

    Eriksson, Tor Viking; Poulsen, Anders; Villeval, Marie Claire

    2009-01-01

    This paper experimentally investigates the impact of different pay schemes and relative performance feedback policies on employee effort. We explore three feedback rules: no feedback on relative performance, feedback given halfway through the production period, and continuously updated feedback. We...... use two pay schemes, a piece rate and a tournament. We find that overall feedback does not improve performance. In contrast to the piece-rate pay scheme there is some evidence of positive peer effects in tournaments since the underdogs almost never quit the competition even when lagging significantly...... behind, and front runners do not slack off. But in both pay schemes relative performance feedback reduces the quality of the low performers' work; we refer to this as a "negative quality peer effect"....

  5. The development of a thermal hydraulic feedback mechanism with a quasi-fixed point iteration scheme for control rod position modeling for the TRIGSIMS-TH application

    Science.gov (United States)

    Karriem, Veronica V.

    Nuclear reactor design incorporates the study and application of nuclear physics, nuclear thermal hydraulic and nuclear safety. Theoretical models and numerical methods implemented in computer programs are utilized to analyze and design nuclear reactors. The focus of this PhD study's is the development of an advanced high-fidelity multi-physics code system to perform reactor core analysis for design and safety evaluations of research TRIGA-type reactors. The fuel management and design code system TRIGSIMS was further developed to fulfill the function of a reactor design and analysis code system for the Pennsylvania State Breazeale Reactor (PSBR). TRIGSIMS, which is currently in use at the PSBR, is a fuel management tool, which incorporates the depletion code ORIGEN-S (part of SCALE system) and the Monte Carlo neutronics solver MCNP. The diffusion theory code ADMARC-H is used within TRIGSIMS to accelerate the MCNP calculations. It manages the data and fuel isotopic content and stores it for future burnup calculations. The contribution of this work is the development of an improved version of TRIGSIMS, named TRIGSIMS-TH. TRIGSIMS-TH incorporates a thermal hydraulic module based on the advanced sub-channel code COBRA-TF (CTF). CTF provides the temperature feedback needed in the multi-physics calculations as well as the thermal hydraulics modeling capability of the reactor core. The temperature feedback model is using the CTF-provided local moderator and fuel temperatures for the cross-section modeling for ADMARC-H and MCNP calculations. To perform efficient critical control rod calculations, a methodology for applying a control rod position was implemented in TRIGSIMS-TH, making this code system a modeling and design tool for future core loadings. The new TRIGSIMS-TH is a computer program that interlinks various other functional reactor analysis tools. It consists of the MCNP5, ADMARC-H, ORIGEN-S, and CTF. CTF was coupled with both MCNP and ADMARC-H to provide the

  6. The inhibitory effects of AR/miR-190a/YB-1 negative feedback loop on prostate cancer and underlying mechanism.

    Science.gov (United States)

    Xu, Shaohua; Wang, Tao; Song, Wen; Jiang, Tao; Zhang, Feng; Yin, Yu; Jiang, Shi-Wen; Wu, Kongming; Yu, Zuoren; Wang, Chenguang; Chen, Ke

    2015-08-28

    Prostate cancer at advanced stages including metastatic and castration-resistant cancer remains incurable due to the lack of effective therapies. MiR-190a belongs to the small noncoding RNA family and has an important role in breast cancer metastasis. However, it is still unknown whether miR-190a plays a role in prostate cancer development. Herein, we first observed AR/miR-190a/YB-1 forms an auto-regulatory negative feedback loop in prostate cancer: miR-190a expression was down-regulated by AR activation; YB-1 functions are as an AR activator; miR-190a inhibited AR expression and transactivation through direct binding to 3'UTR of YB-1 gene. MiR-190a contributes the human prostate cancer cell growth through AR-dependent signaling. Moreover, we examined the expression of miR-190a and observed a significant decrease in human prostate cancers. Reduced expression of miR-190a was inversely correlated to AR levels of prostate cancer patients, and patients with higher miR-190a expression in their tumor have improved tumor-free survival. Taken together, our findings identified a biochemical and functional link between miR-190a with reduced expression in advanced prostate cancer, YB-1 and AR signaling in prostate cancer.

  7. Investigation of Laser Induced Breakdown Spectroscopy (LIBS) for the Differentiation of Nerve and Gland Tissue—A Possible Application for a Laser Surgery Feedback Control Mechanism

    Science.gov (United States)

    Mehari, F.; Rohde, M.; Knipfer, C.; Kanawade, R.; Klämpfl, F.; W., Adler; Oetter, N.; Stelzle, F.; Schmidt, M.

    2016-06-01

    Laser surgery provides clean, fast and accurate modeling of tissue. However, the inability to determine what kind of tissue is being ablated at the bottom of the cut may lead to the iatrogenic damage of structures that were meant to be preserved. In this context, nerve preservation is one of the key challenges in any surgical procedure. One example is the treatment of parotid gland pathologies, where the facial nerve (N. VII) and its main branches run through and fan out inside the glands parenchyma. A feedback system that automatically stops the ablation to prevent nerve-tissue damage could greatly increase the applicability and safety of surgical laser systems. In the present study, Laser Induced Breakdown Spectroscopy (LIBS) is used to differentiate between nerve and gland tissue of an ex-vivo pig animal model. The LIBS results obtained in this preliminary experiment suggest that the measured spectra, containing atomic and molecular emissions, can be used to differentiate between the two tissue types. The measurements and differentiation were performed in open air and under normal stray light conditions.

  8. Laser induced breakdown spectroscopy for bone and cartilage differentiation - ex vivo study as a prospect for a laser surgery feedback mechanism.

    Science.gov (United States)

    Mehari, Fanuel; Rohde, Maximilian; Knipfer, Christian; Kanawade, Rajesh; Klämpfl, Florian; Adler, Werner; Stelzle, Florian; Schmidt, Michael

    2014-11-01

    Laser surgery enables for very accurate, fast and clean modeling of tissue. The specific and controlled cutting and ablation of tissue, however, remains a central challenge in the field of clinical laser applications. The lack of information on what kind of tissue is being ablated at the bottom of the cut may lead to iatrogenic damage of structures that were meant to be preserved. One such example is the shaping or removal of diseased cartilaginous and bone tissue in the temporomandibular joint (TMJ). Diseases of the TMJ can induce deformation and perforation of the cartilaginous discus articularis, as well as alterations to the cartilaginous surface of the condyle or even the bone itself. This may result in restrictions of movement and pain. The aim of a surgical intervention ranges from specific ablation and shaping of diseased cartilage, bone or synovial tissues to extensive removal of TMJ structures. One approach to differentiate between these tissues is to use Laser Induced Breakdown Spectroscopy (LIBS). The ultimate goal is a LIBS guided feedback control system for surgical laser systems that enables real-time tissue identification for tissue specific ablation. In the presented study, the authors focused on the LIBS based differentiation between cartilage tissue and cortical bone tissue using an ex-vivo pig model.

  9. RF feedback for KEKB

    Energy Technology Data Exchange (ETDEWEB)

    Ezura, Eizi; Yoshimoto, Shin-ichi; Akai, Kazunori [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

    1996-08-01

    This paper describes the present status of the RF feedback development for the KEK B-Factory (KEKB). A preliminary experiment concerning the RF feedback using a parallel comb-filter was performed through a choke-mode cavity and a klystron. The RF feedback has been tested using the beam of the TRISTAN Main Ring, and has proved to be effective in damping the beam instability. (author)

  10. Cholesterol-induced conformational changes in the sterol-sensing domain of the Scap protein suggest feedback mechanism to control cholesterol synthesis.

    Science.gov (United States)

    Gao, Yansong; Zhou, Yulian; Goldstein, Joseph L; Brown, Michael S; Radhakrishnan, Arun

    2017-05-26

    Scap is a polytopic protein of endoplasmic reticulum (ER) membranes that transports sterol regulatory element-binding proteins to the Golgi complex for proteolytic activation. Cholesterol accumulation in ER membranes prevents Scap transport and decreases cholesterol synthesis. Previously, we provided evidence that cholesterol inhibition is initiated when cholesterol binds to loop 1 of Scap, which projects into the ER lumen. Within cells, this binding causes loop 1 to dissociate from loop 7, another luminal Scap loop. However, we have been unable to demonstrate this dissociation when we added cholesterol to isolated complexes of loops 1 and 7. We therefore speculated that the dissociation requires a conformational change in the intervening polytopic sequence separating loops 1 and 7. Here we demonstrate such a change using a protease protection assay in sealed membrane vesicles. In the absence of cholesterol, trypsin or proteinase K cleaved cytosolic loop 4, generating a protected fragment that we visualized with a monoclonal antibody against loop 1. When cholesterol was added to these membranes, cleavage in loop 4 was abolished. Because loop 4 is part of the so-called sterol-sensing domain separating loops 1 and 7, these results support the hypothesis that cholesterol binding to loop 1 alters the conformation of the sterol-sensing domain. They also suggest that this conformational change helps transmit the cholesterol signal from loop 1 to loop 7, thereby allowing separation of the loops and facilitating the feedback inhibition of cholesterol synthesis. These insights suggest a new structural model for cholesterol-mediated regulation of Scap activity. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  11. Feedback Synthesizes Neural Codes for Motion.

    Science.gov (United States)

    Clarke, Stephen E; Maler, Leonard

    2017-05-08

    In senses as diverse as vision, hearing, touch, and the electrosense, sensory neurons receive bottom-up input from the environment, as well as top-down input from feedback loops involving higher brain regions [1-4]. Through connectivity with local inhibitory interneurons, these feedback loops can exert both positive and negative control over fundamental aspects of neural coding, including bursting [5, 6] and synchronous population activity [7, 8]. Here we show that a prominent midbrain feedback loop synthesizes a neural code for motion reversal in the hindbrain electrosensory ON- and OFF-type pyramidal cells. This top-down mechanism generates an accurate bidirectional encoding of object position, despite the inability of the electrosensory afferents to generate a consistent bottom-up representation [9, 10]. The net positive activity of this midbrain feedback is additionally regulated through a hindbrain feedback loop, which reduces stimulus-induced bursting and also dampens the ON and OFF cell responses to interfering sensory input [11]. We demonstrate that synthesis of motion representations and cancellation of distracting signals are mediated simultaneously by feedback, satisfying an accepted definition of spatial attention [12]. The balance of excitatory and inhibitory feedback establishes a "focal" distance for optimized neural coding, whose connection to a classic motion-tracking behavior provides new insight into the computational roles of feedback and active dendrites in spatial localization [13, 14]. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Feedback stabilization initiative

    International Nuclear Information System (INIS)

    1997-06-01

    Much progress has been made in attaining high confinement regimes in magnetic confinement devices. These operating modes tend to be transient, however, due to the onset of MHD instabilities, and their stabilization is critical for improved performance at steady state. This report describes the Feedback Stabilization Initiative (FSI), a broad-based, multi-institutional effort to develop and implement methods for raising the achievable plasma betas through active MHD feedback stabilization. A key element in this proposed effort is the Feedback Stabilization Experiment (FSX), a medium-sized, national facility that would be specifically dedicated to demonstrating beta improvement in reactor relevant plasmas by using a variety of MHD feedback stabilization schemes

  13. Feedback stabilization initiative

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-06-01

    Much progress has been made in attaining high confinement regimes in magnetic confinement devices. These operating modes tend to be transient, however, due to the onset of MHD instabilities, and their stabilization is critical for improved performance at steady state. This report describes the Feedback Stabilization Initiative (FSI), a broad-based, multi-institutional effort to develop and implement methods for raising the achievable plasma betas through active MHD feedback stabilization. A key element in this proposed effort is the Feedback Stabilization Experiment (FSX), a medium-sized, national facility that would be specifically dedicated to demonstrating beta improvement in reactor relevant plasmas by using a variety of MHD feedback stabilization schemes.

  14. Policy Feedback System (PFS)

    Data.gov (United States)

    Social Security Administration — The Policy Feedback System (PFS) is a web application developed by the Office of Disability Policy Management Information (ODPMI) team that gathers empirical data...

  15. The influence of force feedback and visual feedback in grasping tissue laparoscopically.

    Science.gov (United States)

    Heijnsdijk, E A M; Pasdeloup, A; van der Pijl, A J; Dankelman, J; Gouma, D J

    2004-06-01

    Due to the limited force feedback provided by laparoscopic instruments, surgeons may have difficulty in applying the appropriate force on the tissue. The aim of this study was to determine the influence of force feedback and visual feedback on the exerted pinch force. A grasper with a force sensor in the jaws was developed. Subjects with and without laparoscopic experience grasped and pulled pig bowel with a force of 5 N. The applied pinch force was measured during tasks of 1-s and 1-min duration. Visual feedback was provided in half the measurements. Force feedback was adjusted by changing the mechanical efficiency of the forceps from 30% to 90%. The mean pinch force applied was 6.8 N (+/-0.5), whereas the force to prevent slippage was 3.0 N (+/-0.4). Improving the mechanical efficiency had no effect on the pinch force for the 1-s measurements. The amount of excessive pinch force when holding tissue for 1 min was lower at 30% mechanical efficiency compared with 90% (105% vs 131%, p = 0.04). The tissue slipped more often when the subject had no visual feedback (2% vs 8%, p = 0.02). Force feedback and visual feedback play a more limited role than expected in the task of grasping tissue with laparoscopic forceps.

  16. RHIC 10 Hz global orbit feedback system

    International Nuclear Information System (INIS)

    Michnoff, R.; Arnold, L.; Carboni, L.; Cerniglia, P.; Curcio, A.; DeSanto, L.; Folz, C.; Ho, C.; Hoff, L.; Hulsart, R.; Karl, R.; Luo, Y.; Liu, C.; MacKay, W.; Mahler, G.; Meng, W.; Mernick, K.; Minty, M.; Montag, C.; Olsen, R.; Piacentino, J.; Popken, P.; Przybylinski, R.; Ptitsyn, V.; Ritter, J.; Schoenfeld, R.; Thieberger, P.; Tuozzolo, J.; Weston, A.; White, J.; Ziminski, P.; Zimmerman, P.

    2011-01-01

    Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the horizontal beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including a local beam feedback system at each of the two experimental areas, reinforcing the magnet base support assembly, and a mechanical servo feedback system. However, the local feedback system was insufficient because perturbation amplitudes outside the experimental areas were still problematic, and the mechanical solutions are very expensive. A global 10 Hz orbit feedback system consisting of 36 beam position monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two 3.8 km circumference counter-rotating rings has been developed and commissioned in February 2011. A description of the system architecture and results with beam will be discussed.

  17. Feedback For Helpers

    Science.gov (United States)

    Stromer, Walter F.

    1975-01-01

    The author offers some feedback to those in the helping professions in three areas: (1) forms and letters; (2) jumping to conclusions; and (3) blaming and belittling, in hopes of stimulating more feedback as well as more positive ways of performing their services. (HMV)

  18. Feedback og interpersonel kommunikation

    DEFF Research Database (Denmark)

    Dindler, Camilla

    2016-01-01

    Som interpersonel kommunikationsform handler feedback om at observere, mærke og italesætte det, som handler om relationen mellem samtaleparterne mere end om samtaleemnet. Her er fokus på, hvad der siges og hvordan der kommunikeres sammen. Feedback er her ikke en korrigerende tilbagemelding til...

  19. Feedback i matematik

    DEFF Research Database (Denmark)

    Sortkær, Bent

    2017-01-01

    Feedback bliver i litteraturen igen og igen fremhævet som et af de mest effektive midler til at fremme elevers præstationer i skolen (Hartberg, Dobson, & Gran, 2012; Hattie & Timperley, 2007; Wiliam, 2015). Dette på trods af, at flere forskere påpeger, at feedback ikke altid er læringsfremmende...... (Hattie & Gan, 2011), og nogle endda viser, at feedback kan have en negativ virkning i forhold til præstationer (Kluger & DeNisi, 1996). Artiklen vil undersøge disse tilsyneladende modstridende resultater ved at stille spørgsmålet: Under hvilke forudsætninger virker feedback i matematik læringsfremmende......? Dette gøres ved at dykke ned i forskningslitteraturen omhandlende feedback ud fra en række temaer for på den måde at besvare ovenstående spørgsmål....

  20. Feedback and Incentives:

    DEFF Research Database (Denmark)

    Eriksson, Tor Viking; Poulsen, Anders; Villeval, Marie-Claire

    This paper experimentally investigates the impact of different pay and relative performance information policies on employee effort. We explore three information policies: No feedback about relative performance, feedback given halfway through the production period, and continuously updated feedback....... The pay schemes are a piece rate payment scheme and a winner-takes-all tournament. We find that, regardless of the pay scheme used, feedback does not improve performance. There are no significant peer effects in the piece-rate pay scheme. In contrast, in the tournament scheme we find some evidence...... of positive peer effects since the underdogs almost never quit the competition even when lagging significantly behind, and frontrunners do not slack off. Moreover, in both pay schemes information feedback reduces the quality of the low performers' work....

  1. Feedback Valence Affects Auditory Perceptual Learning Independently of Feedback Probability

    OpenAIRE

    Amitay, Sygal; Moore, David R.; Molloy, Katharine; Halliday, Lorna F.

    2015-01-01

    Previous studies have suggested that negative feedback is more effective in driving learning than positive feedback. We investigated the effect on learning of providing varying amounts of negative and positive feedback while listeners attempted to discriminate between three identical tones; an impossible task that nevertheless produces robust learning. Four feedback conditions were compared during training: 90% positive feedback or 10% negative feedback informed the participants that they wer...

  2. Audio Feedback to Physiotherapy Students for Viva Voce: How Effective Is "The Living Voice"?

    Science.gov (United States)

    Munro, Wendy; Hollingworth, Linda

    2014-01-01

    Assessment and feedback remains one of the categories that students are least satisfied with within the United Kingdom National Student Survey. The Student Charter promotes the use of various formats of feedback to enhance student learning. This study evaluates the use of audio MP3 as an alternative feedback mechanism to written feedback for…

  3. Metabolic effects of free fatty acids during endotoxaemia in a porcine model--free fatty acid inhibition of growth hormone secretion as a potential catabolic feedback mechanism.

    Science.gov (United States)

    Buhl, M; Gjedsted, J; Granfeldt, A; Larsen, P Ø; Schmitz, O; Tønnesen, E; Møller, N

    2010-05-01

    Critical illness and severe inflammation are catabolic states characterised by breakdown of tissue and protein stores, by increased levels of free fatty acids, and by insulin resistance. These metabolic features contribute to morbidity and mortality. Growth hormone and insulin are the two major anabolic hormones. The present study was designed to test whether increased levels of free fatty acids (i) inhibit growth hormone secretion and (ii) induce insulin resistance during acute endotoxin exposure in a porcine model of critical illness. We studied 20 pigs for 6 h during combined anaesthesia and endotoxin infusion and a hyperinsulinaemic glucose clamp to control glucose, insulin, and free fatty acid concentrations. Pigs were randomised to two different continuous infusion rates of Intralipid resulting in different, sustained, and elevated free fatty acid concentrations (1.63 mmol l(-1) vs. 0.58 mmol l(-1), p=0.0002). Concomitantly, we observed reduced growth hormone concentrations in the group with high free fatty acid concentrations (3.5 ng ml(-1) vs. 6.6 ng ml(-1), pfeedback mechanism whereby growth hormone induced-stimulation of free fatty acids release inhibit growth hormone secretion. This mechanism may further contribute to protein loss in critical illness. We found no evidence that the increment of plasma free fatty acids between groups contribute to insulin resistance in critical illness. Georg Thieme Verlag KG Stuttgart-New York.

  4. It's all about timing: An electrophysiological examination of feedback-based learning with immediate and delayed feedback.

    Science.gov (United States)

    Arbel, Yael; Hong, Lucia; Baker, Travis E; Holroyd, Clay B

    2017-05-01

    Feedback regarding an individual's action can occur immediately or with a temporal delay. Processing of feedback that varies in its delivery time is proposed to engage different brain mechanisms. fMRI data implicate the striatum in the processing of immediate feedback, and the medial temporal lobe (MTL) in the processing of delayed feedback. The present study offers an electrophysiological examination of feedback processing in the context of timing, by studying the effects of feedback timing on the feedback-related negativity (FRN), a product of the midbrain dopamine system, and elucidating whether the N170 ERP component could capture MTL activation associated with the processing of delayed feedback. Participants completed a word-object paired association learning task; they received feedback 500ms (immediate feedback condition) following a button press during the learning of two sets of 14 items, and at a delay of 6500ms (delayed feedback condition) during the learning of the other two sets. The results indicated that while learning outcomes did not differ under the two timing conditions, Event Related Potential (ERPs) pointed to differential activation of the examined ERP components. FRN amplitude was found to be larger following the immediate feedback condition when compared with the delayed feedback condition, and sensitive to valence and learning only under the immediate feedback condition. Additionally, the amplitude of the N170 was found larger following the delayed feedback condition when compared with the immediate feedback condition. Taken together, the findings of the present study support the contention that the processing of delayed feedback involves a shift away from midbrain dopamine activation to the recruitment of the MTL. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Feedback - fra et elevperspektiv

    DEFF Research Database (Denmark)

    Petersen, Benedikte Vilslev; Pedersen, Bent Sortkær

    Feedback bliver i litteraturen igen og igen fremhævet som et af de mest effektive midler til at fremme elevers præstationer i skolen (Hattie og Timperley, 2007). Andre studier er dog inde på at feedback ikke altid er læringsfremmende og nogle viser endda at feedback kan have en negativ virkning i...... forhold til præstationer (Kluger & DeNisi, 1996). I forsøget på at forklare hvordan og hvorfor feedback virker (forskelligt), er der undersøgt flere dimensioner og forhold omkring feedback (se bl.a. Black og Wiliam, 1998; Hattie og Timperley, 2007; Shute, 2008). Dog er der få studier der undersøger...... hvordan feedback opleves fra et elevperspektiv (Ruiz-Primo og Li, 2013). Samtidig er der i feedbacklitteraturen en mangel på kvalitative studier, der kommer tæt på fænomenet feedback, som det viser sig i klasserummet (Ruiz-Primo og Li, 2013) i naturlige omgivelser (Black og Wiliam, 1998), og hvordan...

  6. Feedback Loop Gains and Feedback Behavior (1996)

    DEFF Research Database (Denmark)

    Kampmann, Christian Erik

    2012-01-01

    elasticities. For illustration, the method is applied to a well-known system: the simple long-wave model. Because this model exhibits highly nonlinear behavior, it sheds light on the usefulness of linear methods to nonlinear system. The analysis leads to a more thorough and deeper understanding of the system......Linking feedback loops and system behavior is part of the foundation of system dynamics, yet the lack of formal tools has so far prevented a systematic application of the concept, except for very simple systems. Having such tools at their disposal would be a great help to analysts in understanding...... large, complicated simulation models. The paper applies tools from graph theory formally linking individual feedback loop strengths to the system eigenvalues. The significance of a link or a loop gain and an eigenvalue can be expressed in the eigenvalue elasticity, i.e., the relative change...

  7. Training effectiveness feedback

    International Nuclear Information System (INIS)

    Wiggin, N.A.

    1987-01-01

    A formal method of getting feedback about the job performance of employees is a necessary part of all the authors training programs. The formal process may prove to be inadequate if it is the only process in use. There are many ways and many opportunities to get good feedback about employee performance. It is important to document these methods and specific instances to supplement the more formalized process. The key is to identify them, encourage them, use them, and document the training actions that result from them. This paper describes one plant's method of getting feedback about performance of technicians in the field

  8. Brugbar peer feedback

    DEFF Research Database (Denmark)

    Hvass, Helle; Heger, Stine

    Studerende kan være medskabere af undervisning i akademisk skrivning, når de modtager og giver feedback til hinandens ufærdige akademiske tekster. Det ser vi i et udviklingsprojekt, hvor vi afprøver kollektive vejledningsformater. Vi har dog erfaret: 1. at studerende mangler træning i at give og ...... modtage feedback 2. at den manglende træning kan stå i vejen for realiseringen af læringspotentialet ved peer feedback....

  9. Nonlinear feedback control of multiple robot arms

    Science.gov (United States)

    Tarn, T. J.; Yun, X.; Bejczy, A. K.

    1987-01-01

    Multiple coordinated robot arms are modeled by considering the arms: (1) as closed kinematic chains, and (2) as a force constrained mechanical system working on the same object simultaneously. In both formulations a new dynamic control method is discussed. It is based on a feedback linearization and simultaneous output decoupling technique. Applying a nonlinear feedback and a nonlinear coordinate transformation, the complicated model of the multiple robot arms in either formulation is converted into a linear and output decoupled system. The linear system control theory and optimal control theory are used to design robust controllers in the task space. The first formulation has the advantage of automatically handling the coordination and load distribution among the robot arms. In the second formulation, by choosing a general output equation, researchers can superimpose the position and velocity error feedback with the force-torque error feedback in the task space simultaneously.

  10. Probabilistic models for feedback systems.

    Energy Technology Data Exchange (ETDEWEB)

    Grace, Matthew D.; Boggs, Paul T.

    2011-02-01

    In previous work, we developed a Bayesian-based methodology to analyze the reliability of hierarchical systems. The output of the procedure is a statistical distribution of the reliability, thus allowing many questions to be answered. The principal advantage of the approach is that along with an estimate of the reliability, we also can provide statements of confidence in the results. The model is quite general in that it allows general representations of all of the distributions involved, it incorporates prior knowledge into the models, it allows errors in the 'engineered' nodes of a system to be determined by the data, and leads to the ability to determine optimal testing strategies. In this report, we provide the preliminary steps necessary to extend this approach to systems with feedback. Feedback is an essential component of 'complexity' and provides interesting challenges in modeling the time-dependent action of a feedback loop. We provide a mechanism for doing this and analyze a simple case. We then consider some extensions to more interesting examples with local control affecting the entire system. Finally, a discussion of the status of the research is also included.

  11. Fuzzy logic-based risk of fall estimation using smartwatch data as a means to form an assistive feedback mechanism in everyday living activities.

    Science.gov (United States)

    Iakovakis, Dimitrios E; Papadopoulou, Fotini A; Hadjileontiadis, Leontios J

    2016-12-01

    This Letter aims to create a fuzzy logic-based assistive prevention tool for falls, based on accessible sensory technology, such as smartwatch, resulting in monitoring of the risk factors of falls caused by orthostatic hypotension (OH); a drop in systolic blood pressure (DSBP) >20 mmHg due to postural changes. Epidemiological studies have shown that OH is a high risk factor for falls and has a strong impact in quality of life (QoL) of the elderly's, especially for some cases such as Parkinsonians. Based on smartwatch data, it is explored here how statistical features of heart rate variability (HRV) can lead to DSBP prediction and estimation of the risk of fall. In this vein, a pilot study was conducted in collaboration with five Greek Parkinson's Foundation patients and ten healthy volunteers. Taking into consideration, the estimated DSBP and additional statistics of the user's medical/behavioural history, a fuzzy logic inference system was developed, to estimate the instantaneous risk of fall. The latter is fed back to the user with a mechanism chosen by him/her (i.e. vibration and/or sound), to prevent a possible fall, and also sent to the attentive carers and/or healthcare professionals for a home-based monitoring beyond the clinic. The proposed approach paves the way for effective exploitation of the contribution of smartwatch data, such as HRV, in the sustain of QoL in everyday living activities.

  12. Feedback Valence Affects Auditory Perceptual Learning Independently of Feedback Probability

    Science.gov (United States)

    Amitay, Sygal; Moore, David R.; Molloy, Katharine; Halliday, Lorna F.

    2015-01-01

    Previous studies have suggested that negative feedback is more effective in driving learning than positive feedback. We investigated the effect on learning of providing varying amounts of negative and positive feedback while listeners attempted to discriminate between three identical tones; an impossible task that nevertheless produces robust learning. Four feedback conditions were compared during training: 90% positive feedback or 10% negative feedback informed the participants that they were doing equally well, while 10% positive or 90% negative feedback informed them they were doing equally badly. In all conditions the feedback was random in relation to the listeners’ responses (because the task was to discriminate three identical tones), yet both the valence (negative vs. positive) and the probability of feedback (10% vs. 90%) affected learning. Feedback that informed listeners they were doing badly resulted in better post-training performance than feedback that informed them they were doing well, independent of valence. In addition, positive feedback during training resulted in better post-training performance than negative feedback, but only positive feedback indicating listeners were doing badly on the task resulted in learning. As we have previously speculated, feedback that better reflected the difficulty of the task was more effective in driving learning than feedback that suggested performance was better than it should have been given perceived task difficulty. But contrary to expectations, positive feedback was more effective than negative feedback in driving learning. Feedback thus had two separable effects on learning: feedback valence affected motivation on a subjectively difficult task, and learning occurred only when feedback probability reflected the subjective difficulty. To optimize learning, training programs need to take into consideration both feedback valence and probability. PMID:25946173

  13. NAIP 2015 Imagery Feedback

    Data.gov (United States)

    Farm Service Agency, Department of Agriculture — The NAIP 2015 Imagery Feedback web application allows users to make comments and observations about the quality of the 2015 National Agriculture Imagery Program...

  14. Feedback in analog circuits

    CERN Document Server

    Ochoa, Agustin

    2016-01-01

    This book describes a consistent and direct methodology to the analysis and design of analog circuits with particular application to circuits containing feedback. The analysis and design of circuits containing feedback is generally presented by either following a series of examples where each circuit is simplified through the use of insight or experience (someone else’s), or a complete nodal-matrix analysis generating lots of algebra. Neither of these approaches leads to gaining insight into the design process easily. The author develops a systematic approach to circuit analysis, the Driving Point Impedance and Signal Flow Graphs (DPI/SFG) method that does not require a-priori insight to the circuit being considered and results in factored analysis supporting the design function. This approach enables designers to account fully for loading and the bi-directional nature of elements both in the feedback path and in the amplifier itself, properties many times assumed negligible and ignored. Feedback circuits a...

  15. Feedback control for clinicians.

    Science.gov (United States)

    Dumont, Guy A

    2014-02-01

    Although feedback control and automation has revolutionized many fields of human activity, it has yet to have a significant impact on healthcare, particularly when a patient is in the loop. Although there have been a number of studies concerned with closed-loop control of anesthesia, they have yet to have an impact on clinical practice. For such systems to be successful, engineers and clinicians have to work hand in hand, for this they have to have a basic understanding of each other's fields. The goal of this paper is to introduce clinicians to basic concepts in control engineering, with an emphasis on the properties of feedback control. Concepts such as modelling for control, feedback and uncertainty, robustness, feedback controller such as proportional-integral-derivative control, predictive control and adaptive control are briefly reviewed. Finally we discuss the safety issues around closed-loop control and discuss ways by which safe control can be guaranteed.

  16. Staff education, regular sedation and analgesia quality feedback, and a sedation monitoring technology for improving sedation and analgesia quality for critically ill, mechanically ventilated patients: a cluster randomised trial.

    Science.gov (United States)

    Walsh, Timothy S; Kydonaki, Kalliopi; Antonelli, Jean; Stephen, Jacqueline; Lee, Robert J; Everingham, Kirsty; Hanley, Janet; Phillips, Emma C; Uutela, Kimmo; Peltola, Petra; Cole, Stephen; Quasim, Tara; Ruddy, James; McDougall, Marcia; Davidson, Alan; Rutherford, John; Richards, Jonathan; Weir, Christopher J

    2016-10-01

    Optimal sedation of patients in intensive care units (ICUs) requires the avoidance of pain, agitation, and unnecessary deep sedation, but these outcomes are challenging to achieve. Excessive sedation can prolong ICU stay, whereas light sedation can increase pain and frightening memories, which are commonly recalled by ICU survivors. We aimed to assess the effectiveness of three interventions to improve sedation and analgesia quality: an online education programme; regular feedback of sedation-analgesia quality data; and use of a novel sedation-monitoring technology (the Responsiveness Index [RI]). We did a cluster randomised trial in eight ICUs, which were randomly allocated to receive education alone (two ICUs), education plus sedation-analgesia quality feedback (two ICUs), education plus RI monitoring technology (two ICUs), or all three interventions (two ICUs). Randomisation was done with computer-generated random permuted blocks, stratified according to recruitment start date. A 45 week baseline period was followed by a 45 week intervention period, separated by an 8 week implementation period in which the interventions were introduced. ICU and research staff were not masked to study group assignment during the intervention period. All mechanically ventilated patients were potentially eligible. We assessed patients' sedation-analgesia quality for each 12 h period of nursing care, and sedation-related adverse events daily. Our primary outcome was the proportion of care periods with optimal sedation-analgesia, defined as being free from excessive sedation, agitation, poor limb relaxation, and poor ventilator synchronisation. Analysis used multilevel generalised linear mixed modelling to explore intervention effects in a single model taking clustering and patient-level factors into account. A concurrent mixed-methods process evaluation was undertaken to help understand the trial findings. The trial is registered with ClinicalTrials.gov, number NCT01634451. Between

  17. RTP/I Payload Type Definition for Feedback Tools

    OpenAIRE

    Vogel, Jürgen

    2001-01-01

    This document specifies an application-level protocol (i.e., payload type) for feedback tools using the Real Time Protocol for Distributed Interactive Media (RTP/I). RTP/I defines a standardized framing for the transmission of application data and provides protocol mechanisms that are universally needed for the class of distributed interactive media. A feedback tool is used in synchronous collaborative environments for permanent feedback about certain criteria (e.g., audio quality). This docu...

  18. Muscle involvement during intermittent contraction patterns with different target force feedback modes

    DEFF Research Database (Denmark)

    Sjøgaard, G; Jørgensen, L V; Ekner, D

    2000-01-01

    and following 30 min of intermittent contractions showed larger fatigue development with proprioceptive feedback than visual feedback. Also rating of perceived exertion increased more during proprioceptive feedback than visual feedback. This may in part be explained by small differences in the mechanics during......: Feedback mode significantly effects the muscle involvement and fatigue during intermittent contractions. RelevanceIntermittent contractions are common in many work places and various feedback modes are being given regarding work requirements. The choice of feedback may significantly affect the muscle load...... and consequently the development muscle fatigue and disorders....

  19. Mechanism

    Directory of Open Access Journals (Sweden)

    Yao Yu

    2010-01-01

    Full Text Available The kinematics analysis method of a novel 3-DOF wind tunnel mechanism based on cable-driven parallel mechanism is provided. Rodrigues' parameters are applied to express the transformation matrix of the wire-driven mechanism in the paper. The analytical forward kinematics model is described as three quadratic equations using three Rodridgues' parameters based on the fundamental theory of parallel mechanism. Elimination method is used to remove two of the variables, so that an eighth-order polynomial with one variable is derived. From the equation, the eight sets of Rodridgues' parameters and corresponding Euler angles for the forward kinematical problem can be obtained. In the end, numerical example of both forward and inverse kinematics is included to demonstrate the presented forward-kinematics solution method. The numerical results show that the method for the position analysis of this mechanism is effective.

  20. Modelling land surface - atmosphere interactions

    DEFF Research Database (Denmark)

    Rasmussen, Søren Højmark

    related to inaccurate land surface modelling, e.g. enhanced warm bias in warm dry summer months. Coupling the regional climate model to a hydrological model shows the potential of improving the surface flux simulations in dry periods and the 2 m air temperature in general. In the dry periods......The study is investigates modelling of land surface – atmosphere interactions in context of fully coupled climatehydrological model. With a special focus of under what condition a fully coupled model system is needed. Regional climate model inter-comparison projects as ENSEMBLES have shown bias...

  1. Modelling land surface - atmosphere interactions

    DEFF Research Database (Denmark)

    Rasmussen, Søren Højmark

    The study is investigates modelling of land surface – atmosphere interactions in context of fully coupled climatehydrological model. With a special focus of under what condition a fully coupled model system is needed. Regional climate model inter-comparison projects as ENSEMBLES have shown bias...

  2. A Remote Sensing Analysis on the Spatiotemporal Variation of Land Surface Albedo and Emissivity in South Florida: An Implication for Surface-Atmosphere Energy and Water Exchange

    Science.gov (United States)

    Kandel, H. P.; Melesse, A. M.

    2016-12-01

    Land use /land cover has wide range of impacts from surface energy budget to radiative forcing of climate change. This study aims to analyze the variation in two radiative properties, albedo and emissivity in South Florida landscape to investigate how radially distinct surfaces lead to a energy and moisture contrast on the near-surface atmosphere and eventually to surface-induced climate. Maps of land surface albedo and emissivity were prepared using algorithms that convert narrow-band spectral reflectance to total short-wave albedo, and vegetation index to emissivity from Landsat -5 TM images of several different summer dates. A comparative analysis was made using the zonal statistics in ArcGIS. Relatively higher albedos were found over cultivated and developed lands (0.17 - 0.21) than in forests and herbaceous wetland (0.09 - 0.16). The emissivities, on the other hand, are lower for developed and drained lands. Average albedo exhibits a slight increase whereas emissivity is found to be decreasing through time. Urban areas showing higher albedos, a unique occurrence in this landscape, store less short-wave radiation, however, their lower emissivities points to increased storage of long-wave radiation. The results imply that the emissivity perhaps play a dominant role in heat island development and initiation of local circulation in urbanized South Florida.

  3. Accountability and feedback, part IV: destructive feedback.

    Science.gov (United States)

    Harolds, Jay A

    2013-04-01

    There are times that feedback is destructive rather than helpful to the employee and the organization. Occasionally, this is deliberate, such as when a boss does not like someone for reasons that have nothing to do with his/her performance as an employee, or his/her character. More often, it is inadvertent. This could be due to erroneous information from others or the leader's failure to take the time to adequately observe or supervise others. It could also be due to a lack of understanding of the individual's communication style, or failure to take into account age, cultural, religious, or sex differences. This article addresses some of these issues and what to do about it.

