Distributed Adaptive Neural Network Output Tracking of Leader-Following High-Order Stochastic Nonlinear Multiagent Systems With Unknown Dead-Zone Input.

PubMed

Hua, Changchun; Zhang, Liuliu; Guan, Xinping

2017-01-01

This paper studies the problem of distributed output tracking consensus control for a class of high-order stochastic nonlinear multiagent systems with unknown nonlinear dead-zone under a directed graph topology. The adaptive neural networks are used to approximate the unknown nonlinear functions and a new inequality is used to deal with the completely unknown dead-zone input. Then, we design the controllers based on backstepping method and the dynamic surface control technique. It is strictly proved that the resulting closed-loop system is stable in probability in the sense of semiglobally uniform ultimate boundedness and the tracking errors between the leader and the followers approach to a small residual set based on Lyapunov stability theory. Finally, two simulation examples are presented to show the effectiveness and the advantages of the proposed techniques.

Control of Complex Dynamic Systems by Neural Networks

NASA Technical Reports Server (NTRS)

Spall, James C.; Cristion, John A.

1993-01-01

This paper considers the use of neural networks (NN's) in controlling a nonlinear, stochastic system with unknown process equations. The NN is used to model the resulting unknown control law. The approach here is based on using the output error of the system to train the NN controller without the need to construct a separate model (NN or other type) for the unknown process dynamics. To implement such a direct adaptive control approach, it is required that connection weights in the NN be estimated while the system is being controlled. As a result of the feedback of the unknown process dynamics, however, it is not possible to determine the gradient of the loss function for use in standard (back-propagation-type) weight estimation algorithms. Therefore, this paper considers the use of a new stochastic approximation algorithm for this weight estimation, which is based on a 'simultaneous perturbation' gradient approximation that only requires the system output error. It is shown that this algorithm can greatly enhance the efficiency over more standard stochastic approximation algorithms based on finite-difference gradient approximations.

Decentralized adaptive control of interconnected nonlinear systems with unknown control directions.

PubMed

Huang, Jiangshuai; Wang, Qing-Guo

2018-03-01

In this paper, we propose a decentralized adaptive control scheme for a class of interconnected strict-feedback nonlinear systems without a priori knowledge of subsystems' control directions. To address this problem, a novel Nussbaum-type function is proposed and a key theorem is drawn which involves quantifying the interconnections of multiple Nussbaum-type functions of the subsystems with different control directions in a single inequality. Global stability of the closed-loop system and asymptotic stabilization of subsystems' output are proved and a simulation example is given to illustrate the effectiveness of the proposed control scheme. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Power maximization of variable-speed variable-pitch wind turbines using passive adaptive neural fault tolerant control

NASA Astrophysics Data System (ADS)

Habibi, Hamed; Rahimi Nohooji, Hamed; Howard, Ian

2017-09-01

Power maximization has always been a practical consideration in wind turbines. The question of how to address optimal power capture, especially when the system dynamics are nonlinear and the actuators are subject to unknown faults, is significant. This paper studies the control methodology for variable-speed variable-pitch wind turbines including the effects of uncertain nonlinear dynamics, system fault uncertainties, and unknown external disturbances. The nonlinear model of the wind turbine is presented, and the problem of maximizing extracted energy is formulated by designing the optimal desired states. With the known system, a model-based nonlinear controller is designed; then, to handle uncertainties, the unknown nonlinearities of the wind turbine are estimated by utilizing radial basis function neural networks. The adaptive neural fault tolerant control is designed passively to be robust on model uncertainties, disturbances including wind speed and model noises, and completely unknown actuator faults including generator torque and pitch actuator torque. The Lyapunov direct method is employed to prove that the closed-loop system is uniformly bounded. Simulation studies are performed to verify the effectiveness of the proposed method.

Distributed adaptive asymptotically consensus tracking control of uncertain Euler-Lagrange systems under directed graph condition.

PubMed

Wang, Wei; Wen, Changyun; Huang, Jiangshuai; Fan, Huijin

2017-11-01

In this paper, a backstepping based distributed adaptive control scheme is proposed for multiple uncertain Euler-Lagrange systems under directed graph condition. The common desired trajectory is allowed totally unknown by part of the subsystems and the linearly parameterized trajectory model assumed in currently available results is no longer needed. To compensate the effects due to unknown trajectory information, a smooth function of consensus errors and certain positive integrable functions are introduced in designing virtual control inputs. Besides, to overcome the difficulty of completely counteracting the coupling terms of distributed consensus errors and parameter estimation errors in the presence of asymmetric Laplacian matrix, extra information transmission of local parameter estimates are introduced among linked subsystem and adaptive gain technique is adopted to generate distributed torque inputs. It is shown that with the proposed distributed adaptive control scheme, global uniform boundedness of all the closed-loop signals and asymptotically output consensus tracking can be achieved. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Terminal Sliding Mode-Based Consensus Tracking Control for Networked Uncertain Mechanical Systems on Digraphs.

PubMed

Chen, Gang; Song, Yongduan; Guan, Yanfeng

2018-03-01

This brief investigates the finite-time consensus tracking control problem for networked uncertain mechanical systems on digraphs. A new terminal sliding-mode-based cooperative control scheme is developed to guarantee that the tracking errors converge to an arbitrarily small bound around zero in finite time. All the networked systems can have different dynamics and all the dynamics are unknown. A neural network is used at each node to approximate the local unknown dynamics. The control schemes are implemented in a fully distributed manner. The proposed control method eliminates some limitations in the existing terminal sliding-mode-based consensus control methods and extends the existing analysis methods to the case of directed graphs. Simulation results on networked robot manipulators are provided to show the effectiveness of the proposed control algorithms.

Reinforcement learning for adaptive optimal control of unknown continuous-time nonlinear systems with input constraints

NASA Astrophysics Data System (ADS)

Yang, Xiong; Liu, Derong; Wang, Ding

2014-03-01

In this paper, an adaptive reinforcement learning-based solution is developed for the infinite-horizon optimal control problem of constrained-input continuous-time nonlinear systems in the presence of nonlinearities with unknown structures. Two different types of neural networks (NNs) are employed to approximate the Hamilton-Jacobi-Bellman equation. That is, an recurrent NN is constructed to identify the unknown dynamical system, and two feedforward NNs are used as the actor and the critic to approximate the optimal control and the optimal cost, respectively. Based on this framework, the action NN and the critic NN are tuned simultaneously, without the requirement for the knowledge of system drift dynamics. Moreover, by using Lyapunov's direct method, the weights of the action NN and the critic NN are guaranteed to be uniformly ultimately bounded, while keeping the closed-loop system stable. To demonstrate the effectiveness of the present approach, simulation results are illustrated.

Self-Controlled Amount of Practice Benefits Learning of a Motor Skill

ERIC Educational Resources Information Center

Post, Phillip G.; Fairbrother, Jeffrey T.; Barros, Joao A. C.

2011-01-01

Self-control over factors involving task-related information (e.g., feedback) can enhance motor learning. It is unknown if these benefits extend to manipulations that do not directly affect such information. The purpose of this study was to determine if self-control over the amount of practice would also facilitate learning. Participants learned…

Adaptive Control in the Presence of Simultaneous Sensor Bias and Actuator Failures

NASA Technical Reports Server (NTRS)

Joshi, Suresh M.

2012-01-01

The problem of simultaneously accommodating unknown sensor biases and unknown actuator failures in uncertain systems is considered in a direct model reference adaptive control (MRAC) setting for state tracking using state feedback. Sensor biases and actuator faults may be present at the outset or may occur at unknown instants of time during operation. A modified MRAC law is proposed, which combines sensor bias estimation with control gain adaptation for accommodation of sensor biases and actuator failures. This control law is shown to provide signal boundedness in the resulting system. For the case when an external asymptotically stable sensor bias estimator is available, an MRAC law is developed to accomplish asymptotic state tracking and signal boundedness. For a special case wherein biases are only present in the rate measurements and bias-free position measurements are available, an MRAC law is developed using a model-independent bias estimator, and is shown to provide asymptotic state tracking with signal boundedness.

Adaptive neural network output feedback control for stochastic nonlinear systems with unknown dead-zone and unmodeled dynamics.

PubMed

Tong, Shaocheng; Wang, Tong; Li, Yongming; Zhang, Huaguang

2014-06-01

This paper discusses the problem of adaptive neural network output feedback control for a class of stochastic nonlinear strict-feedback systems. The concerned systems have certain characteristics, such as unknown nonlinear uncertainties, unknown dead-zones, unmodeled dynamics and without the direct measurements of state variables. In this paper, the neural networks (NNs) are employed to approximate the unknown nonlinear uncertainties, and then by representing the dead-zone as a time-varying system with a bounded disturbance. An NN state observer is designed to estimate the unmeasured states. Based on both backstepping design technique and a stochastic small-gain theorem, a robust adaptive NN output feedback control scheme is developed. It is proved that all the variables involved in the closed-loop system are input-state-practically stable in probability, and also have robustness to the unmodeled dynamics. Meanwhile, the observer errors and the output of the system can be regulated to a small neighborhood of the origin by selecting appropriate design parameters. Simulation examples are also provided to illustrate the effectiveness of the proposed approach.

Distributed Synchronization Control of Multiagent Systems With Unknown Nonlinearities.

PubMed

Su, Shize; Lin, Zongli; Garcia, Alfredo

2016-01-01

This paper revisits the distributed adaptive control problem for synchronization of multiagent systems where the dynamics of the agents are nonlinear, nonidentical, unknown, and subject to external disturbances. Two communication topologies, represented, respectively, by a fixed strongly-connected directed graph and by a switching connected undirected graph, are considered. Under both of these communication topologies, we use distributed neural networks to approximate the uncertain dynamics. Decentralized adaptive control protocols are then constructed to solve the cooperative tracker problem, the problem of synchronization of all follower agents to a leader agent. In particular, we show that, under the proposed decentralized control protocols, the synchronization errors are ultimately bounded, and their ultimate bounds can be reduced arbitrarily by choosing the control parameter appropriately. Simulation study verifies the effectiveness of our proposed protocols.

Integrated direct/indirect adaptive robust motion trajectory tracking control of pneumatic cylinders

NASA Astrophysics Data System (ADS)

Meng, Deyuan; Tao, Guoliang; Zhu, Xiaocong

2013-09-01

This paper studies the precision motion trajectory tracking control of a pneumatic cylinder driven by a proportional-directional control valve. An integrated direct/indirect adaptive robust controller is proposed. The controller employs a physical model based indirect-type parameter estimation to obtain reliable estimates of unknown model parameters, and utilises a robust control method with dynamic compensation type fast adaptation to attenuate the effects of parameter estimation errors, unmodelled dynamics and disturbances. Due to the use of projection mapping, the robust control law and the parameter adaption algorithm can be designed separately. Since the system model uncertainties are unmatched, the recursive backstepping technology is adopted to design the robust control law. Extensive comparative experimental results are presented to illustrate the effectiveness of the proposed controller and its performance robustness to parameter variations and sudden disturbances.

Adaptive sliding control of non-autonomous active suspension systems with time-varying loadings

NASA Astrophysics Data System (ADS)

Chen, Po-Chang; Huang, An-Chyau

2005-04-01

An adaptive sliding controller is proposed in this paper for controlling a non-autonomous quarter-car suspension system with time-varying loadings. The bound of the car-body loading is assumed to be available. Then, the reference coordinate is placed at the static position under the nominal loading so that the system dynamic equation is derived. Due to spring nonlinearities, the system property becomes asymmetric after coordinate transformation. Besides, in practical cases, system parameters are not easy to be obtained precisely for controller design. Therefore, in this paper, system uncertainties are lumped into two unknown time-varying functions. Since the variation bound of one of the unknown functions is not available, conventional adaptive schemes and robust designs are not applicable. To deal with this problem, the function approximation technique is employed to represent the unknown function as a finite combination of basis functions. The Lyapunov direct method can thus be used to find adaptive laws for updating coefficients in the approximating series and to prove stability of the closed-loop system. Since the position and velocity measurements of the unsprung mass are lumped into the unknown function, there is no need to install sensors on the axle and wheel assembly in the actual implementation. Simulation results are presented to show the performance of the proposed strategy.

Tracking problem for electromechanical system under influence of external perturbations

NASA Astrophysics Data System (ADS)

Kochetkov, Sergey A.; Krasnova, Svetlana A.; Utkin, Victor A.

2017-01-01

For electromechanical objects the new control algorithms (vortex algprithms) are developed on the base of discontinuous functions. The distinctive feature of these algorithms is providing of asymptotical convergence of the output variables to zero under influence of unknown bounded disturbances of prescribed class. The advantages of proposed approach is demonstrated for direct current motor with permanent excitation. It is shown that inner variables of the system converge to unknown bounded disturbances and guarantee asymptotical convergence of output variables to zero.

Adaptive control of bivalirudin in the cardiac intensive care unit.

PubMed

Zhao, Qi; Edrich, Thomas; Paschalidis, Ioannis Ch

2015-02-01

Bivalirudin is a direct thrombin inhibitor used in the cardiac intensive care unit when heparin is contraindicated due to heparin-induced thrombocytopenia. Since it is not a commonly used drug, clinical experience with its dosing is sparse. In earlier work [1], we developed a dynamic system model that accurately predicts the effect of bivalirudin given dosage over time and patient physiological characteristics. This paper develops adaptive dosage controllers that regulate its effect to desired levels. To that end, and in the case that bivalirudin model parameters are available, we develop a Model Reference Control law. In the case that model parameters are unknown, an indirect Model Reference Adaptive Control scheme is applied to estimate model parameters first and then adapt the controller. Alternatively, direct Model Reference Adaptive Control is applied to adapt the controller directly without estimating model parameters first. Our algorithms are validated using actual patient data from a large hospital in the Boston area.

Decentralized adaptive control

NASA Technical Reports Server (NTRS)

Oh, B. J.; Jamshidi, M.; Seraji, H.

1988-01-01

A decentralized adaptive control is proposed to stabilize and track the nonlinear, interconnected subsystems with unknown parameters. The adaptation of the controller gain is derived by using model reference adaptive control theory based on Lyapunov's direct method. The adaptive gains consist of sigma, proportional, and integral combination of the measured and reference values of the corresponding subsystem. The proposed control is applied to the joint control of a two-link robot manipulator, and the performance in computer simulation corresponds with what is expected in theoretical development.

Nonlinear adaptive control system design with asymptotically stable parameter estimation error

NASA Astrophysics Data System (ADS)

Mishkov, Rumen; Darmonski, Stanislav

2018-01-01

The paper presents a new general method for nonlinear adaptive system design with asymptotic stability of the parameter estimation error. The advantages of the approach include asymptotic unknown parameter estimation without persistent excitation and capability to directly control the estimates transient response time. The method proposed modifies the basic parameter estimation dynamics designed via a known nonlinear adaptive control approach. The modification is based on the generalised prediction error, a priori constraints with a hierarchical parameter projection algorithm, and the stable data accumulation concepts. The data accumulation principle is the main tool for achieving asymptotic unknown parameter estimation. It relies on the parametric identifiability system property introduced. Necessary and sufficient conditions for exponential stability of the data accumulation dynamics are derived. The approach is applied in a nonlinear adaptive speed tracking vector control of a three-phase induction motor.

Distributed Adaptive Neural Control for Stochastic Nonlinear Multiagent Systems.

PubMed

Wang, Fang; Chen, Bing; Lin, Chong; Li, Xuehua

2016-11-14

In this paper, a consensus tracking problem of nonlinear multiagent systems is investigated under a directed communication topology. All the followers are modeled by stochastic nonlinear systems in nonstrict feedback form, where nonlinearities and stochastic disturbance terms are totally unknown. Based on the structural characteristic of neural networks (in Lemma 4), a novel distributed adaptive neural control scheme is put forward. The raised control method not only effectively handles unknown nonlinearities in nonstrict feedback systems, but also copes with the interactions among agents and coupling terms. Based on the stochastic Lyapunov functional method, it is indicated that all the signals of the closed-loop system are bounded in probability and all followers' outputs are convergent to a neighborhood of the output of leader. At last, the efficiency of the control method is testified by a numerical example.

A modified NARMAX model-based self-tuner with fault tolerance for unknown nonlinear stochastic hybrid systems with an input-output direct feed-through term.

PubMed

Tsai, Jason S-H; Hsu, Wen-Teng; Lin, Long-Guei; Guo, Shu-Mei; Tann, Joseph W

2014-01-01

A modified nonlinear autoregressive moving average with exogenous inputs (NARMAX) model-based state-space self-tuner with fault tolerance is proposed in this paper for the unknown nonlinear stochastic hybrid system with a direct transmission matrix from input to output. Through the off-line observer/Kalman filter identification method, one has a good initial guess of modified NARMAX model to reduce the on-line system identification process time. Then, based on the modified NARMAX-based system identification, a corresponding adaptive digital control scheme is presented for the unknown continuous-time nonlinear system, with an input-output direct transmission term, which also has measurement and system noises and inaccessible system states. Besides, an effective state space self-turner with fault tolerance scheme is presented for the unknown multivariable stochastic system. A quantitative criterion is suggested by comparing the innovation process error estimated by the Kalman filter estimation algorithm, so that a weighting matrix resetting technique by adjusting and resetting the covariance matrices of parameter estimate obtained by the Kalman filter estimation algorithm is utilized to achieve the parameter estimation for faulty system recovery. Consequently, the proposed method can effectively cope with partially abrupt and/or gradual system faults and input failures by the fault detection. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

Echolalic responses by a child with autism to four experimental conditions of sociolinguistic input.

PubMed

Violette, J; Swisher, L

1992-02-01

Studies of the immediate verbal imitations (IVIs) of subjects with echolalia report that features of linguistic or social input alone affect the number of IVIs elicited. This experimental study of a child with echolalia and autism controlled each of these variables while introducing a systematic change in the other. The subject produced more (p less than .05) IVIs in response to unknown lexical words presented with a high degree of directiveness (Condition D) than in response to three other conditions of stimulus presentation (e.g., unknown lexical words, minimally directive style.) Thus, an interaction between the effects of linguistic and social input was demonstrated. IVIs were produced across all conditions, primarily during first presentations of lexical stimuli. Only the IVIs elicited by first presentations of the lexical stimuli during Condition D differed significantly (p less than .05) from the number of IVIs elicited by first presentations of lexical stimuli in other conditions. These findings viewed together suggest that the occurrence of IVIs was related, at least for this child, to an uncertain or informative event and that this response was significantly greater when the lexical stimuli were unknown and presented in a highly directive style.

Natural Language Direction Following for Robots in Unstructured Unknown Environments

DTIC Science & Technology

2015-01-15

Looking back, I can safely say my most fruitful research was the result of these collaborations. Seeing peers learn and struggle alongside me has been...performance gains on such diverse problems as autonomous driving, playing Super Mario, handwriting recogni- tion, helicopter control, and image...similarity metric between what the direction says and what the robot sees. These are useful to describe the landmark field of the Spatial Description

Nonlinear adaptive formation control for a class of autonomous holonomic planetary exploration rovers

NASA Astrophysics Data System (ADS)

Ganji, Farid

This dissertation presents novel nonlinear adaptive formation controllers for a heterogeneous group of holonomic planetary exploration rovers navigating over flat terrains with unknown soil types and surface conditions. A leader-follower formation control architecture is employed. In the first part, using a point-mass model for robots and a Coulomb-viscous friction model for terrain resistance, direct adaptive control laws and a formation speed-adaptation strategy are developed for formation navigation over unknown and changing terrain in the presence of actuator saturation. On-line estimates of terrain frictional parameters compensate for unknown terrain resistance and its variations. In saturation events over difficult terrain, the formation speed is reduced based on the speed of the slowest saturated robot, using internal fleet communication and a speed-adaptation strategy, so that the formation error stays bounded and small. A formal proof for asymptotic stability of the formation system in non-saturated conditions is given. The performance of robot controllers are verified using a modular 3-robot formation simulator. Simulations show that the formation errors reduce to zero asymptotically under non-saturated conditions as is guaranteed by the theoretical proof. In the second part, the proposed adaptive control methodology is extended for formation control of a class of omnidirectional rovers with three independently-driven universal holonomic rigid wheels, where the rovers' rigid-body dynamics, drive-system electromechanical characteristics, and wheel-ground interaction mechanics are incorporated. Holonomic rovers have the ability to move simultaneously and independently in translation and rotation, rendering great maneuverability and agility, which makes them suitable for formation navigation. Novel nonlinear adaptive control laws are designed for the input voltages of the three wheel-drive motors. The motion resistance, which is due to the sinkage of rover wheels in soft planetary terrain, is modeled using classical terramechanics theory. The unknown system parameters for adaptive estimation pertain to the rolling resistance forces and scrubbing resistance torques at the wheel-terrain interfaces. Novel terramechanical formulas for terrain resistance forces and torques are derived via considering the universal holonomic wheels as rigid toroidal wheels moving forward and/or sideways as well as turning on soft ground. The asymptotic stability of the formation control system is rigorously proved using Lyapunov's direct method.

Synchronization of coupled different chaotic FitzHugh-Nagumo neurons with unknown parameters under communication-direction-dependent coupling.

PubMed

Iqbal, Muhammad; Rehan, Muhammad; Khaliq, Abdul; Saeed-ur-Rehman; Hong, Keum-Shik

2014-01-01

This paper investigates the chaotic behavior and synchronization of two different coupled chaotic FitzHugh-Nagumo (FHN) neurons with unknown parameters under external electrical stimulation (EES). The coupled FHN neurons of different parameters admit unidirectional and bidirectional gap junctions in the medium between them. Dynamical properties, such as the increase in synchronization error as a consequence of the deviation of neuronal parameters for unlike neurons, the effect of difference in coupling strengths caused by the unidirectional gap junctions, and the impact of large time-delay due to separation of neurons, are studied in exploring the behavior of the coupled system. A novel integral-based nonlinear adaptive control scheme, to cope with the infeasibility of the recovery variable, for synchronization of two coupled delayed chaotic FHN neurons of different and unknown parameters under uncertain EES is derived. Further, to guarantee robust synchronization of different neurons against disturbances, the proposed control methodology is modified to achieve the uniformly ultimately bounded synchronization. The parametric estimation errors can be reduced by selecting suitable control parameters. The effectiveness of the proposed control scheme is illustrated via numerical simulations.

Quantum key distribution with an unknown and untrusted source

NASA Astrophysics Data System (ADS)

Zhao, Yi; Qi, Bing; Lo, Hoi-Kwong

2008-05-01

The security of a standard bidirectional “plug-and-play” quantum key distribution (QKD) system has been an open question for a long time. This is mainly because its source is equivalently controlled by an eavesdropper, which means the source is unknown and untrusted. Qualitative discussion on this subject has been made previously. In this paper, we solve this question directly by presenting the quantitative security analysis on a general class of QKD protocols whose sources are unknown and untrusted. The securities of standard Bennett-Brassard 1984 protocol, weak+vacuum decoy state protocol, and one-decoy state protocol, with unknown and untrusted sources are rigorously proved. We derive rigorous lower bounds to the secure key generation rates of the above three protocols. Our numerical simulation results show that QKD with an untrusted source gives a key generation rate that is close to that with a trusted source.

Effects of Trait Self-Control on Response Conflict About Healthy and Unhealthy Food.

PubMed

Gillebaart, Marleen; Schneider, Iris K; De Ridder, Denise T D

2016-12-01

Self-control leads to positive life outcomes, but it is poorly understood. While previous research has focused on self-control failure, self-control success remains unexplored. The current studies aim to shed more light on the mechanisms of self-control by focusing on the resolution of response conflict as a key component in self-control success. Trait self-control was measured, and participants reported on the magnitude of response conflict they experienced about healthy and unhealthy foods in Study 1 (N = 146; M age  = 33.03; 59 females, 83 males, 4 unknown). The response conflict process was assessed in Study 2 (N = 118; M age  = 21.45; 68 females, 41 males, 9 unknown). Outcomes showed that self-reported evaluative response conflict about food items was smaller for people high in trait self-control. Study 2 revealed that higher trait self-control predicted faster resolution of self-control conflict, and an earlier peak of the response conflict. Taken together, these results provide insight into what makes people with high trait self-control successful, namely, how they handle response conflict. Implications for self-control theories and future directions are discussed. © 2015 Wiley Periodicals, Inc.

Differential flatness properties and adaptive control of the hypothalamic-pituitary-adrenal axis model

NASA Astrophysics Data System (ADS)

Rigatos, Gerasimos

2016-12-01

It is shown that the model of the hypothalamic-pituitary-adrenal gland axis is a differentially flat one and this permits to transform it to the so-called linear canonical form. For the new description of the system's dynamics the transformed control inputs contain unknown terms which depend on the system's parameters. To identify these terms an adaptive fuzzy approximator is used in the control loop. Thus an adaptive fuzzy control scheme is implemented in which the unknown or unmodeled system dynamics is approximated by neurofuzzy networks and next this information is used by a feedback controller that makes the state variables (CRH - corticotropin releasing hormone, adenocortocotropic hormone - ACTH, cortisol) of the hypothalamic-pituitary-adrenal gland axis model converge to the desirable levels (setpoints). This adaptive control scheme is exclusively implemented with the use of output feedback, while the state vector elements which are not directly measured are estimated with the use of a state observer that operates in the control loop. The learning rate of the adaptive fuzzy system is suitably computed from Lyapunov analysis, so as to assure that both the learning procedure for the unknown system's parameters, the dynamics of the observer and the dynamics of the control loop will remain stable. The performed Lyapunov stability analysis depends on two Riccati equations, one associated with the feedback controller and one associated with the state observer. Finally, it is proven that for the control scheme that comprises the feedback controller, the state observer and the neurofuzzy approximator, an H-infinity tracking performance can be succeeded.

Aircraft Engine Thrust Estimator Design Based on GSA-LSSVM

NASA Astrophysics Data System (ADS)

Sheng, Hanlin; Zhang, Tianhong

2017-08-01

In view of the necessity of highly precise and reliable thrust estimator to achieve direct thrust control of aircraft engine, based on support vector regression (SVR), as well as least square support vector machine (LSSVM) and a new optimization algorithm - gravitational search algorithm (GSA), by performing integrated modelling and parameter optimization, a GSA-LSSVM-based thrust estimator design solution is proposed. The results show that compared to particle swarm optimization (PSO) algorithm, GSA can find unknown optimization parameter better and enables the model developed with better prediction and generalization ability. The model can better predict aircraft engine thrust and thus fulfills the need of direct thrust control of aircraft engine.

Robust Neighboring Optimal Guidance for the Advanced Launch System

NASA Technical Reports Server (NTRS)

Hull, David G.

1993-01-01

In recent years, optimization has become an engineering tool through the availability of numerous successful nonlinear programming codes. Optimal control problems are converted into parameter optimization (nonlinear programming) problems by assuming the control to be piecewise linear, making the unknowns the nodes or junction points of the linear control segments. Once the optimal piecewise linear control (suboptimal) control is known, a guidance law for operating near the suboptimal path is the neighboring optimal piecewise linear control (neighboring suboptimal control). Research conducted under this grant has been directed toward the investigation of neighboring suboptimal control as a guidance scheme for an advanced launch system.

Quantum key distribution with an unknown and untrusted source

NASA Astrophysics Data System (ADS)

Zhao, Yi; Qi, Bing; Lo, Hoi-Kwong

2009-03-01

The security of a standard bi-directional ``plug & play'' quantum key distribution (QKD) system has been an open question for a long time. This is mainly because its source is equivalently controlled by an eavesdropper, which means the source is unknown and untrusted. Qualitative discussion on this subject has been made previously. In this paper, we present the first quantitative security analysis on a general class of QKD protocols whose sources are unknown and untrusted. The securities of standard BB84 protocol, weak+vacuum decoy state protocol, and one-decoy decoy state protocol, with unknown and untrusted sources are rigorously proved. We derive rigorous lower bounds to the secure key generation rates of the above three protocols. Our numerical simulation results show that QKD with an untrusted source gives a key generation rate that is close to that with a trusted source. Our work is published in [1]. [4pt] [1] Y. Zhao, B. Qi, and H.-K. Lo, Phys. Rev. A, 77:052327 (2008).

Locally optimal control under unknown dynamics with learnt cost function: application to industrial robot positioning

NASA Astrophysics Data System (ADS)

Guérin, Joris; Gibaru, Olivier; Thiery, Stéphane; Nyiri, Eric

2017-01-01

Recent methods of Reinforcement Learning have enabled to solve difficult, high dimensional, robotic tasks under unknown dynamics using iterative Linear Quadratic Gaussian control theory. These algorithms are based on building a local time-varying linear model of the dynamics from data gathered through interaction with the environment. In such tasks, the cost function is often expressed directly in terms of the state and control variables so that it can be locally quadratized to run the algorithm. If the cost is expressed in terms of other variables, a model is required to compute the cost function from the variables manipulated. We propose a method to learn the cost function directly from the data, in the same way as for the dynamics. This way, the cost function can be defined in terms of any measurable quantity and thus can be chosen more appropriately for the task to be carried out. With our method, any sensor information can be used to design the cost function. We demonstrate the efficiency of this method through simulating, with the V-REP software, the learning of a Cartesian positioning task on several industrial robots with different characteristics. The robots are controlled in joint space and no model is provided a priori. Our results are compared with another model free technique, consisting in writing the cost function as a state variable.

Indirect iterative learning control for a discrete visual servo without a camera-robot model.

PubMed

Jiang, Ping; Bamforth, Leon C A; Feng, Zuren; Baruch, John E F; Chen, YangQuan

2007-08-01

This paper presents a discrete learning controller for vision-guided robot trajectory imitation with no prior knowledge of the camera-robot model. A teacher demonstrates a desired movement in front of a camera, and then, the robot is tasked to replay it by repetitive tracking. The imitation procedure is considered as a discrete tracking control problem in the image plane, with an unknown and time-varying image Jacobian matrix. Instead of updating the control signal directly, as is usually done in iterative learning control (ILC), a series of neural networks are used to approximate the unknown Jacobian matrix around every sample point in the demonstrated trajectory, and the time-varying weights of local neural networks are identified through repetitive tracking, i.e., indirect ILC. This makes repetitive segmented training possible, and a segmented training strategy is presented to retain the training trajectories solely within the effective region for neural network approximation. However, a singularity problem may occur if an unmodified neural-network-based Jacobian estimation is used to calculate the robot end-effector velocity. A new weight modification algorithm is proposed which ensures invertibility of the estimation, thus circumventing the problem. Stability is further discussed, and the relationship between the approximation capability of the neural network and the tracking accuracy is obtained. Simulations and experiments are carried out to illustrate the validity of the proposed controller for trajectory imitation of robot manipulators with unknown time-varying Jacobian matrices.

The RNA Chaperone Hfq Regulates Antibiotic Biosynthesis in the Rhizobacterium Pseudomonas aeruginosa M18

PubMed Central

Wang, Guohao; Li, Sainan; Huang, Jiaofang; Wei, Xue; Li, Yaqian

2012-01-01

The rhizosphere microbe Pseudomonas aeruginosa M18 shows strong antifungal activities, mainly due to the biosynthesis of antibiotics like pyoluteorin (Plt) and phenazine-1-carboxylic acid (PCA). The ubiquitous RNA chaperone Hfq regulates bacterial virulence and stress tolerance through global posttranscriptional regulation. Here, we explored the molecular mechanism by which Hfq controls antibiotic biosynthesis in P. aeruginosa M18. The robust downregulation of Plt biosynthesis by Hfq was mediated exclusively by the posttranscriptional downregulation of the plt transcriptional activator PltR. Hfq posttranscriptionally repressed phzM expression and consequently reduced the conversion of PCA to pyocyanin. However, Hfq positively controlled the phz2 operon and PCA biosynthesis through both QscR-mediated transcriptional regulation at the promoter and an unknown regulation at the operator. Also, Hfq was shown to directly bind at the mRNA 5′ untranslated leaders of pltR, qscR, and phzM. These three negatively regulated target genes of Hfq shared a similar secondary structure with a short single-stranded AU-rich spacer (a potential Hfq-binding motif) linking two stem-loops. Taken together, these results indicate that Hfq, potentially in collaboration with unknown small noncoding RNAs (sRNAs), tightly controls antibiotic biosynthesis through both direct posttranscriptional inhibition and indirect transcriptional regulation. PMID:22427627

Switching Adaptability in Human-Inspired Sidesteps: A Minimal Model.

PubMed

Fujii, Keisuke; Yoshihara, Yuki; Tanabe, Hiroko; Yamamoto, Yuji

2017-01-01

Humans can adapt to abruptly changing situations by coordinating redundant components, even in bipedality. Conventional adaptability has been reproduced by various computational approaches, such as optimal control, neural oscillator, and reinforcement learning; however, the adaptability in bipedal locomotion necessary for biological and social activities, such as unpredicted direction change in chase-and-escape, is unknown due to the dynamically unstable multi-link closed-loop system. Here we propose a switching adaptation model for performing bipedal locomotion by improving autonomous distributed control, where autonomous actuators interact without central control and switch the roles for propulsion, balancing, and leg swing. Our switching mobility model achieved direction change at any time using only three actuators, although it showed higher motor costs than comparable models without direction change. Our method of evaluating such adaptation at any time should be utilized as a prerequisite for understanding universal motor control. The proposed algorithm may simply explain and predict the adaptation mechanism in human bipedality to coordinate the actuator functions within and between limbs.

Interventional effects for mediation analysis with multiple mediators

PubMed Central

Vansteelandt, Stijn; Daniel, Rhian M.

2016-01-01

The mediation formula for the identification of natural (in)direct effects has facilitated mediation analyses that better respect the nature of the data, with greater consideration of the need for confounding control. The default assumptions on which it relies are strong, however. In particular, they are known to be violated when confounders of the mediator–outcome association are affected by the exposure. This complicates extensions of counterfactual-based mediation analysis to settings that involve repeatedly measured mediators, or multiple correlated mediators. VanderWeele, Vansteelandt, and Robins21 introduced so-called interventional (in)direct effects. These can be identified under much weaker conditions than natural (in)direct effects, but have the drawback of not adding up to the total effect. In this article, we adapt their proposal in order to achieve an exact decomposition of the total effect, and extend it to the multiple mediator setting. Interestingly, the proposed effects capture the path-specific effects of an exposure on an outcome that are mediated by distinct mediators, even when – as often – the structural dependence between the multiple mediators is unknown; for instance, when the direction of the causal effects between the mediators is unknown, or there may be unmeasured common causes of the mediators. PMID:27922534

Interventional Effects for Mediation Analysis with Multiple Mediators.

PubMed

Vansteelandt, Stijn; Daniel, Rhian M

2017-03-01

The mediation formula for the identification of natural (in)direct effects has facilitated mediation analyses that better respect the nature of the data, with greater consideration of the need for confounding control. The default assumptions on which it relies are strong, however. In particular, they are known to be violated when confounders of the mediator-outcome association are affected by the exposure. This complicates extensions of counterfactual-based mediation analysis to settings that involve repeatedly measured mediators, or multiple correlated mediators. VanderWeele, Vansteelandt, and Robins introduced so-called interventional (in)direct effects. These can be identified under much weaker conditions than natural (in)direct effects, but have the drawback of not adding up to the total effect. In this article, we adapt their proposal to achieve an exact decomposition of the total effect, and extend it to the multiple mediator setting. Interestingly, the proposed effects capture the path-specific effects of an exposure on an outcome that are mediated by distinct mediators, even when-as often-the structural dependence between the multiple mediators is unknown, for instance, when the direction of the causal effects between the mediators is unknown, or there may be unmeasured common causes of the mediators.

Locus of control as a stress moderator and mediator in children of divorce.

PubMed

Kim, L S; Sandler, I N; Tein, J Y

1997-04-01

This paper examined the stress moderator and mediator effects of four dimensions of perceived control in children of divorce. The dimensions of locus of control included internal control for positive events, internal control for negative events, unknown control for positive events, and unknown control for negative events. The sample consisted of 222 children between the ages of 8 and 12 whose parents had divorced in the previous 2 years. Moderational analyses showed that unknown control for positive events interacted with negative events to predict total symptoms. Plots of the simple slopes indicated a stress buffering effect whereby the slope of negative events on symptoms was higher for high than for low levels of unknown control for positive events. Mediational analysis showed that the relations between negative events and symptoms were mediated by both unknown control for positive events and unknown control for negative events. In contrast, evidence was not found for either a stress mediational or a moderational model for perceived internal control for positive or negative events. These results suggest that unknown control beliefs may be a particularly important dimension of control for children of divorce.

Off-Policy Actor-Critic Structure for Optimal Control of Unknown Systems With Disturbances.

PubMed

Song, Ruizhuo; Lewis, Frank L; Wei, Qinglai; Zhang, Huaguang

2016-05-01

An optimal control method is developed for unknown continuous-time systems with unknown disturbances in this paper. The integral reinforcement learning (IRL) algorithm is presented to obtain the iterative control. Off-policy learning is used to allow the dynamics to be completely unknown. Neural networks are used to construct critic and action networks. It is shown that if there are unknown disturbances, off-policy IRL may not converge or may be biased. For reducing the influence of unknown disturbances, a disturbances compensation controller is added. It is proven that the weight errors are uniformly ultimately bounded based on Lyapunov techniques. Convergence of the Hamiltonian function is also proven. The simulation study demonstrates the effectiveness of the proposed optimal control method for unknown systems with disturbances.

Finite-time tracking control for multiple non-holonomic mobile robots based on visual servoing

NASA Astrophysics Data System (ADS)

Ou, Meiying; Li, Shihua; Wang, Chaoli

2013-12-01

This paper investigates finite-time tracking control problem of multiple non-holonomic mobile robots via visual servoing. It is assumed that the pinhole camera is fixed to the ceiling, and camera parameters are unknown. The desired reference trajectory is represented by a virtual leader whose states are available to only a subset of the followers, and the followers have only interaction. First, the camera-objective visual kinematic model is introduced by utilising the pinhole camera model for each mobile robot. Second, a unified tracking error system between camera-objective visual servoing model and desired reference trajectory is introduced. Third, based on the neighbour rule and by using finite-time control method, continuous distributed cooperative finite-time tracking control laws are designed for each mobile robot with unknown camera parameters, where the communication topology among the multiple mobile robots is assumed to be a directed graph. Rigorous proof shows that the group of mobile robots converges to the desired reference trajectory in finite time. Simulation example illustrates the effectiveness of our method.