  4. Feedback Specificity, Information Processing, and Transfer of Training

    Science.gov (United States)

    Goodman, Jodi S.; Wood, Robert E.; Chen, Zheng

    2011-01-01

    This study examines the effects of feedback specificity on transfer of training and the mechanisms through which feedback can enhance or inhibit transfer. We used concurrent verbal protocol methodology to elicit and operationalize the explicit information processing activities used by 48 trainees performing the Furniture Factory computer…

  5. Evolutionary selection of expectations in positive and negative feedback markets

    NARCIS (Netherlands)

    Anufriev, M.; Hommes, C.H.; Philipse, R.H.S.

    2010-01-01

    An economic environment is a feedback system, where dynamics of aggregate variables depend on individual expectations and also shape them. The type of feedback mechanism is crucial for the aggregate outcome. Experiments with human subjects (Heemeijer et al, 2009) have shown that price converges to

  6. Evolutionary selection of expectations in positive and negative feedback markets

    NARCIS (Netherlands)

    Anufriev, M.; Hommes, C.H.; Philipse, R.H.S.

    2013-01-01

    An economic environment is a feedback system, where the dynamics of aggregate variables depend on individual expectations and vice versa. The type of feedback mechanism is crucial for the aggregate outcome. Experiments with human subjects (Heemeijer et al., J Econ Dyn Control 33:1052-1072, 2009 )

  7. Portfolio, refleksion og feedback

    DEFF Research Database (Denmark)

    Hansen, Jens Jørgen; Qvortrup, Ane; Christensen, Inger-Marie F.

    2017-01-01

    Denne leder definerer indledningsvist begrebet portfolio og gør rede for anvendelsesmuligheder i en uddannelseskontekst. Dernæst behandles portfoliometodens kvalitet og effekt for læring og undervisning og de centrale begreber refleksion, progression og feedback præsenteres og diskuteres. Herefter...

  8. Feedback i undervisningen

    DEFF Research Database (Denmark)

    Kirkegaard, Preben Olund

    2015-01-01

    undervisningsdifferentiering, feedback på læreprocesser, formativ og summativ evaluering, observationer og analyse af undervisning samt lærernes teamsamarbejde herom. Praktikken udgør et særligt læringsrum i læreruddannelsen. Samspillet mellem studerende, praktiklærere og undervisere giver den studerende en unik mulighed...

  9. The Endogenous Feedback Network

    DEFF Research Database (Denmark)

    Augustenborg, Claudia Carrara

    2010-01-01

    proposals, it will first be considered the extents of their reciprocal compatibility, tentatively shaping an integrated, theoretical profile of consciousness. A new theory, the Endogenous Feedback Network (EFN) will consequently be introduced which, beside being able to accommodate the main tenets...

  10. Mechanics

    CERN Document Server

    Hartog, J P Den

    1961-01-01

    First published over 40 years ago, this work has achieved the status of a classic among introductory texts on mechanics. Den Hartog is known for his lively, discursive and often witty presentations of all the fundamental material of both statics and dynamics (and considerable more advanced material) in new, original ways that provide students with insights into mechanical relationships that other books do not always succeed in conveying. On the other hand, the work is so replete with engineering applications and actual design problems that it is as valuable as a reference to the practicing e

  11. Autoregulatory Feedback Mechanism of P38MAPK/Caspase-8 in Photodynamic Therapy-Hydrophilic/Lipophilic Tetra-α-(4-carboxyphenoxy Phthalocyanine Zinc-Induced Apoptosis of Human Hepatocellular Carcinoma Bel-7402 Cells

    Directory of Open Access Journals (Sweden)

    Yu Wang

    2014-01-01

    Full Text Available Photodynamic therapy (PDT is a novel and promising antitumor treatment. Our previous study showed that hydrophilic/lipophilic tetra-α-(4-carboxyphenoxy phthalocyanine zinc- (TαPcZn- mediated PDT (TαPcZn-PDT inhibits the proliferation of human hepatocellular carcinoma Bel-7402 cells by triggering apoptosis and arresting cell cycle. However, mechanisms of TαPcZn-PDT-induced apoptosis of Bel-7402 cells have not been fully clarified. In the present study, therefore, effect of TαPcZn-PDT on apoptosis, P38MAPK, p-P38MAPK, Caspase-8, Caspase-3, Bcl-2, Bid, Cytochrome c, and mitochondria membrane potential in Bel-7402 cells without or with P38MAPK inhibitor SB203580 or Caspase-8 inhibitor Ac-IEFD-CHO was investigated by haematoxylin and eosin (HE staining assay, flow cytometry analysis of annexin V-FITC/propidium iodide (PI double staining cells and 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide (JC-1, and immunoblot assay. We found that TαPcZn-PDT resulted in apoptosis induction, activation of P38MAPK, Caspase-8, Caspase-3, and Bid, downregulation of Bcl-2, release of Cytochrome c from mitochondria, and disruption of mitochondrial membrane potential in TαPcZn-PDT-treated Bel-7402 cells. In contrast, SB203580 or Ac-IEFD-CHO attenuated induction of apoptosis, activation of P38MAPK, Caspase-8, Caspase-3, and Bid, downregulation of Bcl-2, release of Cytochrome c from mitochondria, and disruption of mitochondrial membrane potential in TαPcZn-PDT-treated Bel-7402 cells. Taken together, we conclude that Caspase-3, Bcl-2, Bid, and mitochondria are involved in autoregulatory feedback of P38MAPK/Caspase-8 during TαPcZn-PDT-induced apoptosis of Bel-7402 cells.

  12. What higher education students do with teacher feedback: Feedback ...

    African Journals Online (AJOL)

    Feedback research, therefore, suggests a causal relationship between teacher feedback practices during text production, student attitude and writing performance. However, a four-year longitudinal study conducted at a higher education institution monitoring student perceptions of written feedback on essay drafts found that ...

  13. Online feedback op schriftelijk werk: betere feedback in minder tijd.

    NARCIS (Netherlands)

    van den Berg, B.A.M.; van der Hulst, M.E.

    2015-01-01

    Feedback is a powerful teaching technic to raise students’ performance, provided that the feedback is informative on how to improve, is given in a timely manner and students have the opportunity to act upon it. Therefore, many institutions want their students to receive feedback on their performance

  14. Climate stability and cloud optical thickness feedbacks

    Science.gov (United States)

    Somerville, Richard C. J.; Iacobellis, Sam

    1989-01-01

    An improved radiative-convective model (RCM) has been developed and used to examine the role of cirrus clouds in the optical thickness feedback mechanism. Low and middle clouds are approximately black bodies for infrared radiative transfer, and so any increase in their optical thickness primarily increases the cloud albedo. Thus, if a climate warming is accompanied by an increase in average atmospheric absolute humidity and hence in average cloud liquid water content, low and middle cloud optical thickness and albedo may increase. The result is a negative feedback on the climate change, tending to reduce the surface temperature increase. Recent research suggests that the optical thickness feedback can depend sensitively on aspects of cirrus which are not well observed or adequately incorporated in typical present-day climate models.

  15. Engaging Students with Audio Feedback

    Science.gov (United States)

    Cann, Alan

    2014-01-01

    Students express widespread dissatisfaction with academic feedback. Teaching staff perceive a frequent lack of student engagement with written feedback, much of which goes uncollected or unread. Published evidence shows that audio feedback is highly acceptable to students but is underused. This paper explores methods to produce and deliver audio…

  16. Student Perceptions of Classroom Feedback

    Science.gov (United States)

    Gamlem, Siv M.; Smith, Kari

    2013-01-01

    Feedback to students has been identified as a key strategy in learning and teaching, but we know less about how feedback is understood by students. The purpose of this study is to gain more insight into lower secondary students' perceptions of when and how they find classroom feedback useful. This article draws on data generated through individual…

  17. Det ved vi om Feedback

    DEFF Research Database (Denmark)

    Christensen, Vibeke; Bærenholdt, Jørgen

    Præsentation af forskningsviden om feedback i forskellige personkonstellationer i undervisningen: Feedback fra lærer til elev, fra elever til lærer, fra elev til elev og elevens eget arbejde med feedback til sig selv. De præsenterede forskningsresultater er udvalgt dels inden for en kognitivistisk...

  18. A Journey towards Sustainable Feedback

    Science.gov (United States)

    Mutch, Allyson; Young, Charlotte; Davey, Tamzyn; Fitzgerald, Lisa

    2018-01-01

    Meeting students' expectations associated with the provision of feedback is a perennial challenge for tertiary education. Efforts to provide comprehensive, timely feedback within our own first year undergraduate public health courses have not always met students' expectations. In response, we sought to develop peer feedback activities to support…

  19. Polarization feedback laser stabilization

    Science.gov (United States)

    Esherick, P.; Owyoung, A.

    1987-09-28

    A system for locking two Nd:YAG laser oscillators includes an optical path for feeding the output of one laser into the other with different polarizations. Elliptical polarization is incorporated into the optical path so that the change in polarization that occurs when the frequencies coincide may be detected to provide a feedback signal to control one laser relative to the other. 4 figs.

  20. Regenerative feedback resonant circuit

    Science.gov (United States)

    Jones, A. Mark; Kelly, James F.; McCloy, John S.; McMakin, Douglas L.

    2014-09-02

    A regenerative feedback resonant circuit for measuring a transient response in a loop is disclosed. The circuit includes an amplifier for generating a signal in the loop. The circuit further includes a resonator having a resonant cavity and a material located within the cavity. The signal sent into the resonator produces a resonant frequency. A variation of the resonant frequency due to perturbations in electromagnetic properties of the material is measured.

  1. Sand Dune Albedo Feedback

    Directory of Open Access Journals (Sweden)

    Yosef Ashkenazy

    2018-02-01

    Full Text Available Sand dunes cover substantial parts of desert areas. Fully active dunes are bare, while fixed dunes are stabilized by vegetation and biogenic crust, and the dune activity is affected by the wind. Here we suggest the following atmosphere-sand dune feedback: spatial differences in the dunes’ vegetation and biogenic crust cover lead to differences in albedo as the albedo of bare sand is larger than that of vegetation and biogenic crust. This leads to a higher temperature over the vegetated area, resulting in air flow from the bare dune area to the vegetated dune area, thus increasing the wind activity over the vegetated dune area. In turn, this leads to enhanced stress on the vegetation and enhanced dune activity and thus to a decrease in vegetation. These changes in vegetation cover affect the surface albedo, leading to a change in wind activity. We examined this feedback using an atmospheric general circulation model, Weather Research and Forecasting (WRF, in selected regions of the northwestern Negev Desert and the Sahara/Sahel region, and we show that changes in surface albedo do indeed lead to significantly enhanced wind activity over the lower albedo region. We then incorporated this feedback into a simple vegetated dune model, showing that the multiple states associated with active and fixed dunes can be obtained for a larger range of parameters and that the stables states become more extreme (i.e., the fixed dune state becomes more vegetated and the active dune state becomes less vegetated.

  2. Feedback on Feedback: Eliciting Learners' Responses to Written Feedback through Student-Generated Screencasts

    Science.gov (United States)

    Fernández-Toro, María; Furnborough, Concha

    2014-01-01

    Despite the potential benefits of assignment feedback, learners often fail to use it effectively. This study examines the ways in which adult distance learners engage with written feedback on one of their assignments. Participants were 10 undergraduates studying Spanish at the Open University, UK. Their responses to feedback were elicited by means…

  3. Investigating Expectations and Experiences of Audio and Written Assignment Feedback in First-Year Undergraduate Students

    Science.gov (United States)

    Fawcett, Hannah; Oldfield, Jeremy

    2016-01-01

    Previous research suggests that audio feedback may be an important mechanism for facilitating effective and timely assignment feedback. The present study examined expectations and experiences of audio and written feedback provided through "turnitin for iPad®" from students within the same cohort and assignment. The results showed that…

  4. Feedback på arbejdspladser

    DEFF Research Database (Denmark)

    Holdt Christensen, Peter

    Feedback på arbejdspladser er vigtig. Men feedback er også et populært begreb mange taler med om uden dog at vide sig helt sikker på hvad det er. Formålet med denne bog er at bidrage til en bedre forståelse af hvad feedback er, hvordan det fungerer og dermed hvordan arbejdspladser bedst muligt bør...... understøtte feedback. Med udgangspunkt i forskningen identificeres centrale udfordringer ved feedback, bl.a. hvorfor det kan være svært at give præcis feedback, hvordan forholdet mellem lederen og den ansatte påvirker den feedback der gives, og hvad der kendetegner en feedback kultur. Bogen er skrevet til...... undervisere og studerende på videregående uddannelser samt praktikere der ønsker en systematisk og forskningsbaseret forståelse af feedback på arbejdspladser. Bogen er således ikke en kogebog til bedre feedback, men en analyse og diskussion af hvad forskningen ved om feedback, og bidrager med inspiration og...

  5. Mechanics

    CERN Document Server

    Chester, W

    1979-01-01

    When I began to write this book, I originally had in mind the needs of university students in their first year. May aim was to keep the mathematics simple. No advanced techniques are used and there are no complicated applications. The emphasis is on an understanding of the basic ideas and problems which require expertise but do not contribute to this understanding are not discussed. How­ ever, the presentation is more sophisticated than might be considered appropri­ ate for someone with no previous knowledge of the subject so that, although it is developed from the beginning, some previous acquaintance with the elements of the subject would be an advantage. In addition, some familiarity with element­ ary calculus is assumed but not with the elementary theory of differential equations, although knowledge of the latter would again be an advantage. It is my opinion that mechanics is best introduced through the motion of a particle, with rigid body problems left until the subject is more fully developed. Howev...

  6. The Endogenous Feedback Network

    DEFF Research Database (Denmark)

    Augustenborg, Claudia Carrara

    2010-01-01

    proposals, it will first be considered the extents of their reciprocal compatibility, tentatively shaping an integrated, theoretical profile of consciousness. A new theory, the Endogenous Feedback Network (EFN) will consequently be introduced which, beside being able to accommodate the main tenets...... of the reviewed theories, appears able to compensate for the explanatory gaps they leave behind. The EFN proposes consciousness as the phenomenon emerging from a distinct network of neural paths broadcasting the neural changes associated to any mental process. It additionally argues for the need to include a 5th...

  7. Feedback reliability calculation for an iterative block decision feedback equalizer

    OpenAIRE

    Huang, G; Nix, AR; Armour, SMD

    2009-01-01

    A new class of iterative block decision feedback equalizer (IB-DFE) was pioneered by Chan and Benvenuto. Unlike the conventional DFE, the IB-DFE is optimized according to the reliability of the feedback (FB) symbols. Since the use of the training sequence (TS) for feedback reliability (FBR) estimation lowers the bandwidth efficiency, FBR estimation without the need for additional TS is of considerable interest. However, prior FBR estimation is limited in the literature to uncoded M-ary phases...

  8. A reduced feedback proportional fair multiuser scheduling scheme

    KAUST Repository

    Shaqfeh, Mohammad

    2011-12-01

    Multiuser switched-diversity scheduling schemes were recently proposed in order to overcome the heavy feedback requirements of conventional opportunistic scheduling schemes by applying a threshold-based, distributed and ordered scheduling mechanism. A slight reduction in the prospected multiuser diversity gains is an acceptable trade-off for great savings in terms of required channel-state-information feedback messages. In this work, we propose a novel proportional fair multiuser switched-diversity scheduling scheme and we demonstrate that it can be optimized using a practical and distributed method to obtain the per-user feedback thresholds. We demonstrate by numerical examples that our reduced feedback proportional fair scheduler operates within 0.3 bits/sec/Hz from the achievable rates by the conventional full feedback proportional fair scheduler in Rayleigh fading conditions. © 2011 IEEE.

  9. Role of measurement in feedback-controlled quantum engines

    Science.gov (United States)

    Yi, Juyeon; Kim, Yong Woon

    2018-01-01

    In feedback controls, measurement is an essential step in designing protocols according to outcomes. For quantum mechanical systems, measurement has another effect; to supply energy to the measured system. We verify that in feedback-controlled quantum engines, measurement plays a dual role; not only as an auxiliary to perform feedback control but also as an energy supply to drive the engines. We consider a specific engine cycle exploiting feedback control followed by projective measurement and show that the maximum bound of the extractable work is set by both the efficacy of the feedback control and the energy change caused by projective measurement. We take a concrete example of an engine using an immobile spin-1/2 particle as a working substance and suggest two possible scenarios for work extraction.

  10. How Quasar Feedback May Shape the Co-evolutionary Paths

    Energy Technology Data Exchange (ETDEWEB)

    Ishibashi, Wako, E-mail: wako.ishibashi@physik.uzh.ch [Physik-Institut, University of Zurich, Zürich (Switzerland)

    2017-10-17

    Observations point toward some form of “co-evolutionary sequence,” from dust-enshrouded starbursts to luminous unobscured quasars. Active galactic nucleus (AGN) feedback is generally invoked to expel the obscuring dusty gas in a blow-out event, eventually revealing the hidden central quasar. However, the physical mechanism driving AGN feedback, either due to winds or radiation, remains uncertain and is still a source of much debate. We consider quasar feedback, based on radiation pressure on dust, which directly acts on the obscuring dusty gas. We show that AGN radiative feedback is capable of efficiently removing the obscuring cocoon, and driving powerful outflows on galactic scales, consistent with recent observations. I will discuss how such quasar feedback may provide a natural physical interpretation of the observed evolutionary path, and the physical implications in the broader context of black hole-host galaxy co-evolution.

  11. Emotional feedback for mobile devices

    CERN Document Server

    Seebode, Julia

    2015-01-01

    This book investigates the functional adequacy as well as the affective impression made by feedback messages on mobile devices. It presents an easily adoptable experimental setup to examine context effects on various feedback messages, and applies it to auditory, tactile and auditory-tactile feedback messages. This approach provides insights into the relationship between the affective impression and functional applicability of these messages as well as an understanding of the influence of unimodal components on the perception of multimodal feedback messages. The developed paradigm can also be extended to investigate other aspects of context and used to investigate feedback messages in modalities other than those presented. The book uses questionnaires implemented on a Smartphone, which can easily be adopted for field studies to broaden the scope even wider. Finally, the book offers guidelines for the design of system feedback.

  12. Operation feedback analysis applied to preventive maintenance

    International Nuclear Information System (INIS)

    Bouchet, J.L.; Havart, J.; Jacquot, J.P.; Lannoy, A.; Vasseur, D.

    1992-03-01

    The paper presents the contribution of operation feedback data bases and their analysis for the optimization of a preventive maintenance program. The RCM approach (Reliability Centered Maintenance) is based on a functional breakdown of systems and components. There are four major stages: analysis of equipment criticality, critical failure analysis for each critical component, selection of maintenance tasks, and operation feedback analysis. The in-depth knowledge of the failure and degradation mechanisms is only available through operation feedback, its analysis and experts judgements. The validation of the information collected in the various feedback files, and its statistical processing coupled with reliability calculations, enables : - the definition of the causes of failure and degradation noted, - the estimation of the associated failure rate and the calculation of the evolution of this failure rate as the age of the component increases. The paper presents the approach used and the results obtained for the pilot study of the chemical and volumetric control system CVCS of 900 MW PWR nuclear power plants. About 2 500 sheets, concerning a lot of equipment types (pumps, sensors, valves, ...) have been expertised and the statistical processing provided basic reliability parameters for RCM (rates, modes, causes, subcomponents, ...). (authors). 5 tabs., 6 figs., 7 refs

  13. Strategies in probabilistic feedback learning in Parkinson patients OFF medication.

    Science.gov (United States)

    Bellebaum, C; Kobza, S; Ferrea, S; Schnitzler, A; Pollok, B; Südmeyer, M

    2016-04-21

    Studies on classification learning suggested that altered dopamine function in Parkinson's Disease (PD) specifically affects learning from feedback. In patients OFF medication, enhanced learning from negative feedback has been described. This learning bias was not seen in observational learning from feedback, indicating different neural mechanisms for this type of learning. The present study aimed to compare the acquisition of stimulus-response-outcome associations in PD patients OFF medication and healthy control subjects in active and observational learning. 16 PD patients OFF medication and 16 controls were examined with three parallel learning tasks each, two feedback-based (active and observational) and one non-feedback-based paired associates task. No acquisition deficit was seen in the patients for any of the tasks. More detailed analyses on the learning strategies did, however, reveal that the patients showed more lose-shift responses during active feedback learning than controls, and that lose-shift and win-stay responses more strongly determined performance accuracy in patients than controls. For observational feedback learning, the performance of both groups correlated similarly with the performance in non-feedback-based paired associates learning and with the accuracy of observed performance. Also, patients and controls showed comparable evidence of feedback processing in observational learning. In active feedback learning, PD patients use alternative learning strategies than healthy controls. Analyses on observational learning did not yield differences between patients and controls, adding to recent evidence of a differential role of the human striatum in active and observational learning from feedback. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  14. Hvad siger forskningen om feedback?

    DEFF Research Database (Denmark)

    Holdt Christensen, Peter

    2016-01-01

    Feedback skal serveres ligesom en gammeldags sandwich. Først lidt brød, så det lidt sejere kød og til sidst igen til lidt brød”. Sådan nogenlunde lyder en pragmatisk løsning på udfordringerne ved at give feedback. Når medarbejdere skal have negativ feedback, skal denne altså pakkes ind, så feedb...... feedbacken indledes med let fordøjeligt positiv feedback, derefter kommer den negative – og noget sværere fordøjelige – feedback, og til sidst afrundes feedbacken med en god udgangsreplik, nemlig den positive feedback.......”Feedback skal serveres ligesom en gammeldags sandwich. Først lidt brød, så det lidt sejere kød og til sidst igen til lidt brød”. Sådan nogenlunde lyder en pragmatisk løsning på udfordringerne ved at give feedback. Når medarbejdere skal have negativ feedback, skal denne altså pakkes ind, så...

  15. Optimal allocation of reviewers for peer feedback

    DEFF Research Database (Denmark)

    Wind, David Kofoed; Jensen, Ulf Aslak; Jørgensen, Rasmus Malthe

    2017-01-01

    Peer feedback is the act of letting students give feedback to each other on submitted work. There are multiple reasons to use peer feedback, including students getting more feedback, time saving for teachers and increased learning by letting students reflect on work by others. In order for peer...... feedback to be effective students should give and receive useful feedback. A key challenge in peer feedback is allocating the feedback givers in a good way. It is important that reviewers are allocated to submissions such that the feedback distribution is fair - meaning that all students receive good...... feedback. In this paper we present a novel way to intelligently allocate reviewers for peer feedback. We train a statistical model to infer the quality of feedback based on a dataset of feedback quality evaluations. This dataset contains more than 20,000 reviews where the receiver of the feedback has...

  16. KEKB bunch feedback systems

    Energy Technology Data Exchange (ETDEWEB)

    Tobiyama, M.; Kikutani, E. [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

    1996-08-01

    Design and the present status of the bunch by bunch feedback systems for KEKB rings are shown. The detection of the bunch oscillation are made with the phase detection for longitudinal plane, the AM/PM method for transverse plane. Two GHz component of the bunch signal which is extracted with an analog FIR filter is used for the detection. Hardware two-tap FIR filter systems to shift the phase of the oscillation by 90deg will be used for the longitudinal signal processing. The same system will be used with no filtering but with only digital delay for transverse system. The candidate for the kicker and the required maximum power are also estimated. (author)

  17. Reviewing operational experience feedback

    International Nuclear Information System (INIS)

    1991-04-01

    The purpose of this document is to provide detailed supplementary guidance to OSART experts to aid in the evaluation of operational experience feedback (OEF) programmes at nuclear power plants. The document begins by describing the objectives of an OEF programme. It goes on to indicate preparatory work and investigatory guidance for the expert. Section 5 describes attributes of an excellent OEF programme. Appended to these guidelines are examples of OEF documents from various plants. These are intended to help the expert by demonstrating the actual implementation of OEF in practice. These guidelines are in no way intended to conflict with existing national regulations and rules. A comprehensive OEF programme, as described in Section 2, would be impossible to evaluated in detail in the amount of time typically allocated for assessing OEF in an OSART review. The expert must use his or her time wisely by concentrating on those areas that appear to be the weakest

  18. Feedback matters current feedback practices in the EFL classroom

    CERN Document Server

    Reitbauer, Margit; Mercer, Sarah; Schumm-Fauster, Jennifer

    2013-01-01

    This varied collection of papers is concerned with feedback in the language learning context. With its blend of theoretical overviews, action research-based empirical studies and practical implications, this will be a valuable resource for all academics and practitioners concerned with generating feedback that matters.

  19. Multi-bunch Feedback Systems

    International Nuclear Information System (INIS)

    Lonza, M; Schmickler, H

    2014-01-01

    Coupled-bunch instabilities excited by the interaction of the particle beam with its surroundings can seriously limit the performance of circular particle accelerators. These instabilities can be cured by the use of active feedback systems based on sensors capable of detecting the unwanted beam motion and actuators that apply the feedback correction to the beam. Advances in electronic technology now allow the implementation of feedback loops using programmable digital systems. Besides important advantages in terms of flexibility and reproducibility, digital systems open the way to the use of novel diagnostic tools and additional features. We first introduce coupled-bunch instabilities, analysing the equation of motion of charged particles and the different modes of oscillation of a multi-bunch beam, showing how they can be observed and measured. Different types of feedback systems will then be presented as examples of real implementations that belong to the history of multi-bunch feedback systems. The main components of a feedback system and the related issues will also be analysed. Finally, we shall focus on digital feedback systems, their characteristics, and features, as well as on how they can be concretely exploited for both the optimization of feedback performance and for beam dynamics studies

  20. Videoer om feedback i undervisningen

    DEFF Research Database (Denmark)

    Jensen, Hanne Nexø

    2017-01-01

    I denne video bliver du introduceret til en måde at praktisere og rammesætte klyngevejledning på i bachelorundervisning. Klyngefeedbackformen til de studerende er valgt, da de studerende lærer meget af både at give og om modtage feedback fra medstuderende. Fokus på feedback ligger derfor primært i...

  1. Multi-bunch Feedback Systems

    CERN Document Server

    Lonza, M.

    2014-12-19

    Coupled-bunch instabilities excited by the interaction of the particle beam with its surroundings can seriously limit the performance of circular particle accelerators. These instabilities can be cured by the use of active feedback systems based on sensors capable of detecting the unwanted beam motion and actuators that apply the feedback correction to the beam. Advances in electronic technology now allow the implementation of feedback loops using programmable digital systems. Besides important advantages in terms of flexibility and reproducibility, digital systems open the way to the use of novel diagnostic tools and additional features. We first introduce coupled-bunch instabilities, analysing the equation of motion of charged particles and the different modes of oscillation of a multi-bunch beam, showing how they can be observed and measured. Different types of feedback systems will then be presented as examples of real implementations that belong to the history of multi-bunch feedback systems. The main co...

  2. Feedback systems for linear colliders

    CERN Document Server

    Hendrickson, L; Himel, Thomas M; Minty, Michiko G; Phinney, N; Raimondi, Pantaleo; Raubenheimer, T O; Shoaee, H; Tenenbaum, P G

    1999-01-01

    Feedback systems are essential for stable operation of a linear collider, providing a cost-effective method for relaxing tight tolerances. In the Stanford Linear Collider (SLC), feedback controls beam parameters such as trajectory, energy, and intensity throughout the accelerator. A novel dithering optimization system which adjusts final focus parameters to maximize luminosity contributed to achieving record performance in the 1997-98 run. Performance limitations of the steering feedback have been investigated, and improvements have been made. For the Next Linear Collider (NLC), extensive feedback systems are planned as an intregal part of the design. Feedback requiremetns for JLC (the Japanese Linear Collider) are essentially identical to NLC; some of the TESLA requirements are similar but there are significant differences. For NLC, algorithms which incorporate improvements upon the SLC implementation are being prototyped. Specialized systems for the damping rings, rf and interaction point will operate at hi...

  3. Multi-bunch feedback systems

    CERN Document Server

    Lonza, M

    2008-01-01

    Coupled-bunch instabilities excited by the interaction of the particle beam with its surroundings can seriously limit the performance of circular particle accelerators. These instabilities can be cured by the use of active feedback systems based on sensors capable of detecting the unwanted beam motion and actuators that apply the feedback correction to the beam. The advances in electronic technology now allow the implementation of feedback loops using programmable digital systems. Besides important advantages in terms of flexibility and reproducibility, digital systems open the way to the use of novel diagnostic tools and additional features. The lecture will first introduce coupled-bunch instabilities analysing the equation of motion of charged particles and the different modes of oscillation of a multi-bunch beam, showing how they can be observed and measured. Different types of feedbacks systems will then be presented as examples of real implementations that belong to the history of multi-bunch feedback sy...

  4. Smith-Purcell Distributed Feedback Laser

    CERN Document Server

    Kipnis, D; Gover, A

    2005-01-01

    Smith-Purcell radiation is the emission of electromagnetic radiation by an electron beam passing next to an optical grating. Recently measurement of relatively intense power of such radiation was observed in the THz-regime [1]. To explain the high intensity and the super-linear dependence on current beyond a threshold it was suggested that the radiating device operated in the high gain regime, amplifying spontaneous emission (ASE) [1,2]. We contest this interpretation and suggest an alternative mechanism. According to our interpretation the device operates as a distributed feedback (DFB) laser oscillator, in which a forward going surface wave, excited by the beam on the grating surface, is coupled to a backward going surface wave by a second order Bragg reflection process. This feedback process produces a saturated oscillator. We present theoretical analysis of the proposed process, which fits the reported experimental results, and enables better design of the radiation device, operating as a Smith-Purcell DF...

  5. Understanding Feedback: A Learning Theory Perspective

    Science.gov (United States)

    Thurlings, Marieke; Vermeulen, Marjan; Bastiaens, Theo; Stijnen, Sjef

    2013-01-01

    This article aims to review literature on feedback to teachers. Because research has hardly focused on feedback among teachers, the review's scope also includes feedback in classrooms. The review proposes that the effectiveness of feedback and feedback processes depend on the learning theory adhered to. Findings show that regardless of the…

  6. Understanding feedback: A learning theory perspective

    NARCIS (Netherlands)

    Thurlings, Marieke; Vermeulen, Marjan; Bastiaens, Theo; Stijnen, Sjef

    2018-01-01

    This article aims to review literature on feedback to teachers. Because research has hardly focused on feedback among teachers, the review’s scope also includes feedback in class- rooms. The review proposes that the effectiveness of feedback and feedback processes depend on the learning theory

  7. Feedback on the Feedback: Sociocultural Interpretation of Saudi ESL Learners' Opinions about Writing Feedback

    Science.gov (United States)

    Mustafa, Rami F.

    2012-01-01

    This qualitative study employed informal conversational interviews and semi-structured individual interviews to capture the Saudi students' opinions about the feedback they receive, and about their perceptions on what constitutes helpful feedback. Sociocultural theory was used as the framework of this study. The findings suggest that the Saudi…

  8. The "Physical feedbacks of Arctic PBL, Sea ice, Cloud and AerosoL (PASCAL)" campaign during the Arctic POLARSTERN expedition PS106 in spring 2017.

    Science.gov (United States)

    Macke, A.

    2017-12-01

    The Polar regions are important components in the global climate system. The widespread surface snow and ice cover strongly impacts the surface energy budget, which is tightly coupled to global atmospheric and oceanic circulations. The coupling of sea ice, clouds and aerosol in the transition zone between Open Ocean and sea ice is the focus of the PASCAL investigations to improve our understanding of the recent dramatic reduction in Arctic sea-ice. A large variety of active/passive remote sensing, in-situ-aerosol observation, and spectral irradiance measurements have been obtained during the German research icebreaker POLARSTERN expedition PS106, and provided detailed information on the atmospheric spatiotemporal structure, aerosol and cloud chemical and microphysical properties as well as the resulting surface radiation budget. Nearly identical measurements at the AWIPEV Base (German - French Research Base) in Ny-Ålesund close to the Open Ocean and collocated airborne activities of the POLAR 5 and POLAR 6 AWI aircraft in the framework of the ACLOUD project have been carried out in parallel. The airborne observations have been supplemented by observations of the boundary layer structure (mean and turbulent quantities) from a tethered balloon reaching up to 1500 m, which was operated at an ice floe station nearby POLARSTERN for two weeks. All observational activities together with intense modelling at various scales are part of the German Collaborative Research Cluster TR 172 "Arctic Amplification" that aims to provide an unprecedented picture of the complex Arctic weather and climate system. The presentation provides an overview of the measurements on-board POLARSTERN and on the ice floe station during PASCAL from May 24 to July 21 2017. We conclude how these and future similar measurements during the one-year ice drift of POLARSTERN in the framework of MOSAiC help to reduce uncertainties in Arctic aerosol-cloud interaction, cloud radiative forcing, and surface/atmosphere

  9. Styrket feedback gennem studerendes selvevaluering

    DEFF Research Database (Denmark)

    Andersen, Lars Bo

    2016-01-01

    Studerende er ofte utilfredse med såvel kvaliteten som kvantiteten af feedback på skriftligt arbejde. Ligeledes kan det som underviser være svært at afgive feedback, der tager udgangspunkt i de studerendes respektive læringssituationer, hvis man ikke har andet afsæt end opgavetekster. Denne artikel...... beskriver derfor to eksperimenter med brug af selvevaluering som kvalificerende mellemled i ekstern feedback på skriveøvelser. Eksperimenternes formål er at styrke den formative læring ved skriftligt arbejde. I det første eksperiment bestod feedbacken af underviser-feedback, mens det andet eksperiment...... indebar peer-feedback og fælles feedback. I begge tilfælde blev selvevalueringen foretaget med udgangspunkt i en kriteriebaseret retteguide. Eksperimenterne medførte, at den eksterne feedback blev målrettet og kvalificeret i forhold til den enkelte studerende, mens selve skriveprocessen mod forventning...

  10. Virtual potentials for feedback traps.

    Science.gov (United States)

    Jun, Yonggun; Bechhoefer, John

    2012-12-01

    The recently developed feedback trap can be used to create arbitrary virtual potentials, to explore the dynamics of small particles or large molecules in complex situations. Experimentally, feedback traps introduce several finite time scales: There is a delay between the measurement of a particle's position and the feedback response, the feedback response is applied for a finite update time, and a finite camera exposure integrates motion. We show how to incorporate such timing effects into the description of particle motion. For the test case of a virtual quadratic potential, we give the first accurate description of particle dynamics, calculating the power spectrum and variance of fluctuations as a function of feedback gain, testing against simulations. We show that for small feedback gains, the motion approximates that of a particle in an ordinary harmonic potential. Moreover, if the potential is varied in time, for example by varying its stiffness, the work that is calculated approximates that done in an ordinary changing potential. The quality of the approximation is set by the ratio of the update time of the feedback loop to the relaxation time of motion in the virtual potential.

  11. Quantifying the ice-albedo feedback through decoupling

    Science.gov (United States)

    Kravitz, B.; Rasch, P. J.

    2017-12-01

    The ice-albedo feedback involves numerous individual components, whereby warming induces sea ice melt, inducing reduced surface albedo, inducing increased surface shortwave absorption, causing further warming. Here we attempt to quantify the sea ice albedo feedback using an analogue of the "partial radiative perturbation" method, but where the governing mechanisms are directly decoupled in a climate model. As an example, we can isolate the insulating effects of sea ice on surface energy and moisture fluxes by allowing sea ice thickness to change but fixing Arctic surface albedo, or vice versa. Here we present results from such idealized simulations using the Community Earth System Model in which individual components are successively fixed, effectively decoupling the ice-albedo feedback loop. We isolate the different components of this feedback, including temperature change, sea ice extent/thickness, and air-sea exchange of heat and moisture. We explore the interactions between these different components, as well as the strengths of the total feedback in the decoupled feedback loop, to quantify contributions from individual pieces. We also quantify the non-additivity of the effects of the components as a means of investigating the dominant sources of nonlinearity in the ice-albedo feedback.

  12. The Interplay between Feedback and Buffering in Cellular Homeostasis.

    Science.gov (United States)

    Hancock, Edward J; Ang, Jordan; Papachristodoulou, Antonis; Stan, Guy-Bart

    2017-11-22

    Buffering, the use of reservoirs of molecules to maintain concentrations of key molecular species, and negative feedback are the primary known mechanisms for robust homeostatic regulation. To our knowledge, however, the fundamental principles behind their combined effect have not been elucidated. Here, we study the interplay between buffering and negative feedback in the context of cellular homeostasis. We show that negative feedback counteracts slow-changing disturbances, whereas buffering counteracts fast-changing disturbances. Furthermore, feedback and buffering have limitations that create trade-offs for regulation: instability in the case of feedback and molecular noise in the case of buffering. However, because buffering stabilizes feedback and feedback attenuates noise from slower-acting buffering, their combined effect on homeostasis can be synergistic. These effects can be explained within a traditional control theory framework and are consistent with experimental observations of both ATP homeostasis and pH regulation in vivo. These principles are critical for studying robustness and homeostasis in biology and biotechnology. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  13. Negative Feedback in Genetic Circuits Confers Evolutionary Resilience and Capacitance

    Directory of Open Access Journals (Sweden)

    David C. Marciano

    2014-06-01

    Full Text Available Natural selection for specific functions places limits upon the amino acid substitutions a protein can accept. Mechanisms that expand the range of tolerable amino acid substitutions include chaperones that can rescue destabilized proteins and additional stability-enhancing substitutions. Here, we present an alternative mechanism that is simple and uses a frequently encountered network motif. Computational and experimental evidence shows that the self-correcting, negative-feedback gene regulation motif increases repressor expression in response to deleterious mutations and thereby precisely restores repression of a target gene. Furthermore, this ability to rescue repressor function is observable across the Eubacteria kingdom through the greater accumulation of amino acid substitutions in negative-feedback transcription factors compared to genes they control. We propose that negative feedback represents a self-contained genetic canalization mechanism that preserves phenotype while permitting access to a wider range of functional genotypes.

  14. A modular positive feedback-based gene amplifier

    Directory of Open Access Journals (Sweden)

    Bhalerao Kaustubh D

    2010-02-01

    Full Text Available Abstract Background Positive feedback is a common mechanism used in the regulation of many gene circuits as it can amplify the response to inducers and also generate binary outputs and hysteresis. In the context of electrical circuit design, positive feedback is often considered in the design of amplifiers. Similar approaches, therefore, may be used for the design of amplifiers in synthetic gene circuits with applications, for example, in cell-based sensors. Results We developed a modular positive feedback circuit that can function as a genetic signal amplifier, heightening the sensitivity to inducer signals as well as increasing maximum expression levels without the need for an external cofactor. The design utilizes a constitutively active, autoinducer-independent variant of the quorum-sensing regulator LuxR. We experimentally tested the ability of the positive feedback module to separately amplify the output of a one-component tetracycline sensor and a two-component aspartate sensor. In each case, the positive feedback module amplified the response to the respective inducers, both with regards to the dynamic range and sensitivity. Conclusions The advantage of our design is that the actual feedback mechanism depends only on a single gene and does not require any other modulation. Furthermore, this circuit can amplify any transcriptional signal, not just one encoded within the circuit or tuned by an external inducer. As our design is modular, it can potentially be used as a component in the design of more complex synthetic gene circuits.

  15. LHC beam stability and feedback control

    Energy Technology Data Exchange (ETDEWEB)

    Steinhagen, Ralph

    2007-07-20

    proportional-integral (PI) controller that is extended by an internal Smith-Predictor and so called anti-windup mechanism in order to compensate the deteriorating effects of non-linearities due to the current rate limiter and inevitable dead times in the system. The predictor logic has been derived using Youla's affine parameterisation enables to adjust the effective feedback bandwidth through a single parameter. A real-time 'testbed' complementary to the feedback controller has been developed to test part of the controller logic and its components prior to LHC commissioning. (orig.)

  16. AGN Feedback Compared: Jets versus Radiation

    Science.gov (United States)

    Cielo, Salvatore; Bieri, Rebekka; Volonteri, Marta; Wagner, Alexander Y.; Dubois, Yohan

    2018-03-01

    Feedback by Active Galactic Nuclei is often divided into quasar and radio mode, powered by radiation or radio jets, respectively. Both are fundamental in galaxy evolution, especially in late-type galaxies, as shown by cosmological simulations and observations of jet-ISM interactions in these systems. We compare AGN feedback by radiation and by collimated jets through a suite of simulations, in which a central AGN interacts with a clumpy, fractal galactic disc. We test AGN of 1043 and 1046 erg/s, considering jets perpendicular or parallel to the disc. Mechanical jets drive the more powerful outflows, exhibiting stronger mass and momentum coupling with the dense gas, while radiation heats and rarifies the gas more. Radiation and perpendicular jets evolve to be quite similar in outflow properties and effect on the cold ISM, while inclined jets interact more efficiently with all the disc gas, removing the densest 20% in 20 Myr, and thereby reducing the amount of cold gas available for star formation. All simulations show small-scale inflows of 0.01 - 0.1 M⊙/yr, which can easily reach down to the Bondi radius of the central supermassive black hole (especially for radiation and perpendicular jets), implying that AGN modulate their own duty cycle in a feedback/feeding cycle.

  17. Snap, crackle, pop: sub-grid supernova feedback in AMR simulations of disc galaxies

    Science.gov (United States)

    Rosdahl, Joakim; Schaye, Joop; Dubois, Yohan; Kimm, Taysun; Teyssier, Romain

    2017-04-01

    We compare five sub-grid models for supernova (SN) feedback in adaptive mesh refinement (AMR) simulations of isolated dwarf and L-star disc galaxies with 20-40 pc resolution. The models are thermal dump, stochastic thermal, 'mechanical' (injecting energy or momentum depending on the resolution), kinetic and delayed cooling feedback. We focus on the ability of each model to suppress star formation and generate outflows. Our highest resolution runs marginally resolve the adiabatic phase of the feedback events, which correspond to 40 SN explosions, and the first three models yield nearly identical results, possibly indicating that kinetic and delayed cooling feedback converge to wrong results. At lower resolution all models differ, with thermal dump feedback becoming inefficient. Thermal dump, stochastic and mechanical feedback generate multiphase outflows with mass loading factors β ≪ 1, which is much lower than observed. For the case of stochastic feedback, we compare to published SPH simulations, and find much lower outflow rates. Kinetic feedback yields fast, hot outflows with β ˜ 1, but only if the wind is in effect hydrodynamically decoupled from the disc using a large bubble radius. Delayed cooling generates cold, dense and slow winds with β > 1, but large amounts of gas occupy regions of temperature-density space with short cooling times. We conclude that either our resolution is too low to warrant physically motivated models for SN feedback, that feedback mechanisms other than SNe are important or that other aspects of galaxy evolution, such as star formation, require better treatment.

  18. Smart building temperature control using occupant feedback

    Science.gov (United States)

    Gupta, Santosh K.

    feedback signals, we propose a distributed solution, which ensures that a consensus is attained among all occupants upon convergence, irrespective of their temperature preferences being in coherence or conflicting. Occupants are only assumed to be rational, in that they choose their own temperature set-points so as to minimize their individual energy cost plus discomfort. We use Alternating Direction Method of Multipliers ( ADMM) to solve our consensus problem. We further establish the convergence of the proposed algorithm to the optimal thermal set point values that minimize the sum of the energy cost and the aggregate discomfort of all occupants in a multi-zone building. For simulating our consensus algorithm we use realistic building parameters based on the Watervliet test facility. The simulation study based on real world building parameters establish the validity of our theoretical model and provide insights on the dynamics of the system with a mobile user population. In the third part we present a game-theoretic (auction) mechanism, that requires occupants to "purchase" their individualized comfort levels beyond what is provided by default by the building operator. The comfort pricing policy, derived as an extension of Vickrey-Clarke-Groves (VCG) pricing, ensures incentive-compatibility of the mechanism, i.e., an occupant acting in self-interest cannot benefit from declaring their comfort function untruthfully, irrespective of the choices made by other occupants. The declared (or estimated) occupant comfort ranges (functions) are then utilized by the building operator---along with the energy cost information---to set the environment controls to optimally balance the aggregate discomfort of the occupants and the energy cost of the building operator. We use realistic building model and parameters based on our test facility to demonstrate the convergence of the actual temperatures in different zones to the desired temperatures, and provide insight to the pricing

  19. NAIP 2015 Imagery Feedback Map

    Data.gov (United States)

    Farm Service Agency, Department of Agriculture — The NAIP 2015 Imagery Feedback map allows users to make comments and observations about the quality of the 2015 National Agriculture Imagery Program (NAIP)...

  20. NAIP 2017 Imagery Feedback Map

    Data.gov (United States)

    Farm Service Agency, Department of Agriculture — The NAIP 2017 Imagery Feedback map allows users to make comments and observations about the quality of the 2017 National Agriculture Imagery Program (NAIP)...

  1. On the role of temperature feedbacks for Arctic amplification

    Science.gov (United States)

    Pithan, Felix; Mauritsen, Thorsten

    2013-04-01

    The amplification of global climate changes at the poles is a well-known feature of the climate system mentioned already by Arrhenius (1896). It has been linked to the surface-albedo feedback, changes in atmospheric and oceanic heat convergence, water vapour and cloud feedbacks and the albedo effect of black carbon on snow (Serreze and Barry, 2011). We here focus on the role of temperature feedbacks, which have received rather little attention in recent debates. The basic temperature feedback is the Planck feedback or the increase in the Earth's blackbody radiation due to a uniform temperature increase. Since the blackbody radiation scales with the fourth power of temperature, stronger warming is necessary in cold regions to balance a globally uniform radiative forcing. The second temperature feedback is caused by changes in the vertical atmospheric temperature structure: In the Tropics, deep convection leads to warming aloft being larger than at the surface, which causes a greater increase in outgoing longwave radiation compared a vertically uniform forcing and thus constitutes a negative feedback mechanism. In the Arctic, where warming is amplified at the surface, the lapse-rate feedback is positive (Wetherald and Manabe, 1975). We use CMIP5 model output and radiative Kernels to investigate the zonal distribution of temperature feedbacks. Arrhenius, S. (1896). On the influence of carbonic acid in the air upon the temperature of the ground Philos. Mag. J. Sci., 5, pp. 237-276 Serreze, M.C. and Barry, R.G. (2011) . Processes and impacts of Arctic amplification: A research synthesis, Global and Planetary Change, 77(1-2), pp. 85-96 Wetherald, R. and Manabe, S. (1975). The effects of changing the solar constant on the climate of a general circulation model. J. Atmos. Sci., 23 pp 2044-2059

  2. Feedback trap using optical force

    Science.gov (United States)

    Jun, Yonggun; Pak, Hyuk Kyu

    Recently, the feedback trap using electrophoretic force (ABEL trap) has been used in the experimental study of non-equilibrium thermodynamics such as Landauer's erasure principle. This trap can trap and manipulate a small particle in solution by canceling the Brownian fluctuations. Here, we propose a simple way to control a bead using optical force with feedback and show the dynamics of a single particle in the virtual potential.

  3. Recognition of boundary feedback systems

    DEFF Research Database (Denmark)

    Pedersen, Michael

    1989-01-01

    A system that has been the object of intense research is outlined. In view of that and recent progress of the theory of pseudodifferential boundary operator calculus, the author describes some features that could prove to be interesting in connection with the problems of boundary feedback...... stabilizability. It is shown that it is possible to use the calculus to consider more general feedback systems in a variational setup....

  4. Efferent feedback can explain many hearing phenomena

    Science.gov (United States)

    Holmes, W. Harvey; Flax, Matthew R.

    2015-12-01

    The mixed mode cochlear amplifier (MMCA) model was presented at the last Mechanics of Hearing workshop [4]. The MMCA consists principally of a nonlinear feedback loop formed when an efferent-controlled outer hair cell (OHC) is combined with the cochlear mechanics and the rest of the relevant neurobiology. Essential elements of this model are efferent control of the OHC motility and a delay in the feedback to the OHC. The input to the MMCA is the passive travelling wave. In the MMCA amplification is localized where both the neural and tuned mechanical systems meet in the Organ of Corti (OoC). The simplest model based on this idea is a nonlinear delay line resonator (DLR), which is mathematically described by a nonlinear delay-differential equation (DDE). This model predicts possible Hopf bifurcations and exhibits its most interesting behaviour when operating near a bifurcation. This contribution presents some simulation results using the DLR model. These show that various observed hearing phenomena can be accounted for by this model, at least qualitatively, including compression effects, two-tone suppression and some forms of otoacoustic emissions (OAEs).

  5. Feedback-enhanced sensitivity in optomechanics

    DEFF Research Database (Denmark)

    Harris, Glen I.; Andersen, Ulrik L.; Knittel, Joachim

    2012-01-01

    The intracavity power, and hence sensitivity, of optomechanical sensors is commonly limited by parametric instability. Here we characterize the degradation of sensitivity induced by parametric instability in a micron-scale cavity optomechanical system. Feedback via optomechanical transduction...... and electrical gradient force actuation is applied to suppress the parametric instability. As a result a 5.4-fold increase in mechanical motion transduction sensitivity is achieved to a final value of 1.9×10-18 mHz-1/2....

  6. Insights in time dependent cross compartment sensitivities from ensemble simulations with the fully coupled subsurface-land surface-atmosphere model TerrSysMP

    Science.gov (United States)

    Schalge, Bernd; Rihani, Jehan; Haese, Barbara; Baroni, Gabriele; Erdal, Daniel; Haefliger, Vincent; Lange, Natascha; Neuweiler, Insa; Hendricks-Franssen, Harrie-Jan; Geppert, Gernot; Ament, Felix; Kollet, Stefan; Cirpka, Olaf; Saavedra, Pablo; Han, Xujun; Attinger, Sabine; Kunstmann, Harald; Vereecken, Harry; Simmer, Clemens

    2017-04-01

    Currently, an integrated approach to simulating the earth system is evolving where several compartment models are coupled to achieve the best possible physically consistent representation. We used the model TerrSysMP, which fully couples subsurface, land surface and atmosphere, in a synthetic study that mimicked the Neckar catchment in Southern Germany. A virtual reality run at a high resolution of 400m for the land surface and subsurface and 1.1km for the atmosphere was made. Ensemble runs at a lower resolution (800m for the land surface and subsurface) were also made. The ensemble was generated by varying soil and vegetation parameters and lateral atmospheric forcing among the different ensemble members in a systematic way. It was found that the ensemble runs deviated for some variables and some time periods largely from the virtual reality reference run (the reference run was not covered by the ensemble), which could be related to the different model resolutions. This was for example the case for river discharge in the summer. We also analyzed the spread of model states as function of time and found clear relations between the spread and the time of the year and weather conditions. For example, the ensemble spread of latent heat flux related to uncertain soil parameters was larger under dry soil conditions than under wet soil conditions. Another example is that the ensemble spread of atmospheric states was more influenced by uncertain soil and vegetation parameters under conditions of low air pressure gradients (in summer) than under conditions with larger air pressure gradients in winter. The analysis of the ensemble of fully coupled model simulations provided valuable insights in the dynamics of land-atmosphere feedbacks which we will further highlight in the presentation.

  7. A biopsychosocial model based on negative feedback and control.

    Science.gov (United States)

    Carey, Timothy A; Mansell, Warren; Tai, Sara J

    2014-01-01

    Although the biopsychosocial model has been a popular topic of discussion for over four decades it has not had the traction in fields of research that might be expected of such an intuitively appealing idea. One reason for this might be the absence of an identified mechanism or a functional architecture that is authentically biopsychosocial. What is needed is a robust mechanism that is equally important to biochemical processes as it is to psychological and social processes. Negative feedback may be the mechanism that is required. Negative feedback has been implicated in the regulation of neurotransmitters as well as important psychological and social processes such as emotional regulation and the relationship between a psychotherapist and a client. Moreover, negative feedback is purported to also govern the activity of all other organisms as well as humans. Perceptual Control Theory (PCT) describes the way in which negative feedback establishes control at increasing levels of perceptual complexity. Thus, PCT may be the first biopsychosocial model to be articulated in functional terms. In this paper we outline the working model of PCT and explain how PCT provides an embodied hierarchical neural architecture that utilizes negative feedback to control physiological, psychological, and social variables. PCT has major implications for both research and practice and, importantly, provides a guide by which fields of research that are currently separated may be integrated to bring about substantial progress in understanding the way in which the brain alters, and is altered by, its behavioral and environmental context.

  8. Feedback i den laegelige postgraduate uddannelse

    DEFF Research Database (Denmark)

    Rubak, Sune; Ipsen, Merete; Sørensen, Jette

    2008-01-01

    . Feedback is essential in medical education and has great implications for the educational climate. It has been shown that a common language regarding the principles of feedback has a sustained effect on quality and frequency of feedback. Further research is needed on feedback and educational climate...

  9. Ergodic Interference Alignment with Delayed Feedback

    OpenAIRE

    Kang, Myung Gil; Choi, Wan

    2013-01-01

    We propose new ergodic interference alignment techniques for $K$-user interference channels with delayed feedback. Two delayed feedback scenarios are considered -- delayed channel information at transmitter (CIT) and delayed output feedback. It is proved that the proposed techniques achieve total $2K/(K+2)$ DoF which is higher than that by the retrospective interference alignment for the delayed feedback scenarios.

  10. Providing Students with Formative Audio Feedback

    Science.gov (United States)

    Brearley, Francis Q.; Cullen, W. Rod

    2012-01-01

    The provision of timely and constructive feedback is increasingly challenging for busy academics. Ensuring effective student engagement with feedback is equally difficult. Increasingly, studies have explored provision of audio recorded feedback to enhance effectiveness and engagement with feedback. Few, if any, of these focus on purely formative…

  11. Sustainable feedback: students’ and tutors’ perceptions

    NARCIS (Netherlands)

    Geitz, Gerry; Joosten-ten Brinke, Desirée; Kirschner, Paul A.

    2018-01-01

    Feedback has been shown to substantially influence students’ learning. However, not everything characterized as feedback is effective. Sustainable feedback places students in an active role in which they generate and use feedback from peers, self or others and aims at developing lifelong learning

  12. Feedback as Real-Time Constructions

    Science.gov (United States)

    Keiding, Tina Bering; Qvortrup, Ane

    2014-01-01

    This article offers a re-description of feedback and the significance of time in feedback constructions based on systems theory. It describes feedback as internal, real-time constructions in a learning system. From this perspective, feedback is neither immediate nor delayed, but occurs in the very moment it takes place. This article argues for a…

  13. Feedback in the emergency medicine clerkship.

    Science.gov (United States)

    Bernard, Aaron W; Kman, Nicholas E; Khandelwal, Sorabh

    2011-11-01

    Feedback is a technique used in medical education to help develop and improve clinical skills. A comprehensive review article specifically intended for the emergency medicine (EM) educator is lacking, and it is the intent of this article to provide the reader with an in-depth, up-to-date, and evidence-based review of feedback in the context of the EM clerkship. The review article is organized in a progressive manner, beginning with the definition of feedback, the importance of feedback in medical education, the obstacles limiting the effective delivery of feedback, and the techniques to overcome these obstacles then follows. The article concludes with practical recommendations to implement feedback in the EM clerkship. To advance the literature on feedback, the concept of receiving feedback is introduced. The published literature regarding feedback is limited but generally supportive of its importance and effectiveness. Obstacles in the way of feedback include time constraints, lack of direct observation, and fear of negative emotional responses from students. Feedback should be timely, expected, focused, based on first-hand data, and limited to behaviors that are remediable. Faculty development and course structure can improve feedback in the EM clerkship. Teaching students to receive feedback is a novel educational technique that can improve the feedback process. Feedback is an important educational technique necessary to improve clinical skills. Feedback can be delivered effectively in the EM clerkship.

  14. Feedback in the Emergency Medicine Clerkships

    Directory of Open Access Journals (Sweden)

    Sorabh Khandelwal

    2011-05-01

    Full Text Available Objective: Feedback is a technique used in medical education to help develop and improve clinical skills. A comprehensive review article specifically intended for the emergency medicine (EM educator is lacking, and it is the intent of this article to provide the reader with an in-depth, up-to-date, and evidence-based review of feedback in the context of the EM clerkship. Methods: The review article is organized in a progressive manner, beginning with the definition of feedback, the importance of feedback in medical education, and the obstacles limiting the effective delivery of feedback, and the techniques to overcome these obstacles then follows. The article concludes with practical recommendations to implement feedback in the EM clerkship. To advance the literature on feedback, the concept of receiving feedback is introduced. Results: The published literature regarding feedback is limited but generally supportive of its importance and effectiveness. Obstacles in the way of feedback include time constraints, lack of direct observation, and fear of negative emotional responses from students. Feedback should be timely, expected, focused, based on first-hand data, and limited to behaviors that are remediable. Faculty development and course structure can improve feedback in the EM clerkship. Teaching students to receive feedback is a novel educational technique that can improve the feedback process. Conclusion: Feedback is an important educational technique necessary to improve clinical skills. Feedback can be delivered effectively in the EM clerkship. [West J Emerg Med. 2011;12(4:537–542.

  15. Dynamics of Team Reflexivity after Feedback

    Science.gov (United States)

    Gabelica, Catherine; Van den Bossche, Piet; Segers, Mien; Gijselaers, Wim

    2014-01-01

    A great deal of work has been generated on feedback in teams and has shown that giving performance feedback to teams is not sufficient to improve performance. To achieve the potential of feedback, it is stated that teams need to proactively process this feedback and thus collectively evaluate their performance and strategies, look for…

  16. Electrophysiological brain indices of risk behavior modification induced by contingent feedback.

    Science.gov (United States)

    Megías, Alberto; Torres, Miguel Angel; Catena, Andrés; Cándido, Antonio; Maldonado, Antonio

    2018-02-01

    The main aim of this research was to study the effects of response feedback on risk behavior and the neural and cognitive mechanisms involved, as a function of the feedback contingency. Sixty drivers were randomly assigned to one of three feedback groups: contingent, non-contingent and no feedback. The participants' task consisted of braking or not when confronted with a set of risky driving situations, while their electroencephalographic activity was continuously recorded. We observed that contingent feedback, as opposed to non-contingent feedback, promoted changes in the response bias towards safer decisions. This behavioral modification implied a higher demand on cognitive control, reflected in a larger amplitude of the N400 component. Moreover, the contingent feedback, being predictable and entailing more informative value, gave rise to smaller SPN and larger FRN scores when compared with non-contingent feedback. Taken together, these findings provide a new and complex insight into the neurophysiological basis of the influence of feedback contingency on the processing of decision-making under risk. We suggest that response feedback, when contingent upon the risky behavior, appears to improve the functionality of the brain mechanisms involved in decision-making and can be a powerful tool for reducing the tendency to choose risky options in risk-prone individuals. Copyright © 2018 Elsevier B.V. All rights reserved.

  17. Distinct oxytocin effects on belief updating in response to desirable and undesirable feedback

    Science.gov (United States)

    Ma, Yina; Li, Shiyi; Wang, Chenbo; Liu, Yi; Li, Wenxin; Yan, Xinyuan; Chen, Qiang; Han, Shihui

    2016-01-01

    Humans update their beliefs upon feedback and, accordingly, modify their behaviors to adapt to the complex, changing social environment. However, people tend to incorporate desirable (better than expected) feedback into their beliefs but to discount undesirable (worse than expected) feedback. Such optimistic updating has evolved as an advantageous mechanism for social adaptation. Here, we examine the role of oxytocin (OT)―an evolutionary ancient neuropeptide pivotal for social adaptation―in belief updating upon desirable and undesirable feedback in three studies (n = 320). Using a double-blind, placebo-controlled between-subjects design, we show that intranasally administered OT (IN-OT) augments optimistic belief updating by facilitating updates of desirable feedback but impairing updates of undesirable feedback. The IN-OT–induced impairment in belief updating upon undesirable feedback is more salient in individuals with high, rather than with low, depression or anxiety traits. IN-OT selectively enhances learning rate (the strength of association between estimation error and subsequent update) of desirable feedback. IN-OT also increases participants’ confidence in their estimates after receiving desirable but not undesirable feedback, and the OT effect on confidence updating upon desirable feedback mediates the effect of IN-OT on optimistic belief updating. Our findings reveal distinct functional roles of OT in updating the first-order estimation and second-order confidence judgment in response to desirable and undesirable feedback, suggesting a molecular substrate for optimistic belief updating. PMID:27482087

  18. Distinct oxytocin effects on belief updating in response to desirable and undesirable feedback.

    Science.gov (United States)

    Ma, Yina; Li, Shiyi; Wang, Chenbo; Liu, Yi; Li, Wenxin; Yan, Xinyuan; Chen, Qiang; Han, Shihui

    2016-08-16

    Humans update their beliefs upon feedback and, accordingly, modify their behaviors to adapt to the complex, changing social environment. However, people tend to incorporate desirable (better than expected) feedback into their beliefs but to discount undesirable (worse than expected) feedback. Such optimistic updating has evolved as an advantageous mechanism for social adaptation. Here, we examine the role of oxytocin (OT)-an evolutionary ancient neuropeptide pivotal for social adaptation-in belief updating upon desirable and undesirable feedback in three studies (n = 320). Using a double-blind, placebo-controlled between-subjects design, we show that intranasally administered OT (IN-OT) augments optimistic belief updating by facilitating updates of desirable feedback but impairing updates of undesirable feedback. The IN-OT-induced impairment in belief updating upon undesirable feedback is more salient in individuals with high, rather than with low, depression or anxiety traits. IN-OT selectively enhances learning rate (the strength of association between estimation error and subsequent update) of desirable feedback. IN-OT also increases participants' confidence in their estimates after receiving desirable but not undesirable feedback, and the OT effect on confidence updating upon desirable feedback mediates the effect of IN-OT on optimistic belief updating. Our findings reveal distinct functional roles of OT in updating the first-order estimation and second-order confidence judgment in response to desirable and undesirable feedback, suggesting a molecular substrate for optimistic belief updating.

  19. Feedback på tekst i grupper

    DEFF Research Database (Denmark)

    Hvass, Helle; Heger, Stine

    2017-01-01

    med temaet Feedback på tekst i grupper er via aktiviteter at gøre de studerende bevidste om, at feedback er noget, de skal lære, og noget, de skal øve sig på. De forskellige aktiviteter sætter de studerende i gang med at skabe rammer for feedback, at træne feedback og at give og modtage feedback på...... hinandens tekster. Temaet er bygget op omkring 2 forskellige elementer: 1) forberedelse af feedback og 2) udførelse af feedback....

  20. Feedback suppression in digital hearing instruments

    DEFF Research Database (Denmark)

    Ma, Guilin

    . Methods to extract the fixed model are proposed and proved to be effective in representing the invariant part of the feedback path. Based on the investigation of the dynamic changes of the feedback path in adverse situations, for example when the user picks up the telephone handset, a reflection model...... is developed as one type of the fast varying models. The techniques to suppress the feedback are then reviewed. To improve the existing feedback suppression systems, two approaches are proposed to address the so-called “bias problem”. The first approach improves the performance of the adaptive feedback...... of the proposed feedback path models in the feedback cancellation systems is presented....

  1. Feedback control of retrograde peristalsis using Neural Gastric Electrical Stimulation.

    Science.gov (United States)

    Aelen, Paul; Aulanier, Anne-Lise; Mintchev, Martin P

    2008-01-01

    Neural Gastric Electrical Stimulation (NGES) is a new method for invoking gastric contractions under microprocessor control. However, optimization of this technique using feedback mechanisms to minimize power consumption and maximize effectiveness has been lacking. The present work proposes a prototype feedback-controlled neural gastric electrical stimulator for the treatment of obesity. Both a force-based and an interelectrode impedance-based feedback neurostimulator were implemented and tested. Four mongrel dogs (2 M, 2 F, weight 14.9 ++/- 2.3kg) underwent subserosal implantation of 2-channel 1-cm bipolar electrode leads in the distal antrum. Two of the dogs were stimulated with a force-based feedback system and the other two animals were stimulated utilizing an interelectrode impedance-based feedback system. Both feedback systems were able to recognize Erythromycin-driven contractions of the stomach and were capable of overriding them with NGES-invoked retrograde contractions. The proposed technique could be helpful for retaining food longer in the stomach, thus inducing early satiety and diminishing food intake.

  2. Optimal allocation of reviewers for peer feedback

    DEFF Research Database (Denmark)

    Wind, David Kofoed; Jensen, Ulf Aslak; Jørgensen, Rasmus Malthe

    2017-01-01

    to submissions in such a way that all submissions receive feedback of similar quality and that we are able to significantly outperform simple random allocation of reviewers. Additionally we investigate the effect of pre-allocating reviews in comparison to allocating reviewers live during the review process......Peer feedback is the act of letting students give feedback to each other on submitted work. There are multiple reasons to use peer feedback, including students getting more feedback, time saving for teachers and increased learning by letting students reflect on work by others. In order for peer...... feedback to be effective students should give and receive useful feedback. A key challenge in peer feedback is allocating the feedback givers in a good way. It is important that reviewers are allocated to submissions such that the feedback distribution is fair - meaning that all students receive good...

  3. ABCDEFG IS - the principle of constructive feedback.

    Science.gov (United States)

    Bhattarai, M

    2007-01-01

    Feedback is an integral part of any learning experience. Constructive feedback is a powerful instrument and facilitates the learner's professional and personal development. "ABCDEFG IS", a mnemonic for the principles of constructive feedback, stands for Amount of the information, Benefit of the trainees, Change behaviour, Descriptive language, Environment, Focused, Group check, Interpretation check, and Sharing information. The eight important steps of feedback are: Ensure prior information, Collect data, Make appropriate meeting arrangement, Begin by encouraging self assessment by the trainee, Highlight areas where the trainee is doing well, Give feedback, Handle reaction maintaining the dignity and Plan actions. Communication and reflection also share many of the principles and steps of constructive feedback and giving regular feedback, thus, helps to improve communication and reflection. The feedback provider would be able to provide genuine feedback by following the appropriate steps and principles of constructive feedback and realize how important and rewarding its role is in teaching learning activities.

  4. AGN feedback in dwarf galaxies?

    Science.gov (United States)

    Dashyan, Gohar; Silk, Joseph; Mamon, Gary A.; Dubois, Yohan; Hartwig, Tilman

    2018-02-01

    Dwarf galaxy anomalies, such as their abundance and cusp-core problems, remain a prime challenge in our understanding of galaxy formation. The inclusion of baryonic physics could potentially solve these issues, but the efficiency of stellar feedback is still controversial. We analytically explore the possibility of feedback from active galactic nuclei (AGNs) in dwarf galaxies and compare AGN and supernova (SN) feedback. We assume the presence of an intermediate-mass black hole within low-mass galaxies and standard scaling relations between the relevant physical quantities. We model the propagation and properties of the outflow and explore the critical condition for global gas ejection. Performing the same calculation for SNe, we compare the ability of AGNs and SNe to drive gas out of galaxies. We find that a critical halo mass exists below which AGN feedback can remove gas from the host halo and that the critical halo mass for an AGN is greater than the equivalent for SNe in a significant part of the parameter space, suggesting that an AGN could provide an alternative and more successful source of negative feedback than SNe, even in the most massive dwarf galaxies.

  5. Peer Feedback in Learning a Foreign Language in Facebook

    NARCIS (Netherlands)

    Akbari, E.; Simons, P.R.J.; Pilot, A.; Naderi, Ahmad

    2017-01-01

    Feedback can have different forms and functions depending on its objectives as well as its provider: teacher feedback, student feedback, peer feedback, written feedback, oral feedback, etc. One of the most constructive forms of feedback may be peer feedback, since it involves group learning (Van

  6. Feedback in Czech Language Courses for Foreigners

    OpenAIRE

    Plísková, Kamila

    2015-01-01

    This thesis explores teacher's feedback, its definition, types, and is specifically focused on feedback moves in context of teaching Czech as a foreign language. The aim of this thesis is to present current research on the feedback in the context of teaching a second/foreign language and describe how the feedback is used in Czech language courses for foreigners and what instruments teachers use for such purpose. The first part is focusing on the feedback as part of the educational dialogue an...

  7. Driving feedback : psychological factors influencing the effectiveness of feedback

    NARCIS (Netherlands)

    Dogan, Ebru

    2013-01-01

    Automobilisten rijden niet altijd veilig en duurzaam. Het geven van feedback wordt over het algemeen beschouwd als een kansrijke strategie om automobilisten bewust te maken van de gevolgen van hun gedrag, en om hun gedrag te veranderen. Er is tot nu toe echter weinig bekend over welke factoren de

  8. Linear feedback controls the essentials

    CERN Document Server

    Haidekker, Mark A

    2013-01-01

    The design of control systems is at the very core of engineering. Feedback controls are ubiquitous, ranging from simple room thermostats to airplane engine control. Helping to make sense of this wide-ranging field, this book provides a new approach by keeping a tight focus on the essentials with a limited, yet consistent set of examples. Analysis and design methods are explained in terms of theory and practice. The book covers classical, linear feedback controls, and linear approximations are used when needed. In parallel, the book covers time-discrete (digital) control systems and juxtapos

  9. Simulating feedbacks in land use and land cover change models

    NARCIS (Netherlands)

    Verburg, P.H.

    2006-01-01

    In spite of the many advances in land use and land cover change modelling over the past decade many challenges remain. One of these challenges relates to the explicit treatment of feedback mechanisms in descriptive models of the land use system. This paper argues for model-based analysis to explore

  10. Feedback for Simulation-Based Procedural Skills Training: A Meta-Analysis and Critical Narrative Synthesis

    Science.gov (United States)

    Hatala, Rose; Cook, David A.; Zendejas, Benjamin; Hamstra, Stanley J.; Brydges, Ryan

    2014-01-01

    Although feedback has been identified as a key instructional feature in simulation based medical education (SBME), we remain uncertain as to the magnitude of its effectiveness and the mechanisms by which it may be effective. We employed a meta-analysis and critical narrative synthesis to examine the effectiveness of feedback for SBME procedural…

  11. Air-sea interactions and cirrus cloud-radiation feedbacks on climate

    Science.gov (United States)

    Somerville, Richard C. J.; Iacobellis, Sam

    1988-01-01

    A single cloud-radiation feedback mechanism, which may play a role in the climate changes expected from increased atmospheric concentrations of carbon dioxide and other trace greenhouse gases, is described. An improved radiative-convective model was developed and used to study the role of cirrus clouds in the optical thickness feedback mechanism. The model includes prescribed relative humidity and ozone profiles and a surface energy balance. The results suggest that the cloud optical thickness feedback mechanism can cause a substantial reduction in the surface warming due to doubling CO2, even in the presence of cirrus clouds.

  12. [Peer feedback for trainers in general practice].

    Science.gov (United States)

    Damoiseaux, R A M J; Truijens, L

    2016-01-01

    In medical specialist training programmes it is common practice for residents to provide feedback to their medical trainers. The problem is that due to its anonymous nature, the feedback often lacks the specificity necessary to improve the performance of trainers. If anonymity is to be abolished, there is a need for residents to feel safe in giving their feedback. Another way to improve the performance of trainers might be peer feedback. For peer feedback it is necessary that trainers observe each other during their training sessions with the residents. In speciality training in general practice peer feedback is done in group sessions of 12 trainers. They show videos of their training sessions and get feedback from their fellow trainers. Trainers also visit each other in their practices to observe training sessions and provide feedback. In order to improve trainer performance there is a need for more focus on peer feedback in medical specialist training programmes.

  13. Feedback on household electricity consumption

    DEFF Research Database (Denmark)

    Grønhøj, Alice; Thøgersen, John

    2011-01-01

    with respect to lowering their energy consumption. In addition, the feedback stimulated social influences processes related to energy savings between spouses as well as between (teenage) children and their parents. Notably, families with teenage children appear to be particularly receptive to this type...

  14. Haptic feedback helps bipedal coordination

    NARCIS (Netherlands)

    Roelofsen, E.G.J.; Bosga, J.; Rosenbaum, D.A.; Nijhuis-Van der Sanden, M.W.G.; Hullegie, W.A.M.; Cingel, R.E. van; Meulenbroek, R.G.J.

    2016-01-01

    The present study investigated whether special haptic or visual feedback would facilitate the coordination of in-phase, cyclical feet movements of different amplitudes. Seventeen healthy participants sat with their feet on sliding panels that were moved externally over the same or different

  15. Feedback - closing the loop digitally

    International Nuclear Information System (INIS)

    Zagel, J.; Chase, B.

    1992-01-01

    Many feedback and feedforward systems are now using microprocessors within the loop. We describe the wide range of possibilities and problems that arise. We also propose some ideas for analysis and testing, including examples of motion control in the Flying Wire systems in Main Ring and Tevatron and Low Level RF control now being built for the Fermilab Linac upgrade. (author)

  16. Environmental Feedback and Spatial Conditioning

    DEFF Research Database (Denmark)

    Foged, Isak Worre; Poulsen, Esben Skouboe

    2010-01-01

    with structural integrity, where thermal energy flow through the prototype, to be understood as a membrane, can be controlled and the visual transparancy altered. The work shows performance based feedback systems and physical prototype models driven by information streaming, screening and application....

  17. LFSC - Linac Feedback Simulation Code

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Valentin; /Fermilab

    2008-05-01

    The computer program LFSC (Feedback Simulation Code>) is a numerical tool for simulation beam based feedback in high performance linacs. The code LFSC is based on the earlier version developed by a collective of authors at SLAC (L.Hendrickson, R. McEwen, T. Himel, H. Shoaee, S. Shah, P. Emma, P. Schultz) during 1990-2005. That code was successively used in simulation of SLC, TESLA, CLIC and NLC projects. It can simulate as pulse-to-pulse feedback on timescale corresponding to 5-100 Hz, as slower feedbacks, operating in the 0.1-1 Hz range in the Main Linac and Beam Delivery System. The code LFSC is running under Matlab for MS Windows operating system. It contains about 30,000 lines of source code in more than 260 subroutines. The code uses the LIAR ('Linear Accelerator Research code') for particle tracking under ground motion and technical noise perturbations. It uses the Guinea Pig code to simulate the luminosity performance. A set of input files includes the lattice description (XSIF format), and plane text files with numerical parameters, wake fields, ground motion data etc. The Matlab environment provides a flexible system for graphical output.

  18. Cardiac concomitants of feedback processing.

    NARCIS (Netherlands)

    Crone, E.A.; van der Veen, F.M.; van der Molen, M.W.; Somsen, R.J.; van Beek, B.; Jennings, J.R.

    2003-01-01

    This study examined the heart rate changes associated with positive and negative performance feedback in a probabilistic learning task derived from Holroyd and Coles (2002). In this task, 21 20-29 yr old college students were presented with six stimuli and asked to respond by pressing a left versus

  19. Tubuloglomerular feedback in Dahl rats

    DEFF Research Database (Denmark)

    Karlsen, F M; Leyssac, P P; Holstein-Rathlou, N H

    1998-01-01

    We have previously demonstrated a loss of autoregulation in Dahl salt-sensitive (Dahl-S) rats rendered hypertensive on a high-salt diet. To determine whether this was due to a decreased activity of either the myogenic or the tubuloglomerular feedback (TGF) response, we tested the TGF response...