Simple robust control laws for robot manipulators. Part 2: Adaptive case

NASA Technical Reports Server (NTRS)

Bayard, D. S.; Wen, J. T.

1987-01-01

A new class of asymptotically stable adaptive control laws is introduced for application to the robotic manipulator. Unlike most applications of adaptive control theory to robotic manipulators, this analysis addresses the nonlinear dynamics directly without approximation, linearization, or ad hoc assumptions, and utilizes a parameterization based on physical (time-invariant) quantities. This approach is made possible by using energy-like Lyapunov functions which retain the nonlinear character and structure of the dynamics, rather than simple quadratic forms which are ubiquitous to the adaptive control literature, and which have bound the theory tightly to linear systems with unknown parameters. It is a unique feature of these results that the adaptive forms arise by straightforward certainty equivalence adaptation of their nonadaptive counterparts found in the companion to this paper (i.e., by replacing unknown quantities by their estimates) and that this simple approach leads to asymptotically stable closed-loop adaptive systems. Furthermore, it is emphasized that this approach does not require convergence of the parameter estimates (i.e., via persistent excitation), invertibility of the mass matrix estimate, or measurement of the joint accelerations.

Robust Control Design for Uncertain Nonlinear Dynamic Systems

NASA Technical Reports Server (NTRS)

Kenny, Sean P.; Crespo, Luis G.; Andrews, Lindsey; Giesy, Daniel P.

2012-01-01

Robustness to parametric uncertainty is fundamental to successful control system design and as such it has been at the core of many design methods developed over the decades. Despite its prominence, most of the work on robust control design has focused on linear models and uncertainties that are non-probabilistic in nature. Recently, researchers have acknowledged this disparity and have been developing theory to address a broader class of uncertainties. This paper presents an experimental application of robust control design for a hybrid class of probabilistic and non-probabilistic parametric uncertainties. The experimental apparatus is based upon the classic inverted pendulum on a cart. The physical uncertainty is realized by a known additional lumped mass at an unknown location on the pendulum. This unknown location has the effect of substantially altering the nominal frequency and controllability of the nonlinear system, and in the limit has the capability to make the system neutrally stable and uncontrollable. Another uncertainty to be considered is a direct current motor parameter. The control design objective is to design a controller that satisfies stability, tracking error, control power, and transient behavior requirements for the largest range of parametric uncertainties. This paper presents an overview of the theory behind the robust control design methodology and the experimental results.

The role of Myc-induced protein synthesis in cancer

PubMed Central

Ruggero, Davide

2009-01-01

Deregulation in different steps of translational control is an emerging mechanism for cancer formation. One example of an oncogene with a direct role in control of translation is the Myc transcription factor. Myc directly increases protein synthesis rates by controlling the expression of multiple components of the protein synthetic machinery, including ribosomal proteins, initiation factors of translation, Pol III and rDNA. However, the contribution of Myc-dependent increases in protein synthesis towards the multi-step process leading to cancer has remained unknown. Recent evidence strongly suggests that Myc oncogenic signaling may monopolize the translational machinery to elicit cooperative effects on cell growth, cell cycle progression, and genome instability as a mechanism for cancer initiation. Moreover, new genetic tools to restore aberrant increases in protein synthesis control are now available, which should enable the dissection of important mechanisms in cancer that rely on the translational machinery. PMID:19934336

New Finite Difference Methods Based on IIM for Inextensible Interfaces in Incompressible Flows

PubMed Central

Li, Zhilin; Lai, Ming-Chih

2012-01-01

In this paper, new finite difference methods based on the augmented immersed interface method (IIM) are proposed for simulating an inextensible moving interface in an incompressible two-dimensional flow. The mathematical models arise from studying the deformation of red blood cells in mathematical biology. The governing equations are incompressible Stokes or Navier-Stokes equations with an unknown surface tension, which should be determined in such a way that the surface divergence of the velocity is zero along the interface. Thus, the area enclosed by the interface and the total length of the interface should be conserved during the evolution process. Because of the nonlinear and coupling nature of the problem, direct discretization by applying the immersed boundary or immersed interface method yields complex nonlinear systems to be solved. In our new methods, we treat the unknown surface tension as an augmented variable so that the augmented IIM can be applied. Since finding the unknown surface tension is essentially an inverse problem that is sensitive to perturbations, our regularization strategy is to introduce a controlled tangential force along the interface, which leads to a least squares problem. For Stokes equations, the forward solver at one time level involves solving three Poisson equations with an interface. For Navier-Stokes equations, we propose a modified projection method that can enforce the pressure jump condition corresponding directly to the unknown surface tension. Several numerical experiments show good agreement with other results in the literature and reveal some interesting phenomena. PMID:23795308

ShiftNMFk 1.2

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

Alexandrov, Boian S.; Vesselinov, Velimir V.; Stanev, Valentin

The ShiftNMFk1.2 code, or as we call it, GreenNMFk, represents a hybrid algorithm combining unsupervised adaptive machine learning and Green's function inverse method. GreenNMFk allows an efficient and high performance de-mixing and feature extraction of a multitude of nonnegative signals that change their shape propagating through the medium. The signals are mixed and recorded by a network of uncorrelated sensors. The code couples Non-negative Matrix Factorization (NMF) and inverse-analysis Green's functions method. GreenNMF synergistically performs decomposition of the recorded mixtures, finds the number of the unknown sources and uses the Green's function of the governing partial differential equation to identifymore » the unknown sources and their charecteristics. GreenNMF can be applied directly to any problem controlled by a known partial-differential parabolic equation where mixtures of an unknown number of sources are measured at multiple locations. Full GreenNMFk method is a subject LANL U.S. Patent application S133364.000 August, 2017. The ShiftNMFk 1.2 version here is a toy version of this method that can work with a limited number of unknown sources (4 or less).« less

Real-Time Decentralized Neural Control via Backstepping for a Robotic Arm Powered by Industrial Servomotors.

PubMed

Vazquez, Luis A; Jurado, Francisco; Castaneda, Carlos E; Santibanez, Victor

2018-02-01

This paper presents a continuous-time decentralized neural control scheme for trajectory tracking of a two degrees of freedom direct drive vertical robotic arm. A decentralized recurrent high-order neural network (RHONN) structure is proposed to identify online, in a series-parallel configuration and using the filtered error learning law, the dynamics of the plant. Based on the RHONN subsystems, a local neural controller is derived via backstepping approach. The effectiveness of the decentralized neural controller is validated on a robotic arm platform, of our own design and unknown parameters, which uses industrial servomotors to drive the joints.

In-flight wind identification and soft landing control for autonomous unmanned powered parafoils

NASA Astrophysics Data System (ADS)

Luo, Shuzhen; Tan, Panlong; Sun, Qinglin; Wu, Wannan; Luo, Haowen; Chen, Zengqiang

2018-04-01

For autonomous unmanned powered parafoil, the ability to perform a final flare manoeuvre against the wind direction can allow a considerable reduction of horizontal and vertical velocities at impact, enabling a soft landing for a safe delivery of sensible loads; the lack of knowledge about the surface-layer winds will result in messing up terminal flare manoeuvre. Moreover, unknown or erroneous winds can also prevent the parafoil system from reaching the target area. To realize accurate trajectory tracking and terminal soft landing in the unknown wind environment, an efficient in-flight wind identification method merely using Global Positioning System (GPS) data and recursive least square method is proposed to online identify the variable wind information. Furthermore, a novel linear extended state observation filter is proposed to filter the groundspeed of the powered parafoil system calculated by the GPS information to provide a best estimation of the present wind during flight. Simulation experiments and real airdrop tests demonstrate the great ability of this method to in-flight identify the variable wind field, and it can benefit the powered parafoil system to fulfil accurate tracking control and a soft landing in the unknown wind field with high landing accuracy and strong wind-resistance ability.

The Design and Development of an Omni-Directional Mobile Robot Oriented to an Intelligent Manufacturing System

PubMed Central

Qian, Jun; Zi, Bin; Ma, Yangang; Zhang, Dan

2017-01-01

In order to transport materials flexibly and smoothly in a tight plant environment, an omni-directional mobile robot based on four Mecanum wheels was designed. The mechanical system of the mobile robot is made up of three separable layers so as to simplify its combination and reorganization. Each modularized wheel was installed on a vertical suspension mechanism, which ensures the moving stability and keeps the distances of four wheels invariable. The control system consists of two-level controllers that implement motion control and multi-sensor data processing, respectively. In order to make the mobile robot navigate in an unknown semi-structured indoor environment, the data from a Kinect visual sensor and four wheel encoders were fused to localize the mobile robot using an extended Kalman filter with specific processing. Finally, the mobile robot was integrated in an intelligent manufacturing system for material conveying. Experimental results show that the omni-directional mobile robot can move stably and autonomously in an indoor environment and in industrial fields. PMID:28891964

The Design and Development of an Omni-Directional Mobile Robot Oriented to an Intelligent Manufacturing System.

PubMed

Qian, Jun; Zi, Bin; Wang, Daoming; Ma, Yangang; Zhang, Dan

2017-09-10

In order to transport materials flexibly and smoothly in a tight plant environment, an omni-directional mobile robot based on four Mecanum wheels was designed. The mechanical system of the mobile robot is made up of three separable layers so as to simplify its combination and reorganization. Each modularized wheel was installed on a vertical suspension mechanism, which ensures the moving stability and keeps the distances of four wheels invariable. The control system consists of two-level controllers that implement motion control and multi-sensor data processing, respectively. In order to make the mobile robot navigate in an unknown semi-structured indoor environment, the data from a Kinect visual sensor and four wheel encoders were fused to localize the mobile robot using an extended Kalman filter with specific processing. Finally, the mobile robot was integrated in an intelligent manufacturing system for material conveying. Experimental results show that the omni-directional mobile robot can move stably and autonomously in an indoor environment and in industrial fields.

Adaptive quantum computation in changing environments using projective simulation

NASA Astrophysics Data System (ADS)

Tiersch, M.; Ganahl, E. J.; Briegel, H. J.

2015-08-01

Quantum information processing devices need to be robust and stable against external noise and internal imperfections to ensure correct operation. In a setting of measurement-based quantum computation, we explore how an intelligent agent endowed with a projective simulator can act as controller to adapt measurement directions to an external stray field of unknown magnitude in a fixed direction. We assess the agent’s learning behavior in static and time-varying fields and explore composition strategies in the projective simulator to improve the agent’s performance. We demonstrate the applicability by correcting for stray fields in a measurement-based algorithm for Grover’s search. Thereby, we lay out a path for adaptive controllers based on intelligent agents for quantum information tasks.

Adaptive quantum computation in changing environments using projective simulation

PubMed Central

Tiersch, M.; Ganahl, E. J.; Briegel, H. J.

2015-01-01

Quantum information processing devices need to be robust and stable against external noise and internal imperfections to ensure correct operation. In a setting of measurement-based quantum computation, we explore how an intelligent agent endowed with a projective simulator can act as controller to adapt measurement directions to an external stray field of unknown magnitude in a fixed direction. We assess the agent’s learning behavior in static and time-varying fields and explore composition strategies in the projective simulator to improve the agent’s performance. We demonstrate the applicability by correcting for stray fields in a measurement-based algorithm for Grover’s search. Thereby, we lay out a path for adaptive controllers based on intelligent agents for quantum information tasks. PMID:26260263

Autonomous Landing and Smart Anchoring for In-Situ Exploration of Small Bodies

NASA Technical Reports Server (NTRS)

Ghavimi, Ali R.; Serricchio, Frederick; Hadaegh, Fred Y.; Dolgin, Ben

2000-01-01

Future NASA missions include in-situ scientific explorations of small interplanetary objects like comets and asteroids. Sample acquisition systems are envisioned to operate directly from the landers that are anchored to the surface. Landing and anchoring proves to be challenging in the absence of an attitude control system and in the presence of nearly zero-gravity environments with uncertain surface terrain and unknown mechanical properties. This paper presents recent advancements in developing a novel landing and anchoring control system for the exploration of small bodies.

Realtime motion planning for a mobile robot in an unknown environment using a neurofuzzy based approach

NASA Astrophysics Data System (ADS)

Zheng, Taixiong

2005-12-01

A neuro-fuzzy network based approach for robot motion in an unknown environment was proposed. In order to control the robot motion in an unknown environment, the behavior of the robot was classified into moving to the goal and avoiding obstacles. Then, according to the dynamics of the robot and the behavior character of the robot in an unknown environment, fuzzy control rules were introduced to control the robot motion. At last, a 6-layer neuro-fuzzy network was designed to merge from what the robot sensed to robot motion control. After being trained, the network may be used for robot motion control. Simulation results show that the proposed approach is effective for robot motion control in unknown environment.

A Single RF Emitter-Based Indoor Navigation Method for Autonomous Service Robots.

PubMed

Sherwin, Tyrone; Easte, Mikala; Chen, Andrew Tzer-Yeu; Wang, Kevin I-Kai; Dai, Wenbin

2018-02-14

Location-aware services are one of the key elements of modern intelligent applications. Numerous real-world applications such as factory automation, indoor delivery, and even search and rescue scenarios require autonomous robots to have the ability to navigate in an unknown environment and reach mobile targets with minimal or no prior infrastructure deployment. This research investigates and proposes a novel approach of dynamic target localisation using a single RF emitter, which will be used as the basis of allowing autonomous robots to navigate towards and reach a target. Through the use of multiple directional antennae, Received Signal Strength (RSS) is compared to determine the most probable direction of the targeted emitter, which is combined with the distance estimates to improve the localisation performance. The accuracy of the position estimate is further improved using a particle filter to mitigate the fluctuating nature of real-time RSS data. Based on the direction information, a motion control algorithm is proposed, using Simultaneous Localisation and Mapping (SLAM) and A* path planning to enable navigation through unknown complex environments. A number of navigation scenarios were developed in the context of factory automation applications to demonstrate and evaluate the functionality and performance of the proposed system.

A Single RF Emitter-Based Indoor Navigation Method for Autonomous Service Robots

PubMed Central

Sherwin, Tyrone; Easte, Mikala; Wang, Kevin I-Kai; Dai, Wenbin

2018-01-01

Location-aware services are one of the key elements of modern intelligent applications. Numerous real-world applications such as factory automation, indoor delivery, and even search and rescue scenarios require autonomous robots to have the ability to navigate in an unknown environment and reach mobile targets with minimal or no prior infrastructure deployment. This research investigates and proposes a novel approach of dynamic target localisation using a single RF emitter, which will be used as the basis of allowing autonomous robots to navigate towards and reach a target. Through the use of multiple directional antennae, Received Signal Strength (RSS) is compared to determine the most probable direction of the targeted emitter, which is combined with the distance estimates to improve the localisation performance. The accuracy of the position estimate is further improved using a particle filter to mitigate the fluctuating nature of real-time RSS data. Based on the direction information, a motion control algorithm is proposed, using Simultaneous Localisation and Mapping (SLAM) and A* path planning to enable navigation through unknown complex environments. A number of navigation scenarios were developed in the context of factory automation applications to demonstrate and evaluate the functionality and performance of the proposed system. PMID:29443906

Potential for direct interspecies electron transfer in an electric-anaerobic system to increase methane production from sludge digestion.

PubMed

Zhao, Zhiqiang; Zhang, Yaobin; Wang, Liying; Quan, Xie

2015-06-09

Direct interspecies electron transfer (DIET) between Geobacter species and Methanosaeta species is an alternative to interspecies hydrogen transfer (IHT) in anaerobic digester, which however has not been established in anaerobic sludge digestion as well as in bioelectrochemical systems yet. In this study, it was found that over 50% of methane production of an electric-anaerobic sludge digester was resulted from unknown pathway. Pyrosequencing analysis revealed that Geobacter species were significantly enriched with electrodes. Fluorescence in situ hybridization (FISH) further confirmed that the dominant Geobacter species enriched belonged to Geobacter metallireducens. Together with Methanosaeta species prevailing in the microbial communities, the direct electron exchange between Geobacter species and Methanosaeta species might be an important reason for the "unknown" increase of methane production. Conductivity of the sludge in this electric-anaerobic digester was about 30% higher than that of the sludge in a control digester without electrodes. This study not only revealed for the first time that DIET might be the important mechanism on the methanogenesis of bioelectrochemical system, but also provided a new method to enhance DIET by means of bioelectric enrichment of Geobacter species.

Adaptive control of dual-arm robots

NASA Technical Reports Server (NTRS)

Seraji, H.

1987-01-01

Three strategies for adaptive control of cooperative dual-arm robots are described. In the position-position control strategy, the adaptive controllers ensure that the end-effector positions of both arms track desired trajectories in Cartesian space despite unknown time-varying interaction forces exerted through the load. In the position-hybrid control strategy, the adaptive controller of one arm controls end-effector motions in the free directions and applied forces in the constraint directions, while the adaptive controller of the other arm ensures that the end-effector tracks desired position trajectories. In the hybrid-hybrid control strategy, the adaptive controllers ensure that both end-effectors track reference position trajectories while simultaneously applying desired forces on the load. In all three control strategies, the cross-coupling effects between the arms are treated as disturbances which are rejected by the adaptive controllers while following desired commands in a common frame of reference. The adaptive controllers do not require the complex mathematical model of the arm dynamics or any knowledge of the arm dynamic parameters or the load parameters such as mass and stiffness. The controllers have simple structures and are computationally fast for on-line implementation with high sampling rates.

Dynamic parameter identification of robot arms with servo-controlled electrical motors

NASA Astrophysics Data System (ADS)

Jiang, Zhao-Hui; Senda, Hiroshi

2005-12-01

This paper addresses the issue of dynamic parameter identification of the robot manipulator with servo-controlled electrical motors. An assumption is made that all kinematical parameters, such as link lengths, are known, and only dynamic parameters containing mass, moment of inertia, and their functions need to be identified. First, we derive dynamics of the robot arm with a linear form of the unknown dynamic parameters by taking dynamic characteristics of the motor and servo unit into consideration. Then, we implement the parameter identification approach to identify the unknown parameters with respect to individual link separately. A pseudo-inverse matrix is used for formulation of the parameter identification. The optimal solution is guaranteed in a sense of least-squares of the mean errors. A Direct Drive (DD) SCARA type industrial robot arm AdeptOne is used as an application example of the parameter identification. Simulations and experiments for both open loop and close loop controls are carried out. Comparison of the results confirms the correctness and usefulness of the parameter identification and the derived dynamic model.

Direct Adaptive Rejection of Vortex-Induced Disturbances for a Powered SPAR Platform

NASA Technical Reports Server (NTRS)

VanZwieten, Tannen S.; Balas, Mark J.; VanZwieten, James H.; Driscoll, Frederick R.

2009-01-01

The Rapidly Deployable Stable Platform (RDSP) is a novel vessel designed to be a reconfigurable, stable at-sea platform. It consists of a detachable catamaran and spar, performing missions with the spar extending vertically below the catamaran and hoisting it completely out of the water. Multiple thrusters located along the spar allow it to be actively controlled in this configuration. A controller is presented in this work that uses an adaptive feedback algorithm in conjunction with Direct Adaptive Disturbance Rejection (DADR) to mitigate persistent, vortex-induced disturbances. Given the frequency of a disturbance, the nominal DADR scheme adaptively compensates for its unknown amplitude and phase. This algorithm is extended to adapt to a disturbance frequency that is only coarsely known by including a Phase Locked Loop (PLL). The PLL improves the frequency estimate on-line, allowing the modified controller to reduce vortex-induced motions by more than 95% using achievable thrust inputs.

Decentralised output feedback control of Markovian jump interconnected systems with unknown interconnections

NASA Astrophysics Data System (ADS)

Li, Li-Wei; Yang, Guang-Hong

2017-07-01

The problem of decentralised output feedback control is addressed for Markovian jump interconnected systems with unknown interconnections and general transition rates (TRs) allowed to be unknown or known with uncertainties. A class of decentralised dynamic output feedback controllers are constructed, and a cyclic-small-gain condition is exploited to dispose the unknown interconnections so that the resultant closed-loop system is stochastically stable and satisfies an H∞ performance. With slack matrices to cope with the nonlinearities incurred by unknown and uncertain TRs in control synthesis, a novel controller design condition is developed in linear matrix inequality formalism. Compared with the existing works, the proposed approach leads to less conservatism. Finally, two examples are used to illustrate the effectiveness of the new results.

Accommodating Sensor Bias in MRAC for State Tracking

NASA Technical Reports Server (NTRS)

Patre, Parag; Joshi, Suresh M.

2011-01-01

The problem of accommodating unknown sensor bias is considered in a direct model reference adaptive control (MRAC) setting for state tracking using state feedback. Sensor faults can occur during operation, and if the biased state measurements are directly used with a standard MRAC control law, neither closed-loop signal boundedness, nor asymptotic tracking can be guaranteed and the resulting tracking errors may be unbounded or unacceptably large. A modified MRAC law is proposed, which combines a bias estimator with control gain adaptation, and it is shown that signal boundedness can be accomplished, although the tracking error may not go to zero. Further, for the case wherein an asymptotically stable sensor bias estimator is available, an MRAC control law is proposed to accomplish asymptotic tracking and signal boundedness. Such a sensor bias estimator can be designed if additional sensor measurements are available, as illustrated for the case wherein bias is present in the rate gyro and airspeed measurements. Numerical example results are presented to illustrate each of the schemes.

Adaptive Fault-Tolerant Control of Uncertain Nonlinear Large-Scale Systems With Unknown Dead Zone.

PubMed

Chen, Mou; Tao, Gang

2016-08-01

In this paper, an adaptive neural fault-tolerant control scheme is proposed and analyzed for a class of uncertain nonlinear large-scale systems with unknown dead zone and external disturbances. To tackle the unknown nonlinear interaction functions in the large-scale system, the radial basis function neural network (RBFNN) is employed to approximate them. To further handle the unknown approximation errors and the effects of the unknown dead zone and external disturbances, integrated as the compounded disturbances, the corresponding disturbance observers are developed for their estimations. Based on the outputs of the RBFNN and the disturbance observer, the adaptive neural fault-tolerant control scheme is designed for uncertain nonlinear large-scale systems by using a decentralized backstepping technique. The closed-loop stability of the adaptive control system is rigorously proved via Lyapunov analysis and the satisfactory tracking performance is achieved under the integrated effects of unknown dead zone, actuator fault, and unknown external disturbances. Simulation results of a mass-spring-damper system are given to illustrate the effectiveness of the proposed adaptive neural fault-tolerant control scheme for uncertain nonlinear large-scale systems.

Remote possibly hazardous content container sampling device

DOEpatents

Volz, David L.

1998-01-01

The present invention relates to an apparatus capable of sampling enclosed containers, where the contents of the container is unknown. The invention includes a compressed air device capable of supplying air pressure, device for controlling the amount of air pressure applied, a pneumatic valve, a sampling device having a hollow, sampling insertion needle suspended therein and device to communicate fluid flow between the container and a containment vessel, pump or direct reading instrument.

Diet-induced obesity accelerates acute lymphoblastic leukemia progression in two murine models.

PubMed

Yun, Jason P; Behan, James W; Heisterkamp, Nora; Butturini, Anna; Klemm, Lars; Ji, Lingyun; Groffen, John; Müschen, Markus; Mittelman, Steven D

2010-10-01

Obesity is associated with an increased incidence of many cancers, including leukemia, although it is unknown whether leukemia incidence is increased directly by obesity or rather by associated genetic, lifestyle, health, or socioeconomic factors. We developed animal models of obesity and leukemia to test whether obesity could directly accelerate acute lymphoblastic leukemia (ALL) using BCR/ABL transgenic and AKR/J mice weaned onto a high-fat diet. Mice were observed until development of progressive ALL. Although obese and control BCR/ABL mice had similar median survival, older obese mice had accelerated ALL onset, implying a time-dependent effect of obesity on ALL. Obese AKR mice developed ALL significantly earlier than controls. The effect of obesity was not explained by WBC count, thymus/spleen weight, or ALL phenotype. However, obese AKR mice had higher leptin, insulin, and interleukin-6 levels than controls, and these obesity-related hormones all have potential roles in leukemia pathogenesis. In conclusion, obesity directly accelerates presentation of ALL, likely by increasing the risk of an early event in leukemogenesis. This is the first study to show that obesity can directly accelerate the progression of ALL. Thus, the observed associations between obesity and leukemia incidence are likely to be directly related to biological effects of obesity. ©2010 AACR.

Lamellipodin and the Scar/WAVE complex cooperate to promote cell migration in vivo

PubMed Central

Law, Ah-Lai; Vehlow, Anne; Kotini, Maria; Dodgson, Lauren; Soong, Daniel; Theveneau, Eric; Bodo, Cristian; Taylor, Eleanor; Navarro, Christel; Perera, Upamali; Michael, Magdalene; Dunn, Graham A.; Bennett, Daimark; Mayor, Roberto

2013-01-01

Cell migration is essential for development, but its deregulation causes metastasis. The Scar/WAVE complex is absolutely required for lamellipodia and is a key effector in cell migration, but its regulation in vivo is enigmatic. Lamellipodin (Lpd) controls lamellipodium formation through an unknown mechanism. Here, we report that Lpd directly binds active Rac, which regulates a direct interaction between Lpd and the Scar/WAVE complex via Abi. Consequently, Lpd controls lamellipodium size, cell migration speed, and persistence via Scar/WAVE in vitro. Moreover, Lpd knockout mice display defective pigmentation because fewer migrating neural crest-derived melanoblasts reach their target during development. Consistently, Lpd regulates mesenchymal neural crest cell migration cell autonomously in Xenopus laevis via the Scar/WAVE complex. Further, Lpd’s Drosophila melanogaster orthologue Pico binds Scar, and both regulate collective epithelial border cell migration. Pico also controls directed cell protrusions of border cell clusters in a Scar-dependent manner. Taken together, Lpd is an essential, evolutionary conserved regulator of the Scar/WAVE complex during cell migration in vivo. PMID:24247431

Intelligent on-line fault tolerant control for unanticipated catastrophic failures.

PubMed

Yen, Gary G; Ho, Liang-Wei

2004-10-01

As dynamic systems become increasingly complex, experience rapidly changing environments, and encounter a greater variety of unexpected component failures, solving the control problems of such systems is a grand challenge for control engineers. Traditional control design techniques are not adequate to cope with these systems, which may suffer from unanticipated dynamic failures. In this research work, we investigate the on-line fault tolerant control problem and propose an intelligent on-line control strategy to handle the desired trajectories tracking problem for systems suffering from various unanticipated catastrophic faults. Through theoretical analysis, the sufficient condition of system stability has been derived and two different on-line control laws have been developed. The approach of the proposed intelligent control strategy is to continuously monitor the system performance and identify what the system's current state is by using a fault detection method based upon our best knowledge of the nominal system and nominal controller. Once a fault is detected, the proposed intelligent controller will adjust its control signal to compensate for the unknown system failure dynamics by using an artificial neural network as an on-line estimator to approximate the unexpected and unknown failure dynamics. The first control law is derived directly from the Lyapunov stability theory, while the second control law is derived based upon the discrete-time sliding mode control technique. Both control laws have been implemented in a variety of failure scenarios to validate the proposed intelligent control scheme. The simulation results, including a three-tank benchmark problem, comply with theoretical analysis and demonstrate a significant improvement in trajectory following performance based upon the proposed intelligent control strategy.

Path Planning for Robot based on Chaotic Artificial Potential Field Method

NASA Astrophysics Data System (ADS)

Zhang, Cheng

2018-03-01

Robot path planning in unknown environments is one of the hot research topics in the field of robot control. Aiming at the shortcomings of traditional artificial potential field methods, we propose a new path planning for Robot based on chaotic artificial potential field method. The path planning adopts the potential function as the objective function and introduces the robot direction of movement as the control variables, which combines the improved artificial potential field method with chaotic optimization algorithm. Simulations have been carried out and the results demonstrate that the superior practicality and high efficiency of the proposed method.

Bayesian nonlinear structural FE model and seismic input identification for damage assessment of civil structures

NASA Astrophysics Data System (ADS)

Astroza, Rodrigo; Ebrahimian, Hamed; Li, Yong; Conte, Joel P.

2017-09-01

A methodology is proposed to update mechanics-based nonlinear finite element (FE) models of civil structures subjected to unknown input excitation. The approach allows to jointly estimate unknown time-invariant model parameters of a nonlinear FE model of the structure and the unknown time histories of input excitations using spatially-sparse output response measurements recorded during an earthquake event. The unscented Kalman filter, which circumvents the computation of FE response sensitivities with respect to the unknown model parameters and unknown input excitations by using a deterministic sampling approach, is employed as the estimation tool. The use of measurement data obtained from arrays of heterogeneous sensors, including accelerometers, displacement sensors, and strain gauges is investigated. Based on the estimated FE model parameters and input excitations, the updated nonlinear FE model can be interrogated to detect, localize, classify, and assess damage in the structure. Numerically simulated response data of a three-dimensional 4-story 2-by-1 bay steel frame structure with six unknown model parameters subjected to unknown bi-directional horizontal seismic excitation, and a three-dimensional 5-story 2-by-1 bay reinforced concrete frame structure with nine unknown model parameters subjected to unknown bi-directional horizontal seismic excitation are used to illustrate and validate the proposed methodology. The results of the validation studies show the excellent performance and robustness of the proposed algorithm to jointly estimate unknown FE model parameters and unknown input excitations.

Dual-arm manipulators with adaptive control

NASA Technical Reports Server (NTRS)

Seraji, Homayoun (Inventor)

1991-01-01

The described and improved multi-arm invention of this application presents three strategies for adaptive control of cooperative multi-arm robots which coordinate control over a common load. In the position-position control strategy, the adaptive controllers ensure that the end-effector positions of both arms track desired trajectories in Cartesian space despite unknown time-varying interaction forces exerted through a load. In the position-hybrid control strategy, the adaptive controller of one arm controls end-effector motions in the free directions and applied forces in the constraint directions; while the adaptive controller of the other arm ensures that the end-effector tracks desired position trajectories. In the hybrid-hybrid control strategy, the adaptive controllers ensure that both end-effectors track reference position trajectories while simultaneously applying desired forces on the load. In all three control strategies, the cross-coupling effects between the arms are treated as disturbances which are compensated for by the adaptive controllers while following desired commands in a common frame of reference. The adaptive controllers do not require the complex mathematical model of the arm dynamics or any knowledge of the arm dynamic parameters or the load parameters such as mass and stiffness. Circuits in the adaptive feedback and feedforward controllers are varied by novel adaptation laws.

Method and apparatus for adaptive force and position control of manipulators

NASA Technical Reports Server (NTRS)

Seraji, Homayoun (Inventor)

1995-01-01

The described and improved multi-arm invention of this application presents three strategies for adaptive control of cooperative multi-arm robots which coordinate control over a common load. In the position-position control strategy, the adaptive controllers ensure that the end-effector positions of both arms track desired trajectories in Cartesian space despite unknown time-varying interaction forces exerted through a load. In the position-hybrid control strategy, the adaptive controller of one arm controls end-effector motions in the free directions and applied forces in the constraint directions; while the adaptive controller of the other arm ensures that the end-effector tracks desired position trajectories. In the hybrid-hybrid control strategy, the adaptive controllers ensure that both end-effectors track reference position trajectories while simultaneously applying desired forces on the load. In all three control strategies, the cross-coupling effects between the arms are treated as disturbances which are compensated for by the adaptive controllers while following desired commands in a common frame of reference. The adaptive controllers do not require the complex mathematical model of the arm dynamics or any knowledge of the arm dynamic parameters or the load parameters such as mass and stiffness. Circuits in the adaptive feedback and feedforward controllers are varied by novel adaptation laws.

Costs of injuries due to interpersonal and self-directed violence in Thailand, 2005.

PubMed

Bundhamcharoen, Kanitta; Odton, Patarapan; Mugem, Suwanna; Phulkerd, Sirinya; Dhisayathikom, Kanjana; Brown, David W; Tangcharoensathien, Viroj

2008-06-01

Violence, a serious public health problem in Thailand, remains largely unknown for its economic costs. This study is a national-level economic cost-estimates of injury from interpersonal and self-directed violence for Thailand during 2005 using the World Health Organization-US Centers for Disease Control and Prevention's guidelines. Direct medical costs from self-directed violence totaled 569 million Baht (THB) while the cost of interpersonal violence was THB 1.3 billion. Productivity losses for injuries due to self-directed violence were estimated at THB 12.2 billion and those for interpersonal violence were THB 14.4 billion. The total direct medical cost, thus, accounted for about 4% of Thailand's total health budget while the productivity losses accounted for approximately 0.4% of Thailand s GDP In summary, interpersonal and self-directed violence caused a total loss of 33.8 billion baht for Thailand in 2005. More than 90% of the economic loss was incurred from productivity loss and about four-fifths came from men.

When pupils do not understand the determinants of their success and failure in school: relations between internal, teacher and unknown perceptions of control and school achievement.

PubMed

Butler, R; Orion, R

1990-02-01

Both dispositional and attributional perspectives on perceptions of control assume that people have some idea of outcome determinants. This, however, may not always be so. This study tested the hypothesis that pupils do not always understand the determinants of their learning outcomes, and that such a sense of unknown control will be associated with poor achievement in school. The study was unusual in that it tapped both dispositional control perceptions, using the new MMPCC, and causal attributions for success and failure in a school examination. Subjects were 186 10-year-old Israeli pupils of heterogeneous SES. Results confirmed that unknown control emerged as a distinct dimension of perceived control in both dispositional and attributional measures, and was consistently associated with poor achievement in school. Attributions of test outcomes to unknown causes were strongly related to dispositional unknown control, and were not affected by success or failure. In contrast, dispositional and attributional internality were unrelated, and did not predict achievement. It is argued that internal beliefs reflect internalised social-educational norms, and as a result have less impact on motivation than perceptions of unknown control. The implications of these findings for educational practice and motivational interventions are discussed.

Hip adductor activations during run-to-cut maneuvers in compression shorts: Implications for return to sport after groin injury

PubMed Central

CHAUDHARI, AJIT M. W.; JAMISON, STEVEN T.; MCNALLY, MICHAEL P.; PAN, XUELIANG; SCHMITT, LAURA C.

2014-01-01

Athletes at high risk of groin strains in sports such as hockey and soccer often choose to wear shorts with directional compression to aid in prevention or recovery from hip adductor strains. Large eccentric contractions are known to result in or exacerbate strain injuries, but it is unknown if these shorts have a beneficial effect on hip adductor muscle activity. In this study, surface electromyography of the adductor longus and ground reaction force (GRF) data were obtained simultaneously on 29 healthy individuals without previous history of serious injury while performing unanticipated 45° run-to-cut maneuvers in a laboratory setting wearing shorts with non-directional compression (control, HeatGear, Under Armour, USA) or shorts with directional compression (directional, CoreShort PRO, Under Armour, USA), in random order. Average adductor activity in the stance leg was significantly lower in the directional condition than in the control condition during all parts of stance phase (all p<0.042). From this preliminary analysis, wearing directional compression shorts appears to be associated with reduced stance limb hip adductor activity. Athletes seeking to reduce demand on the hip adductors as they approach full return to activities may benefit from the use of directional compression shorts. PMID:24669858

Hip adductor activations during run-to-cut manoeuvres in compression shorts: implications for return to sport after groin injury.

PubMed

Chaudhari, Ajit M W; Jamison, Steven T; McNally, Michael P; Pan, Xueliang; Schmitt, Laura C

2014-01-01

Athletes at high risk of groin strains in sports such as hockey and soccer often choose to wear shorts with directional compression to aid in prevention of or recovery from hip adductor strains. Large, eccentric contractions are known to result in or exacerbate strain injuries, but it is unknown if these shorts have a beneficial effect on hip adductor muscle activity. In this study, surface electromyography (EMG) of the adductor longus and ground reaction force (GRF) data were obtained simultaneously on 29 healthy individuals without previous history of serious injury while performing unanticipated 45° run-to-cut manoeuvres in a laboratory setting wearing shorts with non-directional compression (control, HeatGear, Under Armour, USA) or shorts with directional compression (directional, CoreShort PRO, Under Armour, USA), in random order. Average adductor activity in the stance leg was significantly lower in the directional condition than in the control condition during all parts of stance phase (all P < 0.042). From this preliminary analysis, wearing directional compression shorts appears to be associated with reduced stance limb hip adductor activity. Athletes seeking to reduce demand on the hip adductors as they approach full return to activities may benefit from the use of directional compression shorts.

Adaptive near-optimal neuro controller for continuous-time nonaffine nonlinear systems with constrained input.

PubMed

Esfandiari, Kasra; Abdollahi, Farzaneh; Talebi, Heidar Ali

2017-09-01

In this paper, an identifier-critic structure is introduced to find an online near-optimal controller for continuous-time nonaffine nonlinear systems having saturated control signal. By employing two Neural Networks (NNs), the solution of Hamilton-Jacobi-Bellman (HJB) equation associated with the cost function is derived without requiring a priori knowledge about system dynamics. Weights of the identifier and critic NNs are tuned online and simultaneously such that unknown terms are approximated accurately and the control signal is kept between the saturation bounds. The convergence of NNs' weights, identification error, and system states is guaranteed using Lyapunov's direct method. Finally, simulation results are performed on two nonlinear systems to confirm the effectiveness of the proposed control strategy. Copyright © 2017 Elsevier Ltd. All rights reserved.

Two SHIPs passing in the middle of the immune system.

PubMed

Corey, Seth J; Mehta, Hrishikesh M; Stein, Paul L

2012-07-01

Immunity requires a complex, multiscale system of molecules, cells, and cytokines. In this issue of the European Journal of Immunology, Collazo et al. [Eur. J. Immunol. 2012. 42: 1785-1796] provide evidence that links the lipid phosphatase SHIP1 with the coordination of interactions between regulatory T (Treg) cells and myeloid-derived suppressor cells (MDSCs). Using conditional knockouts of SHIP1 in either the myeloid or T-cell-lineage of mice, the authors show that the regulated development of Treg cells is controlled directly by cell-intrinsic SHIP1, and indirectly by extrinsic SHIP1 control of an unknown myeloid cell. Regulation of MDSCs is also determined by SHIP1 in an extrinsic manner, again via an as-yet-unknown myeloid cell. Furthermore, this extrinsic control of Treg cells and MDSCs is mediated in part by increased production of G-CSF, a growth factor critical for the production of neutrophils, in SHIP1-deficient mice. Thus, a physiologically important implication of this report is the collaboration between the innate and adaptive immune systems in fine tuning of Treg cells as discussed in this commentary. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Restricted Complexity Framework for Nonlinear Adaptive Control in Complex Systems

NASA Astrophysics Data System (ADS)

Williams, Rube B.