  20. Providing Feedback: Practical Skills and Strategies.

    Science.gov (United States)

    Sarkany, David; Deitte, Lori

    2017-06-01

    Feedback is an essential component of education. It is designed to influence, reinforce, and change behaviors, concepts, and attitudes in learners. Although providing constructive feedback can be challenging, it is a learnable skill. The negative consequences of destructive feedback or lack of feedback all together are far-reaching. This article summarizes the components of constructive feedback and provides readers with tangible skills to enhance their ability to give effective feedback to learners and peers. Copyright © 2017 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

  1. Feedback options in nonlinear numerical finance

    DEFF Research Database (Denmark)

    Hugger, Jens; Mashayekhi, Sima

    2012-01-01

    Feedback options are options where information about the trading of the underlying asset is fed back into the pricing model. This results in nonlinear pricing models. A survey of the literature about feedback options in finance is presented. The pricing model for the full feedback option on an in......Feedback options are options where information about the trading of the underlying asset is fed back into the pricing model. This results in nonlinear pricing models. A survey of the literature about feedback options in finance is presented. The pricing model for the full feedback option...

  2. Control your anger! The neural basis of aggression regulation in response to negative social feedback.

    Science.gov (United States)

    Achterberg, Michelle; van Duijvenvoorde, Anna C K; Bakermans-Kranenburg, Marian J; Crone, Eveline A

    2016-05-01

    Negative social feedback often generates aggressive feelings and behavior. Prior studies have investigated the neural basis of negative social feedback, but the underlying neural mechanisms of aggression regulation following negative social feedback remain largely undiscovered. In the current study, participants viewed pictures of peers with feedback (positive, neutral or negative) to the participant's personal profile. Next, participants responded to the peer feedback by pressing a button, thereby producing a loud noise toward the peer, as an index of aggression. Behavioral analyses showed that negative feedback led to more aggression (longer noise blasts). Conjunction neuroimaging analyses revealed that both positive and negative feedback were associated with increased activity in the medial prefrontal cortex (PFC) and bilateral insula. In addition, more activation in the right dorsal lateral PFC (dlPFC) during negative feedback vs neutral feedback was associated with shorter noise blasts in response to negative social feedback, suggesting a potential role of dlPFC in aggression regulation, or top-down control over affective impulsive actions. This study demonstrates a role of the dlPFC in the regulation of aggressive social behavior. © The Author (2016). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  3. Dissociation between active and observational learning from positive and negative feedback in Parkinsonism.

    Science.gov (United States)

    Kobza, Stefan; Ferrea, Stefano; Schnitzler, Alfons; Pollok, Bettina; Südmeyer, Martin; Bellebaum, Christian

    2012-01-01

    Feedback to both actively performed and observed behaviour allows adaptation of future actions. Positive feedback leads to increased activity of dopamine neurons in the substantia nigra, whereas dopamine neuron activity is decreased following negative feedback. Dopamine level reduction in unmedicated Parkinson's Disease patients has been shown to lead to a negative learning bias, i.e. enhanced learning from negative feedback. Recent findings suggest that the neural mechanisms of active and observational learning from feedback might differ, with the striatum playing a less prominent role in observational learning. Therefore, it was hypothesized that unmedicated Parkinson's Disease patients would show a negative learning bias only in active but not in observational learning. In a between-group design, 19 Parkinson's Disease patients and 40 healthy controls engaged in either an active or an observational probabilistic feedback-learning task. For both tasks, transfer phases aimed to assess the bias to learn better from positive or negative feedback. As expected, actively learning patients showed a negative learning bias, whereas controls learned better from positive feedback. In contrast, no difference between patients and controls emerged for observational learning, with both groups showing better learning from positive feedback. These findings add to neural models of reinforcement-learning by suggesting that dopamine-modulated input to the striatum plays a minor role in observational learning from feedback. Future research will have to elucidate the specific neural underpinnings of observational learning.

  4. Time-dependent neural processing of auditory feedback during voice pitch error detection.

    Science.gov (United States)

    Behroozmand, Roozbeh; Liu, Hanjun; Larson, Charles R

    2011-05-01

    The neural responses to sensory consequences of a self-produced motor act are suppressed compared with those in response to a similar but externally generated stimulus. Previous studies in the somatosensory and auditory systems have shown that the motor-induced suppression of the sensory mechanisms is sensitive to delays between the motor act and the onset of the stimulus. The present study investigated time-dependent neural processing of auditory feedback in response to self-produced vocalizations. ERPs were recorded in response to normal and pitch-shifted voice auditory feedback during active vocalization and passive listening to the playback of the same vocalizations. The pitch-shifted stimulus was delivered to the subjects' auditory feedback after a randomly chosen time delay between the vocal onset and the stimulus presentation. Results showed that the neural responses to delayed feedback perturbations were significantly larger than those in response to the pitch-shifted stimulus occurring at vocal onset. Active vocalization was shown to enhance neural responsiveness to feedback alterations only for nonzero delays compared with passive listening to the playback. These findings indicated that the neural mechanisms of auditory feedback processing are sensitive to timing between the vocal motor commands and the incoming auditory feedback. Time-dependent neural processing of auditory feedback may be an important feature of the audio-vocal integration system that helps to improve the feedback-based monitoring and control of voice structure through vocal error detection and correction.

  5. Negative soil moisture-precipitation feedback in dry and wet regions.

    Science.gov (United States)

    Yang, Lingbin; Sun, Guoqing; Zhi, Lu; Zhao, Jianjun

    2018-03-05

    Soil moisture-precipitation (SM-P) feedback significantly influences the terrestrial water and energy cycles. However, the sign of the feedback and the associated physical mechanism have been debated, leaving a research gap regarding global water and climate changes. Based on Koster's framework, we estimate SM-P feedback using satellite remote sensing and ground observation data sets. Methodologically, the sign of the feedback is identified by the correlation between monthly soil moisture and next-month precipitation. The physical mechanism is investigated through coupling precipitation and soil moisture (P-SM), soil moisture ad evapotranspiration (SM-E) and evapotranspiration and precipitation (E-P) correlations. Our results demonstrate that although positive SM-P feedback is predominant over land, non-negligible negative feedback occurs in dry and wet regions. Specifically, 43.75% and 40.16% of the negative feedback occurs in the arid and humid climate zones. Physically, negative SM-P feedback depends on the SM-E correlation. In dry regions, evapotranspiration change is soil moisture limited. In wet regions, evapotranspiration change is energy limited. We conclude that the complex SM-E correlation results in negative SM-P feedback in dry and wet regions, and the cause varies based on the environmental and climatic conditions.

  6. Land-Atmosphere Feedback Experiment (LAFE) Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Wulfmeyer, Volker [University of Hohenheim; Turner, David [NOAA National Severe Storms Laboratory

    2016-07-01

    The Land-Atmosphere Feedback Experiment (LAFE; pronounced “la-fey”) deploys several state-of-the-art scanning lidar and remote sensing systems to the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Southern Great Plains (SGP) site. These instruments will augment the ARM instrument suite in order to collect a data set for studying feedback processes between the land surface and the atmosphere. The novel synergy of remote-sensing systems will be applied for simultaneous measurements of land-surface fluxes and horizontal and vertical transport processes in the atmospheric convective boundary layer (CBL). The impact of spatial inhomogeneities of the soil-vegetation continuum on land-surface-atmosphere (LSA) feedback will be studied using the scanning capability of the instrumentation. The time period of the observations is August 2017, because large differences in surface fluxes between different fields and bare soil can be observed, e.g., pastures versus fields where the wheat has already been harvested. The remote sensing system synergy will consist of three components: 1) The SGP water vapor and temperature Raman lidar (SRL), the SGP Doppler lidar (SDL), and the National Center for Atmospheric Research (NCAR) water vapor differential absorption lidar (DIAL) (NDIAL) mainly in vertical staring modes to measure mean profiles and gradients of moisture, temperature, and horizontal wind. They will also measure profiles of higher-order turbulent moments in the water vapor and wind fields and profiles of the latent heat flux. 2) A novel scanning lidar system synergy consisting of the National Oceanic and Atmospheric Administration (NOAA) High-Resolution Doppler lidar (HRDL), the University of Hohenheim (UHOH) water-vapor differential absorption lidar (UDIAL), and the UHOH temperature Raman lidar (URL). These systems will perform coordinated range-height indicator (RHI) scans from just above the canopy level to the

  7. Observational Signatures Of Agn Feedback Across Cosmic Time

    Science.gov (United States)

    Wylezalek, Dominika

    2017-06-01

    While many compelling models of AGN feedback exist, there is no clear data-driven picture of how winds are launched, how they propagate through the galaxy and what impact they have on the galactic gas. Recent work suggests that AGN luminosity plays an important role. The following described projects focus on understanding the power, reach and impact of feedback processes exerted by AGN of different power. I first describe recent efforts in our group of relating feedback signatures in powerful quasars to the specific star formation rate in their host galaxies, where our results are consistent with the AGN having a `negative' impact through feedback on the galaxies' star formation history. Feedback signatures seem to be best observable in gas-rich galaxies where the coupling of the AGN-driven wind to the gas is strongest, in agreement with recent simulations. But how and where does this quenching happen? Is it accomplished through the mechanical action of jets or through nuclear winds driven by radiation pressure? Finally, I show that AGN signatures and AGN-driven winds can be easily hidden and not be apparent in the integrated spectrum of a galaxy hosting a low/intermediate-luminosity AGN. Using data from the new SDSS-IV MaNGA survey, we have developed a new AGN selection algorithm tailored to IFU data and we are uncovering a much more nuanced picture of AGN activity allowing us to discover AGN signatures at large distances from the galaxy center. This implies that large IFU surveys, such as the SDSS-IV MaNGA survey, might uncover many previously unknown AGN and feedback signatures related to them. Outflows and feedback from low- and intermediate-luminosity AGN might have been underestimated in the past but can potentially significantly contribute to the AGN/host-galaxy self-regulation.

  8. Theory of feedback controlled brain stimulations for Parkinson's disease

    Science.gov (United States)

    Sanzeni, A.; Celani, A.; Tiana, G.; Vergassola, M.

    2016-01-01

    Limb tremor and other debilitating symptoms caused by the neurodegenerative Parkinson's disease are currently treated by administering drugs and by fixed-frequency deep brain stimulation. The latter interferes directly with the brain dynamics by delivering electrical impulses to neurons in the subthalamic nucleus. While deep brain stimulation has shown therapeutic benefits in many instances, its mechanism is still unclear. Since its understanding could lead to improved protocols of stimulation and feedback control, we have studied a mathematical model of the many-body neural network dynamics controlling the dynamics of the basal ganglia. On the basis of the results obtained from the model, we propose a new procedure of active stimulation, that depends on the feedback of the network and that respects the constraints imposed by existing technology. We show by numerical simulations that the new protocol outperforms the standard ones for deep brain stimulation and we suggest future experiments that could further improve the feedback procedure.

  9. The basis for cosmic ray feedback: Written on the wind

    Science.gov (United States)

    Zweibel, Ellen G.

    2017-05-01

    Star formation and supermassive black hole growth in galaxies appear to be self-limiting. The mechanisms for self-regulation are known as feedback. Cosmic rays, the relativistic particle component of interstellar and intergalactic plasma, are among the agents of feedback. Because cosmic rays are virtually collisionless in the plasma environments of interest, their interaction with the ambient medium is primarily mediated by large scale magnetic fields and kinetic scale plasma waves. Because kinetic scales are much smaller than global scales, this interaction is most conveniently described by fluid models. In this paper, I discuss the kinetic theory and the classical theory of cosmic ray hydrodynamics (CCRH) which follows from assuming cosmic rays interact only with self-excited waves. I generalize CCRH to generalized cosmic ray hydrodynamics, which accommodates interactions with extrinsic turbulence, present examples of cosmic ray feedback, and assess where progress is needed.

  10. Feedbacks and Acceleration of Global Change

    Science.gov (United States)

    Hay, William

    2014-05-01

    The burning of fossil fuels since the beginning of the Industrial revolution has increased the level of atmospheric CO2 by about 45 % over that of earlier times. The increasing greenhouse effect is augmented by a series of feedbacks; most have been positive, but a few are negative. The most important are 1) Slowing of the thermohaline circulation system; 2) Decreasing Atlantic to Pacific vapor transport; 3) Increasing Arctic river runoff; 4) Melting of Arctic sea ice; 5) Periodic replacement of the Arctic atmospheric high by a cyclonic low pressure system; 6) Increased exchange of waters between the Arctic and North Atlantic; 7) Lessening of the Northern Hemisphere ice-albedo feedback effect; 8) Addition of methane from melting permafrost; 9) Overall changes in the rate of ocean mixing; 10) Overall changes in vegetation cover of land; 11) Increase in the area covered by C4 vegetation; 12) Addition of nitrous oxide from agricultural practices; 13) Changes in insect populations and their effect on vegetation; 14) Wildfires; 15) Soot accumulation on snow and ice; 16) Accelerated melting of the Greenland Ice Sheet; 17) Changes in the East Antarctic Ice Sheet; 18) Closing of the ozone hole over Antarctica; 19) Decay of the West Antarctic Ice Sheet; 20) Expansion of Southern Ocean sea ice; 21) Slowing of the rate of organic matter sinking into the deep ocean; 22) Decrease in insolation reaching the surface of the Earth as a result of introduction of aerosols into the atmosphere; 23) Depletion of stratospheric ozone by nitrous oxide. The global and regional effects and relative importance of many of these feedbacks are uncertain, and they may change both in magnitude and sign with time. New and unexpected mechanisms are constantly being discovered. The uncertainties and complexity associated with climate system feedbacks are responsible for the acceleration of climate change beyond the rates predicted by numerical modeling. To add to the difficulties inherent in

  11. Feedback, Surveys, and Soviet Communication Theory.

    Science.gov (United States)

    Mickiewicz, Ellen

    1983-01-01

    Reports on how traditional feedback channels in the Soviet Union work and how public opinion surveys have caused Communist party leaders to assess and expand their feedback channels, particularly in the area of letters from private citizens. (PD)

  12. Neural correlates of feedback processing in toddlers

    NARCIS (Netherlands)

    Meyer, M.; Bekkering, H.; Janssen, D.J.C.; Bruijn, E.R.A. de; Hunnius, S.

    2014-01-01

    External feedback provides essential information for successful learning. Feedback is especially important for learning in early childhood, as toddlers strongly rely on external signals to determine the consequences of their actions. In adults, many electrophysiological studies have elucidated

  13. Feedback as real-time constructions

    DEFF Research Database (Denmark)

    Keiding, Tina Bering; Qvortrup, Ane

    2014-01-01

    The article offers a re-description of feedback and the significance of time in feedback constructions based on systems theory. It describes feedback as internal, real-time constructions in a learning system. From this perspective, feedback is neither immediate nor delayed, but occurs in the very...... instant it takes place. This article argues for a clear distinction between the timing of communicative events, such as responses that are provided as help for feedback constructions, and the feedback construction itself as an event in a psychic system. Although feedback is described as an internal......, system-relative construction, different teaching environments offer diverse conditions for feedback constructions. The final section of this article explores this idea with the help of examples from both synchronous, oral interaction and asynchronous, text-based interaction mediated by digital media....

  14. Reality and myths of AGN feedback

    Science.gov (United States)

    Husemann, Bernd; Harrison, Chris M.

    2018-03-01

    Feedback from active galactic nuclei (AGNs) remains controversial despite its wide acceptance as necessary to regulate massive galaxy growth. Consequently, we held a workshop in October 2017, at Leiden's Lorentz Center, to distinguish between the reality and myths of feedback.

  15. Feedback as real-time constructions

    DEFF Research Database (Denmark)

    Keiding, Tina Bering; Qvortrup, Ane

    2014-01-01

    This article offers a re-description of feedback and the significance of time in feedback constructions based on systems theory. It describes feedback as internal, real-time constructions in a learning system. From this perspective, feedback is neither immediate nor delayed, but occurs in the very...... instant it takes place. This article argues for a clear distinction between the timing of communicative events, such as responses that are provided as help for feedback constructions, and the feedback construction itself as an event in a psychic system. Although feedback is described as an internal......, system-relative construction, different teaching environments offer diverse conditions for feedback constructions. The final section of this article explores this idea with the help of examples from both synchronous oral interaction and asynchronous text-based interaction mediated by digital media....

  16. Finding Positive Feedback Loops in Environmental Models: A Mathematical Investigation

    Science.gov (United States)

    Sheikholeslami, R.; Razavi, S.

    2016-12-01

    Dynamics of most earth and environmental systems are generally governed by interactions between several hydrological (e.g., soil moisture and precipitation), geological (e.g., and erosion), geochemical (e.g., nutrient loading), and atmospheric (e.g., temperature) processes which operate on a range of spatio-temporal scales. These interactions create numerous feedback mechanisms with complex behaviours, and their understanding and representation can vary depending on the scale in space and/or time at which the system is analyzed. One of the most crucial characteristics of such complex systems is the existence of positive feedback loops. The presence of positive feedbacks may increase complexity, accelerate change, or trigger multiple stable states in the underlying dynamical system. Furthermore, because of the inherent non-linearity, it is often very difficult to obtain a general idea of their complex dynamics. Feedback loops in environmental systems have been well recognized and qualitatively discussed. With a quantitative/mathematical view, in this presentation, we address the question of how the positive feedback loops can be identified/implemented in environmental models. We investigate the nature of different feedback mechanisms and dynamics of simple example case studies that underlie fundamental processes such as vegetation, precipitation and soil moisture. To do this, we apply the concept of "interaction graph" from mathematics which is built from the Jacobian matrix of the dynamical system. The Jacobian matrix contains information on how variations of one state variable depends on variations of other variables, and thus can be used to understand the dynamical possibilities of feedback mechanisms in the underlying system. Moreover, this study highlights that there are some situations where the existence of positive feedback loops can cause multiple stable states, and thereby regime shifts in environmental systems. Systems with multiple stable states are

  17. Fast Flux Test Facility (FFTF) feedback reactivity components

    International Nuclear Information System (INIS)

    Nguyen, D.H.

    1988-04-01

    The static tests conducted during Cycle 8A (1986) of the FFTF have allowed, for the first time, the experimental determination of each of the feedback reactivities caused by the following mechanisms: fuel axial expansion, control rod repositioning, core radial expansion, and subassembly bowing. A semiempirical equation was obtained to describe each of these feedback components that depended only on the relevant reactor temperature (bowing was presented in a tabular form). The Doppler and sodium density reactivities were calculated using existing mechanistic methods. Although they could also be fitted with closed-form equations depending only on temperatures, these equations are not needed in transient analyses using whole core safety computer codes, which use mechanistic methods. The static feedback reactivity model was extended to obtain a dynamic model via the concept of ''time constants.'' Besides being used for transient analyses in the FFTF, these feedback equations constitute a database for the validation and/or calibration of mechanistic feedback reactivity models. 2 refs., 6 tabs

  18. Social closeness and feedback modulate susceptibility to the framing effect.

    Science.gov (United States)

    Sip, Kamila E; Smith, David V; Porcelli, Anthony J; Kar, Kohitij; Delgado, Mauricio R

    2015-01-01

    Although we often seek social feedback (SFB) from others to help us make decisions, little is known about how SFB affects decisions under risk, particularly from a close peer. We conducted two experiments using an established framing task to probe how decision-making is modulated by SFB valence (positive, negative) and the level of closeness with feedback provider (friend, confederate). Participants faced mathematically equivalent decisions framed as either an opportunity to keep (gain frame) or lose (loss frame) part of an initial endowment. Periodically, participants were provided with positive (e.g., "Nice!") or negative (e.g., "Lame!") feedback about their choices. Such feedback was provided by either a confederate (Experiment 1) or a gender-matched close friend (Experiment 2). As expected, the framing effect was observed in both experiments. Critically, an individual's susceptibility to the framing effect was modulated by the valence of the SFB, but only when the feedback provider was a close friend. This effect was reflected in the activation patterns of ventromedial prefrontal cortex and posterior cingulate cortex, regions involved in complex decision-making. Taken together, these results highlight social closeness as an important factor in understanding the impact of SFB on neural mechanisms of decision-making.

  19. Buckling feedback of the spectral calculations

    International Nuclear Information System (INIS)

    Jing Xingqing; Shan Wenzhi; Luo Jingyu

    1992-01-01

    This paper studies the problems about buckling feedback of spectral calculations in physical calculations of the reactor and presents a useful method by which the buckling feedback of spectral calculations is implemented. The effect of the buckling feedback in spectra and the broad group cross section, convergence of buckling feedback iteration and the effect of the spectral zones dividing are discussed in the calculations. This method has been used for the physical design of HTR-10 MW Test Module

  20. Resonant passive–active vibration absorber with integrated force feedback control

    DEFF Research Database (Denmark)

    Høgsberg, Jan Becker; Brodersen, Mark Laier; Krenk, Steen

    2016-01-01

    realized passively by a mechanical inerter or actively by the integrated force feedback. Accurate calibration formulae are presented for two particular absorber configurations and the performance is subsequently demonstrated with respect to both equal modal damping and effective response reduction....

  1. Feedback control of resistive instabilities

    International Nuclear Information System (INIS)

    White, R.B.; Rutherford, P.H.; Furth, H.P.; Park, W.; Chen, L.

    1985-12-01

    Resistive instabilities are responsible for much of the global behavior and the determination of the possible domains of operation of tokamaks. Their successful control could have definite advantages, even making available new regimes of operation. Elimination of sawtoothing might allow operation with higher currents and more peaked current profiles, with q on axis well below unity. In this work different feedback schemes are explored. Simple analytical derivations of the effects of local heating and current drive feedback are presented. Although control of modes with m greater than or equal to 2 is fairly straightforward, the control of the m = 1 mode is more difficult because of its proximity to ideal instability. The most promising scheme utilizes high energy trapped particles. 20 refs., 3 figs

  2. Skill learning from kinesthetic feedback.

    Science.gov (United States)

    Pinzon, David; Vega, Roberto; Sanchez, Yerly Paola; Zheng, Bin

    2017-10-01

    It is important for a surgeon to perform surgical tasks under appropriate guidance from visual and kinesthetic feedback. However, our knowledge on kinesthetic (muscle) memory and its role in learning motor skills remains elementary. To discover the effect of exclusive kinesthetic training on kinesthetic memory in both performance and learning. In Phase 1, a total of twenty participants duplicated five 2 dimensional movements of increasing complexity via passive kinesthetic guidance, without visual or auditory stimuli. Five participants were asked to repeat the task in the Phase 2 over a period of three weeks, for a total of nine sessions. Subjects accurately recalled movement direction using kinesthetic memory, but recalling movement length was less precise. Over the nine training sessions, error occurrence dropped after the sixth session. Muscle memory constructs the foundation for kinesthetic training. Knowledge gained helps surgeons learn skills from kinesthetic information in the condition where visual feedback is limited. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. 360-degree feedback for medical trainees

    DEFF Research Database (Denmark)

    Holm, Ellen; Holm, Kirsten; Sørensen, Jette Led

    2015-01-01

    In 360-degree feedback medical colleagues and collaborators give a trainee feedback by answering a questionnaire on behaviour of the trainee. The questionnaire may contain questions answered on a scale or/and they may contain open questions. The result from 360-degree feedback is used for formative...

  4. Generic Online Multimodal Feedback on Summative Assessments

    OpenAIRE

    Sadoux, Marion

    2010-01-01

    Feedback has become a buzzword in Higher Education in the United Kingdom. As successive National Students’ Surveys show current feedback practices as a source of discontent rather than reassurance and guidance, the question of what good feedback should or could be has come under tight scrutiny by academics and students alike.

  5. Force feedback and basic laparoscopic skills

    NARCIS (Netherlands)

    Chmarra, M.K.; Dankelman, J.; Van den Dobbelsteen, J.J.; Jansen, F.W.

    2008-01-01

    Background - Not much is known about the exact role offorce feedback in laparoscopy. This study aimed to determine whether force feedback influences movements of instruments during training in laparoscopic tasks and whether force feedback is required for training in basic laparoscopic force

  6. Feedback options in nonlinear numerical finance

    DEFF Research Database (Denmark)

    Hugger, Jens; Mashayekhi, Sima

    2012-01-01

    Feedback options are options where information about the trading of the underlying asset is fed back into the pricing model. This results in nonlinear pricing models. A survey of the literature about feedback options in finance is presented. The pricing model for the full feedback option...

  7. Chat-Line Interaction and Negative Feedback.

    Science.gov (United States)

    Iwasaki, Junko; Oliver, Rhonda

    2003-01-01

    Examines communicative interactions between native speakers (NSs) and nonnative speakers (NNSs) of Japanese on Internet relay chat, with a special focus on implicit negative feedback in the interactions. Reports that NSs of Japanese gave implicit negative feedback to their NNS partners and NNSs used the feedback in their subsequent production, but…

  8. The Art of Giving Online Feedback

    Science.gov (United States)

    Leibold, Nancyruth; Schwarz, Laura Marie

    2015-01-01

    The cultivation of providing online feedback that is positive, effective, and enhances the learning experience is a valuable educator skill. Acquisition of the art of providing feedback is through education, practice, and faculty development. This article provides information about the best practices for delivering online feedback to learners. An…

  9. Effectiveness of Feedback in First Year Physics

    DEFF Research Database (Denmark)

    Bearden, Ian; Voigt, Karen A; Mathiasen, Helle

    How can we provide better and more effective feedback to our students? How can we encourage students to use feedback effectively? We will present results of a study of first year physics students addressing these questions and comparing the effectiveness of written and screencast feedback....

  10. Coaching Medical Students in Receiving Effective Feedback.

    Science.gov (United States)

    Bing-You, Robert G.; Bertsch, Tania; Thompson, Janet A.

    1998-01-01

    A study assessed effectiveness of instruction designed to train internal-medical-clerkship students in productive use of feedback from residents and attending physicians (APs) to improve performance. The workshop focused on writing goals in a learning contract, defining characteristics of effective feedback, and practicing use of feedback in…

  11. Stellar Feedback from Galactic Bulges

    Science.gov (United States)

    Tang, Shikui; Wang, D. Q.

    2009-01-01

    We demonstrate that feedback from galactic bulges can play an essential role in the halo gas dynamics and the evolution of their host galaxies by conducting a series of 1-D and 3-D simulations. In our 1-D models we approximately divide the the bulge stellar feedback into two phases: 1) a starbusrt-induced blastwave from the formation of bulge built up through frequent major mergers at high redshift and 2) a gradual feedback in forms of stellar wind and Type Ia SNe from low mass stars. Our simulations show that the combination of the two-phase feedback can heat the surrounding gas beyond the virial radius and stop further gas accretion, which naturally produces a baryon deficit around MW-like galaxies and explains the lack of large-scale X-ray halos, consistent with observations. The hot gas dynamics depends sensitively on the environment and bulge formation history. This dependency may account for the large dispersion in the X-ray luminosities of the galaxies with similar L_B. In the 3-D simulations, we examine the spatial, thermal, and chemical substructures and their effects on X-ray measurements. The sporadic SN explosion creates wealth of filamentary and shell-like structures in the hot gas and produces a broad lognormal-like emission-measure distribution, which enhances the X-ray emission at a low and high temperatures. The luminosity at 0.3-2.0 keV band is nearly tripled due to the gas structures. We find that the SN Ia ejecta are not well-mixed with the ambient medium within the bulge scale, and the X-ray emission is primarily from shocked stellar wind materials which in general has low metallicity.

  12. Rf Feedback free electron laser

    Science.gov (United States)

    Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

    1981-01-01

    A free electron laser system and electron beam system for a free electron laser which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

  13. Written feedback to mathematics homework

    OpenAIRE

    Žitko, Urša

    2017-01-01

    This diploma thesis is about teachers’ feedback to students’ mathematics homework. In the theoretical part I present the purpose and history of homework assignments as well as various classifications of types of homework. In general, homework assignments are intended for students to learn and refresh the subject matter they have learnt in class, to gain further understanding, to practice various mathematical processes, and to prepare the student for a forthcoming subject matter. By doing home...

  14. Ecogeomorphic Feedbacks that Grow Deltas

    Science.gov (United States)

    Ma, H.; Larsen, L.; Wagner, W.

    2017-12-01

    Coastal river deltas are complex and dynamic ecosystems where vegetation plays an essential role in influencing (as well as being influenced by) physical processes, creating a strong potential for ecogeomorphic feedbacks. However, understanding of the relative strenghts of feedback between vegetation species and topography along different portions of the marsh elevation/zonation gradient is poorly developed, particularly for freshwater, deltaic marshes. In part, this knowledge gap is due to difficulties associated with adequate sampling within heterogeneous vegetation communities to delineate bi-directional feedback applicable at the delta scale.. Emerging technology (high resolution remote sensing and high resolution LiDAR) and data analysis techniques like transfer entropy have made it possible to overcome these difficulties. Here, results of the transfer entropy analysis were consistent with widespread understanding of marsh zonation, yet produced additional insight into which vegetation communities specifically had a dominant impact on topographic change. Ecogeomorphic feedback that has a substantial short-term impact on evolving topography was resolvable only within native vegetation communities (Nelumbo lutea and Polygonum spp.) that occur over low to moderate elevations within the Wax Lake Delta tidal prism. In contrast, nonnative vegetation communities (Colocasia esculenta and Eichhonia crasspies) are not as functional at accreting sediment as native communities. The transfer entropy analysis suggests that different vegetation communities play functionally different roles in landscape evolution that should be differentiated in a model. Within such a model, it would be most critical to resolve detailed flow characteristics at low to low-middle island elevations, where submerged aquatic vegetation and Nelumbo are abundant, as these communities exert the strongest influence on topographic change. Furthermore, within elevation zones, it is likely important to

  15. Feedback regulation between autophagy and PKA.

    Science.gov (United States)

    Torres-Quiroz, Francisco; Filteau, Marie; Landry, Christian R

    2015-01-01

    Protein kinase A (PKA) controls diverse cellular processes and homeostasis in eukaryotic cells. Many processes and substrates of PKA have been described and among them are direct regulators of autophagy. The mechanisms of PKA regulation and how they relate to autophagy remain to be fully understood. We constructed a reporter of PKA activity in yeast to identify genes affecting PKA regulation. The assay systematically measures relative protein-protein interactions between the regulatory and catalytic subunits of the PKA complex in a systematic set of genetic backgrounds. The candidate PKA regulators we identified span multiple processes and molecular functions (autophagy, methionine biosynthesis, TORC signaling, protein acetylation, and DNA repair), which themselves include processes regulated by PKA. These observations suggest the presence of many feedback loops acting through this key regulator. Many of the candidate regulators include genes involved in autophagy, suggesting that not only does PKA regulate autophagy but that autophagy also sends signals back to PKA.

  16. LFSC - Linac Feedback Simulation Code

    International Nuclear Information System (INIS)

    Ivanov, Valentin; Fermilab

    2008-01-01

    The computer program LFSC ( ) is a numerical tool for simulation beam based feedback in high performance linacs. The code LFSC is based on the earlier version developed by a collective of authors at SLAC (L.Hendrickson, R. McEwen, T. Himel, H. Shoaee, S. Shah, P. Emma, P. Schultz) during 1990-2005. That code was successively used in simulation of SLC, TESLA, CLIC and NLC projects. It can simulate as pulse-to-pulse feedback on timescale corresponding to 5-100 Hz, as slower feedbacks, operating in the 0.1-1 Hz range in the Main Linac and Beam Delivery System. The code LFSC is running under Matlab for MS Windows operating system. It contains about 30,000 lines of source code in more than 260 subroutines. The code uses the LIAR ('Linear Accelerator Research code') for particle tracking under ground motion and technical noise perturbations. It uses the Guinea Pig code to simulate the luminosity performance. A set of input files includes the lattice description (XSIF format), and plane text files with numerical parameters, wake fields, ground motion data etc. The Matlab environment provides a flexible system for graphical output

  17. Augmented feedback in autistic disorder

    Directory of Open Access Journals (Sweden)

    Salome Geertsema

    2017-10-01

    Full Text Available Children with autistic disorder (AD display atypical eye contact and struggle with the social imitation of eye contact. Impaired social imitation may be indicative of disruptions in motor learning processes. The application of specific motor learning principles, such as external feedback, may suggest which variables will result in positive change in eye contact. The study aimed to determine the effects of knowledge of performance (KP and knowledge of results (KR as types of feedback on the frequency and duration of elicited and spontaneous eye contact in children with AD. A two-phase multiple-probe, multi-treatment (cross-over, singleparticipant design with a withdrawal component was used. Mixed treatment effects were obtained. Overall effects suggest that KR results in the greatest positive change over a short period of time regarding frequency and duration for both elicited and spontaneous eye contact. This type of feedback seems to be the most effective for spontaneous eye contact. The provision of KP, after elicited and spontaneous eye contact, produced positive effects for duration only. The current Phase 1 evidence suggests that KR (which is goal-directed with fewer additional instructions may be more beneficial to children with AD. These findings are in accordance with the limb motor learning literature and may therefore support preliminary evidence for disrupted motor learning during eye contact imitation in children with AD.

  18. Development of the Teacher Feedback Observation Scheme: evaluating the quality of feedback in peer groups

    NARCIS (Netherlands)

    Thurlings, Marieke; Vermeulen, Marjan; Kreijns, Karel; Bastiaens, Theo; Stijnen, Sjef

    2018-01-01

    Research suggests that feedback is an essential element in learning. This study focuses on feedback that teachers provide in reciprocal peer groups to improve their performance in the classroom. The Teacher Feedback Observation Scheme (TFOS) was developed to identify feedback patterns, which

  19. Interpreting Feedback: A Discourse Analysis of Teacher Feedback and Student Identity

    Science.gov (United States)

    Torres, J. T.; Anguiano, Carlos J.

    2016-01-01

    Feedback has typically been studied as a means of improving academic performance. Few studies inquire into the processes by which feedback shapes student identity. The authors carry out a discourse analysis of written comments to explore how feedback is discursively constructed by both teachers and students. Analysis of written feedback,…

  20. Feedbacks stablizing wetland geometry on a pattened landscape

    Science.gov (United States)

    Dong, X.; Heffernan, J. B.; Murray, A. B.

    2017-12-01

    Karst morphology is highly varied across different climatic and geologic regions of the world. Big Cypress National Preserve in SW Florida, features regularly distributed wetland depressions, located on exposed limestone bedrock. In this study, we explored the development of wetland depressions over the past 10kyrs of landscape formation. Specifically, we are interested in (1) whether the wetland depressions on the landscape have reached equilibrium size, and (2) if so, what are feedback mechanisms that contributed to stabilizing these depressions. We hypothesized three stabilizing feedback mechanisms. HYP1: increased size of depressions reduces landscape hydrological connectivity, which resulted in reduced landscape capacity to export dissolution products, hence lower weathering rate. HYP2: expansion of depression area increases tree biomass within the depression, which increased average evapotranspiration (ET) within the dome. The greater difference of ET rate between depression and upland leads to a lower water table in the depression. As a result, more subsurface water, carrying dissolved calcium, flows from catchment to depression. With lower export capacity and more calcium moving into the depression zones, rate of calcite precipitation increases, which lowers net weathering rate. HYP3: increasingly thicker sediment cover in the wetland depression over time decreases chemical transport capacity. This lowers both transport of CO2 from shallower soil to bedrock and transport of dissolution products from bedrock to surface. Both of these processes reduce bedrock-weathering rate. We built a 3-D numerical simulation model that partitioned the relative importance of different mechanisms. Preliminary results show that (1) there is an equilibrium size for wetland depressions for both radius and depth dimension; (2) current depressions are formed by coalescence of several nearby small depressions during development; (3) the soil cover feedback (HYP3) is the major

  1. 360-degree feedback for medical trainees

    DEFF Research Database (Denmark)

    Holm, Ellen; Holm, Kirsten; Sørensen, Jette Led

    2015-01-01

    In 360-degree feedback medical colleagues and collaborators give a trainee feedback by answering a questionnaire on behaviour of the trainee. The questionnaire may contain questions answered on a scale or/and they may contain open questions. The result from 360-degree feedback is used for formative...... feedback and assessment. In order to secure reliability 8-15 respondents are needed. It is a matter of discussion whether the respondents should be chosen by the trainee or by a third part, and if respondents should be anonymous. The process includes a feedback session with a trained supervisor....

  2. Exploring the value of usability feedback formats

    DEFF Research Database (Denmark)

    Nørgaard, Mie; Hornbæk, Kasper Anders Søren

    2009-01-01

    presented using five feedback formats. Our usability findings comprise 35 problems and 5 positive comments. Data suggest that feedback serves multiple purposes. Initially, feedback must convince developers about the relevance of a problem and convey an understanding of this. Feedback must next be easy...... working with the feedback to address the usability problems, there were no significant differences among the developers' ratings of the value of the different formats. This suggests that all of the formats may serve equally well as reminders in later stages of working with usability problems...

  3. Electrotactile EMG feedback improves the control of prosthesis grasping force

    Science.gov (United States)

    Schweisfurth, Meike A.; Markovic, Marko; Dosen, Strahinja; Teich, Florian; Graimann, Bernhard; Farina, Dario

    2016-10-01

    Objective. A drawback of active prostheses is that they detach the subject from the produced forces, thereby preventing direct mechanical feedback. This can be compensated by providing somatosensory feedback to the user through mechanical or electrical stimulation, which in turn may improve the utility, sense of embodiment, and thereby increase the acceptance rate. Approach. In this study, we compared a novel approach to closing the loop, namely EMG feedback (emgFB), to classic force feedback (forceFB), using electrotactile interface in a realistic task setup. Eleven intact-bodied subjects and one transradial amputee performed a routine grasping task while receiving emgFB or forceFB. The two feedback types were delivered through the same electrotactile interface, using a mixed spatial/frequency coding to transmit 8 discrete levels of the feedback variable. In emgFB, the stimulation transmitted the amplitude of the processed myoelectric signal generated by the subject (prosthesis input), and in forceFB the generated grasping force (prosthesis output). The task comprised 150 trials of routine grasping at six forces, randomly presented in blocks of five trials (same force). Interquartile range and changes in the absolute error (AE) distribution (magnitude and dispersion) with respect to the target level were used to assess precision and overall performance, respectively. Main results. Relative to forceFB, emgFB significantly improved the precision of myoelectric commands (min/max of the significant levels) for 23%/36% as well as the precision of force control for 12%/32%, in intact-bodied subjects. Also, the magnitude and dispersion of the AE distribution were reduced. The results were similar in the amputee, showing considerable improvements. Significance. Using emgFB, the subjects therefore decreased the uncertainty of the forward pathway. Since there is a correspondence between the EMG and force, where the former anticipates the latter, the emgFB allowed for

  4. The Impact of Feedback on the Different Time Courses of Multisensory Temporal Recalibration

    Directory of Open Access Journals (Sweden)

    Matthew A. De Niear

    2017-01-01

    Full Text Available The capacity to rapidly adjust perceptual representations confers a fundamental advantage when confronted with a constantly changing world. Unexplored is how feedback regarding sensory judgments (top-down factors interacts with sensory statistics (bottom-up factors to drive long- and short-term recalibration of multisensory perceptual representations. Here, we examined the time course of both cumulative and rapid temporal perceptual recalibration for individuals completing an audiovisual simultaneity judgment task in which they were provided with varying degrees of feedback. We find that in the presence of feedback (as opposed to simple sensory exposure temporal recalibration is more robust. Additionally, differential time courses are seen for cumulative and rapid recalibration dependent upon the nature of the feedback provided. Whereas cumulative recalibration effects relied more heavily on feedback that informs (i.e., negative feedback rather than confirms (i.e., positive feedback the judgment, rapid recalibration shows the opposite tendency. Furthermore, differential effects on rapid and cumulative recalibration were seen when the reliability of feedback was altered. Collectively, our findings illustrate that feedback signals promote and sustain audiovisual recalibration over the course of cumulative learning and enhance rapid trial-to-trial learning. Furthermore, given the differential effects seen for cumulative and rapid recalibration, these processes may function via distinct mechanisms.

  5. Influence of feedback characteristics on perceived learning value of feedback in clerkships: does culture matter?

    OpenAIRE

    Suhoyo, Yoyo; Van Hell, Elisabeth A.; Kerdijk, Wouter; Emilia, Ova; Sch?nrock-Adema, Johanna; Kuks, Jan B. M.; Cohen-Schotanus, Janke

    2017-01-01

    Background: Various feedback characteristics have been suggested to positively influence student learning. It is not clear how these feedback characteristics contribute to students' perceived learning value of feedback in cultures classified low on the cultural dimension of individualism and high on power distance. This study was conducted to validate the influence of five feedback characteristics on students' perceived learning value of feedback in an Indonesian clerkship context. Methods: W...

  6. The Effects of Visual Feedback Distortion with Unilateral Leg Loading on Gait Symmetry.

    Science.gov (United States)

    Tobar, Carlos; Martinez, Eva; Rhouni, Nada; Kim, Seung-Jae

    2018-02-01

    Our prior work provides evidence that visual feedback distortion drives an implicit adaptation; a gradual distortion of visual representation of step length modulated subjects' step lengths away from symmetry. To further explore the effect of the visual feedback distortion on unconscious change in step symmetry, we investigated whether such adaptation would occur even in the presence of altered limb mechanics by adding mass to one side of the leg. 26 subjects performed three 8-min trials (weight only, weight plus visual feedback, and weight plus visual feedback distortion) of treadmill walking. During the weight only trial, the subjects wore a 5 lb mass around the right ankle. The modification of limb inertia caused asymmetric gait. The visual feedback showing right and left step length information as bar graphs was displayed on a computer screen. To add visual feedback distortion, we increased the length of one side of the visual bars by 10% above the actual step length, and the visual distortion was implemented for the side that took longer in response to the added mass. We found that even when adjustments were made to unilateral loading, the subjects spontaneously changed their step symmetry in response to the visual distortion, which resulted in a more symmetric gait. This change may be characterized by sensory prediction errors, and our results suggest that visual feedback distortion has a significant impact on gait symmetry regardless of other conditions affecting limb mechanics. A rehabilitation program employing visual feedback distortion may provide an effective way to restore gait symmetry.

  7. Noise propagation in gene regulation networks involving interlinked positive and negative feedback loops.

    Directory of Open Access Journals (Sweden)

    Hui Zhang

    Full Text Available It is well known that noise is inevitable in gene regulatory networks due to the low-copy numbers of molecules and local environmental fluctuations. The prediction of noise effects is a key issue in ensuring reliable transmission of information. Interlinked positive and negative feedback loops are essential signal transduction motifs in biological networks. Positive feedback loops are generally believed to induce a switch-like behavior, whereas negative feedback loops are thought to suppress noise effects. Here, by using the signal sensitivity (susceptibility and noise amplification to quantify noise propagation, we analyze an abstract model of the Myc/E2F/MiR-17-92 network that is composed of a coupling between the E2F/Myc positive feedback loop and the E2F/Myc/miR-17-92 negative feedback loop. The role of the feedback loop on noise effects is found to depend on the dynamic properties of the system. When the system is in monostability or bistability with high protein concentrations, noise is consistently suppressed. However, the negative feedback loop reduces this suppression ability (or improves the noise propagation and enhances signal sensitivity. In the case of excitability, bistability, or monostability, noise is enhanced at low protein concentrations. The negative feedback loop reduces this noise enhancement as well as the signal sensitivity. In all cases, the positive feedback loop acts contrary to the negative feedback loop. We also found that increasing the time scale of the protein module or decreasing the noise autocorrelation time can enhance noise suppression; however, the systems sensitivity remains unchanged. Taken together, our results suggest that the negative/positive feedback mechanisms in coupled feedback loop dynamically buffer noise effects rather than only suppressing or amplifying the noise.

  8. Technologies for learner-centered feedback

    Directory of Open Access Journals (Sweden)

    Jane Costello

    2013-09-01

    Full Text Available As the number, type, and use of technologies to support learning increases, so do the opportunities for using these technologies for feedback. Learner-centered feedback is a core to the teaching-learning process. It is related to assessment in describing how learners perform in their learning, their gain in knowledge, skills, and attitudes. Feedback, types of feedback, guidelines for effective learner-centered feedback, and feedback’s relationship to assessment are presented. Methods of providing feedback, for example, automated, audio scribe pens, digital audio, etc., and the related technologies are described. Technologies that allow instructors to make informed decisions about the use of various methods for feedback are discussed.

  9. Modeling terrestrial gamma ray flashes produced by relativistic feedback discharges

    Science.gov (United States)

    Liu, Ningyu; Dwyer, Joseph R.

    2013-05-01

    This paper reports a modeling study of terrestrial gamma ray flashes (TGFs) produced by relativistic feedback discharges. Terrestrial gamma ray flashes are intense energetic radiation originating from the Earth's atmosphere that has been observed by spacecraft. They are produced by bremsstrahlung interactions of energetic electrons, known as runaway electrons, with air atoms. An efficient physical mechanism for producing large fluxes of the runaway electrons to make the TGFs is the relativistic feedback discharge, where seed runaway electrons are generated by positrons and X-rays, products of the discharge itself. Once the relativistic feedback discharge becomes self-sustaining, an exponentially increasing number of relativistic electron avalanches propagate through the same high-field region inside the thundercloud until the electric field is partially discharged by the ionization created by the discharge. The modeling results indicate that the durations of the TGF pulses produced by the relativistic feedback discharge vary from tens of microseconds to several milliseconds, encompassing all durations of the TGFs observed so far. In addition, when a sufficiently large potential difference is available in thunderclouds, a self-propagating discharge known as the relativistic feedback streamer can be formed, which propagates like a conventional positive streamer. For the relativistic feedback streamer, the positive feedback mechanism of runaway electron production by the positrons and X-rays plays a similar role as the photoionization for the conventional positive streamer. The simulation results of the relativistic feedback streamer show that a sequence of TGF pulses with varying durations can be produced by the streamer. The relativistic streamer may initially propagate with a pulsed manner and turn into a continuous propagation mode at a later stage. Milliseconds long TGF pulses can be produced by the feedback streamer during its continuous propagation. However

  10. Practice of knowledge management for institutes--take the construction of experience feedback system as the example

    International Nuclear Information System (INIS)

    Wu Kaiping

    2014-01-01

    The construction of experience feedback system is an important part and breakthrough point of institutes' knowledge management. It is significant for institutes' design, management, development and innovation. This article introduces the concept of experience feedback for institutes. It also goes details of the content of experience feedback system construction for institutes, including the founding of experience feedback organizational mechanism, the development of experience feedback system, construction of knowledge database system, the construction of knowledge resources, and the appraisal of experience feedback's performance. Furthermore, the recognition and support of leaders, understanding and cooperation of relative departments, and corporation's culture of encouraging knowledge sharing, also are the important guarantees for the good effects of institutes' experience feedback work. (author)

  11. Flexible Multi-Bit Feedback Design for HARQ Operation of Large-Size Data Packets in 5G

    DEFF Research Database (Denmark)

    Khosravirad, Saeed; Mudolo, Luke; Pedersen, Klaus I.

    2017-01-01

    large-size data packet thanks to which the transmitter node can reduce the retransmission size to only include the initially failed segments of the packet. We study the effect of feedback size on retransmission efficiency through extensive link-level simulations over realistic channel models. Numerical......A reliable feedback channel is vital to report decoding acknowledgments in retransmission mechanisms such as the hybrid automatic repeat request (HARQ). While the feedback bits are known to be costly for the wireless link, a feedback message more informative than the conventional single......-bit feedback can increase resource utilization efficiency. Considering the practical limitations for increasing feedback message size, this paper proposes a framework for the design of flexible-content multi-bit feedback. The proposed design is capable of efficiently indicating the faulty segments of a failed...

  12. Experiments with positive, negative and topical relevance feedback

    NARCIS (Netherlands)

    Kaptein, R.; Kamps, J.; Li, R.; Hiemstra, D.

    2008-01-01

    This document contains a description of experiments for the 2008 Relevance Feedback track. We experiment with different amounts of feedback, including negative relevance feedback. Feedback is implemented using massive weighted query expansion. Parsimonious query expansion using Dirichlet smoothing

  13. The impact of positive, negative and topical relevance feedback

    NARCIS (Netherlands)

    Kaptein, R.; Kamps, J.; Hiemstra, D.; Voorhees, E.M.; Buckland, L.P.

    2009-01-01

    This document contains a description of experiments for the 2008 Relevance Feedback track. We experiment with different amounts of feedback, including negative relevance feedback. Feedback is implemented using massive weighted query expansion. Parsimonious query expansion using only relevant

  14. The impact of positive, negative and topical relevance feedback

    NARCIS (Netherlands)

    Kaptein, Rianne; Kamps, Jaap; Hiemstra, Djoerd

    2008-01-01

    This document contains a description of experiments for the 2008 Relevance Feedback track. We experiment with different amounts of feedback, including negative relevance feedback. Feedback is implemented using massive weighted query expansion. Parsimonious query expansion using only relevant

  15. Microphysics and Southern Ocean Cloud Feedback

    Science.gov (United States)

    McCoy, Daniel T.

    Global climate models (GCMs) change their cloud properties in the Southern Ocean (SO) with warming in a qualitatively consistent fashion. Cloud albedo increases in the mid-latitudes and cloud fraction decreases in the subtropics. This creates a distinctive 'dipole' structure in the SW cloud feedback. However, the shape of the dipole varies from model to model. In this thesis we discuss the microphysical mechanisms underlying the SW cloud feedback over the mid-latitude SO. We will focus on the negative lobe of the dipole. The negative SW cloud feedback in the mid-latitudes is created by transitions from ice to liquid in models. If ice transitions to liquid in mixed-phase clouds the cloud albedo increases because ice crystals are larger than liquid droplets and therefore more reflective for a constant mass of water. Decreases in precipitation efficiency further enhance this effect by decreasing sinks of cloud water. This transition is dependent on the mixed-phase cloud parameterization. Parameterizations vary wildly between models and GCMs disagree by up to 35 K on the temperature where ice and liquid are equally prevalent. This results in a wide spread in the model predictions of the increase in liquid water path (LWP, where the path is the vertically integrated mass of water) with warming that drives the negative optical depth cloud feedback. It is found that this disagreement also results in a wide array of climate mean-states as models that create liquid at lower temperatures have a higher mean-state LWP, lower ice water path (IWP), and higher condensed (ice and liquid) water path (CWP). This presents a problem in climate models. GCMs need to have a reasonable planetary albedo in their climate mean-state. We show evidence that GCMs have tuned cloud fraction to compensate for the variation in mid-latitude cloud albedo driven by the mixed-phase cloud parameterization. This tuning results in mid-latitude clouds that are both too few and too bright as well as a

  16. Titan Coupled Surface/Atmosphere Retrievals

    Science.gov (United States)

    West, R. A.; Pitman, K. M.

    2009-05-01

    Titan's thick haze obscures its surface at visible wavelengths and hinders surface photometric studies in the near-infrared. The large vertical extent of the haze produces two effects which require radiative transfer analysis beyond the capability of plane-parallel multi-scatter models. Haze aerosols extend to altitudes above 500 km and require a spherical-shell RT algorithm close to the limb or terminator. Even near nadir viewing, horizontal scattering at spatial scales less than a few hundred km requires a code capable of simulating the adjacency effect. The adjacency effect will reduce contrast more for small spatial scales than for large spatial scales, and the amount of contrast reduction depends on many factors (haze optical thickness, vertical distribution, single scattering albedo, scattering geometry, spatial scale). Titan's haze is strongly forward scattering even near 1-µm wavelength and many RT codes do a poor job. Fortunately the problem is more tractable at longer wavelengths. We show how data from the Cassini VIMS and ISS instruments can be used to understand surface contrast and atmospheric haze properties.

  17. Greenland ice sheet albedo feedback: thermodynamics and atmospheric drivers

    Directory of Open Access Journals (Sweden)

    J. E. Box

    2012-08-01

    Full Text Available Greenland ice sheet mass loss has accelerated in the past decade responding to combined glacier discharge and surface melt water runoff increases. During summer, absorbed solar energy, modulated at the surface primarily by albedo, is the dominant factor governing surface melt variability in the ablation area. Using satellite-derived surface albedo with calibrated regional climate modeled surface air temperature and surface downward solar irradiance, we determine the spatial dependence and quantitative impact of the ice sheet albedo feedback over 12 summer periods beginning in 2000. We find that, while albedo feedback defined by the change in net solar shortwave flux and temperature over time is positive over 97% of the ice sheet, when defined using paired annual anomalies, a second-order negative feedback is evident over 63% of the accumulation area. This negative feedback damps the accumulation area response to warming due to a positive correlation between snowfall and surface air temperature anomalies. Positive anomaly-gauged feedback concentrated in the ablation area accounts for more than half of the overall increase in melting when satellite-derived melt duration is used to define the timing when net shortwave flux is sunk into melting. Abnormally strong anticyclonic circulation, associated with a persistent summer North Atlantic Oscillation extreme since 2007, enabled three amplifying mechanisms to maximize the albedo feedback: (1 increased warm (south air advection along the western ice sheet increased surface sensible heating that in turn enhanced snow grain metamorphic rates, further reducing albedo; (2 increased surface downward shortwave flux, leading to more surface heating and further albedo reduction; and (3 reduced snowfall rates sustained low albedo, maximizing surface solar heating, progressively lowering albedo over multiple years. The summer net infrared and solar radiation for the high elevation accumulation area approached

  18. Sensory-Feedback Exoskeletal Arm Controller

    Science.gov (United States)

    An, Bin; Massie, Thomas H.; Vayner, Vladimir

    2004-01-01

    An electromechanical exoskeletal arm apparatus has been designed for use in controlling a remote robotic manipulator arm. The apparatus, called a force-feedback exoskeleton arm master (F-EAM) is comfortable to wear and easy to don and doff. It provides control signals from the wearer s arm to a robot arm or a computer simulator (e.g., a virtual-reality system); it also provides force and torque feedback from sensors on the robot arm or from the computer simulator to the wearer s arm. The F-EAM enables the wearer to make the robot arm gently touch objects and finely manipulate them without exerting excessive forces. The F-EAM features a lightweight design in which the motors and gear heads that generate force and torque feedback are made smaller than they ordinarily would be: this is achieved by driving the motors to power levels greater than would ordinarily be used in order to obtain higher torques, and by providing active liquid cooling of the motors to prevent overheating at the high drive levels. The F-EAM (see figure) includes an assembly that resembles a backpack and is worn like a backpack, plus an exoskeletal arm mechanism. The FEAM has five degrees of freedom (DOFs) that correspond to those of the human arm: 1. The first DOF is that of the side-to-side rotation of the upper arm about the shoulder (rotation about axis 1). The reflected torque for this DOF is provided by motor 1 via drum 1 and a planar four-bar linkage. 2. The second DOF is that of the up-and-down rotation of the arm about the shoulder. The reflected torque for this DOF is provided by motor 2 via drum 2. 3. The third DOF is that of twisting of the upper arm about its longitudinal axis. This DOF is implemented in a cable remote-center mechanism (CRCM). The reflected torque for this DOF is provided by motor 3, which drives the upper-arm cuff and the mechanism below it. A bladder inflatable by gas or liquid is placed between the cuff and the wearer s upper arm to compensate for misalignment

  19. Multisource feedback for radiation oncologists

    International Nuclear Information System (INIS)

    Vinod, Shalini K.; Lonergan, Denise M.

    2013-01-01

    Multisource feedback (MSF) is an assessment of performance through evaluation of an individual's competence from multiple perspectives. It is mandated in many specialist training schemes in medicine. The aim of this study was to test the feasibility of implementing MSF for consultant radiation oncologists. A validated tool consisting of a self-assessment questionnaire, medical colleague questionnaire, co-worker questionnaire and patient questionnaire was used for MSF. Statements were rated on a 5-point Likert scale with 1 being a low rating and 5 a high rating. Seven radiation oncologists volunteered to undergo MSF. They each nominated 10 medical colleagues, 10 co-workers and 10 patients to be surveyed. Clinician feedback was provided as an individual report with a mean score and range for each data item. Two hundred ten surveys were mailed out and seven self-assessments were completed. The response rate was 87% for medical colleagues, 89% for co-workers and 79% for patients. The mean feedback scores averaged for the radiation oncologists ranged from 4.4 to 4.9, significantly higher than self-assessments scores which ranged from 3.2 to 3.7. MSF identified areas for potential improvement including communication and collaboration with co-workers and accessibility to and adequacy of clinic space for patients. All radiation oncologists found the MSF a positive experience, and five planned to make changes in their practice in response to this. The high response rate to the surveys has shown that it is feasible to implement MSF for radiation oncologists. This could potentially be used as a method for ongoing revalidation.

  20. Wideband feedback system prototype validation

    CERN Document Server

    Li, K; Bjorsvik, E; Fox, J; Hofle, W; Kotzian, G; Rivetta, C; Salvant, B; Turgut, O

    2017-01-01

    A wideband feedback demonstrator system has been de-veloped in collaboration with US-LARP under the joint lead-ership of CERN and SLAC. The system includes widebandkicker structures and amplifiers along with a fast digital re-configurable system up to 4 GS/s for single bunch and multibunch control. Most of the components have been installedin recent years and have been put into operation to test bothintra-bunch damping and individual bunch control in a multibunch train. In this note we report on the MD program,procedure and key findings that were made with this systemin the past year.

  1. AGN feedback in galaxy formation

    CERN Document Server

    Antonuccio-Delogu, Vincenzo

    2010-01-01

    During the past decade, convincing evidence has been accumulated concerning the effect of active galactic nuclei (AGN) activity on the internal and external environment of their host galaxies. Featuring contributions from well-respected researchers in the field, and bringing together work by specialists in both galaxy formation and AGN, this volume addresses a number of key questions about AGN feedback in the context of galaxy formation. The topics covered include downsizing and star-formation time scales in massive elliptical galaxies, the connection between the epochs of supermassive black h

  2. Frequent feedback enhances complex motor skill learning.

    Science.gov (United States)

    Wulf, G; Shea, C H; Matschiner, S

    1998-06-01

    Feedback frequency effects on the learning of a complex motor skill, the production of slalom-type movements on a ski-simulator, were examined. In Experiment 1, a movement feature that characterizes expert performance was identified. Participants (N = 8) practiced the task for 6 days. Significant changes across practice were found for movement amplitude and relative force onset. Relative force onset is considered a measure of movement efficiency; relatively late force onsets characterize expert performance. In Experiment 2, different groups of participants (N = 27) were given concurrent feedback about force onset on either 100% or 50% of the practice trials; a control group was given no feedback. The following hypothesis was tested: Contrary to previous findings concerning relatively simple tasks, for the learning of a complex task such as the one used here, a high relative feedback frequency (100%) is more beneficial for learning than a reduced feedback frequency (50%). Participants practiced the task on 2 consecutive days and performed a retention test without feedback on Day 3. The 100% feedback group demonstrated later relative force onsets than the control group in retention; the 50% feedback group showed intermediate performance. The results provide support for the notion that high feedback frequencies are beneficial for the learning of complex motor skills, at least until a certain level of expertise is achieved. That finding suggests that there may be an interaction between task difficulty and feedback frequency similar to the interaction found in the summary-KR literature.

  3. PEER FEEDBACK ON LANGUAGE FORM IN TELECOLLABORATION

    Directory of Open Access Journals (Sweden)

    Paige Ware

    2008-02-01

    Full Text Available We performed a two-phase, year-long research project that explored the impact of peer feedback on language development. We investigated specifically how and when post-secondary learners of English and Spanish provide corrective feedback on their partners' use of the target language in weekly asynchronous discussions by assigning them to one of two conditions: e-tutoring, in which students were asked to provide peer feedback on any linguistic form they perceived as incorrect; and e-partnering, in which students were not required to provide peer feedback but could do so on their own initiative. We examined the frequency and type of language use by coding the feedback for language-related episodes (Swain & Lapkin, 1998 and for feedback strategies (Ros i Solé & Truman, 2005. The findings indicate that students in both conditions preferred an inclusion of feedback on form as part of their exchange, but such feedback only occurred when explicitly required in the e-tutoring condition. Pedagogical implications include the need to situate peer feedback on form within current models of telecollaboration and to assist students in using feedback strategies such as reformulations, which do not rely on a deep understanding of the target or native language grammar.

  4. EXACT SOLUTION TO FINITE TEMPERATURE SFDM: NATURAL CORES WITHOUT FEEDBACK

    International Nuclear Information System (INIS)

    Robles, Victor H.; Matos, T.

    2013-01-01

    Recent high-quality observations of low surface brightness (LSB) galaxies have shown that their dark matter (DM) halos prefer flat central density profiles. However, the standard cold dark matter model simulations predict a more cuspy behavior. One mechanism used to reconcile the simulations with the observed data is the feedback from star formation. While this mechanism may be successful in isolated dwarf galaxies, its success in LSB galaxies remains unclear. Additionally, the inclusion of too much feedback in the simulations is a double-edged sword—in order to obtain a cored DM distribution from an initially cuspy one, the feedback recipes usually require one to remove a large quantity of baryons from the center of the galaxies; however, some feedback recipes produce twice the number of satellite galaxies of a given luminosity and with much smaller mass-to-light ratios from those that are observed. Therefore, one DM profile that produces cores naturally and that does not require large amounts of feedback would be preferable. We find both requirements to be satisfied in the scalar field dark matter model. Here, we consider that DM is an auto-interacting real scalar field in a thermal bath at temperature T with an initial Z 2 symmetric potential. As the universe expands, the temperature drops so that the Z 2 symmetry is spontaneously broken and the field rolls down to a new minimum. We give an exact analytic solution to the Newtonian limit of this system, showing that it can satisfy the two desired requirements and that the rotation curve profile is no longer universal.

  5. Sensory feedback for upper limb prostheses.

    Science.gov (United States)

    Hsiao, Steven S; Fettiplace, Michael; Darbandi, Bejan

    2011-01-01

    In this chapter, we discuss the neurophysiological basis of how to provide sensory feedback to users with an upper limb prosthesis and discuss some of the theoretical issues that need to be considered when directly stimulating neurons in the somatosensory system. We focus on technologies that are currently available and discuss approaches that are most likely to succeed in providing natural perception from the artificial hand to the user. First, we discuss the advantages and disadvantages of providing feedback by stimulating directly the remaining afferents that originally innervated the arm and hand. In particular, we pay close attention to the normal functional roles that the peripheral afferents play in perception. What are the consequences and implications of stimulating these afferents? We then discuss whether it is reasonable to stimulate neurons in the ascending pathways that carry the information from the afferents to the cortex or directly in neurons in the primary somatosensory cortex. We show that for some modalities there are advantages for stimulating in the spinal cord, while for others it is advantageous to stimulate directly in the somatosensory cortex. Finally, we discuss results from a current experiment in which we used electrical stimuli in primary somatosensory cortex to restore the percept of the intensity of a mechanical probe indented into the hand. The results suggest that the simple percept of stimulus intensity can be provided to the animal from a single finger using four electrodes. We propose that significantly more electrodes will be needed to reproduce more complex aspects of tactile perception. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Sample-Clock Phase-Control Feedback

    Science.gov (United States)

    Quirk, Kevin J.; Gin, Jonathan W.; Nguyen, Danh H.; Nguyen, Huy

    2012-01-01

    To demodulate a communication signal, a receiver must recover and synchronize to the symbol timing of a received waveform. In a system that utilizes digital sampling, the fidelity of synchronization is limited by the time between the symbol boundary and closest sample time location. To reduce this error, one typically uses a sample clock in excess of the symbol rate in order to provide multiple samples per symbol, thereby lowering the error limit to a fraction of a symbol time. For systems with a large modulation bandwidth, the required sample clock rate is prohibitive due to current technological barriers and processing complexity. With precise control of the phase of the sample clock, one can sample the received signal at times arbitrarily close to the symbol boundary, thus obviating the need, from a synchronization perspective, for multiple samples per symbol. Sample-clock phase-control feedback was developed for use in the demodulation of an optical communication signal, where multi-GHz modulation bandwidths would require prohibitively large sample clock frequencies for rates in excess of the symbol rate. A custom mixedsignal (RF/digital) offset phase-locked loop circuit was developed to control the phase of the 6.4-GHz clock that samples the photon-counting detector output. The offset phase-locked loop is driven by a feedback mechanism that continuously corrects for variation in the symbol time due to motion between the transmitter and receiver as well as oscillator instability. This innovation will allow significant improvements in receiver throughput; for example, the throughput of a pulse-position modulation (PPM) with 16 slots can increase from 188 Mb/s to 1.5 Gb/s.

  7. Real-time calibration of a feedback trap

    OpenAIRE

    Gavrilov, Momčilo; Jun, Yonggun; Bechhoefer, John

    2014-01-01

    Feedback traps use closed-loop control to trap or manipulate small particles and molecules in solution. They have been applied to the measurement of physical and chemical properties of particles and to explore fundamental questions in the non-equilibrium statistical mechanics of small systems. These applications have been hampered by drifts in the electric forces used to manipulate the particles. Although the drifts are small for measurements on the order of seconds, they dominate on time sca...

  8. Real-time system for studies of the effects of acoustic feedback on animal vocalizations.

    Directory of Open Access Journals (Sweden)

    Mike eSkocik

    2013-01-01

    Full Text Available Studies of behavioral and neural responses to distorted auditory feedback can help shed light on the neural mechanisms of animal vocalizations. We describe an apparatus for generating real-time acoustic feedback. The system can very rapidly detect acoustic features in a song and output acoustic signals if the detected features match the desired acoustic template. The system uses spectrogram-based detection of acoustic elements. It is low-cost and can be programmed for a variety of behavioral experiments requiring acoustic feedback or neural stimulation. We use the system to study the effects of acoustic feedback on birds' vocalizations and demonstrate that such an acoustic feedback can cause both immediate and long-term changes to birds’ songs.

  9. Ultrasensitive Negative Feedback Control: A Natural Approach for the Design of Synthetic Controllers.

    Science.gov (United States)

    Montefusco, Francesco; Akman, Ozgur E; Soyer, Orkun S; Bates, Declan G

    2016-01-01

    Many of the most important potential applications of Synthetic Biology will require the ability to design and implement high performance feedback control systems that can accurately regulate the dynamics of multiple molecular species within the cell. Here, we argue that the use of design strategies based on combining ultrasensitive response dynamics with negative feedback represents a natural approach to this problem that fully exploits the strongly nonlinear nature of cellular information processing. We propose that such feedback mechanisms can explain the adaptive responses observed in one of the most widely studied biomolecular feedback systems-the yeast osmoregulatory response network. Based on our analysis of such system, we identify strong links with a well-known branch of mathematical systems theory from the field of Control Engineering, known as Sliding Mode Control. These insights allow us to develop design guidelines that can inform the construction of feedback controllers for synthetic biological systems.

  10. Language Trajectory through Corrective Feedback

    Directory of Open Access Journals (Sweden)

    S. Saber Alavi

    2016-08-01

    Full Text Available This quasi-experimental study was designed to investigate the effects of corrective feedback on SLA/EFL to determine the potential benefits of two different corrective feedback techniques, namely recasts and elicitation. The research hypotheses were: 1 Learners who are exposed to interactive focused task that requires CR will benefit more than those who are exposed to communicative activities only; 2 Elicitation will be more effective than recasts in leading to L2 development; Three intensive EFL classes in a language center in Songkhla province, Thailand were selected to participate in the study. Based on the study design, two class were assigned to the treatment conditions elicitation group and recasts group and the third was used as a control group. The treatment took place over a period of 9 meetings focusing on teaching third person singular –s morpheme and the provision of CF where it was necessary. The participants' knowledge of the intended syntantic point was tested before treatment and post tested after receiving the treatment. A multiple choice and focused-cloze reading grammar test was used in the pre-test and the post-test to evaluate the effects of the treatments on the learners' acquisition of third person singular morpheme. This classroom-based study showed that the two treatment groups benefited from CF strategies, but according to the study, elicitation group outperformed the recast one.

  11. Late Quaternary vegetation-climate feedbacks

    Directory of Open Access Journals (Sweden)

    M. Claussen*

    2009-06-01

    Full Text Available Feedbacks between vegetation and other components of the climate system are discussed with respect to their influence on climate dynamics during the late Quaternary, i.e., the last glacial-interglacial cycles. When weighting current understanding based on interpretation of palaeobotanic and palaeoclimatic evidence by numerical climate system models, a number of arguments speak in favour of vegetation dynamics being an amplifier of orbital forcing. (a The vegetation-snow albedo feedback in synergy with the sea-ice albedo feedback tends to amplify Northern Hemisphere and global mean temperature changes. (b Variations in the extent of the largest desert on Earth, the Sahara, appear to be amplified by biogeophysical feedback. (c Biogeochemical feedbacks in the climate system in relation to vegetation migration are supposed to be negative on time scales of glacial cycles. However, with respect to changes in global mean temperature, they are presumably weaker than the positive biogeophysical feedbacks.

  12. Reducing the uncertainty in subtropical cloud feedback

    Science.gov (United States)

    Myers, Timothy A.; Norris, Joel R.

    2016-03-01

    Large uncertainty remains on how subtropical clouds will respond to anthropogenic climate change and therefore whether they will act as a positive feedback that amplifies global warming or negative feedback that dampens global warming by altering Earth's energy budget. Here we reduce this uncertainty using an observationally constrained formulation of the response of subtropical clouds to greenhouse forcing. The observed interannual sensitivity of cloud solar reflection to varying meteorological conditions suggests that increasing sea surface temperature and atmospheric stability in the future climate will have largely canceling effects on subtropical cloudiness, overall leading to a weak positive shortwave cloud feedback (0.4 ± 0.9 W m-2 K-1). The uncertainty of this observationally based approximation of the cloud feedback is narrower than the intermodel spread of the feedback produced by climate models. Subtropical cloud changes will therefore complement positive cloud feedbacks identified by previous work, suggesting that future global cloud changes will amplify global warming.

  13. Differential effects of visual feedback on subjective visual vertical accuracy and precision.

    Directory of Open Access Journals (Sweden)

    Daniel Bjasch

    Full Text Available The brain constructs an internal estimate of the gravitational vertical by integrating multiple sensory signals. In darkness, systematic head-roll dependent errors in verticality estimates, as measured by the subjective visual vertical (SVV, occur. We hypothesized that visual feedback after each trial results in increased accuracy, as physiological adjustment errors (A-/E-effect are likely based on central computational mechanisms and investigated whether such improvements were related to adaptational shifts of perceived vertical or to a higher cognitive strategy. We asked 12 healthy human subjects to adjust a luminous arrow to vertical in various head-roll positions (0 to 120deg right-ear down, 15deg steps. After each adjustment visual feedback was provided (lights on, display of previous adjustment and of an earth-vertical cross. Control trials consisted of SVV adjustments without feedback. At head-roll angles with the largest A-effect (90, 105, and 120deg, errors were reduced significantly (p0.05 influenced. In seven subjects an additional session with two consecutive blocks (first with, then without visual feedback was completed at 90, 105 and 120deg head-roll. In these positions the error-reduction by the previous visual feedback block remained significant over the consecutive 18-24 min (post-feedback block, i.e., was still significantly (p<0.002 different from the control trials. Eleven out of 12 subjects reported having consciously added a bias to their perceived vertical based on visual feedback in order to minimize errors. We conclude that improvements of SVV accuracy by visual feedback, which remained effective after removal of feedback for ≥18 min, rather resulted from a cognitive strategy than by adapting the internal estimate of the gravitational vertical. The mechanisms behind the SVV therefore, remained stable, which is also supported by the fact that SVV precision - depending mostly on otolith input - was not affected by visual

  14. The role of feed-forward and feedback processes for closed-loop prosthesis control

    Directory of Open Access Journals (Sweden)

    Saunders Ian

    2011-10-01

    Full Text Available Abstract Background It is widely believed that both feed-forward and feed-back mechanisms are required for successful object manipulation. Open-loop upper-limb prosthesis wearers receive no tactile feedback, which may be the cause of their limited dexterity and compromised grip force control. In this paper we ask whether observed prosthesis control impairments are due to lack of feedback or due to inadequate feed-forward control. Methods Healthy subjects were fitted with a closed-loop robotic hand and instructed to grasp and lift objects of different weights as we recorded trajectories and force profiles. We conducted three experiments under different feed-forward and feed-back configurations to elucidate the role of tactile feedback (i in ideal conditions, (ii under sensory deprivation, and (iii under feed-forward uncertainty. Results (i We found that subjects formed economical grasps in ideal conditions. (ii To our surprise, this ability was preserved even when visual and tactile feedback were removed. (iii When we introduced uncertainty into the hand controller performance degraded significantly in the absence of either visual or tactile feedback. Greatest performance was achieved when both sources of feedback were present. Conclusions We have introduced a novel method to understand the cognitive processes underlying grasping and lifting. We have shown quantitatively that tactile feedback can significantly improve performance in the presence of feed-forward uncertainty. However, our results indicate that feed-forward and feed-back mechanisms serve complementary roles, suggesting that to improve on the state-of-the-art in prosthetic hands we must develop prostheses that empower users to correct for the inevitable uncertainty in their feed-forward control.

  15. Differential Effects of Visual Feedback on Subjective Visual Vertical Accuracy and Precision

    Science.gov (United States)

    Bjasch, Daniel; Bockisch, Christopher J.; Straumann, Dominik; Tarnutzer, Alexander A.

    2012-01-01

    The brain constructs an internal estimate of the gravitational vertical by integrating multiple sensory signals. In darkness, systematic head-roll dependent errors in verticality estimates, as measured by the subjective visual vertical (SVV), occur. We hypothesized that visual feedback after each trial results in increased accuracy, as physiological adjustment errors (A−/E-effect) are likely based on central computational mechanisms and investigated whether such improvements were related to adaptational shifts of perceived vertical or to a higher cognitive strategy. We asked 12 healthy human subjects to adjust a luminous arrow to vertical in various head-roll positions (0 to 120deg right-ear down, 15deg steps). After each adjustment visual feedback was provided (lights on, display of previous adjustment and of an earth-vertical cross). Control trials consisted of SVV adjustments without feedback. At head-roll angles with the largest A-effect (90, 105, and 120deg), errors were reduced significantly (p0.05) influenced. In seven subjects an additional session with two consecutive blocks (first with, then without visual feedback) was completed at 90, 105 and 120deg head-roll. In these positions the error-reduction by the previous visual feedback block remained significant over the consecutive 18–24 min (post-feedback block), i.e., was still significantly (p<0.002) different from the control trials. Eleven out of 12 subjects reported having consciously added a bias to their perceived vertical based on visual feedback in order to minimize errors. We conclude that improvements of SVV accuracy by visual feedback, which remained effective after removal of feedback for ≥18 min, rather resulted from a cognitive strategy than by adapting the internal estimate of the gravitational vertical. The mechanisms behind the SVV therefore, remained stable, which is also supported by the fact that SVV precision – depending mostly on otolith input - was not affected by visual

  16. Cross-Layer Adaptive Feedback Scheduling of Wireless Control Systems

    Directory of Open Access Journals (Sweden)

    Jinxiang Dong

    2008-07-01

    Full Text Available There is a trend towards using wireless technologies in networked control systems. However, the adverse properties of the radio channels make it difficult to design and implement control systems in wireless environments. To attack the uncertainty in available communication resources in wireless control systems closed over WLAN, a cross-layer adaptive feedback scheduling (CLAFS scheme is developed, which takes advantage of the co-design of control and wireless communications. By exploiting crosslayer design, CLAFS adjusts the sampling periods of control systems at the application layer based on information about deadline miss ratio and transmission rate from the physical layer. Within the framework of feedback scheduling, the control performance is maximized through controlling the deadline miss ratio. Key design parameters of the feedback scheduler are adapted to dynamic changes in the channel condition. An eventdriven invocation mechanism for the feedback scheduler is also developed. Simulation results show that the proposed approach is efficient in dealing with channel capacity variations and noise interference, thus providing an enabling technology for control over WLAN.