2004-02-01

Control law adaptation that includes implicit or explicit adaptive state estimation, can be a fundamental underpinning for the success of intelligent control in complex systems, particularly during subsystem failures, where vital system states and parameters can be impractical or impossible to measure directly. A practical algorithm is proposed for adaptive state filtering and control in nonlinear dynamic systems when the state equations are unknown or are too complex to model analytically. The state equations and inverse plant model are approximated by using neural networks. A framework for a neural network based nonlinear dynamic inversion control law is proposed, as an extrapolation of prior developed restricted complexity methodology used to formulate the adaptive state filter. Examples of adaptive filter performance are presented for an SSME simulation with high pressure turbine failure to support extrapolations to adaptive control problems.

Adaptive control of Parkinson's state based on a nonlinear computational model with unknown parameters.

PubMed

Su, Fei; Wang, Jiang; Deng, Bin; Wei, Xi-Le; Chen, Ying-Yuan; Liu, Chen; Li, Hui-Yan

2015-02-01

The objective here is to explore the use of adaptive input-output feedback linearization method to achieve an improved deep brain stimulation (DBS) algorithm for closed-loop control of Parkinson's state. The control law is based on a highly nonlinear computational model of Parkinson's disease (PD) with unknown parameters. The restoration of thalamic relay reliability is formulated as the desired outcome of the adaptive control methodology, and the DBS waveform is the control input. The control input is adjusted in real time according to estimates of unknown parameters as well as the feedback signal. Simulation results show that the proposed adaptive control algorithm succeeds in restoring the relay reliability of the thalamus, and at the same time achieves accurate estimation of unknown parameters. Our findings point to the potential value of adaptive control approach that could be used to regulate DBS waveform in more effective treatment of PD.

Active vibration control for piezoelectricity cantilever beam: an adaptive feedforward control method

NASA Astrophysics Data System (ADS)

Zhu, Qiao; Yue, Jun-Zhou; Liu, Wei-Qun; Wang, Xu-Dong; Chen, Jun; Hu, Guang-Di

2017-04-01

This work is focused on the active vibration control of piezoelectric cantilever beam, where an adaptive feedforward controller (AFC) is utilized to reject the vibration with unknown multiple frequencies. First, the experiment setup and its mathematical model are introduced. Due to that the channel between the disturbance and the vibration output is unknown in practice, a concept of equivalent input disturbance (EID) is employed to put an equivalent disturbance into the input channel. In this situation, the vibration control can be achieved by setting the control input be the identified EID. Then, for the EID with known multiple frequencies, the AFC is introduced to perfectly reject the vibration but is sensitive to the frequencies. In order to accurately identify the unknown frequencies of EID in presence of the random disturbances and un-modeled nonlinear dynamics, the time-frequency-analysis (TFA) method is employed to precisely identify the unknown frequencies. Consequently, a TFA-based AFC algorithm is proposed to the active vibration control with unknown frequencies. Finally, four cases are given to illustrate the efficiency of the proposed TFA-based AFC algorithm by experiment.

Adaptive Control Using Residual Mode Filters Applied to Wind Turbines

NASA Technical Reports Server (NTRS)

Frost, Susan A.; Balas, Mark J.

2011-01-01

Many dynamic systems containing a large number of modes can benefit from adaptive control techniques, which are well suited to applications that have unknown parameters and poorly known operating conditions. In this paper, we focus on a model reference direct adaptive control approach that has been extended to handle adaptive rejection of persistent disturbances. We extend this adaptive control theory to accommodate problematic modal subsystems of a plant that inhibit the adaptive controller by causing the open-loop plant to be non-minimum phase. We will augment the adaptive controller using a Residual Mode Filter (RMF) to compensate for problematic modal subsystems, thereby allowing the system to satisfy the requirements for the adaptive controller to have guaranteed convergence and bounded gains. We apply these theoretical results to design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed wind turbine that has minimum phase zeros.

Global neural dynamic surface tracking control of strict-feedback systems with application to hypersonic flight vehicle.

PubMed

Xu, Bin; Yang, Chenguang; Pan, Yongping

2015-10-01

This paper studies both indirect and direct global neural control of strict-feedback systems in the presence of unknown dynamics, using the dynamic surface control (DSC) technique in a novel manner. A new switching mechanism is designed to combine an adaptive neural controller in the neural approximation domain, together with the robust controller that pulls the transient states back into the neural approximation domain from the outside. In comparison with the conventional control techniques, which could only achieve semiglobally uniformly ultimately bounded stability, the proposed control scheme guarantees all the signals in the closed-loop system are globally uniformly ultimately bounded, such that the conventional constraints on initial conditions of the neural control system can be relaxed. The simulation studies of hypersonic flight vehicle (HFV) are performed to demonstrate the effectiveness of the proposed global neural DSC design.

Direction of illumination controls gametophyte orientation in seedless plants and related algae

PubMed Central

Cardona-Correa, Christopher; Ecker, Alice; Graham, Linda E

2015-01-01

The environmental influences that determine dorsiventral or axial gametophyte orientation are unknown for most modern seedless plants. To fill this gap, an experimental laboratory system was employed to evaluate the relative effects of light direction and gravity on body orientation of the dorsiventral green alga Coleochaete orbicularis, and gametophytes of liverworts Blasia pusilla and Marchantia polymorpha, early-diverging moss Sphagnum compactum, and fern Ceratopteris richardii, the latter functioning as experimental control. Replicate clonal cultures were experimentally illuminated only from above, only from below, or from multiple directions, with the same near-saturation PAR level for periods brief enough to minimize nutrient limitation effects, and orientation of new growth was evaluated. For all species tested, direction of illumination exerted stronger control over gametophyte body orientation than gravity. When illuminated only from below: 1) axial Sphagnum gametophores that had initially grown into an overlying air space inverted growth by 180°, burrowing into the substrate; 2) new growth of dorsiventral Blasia, Marchantia, and Ceratopteris gametophytes–whose ventral rhizoids initially penetrated agar substrate and dorsal surfaces initially faced overlying airspace–twisted 180° so that ventral surfaces bearing rhizoids faced overlying air space and rhizoids extended into the air; and 3) Coleochaete lost typical dorsiventral organization and diagnostic dorsal hairs. Direction of illumination also exerted stronger control over orientation of liverwort new growth than surface contact did. These results indicate that early land plants likely inherited light-directed gametophyte body orientation from ancestral streptophyte algae and suggest a mechanism for reorientation of gametophyte-dominant land plants after spatial disturbance. PMID:26237278

Direction of illumination controls gametophyte orientation in seedless plants and related algae.

PubMed

Cardona-Correa, Christopher; Ecker, Alice; Graham, Linda E

2015-01-01

The environmental influences that determine dorsiventral or axial gametophyte orientation are unknown for most modern seedless plants. To fill this gap, an experimental laboratory system was employed to evaluate the relative effects of light direction and gravity on body orientation of the dorsiventral green alga Coleochaete orbicularis, and gametophytes of liverworts Blasia pusilla and Marchantia polymorpha, early-diverging moss Sphagnum compactum, and fern Ceratopteris richardii, the latter functioning as experimental control. Replicate clonal cultures were experimentally illuminated only from above, only from below, or from multiple directions, with the same near-saturation PAR level for periods brief enough to minimize nutrient limitation effects, and orientation of new growth was evaluated. For all species tested, direction of illumination exerted stronger control over gametophyte body orientation than gravity. When illuminated only from below: 1) axial Sphagnum gametophores that had initially grown into an overlying air space inverted growth by 180°, burrowing into the substrate; 2) new growth of dorsiventral Blasia, Marchantia, and Ceratopteris gametophytes-whose ventral rhizoids initially penetrated agar substrate and dorsal surfaces initially faced overlying airspace-twisted 180° so that ventral surfaces bearing rhizoids faced overlying air space and rhizoids extended into the air; and 3) Coleochaete lost typical dorsiventral organization and diagnostic dorsal hairs. Direction of illumination also exerted stronger control over orientation of liverwort new growth than surface contact did. These results indicate that early land plants likely inherited light-directed gametophyte body orientation from ancestral streptophyte algae and suggest a mechanism for reorientation of gametophyte-dominant land plants after spatial disturbance.

Determination of unknown coefficient in a non-linear elliptic problem related to the elastoplastic torsion of a bar

NASA Astrophysics Data System (ADS)

Hasanov, Alemdar; Erdem, Arzu

2008-08-01

The inverse problem of determining the unknown coefficient of the non-linear differential equation of torsional creep is studied. The unknown coefficient g = g({xi}2) depends on the gradient{xi} : = |{nabla}u| of the solution u(x), x [isin] {Omega} [sub] Rn, of the direct problem. It is proved that this gradient is bounded in C-norm. This permits one to choose the natural class of admissible coefficients for the considered inverse problem. The continuity in the norm of the Sobolev space H1({Omega}) of the solution u(x;g) of the direct problem with respect to the unknown coefficient g = g({xi}2) is obtained in the following sense: ||u(x;g) - u(x;gm)||1 [->] 0 when gm({eta}) [->] g({eta}) point-wise as m [->] {infty}. Based on these results, the existence of a quasi-solution of the inverse problem in the considered class of admissible coefficients is obtained. Numerical examples related to determination of the unknown coefficient are presented.

Direct counterfactual transmission of a quantum state

NASA Astrophysics Data System (ADS)

Li, Zheng-Hong; Al-Amri, M.; Zubairy, M. Suhail

2015-11-01

We show that an unknown quantum state can be transferred with neither quantum nor classical particle traveling in the transmission channel. Our protocol does not require prearranged entangled photon pairs and Bell measurements. By utilizing quantum Zeno effect and counterfactuality, we can entangle and disentangle a photon and an atom by nonlocal interaction. It is shown that quantum information is completely transferred from an atom to photon due to controllable disentanglement processes. There is no need to cross-check the result via classical channels.

A robust momentum management and attitude control system for the space station

NASA Technical Reports Server (NTRS)

Speyer, J. L.; Rhee, Ihnseok

1991-01-01

A game theoretic controller is synthesized for momentum management and attitude control of the Space Station in the presence of uncertainties in the moments of inertia. Full state information is assumed since attitude rates are assumed to be very assurately measured. By an input-output decomposition of the uncertainty in the system matrices, the parameter uncertainties in the dynamic system are represented as an unknown gain associated with an internal feedback loop (IFL). The input and output matrices associated with the IFL form directions through which the uncertain parameters affect system response. If the quadratic form of the IFL output augments the cost criterion, then enhanced parameter robustness is anticipated. By considering the input and the input disturbance from the IFL as two noncooperative players, a linear-quadratic differential game is constructed. The solution in the form of a linear controller is used for synthesis. Inclusion of the external disturbance torques results in a dynamic feedback controller which consists of conventional PID (proportional integral derivative) control and cyclic disturbance rejection filters. It is shown that the game theoretic design allows large variations in the inertias in directions of importance.

Robust momentum management and attitude control system for the Space Station

NASA Technical Reports Server (NTRS)

Rhee, Ihnseok; Speyer, Jason L.

1992-01-01

A game theoretic controller is synthesized for momentum management and attitude control of the Space Station in the presence of uncertainties in the moments of inertia. Full state information is assumed since attitude rates are assumed to be very accurately measured. By an input-output decomposition of the uncertainty in the system matrices, the parameter uncertainties in the dynamic system are represented as an unknown gain associated with an internal feedback loop (IFL). The input and output matrices associated with the IFL form directions through which the uncertain parameters affect system response. If the quadratic form of the IFL output augments the cost criterion, then enhanced parameter robustness is anticipated. By considering the input and the input disturbance from the IFL as two noncooperative players, a linear-quadratic differential game is constructed. The solution in the form of a linear controller is used for synthesis. Inclusion of the external disturbance torques results in a dynamic feedback controller which consists of conventional PID (proportional integral derivative) control and cyclic disturbance rejection filters. It is shown that the game theoretic design allows large variations in the inertias in directions of importance.

Emergence of polysaccharide membrane walls through macro-space partitioning via interfacial instability.

PubMed

Okeyoshi, Kosuke; Okajima, Maiko K; Kaneko, Tatsuo

2017-07-21

Living organisms in drying environments build anisotropic structures and exhibit directionality through self-organization of biopolymers. However, the process of macro-scale assembly is still unknown. Here, we introduce a dissipative structure through a non-equilibrium process between hydration and deposition in the drying of a polysaccharide liquid crystalline solution. By controlling the geometries of the evaporation front in a limited space, multiple nuclei emerge to grow vertical membrane walls with macroscopic orientation. Notably, the membranes are formed through rational orientation of rod-like microassemblies along the dynamic three-phase contact line. Additionally, in the non-equilibrium state, a dissipative structure is ultimately immobilized as a macroscopically partitioned space by multiple vertical membranes. We foresee that such oriented membranes will be applicable to soft biomaterials with direction controllability, and the macroscopic space partitionings will aid in the understanding of the space recognition ability of natural products under drying environments.

Adaptive relative pose control for autonomous spacecraft rendezvous and proximity operations with thrust misalignment and model uncertainties

NASA Astrophysics Data System (ADS)

Sun, Liang; Zheng, Zewei

2017-04-01

An adaptive relative pose control strategy is proposed for a pursue spacecraft in proximity operations on a tumbling target. Relative position vector between two spacecraft is required to direct towards the docking port of the target while the attitude of them must be synchronized. With considering the thrust misalignment of pursuer, an integrated controller for relative translational and relative rotational dynamics is developed by using norm-wise adaptive estimations. Parametric uncertainties, unknown coupled dynamics, and bounded external disturbances are compensated online by adaptive update laws. It is proved via Lyapunov stability theory that the tracking errors of relative pose converge to zero asymptotically. Numerical simulations including six degrees-of-freedom rigid body dynamics are performed to demonstrate the effectiveness of the proposed controller.

Aerial manoeuvrability in wingless gliding ants (Cephalotes atratus)

PubMed Central

Yanoviak, Stephen P.; Munk, Yonatan; Kaspari, Mike; Dudley, Robert

2010-01-01

In contrast to the patagial membranes of gliding vertebrates, the aerodynamic surfaces used by falling wingless ants to direct their aerial descent are unknown. We conducted ablation experiments to assess the relative contributions of the hindlegs, midlegs and gaster to gliding success in workers of the Neotropical arboreal ant Cephalotes atratus (Hymenoptera: Formicidae). Removal of hindlegs significantly reduced the success rate of directed aerial descent as well as the glide index for successful flights. Removal of the gaster alone did not significantly alter performance relative to controls. Equilibrium glide angles during successful targeting to vertical columns were statistically equivalent between control ants and ants with either the gaster or the hindlegs removed. High-speed video recordings suggested possible use of bilaterally asymmetric motions of the hindlegs to effect body rotations about the vertical axis during targeting manoeuvre. Overall, the control of gliding flight was remarkably robust to dramatic anatomical perturbations, suggesting effective control mechanisms in the face of adverse initial conditions (e.g. falling upside down), variable targeting decisions and turbulent wind gusts during flight. PMID:20236974

Chaos control of the brushless direct current motor using adaptive dynamic surface control based on neural network with the minimum weights.

PubMed

Luo, Shaohua; Wu, Songli; Gao, Ruizhen

2015-07-01

This paper investigates chaos control for the brushless DC motor (BLDCM) system by adaptive dynamic surface approach based on neural network with the minimum weights. The BLDCM system contains parameter perturbation, chaotic behavior, and uncertainty. With the help of radial basis function (RBF) neural network to approximate the unknown nonlinear functions, the adaptive law is established to overcome uncertainty of the control gain. By introducing the RBF neural network and adaptive technology into the dynamic surface control design, a robust chaos control scheme is developed. It is proved that the proposed control approach can guarantee that all signals in the closed-loop system are globally uniformly bounded, and the tracking error converges to a small neighborhood of the origin. Simulation results are provided to show that the proposed approach works well in suppressing chaos and parameter perturbation.

Chaos control of the brushless direct current motor using adaptive dynamic surface control based on neural network with the minimum weights

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

Luo, Shaohua; Department of Mechanical Engineering, Chongqing Aerospace Polytechnic, Chongqing, 400021; Wu, Songli

2015-07-15

This paper investigates chaos control for the brushless DC motor (BLDCM) system by adaptive dynamic surface approach based on neural network with the minimum weights. The BLDCM system contains parameter perturbation, chaotic behavior, and uncertainty. With the help of radial basis function (RBF) neural network to approximate the unknown nonlinear functions, the adaptive law is established to overcome uncertainty of the control gain. By introducing the RBF neural network and adaptive technology into the dynamic surface control design, a robust chaos control scheme is developed. It is proved that the proposed control approach can guarantee that all signals in themore » closed-loop system are globally uniformly bounded, and the tracking error converges to a small neighborhood of the origin. Simulation results are provided to show that the proposed approach works well in suppressing chaos and parameter perturbation.« less

M-MRAC Backstepping for Systems with Unknown Virtual Control Coefficients

NASA Technical Reports Server (NTRS)

Stepanyan, Vahram; Krishnakumar, Kalmanje

2015-01-01

The paper presents an over-parametrization free certainty equivalence state feedback backstepping adaptive control design method for systems of any relative degree with unmatched uncertainties and unknown virtual control coefficients. It uses a fast prediction model to estimate the unknown parameters, which is independent of the control design. It is shown that the system's input and output tracking errors can be systematically decreased by the proper choice of the design parameters. The benefits of the approach are demonstrated in numerical simulations.

Adaptive Incentive Controls for Stackelberg Games with Unknown Cost Functionals.

DTIC Science & Technology

1984-01-01

APR EZT:: F I AN 73S e OsL:-: UNCLASSI?:-- Q4~.’~- .A.., 6, *~*i i~~*~~*.- U ADAPTIVE INCENTIVE CONTROLS FOR STACKELBERG GAMES WITH UNKNOWN COST...AD-A161 885 ADAPTIVE INCENTIVE CONTROLS FOR STACKELBERG GAMES WITH i/1 UNKNOWN COST FUNCTIONALSCU) ILLINOIS UNIV AT URBANA DECISION AND CONTROL LAB T...ORGANIZATION 6b. OFFICE SYMBOL 7.. NAME OF MONITORING ORGANIZATION CoriaeLcenef~pda~ Joint Services Electronics Program Laboratory, Univ. of Illinois N/A

Rendezvous with connectivity preservation for multi-robot systems with an unknown leader

NASA Astrophysics Data System (ADS)

Dong, Yi

2018-02-01

This paper studies the leader-following rendezvous problem with connectivity preservation for multi-agent systems composed of uncertain multi-robot systems subject to external disturbances and an unknown leader, both of which are generated by a so-called exosystem with parametric uncertainty. By combining internal model design, potential function technique and adaptive control, two distributed control strategies are proposed to maintain the connectivity of the communication network, to achieve the asymptotic tracking of all the followers to the output of the unknown leader system, as well as to reject unknown external disturbances. It is also worth to mention that the uncertain parameters in the multi-robot systems and exosystem are further allowed to belong to unknown and unbounded sets when applying the second fully distributed control law containing a dynamic gain inspired by high-gain adaptive control or self-tuning regulator.

Non-predictor control of a class of feedforward nonlinear systems with unknown time-varying delays

NASA Astrophysics Data System (ADS)

Koo, Min-Sung; Choi, Ho-Lim

2016-08-01

This paper generalises the several recent results on the control of feedforward time-delay nonlinear systems. First, in view of system formulation, there are unknown time-varying delays in both states and main control input. Also, the considered nonlinear system has extended feedforward nonlinearities. Second, in view of control solution, our proposed controller is a non-predictor feedback controller whereas smith-predictor type controllers are used in the several existing results. Moreover, our controller does not need any information on the unknown delays except their upper bounds. Thus, our result has certain merits in both system formulation and control solution perspective. The analysis and example are given for clear illustration.

Simultaneous tracking and regulation visual servoing of wheeled mobile robots with uncalibrated extrinsic parameters

NASA Astrophysics Data System (ADS)

Lu, Qun; Yu, Li; Zhang, Dan; Zhang, Xuebo

2018-01-01

This paper presentsa global adaptive controller that simultaneously solves tracking and regulation for wheeled mobile robots with unknown depth and uncalibrated camera-to-robot extrinsic parameters. The rotational angle and the scaled translation between the current camera frame and the reference camera frame, as well as the ones between the desired camera frame and the reference camera frame can be calculated in real time by using the pose estimation techniques. A transformed system is first obtained, for which an adaptive controller is then designed to accomplish both tracking and regulation tasks, and the controller synthesis is based on Lyapunov's direct method. Finally, the effectiveness of the proposed method is illustrated by a simulation study.

Target Capturing Control for Space Robots with Unknown Mass Properties: A Self-Tuning Method Based on Gyros and Cameras.

PubMed

Li, Zhenyu; Wang, Bin; Liu, Hong

2016-08-30

Satellite capturing with free-floating space robots is still a challenging task due to the non-fixed base and unknown mass property issues. In this paper gyro and eye-in-hand camera data are adopted as an alternative choice for solving this problem. For this improved system, a new modeling approach that reduces the complexity of system control and identification is proposed. With the newly developed model, the space robot is equivalent to a ground-fixed manipulator system. Accordingly, a self-tuning control scheme is applied to handle such a control problem including unknown parameters. To determine the controller parameters, an estimator is designed based on the least-squares technique for identifying the unknown mass properties in real time. The proposed method is tested with a credible 3-dimensional ground verification experimental system, and the experimental results confirm the effectiveness of the proposed control scheme.

Target Capturing Control for Space Robots with Unknown Mass Properties: A Self-Tuning Method Based on Gyros and Cameras

PubMed Central

Li, Zhenyu; Wang, Bin; Liu, Hong

2016-01-01

Satellite capturing with free-floating space robots is still a challenging task due to the non-fixed base and unknown mass property issues. In this paper gyro and eye-in-hand camera data are adopted as an alternative choice for solving this problem. For this improved system, a new modeling approach that reduces the complexity of system control and identification is proposed. With the newly developed model, the space robot is equivalent to a ground-fixed manipulator system. Accordingly, a self-tuning control scheme is applied to handle such a control problem including unknown parameters. To determine the controller parameters, an estimator is designed based on the least-squares technique for identifying the unknown mass properties in real time. The proposed method is tested with a credible 3-dimensional ground verification experimental system, and the experimental results confirm the effectiveness of the proposed control scheme. PMID:27589748

Schemes for Teleportation of an Unknown Single-Qubit Quantum State by Using an Arbitrary High-Dimensional Entangled State

NASA Astrophysics Data System (ADS)

Zhan, You-Bang; Zhang, Qun-Yong; Wang, Yu-Wu; Ma, Peng-Cheng

2010-01-01

We propose a scheme to teleport an unknown single-qubit state by using a high-dimensional entangled state as the quantum channel. As a special case, a scheme for teleportation of an unknown single-qubit state via three-dimensional entangled state is investigated in detail. Also, this scheme can be directly generalized to an unknown f-dimensional state by using a d-dimensional entangled state (d > f) as the quantum channel.

Adaptive Output-Feedback Neural Control of Switched Uncertain Nonlinear Systems With Average Dwell Time.

PubMed

Long, Lijun; Zhao, Jun

2015-07-01

This paper investigates the problem of adaptive neural tracking control via output-feedback for a class of switched uncertain nonlinear systems without the measurements of the system states. The unknown control signals are approximated directly by neural networks. A novel adaptive neural control technique for the problem studied is set up by exploiting the average dwell time method and backstepping. A switched filter and different update laws are designed to reduce the conservativeness caused by adoption of a common observer and a common update law for all subsystems. The proposed controllers of subsystems guarantee that all closed-loop signals remain bounded under a class of switching signals with average dwell time, while the output tracking error converges to a small neighborhood of the origin. As an application of the proposed design method, adaptive output feedback neural tracking controllers for a mass-spring-damper system are constructed.

Direct Solve of Electrically Large Integral Equations for Problem Sizes to 1M Unknowns

NASA Technical Reports Server (NTRS)

Shaeffer, John

2008-01-01

Matrix methods for solving integral equations via direct solve LU factorization are presently limited to weeks to months of very expensive supercomputer time for problems sizes of several hundred thousand unknowns. This report presents matrix LU factor solutions for electromagnetic scattering problems for problem sizes to one million unknowns with thousands of right hand sides that run in mere days on PC level hardware. This EM solution is accomplished by utilizing the numerical low rank nature of spatially blocked unknowns using the Adaptive Cross Approximation for compressing the rank deficient blocks of the system Z matrix, the L and U factors, the right hand side forcing function and the final current solution. This compressed matrix solution is applied to a frequency domain EM solution of Maxwell's equations using standard Method of Moments approach. Compressed matrix storage and operations count leads to orders of magnitude reduction in memory and run time.

Distributed Multisensor Data Fusion under Unknown Correlation and Data Inconsistency

PubMed Central

Abu Bakr, Muhammad; Lee, Sukhan

2017-01-01

The paradigm of multisensor data fusion has been evolved from a centralized architecture to a decentralized or distributed architecture along with the advancement in sensor and communication technologies. These days, distributed state estimation and data fusion has been widely explored in diverse fields of engineering and control due to its superior performance over the centralized one in terms of flexibility, robustness to failure and cost effectiveness in infrastructure and communication. However, distributed multisensor data fusion is not without technical challenges to overcome: namely, dealing with cross-correlation and inconsistency among state estimates and sensor data. In this paper, we review the key theories and methodologies of distributed multisensor data fusion available to date with a specific focus on handling unknown correlation and data inconsistency. We aim at providing readers with a unifying view out of individual theories and methodologies by presenting a formal analysis of their implications. Finally, several directions of future research are highlighted. PMID:29077035

Band Alignment and Controllable Electron Migration between Rutile and Anatase TiO2

PubMed Central

Mi, Yang; Weng, Yuxiang

2015-01-01

TiO2 is the most promising semiconductor for photocatalytic splitting of water for hydrogen and degradation of pollutants. The highly photocatalytic active form is its mixed phase of two polymorphs anatase and rutile rather than their pristine compositions. Such a synergetic effect is understood by the staggered band alignment favorable to spatial charge separation. However, electron migration in either direction between the two phases has been reported, the reason of which is still unknown. We determined the band alignment by a novel method, i.e., transient infrared absorption-excitation energy scanning spectra, showing their conduction bands being aligned, thus the electron migration direction is controlled by dynamical factors, such as varying the particle size of anatase, putting electron or hole scavengers on either the surface of anatase or rutile phases, or both. A quantitative criterion capable of predicting the migration direction under various conditions including particle size and surface chemical reactions is proposed, the predictions have been verified experimentally in several typical cases. This would give rise to a great potential in designing more effective titania photocatalysts. PMID:26169699

Direct Interactions with the Integrin β1 Cytoplasmic Tail Activate the Abl2/Arg Kinase*

PubMed Central

Simpson, Mark A.; Bradley, William D.; Harburger, David; Parsons, Maddy; Calderwood, David A.; Koleske, Anthony J.

2015-01-01

Integrins are heterodimeric α/β extracellular matrix adhesion receptors that couple physically to the actin cytoskeleton and regulate kinase signaling pathways to control cytoskeletal remodeling and adhesion complex formation and disassembly. β1 integrins signal through the Abl2/Arg (Abl-related gene) nonreceptor tyrosine kinase to control fibroblast cell motility, neuronal dendrite morphogenesis and stability, and cancer cell invasiveness, but the molecular mechanisms by which integrin β1 activates Arg are unknown. We report here that the Arg kinase domain interacts directly with a lysine-rich membrane-proximal segment in the integrin β1 cytoplasmic tail, that Arg phosphorylates the membrane-proximal Tyr-783 in the β1 tail, and that the Arg Src homology domain then engages this phosphorylated region in the tail. We show that these interactions mediate direct binding between integrin β1 and Arg in vitro and in cells and activate Arg kinase activity. These findings provide a model for understanding how β1-containing integrins interact with and activate Abl family kinases. PMID:25694433

Protein Tyrosine Phosphatase-PEST and β8 Integrin Regulate Spatiotemporal Patterns of RhoGDI1 Activation in Migrating Cells

PubMed Central

Lee, Hye Shin; Cheerathodi, Mujeeburahiman; Chaki, Sankar P.; Reyes, Steve B.; Zheng, Yanhua; Lu, Zhimin; Paidassi, Helena; DerMardirossian, Celine; Lacy-Hulbert, Adam; Rivera, Gonzalo M.

2015-01-01

Directional cell motility is essential for normal development and physiology, although how motile cells spatiotemporally activate signaling events remains largely unknown. Here, we have characterized an adhesion and signaling unit comprised of protein tyrosine phosphatase (PTP)-PEST and the extracellular matrix (ECM) adhesion receptor β8 integrin that plays essential roles in directional cell motility. β8 integrin and PTP-PEST form protein complexes at the leading edge of migrating cells and balance patterns of Rac1 and Cdc42 signaling by controlling the subcellular localization and phosphorylation status of Rho GDP dissociation inhibitor 1 (RhoGDI1). Translocation of Src-phosphorylated RhoGDI1 to the cell's leading edge promotes local activation of Rac1 and Cdc42, whereas dephosphorylation of RhoGDI1 by integrin-bound PTP-PEST promotes RhoGDI1 release from the membrane and sequestration of inactive Rac1/Cdc42 in the cytoplasm. Collectively, these data reveal a finely tuned regulatory mechanism for controlling signaling events at the leading edge of directionally migrating cells. PMID:25666508

Fish population failure caused by an environmental estrogen is long-lasting and regulated by direct and parental effects on survival and fecundity

USGS Publications Warehouse

Schwindt, Adam R.; Winkelman, Dana L.

2013-01-01

Despite significant research demonstrating effects of estrogens such as 17α - ethinylestradiol (EE2) on fish, the underlying mechanisms regulating population failure are unknown. Projected water shortages could leave waterways increasingly dominated by wastewater effluent and understanding mechanisms is necessary for conservation and management. Here we identify mechanisms of population failure in three generations of fathead minnows including direct and parental effects on survival and fecundity. EE2 concentrations, as low as 3.2 ng/L, reduced F0 male survival to 17% and juvenile production by 40%. F1 offspring continuously exposed to EE2 failed to reproduce and offspring transferred to clean water reproduced 70 - 99% less than controls. Furthermore, survival of F2s was reduced 51% - 97% compared to controls, despite the absence of direct embryonic exposure. The indirect effect on F2 survival suggests the possibility of transgenerational effects of EE2. Our results suggest that chronically exposed populations may not be able to recover in the absence of immigration.

A time delay controller for magnetic bearings

NASA Technical Reports Server (NTRS)

Youcef-Toumi, K.; Reddy, S.

1991-01-01

The control of systems with unknown dynamics and unpredictable disturbances has raised some challenging problems. This is particularly important when high system performance needs to be guaranteed at all times. Recently, the Time Delay Control has been suggested as an alternative control scheme. The proposed control system does not require an explicit plant model nor does it depend on the estimation of specific plant parameters. Rather, it combines adaptation with past observations to directly estimate the effect of the plant dynamics. A control law is formulated for a class of dynamic systems and a sufficient condition is presented for control systems stability. The derivation is based on the bounded input-bounded output stability approach using L sub infinity function norms. The control scheme is implemented on a five degrees of freedom high speed and high precision magnetic bearing. The control performance is evaluated using step responses, frequency responses, and disturbance rejection properties. The experimental data show an excellent control performance despite the system complexity.

A recurrent neural-network-based sensor and actuator fault detection and isolation for nonlinear systems with application to the satellite's attitude control subsystem.

PubMed

Talebi, H A; Khorasani, K; Tafazoli, S

2009-01-01

This paper presents a robust fault detection and isolation (FDI) scheme for a general class of nonlinear systems using a neural-network-based observer strategy. Both actuator and sensor faults are considered. The nonlinear system considered is subject to both state and sensor uncertainties and disturbances. Two recurrent neural networks are employed to identify general unknown actuator and sensor faults, respectively. The neural network weights are updated according to a modified backpropagation scheme. Unlike many previous methods developed in the literature, our proposed FDI scheme does not rely on availability of full state measurements. The stability of the overall FDI scheme in presence of unknown sensor and actuator faults as well as plant and sensor noise and uncertainties is shown by using the Lyapunov's direct method. The stability analysis developed requires no restrictive assumptions on the system and/or the FDI algorithm. Magnetorquer-type actuators and magnetometer-type sensors that are commonly employed in the attitude control subsystem (ACS) of low-Earth orbit (LEO) satellites for attitude determination and control are considered in our case studies. The effectiveness and capabilities of our proposed fault diagnosis strategy are demonstrated and validated through extensive simulation studies.

A specific sexual orientation-related difference in navigation strategy.

PubMed

Rahman, Qazi; Andersson, Davinia; Govier, Ernest

2005-02-01

During spatial navigation, women typically navigate an environment using a landmark strategy, whereas men typically use an orientation strategy. To examine the as yet unknown effects of sexual orientation on these normative sex differences, this study required 80 healthy heterosexual and homosexual adult men and women to provide directions from experimental maps for 4 routes. The frequency and type of strategy used by each participant were computed. Expected sex differences were demonstrated, and a robust cross-sex shift was shown by homosexual men in using landmarks. This remained after controlling for differences in mental rotation, directional sense, and general intelligence. The findings may limit the number of putative neurodevelopmental pathways responsible for sex differences in navigation strategy utility. Copyright 2005 APA.

Direct medical costs of accidental falls for adults with transfemoral amputations.

PubMed

Mundell, Benjamin; Maradit Kremers, Hilal; Visscher, Sue; Hoppe, Kurtis; Kaufman, Kenton

2017-12-01

Active individuals with transfemoral amputations are provided a microprocessor-controlled knee with the belief that the prosthesis reduces their risk of falling. However, these prostheses are expensive and the cost-effectiveness is unknown with regard to falls in the transfemoral amputation population. The direct medical costs of falls in adults with transfemoral amputations need to be determined in order to assess the incremental costs and benefits of microprocessor-controlled prosthetic knees. We describe the direct medical costs of falls in adults with a transfemoral amputation. This is a retrospective, population-based, cohort study of adults who underwent transfemoral amputations between 2000 and 2014. A Bayesian structural time series approach was used to estimate cost differences between fallers and non-fallers. The mean 6-month direct medical costs of falls for six hospitalized adults with transfemoral amputations was US$25,652 (US$10,468, US$38,872). The mean costs for the 10 adults admitted to the emergency department was US$18,091 (US$-7,820, US$57,368). Falls are expensive in adults with transfemoral amputations. The 6-month costs of falls resulting in hospitalization are similar to those reported in the elderly population who are also at an increased risk of falling. Clinical relevance Estimates of fall costs in adults with transfemoral amputations can provide policy makers with additional insight when determining whether or not to cover a prescription for microprocessor-controlled prosthetic knees.

Design and experimental validation of linear and nonlinear vehicle steering control strategies

NASA Astrophysics Data System (ADS)

Menhour, Lghani; Lechner, Daniel; Charara, Ali

2012-06-01

This paper proposes the design of three control laws dedicated to vehicle steering control, two based on robust linear control strategies and one based on nonlinear control strategies, and presents a comparison between them. The two robust linear control laws (indirect and direct methods) are built around M linear bicycle models, each of these control laws is composed of two M proportional integral derivative (PID) controllers: one M PID controller to control the lateral deviation and the other M PID controller to control the vehicle yaw angle. The indirect control law method is designed using an oscillation method and a nonlinear optimisation subject to H ∞ constraint. The direct control law method is designed using a linear matrix inequality optimisation in order to achieve H ∞ performances. The nonlinear control method used for the correction of the lateral deviation is based on a continuous first-order sliding-mode controller. The different methods are designed using a linear bicycle vehicle model with variant parameters, but the aim is to simulate the nonlinear vehicle behaviour under high dynamic demands with a four-wheel vehicle model. These steering vehicle controls are validated experimentally using the data acquired using a laboratory vehicle, Peugeot 307, developed by National Institute for Transport and Safety Research - Department of Accident Mechanism Analysis Laboratory's (INRETS-MA) and their performance results are compared. Moreover, an unknown input sliding-mode observer is introduced to estimate the road bank angle.

Nitric oxide is not permissive for cutaneous active vasodilatation in humans.

PubMed

Wilkins, Brad W; Holowatz, Lacy A; Wong, Brett J; Minson, Christopher T

2003-05-01

The precise role of nitric oxide (NO) in cutaneous active vasodilatation in humans is unknown. We tested the hypothesis that NO is necessary to permit the action of an unknown vasodilator. Specifically, we investigated whether a low-dose infusion of exogenous NO, in the form of sodium nitroprusside (SNP), would fully restore vasodilatation in an area of skin in which endogenous NO was inhibited during hyperthermia. This finding would suggest a 'permissive' role for NO in active vasodilatation. Eight subjects were instrumented with three microdialysis fibres in forearm skin. Sites were randomly assigned to (1) Site A: control site; (2) Site B: NO synthase (NOS) inhibition during established hyperthermia; or (3) Site C: NOS inhibition throughout the protocol. Red blood cell flux was measured using laser-Doppler flowmetry (LDF) and cutaneous vascular conductance (CVC; LDF/mean arterial pressure) was normalized to maximal vasodilatation at each site. In Site B, NG-nitro-L-arginine methyl ester (L-NAME) infusion during hyperthermia reduced CVC by approximately 32 % (65 +/- 4 % CVCmax vs. 45 +/- 4 % CVCmax; P < 0.05). Vasodilatation was not restored to pre-NOS inhibition values in this site following low-dose SNP infusion (55 +/- 4 % CVCmax vs. 65 +/- 4 % CVCmax; P < 0.05). CVC remained significantly lower than the control site with low-dose SNP infusion in Site C (P < 0.05). The rise in CVC with low-dose SNP (deltaCVC) was significantly greater in Site B and Site C during hyperthermia compared to normothermia (P < 0.05). No difference in deltaCVC was observed between hyperthermia and normothermia in the control site (Site A). Thus, NO does not act permissively in cutaneous active vasodilatation in humans but may directly mediate vasodilatation and enhance the effect of an unknown active vasodilator.