  17. Tactile feedback improves auditory spatial localization.

    Science.gov (United States)

    Gori, Monica; Vercillo, Tiziana; Sandini, Giulio; Burr, David

    2014-01-01

    Our recent studies suggest that congenitally blind adults have severely impaired thresholds in an auditory spatial bisection task, pointing to the importance of vision in constructing complex auditory spatial maps (Gori et al., 2014). To explore strategies that may improve the auditory spatial sense in visually impaired people, we investigated the impact of tactile feedback on spatial auditory localization in 48 blindfolded sighted subjects. We measured auditory spatial bisection thresholds before and after training, either with tactile feedback, verbal feedback, or no feedback. Audio thresholds were first measured with a spatial bisection task: subjects judged whether the second sound of a three sound sequence was spatially closer to the first or the third sound. The tactile feedback group underwent two audio-tactile feedback sessions of 100 trials, where each auditory trial was followed by the same spatial sequence played on the subject's forearm; auditory spatial bisection thresholds were evaluated after each session. In the verbal feedback condition, the positions of the sounds were verbally reported to the subject after each feedback trial. The no feedback group did the same sequence of trials, with no feedback. Performance improved significantly only after audio-tactile feedback. The results suggest that direct tactile feedback interacts with the auditory spatial localization system, possibly by a process of cross-sensory recalibration. Control tests with the subject rotated suggested that this effect occurs only when the tactile and acoustic sequences are spatially congruent. Our results suggest that the tactile system can be used to recalibrate the auditory sense of space. These results encourage the possibility of designing rehabilitation programs to help blind persons establish a robust auditory sense of space, through training with the tactile modality.

  18. Determinants of feedback retention in soccer players

    OpenAIRE

    Janu?rio, Nuno; Rosado, Ant?nio; Mesquita, Isabel; Gallego, Jos?; Aguilar-Parra, Jos? M.

    2016-01-01

    Abstract This study analyzed soccer players? retention of coaches? feedback during training sessions. We intended to determine if the retention of information was influenced by the athletes? personal characteristic (age, gender and the sports level), the quantity of information included in coach?s feedback (the number of ideas and redundancy), athletes? perception of the relevance of the feedback information and athletes? motivation as well as the attention level. The study that was conducted...

  19. Tactile feedback improves auditory spatial localization

    Directory of Open Access Journals (Sweden)

    Monica eGori

    2014-10-01

    Full Text Available Our recent studies suggest that congenitally blind adults have severely impaired thresholds in an auditory spatial-bisection task, pointing to the importance of vision in constructing complex auditory spatial maps (Gori et al., 2014. To explore strategies that may improve the auditory spatial sense in visually impaired people, we investigated the impact of tactile feedback on spatial auditory localization in 48 blindfolded sighted subjects. We measured auditory spatial bisection thresholds before and after training, either with tactile feedback, verbal feedback or no feedback. Audio thresholds were first measured with a spatial bisection task: subjects judged whether the second sound of a three sound sequence was spatially closer to the first or the third sound. The tactile-feedback group underwent two audio-tactile feedback sessions of 100 trials, where each auditory trial was followed by the same spatial sequence played on the subject’s forearm; auditory spatial bisection thresholds were evaluated after each session. In the verbal-feedback condition, the positions of the sounds were verbally reported to the subject after each feedback trial. The no-feedback group did the same sequence of trials, with no feedback. Performance improved significantly only after audio-tactile feedback. The results suggest that direct tactile feedback interacts with the auditory spatial localization system, possibly by a process of cross-sensory recalibration. Control tests with the subject rotated suggested that this effect occurs only when the tactile and acoustic sequences are spatially coherent. Our results suggest that the tactile system can be used to recalibrate the auditory sense of space. These results encourage the possibility of designing rehabilitation programs to help blind persons establish a robust auditory sense of space, through training with the tactile modality.

  20. Studies Of Positive-Position-Feedback Control

    Science.gov (United States)

    Fanson, James L.; Caughey, Thomas K.

    1992-01-01

    Report discusses theoretical and experimental studies of positive-position-feedback control for suppressing vibrations in large flexible structures. Positive-position-feedback control involves placement of actuators and sensors on structure; control voltages applied to actuators in response to outputs of sensors processed via compensator algorithm. Experiments demonstrate feasibility of suppressing vibrations by positive position feedback, and spillover of vibrational energy into uncontrolled modes has stabilizing effect if control gain sufficiently small.

  1. Feedback in the process of education

    OpenAIRE

    Babejová, Barbora

    2017-01-01

    The thesis Feedback in the proces of education, discusses formative feedback whose goal is to convey information to the student, which positively influences the students progress. Therefore it is an ongoing action of the teacher, who is monitoring the progress and results of the students, so that the teacher can help the students reach their goals and help form their overall personality. The first part of the thesis concentrates on the definition of feedback in the context of educational comm...

  2. Feedback in the Emergency Medicine Clerkship

    OpenAIRE

    Bernard, Aaron W; Kman, Nicholas E; Khandelwal, Sorabh

    2011-01-01

    Objective Feedback is a technique used in medical education to help develop and improve clinical skills. A comprehensive review article specifically intended for the emergency medicine (EM) educator is lacking, and it is the intent of this article to provide the reader with an in-depth, up-to-date, and evidence-based review of feedback in the context of the EM clerkship. Methods The review article is organized in a progressive manner, beginning with the definition of feedback, the importance ...

  3. Feedback in the Emergency Medicine Clerkships

    OpenAIRE

    Sorabh Khandelwal; Nicholas E Kman; Aaron W Bernard

    2011-01-01

    Objective: Feedback is a technique used in medical education to help develop and improve clinical skills. A comprehensive review article specifically intended for the emergency medicine (EM) educator is lacking, and it is the intent of this article to provide the reader with an in-depth, up-to-date, and evidence-based review of feedback in the context of the EM clerkship. Methods: The review article is organized in a progressive manner, beginning with the definition of feedback, the importanc...

  4. Corrective feedback, learner uptake, and feedback perception in a Chinese as a foreign language classroom

    Directory of Open Access Journals (Sweden)

    Tingfeng Fu

    2016-03-01

    Full Text Available The role of corrective feedback in second language classrooms has received considerable research attention in the past few decades. However, most of this research has been conducted in English-teaching settings, either ESL or EFL. This study examined teacher feedback, learner uptake as well as learner and teacher perception of feedback in an adult Chinese as a foreign language classroom. Ten hours of classroom interactions were videotaped, transcribed and coded for analysis. Lyster and Ranta’s (1997 coding system involving six types of feedback was initially used to identify feedback frequency and learner uptake. However, the teacher was found to use a number of additional feedback types. Altogether, 12 types of feedback were identified: recasts, delayed recasts, clarification requests, translation, metalinguistic feedback, elicitation, explicit correction, asking a direct question, repetition, directing question to other students, re-asks, and using L1-English. Differences were noted in the frequency of some of the feedback types as well as learner uptake compared to what had been reported in some previous ESL and EFL studies. With respect to the new feedback types, some led to noticeable uptake. As for the students’ and teacher’s perceptions, they did not match and both the teacher and the students were generally not accurate in perceiving the frequency of each feedback type. The findings are discussed in terms of the role of context in affecting the provision and effectiveness of feedback and its relationship to student and teacher perception of feedback.

  5. Software Development and Feedback from Usability Evaluations

    DEFF Research Database (Denmark)

    Høegh, Rune Thaarup

    2008-01-01

    This paper presents a study of the strengths and weaknesses of written, multimedia and oral feedback from usability evaluations to developers. The strengths and weaknesses are related to how well the feedback supports the developers in addressing usability problems in a software system. The study...... of information, while still not offering the required information to address usability problems. Other forms of feedback, such as oral or multimedia feedback helps the developer in understanding the usability problems better, but are on the other hand less cost-effective than a written description....

  6. Opportunistic Relay Selection With Limited Feedback

    KAUST Repository

    Eltayeb, Mohammed E.

    2015-08-01

    Relay selection is a simple technique that achieves spatial diversity in cooperative relay networks. Generally, relay selection algorithms require channel state information (CSI) feedback from all cooperating relays to make a selection decision. This requirement poses two important challenges, which are often neglected in the literature. Firstly, the fed back channel information is usually corrupted by additive noise. Secondly, CSI feedback generates a great deal of feedback overhead (air-time) that could result in significant performance hits. In this paper, we propose a compressive sensing (CS) based relay selection algorithm that reduces the feedback overhead of relay networks under the assumption of noisy feedback channels. The proposed algorithm exploits CS to first obtain the identity of a set of relays with favorable channel conditions. Following that, the CSI of the identified relays is estimated using least squares estimation without any additional feedback. Both single and multiple relay selection cases are considered. After deriving closed-form expressions for the asymptotic end-to-end SNR at the destination and the feedback load for different relaying protocols, we show that CS-based selection drastically reduces the feedback load and achieves a rate close to that obtained by selection algorithms with dedicated error-free feedback. © 1972-2012 IEEE.

  7. Raman fiber distributed feedback lasers.

    Science.gov (United States)

    Westbrook, Paul S; Abedin, Kazi S; Nicholson, Jeffrey W; Kremp, Tristan; Porque, Jerome

    2011-08-01

    We demonstrate fiber distributed feedback (DFB) lasers using Raman gain in two germanosilicate fibers. Our DFB cavities were 124 mm uniform fiber Bragg gratings with a π phase shift offset from the grating center. Our pump was at 1480 nm and the DFB lasers operated on a single longitudinal mode near 1584 nm. In a commercial Raman gain fiber, the maximum output power, linewidth, and threshold were 150 mW, 7.5 MHz, and 39 W, respectively. In a commercial highly nonlinear fiber, these figures improved to 350 mW, 4 MHz, and 4.3 W, respectively. In both lasers, more than 75% of pump power was transmitted, allowing for the possibility of substantial amplification in subsequent Raman gain fiber. © 2011 Optical Society of America

  8. Tubuloglomerular feedback in Dahl rats

    DEFF Research Database (Denmark)

    Karlsen, F M; Leyssac, P P; Holstein-Rathlou, N H

    1998-01-01

    We have previously demonstrated a loss of autoregulation in Dahl salt-sensitive (Dahl-S) rats rendered hypertensive on a high-salt diet. To determine whether this was due to a decreased activity of either the myogenic or the tubuloglomerular feedback (TGF) response, we tested the TGF response...... in both Dahl-S and salt-resistant Dahl rats on high- and low-salt diets. TGF was investigated in the closed-loop mode with a videometric technique, in which the response in late proximal flow rate to perturbations in Henle flow rate was measured. All Dahl rats showed a similar compensatory response...... to perturbations around the natural operating point, with a TGF response that was more efficient than in normotensive Sprague-Dawley rats. No evidence of decreased TGF responsiveness in hypertensive Dahl-S rats was found. The results suggest that the loss of autoregulation in hypertensive Dahl-S rats is due...

  9. Social is special: A normative framework for teaching with and learning from evaluative feedback.

    Science.gov (United States)

    Ho, Mark K; MacGlashan, James; Littman, Michael L; Cushman, Fiery

    2017-10-01

    Humans often attempt to influence one another's behavior using rewards and punishments. How does this work? Psychologists have often assumed that "evaluative feedback" influences behavior via standard learning mechanisms that learn from environmental contingencies. On this view, teaching with evaluative feedback involves leveraging learning systems designed to maximize an organism's positive outcomes. Yet, despite its parsimony, programs of research predicated on this assumption, such as ones in developmental psychology, animal behavior, and human-robot interaction, have had limited success. We offer an explanation by analyzing the logic of evaluative feedback and show that specialized learning mechanisms are uniquely favored in the case of evaluative feedback from a social partner. Specifically, evaluative feedback works best when it is treated as communicating information about the value of an action rather than as a form of reward to be maximized. This account suggests that human learning from evaluative feedback depends on inferences about communicative intent, goals and other mental states-much like learning from other sources, such as demonstration, observation and instruction. Because these abilities are especially developed in humans, the present account also explains why evaluative feedback is far more widespread in humans than non-human animals. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. The combination of positive and negative feedback loops confers exquisite flexibility to biochemical switches

    International Nuclear Information System (INIS)

    Pfeuty, Benjamin; Kaneko, Kunihiko

    2009-01-01

    A wide range of cellular processes require molecular regulatory pathways to convert a graded signal into a discrete response. One prevalent switching mechanism relies on the coexistence of two stable states (bistability) caused by positive feedback regulations. Intriguingly, positive feedback is often supplemented with negative feedback, raising the question of whether and how these two types of feedback can cooperate to control discrete cellular responses. To address this issue, we formulate a canonical model of a protein–protein interaction network and analyze the dynamics of a prototypical two-component circuit. The appropriate combination of negative and positive feedback loops can bring a bistable circuit close to the oscillatory regime. Notably, sharply activated negative feedback can give rise to a bistable regime wherein two stable fixed points coexist and may collide pairwise with two saddle points. This specific type of bistability is found to allow for separate and flexible control of switch-on and switch-off events, for example (i) to combine fast and reversible transitions, (ii) to enable transient switching responses and (iii) to display tunable noise-induced transition rates. Finally, we discuss the relevance of such bistable switching behavior, and the circuit topologies considered, to specific biological processes such as adaptive metabolic responses, stochastic fate decisions and cell-cycle transitions. Taken together, our results suggest an efficient mechanism by which positive and negative feedback loops cooperate to drive the flexible and multifaceted switching behaviors arising in biological systems

  11. How does feedback and peer feedback affect collaborative writing in a virtual learning environment?

    NARCIS (Netherlands)

    Guasch, Teresa; Espasa, Anna; Alvarez, Ibis; Kirschner, Paul A.

    2011-01-01

    Guasch, T., Espasa, A., Alvarez, I., & Kirschner, P. A. (2011, 31 May). How does feedback and peer feedback affect collaborative writing in a virtual learning environment? Presentation at a Learning & Cognition meeting, Open Universiteit in the Netherlands, Heerlen, The Netherlands.

  12. Plant-driven selection of microbes in the rhizosphere and plant-microbe feedbacks

    Directory of Open Access Journals (Sweden)

    Adil ESSARIOUI

    2017-09-01

    Full Text Available Plant impacts on soil microbial communities and plant-microbe feedbacks have become the focus of much research. Recent advances in plant-microbe interactions investigations show that plants are able to shape their rhizosphere microbiome through diverse mechanisms. In this review, we gather findings from across multiple studies on the role of plants in altering the structure and functions of microbes in the rhizosphere. In addition, we discuss the roles of diverse phytochemicals in mediating these effects. Finally, we highlight that selective enrichment of specific microorganisms in the rhizosphere has either negative feedbacks, with pathogen accumulation in the rhizosphere; or, perhaps most importantly, positive feedbacks as a result of the recruitment of a beneficial microflora. Insights into the mechanisms that underpin plant selection of microbial communities with positive feedbacks will provide new opportunities to increase crop production.

  13. Structural basis for feedback inhibition of the deoxyribonucleoside salvage pathway: Studies of the Drosophila deoxyribonucleoside kinase

    DEFF Research Database (Denmark)

    Mikkelsen, N.E.; Johansson, K.; Karlsson, A.

    2003-01-01

    Deoxyribonucleoside kinases are feedback inhibited by the final products of the salvage pathway, the deoxyribonucleoside triphosphates. In the present study, the mechanism of feedback inhibition is presented based on the crystal structure of a complex between the fruit fly deoxyribonucleoside...... kinase and its feedback inhibitor deoxythymidine triphosphate. The inhibitor was found to be bound as a bisubstrate inhibitor with its nucleoside part in the nucleoside binding site and with its phosphate groups partially occupying the phosphate donor site. The overall structure of the enzyme...... and to the primary base, Glu52, that normally is positioned close to the 5'-OH of the substrate deoxyribose....

  14. ERK1/2 can feedback-regulate cellular MEK1/2 levels

    OpenAIRE

    Hong, Seung-Keun; Wu, Pui-Kei; Karkhanis, Mansi; Park, Jong-In

    2015-01-01

    Signal transduction of the Raf/MEK/ERK pathway is regulated by various feedback mechanisms. Given the greater molar ratio between Raf-MEK than between MEK-ERK in cells, it may be possible that MEK1/2 levels are regulated to modulate Raf/MEK/ERK activity upon pathway stimulation. Nevertheless, it has not been reported whether MEK1/2 expression can be subject to a feedback regulation. Here, we report that the Raf/MEK/ERK pathway can feedback-regulate cellular MEK1 and MEK2 levels. In different ...

  15. Biased Reasoning : Adaptive Responses to Health Risk Feedback

    OpenAIRE

    Renner, Britta

    2004-01-01

    The present study examined reactions toward repeated self relevant feedback. Participants in a community health screening received feedback about their cholesterol level on two separate occasions. Reactions to the first feedback were examined with regard to feedback valence and expectedness. The findings showed that negative feedback was devalued, but only when it was unexpected. Feedback consistency war incorporated into analyses of the second feedback. Again, results showed that negative fe...

  16. Mechanical feedback in the molecular ISM of luminous IR galaxies

    NARCIS (Netherlands)

    Loenen, A. F.; Spaans, M.; Baan, W. A.; Meijerink, R.

    Aims. Molecular emission lines originating in the nuclei of luminous infra-red galaxies are used to determine the physical properties of the nuclear ISM in these systems. Methods. A large observational database of molecular emission lines is compared with model predictions that include heating by UV

  17. Effective feedback mechanism in the transfer and adoption of fish ...

    African Journals Online (AJOL)

    Journal of Agriculture and Social Research (JASR). Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 14, No 1 (2014) >. Log in or Register to get access to full text downloads.

  18. Buyer feedback as a filtering mechanism for reputable sellers

    Czech Academy of Sciences Publication Activity Database

    Laureti, P.; Slanina, František; Yu, Y.K.; Zhang, Y.

    2002-01-01

    Roč. 316, - (2002), s. 413-429 ISSN 0378-4371 R&D Projects: GA ČR GA202/01/1091 Institutional research plan: CEZ:AV0Z1010914 Keywords : asymetric information * internet commerce * Game theory * self-organization * symbiosis Subject RIV: BE - Theoretical Physics Impact factor: 1.369, year: 2002

  19. effective feedback mechanism in the transfer and adoption of fish ...

    African Journals Online (AJOL)

    Percentages, means and frequency count were used to analyse the data collected from the ... (2008), quoting Amiengheme (2005) enumerated the importance of fish in human diet to include;. 1. Food fish has a ... It decreases the risk of bowel cancer; and reduces insulin resistance in skeletal muscles. Fish is often regarded ...

  20. Athermalization of resonant optical devices via thermo-mechanical feedback

    Science.gov (United States)

    Rakich, Peter; Nielson, Gregory N.; Lentine, Anthony L.

    2016-01-19

    A passively athermal photonic system including a photonic circuit having a substrate and an optical cavity defined on the substrate, and passive temperature-responsive provisions for inducing strain in the optical cavity of the photonic circuit to compensate for a thermo-optic effect resulting from a temperature change in the optical cavity of the photonic circuit. Also disclosed is a method of passively compensating for a temperature dependent thermo-optic effect resulting on an optical cavity of a photonic circuit including the step of passively inducing strain in the optical cavity as a function of a temperature change of the optical cavity thereby producing an elasto-optic effect in the optical cavity to compensate for the thermo-optic effect resulting on an optical cavity due to the temperature change.

  1. Variables that affect the process and outcome of feedback, relevant for medical training : A meta-review

    NARCIS (Netherlands)

    van de Ridder, J. M Monica; Mcgaghie, William C.; Stokking, Karel M.; ten Cate, Olle T J

    2015-01-01

    Context: Feedback is considered important in medical education. The literature is not clear about the mechanisms that contribute to its effects, which are often small to moderate and at times contradictory. A variety of variables seem to influence the impact of feedback on learning. The aim of this

  2. Variables that affect the process and outcome of feedback, relevant for medical training : a meta-review

    NARCIS (Netherlands)

    van de Ridder, J.M.M.; McGaghie, W.C.; Stokking, K.M.; ten Cate, TJ

    2015-01-01

    Context Feedback is considered important in medical education. The literature is not clear about the mechanisms that contribute to its effects, which are often small to moderate and at times contradictory. A variety of variables seem to influence the impact of feedback on learning. The aim of this

  3. Influence of feedback characteristics on perceived learning value of feedback in clerkships : does culture matter?

    NARCIS (Netherlands)

    Suhoyo, Yoyo; Van Hell, Elisabeth A.; Kerdijk, Wouter; Emilia, Ova; Schonrock-Adema, Johanna; Kuks, Jan B. M.; Cohen-Schotanus, Janke

    2017-01-01

    Background: Various feedback characteristics have been suggested to positively influence student learning. It is not clear how these feedback characteristics contribute to students' perceived learning value of feedback in cultures classified low on the cultural dimension of individualism and high on

  4. Feedback Perceptions and Attribution by Secretarial Employees: Effects of Feedback-Content and Sender Characteristics

    Science.gov (United States)

    Raemdonck, Isabel; Strijbos, Jan-Willem

    2013-01-01

    Purpose: Theoretical explanations for the diverse reactive feedback from secretarial employees in different career phases are relatively unexplored. However, research examining age differences in the impact of feedback suggests that the effects of performance feedback may differ for employees in the early career phase and employees in the late…

  5. Relative Effects of Daily Feedback and Weekly Feedback on Customer Service Behavior at a Gas Station

    Science.gov (United States)

    So, Yongjoon; Lee, Kyehoon; Oah, Shezeen

    2013-01-01

    The relative effects of daily and weekly feedback on customer service behavior at a gas station were assessed using an ABC within-subjects design. Four critical service behaviors were identified and measured daily. After baseline (A), weekly feedback (B) was introduced, and daily feedback (C) was introduced in the next phase. The results indicated…

  6. Corrective Feedback, Learner Uptake, and Feedback Perception in a Chinese as a Foreign Language Classroom

    Science.gov (United States)

    Fu, Tingfeng; Nassaji, Hossein

    2016-01-01

    The role of corrective feedback in second language classrooms has received considerable research attention in the past few decades. However, most of this research has been conducted in English-teaching settings, either ESL or EFL. This study examined teacher feedback, learner uptake as well as learner and teacher perception of feedback in an adult…

  7. Teacher feedback in the classroom. Analyzing and developing teachers' feedback behavior in secondary education

    NARCIS (Netherlands)

    Voerman, A.

    2014-01-01

    Providing feedback is one of the most influential means of teachers to enhance student learning. In this dissertation, we first focused on what is known from research about effective (i.e. learning-enhancing) feedback. Effective feedback, mostly studied from a cognitive psychologist point of view,

  8. Medical Student Perceptions of Feedback and Feedback Behaviors Within the Context of the "Educational Alliance".

    Science.gov (United States)

    Bowen, Lucy; Marshall, Michelle; Murdoch-Eaton, Deborah

    2017-09-01

    Using the "educational alliance" as a conceptual framework, the authors explored medical students' beliefs about feedback and how their feedback behaviors reflect their perceptions. Five focus groups (four to six medical students each) at one UK medical school in 2015 were used to capture and elucidate learners' feedback perceptions and behaviors within the context of the learner-educator relationship. A map of key feedback opportunities across the program was used as a tool for exploring student engagement with the feedback process. Qualitative data were analyzed using an approach based on grounded theory principles. Three learner feedback behaviors emerged: recognizing, using, and seeking feedback. Five core themes influencing these behaviors were generated: learner beliefs, attitudes, and perceptions; relationships; teacher attributes; mode of feedback; and learning culture. Conceptual models illustrating the relationships between the themes and each behavior were developed. Learning culture influenced all three behaviors with a wide context of influences. Ensuring that feedback leads to improved performance requires more than training educators in best practices. The conceptual models support the educational alliance framework and illustrate the context and complexity of learning culture surrounding the educational relationship, learner, and feedback exchange. The educational alliance approach is underpinned by a mutual understanding of purpose and responsibility. Enhancing learners' feedback literacy skills seems to be the key aspect of the educational alliance in need of attention. Empowering learners to recognize, seek, and use feedback received within diverse learning cultures is essential.

  9. Can performance feedback during instruction boost knowledge acquisition? Contrasting criterion-based and social comparison feedback

    NARCIS (Netherlands)

    Kolloffel, Bas Jan; de Jong, Anthonius J.M.

    2016-01-01

    Feedback indicating how well students are performing during a learning task can be very stimulating. In this study with a pre- and post-test design, the effects of two types of performance feedback on learning results were compared: feedback during a learning task was either stated in terms of how

  10. The Impact of Middle-School Students' Feedback Choices and Performance on Their Feedback Memory

    Science.gov (United States)

    Cutumisu, Maria; Schwartz, Daniel L.

    2016-01-01

    This paper presents a novel examination of the impact of students' feedback choices and performance on their feedback memory. An empirical study was designed to collect the choices to seek critical feedback from a hundred and six Grade 8 middle-school students via Posterlet, a digital assessment game in which students design posters. Upon…

  11. Can Performance Feedback during Instruction Boost Knowledge Acquisition? Contrasting Criterion-Based and Social Comparison Feedback

    Science.gov (United States)

    Kollöffel, Bas; de Jong, Ton

    2016-01-01

    Feedback indicating how well students are performing during a learning task can be very stimulating. In this study with a pre- and post-test design, the effects of two types of performance feedback on learning results were compared: feedback during a learning task was either stated in terms of how well the students were performing relative to…

  12. Using Feedback to Promote Physical Activity: The Role of the Feedback Sign.

    Science.gov (United States)

    Kramer, Jan-Niklas; Kowatsch, Tobias

    2017-06-02

    Providing feedback is a technique to promote health behavior that is emphasized by behavior change theories. However, these theories make contradicting predictions regarding the effect of the feedback sign-that is, whether the feedback signals success or failure. Thus, it is unclear whether positive or negative feedback leads to more favorable behavior change in a health behavior intervention. The aim of this study was to examine the effect of the feedback sign in a health behavior change intervention. Data from participants (N=1623) of a 6-month physical activity intervention was used. Participants received a feedback email at the beginning of each month. Feedback was either positive or negative depending on the participants' physical activity in the previous month. In an exploratory analysis, change in monthly step count averages was used to evaluate the feedback effect. The feedback sign did not predict the change in monthly step count averages over the course of the intervention (b=-84.28, P=.28). Descriptive differences between positive and negative feedback can be explained by regression to the mean. The feedback sign might not influence the effect of monthly feedback emails sent out to participants of a large-scale physical activity intervention. However, randomized studies are needed to further support this conclusion. Limitations as well as opportunities for future research are discussed. ©Jan-Niklas Kramer, Tobias Kowatsch. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 02.06.2017.

  13. Pathology Resident Perspectives on Feedback and a Proposed Trainee Curriculum on Giving Feedback.

    Science.gov (United States)

    Prayson, Richard A; Rowe, J Jordi

    2016-11-01

    Receiving and reflecting on feedback is a critical skill in medicine. Learning how to provide effective feedback is important in assessment and engendering performance improvement. We outline a curriculum for laboratory medicine trainees on providing effective feedback. A group of trainees (26/30 attendees) was surveyed regarding their perspectives on effective feedback and impressions of an educational session focused on how to give effective feedback. The curriculum involved a 1-hour session focused on how to provide useful feedback. The two presenters used role-plays, group discussion, and didactic talk to present the material. Most attendees (n = 22/26) indicated that regular or frequent effective feedback was important to their learning. When asked, "What makes feedback effective for you?" the most frequent responses were being specific (n = 11) and being balanced (ie, presenting both positives and negative) (n = 10). On a Likert scale (1 = poor; 7 = excellent), attendees rated their ability to give feedback higher after the session (mean, 5.2) vs before the session (mean, 3.8). Feedback is an important component of assessment and reflective practice. Pathology trainees believe that being specific and balanced were characteristics of effective feedback. It is important to provide training on giving effective feedback to pathology trainees. © American Society for Clinical Pathology, 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

  14. The influence of force feedback and visual feedback in grasping tissue laparoscopically

    NARCIS (Netherlands)

    Heijnsdijk, E. A. M.; Pasdeloup, A.; van der Pijl, A. J.; Dankelman, J.; Gouma, D. J.

    2004-01-01

    Background: Due to the limited force feedback provided by laparoscopic instruments, surgeons may have difficulty in applying the appropriate force on the tissue. The aim of this study was to determine the influence of force feedback and visual feedback on the exerted pinch force. Methods: A grasper

  15. Projected Regime Shift in Arctic Cloud and Water Vapor Feedbacks

    Science.gov (United States)

    Chen, Yonghua; Miller, James R.; Francis, Jennifer; Russel, Gary L.

    2011-01-01

    The Arctic climate is changing faster than any other large-scale region on Earth. A variety of positive feedback mechanisms are responsible for the amplification, most of which are linked with changes in snow and ice cover, surface temperature (T(sub s)), atmospheric water vapor (WV), and cloud properties. As greenhouse gases continue to accumulate in the atmosphere, air temperature and water vapor content also increase, leading to a warmer surface and ice loss, which further enhance evaporation and WV. Many details of these interrelated feedbacks are poorly understood, yet are essential for understanding the pace and regional variations in future Arctic change. We use a global climate model (Goddard Institute for Space Studies, Atmosphere-Ocean Model) to examine several components of these feedbacks, how they vary by season, and how they are projected to change through the 21st century. One positive feedback begins with an increase in T(sub s) that produces an increase in WV, which in turn increases the downward longwave flux (DLF) and T(sub s), leading to further evaporation. Another associates the expected increases in cloud cover and optical thickness with increasing DLF and T(sub s). We examine the sensitivities between DLF and other climate variables in these feedbacks and find that they are strongest in the non-summer seasons, leading to the largest amplification in Ts during these months. Later in the 21st century, however, DLF becomes less sensitive to changes in WV and cloud optical thickness, as they cause the atmosphere to emit longwave radiation more nearly as a black body. This regime shift in sensitivity implies that the amplified pace of Arctic change relative to the northern hemisphere could relax in the future.

  16. Dissecting Solidago canadensis-soil feedback in its real invasion.

    Science.gov (United States)

    Dong, Li-Jia; Yang, Jian-Xia; Yu, Hong-Wei; He, Wei-Ming

    2017-04-01

    The importance of plant-soil feedback (PSF) has long been recognized, but the current knowledge on PSF patterns and the related mechanisms mainly stems from laboratory experiments. We aimed at addressing PSF effects on community performance and their determinants using an invasive forb Solidago canadensis . To do so, we surveyed 81 pairs of invaded versus uninvaded plots, collected soil samples from these pairwise plots, and performed an experiment with microcosm plant communities. The magnitudes of conditioning soil abiotic properties and soil biotic properties by S. canadensis were similar, but the direction was opposite; altered abiotic and biotic properties influenced the production of subsequent S. canadensis communities and its abundance similarly. These processes shaped neutral S. canadensis -soil feedback effects at the community level. Additionally, the relative dominance of S. canadensis increased with its ability of competitive suppression in the absence and presence of S. canadensis -soil feedbacks, and S. canadensis -induced decreases in native plant species did not alter soil properties directly. These findings provide a basis for understanding PSF effects and the related mechanisms in the field conditions and also highlight the importance of considering PSFs holistically.

  17. Conceptualizing Feedback Literacy: Knowing, Being, and Acting

    Science.gov (United States)

    Sutton, Paul

    2012-01-01

    In this paper I seek to reflect upon the process of becoming feedback literate. Feedback literacy is conceptualised as an integral component of a broader academic literacy that has three interrelated dimensions: the epistemological, the ontological and the practical. Learners experience and respond differentially to each of these dimensions which…

  18. Incident Management Organization succession planning stakeholder feedback

    Science.gov (United States)

    Anne E. Black

    2013-01-01

    This report presents complete results of a 2011 stakeholder feedback effort conducted for the National Wildfire Coordination Group (NWCG) Executive Board concerning how best to organize and manage national wildland fire Incident Management Teams in the future to meet the needs of the public, agencies, fire service and Team members. Feedback was collected from 858...

  19. Does Automated Feedback Improve Writing Quality?

    Science.gov (United States)

    Wilson, Joshua; Olinghouse, Natalie G.; Andrada, Gilbert N.

    2014-01-01

    The current study examines data from students in grades 4-8 who participated in a statewide computer-based benchmark writing assessment that featured automated essay scoring and automated feedback. We examined whether the use of automated feedback was associated with gains in writing quality across revisions to an essay, and with transfer effects…

  20. INDIRECT WRITTEN CORRECTIVE FEEDBACK, REVISION, AND LEARNING

    Directory of Open Access Journals (Sweden)

    Fatemeh Poorebrahim

    2017-01-01

    Full Text Available Corrective feedback, the necessity of providing it, and how it should be provided has been one of the hot topics in the area of ELT. Amid continuing controversies over whether providing feedback helps L2 learners improve their writing accuracy, many research studies have been undertaken to compare the relative effectiveness of different types of feedback. However, the difference between two types of indirect corrective feedback, namely indication and indication plus location, have not been properly examined yet. Motivated to narrow this gap, this study is designed to compare two groups of Iranian learners, each revising their papers based on one of the aforementioned options. For data analysis, a series of independent samples t tests were employed. The results revealed that the difference between the two groups in their reduction of errors from the original draft to the revision of each task followed a growing trend and became significant. Nonetheless, the difference in accuracy of new pieces of writing fell short of significance. Finally, it was found that error reduction in revision stage cannot be considered as learning. The results of the study, discussed in relation to that of others, implicate that the purpose for which feedback is provided is essential in determining the type of feedback; more explicit feedback is better for revising purposes while more implicit feedback is good for learning purposes.

  1. Audiotape Feedback for Essays in Distance Education

    NARCIS (Netherlands)

    Kirschner, P.A.; Brink, H. van den; Meester, M.

    1991-01-01

    Students who were required to write three short essays for a university level course on photochemistry at the Open university of the Netherlands received either audio-cassette or written feedback on their essays. The students receiving the audio feedback described their experience as personal,

  2. Stabilization using both noisy and noiseless feedback

    OpenAIRE

    Sahai, Anant

    2006-01-01

    When designing a distributed control system, the system designer has a choice in how to connect the different units through communication channels. In practice, noiseless and noisy channels may coexist. Using the standard toy example of scalar stabilization, this paper shows how a small amount of noiseless feedback can perform a ``supervisory'' role and thereby boost the effectiveness of noisy feedback.

  3. English Learners Perception on Lecturers’ Corrective Feedback

    Directory of Open Access Journals (Sweden)

    Titien Fatmawaty Mohammad

    2016-04-01

    Full Text Available The importance of written corrective feedback (CF has been an issue of substantial debate in the literature and this controversial issue has led to a development in latest studies to draw on foreign language acquisition (FLA research as a way to further comprehend the complexities of this issue particularly how students and teachers perceive the effectiveness of written corrective feedback. This research has largely focused on students’ perception on Lecturers’ corrective feedback, perceives the usefulness of different types of corrective feedback and the reasons they have for their preferences. Qualitative data was collected from 40 EFL students in 6th semester, by means of written questionnaires, interview and observation. Four feedback strategies were employed in this research and ranked each statement by using five-point Likert scale. Findings showed that almost all students 81.43 % want correction or feedback from lecturers for the mistakes on their writing. For the type of written corrective feedback, students prefer lecturers mark their mistakes and give comment on their work with the percentage as follows: 93% students found that giving clues or comment about how to fix errors can improve their writing ability, 76.69% of the students found that error identification is the most useful type of feedback, and 57.50% of students have a positive opinion for the provision of correction which is accompanied by comment. Those percentages of students perspective is supported by students’ explanation in an open ended question of questionnaire. Pedagogical implications of the study are also discussed.

  4. Feedback analysis of transimpedance operational amplifier circuits

    DEFF Research Database (Denmark)

    Bruun, Erik

    1993-01-01

    The transimpedance or current feedback operational amplifier (CFB op-amp) is reviewed and compared to a conventional voltage mode op-amp using an analysis emphasizing the basic feedback characteristics of the circuit. With this approach the paradox of the constant bandwidth obtained from CFB op...