Minimal-Approximation-Based Decentralized Backstepping Control of Interconnected Time-Delay Systems.

PubMed

Choi, Yun Ho; Yoo, Sung Jin

2016-12-01

A decentralized adaptive backstepping control design using minimal function approximators is proposed for nonlinear large-scale systems with unknown unmatched time-varying delayed interactions and unknown backlash-like hysteresis nonlinearities. Compared with existing decentralized backstepping methods, the contribution of this paper is to design a simple local control law for each subsystem, consisting of an actual control with one adaptive function approximator, without requiring the use of multiple function approximators and regardless of the order of each subsystem. The virtual controllers for each subsystem are used as intermediate signals for designing a local actual control at the last step. For each subsystem, a lumped unknown function including the unknown nonlinear terms and the hysteresis nonlinearities is derived at the last step and is estimated by one function approximator. Thus, the proposed approach only uses one function approximator to implement each local controller, while existing decentralized backstepping control methods require the number of function approximators equal to the order of each subsystem and a calculation of virtual controllers to implement each local actual controller. The stability of the total controlled closed-loop system is analyzed using the Lyapunov stability theorem.

Adaptive Neural Networks Prescribed Performance Control Design for Switched Interconnected Uncertain Nonlinear Systems.

PubMed

Li, Yongming; Tong, Shaocheng

2017-06-28

In this paper, an adaptive neural networks (NNs)-based decentralized control scheme with the prescribed performance is proposed for uncertain switched nonstrict-feedback interconnected nonlinear systems. It is assumed that nonlinear interconnected terms and nonlinear functions of the concerned systems are unknown, and also the switching signals are unknown and arbitrary. A linear state estimator is constructed to solve the problem of unmeasured states. The NNs are employed to approximate unknown interconnected terms and nonlinear functions. A new output feedback decentralized control scheme is developed by using the adaptive backstepping design technique. The control design problem of nonlinear interconnected switched systems with unknown switching signals can be solved by the proposed scheme, and only a tuning parameter is needed for each subsystem. The proposed scheme can ensure that all variables of the control systems are semi-globally uniformly ultimately bounded and the tracking errors converge to a small residual set with the prescribed performance bound. The effectiveness of the proposed control approach is verified by some simulation results.

Teleportation of a 3-dimensional GHZ State

NASA Astrophysics Data System (ADS)

Cao, Hai-Jing; Wang, Huai-Sheng; Li, Peng-Fei; Song, He-Shan

2012-05-01

The process of teleportation of a completely unknown 3-dimensional GHZ state is considered. Three maximally entangled 3-dimensional Bell states function as quantum channel in the scheme. This teleportation scheme can be directly generalized to teleport an unknown d-dimensional GHZ state.

Activation of VTA GABA neurons disrupts reward consumption

PubMed Central

van Zessen, Ruud; Phillips, Jana L.; Budygin, Evgeny A.; Stuber, Garret D.

2012-01-01

The activity of Ventral Tegmental Area (VTA) dopamine (DA) neurons promotes behavioral responses to rewards and environmental stimuli that predict them. VTA GABA inputs synapse directly onto DA neurons and may regulate DA neuronal activity to alter reward-related behaviors, however, the functional consequences of selective activation of VTA GABA neurons remains unknown. Here, we show that in vivo optogenetic activation of VTA GABA neurons disrupts reward consummatory behavior, but not conditioned anticipatory behavior in response to reward-predictive cues. In addition, direct activation of VTA GABA projections to the nucleus accumbens (NAc) resulted in detectable GABA release, but did not alter reward consumption. Furthermore, optogenetic stimulation of VTA GABA neurons directly suppressed the activity and excitability of neighboring DA neurons, as well as the release of DA in the NAc, suggesting that the dynamic interplay between VTA DA and GABA neurons can control the initiation and termination of reward-related behaviors. PMID:22445345

Deletion of the Tail Domain of the Kinesin-5 Cin8 Affects Its Directionality*

PubMed Central

Düselder, André; Fridman, Vladimir; Thiede, Christina; Wiesbaum, Alice; Goldstein, Alina; Klopfenstein, Dieter R.; Zaitseva, Olga; Janson, Marcel E.; Gheber, Larisa; Schmidt, Christoph F.

2015-01-01

The bipolar kinesin-5 motors are one of the major players that govern mitotic spindle dynamics. Their bipolar structure enables them to cross-link and slide apart antiparallel microtubules (MTs) emanating from the opposing spindle poles. The budding yeast kinesin-5 Cin8 was shown to switch from fast minus-end- to slow plus-end-directed motility upon binding between antiparallel MTs. This unexpected finding revealed a new dimension of cellular control of transport, the mechanism of which is unknown. Here we have examined the role of the C-terminal tail domain of Cin8 in regulating directionality. We first constructed a stable dimeric Cin8/kinesin-1 chimera (Cin8Kin), consisting of head and neck linker of Cin8 fused to the stalk of kinesin-1. As a single dimeric motor, Cin8Kin switched frequently between plus and minus directionality along single MTs, demonstrating that the Cin8 head domains are inherently bidirectional, but control over directionality was lost. We next examined the activity of a tetrameric Cin8 lacking only the tail domains (Cin8Δtail). In contrast to wild-type Cin8, the motility of single molecules of Cin8Δtail in high ionic strength was slow and bidirectional, with almost no directionality switches. Cin8Δtail showed only a weak ability to cross-link MTs in vitro. In vivo, Cin8Δtail exhibited bias toward the plus-end of the MTs and was unable to support viability of cells as the sole kinesin-5 motor. We conclude that the tail of Cin8 is not necessary for bidirectional processive motion, but is controlling the switch between plus- and minus-end-directed motility. PMID:25991727

Reach and grasp by people with tetraplegia using a neurally controlled robotic arm

PubMed Central

Hochberg, Leigh R.; Bacher, Daniel; Jarosiewicz, Beata; Masse, Nicolas Y.; Simeral, John D.; Vogel, Joern; Haddadin, Sami; Liu, Jie; Cash, Sydney S.; van der Smagt, Patrick; Donoghue, John P.

2012-01-01

Paralysis following spinal cord injury (SCI), brainstem stroke, amyotrophic lateral sclerosis (ALS) and other disorders can disconnect the brain from the body, eliminating the ability to carry out volitional movements. A neural interface system (NIS)1–5 could restore mobility and independence for people with paralysis by translating neuronal activity directly into control signals for assistive devices. We have previously shown that people with longstanding tetraplegia can use an NIS to move and click a computer cursor and to control physical devices6–8. Able-bodied monkeys have used an NIS to control a robotic arm9, but it is unknown whether people with profound upper extremity paralysis or limb loss could use cortical neuronal ensemble signals to direct useful arm actions. Here, we demonstrate the ability of two people with long-standing tetraplegia to use NIS-based control of a robotic arm to perform three-dimensional reach and grasp movements. Participants controlled the arm over a broad space without explicit training, using signals decoded from a small, local population of motor cortex (MI) neurons recorded from a 96-channel microelectrode array. One of the study participants, implanted with the sensor five years earlier, also used a robotic arm to drink coffee from a bottle. While robotic reach and grasp actions were not as fast or accurate as those of an able-bodied person, our results demonstrate the feasibility for people with tetraplegia, years after CNS injury, to recreate useful multidimensional control of complex devices directly from a small sample of neural signals. PMID:22596161

Approximation-based adaptive tracking control of pure-feedback nonlinear systems with multiple unknown time-varying delays.

PubMed

Wang, Min; Ge, Shuzhi Sam; Hong, Keum-Shik

2010-11-01

This paper presents adaptive neural tracking control for a class of non-affine pure-feedback systems with multiple unknown state time-varying delays. To overcome the design difficulty from non-affine structure of pure-feedback system, mean value theorem is exploited to deduce affine appearance of state variables x(i) as virtual controls α(i), and of the actual control u. The separation technique is introduced to decompose unknown functions of all time-varying delayed states into a series of continuous functions of each delayed state. The novel Lyapunov-Krasovskii functionals are employed to compensate for the unknown functions of current delayed state, which is effectively free from any restriction on unknown time-delay functions and overcomes the circular construction of controller caused by the neural approximation of a function of u and [Formula: see text] . Novel continuous functions are introduced to overcome the design difficulty deduced from the use of one adaptive parameter. To achieve uniformly ultimate boundedness of all the signals in the closed-loop system and tracking performance, control gains are effectively modified as a dynamic form with a class of even function, which makes stability analysis be carried out at the present of multiple time-varying delays. Simulation studies are provided to demonstrate the effectiveness of the proposed scheme.

Input reconstruction for networked control systems subject to deception attacks and data losses on control signals

NASA Astrophysics Data System (ADS)

Keller, J. Y.; Chabir, K.; Sauter, D.

2016-03-01

State estimation of stochastic discrete-time linear systems subject to unknown inputs or constant biases has been widely studied but no work has been dedicated to the case where a disturbance switches between unknown input and constant bias. We show that such disturbance can affect a networked control system subject to deception attacks and data losses on the control signals transmitted by the controller to the plant. This paper proposes to estimate the switching disturbance from an augmented state version of the intermittent unknown input Kalman filter recently developed by the authors. Sufficient stochastic stability conditions are established when the arrival binary sequence of data losses follows a Bernoulli random process.

Improved mapping of radio sources from VLBI data by least-square fit

NASA Technical Reports Server (NTRS)

Rodemich, E. R.

1985-01-01

A method is described for producing improved mapping of radio sources from Very Long Base Interferometry (VLBI) data. The method described is more direct than existing Fourier methods, is often more accurate, and runs at least as fast. The visibility data is modeled here, as in existing methods, as a function of the unknown brightness distribution and the unknown antenna gains and phases. These unknowns are chosen so that the resulting function values are as near as possible to the observed values. If researchers use the radio mapping source deviation to measure the closeness of this fit to the observed values, they are led to the problem of minimizing a certain function of all the unknown parameters. This minimization problem cannot be solved directly, but it can be attacked by iterative methods which we show converge automatically to the minimum with no user intervention. The resulting brightness distribution will furnish the best fit to the data among all brightness distributions of given resolution.

Direct energy balance based active disturbance rejection control for coal-fired power plant.

PubMed

Sun, Li; Hua, Qingsong; Li, Donghai; Pan, Lei; Xue, Yali; Lee, Kwang Y

2017-09-01

The conventional direct energy balance (DEB) based PI control can fulfill the fundamental tracking requirements of the coal-fired power plant. However, it is challenging to deal with the cases when the coal quality variation is present. To this end, this paper introduces the active disturbance rejection control (ADRC) to the DEB structure, where the coal quality variation is deemed as a kind of unknown disturbance that can be estimated and mitigated promptly. Firstly, the nonlinearity of a recent power plant model is analyzed based on the gap metric, which provides guidance on how to set the pressure set-point in line with the power demand. Secondly, the approximate decoupling effect of the DEB structure is analyzed based on the relative gain analysis in frequency domain. Finally, the synthesis of the DEB based ADRC control system is carried out based on multi-objective optimization. The optimized ADRC results show that the integrated absolute error (IAE) indices of the tracking performances in both loops can be simultaneously improved, in comparison with the DEB based PI control and H ∞ control system. The regulation performance in the presence of the coal quality variation is significantly improved under the ADRC control scheme. Moreover, the robustness of the proposed strategy is shown comparable with the H ∞ control. Copyright © 2017. Published by Elsevier Ltd.

Dual RBFNNs-Based Model-Free Adaptive Control With Aspen HYSYS Simulation.

PubMed

Zhu, Yuanming; Hou, Zhongsheng; Qian, Feng; Du, Wenli

2017-03-01

In this brief, we propose a new data-driven model-free adaptive control (MFAC) method with dual radial basis function neural networks (RBFNNs) for a class of discrete-time nonlinear systems. The main novelty lies in that it provides a systematic design method for controller structure by the direct usage of I/O data, rather than using the first-principle model or offline identified plant model. The controller structure is determined by equivalent-dynamic-linearization representation of the ideal nonlinear controller, and the controller parameters are tuned by the pseudogradient information extracted from the I/O data of the plant, which can deal with the unknown nonlinear system. The stability of the closed-loop control system and the stability of the training process for RBFNNs are guaranteed by rigorous theoretical analysis. Meanwhile, the effectiveness and the applicability of the proposed method are further demonstrated by the numerical example and Aspen HYSYS simulation of distillation column in crude styrene produce process.

MyD88 signaling in T cells directs IgA-mediated control of the microbiota to promote health

PubMed Central

Kubinak, Jason L.; Petersen, Charisse; Stephens, W. Zac; Soto, Ray; Bake, Erin; O’Connell, Ryan M.; Round, June L.

2015-01-01

SUMMARY Altered commensal communities are associated with human disease. IgA mediates intestinal homeostasis and regulates microbiota composition. Intestinal IgA is produced at high levels as a result of T follicular helper cell (TFH) and B cell interactions in germinal centers. However, the pathways directing host IgA responses towards the microbiota remain unknown. Here, we report that signaling through the innate adaptor MyD88 in gut T cells coordinates germinal center responses, including TFH and IgA+ B cell development. TFH development is deficient in germfree mice and can be restored by feeding TLR2 agonists that activate T cell intrinsic MyD88 signaling. Loss of this pathway diminishes high affinity IgA targeting of the microbiota and fails to control the bacterial community, leading to worsened disease. Our findings identify that T cells converge innate and adaptive immune signals to coordinate IgA against the microbiota, constraining microbial community membership to promote symbiosis. PMID:25620548

New modules are added to vibrissal premotor circuitry with the emergence of exploratory whisking

PubMed Central

Takatoh, Jun; Nelson, Anders; Zhou, Xiang; Bolton, M. McLean; Ehlers, Michael D.; Arenkiel, Benjamin R.; Mooney, Richard; Wang, Fan

2012-01-01

SUMMARY Rodents begin to use bilaterally coordinated, rhythmic sweeping of their vibrissae (“whisking”) for environmental exploration around two weeks after birth. Whether and how vibrissal control circuitry changes after birth is unknown, and relevant premotor circuitry remains poorly characterized. Using a modified rabies virus transsynaptic tracing strategy, we labeled neurons synapsing directly onto vibrissa facial motor neurons (vFMNs). Sources of potential excitatory, inhibitory, and modulatory vFMN premotor neurons, and differences between the premotor circuitry for vFMNs innervating intrinsic versus extrinsic vibrissal muscles, were systematically characterized. The emergence of whisking is accompanied by the addition of “new” sets of bilateral excitatory inputs to vFMNs from neurons in the lateral paragigantocellularis (LPGi). Furthermore, descending axons from the motor cortex directly innervate LPGi premotor neurons. Thus, neural modules well suited to facilitate the bilateral coordination and cortical control of whisking are added to premotor circuitry in parallel with the emergence of this exploratory behavior. PMID:23352170

Complete synchronization of uncertain chaotic systems via a single proportional adaptive controller: A comparative study

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

Ahmad, Israr, E-mail: iak-2000plus@yahoo.com; Saaban, Azizan Bin, E-mail: azizan.s@uum.edu.my; Ibrahim, Adyda Binti, E-mail: adyda@uum.edu.my

This paper addresses a comparative computational study on the synchronization quality, cost and converging speed for two pairs of identical chaotic and hyperchaotic systems with unknown time-varying parameters. It is assumed that the unknown time-varying parameters are bounded. Based on the Lyapunov stability theory and using the adaptive control method, a single proportional controller is proposed to achieve the goal of complete synchronizations. Accordingly, appropriate adaptive laws are designed to identify the unknown time-varying parameters. The designed control strategy is easy to implement in practice. Numerical simulations results are provided to verify the effectiveness of the proposed synchronization scheme.

Discrete-time switching periodic adaptive control for time-varying parameters with unknown periodicity

NASA Astrophysics Data System (ADS)

Yu, Miao; Huang, Deqing; Yang, Wanqiu

2018-06-01

In this paper, we address the problem of unknown periodicity for a class of discrete-time nonlinear parametric systems without assuming any growth conditions on the nonlinearities. The unknown periodicity hides in the parametric uncertainties, which is difficult to estimate with existing techniques. By incorporating a logic-based switching mechanism, we identify the period and bound of unknown parameter simultaneously. Lyapunov-based analysis is given to demonstrate that a finite number of switchings can guarantee the asymptotic tracking for the nonlinear parametric systems. The simulation result also shows the efficacy of the proposed switching periodic adaptive control approach.

Dynamic modelling and adaptive robust tracking control of a space robot with two-link flexible manipulators under unknown disturbances

NASA Astrophysics Data System (ADS)

Yang, Xinxin; Ge, Shuzhi Sam; He, Wei

2018-04-01

In this paper, both the closed-form dynamics and adaptive robust tracking control of a space robot with two-link flexible manipulators under unknown disturbances are developed. The dynamic model of the system is described with assumed modes approach and Lagrangian method. The flexible manipulators are represented as Euler-Bernoulli beams. Based on singular perturbation technique, the displacements/joint angles and flexible modes are modelled as slow and fast variables, respectively. A sliding mode control is designed for trajectories tracking of the slow subsystem under unknown but bounded disturbances, and an adaptive sliding mode control is derived for slow subsystem under unknown slowly time-varying disturbances. An optimal linear quadratic regulator method is proposed for the fast subsystem to damp out the vibrations of the flexible manipulators. Theoretical analysis validates the stability of the proposed composite controller. Numerical simulation results demonstrate the performance of the closed-loop flexible space robot system.

The Developmental Regulator SEEDSTICK Controls Structural and Mechanical Properties of the Arabidopsis Seed Coat

PubMed Central

Beauzamy, Léna; Caporali, Elisabetta; Koroney, Abdoul-Salam

2016-01-01

Although many transcription factors involved in cell wall morphogenesis have been identified and studied, it is still unknown how genetic and molecular regulation of cell wall biosynthesis is integrated into developmental programs. We demonstrate by molecular genetic studies that SEEDSTICK (STK), a transcription factor controlling ovule and seed integument identity, directly regulates PMEI6 and other genes involved in the biogenesis of the cellulose-pectin matrix of the cell wall. Based on atomic force microscopy, immunocytochemistry, and chemical analyses, we propose that structural modifications of the cell wall matrix in the stk mutant contribute to defects in mucilage release and seed germination under water-stress conditions. Our studies reveal a molecular network controlled by STK that regulates cell wall properties of the seed coat, demonstrating that developmental regulators controlling organ identity also coordinate specific aspects of cell wall characteristics. PMID:27624758

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

Scheinker, Alexander

Here, we study control of the angular-velocity actuated nonholonomic unicycle, via a simple, bounded extremum seeking controller which is robust to external disturbances and measurement noise. The vehicle performs source seeking despite not having any position information about itself or the source, able only to sense a noise corrupted scalar value whose extremum coincides with the unknown source location. In order to control the angular velocity, rather than the angular heading directly, a controller is developed such that the closed loop system exhibits multiple time scales and requires an analysis approach expanding the previous work of Kurzweil, Jarnik, Sussmann, andmore » Liu, utilizing weak limits. We provide analytic proof of stability and demonstrate how this simple scheme can be extended to include position-independent source seeking, tracking, and collision avoidance of groups on autonomous vehicles in GPS-denied environments, based only on a measure of distance to an obstacle, which is an especially important feature for an autonomous agent.« less

Distributed Adaptive Fuzzy Control for Nonlinear Multiagent Systems Via Sliding Mode Observers.

PubMed

Shen, Qikun; Shi, Peng; Shi, Yan

2016-12-01

In this paper, the problem of distributed adaptive fuzzy control is investigated for high-order uncertain nonlinear multiagent systems on directed graph with a fixed topology. It is assumed that only the outputs of each follower and its neighbors are available in the design of its distributed controllers. Equivalent output injection sliding mode observers are proposed for each follower to estimate the states of itself and its neighbors, and an observer-based distributed adaptive controller is designed for each follower to guarantee that it asymptotically synchronizes to a leader with tracking errors being semi-globally uniform ultimate bounded, in which fuzzy logic systems are utilized to approximate unknown functions. Based on algebraic graph theory and Lyapunov function approach, using Filippov-framework, the closed-loop system stability analysis is conducted. Finally, numerical simulations are provided to illustrate the effectiveness and potential of the developed design techniques.

Adaptive output feedback control of uncertain nonlinear systems using single-hidden-layer neural networks.

PubMed

Hovakimyan, N; Nardi, F; Calise, A; Kim, Nakwan

2002-01-01

We consider adaptive output feedback control of uncertain nonlinear systems, in which both the dynamics and the dimension of the regulated system may be unknown. However, the relative degree of the regulated output is assumed to be known. Given a smooth reference trajectory, the problem is to design a controller that forces the system measurement to track it with bounded errors. The classical approach requires a state observer. Finding a good observer for an uncertain nonlinear system is not an obvious task. We argue that it is sufficient to build an observer for the output tracking error. Ultimate boundedness of the error signals is shown through Lyapunov's direct method. The theoretical results are illustrated in the design of a controller for a fourth-order nonlinear system of relative degree two and a high-bandwidth attitude command system for a model R-50 helicopter.

Neurobiology of Self-Awareness in Schizophrenia: an fMRI Study

PubMed Central

Shad, Mujeeb U.; Keshavan, Matcheri S.; Steinberg, Joel L.; Mihalakos, Perry; Thomas, Binu P.; Motes, Michael A.; Soares, Jair C.; Tamminga, Carol A.

2012-01-01

Self-awareness (SA) is one of the core domains of higher cortical functions and is frequently compromised in schizophrenia. Deficits in SA have been associated with functional and psychosocial impairment in this patient population. However, despite its clinical significance, only a few studies have examined the neural substrates of self-referential processing in schizophrenia. The aim of this study was to assess self-awareness in schizophrenia using a functional magnetic resonance imaging (fMRI) paradigm designed to elicit judgments of self-reference in a simulated social context. While scanned, volunteers looked at visually-displayed sentences that had the volunteer’s own first name (self-directed sentence-stimulus) or an unknown other person’s first name (other-directed sentence stimulus) as the grammatical subject of the sentence. The volunteers were asked to discern whether each sentence-stimulus was about the volunteer personally (during a self-referential cue epoch) or asked whether each statement was about someone else (during an other-referential cue epoch). We predicted that individuals with schizophrenia would demonstrate altered functional activation to self- and other-directed sentence-stimuli as compared to controls. Fifteen controls and seventeen schizophrenia volunteers completed clinical assessments and SA fMRI task on a 3T Philips 3.0 T Achieva system. The results showed significantly greater activation in schizophrenia compared to controls for cortical midline structures in response to self- vs. other-directed sentence-stimuli. These findings support results from earlier studies and demonstrate selective alteration in the activation of cortical midline structures associated with evaluations of self-reference in schizophrenia as compared to controls. PMID:22480958

Neurobiology of self-awareness in schizophrenia: an fMRI study.

PubMed

Shad, Mujeeb U; Keshavan, Matcheri S; Steinberg, Joel L; Mihalakos, Perry; Thomas, Binu P; Motes, Michael A; Soares, Jair C; Tamminga, Carol A

2012-07-01

Self-awareness (SA) is one of the core domains of higher cortical functions and is frequently compromised in schizophrenia. Deficits in SA have been associated with functional and psychosocial impairment in this patient population. However, despite its clinical significance, only a few studies have examined the neural substrates of self-referential processing in schizophrenia. The aim of this study was to assess self-awareness in schizophrenia using a functional magnetic resonance imaging (fMRI) paradigm designed to elicit judgments of self-reference in a simulated social context. While scanned, volunteers looked at visually-displayed sentences that had the volunteer's own first name (self-directed sentence-stimulus) or an unknown other person's first name (other-directed sentence stimulus) as the grammatical subject of the sentence. The volunteers were asked to discern whether each sentence-stimulus was about the volunteer personally (during a self-referential cue epoch) or asked whether each statement was about someone else (during an other-referential cue epoch). We predicted that individuals with schizophrenia would demonstrate altered functional activation to self- and other-directed sentence-stimuli as compared to controls. Fifteen controls and seventeen schizophrenia volunteers completed clinical assessments and SA fMRI task on a 3T Philips 3.0 T Achieva system. The results showed significantly greater activation in schizophrenia compared to controls for cortical midline structures in response to self- vs. other-directed sentence-stimuli. These findings support results from earlier studies and demonstrate selective alteration in the activation of cortical midline structures associated with evaluations of self-reference in schizophrenia as compared to controls. Copyright © 2012 Elsevier B.V. All rights reserved.

Optimal thrust level for orbit insertion

NASA Astrophysics Data System (ADS)

Cerf, Max

2017-07-01

The minimum-fuel orbital transfer is analyzed in the case of a launcher upper stage using a constantly thrusting engine. The thrust level is assumed to be constant and its value is optimized together with the thrust direction. A closed-loop solution for the thrust direction is derived from the extremal analysis for a planar orbital transfer. The optimal control problem reduces to two unknowns, namely the thrust level and the final time. Guessing and propagating the costates is no longer necessary and the optimal trajectory is easily found from a rough initialization. On the other hand the initial costates are assessed analytically from the initial conditions and they can be used as initial guess for transfers at different thrust levels. The method is exemplified on a launcher upper stage targeting a geostationary transfer orbit.

Referrals in Primary Care: Is the Family Physician a “Gatekeeper”?

PubMed Central

Norton, Peter G.; Dunn, Earl V.; Bestvater, David

1989-01-01

The increasing financial restraints on the use of health care resources make it important to examine the appropriateness of present usage patterns. The authors studied referral patterns for a group of academic family physicians practising in a health service organization in Ontario. They found that for all consultant encounters, the family physician directly controlled 65% of these consultations, whereas 13% were continuing consultations with the specialist without direct family physician referral. The remainder were either unknown or referred from other sources, for example, emergency room or specialist-to-specialist referrals. The family physician made the exact same diagnosis as the consultant in 73.4% of cases for which data were available, and the patient was referred to an inappropriate specialist in only 2.7% of cases. PMID:21249055

Factors associated with positive direct antiglobulin tests in pretransfusion patients: a case-control study.

PubMed

Toy, P T; Chin, C A; Reid, M E; Burns, M A

1985-01-01

During routine pretransfusion testing, the presence of IgG on patient red cells is suggested by a positive autocontrol and confirmed by a positive direct antiglobulin test (DAT) using monospecific anti-IgG sera. Most IgG on patient red cells detected in this manner are of unknown etiology. We recently showed an association between elevated serum globulin levels and positive DAT with unreactive eluate in patients with acquired immunodeficiency syndrome (AIDS). In the present study, we wished to determine whether elevated serum globulin levels contribute to some of the positive DAT encountered in pretransfusion testing of patients without AIDS. 76 patients with positive DAT were compared with 90 controls without IgG detected on their red cells during pretransfusion testing. The rate of elevated serum globulin levels was 75% in positive DAT cases versus 29% in controls (p less than 0.001); the odds ratio was 7.6. Elevated blood urea nitrogen levels occurred in 42% of cases versus 19% of controls (p less than 0.025); the odds ratio was 3.1. Cases and controls were not significantly different with regard to age, sex, race, quinidine usage, or hyperalimentation. Elevated serum globulin and blood urea nitrogen levels are significantly associated with a positive DAT with unreactive eluate in pretransfusion patients.

Attitude and Intention Regarding Pain Management among Chinese Nursing Students: A Cross-Sectional Questionnaire Survey.

PubMed

Fang, Liang-Yu; Xu, Yin-Chuan; Lin, Dan-Ni; Jin, Jing-Feng; Yan, Min

2017-08-01

Optimal pain management is a priority in effective nursing care. Lack of sufficient pain knowledge associated with inadequate pain management has been proved. However, the intention, defined as the predictor of behavior, regarding pain management remains unknown. Therefore, the study was to determine the attitude and intention regarding pain management among Chinese nursing students and investigate the underlying determinants and their interactions in terms of intention toward pain management. The Pain Management Survey Questionnaire, comprising the key determinants of the theory of planned behavior-that is, direct attitude, belief-based intention, subjective norm, direct control, and indirect control-was used to collect data from 512 nursing students who undertook clinical rotation in an affiliated hospital of a medical college in China. Data were analyzed using descriptive statistics, independent sample t test, Pearson correlation analysis, or structural equation modeling analysis. Chinese nursing students reported negative attitudes and behavioral intentions toward pain management. Direct control, subjective norm, belief-based attitude, and indirect control independently predicted nursing students' intention to treat patients with pain. Direct control was the strongest predictor. Structural equation modeling analysis further revealed 39.84% of the variance associated with intention that could be explained by determinants of the theory of planned behavior. Additionally, educational school level and previous pain management training had great effects on pain management intention. Overall, this study identified intention as an important factor in effective pain treatment. Chinese nursing students have negative attitudes and insufficient intention to pain management. Therefore, hospitals and universities in China should manage these factors to improve nursing students' practice regarding pain management. Copyright © 2017 American Society for Pain Management Nursing. Published by Elsevier Inc. All rights reserved.

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

Pin, F.G.; Bender, S.R.

Most fuzzy logic-based reasoning schemes developed for robot control are fully reactive, i.e., the reasoning modules consist of fuzzy rule bases that represent direct mappings from the stimuli provided by the perception systems to the responses implemented by the motion controllers. Due to their totally reactive nature, such reasoning systems can encounter problems such as infinite loops and limit cycles. In this paper, we proposed an approach to remedy these problems by adding a memory and memory-related behaviors to basic reactive systems. Three major types of memory behaviors are addressed: memory creation, memory management, and memory utilization. These are firstmore » presented, and examples of their implementation for the recognition of limit cycles during the navigation of an autonomous robot in a priori unknown environments are then discussed.« less

Adaptive fuzzy dynamic surface control for the chaotic permanent magnet synchronous motor using Nussbaum gain

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

Luo, Shaohua

This paper is concerned with the problem of adaptive fuzzy dynamic surface control (DSC) for the permanent magnet synchronous motor (PMSM) system with chaotic behavior, disturbance and unknown control gain and parameters. Nussbaum gain is adopted to cope with the situation that the control gain is unknown. And the unknown items can be estimated by fuzzy logic system. The proposed controller guarantees that all the signals in the closed-loop system are bounded and the system output eventually converges to a small neighborhood of the desired reference signal. Finally, the numerical simulations indicate that the proposed scheme can suppress the chaosmore » of PMSM and show the effectiveness and robustness of the proposed method.« less

Adaptive fuzzy dynamic surface control for the chaotic permanent magnet synchronous motor using Nussbaum gain.

PubMed

Luo, Shaohua

2014-09-01

This paper is concerned with the problem of adaptive fuzzy dynamic surface control (DSC) for the permanent magnet synchronous motor (PMSM) system with chaotic behavior, disturbance and unknown control gain and parameters. Nussbaum gain is adopted to cope with the situation that the control gain is unknown. And the unknown items can be estimated by fuzzy logic system. The proposed controller guarantees that all the signals in the closed-loop system are bounded and the system output eventually converges to a small neighborhood of the desired reference signal. Finally, the numerical simulations indicate that the proposed scheme can suppress the chaos of PMSM and show the effectiveness and robustness of the proposed method.

Epidemiology of neuroendocrine cancers in an Australian population.

PubMed

Luke, Colin; Price, Timothy; Townsend, Amanda; Karapetis, Christos; Kotasek, Dusan; Singhal, Nimit; Tracey, Elizabeth; Roder, David

2010-06-01

The aim was to explore incidence, mortality and case survivals for invasive neuroendocrine cancers in an Australian population and consider cancer control implications. Directly age-standardised incidence and mortality rates were investigated from 1980 to 2006, plus disease-specific survivals. Annual incidence per 100,000 increased from 1.7 in 1980-1989 to 3.3 in 2000-2006. A corresponding mortality increase was not observed, although numbers of deaths were low, reducing statistical power. Increases in incidence affected both sexes and were more evident for female lung, large bowel (excluding appendix), and unknown primary site. Common sites were lung (25.9%), large bowel (23.3%) (40.9% were appendix), small intestine (20.6%), unknown primary (15.0%), pancreas (6.5%), and stomach (3.7%). Site distribution did not vary by sex (p = 0.260). Younger ages at diagnosis applied for lung (p = 0.002) and appendix (p < 0.001) and older ages for small intestine (p < 0.001) and unknown primary site (p < 0.001). Five-year survival was 68.5% for all sites combined, with secular increases (p < 0.001). After adjusting for age and diagnostic period, survivals were higher for appendix and lower for unknown primary site, pancreas, and colon (excluding appendix). Incidence rates are increasing. Research is needed into possible aetiological factors for lung and large-bowel sites, including tobacco smoking, and excess body weight and lack of exercise, respectively; and Crohn's disease as a possible precursor condition.

Learning-by-catching: uncertain invasive-species populations and the value of information.

PubMed

D'Evelyn, Sean T; Tarui, Nori; Burnett, Kimberly; Roumasset, James A

2008-12-01

This paper develops a model of invasive species control when the species' population size is unknown. In the face of an uncertain population size, a resource manager's species-control efforts provide two potential benefits: (1) a direct benefit of possibly reducing the population of invasive species, and (2) an indirect benefit of information acquisition (due to learning about the population size, which reduces uncertainty). We provide a methodology that takes into account both of these benefits, and show how optimal management decisions are altered in the presence of the indirect benefit of learning. We then apply this methodology to the case of controlling the Brown Treesnake (Boiga irregularis) on the island of Saipan. We find that the indirect benefit--the value of information to reduce uncertainty--is likely to be quite large.

Amyloid Precursor Protein (APP) Mediated Regulation of Ganglioside Homeostasis Linking Alzheimer's Disease Pathology with Ganglioside Metabolism

PubMed Central

Grimm, Marcus O. W.; Zinser, Eva G.; Grösgen, Sven; Hundsdörfer, Benjamin; Rothhaar, Tatjana L.; Burg, Verena K.; Kaestner, Lars; Bayer, Thomas A.; Lipp, Peter; Müller, Ulrike; Grimm, Heike S.; Hartmann, Tobias

2012-01-01

Gangliosides are important players for controlling neuronal function and are directly involved in AD pathology. They are among the most potent stimulators of Aβ production, are enriched in amyloid plaques and bind amyloid beta (Aβ). However, the molecular mechanisms linking gangliosides with AD are unknown. Here we identified the previously unknown function of the amyloid precursor protein (APP), specifically its cleavage products Aβ and the APP intracellular domain (AICD), of regulating GD3-synthase (GD3S). Since GD3S is the key enzyme converting a- to b-series gangliosides, it therefore plays a major role in controlling the levels of major brain gangliosides. This regulation occurs by two separate and additive mechanisms. The first mechanism directly targets the enzymatic activity of GD3S: Upon binding of Aβ to the ganglioside GM3, the immediate substrate of the GD3S, enzymatic turnover of GM3 by GD3S was strongly reduced. The second mechanism targets GD3S expression. APP cleavage results, in addition to Aβ release, in the release of AICD, a known candidate for gene transcriptional regulation. AICD strongly down regulated GD3S transcription and knock-in of an AICD deletion mutant of APP in vivo, or knock-down of Fe65 in neuroblastoma cells, was sufficient to abrogate normal GD3S functionality. Equally, knock-out of the presenilin genes, presenilin 1 and presenilin 2, essential for Aβ and AICD production, or of APP itself, increased GD3S activity and expression and consequently resulted in a major shift of a- to b-series gangliosides. In addition to GD3S regulation by APP processing, gangliosides in turn altered APP cleavage. GM3 decreased, whereas the ganglioside GD3, the GD3S product, increased Aβ production, resulting in a regulatory feedback cycle, directly linking ganglioside metabolism with APP processing and Aβ generation. A central aspect of this homeostatic control is the reduction of GD3S activity via an Aβ-GM3 complex and AICD-mediated repression of GD3S transcription. PMID:22470521

Reachable set estimation for Takagi-Sugeno fuzzy systems against unknown output delays with application to tracking control of AUVs.

PubMed

Zhong, Zhixiong; Zhu, Yanzheng; Ahn, Choon Ki

2018-07-01

In this paper, we address the problem of reachable set estimation for continuous-time Takagi-Sugeno (T-S) fuzzy systems subject to unknown output delays. Based on the reachable set concept, a new controller design method is also discussed for such systems. An effective method is developed to attenuate the negative impact from the unknown output delays, which likely degrade the performance/stability of systems. First, an augmented fuzzy observer is proposed to capacitate a synchronous estimation for the system state and the disturbance term owing to the unknown output delays, which ensures that the reachable set of the estimation error is limited via the intersection operation of ellipsoids. Then, a compensation technique is employed to eliminate the influence on the system performance stemmed from the unknown output delays. Finally, the effectiveness and correctness of the obtained theories are verified by the tracking control of autonomous underwater vehicles. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Detecting fission from special nuclear material sources

DOEpatents

Rowland, Mark S [Alamo, CA; Snyderman, Neal J [Berkeley, CA

2012-06-05

A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. The system includes a graphing component that displays the plot of the neutron distribution from the unknown source over a Poisson distribution and a plot of neutrons due to background or environmental sources. The system further includes a known neutron source placed in proximity to the unknown source to actively interrogate the unknown source in order to accentuate differences in neutron emission from the unknown source from Poisson distributions and/or environmental sources.

Model-free adaptive sliding mode controller design for generalized projective synchronization of the fractional-order chaotic system via radial basis function neural networks

NASA Astrophysics Data System (ADS)

Wang, L. M.

2017-09-01

A novel model-free adaptive sliding mode strategy is proposed for a generalized projective synchronization (GPS) between two entirely unknown fractional-order chaotic systems subject to the external disturbances. To solve the difficulties from the little knowledge about the master-slave system and to overcome the bad effects of the external disturbances on the generalized projective synchronization, the radial basis function neural networks are used to approach the packaged unknown master system and the packaged unknown slave system (including the external disturbances). Consequently, based on the slide mode technology and the neural network theory, a model-free adaptive sliding mode controller is designed to guarantee asymptotic stability of the generalized projective synchronization error. The main contribution of this paper is that a control strategy is provided for the generalized projective synchronization between two entirely unknown fractional-order chaotic systems subject to the unknown external disturbances, and the proposed control strategy only requires that the master system has the same fractional orders as the slave system. Moreover, the proposed method allows us to achieve all kinds of generalized projective chaos synchronizations by turning the user-defined parameters onto the desired values. Simulation results show the effectiveness of the proposed method and the robustness of the controlled system.