  5. Exploring Student Perceptions of Verbal Feedback

    Science.gov (United States)

    Kerr, Katie

    2017-01-01

    This multiple case study was used to explore students' perceptions of what constitutes verbal feedback and what impacts their receipt and use of feedback. Interpretivist research was undertaken in a rural mixed secondary school in Cornwall, UK involving four year nine students (aged 13-14 years) from two separate classes over eleven weeks.…

  6. Nonlinear H-ininity state feedback controllers:

    DEFF Research Database (Denmark)

    Cromme, Marc; Møller-Pedersen, Jens; Pagh Petersen, Martin

    1997-01-01

    From a general point of view the state feedback H∞ suboptimal control problem is reasonably well understood. Important problems remain with regard to a priori information of the size of the neighbourhood where the local state feedback H∞ problem is solvable. This problem is solved regionally...

  7. Inoculating Relevance Feedback Against Poison Pills

    NARCIS (Netherlands)

    Dehghani, Mostafa; Azarbonyad, Hosein; Kamps, Jaap; Hiemstra, Djoerd; Marx, Maarten

    Relevance Feedback is a common approach for enriching queries, given a set of explicitly or implicitly judged documents to improve the performance of the retrieval. Although it has been shown that on average, the overall performance of retrieval will be improved after relevance feedback, for some

  8. Technologies for Learner-Centered Feedback

    Science.gov (United States)

    Costello, Jane; Crane, Daph

    2013-01-01

    As the number, type, and use of technologies to support learning increases, so do the opportunities for using these technologies for feedback. Learner-centered feedback is a core to the teaching-learning process. It is related to assessment in describing how learners perform in their learning, their gain in knowledge, skills, and attitudes.…

  9. Optical feedback structures and methods of making

    Science.gov (United States)

    None

    2014-11-18

    An optical resonator can include an optical feedback structure disposed on a substrate, and a composite including a matrix including a chromophore. The composite disposed on the substrate and in optical communication with the optical feedback structure. The chromophore can be a semiconductor nanocrystal. The resonator can provide laser emission when excited.

  10. Exploring Elementary Student Perceptions of Writing Feedback

    Science.gov (United States)

    Marrs, Sarah; Zumbrunn, Sharon; McBride, Caitlin; Stringer, J. K.

    2016-01-01

    The purpose of this descriptive qualitative investigation was to explore elementary students' (N = 867) perceptions of the feedback they receive on their writing. After responding to the closed-ended question, "Do you like to receive feedback about your writing?" students were branched to the appropriate follow-up open-ended question,…

  11. 10 CFR 850.40 - Performance feedback.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Performance feedback. 850.40 Section 850.40 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements § 850.40 Performance feedback. (a) The responsible employer must conduct periodic analyses and assessments of...

  12. {PET}ECUBE: a Multimodal Feedback Interface

    OpenAIRE

    Bennett, Peter

    2006-01-01

    The PETECUBE project consists of a series of musical interfaces designed to explore multi-modal feedback. This paper will briefly describe the definition of multimodal feedback, the aim of the project, the development of the first PETECUBE and proposed further work.

  13. Augmenting Environmental Interaction in Audio Feedback Systems

    Directory of Open Access Journals (Sweden)

    Seunghun Kim

    2016-04-01

    Full Text Available Audio feedback is defined as a positive feedback of acoustic signals where an audio input and output form a loop, and may be utilized artistically. This article presents new context-based controls over audio feedback, leading to the generation of desired sonic behaviors by enriching the influence of existing acoustic information such as room response and ambient noise. This ecological approach to audio feedback emphasizes mutual sonic interaction between signal processing and the acoustic environment. Mappings from analyses of the received signal to signal-processing parameters are designed to emphasize this specificity as an aesthetic goal. Our feedback system presents four types of mappings: approximate analyses of room reverberation to tempo-scale characteristics, ambient noise to amplitude and two different approximations of resonances to timbre. These mappings are validated computationally and evaluated experimentally in different acoustic conditions.

  14. Social feedback processing from early to late adolescence: influence of sex, age, and attachment style

    Science.gov (United States)

    Vrtička, Pascal; Sander, David; Anderson, Brittany; Badoud, Deborah; Eliez, Stephan; Debbané, Martin

    2014-01-01

    Objective The establishment of an accurate understanding of one's social context is a central developmental task during adolescence. A critical component of such development is to learn how to integrate the objective evaluation of one's behavior with the social response to the latter—here referred to as social feedback processing. Case report We measured brain activity by means of fMRI in 33 healthy adolescents (12–19 years old, 14 females). Participants played a difficult perceptual game with integrated verbal and visual feedback. Verbal feedback provided the participants with objective performance evaluation (won vs. lost). Visual feedback consisted of either smiling or angry faces, representing positive or negative social evaluations. Together, the combination of verbal and visual feedback gave rise to congruent versus incongruent social feedback combinations. In addition to assessing sex differences, we further tested for the effects of age and attachment style on social feedback processing. Results revealed that brain activity during social feedback processing was significantly modulated by sex, age, and attachment style in prefrontal cortical areas, ventral anterior cingulate cortex, anterior insula, caudate, and amygdala/hippocampus. We found indication for heightened activity during incongruent social feedback processing in females, older participants, and individuals with an anxious attachment style. Conversely, we observed stronger activity during processing of congruent social feedback in males and participants with an avoidant attachment style. Conclusion Our findings not only extend knowledge on the typical development of socio-emotional brain function during adolescence, but also provide first clues on how attachment insecurities, and particularly attachment avoidance, could interfere with the latter mechanisms. PMID:25328847

  15. Carbon-climate feedbacks accelerate ocean acidification

    Science.gov (United States)

    Matear, Richard J.; Lenton, Andrew

    2018-03-01

    Carbon-climate feedbacks have the potential to significantly impact the future climate by altering atmospheric CO2 concentrations (Zaehle et al. 2010). By modifying the future atmospheric CO2 concentrations, the carbon-climate feedbacks will also influence the future ocean acidification trajectory. Here, we use the CO2 emissions scenarios from four representative concentration pathways (RCPs) with an Earth system model to project the future trajectories of ocean acidification with the inclusion of carbon-climate feedbacks. We show that simulated carbon-climate feedbacks can significantly impact the onset of undersaturated aragonite conditions in the Southern and Arctic oceans, the suitable habitat for tropical coral and the deepwater saturation states. Under the high-emissions scenarios (RCP8.5 and RCP6), the carbon-climate feedbacks advance the onset of surface water under saturation and the decline in suitable coral reef habitat by a decade or more. The impacts of the carbon-climate feedbacks are most significant for the medium- (RCP4.5) and low-emissions (RCP2.6) scenarios. For the RCP4.5 scenario, by 2100 the carbon-climate feedbacks nearly double the area of surface water undersaturated with respect to aragonite and reduce by 50 % the surface water suitable for coral reefs. For the RCP2.6 scenario, by 2100 the carbon-climate feedbacks reduce the area suitable for coral reefs by 40 % and increase the area of undersaturated surface water by 20 %. The sensitivity of ocean acidification to the carbon-climate feedbacks in the low to medium emission scenarios is important because recent CO2 emission reduction commitments are trying to transition emissions to such a scenario. Our study highlights the need to better characterise the carbon-climate feedbacks and ensure we do not underestimate the projected ocean acidification.

  16. Feedback in Clinical Education, Part I: Characteristics of Feedback Provided by Approved Clinical Instructors

    Science.gov (United States)

    Nottingham, Sara; Henning, Jolene

    2014-01-01

    Context Providing students with feedback is an important component of athletic training clinical education; however, little information is known about the feedback that Approved Clinical Instructors (ACIs; now known as preceptors) currently provide to athletic training students (ATSs). Objective To characterize the feedback provided by ACIs to ATSs during clinical education experiences. Design Qualitative study. Setting One National Collegiate Athletic Association Division I athletic training facility and 1 outpatient rehabilitation clinic that were clinical sites for 1 entry-level master's degree program accredited by the Commission on Accreditation of Athletic Training Education. Patients or Other Participants A total of 4 ACIs with various experience levels and 4 second-year ATSs. Data Collection and Analysis Extensive field observations were audio recorded, transcribed, and integrated with field notes for analysis. The constant comparative approach of open, axial, and selective coding was used to inductively analyze data and develop codes and categories. Member checking, triangulation, and peer debriefing were used to promote trustworthiness of the study. Results The ACIs gave 88 feedback statements in 45 hours and 10 minutes of observation. Characteristics of feedback categories included purpose, timing, specificity, content, form, and privacy. Conclusions Feedback that ACIs provided included several components that made each feedback exchange unique. The ACIs in our study provided feedback that is supported by the literature, suggesting that ACIs are using current recommendations for providing feedback. Feedback needs to be investigated across multiple athletic training education programs to gain more understanding of certain areas of feedback, including frequency, privacy, and form. PMID:24143902

  17. "Homework Feedback Is…": Elementary and Middle School Teachers' Conceptions of Homework Feedback.

    Science.gov (United States)

    Cunha, Jennifer; Rosário, Pedro; Núñez, José Carlos; Nunes, Ana Rita; Moreira, Tânia; Nunes, Tânia

    2018-01-01

    This study explored mathematics teachers' conceptions of the homework feedback focusing on four key aspects: definition, purpose, types, and perceived impact. Forty-seven teachers from elementary and middle schools participated in six focus groups. Data were analyzed using content analysis. To enhance the trustworthiness of findings, classroom observations were used for triangulation of data. Participants conceptualized homework feedback in three directions (i.e., teachers' feedback provided to students, students' feedback provided to teachers, and homework self-feedback), being teachers' monitoring of students' learning the purpose reported by most teachers. Participants also reported the types of homework feedback more frequently used in class (e.g., checking homework completion, checking homework on the board), and their perceived impact on students. Findings provide valuable information to deepen the understanding of the homework feedback process, which may help develop new avenues for future research.

  18. “Homework Feedback Is…”: Elementary and Middle School Teachers’ Conceptions of Homework Feedback

    Science.gov (United States)

    Cunha, Jennifer; Rosário, Pedro; Núñez, José Carlos; Nunes, Ana Rita; Moreira, Tânia; Nunes, Tânia

    2018-01-01

    This study explored mathematics teachers’ conceptions of the homework feedback focusing on four key aspects: definition, purpose, types, and perceived impact. Forty-seven teachers from elementary and middle schools participated in six focus groups. Data were analyzed using content analysis. To enhance the trustworthiness of findings, classroom observations were used for triangulation of data. Participants conceptualized homework feedback in three directions (i.e., teachers’ feedback provided to students, students’ feedback provided to teachers, and homework self-feedback), being teachers’ monitoring of students’ learning the purpose reported by most teachers. Participants also reported the types of homework feedback more frequently used in class (e.g., checking homework completion, checking homework on the board), and their perceived impact on students. Findings provide valuable information to deepen the understanding of the homework feedback process, which may help develop new avenues for future research. PMID:29467687

  19. “Homework Feedback Is…”: Elementary and Middle School Teachers’ Conceptions of Homework Feedback

    Directory of Open Access Journals (Sweden)

    Jennifer Cunha

    2018-02-01

    Full Text Available This study explored mathematics teachers’ conceptions of the homework feedback focusing on four key aspects: definition, purpose, types, and perceived impact. Forty-seven teachers from elementary and middle schools participated in six focus groups. Data were analyzed using content analysis. To enhance the trustworthiness of findings, classroom observations were used for triangulation of data. Participants conceptualized homework feedback in three directions (i.e., teachers’ feedback provided to students, students’ feedback provided to teachers, and homework self-feedback, being teachers’ monitoring of students’ learning the purpose reported by most teachers. Participants also reported the types of homework feedback more frequently used in class (e.g., checking homework completion, checking homework on the board, and their perceived impact on students. Findings provide valuable information to deepen the understanding of the homework feedback process, which may help develop new avenues for future research.

  20. Delayed auditory feedback and aphasia.

    Science.gov (United States)

    Boller, F; Vrtunski, P B; Kim, Y; Mack, J L

    1978-06-01

    The effect of Delayed Auditory Feedback (DAF) was evaluated in three groups of subjects: 10 normal controls, 10 non-fluent aphasics, and 10 fluent aphasics. Speec production tasks consisted of (1) repeating sound and words; (2) naming objects; (3) producing sentences from given stimulus words; (4) answering questions; (5) reciting nursery rhymes; and (6) reading. Two delays were used, 180 and 360 msec. Two independent judges rated patients' responses for changes in intensity, duration, and quality of speech. Inter-judge reliability was considered satisfactory. Contrary to some previous reports, all subjects, including all the fluent aphasics, showed some DAF effect. Fluent aphasics, however, showed a significantly smaller DAF effect than non-fluent aphasics. Patient with conduction aphasia appeared to be the least impaired. Overall DAF effect was greater with 180 msec. than with 360 msec. The largest DAF effect occurred during answering question, followed by repeating, reading, nursery rhymes, sentence production, and naming, in that order. Repetition of a complex word produced a greater DAF effect than repetition of a simple sound. Finally, we found a differential effect of DAF on the three measures used in the study. We hypothesize that DAF effects result from changes in two separate monitoring systems. One systems is related to changes in the intensity of speech and does not appear to be affected by aphasia. The other is responsible for duration and qualitative changes in speech and is differentially affected in relation to pathology producing aphasia.

  1. Temperature feedback in virtual environments

    Science.gov (United States)

    Dionisio, Jose

    1997-02-01

    Virtual reality (VR) is known as one of the most exciting computer-related technologies. Although its definition is still vague among experts, it is expected that a VR system should give the user an experience of being 'immersed' in a synthesized environment. Aims of this deeper level of user immersion range from the look-like of the scenes where realistic rendering is one of the goals (vision stimulus), to interaction paradigms through the use of, e.g., dataglove peripherals type, to acoustics (earring stimulus) trying to merge as much as possible the human senses towards the desired immersion. Attempting to increase the previously mentioned realism, an extra sensorial perception is recalled and the user is exposed to the feeling of 'virtual comfort' by means of a new parameter: the temperature. The obtained results concentrate on interaction paradigms and couple input/output feedback, emphasizing the factor 'presence.' The prototype, although conceptually simple, brings together within a couple of virtual scenarios, a software/hardware solution, so far original in this field.

  2. Relay Selection with Limited and Noisy Feedback

    KAUST Repository

    Eltayeb, Mohammed E.

    2016-01-28

    Relay selection is a simple technique that achieves spatial diversity in cooperative relay networks. Nonetheless, relay selection algorithms generally require error-free channel state information (CSI) from all cooperating relays. Practically, CSI acquisition generates a great deal of feedback overhead that could result in significant transmission delays. In addition to this, the fed back channel information is usually corrupted by additive noise. This could lead to transmission outages if the central node selects the set of cooperating relays based on inaccurate feedback information. In this paper, we propose a relay selection algorithm that tackles the above challenges. Instead of allocating each relay a dedicated channel for feedback, all relays share a pool of feedback channels. Following that, each relay feeds back its identity only if its effective channel (source-relay-destination) exceeds a threshold. After deriving closed-form expressions for the feedback load and the achievable rate, we show that the proposed algorithm drastically reduces the feedback overhead and achieves a rate close to that obtained by selection algorithms with dedicated error-free feedback from all relays. © 2015 IEEE.

  3. Development of a teleoperated micromanipulation system with visual and haptic feedback

    Science.gov (United States)

    Ferreira, Antoine; Cassier, Claude; Haddab, Yassine; Rougeot, Patrick; Chaillet, Nicolas

    2001-10-01

    Concerning the teleoperation between different scale worlds, it is important to take into account the scaling effect problem in terms of manipulator precision, human sensation, environment accessibility, dexterity, etc. To consider these different problems, this paper presents the development of a new macro-micro teleoperated micromanipulator, with two kinds of micromanipulation systems: a piezoelectric microgripper and an atomic force microscope (AFM) operating under an optical microscope. The natural force feedback sensation exerted on the piezoelectric microgripper is given through a teleoperated two-fingered planar hand mechanism. This system provides the human operator with natural force feedback sensation and augmented visual feedback while telemanipulating objects in the micro world. Firstly, the bilateral control system with active force feedback based on hybrid master-slave technologies is modeled. The results include the use of force feedback and power assist in order to demonstrate the feasibility and practicability of the micro-teleoperated system. Then, in order to improve the visual feedback issued form the optical microscope of the station, a virtual micro 3D environment is proposed. By combining 2D microscope images and augmented reality-based programming techniques, we reconstructed exactly the operational microworld. Finally, some experiments have been carried out in order to verify the validity of the proposed bilateral control scheme and to calibrate the developed virtual model incorporating visual and haptic feedback.

  4. Prefrontal cortex and striatal activation by feedback in Parkinson's disease

    NARCIS (Netherlands)

    Keitz, Martijn; Koerts, Janneke; Kortekaas, Rudie; Renken, Remco; de Jong, Bauke M.; Leenders, Klaus L.

    2008-01-01

    Positive feedbacks reinforce goal-directed behavior and evoke pleasure. in Parkinson's disease (PD) the striatal dysfunction impairs motor performance, but also may lead to decreased positive feedback (reward) processing. This study investigates two types of positive feedback processing (monetary

  5. Effects of visual feedback-induced variability on motor learning of handrim wheelchair propulsion.

    Directory of Open Access Journals (Sweden)

    Marika T Leving

    Full Text Available It has been suggested that a higher intra-individual variability benefits the motor learning of wheelchair propulsion. The present study evaluated whether feedback-induced variability on wheelchair propulsion technique variables would also enhance the motor learning process. Learning was operationalized as an improvement in mechanical efficiency and propulsion technique, which are thought to be closely related during the learning process.17 Participants received visual feedback-based practice (feedback group and 15 participants received regular practice (natural learning group. Both groups received equal practice dose of 80 min, over 3 weeks, at 0.24 W/kg at a treadmill speed of 1.11 m/s. To compare both groups the pre- and post-test were performed without feedback. The feedback group received real-time visual feedback on seven propulsion variables with instruction to manipulate the presented variable to achieve the highest possible variability (1st 4-min block and optimize it in the prescribed direction (2nd 4-min block. To increase motor exploration the participants were unaware of the exact variable they received feedback on. Energy consumption and the propulsion technique variables with their respective coefficient of variation were calculated to evaluate the amount of intra-individual variability.The feedback group, which practiced with higher intra-individual variability, improved the propulsion technique between pre- and post-test to the same extent as the natural learning group. Mechanical efficiency improved between pre- and post-test in the natural learning group but remained unchanged in the feedback group.These results suggest that feedback-induced variability inhibited the improvement in mechanical efficiency. Moreover, since both groups improved propulsion technique but only the natural learning group improved mechanical efficiency, it can be concluded that the improvement in mechanical efficiency and propulsion technique do not

  6. Generalized fast feedback system in the SLC

    International Nuclear Information System (INIS)

    Hendrickson, L.; Allison, S.; Gromme, T.; Himel, T.; Krauter, K.; Rouse, F.; Sass, R.; Shoaee, H.

    1991-11-01

    A generalized fast feedback system has been developed to stabilize beams at various locations in the SLC. The system is designed to perform measurements and change actuator settings to control beam states such as position, angle and energy on a pulse to pulse basis. The software design is based on the state space formalism of digital control theory. The system is database-driven, facilitating the addition of new loops without requiring additional software. A communications system, KISNet, provides fast communications links between microprocessors for feedback loops which involve multiple micros. Feedback loops have been installed in seventeen locations throughout the SLC and have proven to be invaluable in stabilizing the machine

  7. Generalized fast feedback system in the SLC

    International Nuclear Information System (INIS)

    Hendrickson, L.; Allison, S.; Gromme, T.; Himel, T.; Krauter, K.; Rouse, F.; Sass, R.; Shoaee, H.

    1992-01-01

    A generalized fast feedback system has been developed to stabilize beams at various locations in the SLC. The system is designed to perform measurements and change actuator settings to control beam states such as position, angle and energy on a pulse to pulse basis. The software design is based on the state space formalism of digital control theory. The system is database-driven, facilitating the addition of new loops without requiring additional software. A communications system, KISNet, provides fast communications links between microprocessors for feedback loops which involve multiple micros. Feedback loops have been installed in seventeen locations throughout the SLC and have proven to be invaluable in stabilizing the machine. (author)

  8. Continuous Student Feedback: Your Voice Counts.

    Science.gov (United States)

    Palazzo, Steven J; Miller, Carrie Westmoreland; Salvatierra, Gail

    We created a method to collect continuous course feedback called Your Voice Counts. We sought to create a highly flexible and highly responsive learning environment that had as one of its unique properties the ability to meet the different needs of successive student cohorts. Student feedback has created opportunities for us to address issues in a timely and responsive manner. We believe in managing students' expectations as well as offering a means of continuous formative feedback that sets the stage for active learning by promoting an inclusive environment that supports the development of positive attitudes toward learning.

  9. Controlling entanglement by direct quantum feedback

    Science.gov (United States)

    Carvalho, A. R. R.; Reid, A. J. S.; Hope, J. J.

    2008-07-01

    We discuss the generation of entanglement between electronic states of two atoms in a cavity using direct quantum feedback schemes. We compare the effects of different control Hamiltonians and detection processes in the performance of entanglement production and show that the quantum-jump-based feedback proposed by Carvalho and Hope [Phys. Rev. A 76, 010301(R) (2007)] can protect highly entangled states against decoherence. We provide analytical results that explain the robustness of jump feedback, and also analyze the perspectives of experimental implementation by scrutinizing the effects of imperfections and approximations in our model.

  10. Multibunch feedback: Strategy, technology and implementation options

    International Nuclear Information System (INIS)

    Fox, J.D.; Eisen, N.; Hindi, H.; Oxoby, G.; Sapozhnikov, L.; Linscott, I.; Serio, M.

    1992-10-01

    The proposed next generation accelerator and synchrotron light facilities will require active feedback systems to control multi-bunch instabilities. These feedback systems must operate in machines with thousands of circulating bunches and with short (2--4 ns) interbunch intervals. The functional requirements for transverse (betatron) and longitudinal (synchrotron) feedback systems are presented. Several possible implementation options are discussed and system requirements developed. Results are presented from a digital signal processing based synchrotron oscillation damper operating at the SSRL/SLAC SPEAR storage ring

  11. Haptic seat for fuel economy feedback

    Energy Technology Data Exchange (ETDEWEB)

    Bobbitt, III, John Thomas

    2016-08-30

    A process of providing driver fuel economy feedback is disclosed in which vehicle sensors provide for haptic feedback on fuel usage. Such sensors may include one or more of a speed sensors, global position satellite units, vehicle pitch/roll angle sensors, suspension displacement sensors, longitudinal accelerometer sensors, throttle position in sensors, steering angle sensors, break pressure sensors, and lateral accelerometer sensors. Sensors used singlely or collectively can provide enhanced feedback as to various environmental conditions and operating conditions such that a more accurate assessment of fuel economy information can be provided to the driver.

  12. Improving e-learning by Emotive Feedback

    DEFF Research Database (Denmark)

    Sharp, Robin; Gjedde, Lisa

    2011-01-01

    This paper considers the use of feedback with emotive elements in order to improve the efficiency of e-learning for teaching complex technical subjects to the general public by stimulation of implicit learning. An example is presented, based on an effort to investigate the current level of IT sec......This paper considers the use of feedback with emotive elements in order to improve the efficiency of e-learning for teaching complex technical subjects to the general public by stimulation of implicit learning. An example is presented, based on an effort to investigate the current level...... for exploration and reflection that is supported by the feedback offered by the system....

  13. Pinhole Luminosity Monitor with Feedback

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, J

    2004-05-17

    Previously, the generalized luminosity L was defined and calculated for all incident channels based on an NLC e{sup +}e{sup -} design. Alternatives were then considered to improve the differing beam-beam e{sup -}e{sup -} e{gamma} and {gamma}{gamma} channels. Regardless of the channel, there was a large flux of outgoing, high energy photons that were produced from the beam-beam interaction e.g. beamsstrahlung that needs to be disposed of and whose flux depended on L. One approach to this problem is to consider it a resource and attempt to take advantage of it by disposing of these straight-ahead photons in more useful ways than simply dumping them. While there are many options for monitoring the luminosity, any method that allows feedback and optimization in real time and in a non-intercepting and non-interfering way during normal data taking is extremely important--especially if it provides other capabilities such as high resolution tuning of spot sizes and can be used for all incident channels without essential modifications to their setup. Our ''pin-hole'' camera appears to be such a device if it can be made to work with high energy photons in ways that are compatible with the many other constraints and demands on space around the interaction region. The basis for using this method is that it has, in principle, the inherent resolution and bandwidth to monitor the very small spot sizes and their stabilities that are required for very high, integrated luminosity. While there are many possible, simultaneous uses of these outgoing photon beams, we limit our discussion to a single, blind, proof-of-principle experiment that was done on the FFTB line at SLAC to certify the concept of a camera obscura for high energy photons.

  14. Rlm1 mediates positive autoregulatory transcriptional feedback that is essential for Slt2-dependent gene expression.

    Science.gov (United States)

    García, Raúl; Sanz, Ana Belén; Rodríguez-Peña, José Manuel; Nombela, César; Arroyo, Javier

    2016-04-15

    Activation of the yeast cell wall integrity (CWI) pathway induces an adaptive transcriptional programme that is largely dependent on the transcription factor Rlm1 and the mitogen-activated protein kinase (MAPK) Slt2. Upon cell wall stress, the transcription factor Rlm1 is recruited to the promoters of RLM1 and SLT2, and exerts positive-feedback mechanisms on the expression of both genes. Activation of the MAPK Slt2 by cell wall stress is not impaired in strains with individual blockade of any of the two feedback pathways. Abrogation of the autoregulatory feedback mechanism on RLM1 severely affects the transcriptional response elicited by activation of the CWI pathway. In contrast, a positive trans-acting feedback mechanism exerted by Rlm1 on SLT2 also regulates CWI output responses but to a lesser extent. Therefore, a complete CWI transcriptional response requires not only phosphorylation of Rlm1 by Slt2 but also concurrent SLT2- and RLM1-mediated positive-feedback mechanisms; sustained patterns of gene expression are mainly achieved by positive autoregulatory circuits based on the transcriptional activation of Rlm1. © 2016. Published by The Company of Biologists Ltd.

  15. Depression as a systemic syndrome: mapping the feedback loops of major depressive disorder.

    Science.gov (United States)

    Wittenborn, A K; Rahmandad, H; Rick, J; Hosseinichimeh, N

    2016-02-01

    Depression is a complex public health problem with considerable variation in treatment response. The systemic complexity of depression, or the feedback processes among diverse drivers of the disorder, contribute to the persistence of depression. This paper extends prior attempts to understand the complex causal feedback mechanisms that underlie depression by presenting the first broad boundary causal loop diagram of depression dynamics. We applied qualitative system dynamics methods to map the broad feedback mechanisms of depression. We used a structured approach to identify candidate causal mechanisms of depression in the literature. We assessed the strength of empirical support for each mechanism and prioritized those with support from validation studies. Through an iterative process, we synthesized the empirical literature and created a conceptual model of major depressive disorder. The literature review and synthesis resulted in the development of the first causal loop diagram of reinforcing feedback processes of depression. It proposes candidate drivers of illness, or inertial factors, and their temporal functioning, as well as the interactions among drivers of depression. The final causal loop diagram defines 13 key reinforcing feedback loops that involve nine candidate drivers of depression. Future research is needed to expand upon this initial model of depression dynamics. Quantitative extensions may result in a better understanding of the systemic syndrome of depression and contribute to personalized methods of evaluation, prevention and intervention.

  16. Depression as a systemic syndrome: mapping the feedback loops of major depressive disorder

    Science.gov (United States)

    Wittenborn, A. K.; Rahmandad, H.; Rick, J.; Hosseinichimeh, N.

    2016-01-01

    Background Depression is a complex public health problem with considerable variation in treatment response. The systemic complexity of depression, or the feedback processes among diverse drivers of the disorder, contribute to the persistence of depression. This paper extends prior attempts to understand the complex causal feedback mechanisms that underlie depression by presenting the first broad boundary causal loop diagram of depression dynamics. Method We applied qualitative system dynamics methods to map the broad feedback mechanisms of depression. We used a structured approach to identify candidate causal mechanisms of depression in the literature. We assessed the strength of empirical support for each mechanism and prioritized those with support from validation studies. Through an iterative process, we synthesized the empirical literature and created a conceptual model of major depressive disorder. Results The literature review and synthesis resulted in the development of the first causal loop diagram of reinforcing feedback processes of depression. It proposes candidate drivers of illness, or inertial factors, and their temporal functioning, as well as the interactions among drivers of depression. The final causal loop diagram defines 13 key reinforcing feedback loops that involve nine candidate drivers of depression. Conclusions Future research is needed to expand upon this initial model of depression dynamics. Quantitative extensions may result in a better understanding of the systemic syndrome of depression and contribute to personalized methods of evaluation, prevention and intervention. PMID:26621339

  17. Comprehensive feedback on trainee surgeons' non-technical skills

    DEFF Research Database (Denmark)

    Spanager, Lene; Dieckmann, Peter; Beier-Holgersen, Randi

    2015-01-01

    OBJECTIVE: This study aimed to explore the content of conversations, feedback style, and perceived usefulness of feedback to trainee surgeons when conversations were stimulated by a tool for assessing surgeons' non-technical skills. METHODS: Trainee surgeons and their supervisors used the Non......-Technical Skills for Surgeons in Denmark tool to stimulate feedback conversations. Audio recordings of post-operation feedback conversations were collected. Trainees and supervisors provided questionnaire responses on the usefulness and comprehensiveness of the feedback. The feedback conversations were...

  18. Feedback is good or bad? Medical residents’ points of view on feedback in clinical education

    Directory of Open Access Journals (Sweden)

    LEILA BAZRAFKAN

    2013-04-01

    Full Text Available Introduction: Feedback is very important in education and can help quality in the training process and orient the trainees in clinical contexts. This study aimed to assess the residents’ points of view about feedback in clinical education at Shiraz University of Medical Sciences. Methods: The sample of this study included 170 medical residents attending medical workshops in Shiraz University of Medical Sciences. The residents filled a valid and reliable questionnaire containing 21 items on their perceptions of the feedback they got throughout the workshops. The data were analyzed using SPSS version 14. Results: The study revealed that residents, generally, have a positive perception of feedback in their training. The highest score belonged to the items such as “feedback was applicable to future work”, “feedback corrected my behavior”, “feedback worked as a motivation for education” and “feedback was specific in one subject”. Residents who had a negative feedback experience also increased their efforts to learn. The Surgery residents acquired the highest scores while radiology residents got the lowest. The difference between these groups was statistically significant (P = 0.000. Conclusion: The highest mean score belonged to internal medicine residents. This shows that residents believe that obstetrics & gynecology ward is a ward in which the formative assessment is much more powerful in comparison to the other three major wards. The surgery ward received the lowest score for formative assessment and this shows that the feedback in surgery ward is very low.

  19. Influence of feedback characteristics on perceived learning value of feedback in clerkships: does culture matter?

    Science.gov (United States)

    Suhoyo, Yoyo; Van Hell, Elisabeth A; Kerdijk, Wouter; Emilia, Ova; Schönrock-Adema, Johanna; Kuks, Jan B M; Cohen-Schotanus, Janke

    2017-04-05

    Various feedback characteristics have been suggested to positively influence student learning. It is not clear how these feedback characteristics contribute to students' perceived learning value of feedback in cultures classified low on the cultural dimension of individualism and high on power distance. This study was conducted to validate the influence of five feedback characteristics on students' perceived learning value of feedback in an Indonesian clerkship context. We asked clerks in Neurology (n = 169) and Internal Medicine (n = 132) to assess on a 5-point Likert scale the learning value of the feedback they received. We asked them to record whether the feedback provider (1) informed the student what went well, (2) mentioned which aspects of performance needed improvement, (3) compared the student's performance to a standard, (4) further explained or demonstrated the correct performance, and (5) prepared an action plan with the student to improve performance. Data were analyzed using multilevel regression. A total of 250 students participated in this study, 131 from Internal Medicine (response rate 99%) and 119 from Neurology (response rate 70%). Of these participants, 225 respondents (44% males, 56% females) completed the form and reported 889 feedback moments. Students perceived feedback as more valuable when the feedback provider mentioned their weaknesses (β = 0.153, p perceived learning value of feedback. No gender differences were found for perceived learning value. In Indonesia, we could validate four out of the five characteristics for effective feedback. We argue that our findings relate to culture, in particular to the levels of individualism and power distance. The recognized characteristics of what constitutes effective feedback should be validated across cultures.

  20. Augmented visual feedback counteracts the effects of surface muscular functional electrical stimulation on physiological tremor

    Science.gov (United States)

    2013-01-01

    Background Recent studies suggest that surface muscular functional electrical stimulation (FES) might suppress neurological upper limb tremor. We assessed its effects on upper limb physiological tremor, which is mainly driven by mechanical-reflex oscillations. We investigated the interaction between FES and augmented visual feedback, since (a) most daily activities are performed using visual cues, and (b) augmented visual feedback exacerbates upper limb tremor. Methods 10 healthy subjects (23.4 ± 7.7 years) performed 2 postural tasks with combinations of FES (4 sites; frequency of stimulation: 30 Hz; pulse width: 300 microsec; range of current delivered 10–34 mAmp) and augmented visual feedback. Results Spectral analysis of tremor showed a decrease of power spectral density to 62.18% (p = 0.01), of the integral in the 8-12 Hz frequency band to 57.67% (p = 0.003), and of tremor root mean square (RMS) to 57.16% (p = 0.002) during FES, without any changes in tremor frequency. Augmented visual feedback blocked the beneficial effect of FES, as confirmed by power spectral analysis (p = 0.01). We found a statistically significant interaction between augmented visual feedback and electrical stimulation (p = 0.039). Conclusions Augmented visual feedback antagonizes the effects of FES on physiological tremor. The absence of changes of peak frequency argues against an effect of FES on mechanical properties of the upper limb. PMID:24063436

  1. Randomised prior feedback modulates neural signals of outcome monitoring.

    Science.gov (United States)

    Mushtaq, Faisal; Wilkie, Richard M; Mon-Williams, Mark A; Schaefer, Alexandre

    2016-01-15

    Substantial evidence indicates that decision outcomes are typically evaluated relative to expectations learned from relatively long sequences of previous outcomes. This mechanism is thought to play a key role in general learning and adaptation processes but relatively little is known about the determinants of outcome evaluation when the capacity to learn from series of prior events is difficult or impossible. To investigate this issue, we examined how the feedback-related negativity (FRN) is modulated by information briefly presented before outcome evaluation. The FRN is a brain potential time-locked to the delivery of decision feedback and it is widely thought to be sensitive to prior expectations. We conducted a multi-trial gambling task in which outcomes at each trial were fully randomised to minimise the capacity to learn from long sequences of prior outcomes. Event-related potentials for outcomes (Win/Loss) in the current trial (Outcomet) were separated according to the type of outcomes that occurred in the preceding two trials (Outcomet-1 and Outcomet-2). We found that FRN voltage was more positive during the processing of win feedback when it was preceded by wins at Outcomet-1 compared to win feedback preceded by losses at Outcomet-1. However, no influence of preceding outcomes was found on FRN activity relative to the processing of loss feedback. We also found no effects of Outcomet-2 on FRN amplitude relative to current feedback. Additional analyses indicated that this effect was largest for trials in which participants selected a decision different to the gamble chosen in the previous trial. These findings are inconsistent with models that solely relate the FRN to prediction error computation. Instead, our results suggest that if stable predictions about future events are weak or non-existent, then outcome processing can be determined by affective systems. More specifically, our results indicate that the FRN is likely to reflect the activity of positive

  2. Load rather than length sensitive feedback contributes to soleus muscle activity during human treadmill walking

    DEFF Research Database (Denmark)

    af Klint, Richard; Mazzaro, Nazarena; Nielsen, Jens Bo

    2010-01-01

    Walking requires a constant adaptation of locomotor output from sensory afferent feedback mechanisms to ensure efficient and stable gait. We investigated the nature of the sensory afferent feedback contribution to the soleus motoneuronal drive and to the corrective stretch reflex by manipulating...... on the soleus stretch reflex was measured by presenting dorsiflexion perturbations ( approximately 5 degrees, 360-400 degrees/s) in mid and late stances. Short (SLRs) and medium latency reflexes (MLRs) were quantified in a 15 ms analysis window. The MLR decreased with decreased loading (P = 0......-related afferent feedback contributes both to the background locomotor activity and to the medium latency stretch reflex. In contrast, length-related afferent feedback may contribute to only the medium latency stretch reflex....

  3. Evidence of fast non-linear feedback in EBR-II rod-drop measurements

    International Nuclear Information System (INIS)

    Grimm, K.N.; Meneghetti, D.

    1987-06-01

    Feedback reactivities determine the time dependence of a reactor during and after a transient initiating event. Recent analysis of control-rod drops in the Experimental Breeder Reactor II (EBR-II) Reactor has indicated that some relatively fast feedback may exist which cannot be accounted for by the linear feedback mechanisms. The linear and deduced non-linear feedback reactivities from a control-rod drop in EBR-II run 93A using detailed temperature coefficients of reactivity in the EROS kinetics code have been reported. The transient analyses have now been examined in more detail for times close to the drop to ascertain if additional positive reactivity is being built-in early in the drop which could be gradually released later in the drop

  4. Detecting vegetation-precipitation feedbacks in mid-Holocene North Africa from two climate models

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yi; Notaro, Michael; Liu, Zhengyu; Gallimore, Robert; Levis, Samuel; Kutzbach, John E.