Competence to Complete Psychiatric Advance Directives: Effects of Facilitated Decision Making

PubMed Central

Swanson, Jeffrey W.; Appelbaum, Paul S.; Swartz, Marvin S.; Ferron, Joelle; Van Dorn, Richard A.; Wagner, H. Ryan

2013-01-01

Psychiatric advance directives (PADs) statutes presume competence to complete these documents, but the range and dimensions of decisional competence among people who actually complete PADs is unknown. This study examines clinical and neuropsychological correlates of performance on a measure to assess competence to complete PADs and investigates the effects of a facilitated PAD intervention on decisional capacity. N = 469 adults with psychotic disorders were interviewed at baseline and then randomly assigned to either a control group in which they received written materials about PADs or to an intervention group in which they were offered an opportunity to meet individually with a trained facilitator to create a PAD. At baseline, domains on the Decisional Competence Assessment Tool for PADs (DCAT-PAD) were most strongly associated with IQ, verbal memory, abstract thinking, and psychiatric symptoms. At one-month follow-up, participants in the intervention group showed more improvement on the DCAT-PAD than controls, particularly among participants with pre-morbid IQ estimates below the median of 100. The results suggest that PAD facilitation is an effective method to boost competence of cognitively-impaired clients to write PADs and make treatment decisions within PADs, thereby maximizing the chances their advance directives will be valid. PMID:17294136

[An attempt to explain fertility differentials in Upper Volta and in Ghana].

PubMed

Coulibaly, S P; Pool, I

1975-01-01

This study examines fertility differentials in Western Africa, notably in Upper Volta and in Ghana. The relationship between social and cultural transformation and fertility rate is usually seen as a matter of cause and effect. Direct variables caused by social transformation would be education, migration, and urbanization. This is not necessarily so, at least according to the Davis-Blake paradigm, which says that there are intermediate variables which intervene between fertility rate and the social system. For West Africa such variables are of 3 distinct types: 1) those which upset the normal flow of the family, such as separation due to migration, divorce, and marriage age; 2) those which influence conception itself, such as birth control, lactation and sexual abstinence; and, 3) cultural factors, such as poligamy and monogamy, type of conjugal union, and postpartum sexual abstinence. The central point of this study is that direct variables, i.e. migration, education and urbanization, do not directly influence fertility, but they influence the so-called intermediate variables, which, in turn, cause a change in fertility patterns. It must be remembered that birth control is still practically unknown in Western Africa.

Reconstruction of the unknown optimization cost functions from experimental recordings during static multi-finger prehension

PubMed Central

Niu, Xun; Terekhov, Alexander V.; Latash, Mark L.; Zatsiorsky, Vladimir M.

2013-01-01

The goal of the research is to reconstruct the unknown cost (objective) function(s) presumably used by the neural controller for sharing the total force among individual fingers in multi-finger prehension. The cost function was determined from experimental data by applying the recently developed Analytical Inverse Optimization (ANIO) method (Terekhov et al 2010). The core of the ANIO method is the Theorem of Uniqueness that specifies conditions for unique (with some restrictions) estimation of the objective functions. In the experiment, subjects (n=8) grasped an instrumented handle and maintained it at rest in the air with various external torques, loads, and target grasping forces applied to the object. The experimental data recorded from 80 trials showed a tendency to lie on a 2-dimensional hyperplane in the 4-dimensional finger-force space. Because the constraints in each trial were different, such a propensity is a manifestation of a neural mechanism (not the task mechanics). In agreement with the Lagrange principle for the inverse optimization, the plane of experimental observations was close to the plane resulting from the direct optimization. The latter plane was determined using the ANIO method. The unknown cost function was reconstructed successfully for each performer, as well as for the group data. The cost functions were found to be quadratic with non-zero linear terms. The cost functions obtained with the ANIO method yielded more accurate results than other optimization methods. The ANIO method has an evident potential for addressing the problem of optimization in motor control. PMID:22104742

MdMYB1 Regulates Anthocyanin and Malate Accumulation by Directly Facilitating Their Transport into Vacuoles in Apples1[OPEN

PubMed Central

Hu, Da-Gang; Sun, Cui-Hui; Ma, Qi-Jun; You, Chun-Xiang; Hao, Yu-Jin

2016-01-01

Tonoplast transporters, including proton pumps and secondary transporters, are essential for plant cell function and for quality formation of fleshy fruits and ornamentals. Vacuolar transport of anthocyanins, malate, and other metabolites is directly or indirectly dependent on the H+-pumping activities of vacuolar H+-ATPase (VHA) and/or vacuolar H+-pyrophosphatase, but how these proton pumps are regulated in modulating vacuolar transport is largely unknown. Here, we report a transcription factor, MdMYB1, in apples that binds to the promoters of two genes encoding the B subunits of VHA, MdVHA-B1 and MdVHA-B2, to transcriptionally activate its expression, thereby enhancing VHA activity. A series of transgenic analyses in apples demonstrates that MdMYB1/10 controls cell pH and anthocyanin accumulation partially by regulating MdVHA-B1 and MdVHA-B2. Furthermore, several other direct target genes of MdMYB10 are identified, including MdVHA-E2, MdVHP1, MdMATE-LIKE1, and MdtDT, which are involved in H+-pumping or in the transport of anthocyanins and malates into vacuoles. Finally, we show that the mechanism by which MYB controls malate and anthocyanin accumulation in apples also operates in Arabidopsis (Arabidopsis thaliana). These findings provide novel insights into how MYB transcription factors directly modulate the vacuolar transport system in addition to anthocyanin biosynthesis, consequently controlling organ coloration and cell pH in plants. PMID:26637549

Directional biases reveal utilization of arm's biomechanical properties for optimization of motor behavior.

PubMed

Goble, Jacob A; Zhang, Yanxin; Shimansky, Yury; Sharma, Siddharth; Dounskaia, Natalia V

2007-09-01

Strategies used by the CNS to optimize arm movements in terms of speed, accuracy, and resistance to fatigue remain largely unknown. A hypothesis is studied that the CNS exploits biomechanical properties of multijoint limbs to increase efficiency of movement control. To test this notion, a novel free-stroke drawing task was used that instructs subjects to make straight strokes in as many different directions as possible in the horizontal plane through rotations of the elbow and shoulder joints. Despite explicit instructions to distribute strokes uniformly, subjects showed biases to move in specific directions. These biases were associated with a tendency to perform movements that included active motion at one joint and largely passive motion at the other joint, revealing a tendency to minimize intervention of muscle torque for regulation of the effect of interaction torque. Other biomechanical factors, such as inertial resistance and kinematic manipulability, were unable to adequately account for these significant biases. Also, minimizations of jerk, muscle torque change, and sum of squared muscle torque were analyzed; however, these cost functions failed to explain the observed directional biases. Collectively, these results suggest that knowledge of biomechanical cost functions regarding interaction torque (IT) regulation is available to the control system. This knowledge may be used to evaluate potential movements and to select movement of "low cost." The preference to reduce active regulation of interaction torque suggests that, in addition to muscle energy, the criterion for movement cost may include neural activity required for movement control.

MdMYB1 Regulates Anthocyanin and Malate Accumulation by Directly Facilitating Their Transport into Vacuoles in Apples.

PubMed

Hu, Da-Gang; Sun, Cui-Hui; Ma, Qi-Jun; You, Chun-Xiang; Cheng, Lailiang; Hao, Yu-Jin

2016-03-01

Tonoplast transporters, including proton pumps and secondary transporters, are essential for plant cell function and for quality formation of fleshy fruits and ornamentals. Vacuolar transport of anthocyanins, malate, and other metabolites is directly or indirectly dependent on the H(+)-pumping activities of vacuolar H(+)-ATPase (VHA) and/or vacuolar H(+)-pyrophosphatase, but how these proton pumps are regulated in modulating vacuolar transport is largely unknown. Here, we report a transcription factor, MdMYB1, in apples that binds to the promoters of two genes encoding the B subunits of VHA, MdVHA-B1 and MdVHA-B2, to transcriptionally activate its expression, thereby enhancing VHA activity. A series of transgenic analyses in apples demonstrates that MdMYB1/10 controls cell pH and anthocyanin accumulation partially by regulating MdVHA-B1 and MdVHA-B2. Furthermore, several other direct target genes of MdMYB10 are identified, including MdVHA-E2, MdVHP1, MdMATE-LIKE1, and MdtDT, which are involved in H(+)-pumping or in the transport of anthocyanins and malates into vacuoles. Finally, we show that the mechanism by which MYB controls malate and anthocyanin accumulation in apples also operates in Arabidopsis (Arabidopsis thaliana). These findings provide novel insights into how MYB transcription factors directly modulate the vacuolar transport system in addition to anthocyanin biosynthesis, consequently controlling organ coloration and cell pH in plants. © 2016 American Society of Plant Biologists. All Rights Reserved.

Robust adaptive sliding mode control for uncertain systems with unknown time-varying delay input.

PubMed

Benamor, Anouar; Messaoud, Hassani

2018-05-02

This article focuses on robust adaptive sliding mode control law for uncertain discrete systems with unknown time-varying delay input, where the uncertainty is assumed unknown. The main results of this paper are divided into three phases. In the first phase, we propose a new sliding surface is derived within the Linear Matrix Inequalities (LMIs). In the second phase, using the new sliding surface, the novel Robust Sliding Mode Control (RSMC) is proposed where the upper bound of uncertainty is supposed known. Finally, the novel approach of Robust Adaptive Sliding ModeControl (RASMC) has been defined for this type of systems, where the upper limit of uncertainty which is assumed unknown. In this new approach, we have estimate the upper limit of uncertainties and we have determined the control law based on a sliding surface that will converge to zero. This novel control laws are been validated in simulation on an uncertain numerical system with good results and comparative study. This efficiency is emphasized through the application of the new controls on the two physical systems which are the process trainer PT326 and hydraulic system two tanks. Published by Elsevier Ltd.

Screening Carbohydrate Libraries for Protein Interactions Using the Direct ESI-MS Assay. Applications to Libraries of Unknown Concentration

NASA Astrophysics Data System (ADS)

Kitova, Elena N.; El-Hawiet, Amr; Klassen, John S.

2014-08-01

A semiquantitative electrospray ionization mass spectrometry (ESI-MS) binding assay suitable for analyzing mixtures of oligosaccharides, at unknown concentrations, for interactions with target proteins is described. The assay relies on the differences in the ratio of the relative abundances of the ligand-bound and free protein ions measured by ESI-MS at two or more initial protein concentrations to distinguish low affinity (≤103 M-1) ligands from moderate and high affinity (>105 M-1) ligands present in the library and to rank their affinities. Control experiments were performed on solutions of a single chain antibody and a mixture of synthetic oligosaccharides, with known affinities, in the absence and presence of a 40-component carbohydrate library to demonstrate the implementation and reliability of the assay. The application of the assay for screening natural libraries of carbohydrates against proteins is also demonstrated using mixtures of human milk oligosaccharides, isolated from breast milk, and fragments of a bacterial toxin and human galectin 3.

Consumption of pasteurized human lysozyme transgenic goats’ milk alters serum metabolite profile in young pigs

PubMed Central

Brundige, Dottie R.; Maga, Elizabeth A.; Klasing, Kirk C.

2009-01-01

Nutrition, bacterial composition of the gastrointestinal tract, and general health status can all influence the metabolic profile of an organism. We previously demonstrated that feeding pasteurized transgenic goats’ milk expressing human lysozyme (hLZ) can positively impact intestinal morphology and modulate intestinal microbiota composition in young pigs. The objective of this study was to further examine the effect of consuming hLZ-containing milk on young pigs by profiling serum metabolites. Pigs were placed into two groups and fed a diet of solid food and either control (non-transgenic) goats’ milk or milk from hLZ-transgenic goats for 6 weeks. Serum samples were collected at the end of the feeding period and global metabolite profiling was performed. For a total of 225 metabolites (160 known, 65 unknown) semi-quantitative data was obtained. Levels of 18 known and 4 unknown metabolites differed significantly between the two groups with the direction of change in 13 of the 18 known metabolites being almost entirely congruent with improved health status, particularly in terms of the gastrointestinal tract health and immune response, with the effects of the other five being neutral or unknown. These results further support our hypothesis that consumption of hLZ-containing milk is beneficial to health. PMID:19847666

Neural net target-tracking system using structured laser patterns

NASA Astrophysics Data System (ADS)

Cho, Jae-Wan; Lee, Yong-Bum; Lee, Nam-Ho; Park, Soon-Yong; Lee, Jongmin; Choi, Gapchu; Baek, Sunghyun; Park, Dong-Sun

1996-06-01

In this paper, we describe a robot endeffector tracking system using sensory information from recently-announced structured pattern laser diodes, which can generate images with several different types of structured pattern. The neural network approach is employed to recognize the robot endeffector covering the situation of three types of motion: translation, scaling and rotation. Features for the neural network to detect the position of the endeffector are extracted from the preprocessed images. Artificial neural networks are used to store models and to match with unknown input features recognizing the position of the robot endeffector. Since a minimal number of samples are used for different directions of the robot endeffector in the system, an artificial neural network with the generalization capability can be utilized for unknown input features. A feedforward neural network with the generalization capability can be utilized for unknown input features. A feedforward neural network trained with the back propagation learning is used to detect the position of the robot endeffector. Another feedforward neural network module is used to estimate the motion from a sequence of images and to control movements of the robot endeffector. COmbining the tow neural networks for recognizing the robot endeffector and estimating the motion with the preprocessing stage, the whole system keeps tracking of the robot endeffector effectively.

Consumption of pasteurized human lysozyme transgenic goats' milk alters serum metabolite profile in young pigs.

PubMed

Brundige, Dottie R; Maga, Elizabeth A; Klasing, Kirk C; Murray, James D

2010-08-01

Nutrition, bacterial composition of the gastrointestinal tract, and general health status can all influence the metabolic profile of an organism. We previously demonstrated that feeding pasteurized transgenic goats' milk expressing human lysozyme (hLZ) can positively impact intestinal morphology and modulate intestinal microbiota composition in young pigs. The objective of this study was to further examine the effect of consuming hLZ-containing milk on young pigs by profiling serum metabolites. Pigs were placed into two groups and fed a diet of solid food and either control (non-transgenic) goats' milk or milk from hLZ-transgenic goats for 6 weeks. Serum samples were collected at the end of the feeding period and global metabolite profiling was performed. For a total of 225 metabolites (160 known, 65 unknown) semi-quantitative data was obtained. Levels of 18 known and 4 unknown metabolites differed significantly between the two groups with the direction of change in 13 of the 18 known metabolites being almost entirely congruent with improved health status, particularly in terms of the gastrointestinal tract health and immune response, with the effects of the other five being neutral or unknown. These results further support our hypothesis that consumption of hLZ-containing milk is beneficial to health.

Neuro-adaptive backstepping control of SISO non-affine systems with unknown gain sign.

PubMed

Ramezani, Zahra; Arefi, Mohammad Mehdi; Zargarzadeh, Hassan; Jahed-Motlagh, Mohammad Reza

2016-11-01

This paper presents two neuro-adaptive controllers for a class of uncertain single-input, single-output (SISO) nonlinear non-affine systems with unknown gain sign. The first approach is state feedback controller, so that a neuro-adaptive state-feedback controller is constructed based on the backstepping technique. The second approach is an observer-based controller and K-filters are designed to estimate the system states. The proposed method relaxes a priori knowledge of control gain sign and therefore by utilizing the Nussbaum-type functions this problem is addressed. In these methods, neural networks are employed to approximate the unknown nonlinear functions. The proposed adaptive control schemes guarantee that all the closed-loop signals are semi-globally uniformly ultimately bounded (SGUUB). Finally, the theoretical results are numerically verified through simulation examples. Simulation results show the effectiveness of the proposed methods. Copyright © 2016 ISA. All rights reserved.

Arm coordination in octopus crawling involves unique motor control strategies.

PubMed

Levy, Guy; Flash, Tamar; Hochner, Binyamin

2015-05-04

To cope with the exceptional computational complexity that is involved in the control of its hyper-redundant arms [1], the octopus has adopted unique motor control strategies in which the central brain activates rather autonomous motor programs in the elaborated peripheral nervous system of the arms [2, 3]. How octopuses coordinate their eight long and flexible arms in locomotion is still unknown. Here, we present the first detailed kinematic analysis of octopus arm coordination in crawling. The results are surprising in several respects: (1) despite its bilaterally symmetrical body, the octopus can crawl in any direction relative to its body orientation; (2) body and crawling orientation are monotonically and independently controlled; and (3) contrasting known animal locomotion, octopus crawling lacks any apparent rhythmical patterns in limb coordination, suggesting a unique non-rhythmical output of the octopus central controller. We show that this uncommon maneuverability is derived from the radial symmetry of the arms around the body and the simple pushing-by-elongation mechanism by which the arms create the crawling thrust. These two together enable a mechanism whereby the central controller chooses in a moment-to-moment fashion which arms to recruit for pushing the body in an instantaneous direction. Our findings suggest that the soft molluscan body has affected in an embodied way [4, 5] the emergence of the adaptive motor behavior of the octopus. Copyright © 2015 Elsevier Ltd. All rights reserved.

An Indirect Adaptive Control Scheme in the Presence of Actuator and Sensor Failures

NASA Technical Reports Server (NTRS)

Sun, Joy Z.; Josh, Suresh M.

2009-01-01

The problem of controlling a system in the presence of unknown actuator and sensor faults is addressed. The system is assumed to have groups of actuators, and groups of sensors, with each group consisting of multiple redundant similar actuators or sensors. The types of actuator faults considered consist of unknown actuators stuck in unknown positions, as well as reduced actuator effectiveness. The sensor faults considered include unknown biases and outages. The approach employed for fault detection and estimation consists of a bank of Kalman filters based on multiple models, and subsequent control reconfiguration to mitigate the effect of biases caused by failed components as well as to obtain stability and satisfactory performance using the remaining actuators and sensors. Conditions for fault identifiability are presented, and the adaptive scheme is applied to an aircraft flight control example in the presence of actuator failures. Simulation results demonstrate that the method can rapidly and accurately detect faults and estimate the fault values, thus enabling safe operation and acceptable performance in spite of failures.

Application of incremental unknowns to the Burgers equation

NASA Technical Reports Server (NTRS)

Choi, Haecheon; Temam, Roger

1993-01-01

In this article, we make a few remarks on the role that attractors and inertial manifolds play in fluid mechanics problems. We then describe the role of incremental unknowns for approximating attractors and inertial manifolds when finite difference multigrid discretizations are used. The relation with direct numerical simulation and large eddy simulation is also mentioned.

From Intensity Profile to Surface Normal: Photometric Stereo for Unknown Light Sources and Isotropic Reflectances.

PubMed

Lu, Feng; Matsushita, Yasuyuki; Sato, Imari; Okabe, Takahiro; Sato, Yoichi

2015-10-01

We propose an uncalibrated photometric stereo method that works with general and unknown isotropic reflectances. Our method uses a pixel intensity profile, which is a sequence of radiance intensities recorded at a pixel under unknown varying directional illumination. We show that for general isotropic materials and uniformly distributed light directions, the geodesic distance between intensity profiles is linearly related to the angular difference of their corresponding surface normals, and that the intensity distribution of the intensity profile reveals reflectance properties. Based on these observations, we develop two methods for surface normal estimation; one for a general setting that uses only the recorded intensity profiles, the other for the case where a BRDF database is available while the exact BRDF of the target scene is still unknown. Quantitative and qualitative evaluations are conducted using both synthetic and real-world scenes, which show the state-of-the-art accuracy of smaller than 10 degree without using reference data and 5 degree with reference data for all 100 materials in MERL database.

Containment control of networked autonomous underwater vehicles: A predictor-based neural DSC design.

PubMed

Peng, Zhouhua; Wang, Dan; Wang, Wei; Liu, Lu

2015-11-01

This paper investigates the containment control problem of networked autonomous underwater vehicles in the presence of model uncertainty and unknown ocean disturbances. A predictor-based neural dynamic surface control design method is presented to develop the distributed adaptive containment controllers, under which the trajectories of follower vehicles nearly converge to the dynamic convex hull spanned by multiple reference trajectories over a directed network. Prediction errors, rather than tracking errors, are used to update the neural adaptation laws, which are independent of the tracking error dynamics, resulting in two time-scales to govern the entire system. The stability property of the closed-loop network is established via Lyapunov analysis, and transient property is quantified in terms of L2 norms of the derivatives of neural weights, which are shown to be smaller than the classical neural dynamic surface control approach. Comparative studies are given to show the substantial improvements of the proposed new method. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Bounded extremum seeking for angular velocity actuated control of nonholonomic unicycle

DOE PAGES

Scheinker, Alexander

2016-08-17

Here, we study control of the angular-velocity actuated nonholonomic unicycle, via a simple, bounded extremum seeking controller which is robust to external disturbances and measurement noise. The vehicle performs source seeking despite not having any position information about itself or the source, able only to sense a noise corrupted scalar value whose extremum coincides with the unknown source location. In order to control the angular velocity, rather than the angular heading directly, a controller is developed such that the closed loop system exhibits multiple time scales and requires an analysis approach expanding the previous work of Kurzweil, Jarnik, Sussmann, andmore » Liu, utilizing weak limits. We provide analytic proof of stability and demonstrate how this simple scheme can be extended to include position-independent source seeking, tracking, and collision avoidance of groups on autonomous vehicles in GPS-denied environments, based only on a measure of distance to an obstacle, which is an especially important feature for an autonomous agent.« less

Compensating Unknown Time-Varying Delay in Opto-Electronic Platform Tracking Servo System.

PubMed

Xie, Ruihong; Zhang, Tao; Li, Jiaquan; Dai, Ming

2017-05-09

This paper investigates the problem of compensating miss-distance delay in opto-electronic platform tracking servo system. According to the characteristic of LOS (light-of-sight) motion, we setup the Markovian process model and compensate this unknown time-varying delay by feed-forward forecasting controller based on robust H∞ control. Finally, simulation based on double closed-loop PI (Proportion Integration) control system indicates that the proposed method is effective for compensating unknown time-varying delay. Tracking experiments on the opto-electronic platform indicate that RMS (root-mean-square) error is 1.253 mrad when tracking 10° 0.2 Hz signal.

Directional control of WAVE2 membrane targeting by EB1 and phosphatidylinositol 3,4,5-triphosphate.

PubMed

Takahashi, Kazuhide; Tanaka, Tacu; Suzuki, Katsuo

2010-03-01

Membrane targeting of WAVE2 along microtubules is mediated by a motor protein kinesin and requires Pak1, a downstream effector of Rac1. However, the mechanism by which WAVE2 targeting to the leading edge is directionally controlled remains largely unknown. Here we demonstrate that EB1, a microtubule plus-end-binding protein, constitutively associates with stathmin, a microtubule-destabilizing protein, in human breast cancer cells. Stimulation of the cells with insulin-like growth factor I (IGF-I) induced Pak1-dependent binding of the EB1-stathmin complex to microtubules that bear WAVE2 and colocalization of the complex with WAVE2 at the leading edge. Depletion of EB1 by small interfering RNA (siRNA) abrogated the IGF-I-induced WAVE2 targeting and stathmin binding to microtubules. On the other hand, chemotaxis chamber assays indicated that the IGF-I receptor (IGF-IR) was locally activated in the region facing toward IGF-I. In addition, IGF-I caused phosphatidylinositol 3-kinase (PI 3-kinase)-dependent production of phosphatidylinositol 3,4,5-triphosphate (PIP3) near activated IGF-IR and WAVE2 colocalization with it. Collectively, WAVE2-membrane targeting is directionally controlled by binding of the EB1-stathmin complex to WAVE2-bearing microtubules and by the interaction between WAVE2 and PIP3 produced near IGF-IR that is locally activated by IGF-I.

Adaptive Control of Linear Modal Systems Using Residual Mode Filters and a Simple Disturbance Estimator

NASA Technical Reports Server (NTRS)

Balas, Mark; Frost, Susan

2012-01-01

Flexible structures containing a large number of modes can benefit from adaptive control techniques which are well suited to applications that have unknown modeling parameters and poorly known operating conditions. In this paper, we focus on a direct adaptive control approach that has been extended to handle adaptive rejection of persistent disturbances. We extend our adaptive control theory to accommodate troublesome modal subsystems of a plant that might inhibit the adaptive controller. In some cases the plant does not satisfy the requirements of Almost Strict Positive Realness. Instead, there maybe be a modal subsystem that inhibits this property. This section will present new results for our adaptive control theory. We will modify the adaptive controller with a Residual Mode Filter (RMF) to compensate for the troublesome modal subsystem, or the Q modes. Here we present the theory for adaptive controllers modified by RMFs, with attention to the issue of disturbances propagating through the Q modes. We apply the theoretical results to a flexible structure example to illustrate the behavior with and without the residual mode filter.

Comparing Electronic News Media Reports of Potential Bioterrorism-Related Incidents Involving Unknown White Powder to Reports Received by the United States Centers for Disease Control and Prevention and the Federal Bureau of Investigation: USA, 2009–2011

PubMed Central

Fajardo, Geroncio C.; Posid, Joseph; Papagiotas, Stephen; Lowe, Luis

2015-01-01

There have been periodic electronic news media reports of potential bioterrorism-related incidents involving unknown substances (often referred to as “white powder”) since the 2001 intentional dissemination of Bacillus anthracis through the US Postal System. This study reviewed the number of unknown “white powder” incidents reported online by the electronic news media and compared them with unknown “white powder” incidents reported to the US Centers for Disease Control and Prevention (CDC) and the US Federal Bureau of Investigation (FBI) during a two-year period from June 1, 2009 and May 31, 2011. Results identified 297 electronic news media reports, 538 CDC reports, and 384 FBI reports of unknown “white powder.” This study showed different unknown “white powder” incidents captured by each of the three sources. However, the authors could not determine the public health implications of this discordance. PMID:25420771

Osteocyte-Intrinsic TGF-β Signaling Regulates Bone Quality through Perilacunar/Canalicular Remodeling

DOE PAGES

Dole, Neha S.; Mazur, Courtney M.; Acevedo, Claire; ...

2017-11-28

Poor bone quality contributes to bone fragility in diabetes, aging, and osteogenesis imperfecta. However, the mechanisms controlling bone quality are not well understood, contributing to the current lack of strategies to diagnose or treat bone quality deficits. Transforming growth factor beta (TGF-β) signaling is a crucial mechanism known to regulate the material quality of bone, but its cellular target in this regulation is unknown. Studies showing that osteocytes directly remodel their perilacunar/canalicular matrix led us to hypothesize that TGF-β controls bone quality through perilacunar/canalicular remodeling (PLR). Using inhibitors and mice with an osteocyte-intrinsic defect in TGF-β signaling (TβRII ocy-/-), wemore » show that TGF-β regulates PLR in a cell-intrinsic manner to control bone quality. Altogether, this study emphasizes that osteocytes are key in executing the biological control of bone quality through PLR, thereby highlighting the fundamental role of osteocyte-mediated PLR in bone homeostasis and fragility. Resistance to fracture requires healthy bone mass and quality. However, the cellular mechanisms regulating bone quality are unclear. Dole et al. show that osteocyte-intrinsic TGF-β signaling maintains bone quality through perilacunar/canalicular remodeling. Thus, osteocytes mediate perilacunar/canalicular remodeling and osteoclast-directed remodeling to cooperatively maintain bone quality and mass and prevent fragility.« less

The Control of Auxin Transport in Parasitic and Symbiotic Root–Microbe Interactions

PubMed Central

Ng, Jason Liang Pin; Perrine-Walker, Francine; Wasson, Anton P.; Mathesius, Ulrike

2015-01-01

Most field-grown plants are surrounded by microbes, especially from the soil. Some of these, including bacteria, fungi and nematodes, specifically manipulate the growth and development of their plant hosts, primarily for the formation of structures housing the microbes in roots. These developmental processes require the correct localization of the phytohormone auxin, which is involved in the control of cell division, cell enlargement, organ development and defense, and is thus a likely target for microbes that infect and invade plants. Some microbes have the ability to directly synthesize auxin. Others produce specific signals that indirectly alter the accumulation of auxin in the plant by altering auxin transport. This review highlights root–microbe interactions in which auxin transport is known to be targeted by symbionts and parasites to manipulate the development of their host root system. We include case studies for parasitic root–nematode interactions, mycorrhizal symbioses as well as nitrogen fixing symbioses in actinorhizal and legume hosts. The mechanisms to achieve auxin transport control that have been studied in model organisms include the induction of plant flavonoids that indirectly alter auxin transport and the direct targeting of auxin transporters by nematode effectors. In most cases, detailed mechanisms of auxin transport control remain unknown. PMID:27135343

Osteocyte-Intrinsic TGF-β Signaling Regulates Bone Quality through Perilacunar/Canalicular Remodeling

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

Dole, Neha S.; Mazur, Courtney M.; Acevedo, Claire

Poor bone quality contributes to bone fragility in diabetes, aging, and osteogenesis imperfecta. However, the mechanisms controlling bone quality are not well understood, contributing to the current lack of strategies to diagnose or treat bone quality deficits. Transforming growth factor beta (TGF-β) signaling is a crucial mechanism known to regulate the material quality of bone, but its cellular target in this regulation is unknown. Studies showing that osteocytes directly remodel their perilacunar/canalicular matrix led us to hypothesize that TGF-β controls bone quality through perilacunar/canalicular remodeling (PLR). Using inhibitors and mice with an osteocyte-intrinsic defect in TGF-β signaling (TβRII ocy-/-), wemore » show that TGF-β regulates PLR in a cell-intrinsic manner to control bone quality. Altogether, this study emphasizes that osteocytes are key in executing the biological control of bone quality through PLR, thereby highlighting the fundamental role of osteocyte-mediated PLR in bone homeostasis and fragility. Resistance to fracture requires healthy bone mass and quality. However, the cellular mechanisms regulating bone quality are unclear. Dole et al. show that osteocyte-intrinsic TGF-β signaling maintains bone quality through perilacunar/canalicular remodeling. Thus, osteocytes mediate perilacunar/canalicular remodeling and osteoclast-directed remodeling to cooperatively maintain bone quality and mass and prevent fragility.« less

Quadrotor Control in the Presence of Unknown Mass Properties

NASA Astrophysics Data System (ADS)

Duivenvoorden, Rikky Ricardo Petrus Rufino

Quadrotor UAVs are popular due to their mechanical simplicity, as well as their capability to hover and vertically take-off and land. As applications diversify, quadrotors are increasingly required to operate under unknown mass properties, for example as a multirole sensor platform or for package delivery operations. The work presented here consists of the derivation of a generalized quadrotor dynamic model without the typical simplifying assumptions on the first and second moments of mass. The maximum payload capacity of a quadrotor in hover, and the observability of the unknown mass properties are discussed. A brief introduction of L1 adaptive control is provided, and three different L 1 adaptive controllers were designed for the Parrot AR.Drone quadrotor. Their tracking and disturbance rejection performance was compared to the baseline nonlinear controller in experiments. Finally, the results of the combination of L1 adaptive control with iterative learning control are presented, showing high performance trajectory tracking under uncertainty.

Helicopter pilot estimation of self-altitude in a degraded visual environment

NASA Astrophysics Data System (ADS)

Crowley, John S.; Haworth, Loran A.; Szoboszlay, Zoltan P.; Lee, Alan G.

2000-06-01

The effect of night vision devices and degraded visual imagery on self-attitude perception is unknown. Thirteen Army aviators with normal vision flew five flights under various visual conditions in a modified AH-1 (Cobra) helicopter. Subjects estimated their altitude or flew to specified altitudes while flying a series of maneuvers. The results showed that subjects were better at detecting and controlling changes in altitude than they were at flying to or naming a specific altitude. In cruise flight and descent, the subjects tended to fly above the desired altitude, an error in the safe direction. While hovering, the direction of error was less predictable. In the low-level cruise flight scenario tested in this study, altitude perception was affected more by changes in image resolution than by changes in FOV or ocularity.

Emergence of an optimal search strategy from a simple random walk

PubMed Central

Sakiyama, Tomoko; Gunji, Yukio-Pegio

2013-01-01

In reports addressing animal foraging strategies, it has been stated that Lévy-like algorithms represent an optimal search strategy in an unknown environment, because of their super-diffusion properties and power-law-distributed step lengths. Here, starting with a simple random walk algorithm, which offers the agent a randomly determined direction at each time step with a fixed move length, we investigated how flexible exploration is achieved if an agent alters its randomly determined next step forward and the rule that controls its random movement based on its own directional moving experiences. We showed that our algorithm led to an effective food-searching performance compared with a simple random walk algorithm and exhibited super-diffusion properties, despite the uniform step lengths. Moreover, our algorithm exhibited a power-law distribution independent of uniform step lengths. PMID:23804445

Emergence of an optimal search strategy from a simple random walk.

PubMed

Sakiyama, Tomoko; Gunji, Yukio-Pegio

2013-09-06

In reports addressing animal foraging strategies, it has been stated that Lévy-like algorithms represent an optimal search strategy in an unknown environment, because of their super-diffusion properties and power-law-distributed step lengths. Here, starting with a simple random walk algorithm, which offers the agent a randomly determined direction at each time step with a fixed move length, we investigated how flexible exploration is achieved if an agent alters its randomly determined next step forward and the rule that controls its random movement based on its own directional moving experiences. We showed that our algorithm led to an effective food-searching performance compared with a simple random walk algorithm and exhibited super-diffusion properties, despite the uniform step lengths. Moreover, our algorithm exhibited a power-law distribution independent of uniform step lengths.

Formation of visual memories controlled by gamma power phase-locked to alpha oscillations.

PubMed

Park, Hyojin; Lee, Dong Soo; Kang, Eunjoo; Kang, Hyejin; Hahm, Jarang; Kim, June Sic; Chung, Chun Kee; Jiang, Haiteng; Gross, Joachim; Jensen, Ole

2016-06-16

Neuronal oscillations provide a window for understanding the brain dynamics that organize the flow of information from sensory to memory areas. While it has been suggested that gamma power reflects feedforward processing and alpha oscillations feedback control, it remains unknown how these oscillations dynamically interact. Magnetoencephalography (MEG) data was acquired from healthy subjects who were cued to either remember or not remember presented pictures. Our analysis revealed that in anticipation of a picture to be remembered, alpha power decreased while the cross-frequency coupling between gamma power and alpha phase increased. A measure of directionality between alpha phase and gamma power predicted individual ability to encode memory: stronger control of alpha phase over gamma power was associated with better memory. These findings demonstrate that encoding of visual information is reflected by a state determined by the interaction between alpha and gamma activity.

Panax Notoginseng Saponin Controls IL-17 Expression in Helper T Cells

PubMed Central

Wei, Jia-Ru; Wen, Xiaofeng; Bible, Paul W.; Li, Zhiyu; Nussenblatt, Robert B.

2017-01-01

Abstract Purpose: Panax Notoginseng, a traditional Chinese medicine, is known as an anti-inflammatory herb. However, the molecular mechanism by which it controls helper T cell mediated immune responses is largely unknown. Methods: Naive CD4+ T cells isolated from healthy donors, patients with Behcet's disease, and C57BL/6 mice were polarized into Th1, Th17, and Treg cells. Proliferation and cytokine expression were measured in these cells with the presence or absence of Panax Notoginseng saponins (PNS). Genomewide expression profiles of Th1, Th17, and Treg cells were assessed using Affymetrix microarray analysis. Results: We found that PNS control the proliferation and differentiation of Th17 cells by globally downregulating the expression of inflammatory cytokines and cell cycle genes. Conclusions: These findings demonstrated that PNS function as an anti-inflammatory agent through directly targeting Th17 cell mediated immune response. PMID:28051353

Formation of visual memories controlled by gamma power phase-locked to alpha oscillations

PubMed Central

Park, Hyojin; Lee, Dong Soo; Kang, Eunjoo; Kang, Hyejin; Hahm, Jarang; Kim, June Sic; Chung, Chun Kee; Jiang, Haiteng; Gross, Joachim; Jensen, Ole

2016-01-01

Neuronal oscillations provide a window for understanding the brain dynamics that organize the flow of information from sensory to memory areas. While it has been suggested that gamma power reflects feedforward processing and alpha oscillations feedback control, it remains unknown how these oscillations dynamically interact. Magnetoencephalography (MEG) data was acquired from healthy subjects who were cued to either remember or not remember presented pictures. Our analysis revealed that in anticipation of a picture to be remembered, alpha power decreased while the cross-frequency coupling between gamma power and alpha phase increased. A measure of directionality between alpha phase and gamma power predicted individual ability to encode memory: stronger control of alpha phase over gamma power was associated with better memory. These findings demonstrate that encoding of visual information is reflected by a state determined by the interaction between alpha and gamma activity. PMID:27306959

Composite Intelligent Learning Control of Strict-Feedback Systems With Disturbance.

PubMed

Xu, Bin; Sun, Fuchun

2018-02-01

This paper addresses the dynamic surface control of uncertain nonlinear systems on the basis of composite intelligent learning and disturbance observer in presence of unknown system nonlinearity and time-varying disturbance. The serial-parallel estimation model with intelligent approximation and disturbance estimation is built to obtain the prediction error and in this way the composite law for weights updating is constructed. The nonlinear disturbance observer is developed using intelligent approximation information while the disturbance estimation is guaranteed to converge to a bounded compact set. The highlight is that different from previous work directly toward asymptotic stability, the transparency of the intelligent approximation and disturbance estimation is included in the control scheme. The uniformly ultimate boundedness stability is analyzed via Lyapunov method. Through simulation verification, the composite intelligent learning with disturbance observer can efficiently estimate the effect caused by system nonlinearity and disturbance while the proposed approach obtains better performance with higher accuracy.

Formation of visual memories controlled by gamma power phase-locked to alpha oscillations

NASA Astrophysics Data System (ADS)

Park, Hyojin; Lee, Dong Soo; Kang, Eunjoo; Kang, Hyejin; Hahm, Jarang; Kim, June Sic; Chung, Chun Kee; Jiang, Haiteng; Gross, Joachim; Jensen, Ole

2016-06-01

Neuronal oscillations provide a window for understanding the brain dynamics that organize the flow of information from sensory to memory areas. While it has been suggested that gamma power reflects feedforward processing and alpha oscillations feedback control, it remains unknown how these oscillations dynamically interact. Magnetoencephalography (MEG) data was acquired from healthy subjects who were cued to either remember or not remember presented pictures. Our analysis revealed that in anticipation of a picture to be remembered, alpha power decreased while the cross-frequency coupling between gamma power and alpha phase increased. A measure of directionality between alpha phase and gamma power predicted individual ability to encode memory: stronger control of alpha phase over gamma power was associated with better memory. These findings demonstrate that encoding of visual information is reflected by a state determined by the interaction between alpha and gamma activity.