    2008-03-31

    Using two climate-vegetation model simulations from the Fast Ocean Atmosphere Model (FOAM) and the Community Climate System Model (CCSM, version 2), we investigate vegetation-precipitation feedbacks across North Africa during the mid-Holocene. From mid-Holocene snapshot runs of FOAM and CCSM2, we detect a negative feedback at the annual timescale with our statistical analysis. Using the Monte- Carlo bootstrap method, the annual negative feedback is further confirmed to be significant in both simulations. Additional analysis shows that this negative interaction is partially caused by the competition between evaporation and transpiration in North African grasslands. Furthermore, we find the feedbacks decrease with increasing timescales, and change signs from positive to negative at increasing timescales in FOAM. The proposed mechanism for this sign switch is associated with the different persistent timescales of upper and lower soil water contents, and their interactions with vegetation and atmospheric precipitation.

  5. Research of the master-slave robot surgical system with the function of force feedback.

    Science.gov (United States)

    Shi, Yunyong; Zhou, Chaozheng; Xie, Le; Chen, Yongjun; Jiang, Jun; Zhang, Zhenfeng; Deng, Ze

    2017-12-01

    Surgical robots lack force feedback, which may lead to operation errors. In order to improve surgical outcomes, this research developed a new master-slave surgical robot, which was designed with an integrated force sensor. The new structure designed for the master-slave robot employs a force feedback mechanism. A six-dimensional force sensor was mounted on the tip of the slave robot's actuator. Sliding model control was adopted to control the slave robot. According to the movement of the master system manipulated by the surgeon, the slave's movement and the force feedback function were validated. The motion was completed, the standard deviation was calculated, and the force data were detected. Hence, force feedback was realized in the experiment. The surgical robot can help surgeons to complete trajectory motions with haptic sensation. Copyright © 2017 John Wiley & Sons, Ltd.

  6. Feedback providing improvement strategies and reflection on feedback use: Effects on students' writing motivation, process, and performance

    NARCIS (Netherlands)

    Duijnhouwer, H.; Prins, F.J.; Stokking, K.M.

    2012-01-01

    This study investigated the effects of feedback providing improvement strategies and a reflection assignment on students’ writing motivation, process, and performance. Students in the experimental feedback condition (n = 41) received feedback including improvement strategies, whereas students in the

  7. Feedback regulation of pancreatic exocrine secretion in minipigs.

    Science.gov (United States)

    Houe, T; Saetre, S S; Svendsen, P; Olsen, O; Rehfeld, J F; Schaffalitzky de Muckadell, O B

    1997-04-01

    The mechanism behind the possible feedback regulation of pancreatic exocrine secretion is not well understood. Thirteen minipigs were prepared with fistulas to the pancreatic duct and the duodenum. Peripheral venous blood was obtained for determination of secretin and cholecystokinin (CCK) levels. Four different experiments were performed: 1) diversion and reinfusion of pancreatic juice; 2) intraduodenal infusion of NaHCO3 solution, with the same volume, bicarbonate concentration, and osmolality as the collected pancreatic secretion, and reinfusion of pancreatic juice; 3) reinfusion of pancreatic secretion for 1 h before and 2 h after a meal; and 4) diversion of pancreatic secretion and intraduodenal infusion of NaHCO33 solutions before and after a meal. Reinfusing pancreatic juice significantly decreased pancreatic juice volume and bicarbonate output and slightly decreased the level of secretin in plasma. Alternating infusions of substitute NaHCO3 and pancreatic juice did not change pancreatic output of bicarbonate and protein, nor did it change the CCK and secretin levels in plasma. Replacing pancreatic juice with intraduodenal NaHCO3 infusions during a meal did not significantly modify the pancreatic secretion of bicarbonate and protein or the hormonal levels in blood. A negative feedback regulation of pancreatic exocrine secretion is present in starved minipigs. Duodenal acidity and plasma levels of secretin semm to be of importance, whereas duodenal enzyme activity and the level of CCK in plasma probably are not. A postprandial negative feedback regulation through duodenal enzymatic activity and release of CCK into blood could not be shown.

  8. Microbial contributions to climate change through carbon cycle feedbacks.

    Science.gov (United States)

    Bardgett, Richard D; Freeman, Chris; Ostle, Nicholas J

    2008-08-01

    There is considerable interest in understanding the biological mechanisms that regulate carbon exchanges between the land and atmosphere, and how these exchanges respond to climate change. An understanding of soil microbial ecology is central to our ability to assess terrestrial carbon cycle-climate feedbacks, but the complexity of the soil microbial community and the many ways that it can be affected by climate and other global changes hampers our ability to draw firm conclusions on this topic. In this paper, we argue that to understand the potential negative and positive contributions of soil microbes to land-atmosphere carbon exchange and global warming requires explicit consideration of both direct and indirect impacts of climate change on microorganisms. Moreover, we argue that this requires consideration of complex interactions and feedbacks that occur between microbes, plants and their physical environment in the context of climate change, and the influence of other global changes which have the capacity to amplify climate-driven effects on soil microbes. Overall, we emphasize the urgent need for greater understanding of how soil microbial ecology contributes to land-atmosphere carbon exchange in the context of climate change, and identify some challenges for the future. In particular, we highlight the need for a multifactor experimental approach to understand how soil microbes and their activities respond to climate change and consequences for carbon cycle feedbacks.

  9. Enhanced Feedback-Related Negativity in Alzheimer’s Disease

    Directory of Open Access Journals (Sweden)

    Shuhei Yamaguchi

    2017-04-01

    Full Text Available Alzheimer’s disease (AD, the most common cause of dementia in the elderly, results in the impairment of executive function, including that of performance monitoring. Feedback-related negativity (FRN is an electrophysiological measure reflecting the activity of this monitoring system via feedback signals, and is generated from the anterior cingulate cortex. However, there have been no reports on FRN in AD. Based on prior aging studies, we hypothesized that FRN would decrease in AD patients. To assess this, FRN was measured in healthy individuals and those with AD during a simple gambling task involving positive and negative feedback stimuli. Contrary to our hypothesis, FRN amplitude increased in AD patients, compared with the healthy elderly. We speculate that this may reflect the existence of a compensatory mechanism against the decline in executive function. Also, there was a significant association between FRN amplitude and depression scores in AD, and the FRN amplitude tended to increase insomuch as the Self-rating Depression Scale (SDS was higher. This result suggests the existence of a negative bias in the affective state in AD. Thus, the impaired functioning monitoring system in AD is a more complex phenomenon than we thought.

  10. Operational safety experience feedback by means of unusual event reports

    International Nuclear Information System (INIS)

    1996-07-01

    Operational experience of nuclear power plants can be used to great advantage to enhance safety performance provided adequate measures are in place to collect and analyse it and to ensure that the conclusions drawn are acted upon. Feedback of operating experience is thus an extremely important tool to ensure high standards of safety in operational nuclear power plants and to improve the capability to prevent serious accidents and to learn from minor deviations and equipment failures - which can serve as early warnings -to prevent even minor events from occurring. Mechanisms also need to be developed to ensure that operating experience is shared both nationally as well as internationally. The operating experience feedback process needs to be fully and effectively established within the nuclear power plant, the utility, the regulatory organization as well as in other institutions such as technical support organizations and designers. The main purpose of this publication is to reflect the international consensus as to the general principles and practices in the operational safety experience feedback process. The examples of national practices for the whole or for particular parts of the process are given in annexes. The publication complements the IAEA Safety Series No.93 ''Systems for Reporting Unusual Events in Nuclear Power Plants'' (1989) and may also give a general guidance for Member States in fulfilling their obligations stipulated in the Nuclear Safety Convention. Figs, tabs

  11. Force feedback in a piezoelectric linear actuator for neurosurgery.

    Science.gov (United States)

    De Lorenzo, Danilo; De Momi, Elena; Dyagilev, Ilya; Manganelli, Rudy; Formaglio, Alessandro; Prattichizzo, Domenico; Shoham, Moshe; Ferrigno, Giancarlo

    2011-09-01

    Force feedback in robotic minimally invasive surgery allows the human operator to manipulate tissues as if his/her hands were in contact with the patient organs. A force sensor mounted on the probe raises problems with sterilization of the overall surgical tool. Also, the use of off-axis gauges introduces a moment that increases the friction force on the bearing, which can easily mask off the signal, given the small force to be measured. This work aims at designing and testing two methods for estimating the resistance to the advancement (force) experienced by a standard probe for brain biopsies within a brain-like material. The further goal is to provide a neurosurgeon using a master-slave tele-operated driver with direct feedback on the tissue mechanical characteristics. Two possible sensing methods, in-axis strain gauge force sensor and position-position error (control-based method), were implemented and tested, both aimed at device miniaturization. The analysis carried out was aimed at fulfilment of the psychophysics requirements for force detection and delay tolerance, also taking into account safety, which is directly related to the last two issues. Controller parameters definition is addressed and consideration is given to development of the device with integration of a haptic interface. Results show better performance of the control-based method (RMSE feedback in minimally invasive surgery allows the human operator to manipulate tissues as if his/her hands were in contact with the patient organs. Copyright © 2011 John Wiley & Sons, Ltd.

  12. Feature binding in the feedback layers of area V2.

    Science.gov (United States)

    Shipp, Stewart; Adams, Daniel L; Moutoussis, Konstantinos; Zeki, Semir

    2009-10-01

    The visual features of an object are processed by multiple, functionally specialized areas of cerebral cortex. When several objects are seen simultaneously, what mechanism preserves the association of features that belong to a single item? We address this question-known as the "binding problem"-by examining combinatorial feature selectivity of neurons in area V2. In recording from anesthetized macaques, we estimate that dual selectivity for chromatic and spatiotemporal attributes is 50% more common (27% vs. 18% sampling frequency) in superficial and deep layer neurons receiving feedback connections from higher areas, compared with layer 4-3 neurons relaying ascending signals. The operation of feedback pathways is thought to mediate attentional modulation of activity that may achieve binding through acting to select one single object for higher representation and filtering out competing objects. We propose that dual-selective neurons perform a "bridging" function, mediating the transfer of feedback-induced bias between feature dimensions. The bias can be propagated through V2 output neurons (of unitary selectivity) to higher levels of specialized processing and so promote selection of the target object's representation among multiple feature maps. The bridging function would thus act to unify the outcome of parallel, object-selective processes taking place along segregated visual pathways.

  13. Trainees' Perceptions of Feedback: Validity Evidence for Two FEEDME (Feedback in Medical Education) Instruments.

    Science.gov (United States)

    Bing-You, Robert; Ramesh, Saradha; Hayes, Victoria; Varaklis, Kalli; Ward, Denham; Blanco, Maria

    2017-12-14

    Construct: Medical educators consider feedback a core component of the educational process. Effective feedback allows learners to acquire new skills, knowledge, and attitudes. Learners' perceptions of feedback are an important aspect to assess with valid methods in order to improve the feedback skills of educators and the feedback culture. Although guidelines for delivering effective feedback have existed for several decades, medical students and residents often indicate that they receive little feedback. A recent scoping review on feedback in medical education did not reveal any validity evidence on instruments to assess learner's perceptions of feedback. The purpose of our study was to gather validity evidence on two novel FEEDME (Feedback in Medical Education) instruments to assess medical students' and residents' perceptions of the feedback that they receive. After the authors developed an initial instrument with 54 items, cognitive interviews with medical students and residents suggested that 2 separate instruments were needed, one focused on the feedback culture (FEEDME-Culture) and the other on the provider of feedback (FEEDME-Provider). A Delphi study with 17 medical education experts and faculty members assessed content validity. The response process was explored involving 31 medical students and residents at 2 academic institutions. Exploratory factor analysis and reliability analyses were performed on completed instruments. Two Delphi consultation rounds refined the wording of items and eliminated several items. Learners found both instruments easy and quick to answer; it took them less than 5 minutes to complete. Learners preferred an electronic format of the instruments over paper. Factor analysis revealed a two- and three-factor solution for the FEEDME-Culture and FEEDME-Provider instruments, respectively. Cronbach's alpha was greater than 0.80 for all factors. Items on both instruments were moderately to highly correlated (range, r = .3-.7). Our

  14. DEVELOPING WRITING THROUGH BLOGS AND PEER FEEDBACK

    Directory of Open Access Journals (Sweden)

    Oscar Mauricio Gómez Delgado

    2013-12-01

    Full Text Available Results are presented from a study conducted online with a population of students of an English teacher education program. The study inquired into the role that peer feedback played in the development or maintenance of coherence in non-fictional narrative blog writing. Participant students produced narrative blog entries and peer feedback, which were double-assessed to establish the possible relationship between feedback and coherence. Learner's logs were also kept to obtain second-order data. Findings suggest that peer-feedback and blogging can act as boosting factors to enhance or maintain levels of coherence in text, through the shaping of students' cognition and affection. The potential is revealed of student-centered strategies to enhance learning and foster autonomy through a higher degree of student's control over learning. In addition, it is proposed that new language assessment paradigms be applied in the classroom, acknowledging students as a valid and reliable source of assessment information.

  15. Feedback stabilization of semilinear heat equations

    Directory of Open Access Journals (Sweden)

    V. Barbu

    2003-01-01

    Full Text Available This paper is concerned with the internal and boundary stabilization of the steady-state solutions to quasilinear heat equations via internal linear feedback controllers provided by an LQ control problem associated with the linearized equation.

  16. Final report, Feedback limitations of photosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Sharkey, Thomas D.

    1999-07-22

    Final report of research on carbon metabolism of photosynthesis. The feedback from carbon metabolism to primary photosynthetic processes is summarized, and a comprehensive list of published scientific papers is provided.

  17. Cirrus feedback on interannual climate fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, C; Dessler, A E; Zelinka, M D; Yang, P; Wang, T

    2014-12-28

    Cirrus clouds are not only important in determining the current climate, but also play an important role in climate change and variability. Analysis of satellite observations shows that the amount and altitude of cirrus clouds (optical depth <3.6, cloud top pressure <440 hPa) increase in response to inter-annual surface warming. Thus, cirrus clouds are likely to act as a positive feedback on short-term climate fluctuations, by reducing the planet’s ability to radiate longwave radiation to space in response to planetary surface warming. Using cirrus cloud radiative kernels, the magnitude of cirrus feedback is estimated to be 0.20±0.21W/m2/°C, which is comparable to the surface albedo feedback. Most of the cirrus feedback comes from increasing cloud amount in the tropical tropopause layer (TTL) and subtropical upper troposphere.

  18. Sensory feedback in upper limb prosthetics.

    Science.gov (United States)

    Antfolk, Christian; D'Alonzo, Marco; Rosén, Birgitta; Lundborg, Göran; Sebelius, Fredrik; Cipriani, Christian

    2013-01-01

    One of the challenges facing prosthetic designers and engineers is to restore the missing sensory function inherit to hand amputation. Several different techniques can be employed to provide amputees with sensory feedback: sensory substitution methods where the recorded stimulus is not only transferred to the amputee, but also translated to a different modality (modality-matched feedback), which transfers the stimulus without translation and direct neural stimulation, which interacts directly with peripheral afferent nerves. This paper presents an overview of the principal works and devices employed to provide upper limb amputees with sensory feedback. The focus is on sensory substitution and modality matched feedback; the principal features, advantages and disadvantages of the different methods are presented.

  19. The Greenhouse Effect and Climate Feedbacks

    Science.gov (United States)

    Covey, C.; Haberle, R. M.; McKay, C. P.; Titov, D. V.

    2012-06-01

    We review the theory of the greenhouse effect and climate feedback. We also compare the theory with observations, using examples taken from all four known terrestrial worlds with substantial atmospheres: Venus, Earth, Mars, and Titan.

  20. Adaptive Feedfoward Feedback Control Framework Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An Adaptive Feedforward and Feedback Control (AFFC) Framework is proposed to suppress the aircraft's structural vibrations and to increase the resilience of the...

  1. Equations for studies of feedback stabilization

    International Nuclear Information System (INIS)

    Boozer, A.H.

    1998-01-01

    Important ideal magnetohydrodynamic (MHD) instabilities grow slowly when a conducting wall surrounds a toroidal plasma. Feedback stabilization of these instabilities may be required for tokamaks and other magnetic confinement concepts to achieve adequate plasma pressure and self-driven current for practical fusion power. Equations are derived for simulating feedback stabilization, which require the minimum information about an ideal plasma for an exact analysis. The equations are solved in the approximation of one unstable mode, one wall circuit, one feedback circuit, and one sensor circuit. The analysis based on a single unstable mode is shown to be mathematically equivalent to the standard analysis of feedback of the axisymmetric vertical instability of tokamaks. Unlike that analysis, the method presented here applies to multiple modes that are coupled by the wall and to arbitrary toroidal mode numbers. copyright 1998 American Institute of Physics

  2. Self-Directed Learning with Feedback

    Science.gov (United States)

    Choi, Youngeun; Anderson, William

    2016-01-01

    This article describes a weekly writing assignment named SelFeed (Self-Directed Learning with Feedback), in which students are asked to identify their own questions relevant to the lecture content and provide logical answers.

  3. Online and post-trial feedback differentially affect implicit adaptation to a visuomotor rotation.

    Science.gov (United States)

    Schween, Raphael; Taube, Wolfgang; Gollhofer, Albert; Leukel, Christian

    2014-09-01

    Multiple motor learning processes can be discriminated in visuomotor rotation paradigms. At least four processes have been proposed: Implicit adaptation updates an internal model based on prediction errors. Model-free reinforcement reinforces actions that achieve task success. Use-dependent learning favors repetition of prior movements, and strategic learning uses explicit knowledge about the task. The current experiment tested whether the processes involved in motor learning differ when visual feedback is altered. Specifically, we hypothesized that online and post-trial feedback would cause different amounts of implicit adaptation. Twenty subjects performed drawing movements to targets under a 45° counterclockwise visuomotor rotation while aiming at a clockwise adjacent target. Subjects received visual feedback via a cursor on a screen. One group saw the cursor throughout the movement (online feedback), while the other only saw the final position after movement execution (post-trial feedback). Both groups initially hit the target by applying the strategy. After 80 trials, subjects with online feedback had drifted in clockwise direction [mean direction error: 15.1° (SD 11.2°)], thus overcompensating the rotation. Subjects with post-trial feedback remained accurate [mean: 0.7° (SD 2.0°), TIME × F = 3.926, p = 0.003]. We interpret this overcompensation to reflect implicit adaptation isolated from other mechanisms, because it is driven by prediction error rather than task success (model-free reinforcement) or repetition (use-dependent learning). The current findings extend previous work (e.g., Mazzoni and Krakauer in J Neurosci 26:3642-3645, 2006; Hinder et al. in Exp Brain Res 201:191-207, 2010) and suggest that online feedback promotes more implicit adaptation than does post-trial feedback.

  4. Network interactions underlying mirror feedback in stroke: A dynamic causal modeling study

    Directory of Open Access Journals (Sweden)

    Soha Saleh

    2017-01-01

    Full Text Available Mirror visual feedback (MVF is potentially a powerful tool to facilitate recovery of disordered movement and stimulate activation of under-active brain areas due to stroke. The neural mechanisms underlying MVF have therefore been a focus of recent inquiry. Although it is known that sensorimotor areas can be activated via mirror feedback, the network interactions driving this effect remain unknown. The aim of the current study was to fill this gap by using dynamic causal modeling to test the interactions between regions in the frontal and parietal lobes that may be important for modulating the activation of the ipsilesional motor cortex during mirror visual feedback of unaffected hand movement in stroke patients. Our intent was to distinguish between two theoretical neural mechanisms that might mediate ipsilateral activation in response to mirror-feedback: transfer of information between bilateral motor cortices versus recruitment of regions comprising an action observation network which in turn modulate the motor cortex. In an event-related fMRI design, fourteen chronic stroke subjects performed goal-directed finger flexion movements with their unaffected hand while observing real-time visual feedback of the corresponding (veridical or opposite (mirror hand in virtual reality. Among 30 plausible network models that were tested, the winning model revealed significant mirror feedback-based modulation of the ipsilesional motor cortex arising from the contralesional parietal cortex, in a region along the rostral extent of the intraparietal sulcus. No winning model was identified for the veridical feedback condition. We discuss our findings in the context of supporting the latter hypothesis, that mirror feedback-based activation of motor cortex may be attributed to engagement of a contralateral (contralesional action observation network. These findings may have important implications for identifying putative cortical areas, which may be targeted with

  5. Multivariable Feedback Control of Nuclear Reactors

    Directory of Open Access Journals (Sweden)

    Rune Moen

    1982-07-01

    Full Text Available Multivariable feedback control has been adapted for optimal control of the spatial power distribution in nuclear reactor cores. Two design techniques, based on the theory of automatic control, were developed: the State Variable Feedback (SVF is an application of the linear optimal control theory, and the Multivariable Frequency Response (MFR is based on a generalization of the traditional frequency response approach to control system design.

  6. Formation feedback control of UAV flight

    Science.gov (United States)

    Stegall, Stephen

    This thesis is a study of formation control with autonomous unmanned aerial vehicles using the formation as feedback. There is also an investigation of formation methods presenting insight into different algorithms for formations. A rigid formation is achieved using a proportional-derivative virtual structure with a formation feedback controller. There is an emphasis on stick controlled aerodynamics. The rigid formation is verified by a simulation of a longitudinal model. Formation control ideas are presented for rigid formations.

  7. Numerical Feedback Stabilization with Applications to Networks

    Directory of Open Access Journals (Sweden)

    Simone Göttlich

    2017-01-01

    Full Text Available The focus is on the numerical consideration of feedback boundary control problems for linear systems of conservation laws including source terms. We explain under which conditions the numerical discretization can be used to design feedback boundary values for network applications such as electric transmission lines or traffic flow systems. Several numerical examples illustrate the properties of the results for different types of networks.

  8. Force feedback effects on single molecule hopping and pulling experiments

    Science.gov (United States)

    Rico-Pasto, M.; Pastor, I.; Ritort, F.

    2018-03-01

    Single-molecule experiments with optical tweezers have become an important tool to study the properties and mechanisms of biological systems, such as cells and nucleic acids. In particular, force unzipping experiments have been used to extract the thermodynamics and kinetics of folding and unfolding reactions. In hopping experiments, a molecule executes transitions between the unfolded and folded states at a preset value of the force [constant force mode (CFM) under force feedback] or trap position [passive mode (PM) without feedback] and the force-dependent kinetic rates extracted from the lifetime of each state (CFM) and the rupture force distributions (PM) using the Bell-Evans model. However, hopping experiments in the CFM are known to overestimate molecular distances and folding free energies for fast transitions compared to the response time of the feedback. In contrast, kinetic rate measurements from pulling experiments have been mostly done in the PM while the CFM is seldom implemented in pulling protocols. Here, we carry out hopping and pulling experiments in a short DNA hairpin in the PM and CFM at three different temperatures (6 °C, 25 °C, and 45 °C) exhibiting largely varying kinetic rates. As expected, we find that equilibrium hopping experiments in the CFM and PM perform well at 6 °C (where kinetics are slow), whereas the CFM overestimates molecular parameters at 45 °C (where kinetics are fast). In contrast, nonequilibrium pulling experiments perform well in both modes at all temperatures. This demonstrates that the same kind of feedback algorithm in the CFM leads to more reliable determination of the folding reaction parameters in irreversible pulling experiments.

  9. Basic and supplementary sensory feedback in handwriting

    Directory of Open Access Journals (Sweden)

    Jeremy eDanna

    2015-02-01

    Full Text Available The mastering of handwriting is so essential in our society that it is important to try to find new methods for facilitating its learning and rehabilitation. The ability to control the graphic movements clearly impacts on the quality of the writing. This control allows both the programming of letter formation before movement execution and the online adjustments during execution, thanks to diverse sensory feedback. New technologies improve existing techniques or enable new methods to supply the writer with real-time computer-assisted feedback. The possibilities are numerous and various. Therefore, two main questions arise: 1-What aspect of the movement is concerned and 2- How can we best inform the writer to help them correct their handwriting? In a first step, we report studies on feedback naturally used by the writer. The purpose is to determine which information is carried by each sensory modality, how it is used in handwriting control and how this control changes with practice and learning. In a second step, we report studies on supplementary feedback provided to the writer to help them to better control and learn how to write. We suggest that, depending on their contents, certain sensory modalities will be more appropriate than others to assist handwriting motor control. We emphasize particularly the relevance of auditory modality as online supplementary feedback on handwriting movements. Using real-time supplementary feedback to assist in the handwriting process is probably destined for a brilliant future with the growing availability and rapid development of tablets.

  10. MARTe at FTU: The new feedback control

    Energy Technology Data Exchange (ETDEWEB)

    Boncagni, Luca, E-mail: luca.boncagni@enea.it [EURATOM - ENEA Fusion Association, Frascati Research Centre, Division of Fusion Physics, Rome, Frascati (Italy); Sadeghi, Yahya; Carnevale, Daniele; Di Geronimo, Andrea; Varano, Gianluca; Vitelli, Riccardo [Department of Computer Science, Systems and Production, University of Rome Tor Vergata, Rome (Italy); Galperti, Critsian [Istituto di Fisica del Plasma, CNR, EURATOM-ENEA Association, Milan (Italy); Zarfati, Emanuele; Pucci, Daniele [Department Antonio Ruberti, University of Rome La Sapienza, Rome (Italy)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer We show that the MARTe is a candidate for ITER PSH. Black-Right-Pointing-Pointer We replace the old real-time feedback software using the MARTe framework. Black-Right-Pointing-Pointer We describe all the work done for the integration. - Abstract: Keeping in mind the necessities of a modern control system for fusion devices, such as modularity and a distributed architecture, an upgrade of the present FTU feedback control system was planned, envisaging also a possible reutilization in the proposed FAST experiment [1]. For standardization and efficiency purposes we decided to adopt a pre-existent ITER-relevant framework called MARTe [2], already used with success in other European Tokamak devices [3]. Following the developments shown in [4], in this paper we report on the structure of the new feedback system, and how it was integrated in the current control structure and pulse programming interface, and in the other MARTe systems already in FTU: RT-ODIN [5] and the ECRH and LH [6] satellite stations. The new feedback system has been installed in the FTU backup station (known as 'Feedback B'), which shares the input signals with the actual feedback system, in order to simplify the validation and debug of the new controller by testing it in parallel with the current one. Experimental results are then presented.

  11. Investigation of internal feedback in hearing aids

    DEFF Research Database (Denmark)

    Friis, Lars

    2009-01-01

    There are many aesthetics and structural design requirements to modern hearing aids and their size has been reduced considerably during the last decades. This has led to designs where the receiver (loudspeaker) and microphones are placed closely together. As a consequence, problems with vibroacou......There are many aesthetics and structural design requirements to modern hearing aids and their size has been reduced considerably during the last decades. This has led to designs where the receiver (loudspeaker) and microphones are placed closely together. As a consequence, problems...... with vibroacoustic transmission from the receiver to the microphones often occur during the use of hearing aids. This transmission causes feedback at certain critical gain levels where it produces a loud uncomfortable squealing. Consequently feedback often constitutes the limiting factor for the maximum obtainable...... gain in the hearing aid and it therefore represents a critical design problem. Feedback in hearing aids is usually divided into external and internal feedback. External feedback is caused by the leakage of sound from the ear canal whereas internal feedback is due to transmission of sound and vibrations...

  12. Frequency modulated cutaneous orientation feedback from artificial arms. [dynamic control model of human arm

    Science.gov (United States)

    Solomonow, M.; Freedy, A.; Lyman, J.

    1975-01-01

    A model of the human arm, emphasizing the neuromuscular mechanisms of feedback control, has been constructed. The various parameters and functions of physiological receptors in the feedback section have been classified into an automated category that can be incorporated in the prosthesis servo loop, and into a sensory category that should be communicated to the operator if control and dynamic performance are to be optimized. A scheme for simultaneous display of two such sensory parameters, i.e., fingertip pressure and elbow position, has been developed, implemented and evaluated. The neurophysiological mechanism of such displays, and the feasibility of sensory transformation, is discussed in this paper.

  13. Canard phenomenon and localization of oscillations in the Belousov-Zhabotinsky reaction with global feedback

    Science.gov (United States)

    Rotstein, Horacio G.; Kopell, Nancy; Zhabotinsky, Anatol M.; Epstein, Irving R.

    2003-11-01

    The occurrence of spatial domains of large amplitude oscillation on a background of small amplitude oscillation in a reaction-diffusion system is called localization. We study, analytically and numerically, the mechanism of localization in a model of the Belousov-Zhabotinsky reaction subject to global feedback. This behavior is found to arise from the canard phenomenon, in which a limit cycle suddenly undergoes a significant change in amplitude as a bifurcation parameter, in this case the feedback strength, is varied. In the system studied here, the oscillations arise via a supercritical Hopf bifurcation, but our analysis suggests that the same mechanism is relevant for systems undergoing a subcritical Hopf bifurcation.

  14. Prolactin and Male Fertility: The Long and Short Feedback Regulation

    Directory of Open Access Journals (Sweden)

    M. K. Gill-Sharma

    2009-01-01

    Full Text Available In the last 20 years, a pituitary-hypothalamus tissue culture system with intact neural and portal connections has been developed in our lab and used to understand the feedback mechanisms that regulate the secretions of adenohypophyseal hormones and fertility of male rats. In the last decade, several in vivo rat models have also been developed in our lab with a view to substantiate the in vitro findings, in order to delineate the role of pituitary hormones in the regulation of fertility of male rats. These studies have relied on both surgical and pharmacological interventions to modulate the secretions of gonadotropins and testosterone. The interrelationship between the circadian release of reproductive hormones has also been ascertained in normal men. Our studies suggest that testosterone regulates the secretion of prolactin through a long feedback mechanism, which appears to have been conserved from rats to humans. These studies have filled in a major lacuna pertaining to the role of prolactin in male reproductive physiology by demonstrating the interdependence between testosterone and prolactin. Systemic levels of prolactin play a deterministic role in the mechanism of chromatin condensation during spermiogenesis.

  15. Design of an NLC Intrapulse Feedback System(LCC-0056)

    Energy Technology Data Exchange (ETDEWEB)

    Smith, S.

    2003-12-03

    The small beam spot size at the interaction point of the Next Linear Collider (NLC) makes the luminosity sensitive to beam jitter. A mechanism for aligning the beams to each other which acts during the bunch-train crossing time ({approx}260 ns) has been proposed to maintain luminosity in the presence of beam jitter. Conceptual designs of principal components of the system, a fast position monitor, a kicker,and a feedback regulator are described. Simulation shows that a simple system consisting of fairly conventional components can be effective at reducing the loss of NLC luminosity in the presence of beam jitter many times larger than the vertical beam size.

  16. Microorganisms and climate change: terrestrial feedbacks and mitigation options.

    Science.gov (United States)

    Singh, Brajesh K; Bardgett, Richard D; Smith, Pete; Reay, Dave S

    2010-11-01

    Microbial processes have a central role in the global fluxes of the key biogenic greenhouse gases (carbon dioxide, methane and nitrous oxide) and are likely to respond rapidly to climate change. Whether changes in microbial processes lead to a net positive or negative feedback for greenhouse gas emissions is unclear. To improve the prediction of climate models, it is important to understand the mechanisms by which microorganisms regulate terrestrial greenhouse gas flux. This involves consideration of the complex interactions that occur between microorganisms and other biotic and abiotic factors. The potential to mitigate climate change by reducing greenhouse gas emissions through managing terrestrial microbial processes is a tantalizing prospect for the future.

  17. Feed-Back Regulation of Haemopoiesis

    International Nuclear Information System (INIS)

    Feldman, M.

    1968-01-01

    Studies ate reported on the feed-back regulation of erythropoiesis by means of the intrasplenic cloning system of haemopoietic cells. Polycythaemia, produced by passive transfusion of synzeneic, allogeneic or xenogeneic red blood cells, inhibited the formation of bone-marrow derived erythroid clones. Polycythaemia also inhibited the formation of erythroid clones of endogenous stem cells. Oxygen overloading was found to be a necessary factor in the suppression of erythroid clone formation: no suppression of erythroid colonies was observed when polycythaemic animals were kept under hypoxic conditions. Erythropoietin, either of exogenous or of endogenous origin, elicited a reformation of erythroid clones in 'suppressed' animals. Studies on the kinetics of reformation of erythroid clones after the administration of erythropoietin suggested that the colony-forming stem cell can replicate a few times in the absence of erythropoietin and the cell progeny thus formed are the target cells for erythropoietin action. If, indeed, the colony-forming cell replicates in the absence of the specific inducer, then the cells thus formed should themselves be stem cells. This was substantiated by demonstrating that the cloning efficiency of spleens of polycythaemic recipients was higher than that of non-polycythaemic animals. Experiments indicating that erythroid clones produced by erythropoietin in polycythaemic animals disappeared after the discontinuance of erythropoietin application demonstrated the distinction between the 'mitogenic' and the 'morphogenetic' effects of erythropoietin. The latter seemed to be operated by an early transcription of RNA for proteins necessary for the complete maturation of the red blood cell, Erythroid clones produced by foetal haemopoietic stem cells seemed to be regulated by a different mechanism from that which controls the formation of bone-marrow derived clones. Clones produced by foetal cells were only partially suppressed in the polycythaemic

  18. The Neural Feedback Response to Error As a Teaching Signal for the Motor Learning System

    Science.gov (United States)

    Shadmehr, Reza

    2016-01-01

    When we experience an error during a movement, we update our motor commands to partially correct for this error on the next trial. How does experience of error produce the improvement in the subsequent motor commands? During the course of an erroneous reaching movement, proprioceptive and visual sensory pathways not only sense the error, but also engage feedback mechanisms, resulting in corrective motor responses that continue until the hand arrives at its goal. One possibility is that this feedback response is co-opted by the learning system and used as a template to improve performance on the next attempt. Here we used electromyography (EMG) to compare neural correlates of learning and feedback to test the hypothesis that the feedback response to error acts as a template for learning. We designed a task in which mixtures of error-clamp and force-field perturbation trials were used to deconstruct EMG time courses into error-feedback and learning components. We observed that the error-feedback response was composed of excitation of some muscles, and inhibition of others, producing a complex activation/deactivation pattern during the reach. Despite this complexity, across muscles the learning response was consistently a scaled version of the error-feedback response, but shifted 125 ms earlier in time. Across people, individuals who produced a greater feedback response to error, also learned more from error. This suggests that the feedback response to error serves as a teaching signal for the brain. Individuals who learn faster have a better teacher in their feedback control system. SIGNIFICANCE STATEMENT Our sensory organs transduce errors in behavior. To improve performance, we must generate better motor commands. How does the nervous system transform an error in sensory coordinates into better motor commands in muscle coordinates? Here we show that when an error occurs during a movement, the reflexes transform the sensory representation of error into motor

  19. Controlling chaos with time-delay feedback

    Science.gov (United States)

    Bleich, Michael Edward

    We investigate the application of time-delay feedback to stabilize periodic orbits that are unstable in the absence of control. The control schemes that we consider use feedback that becomes small as the desired controlled state is produced, and actually vanishes in the absence of noise. Time-delay feedback schemes are of interest because they do not require knowledge of the controlled orbit, are applicable to the control of very fast systems, and can be produced with an all-optical technique--the feedback signal is the reflected field of a Fabry-Perot interferometer with appropriate choices of the cavity length and reflectivities of the end mirrors. A linear stability analysis is developed for orbits controlled with time-delay feedback, and used, in addition to numerical simulations, to explore the properties of controlled systems. In particular, we determine which choices of the control parameters, including the feedback gain, that lead to successful control. Three systems are investigated in detail: (1) the driven nonlinear pendulum, a familiar example of a system with only a few degrees of freedom; (2) the complex Ginzburg-Landau equation, an amplitude equation for the spatiotemporal dynamics near a generic instability; and (3) a Swift-Hohenberg type model for the spatio-temporal dynamics of a broad-area semiconductor laser. In the latter two systems we show that unstable traveling wave states can be stabilized by the application of time-delay control, even though in the absence of control these states are unstable to a continuous band of perturbations. Since the feedback can in principle be generated with an all-optical technique, our results indicate that it may be possible to produce controlled high-power coherent states in wide-area semiconductor lasers, a result with important technological ramifications.

  20. Altered Sensory Feedbacks in Pianist's Dystonia: the altered auditory feedback paradigm and the glove effect

    Directory of Open Access Journals (Sweden)

    Felicia Pei-Hsin Cheng

    2013-12-01

    Full Text Available Background: This study investigates the effect of altered auditory feedback (AAF in musician's dystonia (MD and discusses whether altered auditory feedback can be considered as a sensory trick in MD. Furthermore, the effect of AAF is compared with altered tactile feedback, which can serve as a sensory trick in several other forms of focal dystonia. Methods: The method is based on scale analysis (Jabusch et al. 2004. Experiment 1 employs synchronization paradigm: 12 MD patients and 25 healthy pianists had to repeatedly play C-major scales in synchrony with a metronome on a MIDI-piano with 3 auditory feedback conditions: 1. normal feedback; 2. no feedback; 3. constant delayed feedback. Experiment 2 employs synchronization-continuation paradigm: 12 MD patients and 12 healthy pianists had to repeatedly play C-major scales in two phases: first in synchrony with a metronome, secondly continue the established tempo without the metronome. There are 4 experimental conditions, among them 3 are the same altered auditory feedback as in Experiment 1 and 1 is related to altered tactile sensory input. The coefficient of variation of inter-onset intervals of the key depressions was calculated to evaluate fine motor control. Results: In both experiments, the healthy controls and the patients behaved very similarly. There is no difference in the regularity of playing between the two groups under any condition, and neither did AAF nor did altered tactile feedback have a beneficial effect on patients’ fine motor control. Conclusions: The results of the two experiments suggest that in the context of our experimental designs, AAF and altered tactile feedback play a minor role in motor coordination in patients with musicians' dystonia. We propose that altered auditory and tactile feedback do not serve as effective sensory tricks and may not temporarily reduce the symptoms of patients suffering from MD in this experimental context.