Robustness of composite pulse sequences to time-dependent noise

NASA Astrophysics Data System (ADS)

Kabytayev, Chingiz; Green, Todd J.; Khodjasteh, Kaveh; Viola, Lorenza; Biercuk, Michael J.; Brown, Kenneth R.

2014-03-01

Quantum control protocols can minimize the effect of noise sources that reduce the quality of quantum operations. Originally developed for NMR, composite pulse sequences correct for unknown static control errors . We study these compensating pulses in the general case of time-varying Gaussian control noise using a filter-function approach and detailed numerics. Three different noise models were considered in this work: amplitude noise, detuning noise and simultaneous presence of both noises. Pulse sequences are shown to be robust to noise up to frequencies as high as ~10% of the Rabi frequency. Robustness of pulses designed for amplitude noise is explained using a geometric picture that naturally follows from filter function. We also discuss future directions including new pulses correcting for noise of certain frequency. True J. Merrill and Kenneth R. Brown. arXiv:1203.6392v1. In press Adv. Chem. Phys. (2013)

Design and analysis of adaptive Super-Twisting sliding mode control for a microgyroscope.

PubMed

Feng, Zhilin; Fei, Juntao

2018-01-01

This paper proposes a novel adaptive Super-Twisting sliding mode control for a microgyroscope under unknown model uncertainties and external disturbances. In order to improve the convergence rate of reaching the sliding surface and the accuracy of regulating and trajectory tracking, a high order Super-Twisting sliding mode control strategy is employed, which not only can combine the advantages of the traditional sliding mode control with the Super-Twisting sliding mode control, but also guarantee that the designed control system can reach the sliding surface and equilibrium point in a shorter finite time from any initial state and avoid chattering problems. In consideration of unknown parameters of micro gyroscope system, an adaptive algorithm based on Lyapunov stability theory is designed to estimate the unknown parameters and angular velocity of microgyroscope. Finally, the effectiveness of the proposed scheme is demonstrated by simulation results. The comparative study between adaptive Super-Twisting sliding mode control and conventional sliding mode control demonstrate the superiority of the proposed method.

Genetic control of an epigenetic cell degeneration syndrome in Podospora anserina.

PubMed

Haedens, Vicki; Malagnac, Fabienne; Silar, Philippe

2005-06-01

Filamentous fungi frequently present degenerative processes, whose molecular basis is very often unknown. Here, we present three mutant screens that result in the identification of 29 genes that directly or indirectly control Crippled Growth (CG), an epigenetic cell degeneration of the filamentous ascomycete Podospora anserina. Two of these genes were previously shown to encode a MAP kinase kinase kinase and an NADPH oxidase involved in a signal transduction cascade that participates in stationary phase differentiations, fruiting body development and defence against fungal competitors. The numerous genes identified can be incorporated in a model in which CG results from the sustained activation of the MAP kinase cascade. Our data also emphasize the complex regulatory network underlying three interconnected processes in P. anserina: sexual reproduction, defence against competitors, and cell degeneration.

Provider and Patient Directed Financial Incentives to Improve Care and Outcomes for Patients with Diabetes

PubMed Central

Lorincz, Ilona S.; Lawson, Brittany C. T.

2012-01-01

Incentive programs directed at both providers and patients have become increasingly widespread. Pay-for-performance (P4P) where providers receive financial incentives to carry out specific care or improve clinical outcomes has been widely implemented. The existing literature indicates they probably spur initial gains which then level off or partially revert if incentives are withdrawn. The literature also indicates that process measures are easier to influence through P4P programs but that intermediate outcomes such as glucose, blood pressure, and cholesterol control are harder to influence, and the long term impact of P4P programs on health is largely unknown. Programs directed at patients show greater promise as a means to influence patient behavior and intermediate outcomes such as weight loss; however, the evidence for long term effects are lacking. In combination, both patient and provider incentives are potentially powerful tools but whether they are cost-effective has yet to be determined. PMID:23225214

Brain-wide mapping of neural activity controlling zebrafish exploratory locomotion

PubMed Central

Dunn, Timothy W; Mu, Yu; Narayan, Sujatha; Randlett, Owen; Naumann, Eva A; Yang, Chao-Tsung; Schier, Alexander F

2016-01-01

In the absence of salient sensory cues to guide behavior, animals must still execute sequences of motor actions in order to forage and explore. How such successive motor actions are coordinated to form global locomotion trajectories is unknown. We mapped the structure of larval zebrafish swim trajectories in homogeneous environments and found that trajectories were characterized by alternating sequences of repeated turns to the left and to the right. Using whole-brain light-sheet imaging, we identified activity relating to the behavior in specific neural populations that we termed the anterior rhombencephalic turning region (ARTR). ARTR perturbations biased swim direction and reduced the dependence of turn direction on turn history, indicating that the ARTR is part of a network generating the temporal correlations in turn direction. We also find suggestive evidence for ARTR mutual inhibition and ARTR projections to premotor neurons. Finally, simulations suggest the observed turn sequences may underlie efficient exploration of local environments. DOI: http://dx.doi.org/10.7554/eLife.12741.001 PMID:27003593

Engagement of neural circuits underlying 2D spatial navigation in a rodent virtual reality system.

PubMed

Aronov, Dmitriy; Tank, David W

2014-10-22

Virtual reality (VR) enables precise control of an animal's environment and otherwise impossible experimental manipulations. Neural activity in rodents has been studied on virtual 1D tracks. However, 2D navigation imposes additional requirements, such as the processing of head direction and environment boundaries, and it is unknown whether the neural circuits underlying 2D representations can be sufficiently engaged in VR. We implemented a VR setup for rats, including software and large-scale electrophysiology, that supports 2D navigation by allowing rotation and walking in any direction. The entorhinal-hippocampal circuit, including place, head direction, and grid cells, showed 2D activity patterns similar to those in the real world. Furthermore, border cells were observed, and hippocampal remapping was driven by environment shape, suggesting functional processing of virtual boundaries. These results illustrate that 2D spatial representations can be engaged by visual and rotational vestibular stimuli alone and suggest a novel VR tool for studying rat navigation.

Direct Midbrain Dopamine Input to the Suprachiasmatic Nucleus Accelerates Circadian Entrainment.

PubMed

Grippo, Ryan M; Purohit, Aarti M; Zhang, Qi; Zweifel, Larry S; Güler, Ali D

2017-08-21

Dopamine (DA) neurotransmission controls behaviors important for survival, including voluntary movement, reward processing, and detection of salient events, such as food or mate availability. Dopaminergic tone also influences circadian physiology and behavior. Although the evolutionary significance of this input is appreciated, its precise neurophysiological architecture remains unknown. Here, we identify a novel, direct connection between the DA neurons of the ventral tegmental area (VTA) and the suprachiasmatic nucleus (SCN). We demonstrate that D1 dopamine receptor (Drd1) signaling within the SCN is necessary for properly timed resynchronization of activity rhythms to phase-shifted light:dark cycles and that elevation of DA tone through selective activation of VTA DA neurons accelerates photoentrainment. Our findings demonstrate a previously unappreciated role for direct DA input to the master circadian clock and highlight the importance of an evolutionarily significant relationship between the circadian system and the neuromodulatory circuits that govern motivational behaviors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fission meter

DOEpatents

Rowland, Mark S [Alamo, CA; Snyderman, Neal J [Berkeley, CA

2012-04-10

A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source.

Nonlinear Control of the Doubly Fed Induction Motor with Copper Losses Minimization for Electrical Vehicle

NASA Astrophysics Data System (ADS)

Drid, S.; Nait-Said, M.-S.; Tadjine, M.; Makouf, A.

2008-06-01

There is an increasing interest in electric vehicles due to environmental concerns. Recent efforts are directed toward developing an improved propulsion system for electric vehicles applications with minimal power losses. This paper deals with the high efficient vector control for the reduction of copper losses of the doubly fed motor. Firstly, the feedback linearization control based on Lyapunov approach is employed to design the underlying controller achieving the double fluxes orientation. The fluxes controllers are designed independently of the speed. The speed controller is designed using the Lyapunov method especially employed to the unknown load torques. The global asymptotic stability of the overall system is theoretically proven. Secondly, a new Torque Copper Losses Factor is proposed to deal with the problem of the machine copper losses. Its main function is to optimize the torque in keeping the machine saturation at an acceptable level. This leads to a reduction in machine currents and therefore their accompanied copper losses guaranteeing improved machine efficiency. The simulation results in comparative presentation confirm largely the effectiveness of the proposed DFIM control with a very interesting energy saving contribution.

Adaptive Fuzzy Output Constrained Control Design for Multi-Input Multioutput Stochastic Nonstrict-Feedback Nonlinear Systems.

PubMed

Li, Yongming; Tong, Shaocheng

2017-12-01

In this paper, an adaptive fuzzy output constrained control design approach is addressed for multi-input multioutput uncertain stochastic nonlinear systems in nonstrict-feedback form. The nonlinear systems addressed in this paper possess unstructured uncertainties, unknown gain functions and unknown stochastic disturbances. Fuzzy logic systems are utilized to tackle the problem of unknown nonlinear uncertainties. The barrier Lyapunov function technique is employed to solve the output constrained problem. In the framework of backstepping design, an adaptive fuzzy control design scheme is constructed. All the signals in the closed-loop system are proved to be bounded in probability and the system outputs are constrained in a given compact set. Finally, the applicability of the proposed controller is well carried out by a simulation example.

Backstepping Design of Adaptive Neural Fault-Tolerant Control for MIMO Nonlinear Systems.

PubMed

Gao, Hui; Song, Yongduan; Wen, Changyun

In this paper, an adaptive controller is developed for a class of multi-input and multioutput nonlinear systems with neural networks (NNs) used as a modeling tool. It is shown that all the signals in the closed-loop system with the proposed adaptive neural controller are globally uniformly bounded for any external input in . In our control design, the upper bound of the NN modeling error and the gains of external disturbance are characterized by unknown upper bounds, which is more rational to establish the stability in the adaptive NN control. Filter-based modification terms are used in the update laws of unknown parameters to improve the transient performance. Finally, fault-tolerant control is developed to accommodate actuator failure. An illustrative example applying the adaptive controller to control a rigid robot arm shows the validation of the proposed controller.In this paper, an adaptive controller is developed for a class of multi-input and multioutput nonlinear systems with neural networks (NNs) used as a modeling tool. It is shown that all the signals in the closed-loop system with the proposed adaptive neural controller are globally uniformly bounded for any external input in . In our control design, the upper bound of the NN modeling error and the gains of external disturbance are characterized by unknown upper bounds, which is more rational to establish the stability in the adaptive NN control. Filter-based modification terms are used in the update laws of unknown parameters to improve the transient performance. Finally, fault-tolerant control is developed to accommodate actuator failure. An illustrative example applying the adaptive controller to control a rigid robot arm shows the validation of the proposed controller.

Induction of diapause and seasonal morphs in butterflies and other insects: knowns, unknowns and the challenge of integration

PubMed Central

Nylin, Sören

2013-01-01

The ‘choice’ of whether to enter diapause or to develop directly has profound effects on the life histories of insects, and may thus have cascading consequences such as seasonal morphs and other less obvious forms of seasonal plasticity. Present knowledge of the control of diapause and seasonal morphs at the physiological and molecular levels is briefly reviewed. Examples, mainly derived from personal research (primarily on butterflies), are given as a starting point with the aim of outlining areas of research that are still poorly understood. These include: the role of the direction of change in photoperiod; the role of factors such as temperature and diet in modifying the photoperiodic responses; and the role of sex, parental effects and sex linkage on photoperiodic control. More generally, there is still a limited understanding of how external cues and physiological pathways regulating various traits are interconnected via gene action to form a co-adapted complete phenotype that is adaptive in the wild despite environmental fluctuation and change. PMID:23894219

A directed-overflow and damage-control N -glycosidase in riboflavin biosynthesis

DOE PAGES

Frelin, Océane; Huang, Lili; Hasnain, Ghulam; ...

2015-02-15

Plants and bacteria synthesize the essential human micronutrient riboflavin (vitamin B2) via the same multistep pathway. The early intermediates of this pathway are notoriously reactive, and may be overproduced in vivo because riboflavin biosynthesis enzymes lack feedback controls. Here we demonstrate disposal of riboflavin intermediates by COG3236 (DUF1768), a protein of previously unknown function that is fused to two different riboflavin pathway enzymes in plants and bacteria (RIBR and RibA, respectively). We present cheminformatic, biochemical, genetic, and genomic evidence to show that: (i) plant and bacterial COG3236 proteins cleave the N-glycosidic bond of the first two intermediates of riboflavin biosynthesis,more » yielding relatively innocuous products; (ii) certain COG3236 proteins are in a multienzyme riboflavin biosynthesis complex that gives them privileged access to riboflavin intermediates; and (iii) COG3236 action in Arabidopsis thaliana and Escherichia coli helps maintain flavin levels. We find COG3236 proteins thus illustrate two emerging principles in chemical biology: directed overflow metabolism, in which excess flux is diverted out of a pathway, and the pre-emption of damage from reactive metabolites.« less

Opponent and bidirectional control of movement velocity in the basal ganglia

PubMed Central

Yttri, Eric A.

2016-01-01

For goal-directed behavior it is critical that we can both select the appropriate action and learn to modify the underlying movements (e.g. the pitch of a note or velocity of a reach) to improve outcomes. The basal ganglia are a critical nexus where circuits necessary for the production of behavior, such as neocortex and thalamus, are integrated with reward signaling 1 to reinforce successful, purposive actions 2. Dorsal striatum, a major input structure of basal ganglia is composed of two opponent pathways, direct and indirect, thought to select actions that elicit positive outcomes or suppress actions that do not, respectively 3,4. Activity-dependent plasticity modulated by reward is thought to be sufficient for selecting actions in striatum 5,6. Although perturbations of basal ganglia function produce profound changes in movement 7, it remains unknown whether activity-dependent plasticity is sufficient to produce learned changes in movement kinematics, such as velocity. Here we used cell-type specific stimulation delivered in closed-loop during movement to demonstrate that activity in either the direct or indirect pathway is sufficient to produce specific and sustained increases or decreases in velocity without affecting action selection or motivation. These behavioral changes were a form of learning that accumulated over trials, persisted after the cessation of stimulation, and were abolished in the presence of dopamine antagonists. Our results reveal that the direct and indirect pathways can each bidirectionally control movement velocity, demonstrating unprecedented specificity and flexibility in the control of volition by the basal ganglia. PMID:27135927

Iterative Adaptive Dynamic Programming for Solving Unknown Nonlinear Zero-Sum Game Based on Online Data.

PubMed

Zhu, Yuanheng; Zhao, Dongbin; Li, Xiangjun

2017-03-01

H ∞ control is a powerful method to solve the disturbance attenuation problems that occur in some control systems. The design of such controllers relies on solving the zero-sum game (ZSG). But in practical applications, the exact dynamics is mostly unknown. Identification of dynamics also produces errors that are detrimental to the control performance. To overcome this problem, an iterative adaptive dynamic programming algorithm is proposed in this paper to solve the continuous-time, unknown nonlinear ZSG with only online data. A model-free approach to the Hamilton-Jacobi-Isaacs equation is developed based on the policy iteration method. Control and disturbance policies and value are approximated by neural networks (NNs) under the critic-actor-disturber structure. The NN weights are solved by the least-squares method. According to the theoretical analysis, our algorithm is equivalent to a Gauss-Newton method solving an optimization problem, and it converges uniformly to the optimal solution. The online data can also be used repeatedly, which is highly efficient. Simulation results demonstrate its feasibility to solve the unknown nonlinear ZSG. When compared with other algorithms, it saves a significant amount of online measurement time.

Approximation-Based Adaptive Neural Tracking Control of Nonlinear MIMO Unknown Time-Varying Delay Systems With Full State Constraints.

PubMed

Li, Da-Peng; Li, Dong-Juan; Liu, Yan-Jun; Tong, Shaocheng; Chen, C L Philip

2017-10-01

This paper deals with the tracking control problem for a class of nonlinear multiple input multiple output unknown time-varying delay systems with full state constraints. To overcome the challenges which cause by the appearances of the unknown time-varying delays and full-state constraints simultaneously in the systems, an adaptive control method is presented for such systems for the first time. The appropriate Lyapunov-Krasovskii functions and a separation technique are employed to eliminate the effect of unknown time-varying delays. The barrier Lyapunov functions are employed to prevent the violation of the full state constraints. The singular problems are dealt with by introducing the signal function. Finally, it is proven that the proposed method can both guarantee the good tracking performance of the systems output, all states are remained in the constrained interval and all the closed-loop signals are bounded in the design process based on choosing appropriate design parameters. The practicability of the proposed control technique is demonstrated by a simulation study in this paper.

Structural control and health monitoring of building structures with unknown ground excitations: Experimental investigation

NASA Astrophysics Data System (ADS)

He, Jia; Xu, You-Lin; Zhan, Sheng; Huang, Qin

2017-03-01

When health monitoring system and vibration control system both are required for a building structure, it will be beneficial and cost-effective to integrate these two systems together for creating a smart building structure. Recently, on the basis of extended Kalman filter (EKF), a time-domain integrated approach was proposed for the identification of structural parameters of the controlled buildings with unknown ground excitations. The identified physical parameters and structural state vectors were then utilized to determine the control force for vibration suppression. In this paper, the possibility of establishing such a smart building structure with the function of simultaneous damage detection and vibration suppression was explored experimentally. A five-story shear building structure equipped with three magneto-rheological (MR) dampers was built. Four additional columns were added to the building model, and several damage scenarios were then simulated by symmetrically cutting off these columns in certain stories. Two sets of earthquakes, i.e. Kobe earthquake and Northridge earthquake, were considered as seismic input and assumed to be unknown during the tests. The structural parameters and the unknown ground excitations were identified during the tests by using the proposed identification method with the measured control forces. Based on the identified structural parameters and system states, a switching control law was employed to adjust the current applied to the MR dampers for the purpose of vibration attenuation. The experimental results show that the presented approach is capable of satisfactorily identifying structural damages and unknown excitations on one hand and significantly mitigating the structural vibration on the other hand.

Indirect adaptive fuzzy fault-tolerant tracking control for MIMO nonlinear systems with actuator and sensor failures.

PubMed

Bounemeur, Abdelhamid; Chemachema, Mohamed; Essounbouli, Najib

2018-05-10

In this paper, an active fuzzy fault tolerant tracking control (AFFTTC) scheme is developed for a class of multi-input multi-output (MIMO) unknown nonlinear systems in the presence of unknown actuator faults, sensor failures and external disturbance. The developed control scheme deals with four kinds of faults for both sensors and actuators. The bias, drift, and loss of accuracy additive faults are considered along with the loss of effectiveness multiplicative fault. A fuzzy adaptive controller based on back-stepping design is developed to deal with actuator failures and unknown system dynamics. However, an additional robust control term is added to deal with sensor faults, approximation errors, and external disturbances. Lyapunov theory is used to prove the stability of the closed loop system. Numerical simulations on a quadrotor are presented to show the effectiveness of the proposed approach. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Distributed adaptive neural network control for a class of heterogeneous nonlinear multi-agent systems subject to actuation failures

NASA Astrophysics Data System (ADS)

Cui, Bing; Zhao, Chunhui; Ma, Tiedong; Feng, Chi

2017-02-01

In this paper, the cooperative adaptive consensus tracking problem for heterogeneous nonlinear multi-agent systems on directed graph is addressed. Each follower is modelled as a general nonlinear system with the unknown and nonidentical nonlinear dynamics, disturbances and actuator failures. Cooperative fault tolerant neural network tracking controllers with online adaptive learning features are proposed to guarantee that all agents synchronise to the trajectory of one leader with bounded adjustable synchronisation errors. With the help of linear quadratic regulator-based optimal design, a graph-dependent Lyapunov proof provides error bounds that depend on the graph topology, one virtual matrix and some design parameters. Of particular interest is that if the control gain is selected appropriately, the proposed control scheme can be implemented in a unified framework no matter whether there are faults or not. Furthermore, the fault detection and isolation are not needed to implement. Finally, a simulation is given to verify the effectiveness of the proposed method.

Simulated thought insertion: Influencing the sense of agency using deception and magic.

PubMed

Olson, Jay A; Landry, Mathieu; Appourchaux, Krystèle; Raz, Amir

2016-07-01

In order to study the feeling of control over decisions, we told 60 participants that a neuroimaging machine could read and influence their thoughts. While inside a mock brain scanner, participants chose arbitrary numbers in two similar tasks. In the Mind-Reading Task, the scanner appeared to guess the participants' numbers; in the Mind-Influencing Task, it appeared to influence their choice of numbers. We predicted that participants would feel less voluntary control over their decisions when they believed that the scanner was influencing their choices. As predicted, participants felt less control and made slower decisions in the Mind-Influencing Task compared to the Mind-Reading Task. A second study replicated these findings. Participants' experience of the ostensible influence varied, with some reporting an unknown source directing them towards specific numbers. This simulated thought insertion paradigm can therefore influence feelings of voluntary control and may help model symptoms of mental disorders. Copyright © 2016 Elsevier Inc. All rights reserved.

Enhanced Engine Performance During Emergency Operation Using a Model-Based Engine Control Architecture

NASA Technical Reports Server (NTRS)

Csank, Jeffrey T.; Connolly, Joseph W.

2016-01-01

This paper discusses the design and application of model-based engine control (MBEC) for use during emergency operation of the aircraft. The MBEC methodology is applied to the Commercial Modular Aero-Propulsion System Simulation 40k (CMAPSS40k) and features an optimal tuner Kalman Filter (OTKF) to estimate unmeasured engine parameters, which can then be used for control. During an emergency scenario, normally-conservative engine operating limits may be relaxed to increase the performance of the engine and overall survivability of the aircraft; this comes at the cost of additional risk of an engine failure. The MBEC architecture offers the advantage of estimating key engine parameters that are not directly measureable. Estimating the unknown parameters allows for tighter control over these parameters, and on the level of risk the engine will operate at. This will allow the engine to achieve better performance than possible when operating to more conservative limits on a related, measurable parameter.

Enhanced Engine Performance During Emergency Operation Using a Model-Based Engine Control Architecture

NASA Technical Reports Server (NTRS)

Csank, Jeffrey T.; Connolly, Joseph W.

2015-01-01

This paper discusses the design and application of model-based engine control (MBEC) for use during emergency operation of the aircraft. The MBEC methodology is applied to the Commercial Modular Aero-Propulsion System Simulation 40,000 (CMAPSS40,000) and features an optimal tuner Kalman Filter (OTKF) to estimate unmeasured engine parameters, which can then be used for control. During an emergency scenario, normally-conservative engine operating limits may be relaxed to increase the performance of the engine and overall survivability of the aircraft; this comes at the cost of additional risk of an engine failure. The MBEC architecture offers the advantage of estimating key engine parameters that are not directly measureable. Estimating the unknown parameters allows for tighter control over these parameters, and on the level of risk the engine will operate at. This will allow the engine to achieve better performance than possible when operating to more conservative limits on a related, measurable parameter.

Adaptive Neural Networks Decentralized FTC Design for Nonstrict-Feedback Nonlinear Interconnected Large-Scale Systems Against Actuator Faults.

PubMed

Li, Yongming; Tong, Shaocheng

The problem of active fault-tolerant control (FTC) is investigated for the large-scale nonlinear systems in nonstrict-feedback form. The nonstrict-feedback nonlinear systems considered in this paper consist of unstructured uncertainties, unmeasured states, unknown interconnected terms, and actuator faults (e.g., bias fault and gain fault). A state observer is designed to solve the unmeasurable state problem. Neural networks (NNs) are used to identify the unknown lumped nonlinear functions so that the problems of unstructured uncertainties and unknown interconnected terms can be solved. By combining the adaptive backstepping design principle with the combination Nussbaum gain function property, a novel NN adaptive output-feedback FTC approach is developed. The proposed FTC controller can guarantee that all signals in all subsystems are bounded, and the tracking errors for each subsystem converge to a small neighborhood of zero. Finally, numerical results of practical examples are presented to further demonstrate the effectiveness of the proposed control strategy.The problem of active fault-tolerant control (FTC) is investigated for the large-scale nonlinear systems in nonstrict-feedback form. The nonstrict-feedback nonlinear systems considered in this paper consist of unstructured uncertainties, unmeasured states, unknown interconnected terms, and actuator faults (e.g., bias fault and gain fault). A state observer is designed to solve the unmeasurable state problem. Neural networks (NNs) are used to identify the unknown lumped nonlinear functions so that the problems of unstructured uncertainties and unknown interconnected terms can be solved. By combining the adaptive backstepping design principle with the combination Nussbaum gain function property, a novel NN adaptive output-feedback FTC approach is developed. The proposed FTC controller can guarantee that all signals in all subsystems are bounded, and the tracking errors for each subsystem converge to a small neighborhood of zero. Finally, numerical results of practical examples are presented to further demonstrate the effectiveness of the proposed control strategy.

Data-driven adaptive fractional order PI control for PMSM servo system with measurement noise and data dropouts.

PubMed

Xie, Yuanlong; Tang, Xiaoqi; Song, Bao; Zhou, Xiangdong; Guo, Yixuan

2018-04-01

In this paper, data-driven adaptive fractional order proportional integral (AFOPI) control is presented for permanent magnet synchronous motor (PMSM) servo system perturbed by measurement noise and data dropouts. The proposed method directly exploits the closed-loop process data for the AFOPI controller design under unknown noise distribution and data missing probability. Firstly, the proposed method constructs the AFOPI controller tuning problem as a parameter identification problem using the modified l p norm virtual reference feedback tuning (VRFT). Then, iteratively reweighted least squares is integrated into the l p norm VRFT to give a consistent compensation solution for the AFOPI controller. The measurement noise and data dropouts are estimated and eliminated by feedback compensation periodically, so that the AFOPI controller is updated online to accommodate the time-varying operating conditions. Moreover, the convergence and stability are guaranteed by mathematical analysis. Finally, the effectiveness of the proposed method is demonstrated both on simulations and experiments implemented on a practical PMSM servo system. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Comparing electronic news media reports of potential bioterrorism-related incidents involving unknown white powder to reports received by the United States Centers for Disease Control and Prevention and the Federal Bureau of Investigation: U.S.A., 2009-2011.

PubMed

Fajardo, Geroncio C; Posid, Joseph; Papagiotas, Stephen; Lowe, Luis

2015-01-01

There have been periodic electronic news media reports of potential bioterrorism-related incidents involving unknown substances (often referred to as "white powder") since the 2001 intentional dissemination of Bacillus anthracis through the U.S. Postal System. This study reviewed the number of unknown "white powder" incidents reported online by the electronic news media and compared them with unknown "white powder" incidents reported to the U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Federal Bureau of Investigation (FBI) during a 2-year period from June 1, 2009 and May 31, 2011. Results identified 297 electronic news media reports, 538 CDC reports, and 384 FBI reports of unknown "white powder." This study showed different unknown "white powder" incidents captured by each of the three sources. However, the authors could not determine the public health implications of this discordance. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

1. Historic American Buildings Survey Photocopy of old view, direction ...

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

1. Historic American Buildings Survey Photocopy of old view, direction and date unknown From collection of the Kansas City Museum of History and Science, Kansas City, Mo. - Longview Farm, Summer Camp, Longview Road, Lees Summit, Jackson County, MO

Terminal sliding mode tracking control for a class of SISO uncertain nonlinear systems.

PubMed

Chen, Mou; Wu, Qing-Xian; Cui, Rong-Xin

2013-03-01

In this paper, the terminal sliding mode tracking control is proposed for the uncertain single-input and single-output (SISO) nonlinear system with unknown external disturbance. For the unmeasured disturbance of nonlinear systems, terminal sliding mode disturbance observer is presented. The developed disturbance observer can guarantee the disturbance approximation error to converge to zero in the finite time. Based on the output of designed disturbance observer, the terminal sliding mode tracking control is presented for uncertain SISO nonlinear systems. Subsequently, terminal sliding mode tracking control is developed using disturbance observer technique for the uncertain SISO nonlinear system with control singularity and unknown non-symmetric input saturation. The effects of the control singularity and unknown input saturation are combined with the external disturbance which is approximated using the disturbance observer. Under the proposed terminal sliding mode tracking control techniques, the finite time convergence of all closed-loop signals are guaranteed via Lyapunov analysis. Numerical simulation results are given to illustrate the effectiveness of the proposed terminal sliding mode tracking control. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

Prescribed performance distributed consensus control for nonlinear multi-agent systems with unknown dead-zone input

NASA Astrophysics Data System (ADS)

Cui, Guozeng; Xu, Shengyuan; Ma, Qian; Li, Yongmin; Zhang, Zhengqiang

2018-05-01

In this paper, the problem of prescribed performance distributed output consensus for higher-order non-affine nonlinear multi-agent systems with unknown dead-zone input is investigated. Fuzzy logical systems are utilised to identify the unknown nonlinearities. By introducing prescribed performance, the transient and steady performance of synchronisation errors are guaranteed. Based on Lyapunov stability theory and the dynamic surface control technique, a new distributed consensus algorithm for non-affine nonlinear multi-agent systems is proposed, which ensures cooperatively uniformly ultimately boundedness of all signals in the closed-loop systems and enables the output of each follower to synchronise with the leader within predefined bounded error. Finally, simulation examples are provided to demonstrate the effectiveness of the proposed control scheme.

Adaptive fuzzy wavelet network control of second order multi-agent systems with unknown nonlinear dynamics.

PubMed

Taheri, Mehdi; Sheikholeslam, Farid; Najafi, Majddedin; Zekri, Maryam

2017-07-01

In this paper, consensus problem is considered for second order multi-agent systems with unknown nonlinear dynamics under undirected graphs. A novel distributed control strategy is suggested for leaderless systems based on adaptive fuzzy wavelet networks. Adaptive fuzzy wavelet networks are employed to compensate for the effect of unknown nonlinear dynamics. Moreover, the proposed method is developed for leader following systems and leader following systems with state time delays. Lyapunov functions are applied to prove uniformly ultimately bounded stability of closed loop systems and to obtain adaptive laws. Three simulation examples are presented to illustrate the effectiveness of the proposed control algorithms. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Young inversion with multiple linked QTLs under selection in a hybrid zone.

PubMed

Lee, Cheng-Ruei; Wang, Baosheng; Mojica, Julius P; Mandáková, Terezie; Prasad, Kasavajhala V S K; Goicoechea, Jose Luis; Perera, Nadeesha; Hellsten, Uffe; Hundley, Hope N; Johnson, Jenifer; Grimwood, Jane; Barry, Kerrie; Fairclough, Stephen; Jenkins, Jerry W; Yu, Yeisoo; Kudrna, Dave; Zhang, Jianwei; Talag, Jayson; Golser, Wolfgang; Ghattas, Kathryn; Schranz, M Eric; Wing, Rod; Lysak, Martin A; Schmutz, Jeremy; Rokhsar, Daniel S; Mitchell-Olds, Thomas

2017-04-03

Fixed chromosomal inversions can reduce gene flow and promote speciation in two ways: by suppressing recombination and by carrying locally favoured alleles at multiple loci. However, it is unknown whether favoured mutations slowly accumulate on older inversions or if young inversions spread because they capture pre-existing adaptive quantitative trait loci (QTLs). By genetic mapping, chromosome painting and genome sequencing, we have identified a major inversion controlling ecologically important traits in Boechera stricta. The inversion arose since the last glaciation and subsequently reached local high frequency in a hybrid speciation zone. Furthermore, the inversion shows signs of positive directional selection. To test whether the inversion could have captured existing, linked QTLs, we crossed standard, collinear haplotypes from the hybrid zone and found multiple linked phenology QTLs within the inversion region. These findings provide the first direct evidence that linked, locally adapted QTLs may be captured by young inversions during incipient speciation.

Young inversion with multiple linked QTLs under selection in a hybrid zone

PubMed Central

Lee, Cheng-Ruei; Wang, Baosheng; Mojica, Julius; Mandáková, Terezie; Prasad, Kasavajhala V. S. K.; Goicoechea, Jose Luis; Perera, Nadeesha; Hellsten, Uffe; Hundley, Hope N.; Johnson, Jenifer; Grimwood, Jane; Barry, Kerrie; Fairclough, Stephen; Jenkins, Jerry W.; Yu, Yeisoo; Kudrna, Dave; Zhang, Jianwei; Talag, Jayson; Golser, Wolfgang; Ghattas, Katherine; Schranz, M. Eric; Wing, Rod; Lysak, Martin A.; Schmutz, Jeremy; Rokhsar, Daniel S.; Mitchell-Olds, Thomas

2017-01-01

Fixed chromosomal inversions can reduce gene flow and promote speciation in two ways: by suppressing recombination and by carrying locally favored alleles at multiple loci. However, it is unknown whether favored mutations slowly accumulate on older inversions or if young inversions spread because they capture preexisting adaptive Quantitative Trait Loci (QTLs). By genetic mapping, chromosome painting and genome sequencing we have identified a major inversion controlling ecologically important traits in Boechera stricta. The inversion arose since the last glaciation and subsequently reached local high frequency in a hybrid speciation zone. Furthermore, the inversion shows signs of positive directional selection. To test whether the inversion could have captured existing, linked QTLs, we crossed standard, collinear haplotypes from the hybrid zone and found multiple linked phenology QTLs within the inversion region. These findings provide the first direct evidence that linked, locally adapted QTLs may be captured by young inversions during incipient speciation. PMID:28812690

A simple electrostatic switch important in the activation of type I protein kinase A by cyclic AMP.

PubMed

Vigil, Dominico; Lin, Jung-Hsin; Sotriffer, Christoph A; Pennypacker, Juniper K; McCammon, J Andrew; Taylor, Susan S

2006-01-01

Cyclic AMP activates protein kinase A by binding to an inhibitory regulatory (R) subunit and releasing inhibition of the catalytic (C) subunit. Even though crystal structures of regulatory and catalytic subunits have been solved, the precise molecular mechanism by which cyclic AMP activates the kinase remains unknown. The dynamic properties of the cAMP binding domain in the absence of cAMP or C-subunit are also unknown. Here we report molecular-dynamics simulations and mutational studies of the RIalpha R-subunit that identify the C-helix as a highly dynamic switch which relays cAMP binding to the helical C-subunit binding regions. Furthermore, we identify an important salt bridge which links cAMP binding directly to the C-helix that is necessary for normal activation. Additional mutations show that a hydrophobic "hinge" region is not as critical for the cross-talk in PKA as it is in the homologous EPAC protein, illustrating how cAMP can control diverse functions using the evolutionarily conserved cAMP-binding domains.

Uncertainty contribution on the density of liquids due to unknown sinker temperature in hydrostatic weighing apparatus

NASA Astrophysics Data System (ADS)

Schiebl, M.; Zelenka, Z.; Buchner, C.; Pohl, R.; Steindl, D.

2018-02-01

In this study, the influence of the unknown sinker temperature on the measured density of liquids is evaluated. Generally, due to the intrinsic temperature instability of the heat bath temperature controller, the system will never reach thermal equilibrium but instead will oscillate around a mean temperature. The sinker temperature follows this temperature oscillation with a certain time lag. Since the sinker temperature is not measured directly in a hydrostatic weighing apparatus, the temperature of the sinker, and thus in turn the volume of the sinker, is not known exactly. As a consequence, this leads to uncertainty in the value of the density of the liquid. From an analysis of the volume relaxation of the sinker immersed into a heat bath with time-dependent temperature characteristics, the heat transfer coefficient can be estimated, and thus a characteristic time constant for achieving quasi thermal equilibrium for a hydrostatic weighing apparatus is proposed. Additionally, from a theoretical analysis of the transient behavior of the sinker volume, the systematic deviation of the theoretical to the actual measured liquid density is calculated.

Idiopathic slow transit constipation and megacolon are not associated with neurturin mutations.

PubMed

Chen, B; Knowles, C H; Scott, M; Anand, P; Williams, N S; Milbrandt, J; Tam, P K H

2002-10-01

Chronic idiopathic slow-transit constipation (ISTC) and idiopathic megacolon (IMC) are early-onset gastrointestinal motility disorders of unknown aetiology. The gene encoding the neurotrophic factor neurturin may be a candidate for these disorders, as neurturin-deficient mice have a similar enteric phenotype. In the present study, we tested this hypothesis. Genomic DNA from 26 cases of chronic idiopathic STC [with a family history of constipation in 15 (58%) and Hirschsprung's disease in two (8%)], and five cases of IMC [two familial (40%)] was screened by direct DNA sequencing using the fluorescent dideoxy terminator method. Results were compared with published sequence data and 24 control DNAs. Our results revealed several previously unreported common sequence polymorphisms, but overall frequencies were comparable between patients and controls. We conclude that mutation of neurturin is not a frequent cause of ISTC or IMC.

Conjunction search revisited.

PubMed

Treisman, A; Sato, S

1990-08-01

Search for conjunctions of highly discriminable features can be rapid or even parallel. This article explores three possible accounts based on (a) perceptual segregation, (b) conjunction detectors, and (c) inhibition controlled separately by two or more distractor features. Search rates for conjunctions of color, size, orientation, and direction of motion correlated closely with an independent measure of perceptual segregation. However, they appeared unrelated to the physiology of single-unit responses. Each dimension contributed additively to conjunction search rates, suggesting that each was checked independently of the others. Unknown targets appear to be found only by serial search for each in turn. Searching through 4 sets of distractors was slower than searching through 2. The results suggest a modification of feature integration theory, in which attention is controlled not only by a unitary "window" but also by a form of feature-based inhibition.

Direct modulation of T-box riboswitch-controlled transcription by protein synthesis inhibitors

PubMed Central

Stamatopoulou, Vassiliki; Apostolidi, Maria; Li, Shuang; Lamprinou, Katerina; Papakyriakou, Athanasios

2017-01-01

Abstract Recently, it was discovered that exposure to mainstream antibiotics activate numerous bacterial riboregulators that control antibiotic resistance genes including metabolite-binding riboswitches and other transcription attenuators. However, the effects of commonly used antibiotics, many of which exhibit RNA-binding properties, on the widespread T-box riboswitches, remain unknown. In Staphylococcus aureus, a species-specific glyS T-box controls the supply of glycine for both ribosomal translation and cell wall synthesis, making it a promising target for next-generation antimicrobials. Here, we report that specific protein synthesis inhibitors could either significantly increase T-box-mediated transcription antitermination, while other compounds could suppress it, both in vitro and in vivo. In-line probing of the full-length T-box combined with molecular modelling and docking analyses suggest that the antibiotics that promote transcription antitermination stabilize the T-box:tRNA complex through binding specific positions on stem I and the Staphylococcal-specific stem Sa. By contrast, the antibiotics that attenuate T-box transcription bind to other positions on stem I and do not interact with stem Sa. Taken together, our results reveal that the transcription of essential genes controlled by T-box riboswitches can be directly modulated by commonly used protein synthesis inhibitors. These findings accentuate the regulatory complexities of bacterial response to antimicrobials that involve multiple riboregulators. PMID:28973457

PDGF controls contact inhibition of locomotion by regulating N-cadherin during neural crest migration.

PubMed

Bahm, Isabel; Barriga, Elias H; Frolov, Antonina; Theveneau, Eric; Frankel, Paul; Mayor, Roberto

2017-07-01

A fundamental property of neural crest (NC) migration is contact inhibition of locomotion (CIL), a process by which cells change their direction of migration upon cell contact. CIL has been proven to be essential for NC migration in amphibians and zebrafish by controlling cell polarity in a cell contact-dependent manner. Cell contact during CIL requires the participation of the cell adhesion molecule N-cadherin, which starts to be expressed by NC cells as a consequence of the switch between E- and N-cadherins during epithelial-to-mesenchymal transition (EMT). However, the mechanism that controls the upregulation of N-cadherin remains unknown. Here, we show that platelet-derived growth factor receptor alpha (PDGFRα) and its ligand platelet-derived growth factor A (PDGF-A) are co-expressed in migrating cranial NC. Inhibition of PDGF-A/PDGFRα blocks NC migration by inhibiting N-cadherin and, consequently, impairing CIL. Moreover, we identify phosphatidylinositol-3-kinase (PI3K)/AKT as a downstream effector of the PDGFRα cellular response during CIL. Our results lead us to propose PDGF-A/PDGFRα signalling as a tissue-autonomous regulator of CIL by controlling N-cadherin upregulation during EMT. Finally, we show that once NC cells have undergone EMT, the same PDGF-A/PDGFRα works as an NC chemoattractant, guiding their directional migration. © 2017. Published by The Company of Biologists Ltd.

Improved oxygenation during standing performance of deep breathing exercises with positive expiratory pressure after cardiac surgery: A randomized controlled trial.

PubMed

Pettersson, Henrik; Faager, Gun; Westerdahl, Elisabeth

2015-09-01

Breathing exercises after cardiac surgery are often performed in a sitting position. It is unknown whether oxygenation would be better in the standing position. The aim of this study was to evaluate oxygenation and subjective breathing ability during sitting vs standing performance of deep breathing exercises on the second day after cardiac surgery. Patients undergoing coronary artery bypass grafting (n = 189) were randomized to sitting (controls) or standing. Both groups performed 3 × 10 deep breaths with a positive expiratory pressure device. Peripheral oxygen saturation was measured before, directly after, and 15 min after the intervention. Subjective breathing ability, blood pressure, heart rate, and pain were assessed. Oxygenation improved significantly in the standing group compared with controls directly after the breathing exercises (p < 0.001) and after 15 min rest (p = 0.027). The standing group reported better deep breathing ability compared with controls (p = 0.004). A slightly increased heart rate was found in the standing group (p = 0.047). After cardiac surgery, breathing exercises with positive expiratory pressure, performed in a standing position, significantly improved oxygenation and subjective breathing ability compared with sitting performance. Performance of breathing exercises in the standing position is feasible and could be a valuable treatment for patients with postoperative hypoxaemia.

Direct modulation of T-box riboswitch-controlled transcription by protein synthesis inhibitors.

PubMed

Stamatopoulou, Vassiliki; Apostolidi, Maria; Li, Shuang; Lamprinou, Katerina; Papakyriakou, Athanasios; Zhang, Jinwei; Stathopoulos, Constantinos

2017-09-29

Recently, it was discovered that exposure to mainstream antibiotics activate numerous bacterial riboregulators that control antibiotic resistance genes including metabolite-binding riboswitches and other transcription attenuators. However, the effects of commonly used antibiotics, many of which exhibit RNA-binding properties, on the widespread T-box riboswitches, remain unknown. In Staphylococcus aureus, a species-specific glyS T-box controls the supply of glycine for both ribosomal translation and cell wall synthesis, making it a promising target for next-generation antimicrobials. Here, we report that specific protein synthesis inhibitors could either significantly increase T-box-mediated transcription antitermination, while other compounds could suppress it, both in vitro and in vivo. In-line probing of the full-length T-box combined with molecular modelling and docking analyses suggest that the antibiotics that promote transcription antitermination stabilize the T-box:tRNA complex through binding specific positions on stem I and the Staphylococcal-specific stem Sa. By contrast, the antibiotics that attenuate T-box transcription bind to other positions on stem I and do not interact with stem Sa. Taken together, our results reveal that the transcription of essential genes controlled by T-box riboswitches can be directly modulated by commonly used protein synthesis inhibitors. These findings accentuate the regulatory complexities of bacterial response to antimicrobials that involve multiple riboregulators. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

Adaptive Control of Non-Minimum Phase Modal Systems Using Residual Mode Filters2. Parts 1 and 2

NASA Technical Reports Server (NTRS)

Balas, Mark J.; Frost, Susan

2011-01-01

Many dynamic systems containing a large number of modes can benefit from adaptive control techniques, which are well suited to applications that have unknown parameters and poorly known operating conditions. In this paper, we focus on a direct adaptive control approach that has been extended to handle adaptive rejection of persistent disturbances. We extend this adaptive control theory to accommodate problematic modal subsystems of a plant that inhibit the adaptive controller by causing the open-loop plant to be non-minimum phase. We will modify the adaptive controller with a Residual Mode Filter (RMF) to compensate for problematic modal subsystems, thereby allowing the system to satisfy the requirements for the adaptive controller to have guaranteed convergence and bounded gains. This paper will be divided into two parts. Here in Part I we will review the basic adaptive control approach and introduce the primary ideas. In Part II, we will present the RMF methodology and complete the proofs of all our results. Also, we will apply the above theoretical results to a simple flexible structure example to illustrate the behavior with and without the residual mode filter.

A traffic priority language for collision-free navigation of autonomous mobile robots in dynamic environments.

PubMed

Bourbakis, N G

1997-01-01

This paper presents a generic traffic priority language, called KYKLOFORTA, used by autonomous robots for collision-free navigation in a dynamic unknown or known navigation space. In a previous work by X. Grossmman (1988), a set of traffic control rules was developed for the navigation of the robots on the lines of a two-dimensional (2-D) grid and a control center coordinated and synchronized their movements. In this work, the robots are considered autonomous: they are moving anywhere and in any direction inside the free space, and there is no need of a central control to coordinate and synchronize them. The requirements for each robot are i) visual perception, ii) range sensors, and iii) the ability of each robot to detect other moving objects in the same free navigation space, define the other objects perceived size, their velocity and their directions. Based on these assumptions, a traffic priority language is needed for each robot, making it able to decide during the navigation and avoid possible collision with other moving objects. The traffic priority language proposed here is based on a set of primitive traffic priority alphabet and rules which compose pattern of corridors for the application of the traffic priority rules.

Regulation of synaptic vesicle recycling by complex formation between intersectin 1 and the clathrin adaptor complex AP2

PubMed Central

Pechstein, Arndt; Bacetic, Jelena; Vahedi-Faridi, Ardeschir; Gromova, Kira; Sundborger, Anna; Tomlin, Nikolay; Krainer, Georg; Vorontsova, Olga; Schäfer, Johannes G.; Owe, Simen G.; Cousin, Michael A.; Saenger, Wolfram; Shupliakov, Oleg; Haucke, Volker

2010-01-01

Clathrin-mediated synaptic vesicle (SV) recycling involves the spatiotemporally controlled assembly of clathrin coat components at phosphatidylinositiol (4, 5)-bisphosphate [PI(4,5)P2]-enriched membrane sites within the periactive zone. Such spatiotemporal control is needed to coordinate SV cargo sorting with clathrin/AP2 recruitment and to restrain membrane fission and synaptojanin-mediated uncoating until membrane deformation and clathrin coat assembly are completed. The molecular events underlying these control mechanisms are unknown. Here we show that the endocytic SH3 domain-containing accessory protein intersectin 1 scaffolds the endocytic process by directly associating with the clathrin adaptor AP2. Acute perturbation of the intersectin 1-AP2 interaction in lamprey synapses in situ inhibits the onset of SV recycling. Structurally, complex formation can be attributed to the direct association of hydrophobic peptides within the intersectin 1 SH3A-B linker region with the “side sites” of the AP2 α- and β-appendage domains. AP2 appendage association of the SH3A-B linker region inhibits binding of the inositol phosphatase synaptojanin 1 to intersectin 1. These data identify the intersectin-AP2 complex as an important regulator of clathrin-mediated SV recycling in synapses. PMID:20160082

Adaptive neural control for dual-arm coordination of humanoid robot with unknown nonlinearities in output mechanism.

PubMed

Liu, Zhi; Chen, Ci; Zhang, Yun; Chen, C L P

2015-03-01

To achieve an excellent dual-arm coordination of the humanoid robot, it is essential to deal with the nonlinearities existing in the system dynamics. The literatures so far on the humanoid robot control have a common assumption that the problem of output hysteresis could be ignored. However, in the practical applications, the output hysteresis is widely spread; and its existing limits the motion/force performances of the robotic system. In this paper, an adaptive neural control scheme, which takes the unknown output hysteresis and computational efficiency into account, is presented and investigated. In the controller design, the prior knowledge of system dynamics is assumed to be unknown. The motion error is guaranteed to converge to a small neighborhood of the origin by Lyapunov's stability theory. Simultaneously, the internal force is kept bounded and its error can be made arbitrarily small.

Adaptive Fuzzy Output-Constrained Fault-Tolerant Control of Nonlinear Stochastic Large-Scale Systems With Actuator Faults.

PubMed

Li, Yongming; Ma, Zhiyao; Tong, Shaocheng

2017-09-01

The problem of adaptive fuzzy output-constrained tracking fault-tolerant control (FTC) is investigated for the large-scale stochastic nonlinear systems of pure-feedback form. The nonlinear systems considered in this paper possess the unstructured uncertainties, unknown interconnected terms and unknown nonaffine nonlinear faults. The fuzzy logic systems are employed to identify the unknown lumped nonlinear functions so that the problems of structured uncertainties can be solved. An adaptive fuzzy state observer is designed to solve the nonmeasurable state problem. By combining the barrier Lyapunov function theory, adaptive decentralized and stochastic control principles, a novel fuzzy adaptive output-constrained FTC approach is constructed. All the signals in the closed-loop system are proved to be bounded in probability and the system outputs are constrained in a given compact set. Finally, the applicability of the proposed controller is well carried out by a simulation example.

Identification of linear system models and state estimators for controls

NASA Technical Reports Server (NTRS)

Chen, Chung-Wen

1992-01-01

The following paper is presented in viewgraph format and covers topics including: (1) linear state feedback control system; (2) Kalman filter state estimation; (3) relation between residual and stochastic part of output; (4) obtaining Kalman filter gain; (5) state estimation under unknown system model and unknown noises; and (6) relationship between filter Markov parameters and system Markov parameters.

Distributed robust adaptive control of high order nonlinear multi agent systems.

PubMed

Hashemi, Mahnaz; Shahgholian, Ghazanfar

2018-03-01

In this paper, a robust adaptive neural network based controller is presented for multi agent high order nonlinear systems with unknown nonlinear functions, unknown control gains and unknown actuator failures. At first, Neural Network (NN) is used to approximate the nonlinear uncertainty terms derived from the controller design procedure for the followers. Then, a novel distributed robust adaptive controller is developed by combining the backstepping method and the Dynamic Surface Control (DSC) approach. The proposed controllers are distributed in the sense that the designed controller for each follower agent only requires relative state information between itself and its neighbors. By using the Young's inequality, only few parameters need to be tuned regardless of NN nodes number. Accordingly, the problems of dimensionality curse and explosion of complexity are counteracted, simultaneously. New adaptive laws are designed by choosing the appropriate Lyapunov-Krasovskii functionals. The proposed approach proves the boundedness of all the closed-loop signals in addition to the convergence of the distributed tracking errors to a small neighborhood of the origin. Simulation results indicate that the proposed controller is effective and robust. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Robust adaptive precision motion control of hydraulic actuators with valve dead-zone compensation.

PubMed

Deng, Wenxiang; Yao, Jianyong; Ma, Dawei

2017-09-01

This paper addresses the high performance motion control of hydraulic actuators with parametric uncertainties, unmodeled disturbances and unknown valve dead-zone. By constructing a smooth dead-zone inverse, a robust adaptive controller is proposed via backstepping method, in which adaptive law is synthesized to deal with parametric uncertainties and a continuous nonlinear robust control law to suppress unmodeled disturbances. Since the unknown dead-zone parameters can be estimated by adaptive law and then the effect of dead-zone can be compensated effectively via inverse operation, improved tracking performance can be expected. In addition, the disturbance upper bounds can also be updated online by adaptive laws, which increases the controller operability in practice. The Lyapunov based stability analysis shows that excellent asymptotic output tracking with zero steady-state error can be achieved by the developed controller even in the presence of unmodeled disturbance and unknown valve dead-zone. Finally, the proposed control strategy is experimentally tested on a servovalve controlled hydraulic actuation system subjected to an artificial valve dead-zone. Comparative experimental results are obtained to illustrate the effectiveness of the proposed control scheme. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Control of Inhibition by the Direct Action of Cannabinoids on GABAA Receptors.

PubMed

Golovko, Tatiana; Min, Rogier; Lozovaya, Natalia; Falconer, Caroline; Yatsenko, Natalia; Tsintsadze, Timur; Tsintsadze, Vera; Ledent, Catherine; Harvey, Robert J; Belelli, Delia; Lambert, Jeremy J; Rozov, Andrei; Burnashev, Nail

2015-09-01

Cannabinoids are known to regulate inhibitory synaptic transmission via activation of presynaptic G protein-coupled cannabinoid CB1 receptors (CB1Rs). Additionally, recent studies suggest that cannabinoids can also directly interact with recombinant GABAA receptors (GABAARs), potentiating currents activated by micromolar concentrations of γ-aminobutyric acid (GABA). However, the impact of this direct interaction on GABAergic inhibition in central nervous system is unknown. Here we report that currents mediated by recombinant GABAARs activated by high (synaptic) concentrations of GABA as well as GABAergic inhibitory postsynaptic currents (IPSCs) at neocortical fast spiking (FS) interneuron to pyramidal neuron synapses are suppressed by exogenous and endogenous cannabinoids in a CB1R-independent manner. This IPSC suppression may account for disruption of inhibitory control of pyramidal neurons by FS interneurons. At FS interneuron to pyramidal neuron synapses, endocannabinoids induce synaptic low-pass filtering of GABAAR-mediated currents evoked by high-frequency stimulation. The CB1R-independent suppression of inhibition is synapse specific. It does not occur in CB1R containing hippocampal cholecystokinin-positive interneuron to pyramidal neuron synapses. Furthermore, in contrast to synaptic receptors, the activity of extrasynaptic GABAARs in neocortical pyramidal neurons is enhanced by cannabinoids in a CB1R-independent manner. Thus, cannabinoids directly interact differentially with synaptic and extrasynaptic GABAARs, providing a potent novel context-dependent mechanism for regulation of inhibition. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Long-Term Effects from Bacterial Meningitis in Childhood and Adolescence on Postural Control

PubMed Central

Petersen, Hannes; Patel, Mitesh; Ingason, Einar F.; Einarsson, Einar J.; Haraldsson, Ásgeir; Fransson, Per-Anders

2014-01-01

Bacterial meningitis in childhood is associated with cognitive deficiencies, sensorimotor impairments and motor dysfunction later in life. However, the long-term effects on postural control is largely unknown, e.g., whether meningitis subjects as adults fully can utilize visual information and adaptation to enhance stability. Thirty-six subjects (20 women, mean age 19.3 years) treated in childhood or adolescence for bacterial meningitis, and 25 controls (13 women, mean age 25.1 years) performed posturography with eyes open and closed under unperturbed and perturbed standing. The meningitis subjects were screened for subjective vertigo symptoms using a questionnaire, clinically tested with headshake and head thrust test, as well as their hearing was evaluated. Meningitis subjects were significantly more unstable than controls during unperturbed (p≤0.014) and perturbed standing, though while perturbed only with eyes open in anteroposterior direction (p = 0.034) whereas in lateral direction both with eyes open and closed (p<0.001). Meningitis subjects had poorer adaption ability to balance perturbations especially with eyes open, and they frequently reported symptoms of unsteadiness (88% of the subjects) and dizziness (81%), which was found significantly correlated to objectively decreased stability. Out of the 36 subjects only 3 had unilateral hearing impairment. Hence, survivors of childhood bacterial meningitis may suffer long-term disorders affecting postural control, and would greatly benefit if these common late effects became generally known so treatments can be developed and applied. PMID:25405756

Time-delay control of a magnetic levitated linear positioning system

NASA Technical Reports Server (NTRS)

Tarn, J. H.; Juang, K. Y.; Lin, C. E.

1994-01-01

In this paper, a high accuracy linear positioning system with a linear force actuator and magnetic levitation is proposed. By locating a permanently magnetized rod inside a current-carrying solenoid, the axial force is achieved by the boundary effect of magnet poles and utilized to power the linear motion, while the force for levitation is governed by Ampere's Law supplied with the same solenoid. With the levitation in a radial direction, there is hardly any friction between the rod and the solenoid. The high speed motion can hence be achieved. Besides, the axial force acting on the rod is a smooth function of rod position, so the system can provide nanometer resolution linear positioning to the molecule size. Since the force-position relation is highly nonlinear, and the mathematical model is derived according to some assumptions, such as the equivalent solenoid of the permanently magnetized rod, so there exists unknown dynamics in practical application. Thus 'robustness' is an important issue in controller design. Meanwhile the load effect reacts directly on the servo system without transmission elements, so the capability of 'disturbance rejection; is also required. With the above consideration, a time-delay control scheme is chosen and applied. By comparing the input-output relation and the mathematical model, the time-delay controller calculates an estimation of unmodeled dynamics and disturbances and then composes the desired compensation into the system. Effectiveness of the linear positioning system and control scheme are illustrated with simulation results.

The Information Available to a Moving Observer on Shape with Unknown, Isotropic BRDFs.

PubMed

Chandraker, Manmohan

2016-07-01

Psychophysical studies show motion cues inform about shape even with unknown reflectance. Recent works in computer vision have considered shape recovery for an object of unknown BRDF using light source or object motions. This paper proposes a theory that addresses the remaining problem of determining shape from the (small or differential) motion of the camera, for unknown isotropic BRDFs. Our theory derives a differential stereo relation that relates camera motion to surface depth, which generalizes traditional Lambertian assumptions. Under orthographic projection, we show differential stereo may not determine shape for general BRDFs, but suffices to yield an invariant for several restricted (still unknown) BRDFs exhibited by common materials. For the perspective case, we show that differential stereo yields the surface depth for unknown isotropic BRDF and unknown directional lighting, while additional constraints are obtained with restrictions on the BRDF or lighting. The limits imposed by our theory are intrinsic to the shape recovery problem and independent of choice of reconstruction method. We also illustrate trends shared by theories on shape from differential motion of light source, object or camera, to relate the hardness of surface reconstruction to the complexity of imaging setup.

Adaptive backstepping fault-tolerant control for flexible spacecraft with unknown bounded disturbances and actuator failures.

PubMed

Jiang, Ye; Hu, Qinglei; Ma, Guangfu

2010-01-01

In this paper, a robust adaptive fault-tolerant control approach to attitude tracking of flexible spacecraft is proposed for use in situations when there are reaction wheel/actuator failures, persistent bounded disturbances and unknown inertia parameter uncertainties. The controller is designed based on an adaptive backstepping sliding mode control scheme, and a sufficient condition under which this control law can render the system semi-globally input-to-state stable is also provided such that the closed-loop system is robust with respect to any disturbance within a quantifiable restriction on the amplitude, as well as the set of initial conditions, if the control gains are designed appropriately. Moreover, in the design, the control law does not need a fault detection and isolation mechanism even if the failure time instants, patterns and values on actuator failures are also unknown for the designers, as motivated from a practical spacecraft control application. In addition to detailed derivations of the new controller design and a rigorous sketch of all the associated stability and attitude error convergence proofs, illustrative simulation results of an application to flexible spacecraft show that high precise attitude control and vibration suppression are successfully achieved using various scenarios of controlling effective failures. 2009. Published by Elsevier Ltd.

Corrected and Republished from: BCL11A Is a Critical Component of a Transcriptional Network That Activates Recombinase Activating Gene Expression and V(D)J Recombination

PubMed Central

Lee, Baeck-Seung; Lee, Bum-Kyu; Iyer, Vishwanath R.; Sleckman, Barry P.; Shaffer, Arthur L.; Ippolito, Gregory C.

2017-01-01

ABSTRACT Recombination activating gene 1 (RAG1) and RAG2 are critical enzymes for initiating variable-diversity-joining [V(D)J] segment recombination, an essential process for antigen receptor expression and lymphocyte development. The BCL11A transcription factor is required for B cell and plasmacytoid dendritic cell (pDC) development, but its molecular function(s) in early B cell fate specification and commitment is unknown. We show here that the major B cell isoform, BCL11A-XL, binds directly to the RAG1 promoter as well as directly to regulatory regions of transcription factors previously implicated in both B cell and pDC development to activate RAG1 and RAG2 gene transcription in pro- and pre-B cells. We employed BCL11A overexpression with recombination substrates to demonstrate direct consequences of BCL11A/RAG modulation on V(D)J recombination. We conclude that BCL11A is a critical component of a transcriptional network that regulates B cell fate by controlling V(D)J recombination. PMID:29038163

Neurochemical and behavioral indices of exercise reward are independent of exercise controllability

PubMed Central

Herrera, Jonathan J; Fedynska, Sofiya; Ghasem, Parsa R; Wieman, Tyler; Clark, Peter J; Gray, Nathan; Loetz, Esteban; Campeau, Serge; Fleshner, Monika; Greenwood, Benjamin N

2016-01-01

Brain reward circuits are implicated in stress-related psychiatric disorders. Exercise reduces the incidence of stress-related disorders, but the contribution of exercise reward to stress resistance is unknown. Exercise-induced stress resistance is independent of exercise controllability; both voluntary and forced wheel running protect rats against anxiety- and depression-like behavioral consequences of stress. Voluntary exercise is a natural reward, but whether rats find forced wheel running rewarding is unknown. Moreover, the contribution of dopamine (DA) and striatal reward circuits to exercise reward is not well characterized. Adult, male rats were assigned to locked wheels, voluntary running (VR), or forced running (FR) groups. FR rats were forced to run in a pattern resembling rats' natural wheel running behavior. Both VR and FR increased the reward-related plasticity marker ΔFosB in the dorsal striatum (DS) and nucleus accumbens (NAc), and increased activity of DA neurons in the lateral ventral tegmental area (VTA), as revealed by immunohistochemistry for tyrosine hydroxylase (TH) and pCREB. Both VR and FR rats developed conditioned place preference (CPP) to the side of a CPP chamber paired with exercise. Re-exposure to the exercise-paired side of the CPP chamber elicited conditioned increases in cfos mRNA in direct pathway (dynorphin-positive) neurons in the DS and NAc in both VR and FR rats, and in TH-positive neurons in the lateral VTA of VR rats only. Results suggest that the rewarding effects of exercise are independent of exercise controllability and provide insight into the DA and striatal circuitries involved in exercise reward and exercise-induced stress resistance. PMID:26833814

Flying Drosophila stabilize their vision-based velocity controller by sensing wind with their antennae

PubMed Central

Fuller, Sawyer Buckminster; Straw, Andrew D.; Peek, Martin Y.; Murray, Richard M.; Dickinson, Michael H.

2014-01-01

Flies and other insects use vision to regulate their groundspeed in flight, enabling them to fly in varying wind conditions. Compared with mechanosensory modalities, however, vision requires a long processing delay (~100 ms) that might introduce instability if operated at high gain. Flies also sense air motion with their antennae, but how this is used in flight control is unknown. We manipulated the antennal function of fruit flies by ablating their aristae, forcing them to rely on vision alone to regulate groundspeed. Arista-ablated flies in flight exhibited significantly greater groundspeed variability than intact flies. We then subjected them to a series of controlled impulsive wind gusts delivered by an air piston and experimentally manipulated antennae and visual feedback. The results show that an antenna-mediated response alters wing motion to cause flies to accelerate in the same direction as the gust. This response opposes flying into a headwind, but flies regularly fly upwind. To resolve this discrepancy, we obtained a dynamic model of the fly’s velocity regulator by fitting parameters of candidate models to our experimental data. The model suggests that the groundspeed variability of arista-ablated flies is the result of unstable feedback oscillations caused by the delay and high gain of visual feedback. The antenna response drives active damping with a shorter delay (~20 ms) to stabilize this regulator, in exchange for increasing the effect of rapid wind disturbances. This provides insight into flies’ multimodal sensory feedback architecture and constitutes a previously unknown role for the antennae. PMID:24639532

Intrinsic K-Ras dynamics: A novel molecular dynamics data analysis method shows causality between residue pair motions

NASA Astrophysics Data System (ADS)

Vatansever, Sezen; Gümüş, Zeynep H.; Erman, Burak

2016-11-01

K-Ras is the most frequently mutated oncogene in human cancers, but there are still no drugs that directly target it in the clinic. Recent studies utilizing dynamics information show promising results for selectively targeting mutant K-Ras. However, despite extensive characterization, the mechanisms by which K-Ras residue fluctuations transfer allosteric regulatory information remain unknown. Understanding the direction of information flow can provide new mechanistic insights for K-Ras targeting. Here, we present a novel approach -conditional time-delayed correlations (CTC) - using the motions of all residue pairs of a protein to predict directionality in the allosteric regulation of the protein fluctuations. Analyzing nucleotide-dependent intrinsic K-Ras motions with the new approach yields predictions that agree with the literature, showing that GTP-binding stabilizes K-Ras motions and leads to residue correlations with relatively long characteristic decay times. Furthermore, our study is the first to identify driver-follower relationships in correlated motions of K-Ras residue pairs, revealing the direction of information flow during allosteric modulation of its nucleotide-dependent intrinsic activity: active K-Ras Switch-II region motions drive Switch-I region motions, while α-helix-3L7 motions control both. Our results provide novel insights for strategies that directly target mutant K-Ras.

Adaptive neural network backstepping control for a class of uncertain fractional-order chaotic systems with unknown backlash-like hysteresis

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

Wu, Yimin; Lv, Hui, E-mail: lvhui207@gmail.com

In this paper, we consider the control problem of a class of uncertain fractional-order chaotic systems preceded by unknown backlash-like hysteresis nonlinearities based on backstepping control algorithm. We model the hysteresis by using a differential equation. Based on the fractional Lyapunov stability criterion and the backstepping algorithm procedures, an adaptive neural network controller is driven. No knowledge of the upper bound of the disturbance and system uncertainty is required in our controller, and the asymptotical convergence of the tracking error can be guaranteed. Finally, we give two simulation examples to confirm our theoretical results.

Data-driven robust approximate optimal tracking control for unknown general nonlinear systems using adaptive dynamic programming method.

PubMed

Zhang, Huaguang; Cui, Lili; Zhang, Xin; Luo, Yanhong

2011-12-01

In this paper, a novel data-driven robust approximate optimal tracking control scheme is proposed for unknown general nonlinear systems by using the adaptive dynamic programming (ADP) method. In the design of the controller, only available input-output data is required instead of known system dynamics. A data-driven model is established by a recurrent neural network (NN) to reconstruct the unknown system dynamics using available input-output data. By adding a novel adjustable term related to the modeling error, the resultant modeling error is first guaranteed to converge to zero. Then, based on the obtained data-driven model, the ADP method is utilized to design the approximate optimal tracking controller, which consists of the steady-state controller and the optimal feedback controller. Further, a robustifying term is developed to compensate for the NN approximation errors introduced by implementing the ADP method. Based on Lyapunov approach, stability analysis of the closed-loop system is performed to show that the proposed controller guarantees the system state asymptotically tracking the desired trajectory. Additionally, the obtained control input is proven to be close to the optimal control input within a small bound. Finally, two numerical examples are used to demonstrate the effectiveness of the proposed control scheme.

Quantum Logic Networks for Probabilistic and Controlled Teleportation of Unknown Quantum States

NASA Astrophysics Data System (ADS)

Gao, Ting

2004-08-01

We present simplification schemes for probabilistic and controlled teleportation of the unknown quantum states of both one particle and two particles and construct efficient quantum logic networks for implementing the new schemes by means of the primitive operations consisting of single-qubit gates, two-qubit controlled-not gates, Von Neumann measurement, and classically controlled operations. In these schemes the teleportation are not always successful but with certain probability. The project supported by National Natural Science Foundation of China under Grant No. 10271081 and the Natural Science Foundation of Hebei Province of China under Grant No. A2004000141

Nonholonomic Ofject Tracking with Optical Sensors and Ofject Recognition Feedback

NASA Technical Reports Server (NTRS)

Goddard, R. E.; Hadaegh, F.

1994-01-01

Robotic controllers frequently operate under constraints. Often, the constraints are imperfectly or completely unknown. In this paper, the Lagrangian dynamics of a planar robot arm are expressed as a function of a globally unknown consraint.

Disturbance observer-based adaptive sliding mode hybrid projective synchronisation of identical fractional-order financial systems

NASA Astrophysics Data System (ADS)

Khan, Ayub; Tyagi, Arti

2018-05-01

In this paper, we have studied the hybrid projective synchronisation for incommensurate, integer and commensurate fractional-order financial systems with unknown disturbance. To tackle the problem of unknown bounded disturbance, fractional-order disturbance observer is designed to approximate the unknown disturbance. Further, we have introduced simple sliding mode surface and designed adaptive sliding mode controllers incorporating with the designed fractional-order disturbance observer to achieve a bounded hybrid projective synchronisation between two identical fractional-order financial model with different initial conditions. It is shown that the slave system with disturbance can be synchronised with the projection of the master system generated through state transformation. Simulation results are presented to ensure the validity and effectiveness of the proposed sliding mode control scheme in the presence of external bounded unknown disturbance. Also, synchronisation error for commensurate, integer and incommensurate fractional-order financial systems is studied in numerical simulation.

On the rejection of internal and external disturbances in a wind energy conversion system with direct-driven PMSG.

PubMed

Li, Shengquan; Zhang, Kezhao; Li, Juan; Liu, Chao

2016-03-01

This paper deals with the critical issue in a wind energy conversion system (WECS) based on a direct-driven permanent magnet synchronous generator (PMSG): the rejection of lumped disturbance, including the system uncertainties in the internal dynamics and unknown external forces. To simultaneously track the motor speed in real time and capture the maximum power, a maximum power point tracking strategy is proposed based on active disturbance rejection control (ADRC) theory. In real application, system inertia, drive torque and some other parameters change in a wide range with the variations of disturbances and wind speeds, which substantially degrade the performance of WECS. The ADRC design must incorporate the available model information into an extended state observer (ESO) to compensate the lumped disturbance efficiently. Based on this principle, a model-compensation ADRC is proposed in this paper. Simulation study is conducted to evaluate the performance of the proposed control strategy. It is shown that the effect of lumped disturbance is compensated in a more effective way compared with the traditional ADRC approach. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Compensator-based 6-DOF control for probe asteroid-orbital-frame hovering with actuator limitations

NASA Astrophysics Data System (ADS)

Liu, Xiaosong; Zhang, Peng; Liu, Keping; Li, Yuanchun

2016-05-01

This paper is concerned with 6-DOF control of a probe hovering in the orbital frame of an asteroid. Considering the requirements of the scientific instruments pointing direction and orbital position in practical missions, the coordinate control of relative attitude and orbit between the probe and target asteroid is imperative. A 6-DOF dynamic equation describing the relative translational and rotational motion of a probe in the asteroid's orbital frame is derived, taking the irregular gravitation, model and parameter uncertainties and external disturbances into account. An adaptive sliding mode controller is employed to guarantee the convergence of the state error, where the adaptation law is used to estimate the unknown upper bound of system uncertainty. Then the controller is improved to deal with the practical problem of actuator limitations by introducing a RBF neural network compensator, which is used to approximate the difference between the actual control with magnitude constraint and the designed nominal control law. The closed-loop system is proved to be asymptotically stable through the Lyapunov stability analysis. Numerical simulations are performed to compare the performances of the preceding designed control laws. Simulation results demonstrate the validity of the control scheme using the compensator-based adaptive sliding mode control law in the presence of actuator limitations, system uncertainty and external disturbance.

Light-triggered in vivo activation of adhesive peptides regulates cell adhesion, inflammation and vascularization of biomaterials.

PubMed

Lee, Ted T; García, José R; Paez, Julieta I; Singh, Ankur; Phelps, Edward A; Weis, Simone; Shafiq, Zahid; Shekaran, Asha; Del Campo, Aránzazu; García, Andrés J

2015-03-01

Materials engineered to elicit targeted cellular responses in regenerative medicine must display bioligands with precise spatial and temporal control. Although materials with temporally regulated presentation of bioadhesive ligands using external triggers, such as light and electric fields, have recently been realized for cells in culture, the impact of in vivo temporal ligand presentation on cell-material responses is unknown. Here, we present a general strategy to temporally and spatially control the in vivo presentation of bioligands using cell-adhesive peptides with a protecting group that can be easily removed via transdermal light exposure to render the peptide fully active. We demonstrate that non-invasive, transdermal time-regulated activation of cell-adhesive RGD peptide on implanted biomaterials regulates in vivo cell adhesion, inflammation, fibrous encapsulation, and vascularization of the material. This work shows that triggered in vivo presentation of bioligands can be harnessed to direct tissue reparative responses associated with implanted biomaterials.

Light-triggered in vivo activation of adhesive peptides regulates cell adhesion, inflammation and vascularization of biomaterials

NASA Astrophysics Data System (ADS)

Lee, Ted T.; García, José R.; Paez, Julieta I.; Singh, Ankur; Phelps, Edward A.; Weis, Simone; Shafiq, Zahid; Shekaran, Asha; Del Campo, Aránzazu; García, Andrés J.

2015-03-01

Materials engineered to elicit targeted cellular responses in regenerative medicine must display bioligands with precise spatial and temporal control. Although materials with temporally regulated presentation of bioadhesive ligands using external triggers, such as light and electric fields, have recently been realized for cells in culture, the impact of in vivo temporal ligand presentation on cell-material responses is unknown. Here, we present a general strategy to temporally and spatially control the in vivo presentation of bioligands using cell-adhesive peptides with a protecting group that can be easily removed via transdermal light exposure to render the peptide fully active. We demonstrate that non-invasive, transdermal time-regulated activation of cell-adhesive RGD peptide on implanted biomaterials regulates in vivo cell adhesion, inflammation, fibrous encapsulation, and vascularization of the material. This work shows that triggered in vivo presentation of bioligands can be harnessed to direct tissue reparative responses associated with implanted biomaterials.

A circuit-based mechanism underlying familiarity signaling and the preference for novelty

PubMed Central

Molas, Susanna; Zhao-Shea, Rubing; Liu, Liwang; DeGroot, Steven R.; Gardner, Paul D.; Tapper, Andrew R.

2017-01-01

Novelty preference (NP) is an evolutionarily conserved, essential survival mechanism often dysregulated in neuropsychiatric disorders. NP is mediated by a motivational dopamine signal that increases in response to novel stimuli thereby driving exploration. However, the mechanism by which once novel stimuli transitions to familiar stimuli is unknown. Here we describe a neuroanatomical substrate for familiarity signaling, the interpeduncular nucleus (IPN) of the midbrain, which is activated as novel stimuli become familiar with multiple exposures. Optogenetic silencing of IPN neurons increases salience of and interaction with familiar stimuli without affecting novelty responses; whereas, photo-activation of the same neurons reduces exploration of novel stimuli mimicking familiarity. Bi-directional control of NP by the IPN depends on familiarity- and novelty-signals arising from excitatory habenula and dopaminergic ventral tegmental area inputs, which activate and reduce IPN activity, respectively. These results demonstrate that familiarity signals through unique IPN circuitry that opposes novelty seeking to control NP. PMID:28714952

Investigating Factors that Generate and Maintain Variation in Migratory Orientation: A Primer for Recent and Future Work.

PubMed

Delmore, Kira E; Liedvogel, Miriam

2016-01-01

The amazing accuracy of migratory orientation performance across the animal kingdom is facilitated by the use of magnetic and celestial compass systems that provide individuals with both directional and positional information. Quantitative genetics analyses in several animal systems suggests that migratory orientation has a strong genetic component. Nevertheless, the exact identity of genes controlling orientation remains largely unknown, making it difficult to obtain an accurate understanding of this fascinating behavior on the molecular level. Here, we provide an overview of molecular genetic techniques employed thus far, highlight the pros and cons of various approaches, generalize results from species-specific studies whenever possible, and evaluate how far the field has come since early quantitative genetics studies. We emphasize the importance of examining different levels of molecular control, and outline how future studies can take advantage of high-resolution tracking and sequencing techniques to characterize the genomic architecture of migratory orientation.

Coup-TF1 and Coup-TF2 control subtype and laminar identity of MGE-derived neocortical interneurons.

PubMed

Hu, Jia Sheng; Vogt, Daniel; Lindtner, Susan; Sandberg, Magnus; Silberberg, Shanni N; Rubenstein, John L R

2017-08-01

Distinct cortical interneuron (CIN) subtypes have unique circuit functions; dysfunction in specific subtypes is implicated in neuropsychiatric disorders. Somatostatin- and parvalbumin-expressing (SST + and PV + ) interneurons are the two major subtypes generated by medial ganglionic eminence (MGE) progenitors. Spatial and temporal mechanisms governing their cell-fate specification and differential integration into cortical layers are largely unknown. We provide evidence that Coup-TF1 and Coup-TF2 ( Nr2f1 and Nr2f2 ) transcription factor expression in an arc-shaped progenitor domain within the MGE promotes time-dependent survival of this neuroepithelium and the time-dependent specification of layer V SST + CINs. Coup-TF1 and Coup-TF2 autonomously repress PV + fate in MGE progenitors, in part through directly driving Sox6 expression. These results have identified, in mouse, a transcriptional pathway that controls SST-PV fate. © 2017. Published by The Company of Biologists Ltd.

Targeted Metabolomics Approach To Detect the Misuse of Steroidal Aromatase Inhibitors in Equine Sports by Biomarker Profiling.

PubMed

Chan, George Ho Man; Ho, Emmie Ngai Man; Leung, David Kwan Kon; Wong, Kin Sing; Wan, Terence See Ming

2016-01-05

The use of anabolic androgenic steroids (AAS) is prohibited in both human and equine sports. The conventional approach in doping control testing for AAS (as well as other prohibited substances) is accomplished by the direct detection of target AAS or their characteristic metabolites in biological samples using hyphenated techniques such as gas chromatography or liquid chromatography coupled with mass spectrometry. Such an approach, however, falls short when dealing with unknown designer steroids where reference materials and their pharmacokinetics are not available. In addition, AASs with fast elimination times render the direct detection approach ineffective as the detection window is short. A targeted metabolomics approach is a plausible alternative to the conventional direct detection approach for controlling the misuse of AAS in sports. Because the administration of AAS of the same class may trigger similar physiological responses or effects in the body, it may be possible to detect such administrations by monitoring changes in the endogenous steroidal expression profile. This study attempts to evaluate the viability of using the targeted metabolomics approach to detect the administration of steroidal aromatase inhibitors, namely androst-4-ene-3,6,17-trione (6-OXO) and androsta-1,4,6-triene-3,17-dione (ATD), in horses. Total (free and conjugated) urinary concentrations of 31 endogenous steroids were determined by gas chromatography-tandem mass spectrometry for a group of 2 resting and 2 in-training thoroughbred geldings treated with either 6-OXO or ATD. Similar data were also obtained from a control (untreated) group of in-training thoroughbred geldings (n = 28). Statistical processing and chemometric procedures using principle component analysis and orthogonal projection to latent structures-discriminant analysis (OPLS-DA) have highlighted 7 potential biomarkers that could be used to differentiate urine samples obtained from the control and the treated groups. On the basis of this targeted metabolomic approach, the administration of 6-OXO and ATD could be detected for much longer relative to that of the conventional direct detection approach.

11. Photocopy of photograph. Photographer unknown, circa 1955. Original photograph ...

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

11. Photocopy of photograph. Photographer unknown, circa 1955. Original photograph can be found in Marvine Colliery folder in the archives of the Lackawanna Historical Society, Scranton, Pennsylvania. VIEW SHOWING EAST AND NORTH FACADES OF BREAKER, WITH BOILER HOUSE AT FAR LEFT AND RETAIL SCALES OFFICE DIRECTLY EAST OF BREAKER, LOOKING SOUTHWEST - Marvine Colliery, Breaker No. 2, West side Boulevard Avenue, between East Parker Street & Route 380, Scranton, Lackawanna County, PA

Rapid screening and identification of chemical hazards in surface and drinking water using high resolution mass spectrometry and a case-control filter.

PubMed

Kaserzon, Sarit L; Heffernan, Amy L; Thompson, Kristie; Mueller, Jochen F; Gomez Ramos, Maria Jose

2017-09-01

Access to clean, safe drinking water poses a serious challenge to regulators, and requires analytical strategies capable of rapid screening and identification of potentially hazardous chemicals, specifically in situations when threats to water quality or security require rapid investigations and potential response. This study describes a fast and efficient chemical hazard screening strategy for characterising trace levels of polar organic contaminants in water matrices, based on liquid chromatography high resolution mass spectrometry with post-acquisition 'case-control' data processing. This method allowed for a rapid response time of less than 24 h for the screening of target, suspect and non-target unknown chemicals via direct injection analysis, and a second, more sensitive analysis option requiring sample pre-concentration. The method was validated by fortifying samples with a range of pesticides, pharmaceuticals and personal care products (n = 46); with >90% of target compounds positively screened in samples at 1 ng mL -1 , and 46% at 0.1 ng mL -1 when analysed via direct injection. To simulate a contamination event samples were fortified with compounds not present in the commercial library (designated 'non-target compounds'; fipronil and fenitrothion), tentatively identified at 0.2 and 1 ng mL -1 , respectively; and a compound not included in any known commercial library or public database (designated 'unknown' compounds; 8Cl - perfluorooctanesulfonic acid), at 0.8 ng mL -1 . The method was applied to two 'real-case' scenarios: (1) the assessment of drinking water safety during a high-profile event in Brisbane, Australia; and (2) to screen treated, re-circulated drinking water and pre-treated (raw) water. The validated workflow was effective for rapid prioritisation and screening of suspect and non-target potential hazards at trace levels, and could be applied to a wide range of matrices and investigations where comparison of organic contaminants between an affected and control site and or timeframe is warranted. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adaptive Robust Output Feedback Control for a Marine Dynamic Positioning System Based on a High-Gain Observer.

PubMed

Du, Jialu; Hu, Xin; Liu, Hongbo; Chen, C L Philip

2015-11-01

This paper develops an adaptive robust output feedback control scheme for dynamically positioned ships with unavailable velocities and unknown dynamic parameters in an unknown time-variant disturbance environment. The controller is designed by incorporating the high-gain observer and radial basis function (RBF) neural networks in vectorial backstepping method. The high-gain observer provides the estimations of the ship position and heading as well as velocities. The RBF neural networks are employed to compensate for the uncertainties of ship dynamics. The adaptive laws incorporating a leakage term are designed to estimate the weights of RBF neural networks and the bounds of unknown time-variant environmental disturbances. In contrast to the existing results of dynamic positioning (DP) controllers, the proposed control scheme relies only on the ship position and heading measurements and does not require a priori knowledge of the ship dynamics and external disturbances. By means of Lyapunov functions, it is theoretically proved that our output feedback controller can control a ship's position and heading to the arbitrarily small neighborhood of the desired target values while guaranteeing that all signals in the closed-loop DP control system are uniformly ultimately bounded. Finally, simulations involving two ships are carried out, and simulation results demonstrate the effectiveness of the proposed control scheme.

Orphan Nuclear Receptor ERRα Controls Macrophage Metabolic Signaling and A20 Expression to Negatively Regulate TLR-Induced Inflammation.

PubMed

Yuk, Jae-Min; Kim, Tae Sung; Kim, Soo Yeon; Lee, Hye-Mi; Han, Jeongsu; Dufour, Catherine Rosa; Kim, Jin Kyung; Jin, Hyo Sun; Yang, Chul-Su; Park, Ki-Sun; Lee, Chul-Ho; Kim, Jin-Man; Kweon, Gi Ryang; Choi, Hueng-Sik; Vanacker, Jean-Marc; Moore, David D; Giguère, Vincent; Jo, Eun-Kyeong

2015-07-21

The orphan nuclear receptor estrogen-related receptor α (ERRα; NR3B1) is a key metabolic regulator, but its function in regulating inflammation remains largely unknown. Here, we demonstrate that ERRα negatively regulates Toll-like receptor (TLR)-induced inflammation by promoting Tnfaip3 transcription and fine-tuning of metabolic reprogramming in macrophages. ERRα-deficient (Esrra(-/-)) mice showed increased susceptibility to endotoxin-induced septic shock, leading to more severe pro-inflammatory responses than control mice. ERRα regulated macrophage inflammatory responses by directly binding the promoter region of Tnfaip3, a deubiquitinating enzyme in TLR signaling. In addition, Esrra(-/-) macrophages showed an increased glycolysis, but impaired mitochondrial respiratory function and biogenesis. Further, ERRα was required for the regulation of NF-κB signaling by controlling p65 acetylation via maintenance of NAD(+) levels and sirtuin 1 activation. These findings unravel a previously unappreciated role for ERRα as a negative regulator of TLR-induced inflammatory responses through inducing Tnfaip3 transcription and controlling the metabolic reprogramming. Copyright © 2015 Elsevier Inc. All rights reserved.

Hunger States Control the Directions of Synaptic Plasticity via Switching Cell Type-Specific Subunits of NMDA Receptors.

PubMed

Qi, Yong; Yang, Yunlei

2015-09-23

It remains largely unknown whether and how hunger states control activity-dependent synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD). We here report that both LTP and LTD of excitatory synaptic strength within the appetite control circuits residing in hypothalamic arcuate nucleus (ARC) behave in a manner of hunger states dependence and cell type specificity. For instance, we find that tetanic stimulation induces LTP at orexigenic agouti-related protein (AgRP) neurons in ad libitum fed mice, whereas it induces LTD in food-deprived mice. In an opposite direction, the same induction protocol induces LTD at anorexigenic pro-opiomelanocortin (POMC) neurons in fed mice but weak LTP in deprived mice. Mechanistically, we also find that food deprivation increases the expressions of NR2C/NR2D/NR3-containing NMDA receptors (NMDARs) at AgRP neurons that contribute to the inductions of LTD, whereas it decreases their expressions at POMC neurons. Collectively, our data reveal that hunger states control the directions of activity-dependent synaptic plasticity by switching NMDA receptor subpopulations in a cell type-specific manner, providing insights into NMDAR-mediated interactions between energy states and associative memory. Significance statement: Based on the experiments performed in this study, we demonstrate that activity-dependent synaptic plasticity is also under the control of energy states by regulating NMDAR subpopulations in a cell type-specific manner. We thus propose a reversible memory configuration constructed from energy states-dependent cell type-specific bidirectional conversions of LTP and LTD. Together with the distinct functional roles played by NMDAR signaling in the control of food intake and energy states, these findings reveal a new reciprocal interaction between energy states and associative memory, one that might serve as a target for therapeutic treatments of the energy-related memory disorders or vice versa. Copyright © 2015 the authors 0270-6474/15/3513171-12$15.00/0.

Neural Networks for Flight Control

NASA Technical Reports Server (NTRS)

Jorgensen, Charles C.

1996-01-01

Neural networks are being developed at NASA Ames Research Center to permit real-time adaptive control of time varying nonlinear systems, enhance the fault-tolerance of mission hardware, and permit online system reconfiguration. In general, the problem of controlling time varying nonlinear systems with unknown structures has not been solved. Adaptive neural control techniques show considerable promise and are being applied to technical challenges including automated docking of spacecraft, dynamic balancing of the space station centrifuge, online reconfiguration of damaged aircraft, and reducing cost of new air and spacecraft designs. Our experiences have shown that neural network algorithms solved certain problems that conventional control methods have been unable to effectively address. These include damage mitigation in nonlinear reconfiguration flight control, early performance estimation of new aircraft designs, compensation for damaged planetary mission hardware by using redundant manipulator capability, and space sensor platform stabilization. This presentation explored these developments in the context of neural network control theory. The discussion began with an overview of why neural control has proven attractive for NASA application domains. The more important issues in control system development were then discussed with references to significant technical advances in the literature. Examples of how these methods have been applied were given, followed by projections of emerging application needs and directions.

The use of Peer Optic Nerve Photographs for Teaching Direct Ophthalmoscopy

PubMed Central

Milani, Behrad Y.; Majdi, Mercede N.; Green, Wesley; Mehralian, Amir; Moarefi, Majid; Oh, Freddie S.; Riddle, Janet M.; Djalilian, Ali R.

2014-01-01

Objective To use a novel teaching exercise to encourage students to practice ophthalmoscopy and to measure the learning effect both subjectively and objectively. Design Comparative case series. Participants One-hundred thirty-one fourth-year medical students on their one-week ophthalmology rotations with 89 in the experimental group and 42 in the control group. Methods Those in the experimental group had one eye dilated and their optic nerve photographed on the first day. The next day, these students received an unlabeled optic nerve photograph belonging to one of their peers (typically 8–10 per group) and were given three days to identify the student matching the photograph. The students in the control group were simply encouraged to practice ophthalmoscopy on each other without the use of photographs. Main Outcome Measures Both objective and subjective changes from the beginning to the end of the rotation were measured and compared between the two groups. Results In the 89 students who used peer optic nerve photographs, 75 (84.3%) showed improvement in direct ophthalmoscopy skills over the course of the week. In contrast, only 12 (28.6%) of the 42 control students demonstrated an objective improvement (P < 0.001). The subjective confidence levels were likewise more improved in the students who took part in the optic nerve photograph exercise. Conclusions These results suggest that the task of matching an unknown optic nerve photograph to the correct eye of a peer leads to increased self-confidence and more proficient use of the direct ophthalmoscope. PMID:23246117

A Temperature-Responsive Network Links Cell Shape and Virulence Traits in a Primary Fungal Pathogen

PubMed Central

Beyhan, Sinem; Gutierrez, Matias; Voorhies, Mark; Sil, Anita

2013-01-01

Survival at host temperature is a critical trait for pathogenic microbes of humans. Thermally dimorphic fungal pathogens, including Histoplasma capsulatum, are soil fungi that undergo dramatic changes in cell shape and virulence gene expression in response to host temperature. How these organisms link changes in temperature to both morphologic development and expression of virulence traits is unknown. Here we elucidate a temperature-responsive transcriptional network in H. capsulatum, which switches from a filamentous form in the environment to a pathogenic yeast form at body temperature. The circuit is driven by three highly conserved factors, Ryp1, Ryp2, and Ryp3, that are required for yeast-phase growth at 37°C. Ryp factors belong to distinct families of proteins that control developmental transitions in fungi: Ryp1 is a member of the WOPR family of transcription factors, and Ryp2 and Ryp3 are both members of the Velvet family of proteins whose molecular function is unknown. Here we provide the first evidence that these WOPR and Velvet proteins interact, and that Velvet proteins associate with DNA to drive gene expression. Using genome-wide chromatin immunoprecipitation studies, we determine that Ryp1, Ryp2, and Ryp3 associate with a large common set of genomic loci that includes known virulence genes, indicating that the Ryp factors directly control genes required for pathogenicity in addition to their role in regulating cell morphology. We further dissect the Ryp regulatory circuit by determining that a fourth transcription factor, which we name Ryp4, is required for yeast-phase growth and gene expression, associates with DNA, and displays interdependent regulation with Ryp1, Ryp2, and Ryp3. Finally, we define cis-acting motifs that recruit the Ryp factors to their interwoven network of temperature-responsive target genes. Taken together, our results reveal a positive feedback circuit that directs a broad transcriptional switch between environmental and pathogenic states in response to temperature. PMID:23935449

Alcoholic neuropathy

MedlinePlus

Neuropathy - alcoholic; Alcoholic polyneuropathy ... The exact cause of alcoholic neuropathy is unknown. It likely includes both a direct poisoning of the nerve by the alcohol and the effect of poor nutrition ...

Proteins of unknown function in the Protein Data Bank (PDB): an inventory of true uncharacterized proteins and computational tools for their analysis.

PubMed

Nadzirin, Nurul; Firdaus-Raih, Mohd

2012-10-08

Proteins of uncharacterized functions form a large part of many of the currently available biological databases and this situation exists even in the Protein Data Bank (PDB). Our analysis of recent PDB data revealed that only 42.53% of PDB entries (1084 coordinate files) that were categorized under "unknown function" are true examples of proteins of unknown function at this point in time. The remainder 1465 entries also annotated as such appear to be able to have their annotations re-assessed, based on the availability of direct functional characterization experiments for the protein itself, or for homologous sequences or structures thus enabling computational function inference.

On synchronisation of a class of complex chaotic systems with complex unknown parameters via integral sliding mode control

NASA Astrophysics Data System (ADS)

Tirandaz, Hamed; Karami-Mollaee, Ali

2018-06-01

Chaotic systems demonstrate complex behaviour in their state variables and their parameters, which generate some challenges and consequences. This paper presents a new synchronisation scheme based on integral sliding mode control (ISMC) method on a class of complex chaotic systems with complex unknown parameters. Synchronisation between corresponding states of a class of complex chaotic systems and also convergence of the errors of the system parameters to zero point are studied. The designed feedback control vector and complex unknown parameter vector are analytically achieved based on the Lyapunov stability theory. Moreover, the effectiveness of the proposed methodology is verified by synchronisation of the Chen complex system and the Lorenz complex systems as the leader and the follower chaotic systems, respectively. In conclusion, some numerical simulations related to the synchronisation methodology is given to illustrate the effectiveness of the theoretical discussions.

Implementation of controlled quantum teleportation with an arbitrator for secure quantum channels via quantum dots inside optical cavities.

PubMed

Heo, Jino; Hong, Chang-Ho; Kang, Min-Sung; Yang, Hyeon; Yang, Hyung-Jin; Hong, Jong-Phil; Choi, Seong-Gon

2017-11-02

We propose a controlled quantum teleportation scheme to teleport an unknown state based on the interactions between flying photons and quantum dots (QDs) confined within single- and double-sided cavities. In our scheme, users (Alice and Bob) can teleport the unknown state through a secure entanglement channel under the control and distribution of an arbitrator (Trent). For construction of the entanglement channel, Trent utilizes the interactions between two photons and the QD-cavity system, which consists of a charged QD (negatively charged exciton) inside a single-sided cavity. Subsequently, Alice can teleport the unknown state of the electron spin in a QD inside a double-sided cavity to Bob's electron spin in a QD inside a single-sided cavity assisted by the channel information from Trent. Furthermore, our scheme using QD-cavity systems is feasible with high fidelity, and can be experimentally realized with current technologies.

General Anisotropy Identification of Paperboard with Virtual Fields Method

Treesearch

J.M. Considine; F. Pierron; K.T. Turner; D.W. Vahey

2014-01-01

This work extends previous efforts in plate bending of Virtual Fields Method (VFM) parameter identification to include a general 2-D anisotropicmaterial. Such an extension was needed for instances in which material principal directions are unknown or when specimen orientation is not aligned with material principal directions. A new fixture with a multiaxial force...

Adaptive Actor-Critic Design-Based Integral Sliding-Mode Control for Partially Unknown Nonlinear Systems With Input Disturbances.

PubMed

Fan, Quan-Yong; Yang, Guang-Hong

2016-01-01

This paper is concerned with the problem of integral sliding-mode control for a class of nonlinear systems with input disturbances and unknown nonlinear terms through the adaptive actor-critic (AC) control method. The main objective is to design a sliding-mode control methodology based on the adaptive dynamic programming (ADP) method, so that the closed-loop system with time-varying disturbances is stable and the nearly optimal performance of the sliding-mode dynamics can be guaranteed. In the first step, a neural network (NN)-based observer and a disturbance observer are designed to approximate the unknown nonlinear terms and estimate the input disturbances, respectively. Based on the NN approximations and disturbance estimations, the discontinuous part of the sliding-mode control is constructed to eliminate the effect of the disturbances and attain the expected equivalent sliding-mode dynamics. Then, the ADP method with AC structure is presented to learn the optimal control for the sliding-mode dynamics online. Reconstructed tuning laws are developed to guarantee the stability of the sliding-mode dynamics and the convergence of the weights of critic and actor NNs. Finally, the simulation results are presented to illustrate the effectiveness of the proposed method.

A Reduced-Order Successive Linear Estimator for Geostatistical Inversion and its Application in Hydraulic Tomography

NASA Astrophysics Data System (ADS)

Zha, Yuanyuan; Yeh, Tian-Chyi J.; Illman, Walter A.; Zeng, Wenzhi; Zhang, Yonggen; Sun, Fangqiang; Shi, Liangsheng

2018-03-01

Hydraulic tomography (HT) is a recently developed technology for characterizing high-resolution, site-specific heterogeneity using hydraulic data (nd) from a series of cross-hole pumping tests. To properly account for the subsurface heterogeneity and to flexibly incorporate additional information, geostatistical inverse models, which permit a large number of spatially correlated unknowns (ny), are frequently used to interpret the collected data. However, the memory storage requirements for the covariance of the unknowns (ny × ny) in these models are prodigious for large-scale 3-D problems. Moreover, the sensitivity evaluation is often computationally intensive using traditional difference method (ny forward runs). Although employment of the adjoint method can reduce the cost to nd forward runs, the adjoint model requires intrusive coding effort. In order to resolve these issues, this paper presents a Reduced-Order Successive Linear Estimator (ROSLE) for analyzing HT data. This new estimator approximates the covariance of the unknowns using Karhunen-Loeve Expansion (KLE) truncated to nkl order, and it calculates the directional sensitivities (in the directions of nkl eigenvectors) to form the covariance and cross-covariance used in the Successive Linear Estimator (SLE). In addition, the covariance of unknowns is updated every iteration by updating the eigenvalues and eigenfunctions. The computational advantages of the proposed algorithm are demonstrated through numerical experiments and a 3-D transient HT analysis of data from a highly heterogeneous field site.

Metagenomic ventures into outer sequence space.

PubMed

Dutilh, Bas E

Sequencing DNA or RNA directly from the environment often results in many sequencing reads that have no homologs in the database. These are referred to as "unknowns," and reflect the vast unexplored microbial sequence space of our biosphere, also known as "biological dark matter." However, unknowns also exist because metagenomic datasets are not optimally mined. There is a pressure on researchers to publish and move on, and the unknown sequences are often left for what they are, and conclusions drawn based on reads with annotated homologs. This can cause abundant and widespread genomes to be overlooked, such as the recently discovered human gut bacteriophage crAssphage. The unknowns may be enriched for bacteriophage sequences, the most abundant and genetically diverse component of the biosphere and of sequence space. However, it remains an open question, what is the actual size of biological sequence space? The de novo assembly of shotgun metagenomes is the most powerful tool to address this question.

Direct brain recordings reveal impaired neural function in infants with single-suture craniosynostosis: a future modality for guiding management?

PubMed

Hashim, Peter W; Brooks, Eric D; Persing, John A; Reuman, Hannah; Naples, Adam; Travieso, Roberto; Terner, Jordan; Steinbacher, Derek; Landi, Nicole; Mayes, Linda; McPartland, James C

2015-01-01

Patients with single-suture craniosynostosis (SSC) are at an elevated risk for long-term learning disabilities. Such adverse outcomes indicate that the early development of neural processing in SSC may be abnormal. At present, however, the precise functional derangements of the developing brain remain largely unknown. Event-related potentials (ERPs) are a form of noninvasive neuroimaging that provide direct measurements of cortical activity and have shown value in predicting long-term cognitive functioning. The current study used ERPs to examine auditory processing in infants with SSC to help clarify the developmental onset of delays in this population. Fifteen infants with untreated SSC and 23 typically developing controls were evaluated. ERPs were recorded during the presentation of speech sounds. Analyses focused on the P150 and N450 components of auditory processing. Infants with SSC demonstrated attenuated P150 amplitudes relative to typically developing controls. No differences in the N450 component were identified between untreated SSC and controls. Infants with untreated SSC demonstrate abnormal speech sound processing. Atypicalities are detectable as early as 6 months of age and may represent precursors to long-term language delay. Electrophysiological assessments provide a precise examination of neural processing in SSC and hold potential as a future modality to examine the effects of surgical treatment on brain development.

Do neotropical migrant butterflies navigate using a solar compass?

PubMed

Oliveira; Srygley; Dudley

1998-12-01

Many tropical butterfly species are well-known for their migratory behaviour. Although these insects can maintain a constant direction throughout the day, the physiological mechanisms of orientation are unknown. It has been argued that tropical migrant butterflies must use a time-compensated sun compass to accomplish their journey, but the crucial experimental manipulations to test this hypothesis have not been conducted. This study reports the results of clock-shift experiments performed with two species of migrating butterflies (Pieridae: Aphrissa statira and Phoebis argante) captured during flight across Lake Gatun, Panama. The observed constant flight bearing of natural controls suggests that these species are capable of performing time-compensated celestial navigation. Our clock-shift experiments suggest that a sun compass is involved. Individuals submitted to a 4 h advance shift took significantly different mean orientations on release compared with control butterflies. The direction of this difference was consistent with the use of a sun compass. The magnitude was approximately half the predicted value if the vanishing bearing of released butterflies was used as the variable to evaluate the effect of time-shifting and approximately three-quarters of that predicted if the estimated heading was the variable used. Mean vanishing bearings of control and experimental butterflies did not correspond to predicted values. This difference can be attributed largely to the combined effects of wind and handling.

Social stress induces changes in urinary bladder function, bladder NGF content, and generalized bladder inflammation in mice

PubMed Central

Peterson, Abbey; Erickson, Cuixia Shi; Nelson, Mark T.; Vizzard, Margaret A.

2014-01-01

Social stress may play a role in urinary bladder dysfunction in humans, but the underlying mechanisms are unknown. In the present study, we explored changes in bladder function caused by social stress using mouse models of stress and increasing stress. In the stress paradigm, individual submissive FVB mice were exposed to C57BL/6 aggressor mice directly/indirectly for 1 h/day for 2 or 4 wk. Increased stress was induced by continuous, direct/indirect exposure of FVB mice to aggressor mice for 2 wk. Stressed FVB mice exhibited nonvoiding bladder contractions and a decrease in both micturition interval (increased voiding frequency) and bladder capacity compared with control animals. ELISAs demonstrated a significant increase in histamine protein expression with no change in nerve growth factor protein expression in the urinary bladder compared with controls. Unlike stressed mice, mice exposed to an increased stress paradigm exhibited increased bladder capacities and intermicturition intervals (decreased voiding frequency). Both histamine and nerve growth factor protein expression were significantly increased with increased stress compared with control bladders. The change in bladder function from increased voiding frequency to decreased voiding frequency with increased stress intensity suggests that changes in social stress-induced urinary bladder dysfunction are context and duration dependent. In addition, changes in the bladder inflammatory milieu with social stress may be important contributors to changes in urinary bladder function. PMID:25100077

A parieto-medial temporal pathway for the strategic control over working memory biases in human visual attention.

PubMed

Soto, David; Greene, Ciara M; Kiyonaga, Anastasia; Rosenthal, Clive R; Egner, Tobias

2012-12-05

The contents of working memory (WM) can both aid and disrupt the goal-directed allocation of visual attention. WM benefits attention when its contents overlap with goal-relevant stimulus features, but WM leads attention astray when its contents match features of currently irrelevant stimuli. Recent behavioral data have documented that WM biases of attention may be subject to strategic cognitive control processes whereby subjects are able to either enhance or inhibit the influence of WM contents on attention. However, the neural mechanisms supporting cognitive control over WM biases on attention are presently unknown. Here, we characterize these mechanisms by combining human functional magnetic resonance imaging with a task that independently manipulates the relationship between WM cues and attention targets during visual search (with WM contents matching either search targets or distracters), as well as the predictability of this relationship (100 vs 50% predictability) to assess participants' ability to strategically enhance or inhibit WM biases on attention when WM contents reliably matched targets or distracter stimuli, respectively. We show that cues signaling predictable (> unpredictable) WM-attention relations reliably enhanced search performance, and that this strategic modulation of the interplay between WM contents and visual attention was mediated by a neuroanatomical network involving the posterior parietal cortex, the posterior cingulate, and medial temporal lobe structures, with responses in the hippocampus proper correlating with behavioral measures of strategic control of WM biases. Thus, we delineate a novel parieto-medial temporal pathway implementing cognitive control over WM biases to optimize goal-directed selection.

Nanomorphology Effects in Semiconductors with Native Ferromagnetism: Hierarchical Europium (II) Oxide Tubes Prepared via a Topotactic Nanostructure Transition.

PubMed

Trepka, Bastian; Erler, Philipp; Selzer, Severin; Kollek, Tom; Boldt, Klaus; Fonin, Mikhail; Nowak, Ulrich; Wolf, Daniel; Lubk, Axel; Polarz, Sebastian

2018-01-01

Semiconductors with native ferromagnetism barely exist and defined nanostructures are almost unknown. This lack impedes the exploration of a new class of materials characterized by a direct combination of effects on the electronic system caused by quantum confinement effects with magnetism. A good example is EuO for which currently no reliable routes for nanoparticle synthesis can be established. Bottom-up approaches applicable to other oxides fail because of the labile oxidation state +II. Instead of targeting a direct synthesis, the two steps-"structure control" and "chemical transformation"-are separated. The generation of a transitional, hybrid nanophase is followed by its conversion into EuO under full conservation of all morphological features. Hierarchical EuO materials are now accessible in the shape of oriented nanodisks stacked to tubular particles. Magnetically, the coupling of either vortex or onion states has been found. An unexpected temperature dependence is governed by thermally activated transitions between these states. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantification of nanowire penetration into living cells

NASA Astrophysics Data System (ADS)

Xu, Alexander M.; Aalipour, Amin; Leal-Ortiz, Sergio; Mekhdjian, Armen H.; Xie, Xi; Dunn, Alexander R.; Garner, Craig C.; Melosh, Nicholas A.

2014-04-01

High-aspect ratio nanostructures such as nanowires and nanotubes are a powerful new tool for accessing the cell interior for delivery and sensing. Controlling and optimizing cellular access is a critical challenge for this new technology, yet even the most basic aspect of this process, whether these structures directly penetrate the cell membrane, is still unknown. Here we report the first quantification of hollow nanowires—nanostraws—that directly penetrate the membrane by observing dynamic ion delivery from each 100-nm diameter nanostraw. We discover that penetration is a rare event: 7.1±2.7% of the nanostraws penetrate the cell to provide cytosolic access for an extended period for an average of 10.7±5.8 penetrations per cell. Using time-resolved delivery, the kinetics of the first penetration event are shown to be adhesion dependent and coincident with recruitment of focal adhesion-associated proteins. These measurements provide a quantitative basis for understanding nanowire-cell interactions, and a means for rapidly assessing membrane penetration.

A hypothalamic circuit for the circadian control of aggression.

PubMed

Todd, William D; Fenselau, Henning; Wang, Joshua L; Zhang, Rong; Machado, Natalia L; Venner, Anne; Broadhurst, Rebecca Y; Kaur, Satvinder; Lynagh, Timothy; Olson, David P; Lowell, Bradford B; Fuller, Patrick M; Saper, Clifford B

2018-05-01

'Sundowning' in dementia and Alzheimer's disease is characterized by early-evening agitation and aggression. While such periodicity suggests a circadian origin, whether the circadian clock directly regulates aggressive behavior is unknown. We demonstrate that a daily rhythm in aggression propensity in male mice is gated by GABAergic subparaventricular zone (SPZ GABA ) neurons, the major postsynaptic targets of the central circadian clock, the suprachiasmatic nucleus. Optogenetic mapping revealed that SPZ GABA neurons receive input from vasoactive intestinal polypeptide suprachiasmatic nucleus neurons and innervate neurons in the ventrolateral part of the ventromedial hypothalamus (VMH), which is known to regulate aggression. Additionally, VMH-projecting dorsal SPZ neurons are more active during early day than early night, and acute chemogenetic inhibition of SPZ GABA transmission phase-dependently increases aggression. Finally, SPZ GABA -recipient central VMH neurons directly innervate ventrolateral VMH neurons, and activation of this intra-VMH circuit drove attack behavior. Altogether, we reveal a functional polysynaptic circuit by which the suprachiasmatic nucleus clock regulates aggression.

A 61-million-person experiment in social influence and political mobilization

PubMed Central

Bond, Robert M.; Fariss, Christopher J.; Jones, Jason J.; Kramer, Adam D. I.; Marlow, Cameron; Settle, Jaime E.; Fowler, James H.

2013-01-01

Human behaviour is thought to spread through face-to-face social networks, but it is difficult to identify social influence effects in observational studies9–13, and it is unknown whether online social networks operate in the same way14–19. Here we report results from a randomized controlled trial of political mobilization messages delivered to 61 million Facebook users during the 2010 US congressional elections. The results show that the messages directly influenced political self-expression, information seeking and real-world voting behaviour of millions of people. Furthermore, the messages not only influenced the users who received them but also the users’ friends, and friends of friends. The effect of social transmission on real-world voting was greater than the direct effect of the messages themselves, and nearly all the transmission occurred between ‘close friends’ who were more likely to have a face-to-face relationship. These results suggest that strong ties are instrumental for spreading both online and real-world behaviour in human social networks. PMID:22972300

Genomic identification of direct target genes of LEAFY

PubMed Central

William, Dilusha A.; Su, Yanhui; Smith, Michael R.; Lu, Meina; Baldwin, Don A.; Wagner, Doris

2004-01-01

The switch from vegetative to reproductive development in plants necessitates a switch in the developmental program of the descendents of the stem cells in the shoot apical meristem. Genetic and molecular investigations have demonstrated that the plant-specific transcription factor and meristem identity regulator LEAFY (LFY) controls this developmental transition by inducing expression of a second transcription factor, APETALA1, and by regulating the expression of additional, as yet unknown, genes. Here we show that the additional LFY targets include the APETALA1-related factor, CAULI-FLOWER, as well as three transcription factors and two putative signal transduction pathway components. These genes are up-regulated by LFY even when protein synthesis is inhibited and, hence, appear to be direct targets of LFY. Supporting this conclusion, cis-regulatory regions upstream of these genes are bound by LFY in vivo. The newly identified LFY targets likely initiate the transcriptional changes that are required for the switch from vegetative to reproductive development in Arabidopsis. PMID:14736918

The BCL11A Transcription Factor Directly Activates RAG Gene Expression and V(D)J Recombination

PubMed Central

Lee, Baeck-seung; Dekker, Joseph D.; Lee, Bum-kyu; Iyer, Vishwanath R.; Sleckman, Barry P.; Shaffer, Arthur L.; Ippolito, Gregory C.

2013-01-01

Recombination-activating gene 1 protein (RAG1) and RAG2 are critical enzymes for initiating variable-diversity-joining (VDJ) segment recombination, an essential process for antigen receptor expression and lymphocyte development. The transcription factor BCL11A is required for B cell development, but its molecular function(s) in B cell fate specification and commitment is unknown. We show here that the major B cell isoform, BCL11A-XL, binds the RAG1 promoter and Erag enhancer to activate RAG1 and RAG2 transcription in pre-B cells. We employed BCL11A overexpression with recombination substrates in a cultured pre-B cell line as well as Cre recombinase-mediated Bcl11alox/lox deletion in explanted murine pre-B cells to demonstrate direct consequences of BCL11A/RAG modulation on V(D)J recombination. We conclude that BCL11A is a critical component of a transcriptional network that regulates B cell fate by controlling V(D)J recombination. PMID:23438597

Interlayer orientation-dependent light absorption and emission in monolayer semiconductor stacks

PubMed Central

Heo, Hoseok; Sung, Ji Ho; Cha, Soonyoung; Jang, Bo-Gyu; Kim, Joo-Youn; Jin, Gangtae; Lee, Donghun; Ahn, Ji-Hoon; Lee, Myoung-Jae; Shim, Ji Hoon; Choi, Hyunyong; Jo, Moon-Ho

2015-01-01

Two-dimensional stacks of dissimilar hexagonal monolayers exhibit unusual electronic, photonic and photovoltaic responses that arise from substantial interlayer excitations. Interband excitation phenomena in individual hexagonal monolayer occur in states at band edges (valleys) in the hexagonal momentum space; therefore, low-energy interlayer excitation in the hexagonal monolayer stacks can be directed by the two-dimensional rotational degree of each monolayer crystal. However, this rotation-dependent excitation is largely unknown, due to lack in control over the relative monolayer rotations, thereby leading to momentum-mismatched interlayer excitations. Here, we report that light absorption and emission in MoS2/WS2 monolayer stacks can be tunable from indirect- to direct-gap transitions in both spectral and dynamic characteristics, when the constituent monolayer crystals are coherently stacked without in-plane rotation misfit. Our study suggests that the interlayer rotational attributes determine tunable interlayer excitation as a new set of basis for investigating optical phenomena in a two-dimensional hexagonal monolayer system. PMID:26099952

Shared motion signals for human perceptual decisions and oculomotor actions

NASA Technical Reports Server (NTRS)

Stone, Leland S.; Krauzlis, Richard J.

2003-01-01

A fundamental question in primate neurobiology is to understand to what extent motor behaviors are driven by shared neural signals that also support conscious perception or by independent subconscious neural signals dedicated to motor control. Although it has clearly been established that cortical areas involved in processing visual motion support both perception and smooth pursuit eye movements, it remains unknown whether the same or different sets of neurons within these structures perform these two functions. Examination of the trial-by-trial variation in human perceptual and pursuit responses during a simultaneous psychophysical and oculomotor task reveals that the direction signals for pursuit and perception are not only similar on average but also co-vary on a trial-by-trial basis, even when performance is at or near chance and the decisions are determined largely by neural noise. We conclude that the neural signal encoding the direction of target motion that drives steady-state pursuit and supports concurrent perceptual judgments emanates from a shared ensemble of cortical neurons.

Electromagnetic spectrum management system

DOEpatents

Seastrand, Douglas R.

2017-01-31

A system for transmitting a wireless countermeasure signal to disrupt third party communications is disclosed that include an antenna configured to receive wireless signals and transmit wireless counter measure signals such that the wireless countermeasure signals are responsive to the received wireless signals. A receiver processes the received wireless signals to create processed received signal data while a spectrum control module subtracts known source signal data from the processed received signal data to generate unknown source signal data. The unknown source signal data is based on unknown wireless signals, such as enemy signals. A transmitter is configured to process the unknown source signal data to create countermeasure signals and transmit a wireless countermeasure signal over the first antenna or a second antenna to thereby interfere with the unknown wireless signals.

Cerebral arteriovenous malformation

MedlinePlus

AVM - cerebral; Arteriovenous hemangioma; Stroke - AVM; Hemorrhagic stroke - AVM ... The cause of cerebral AVM is unknown. An AVM occurs when arteries in the brain connect directly to nearby veins without having the ...

Intrinsic aerobic capacity correlates with greater inherent mitochondrial oxidative and H2O2 emission capacities without major shifts in myosin heavy chain isoform.

PubMed

Seifert, Erin L; Bastianelli, Mark; Aguer, Céline; Moffat, Cynthia; Estey, Carmen; Koch, Lauren G; Britton, Steven L; Harper, Mary-Ellen

2012-11-01

Exercise capacity and performance strongly associate with metabolic and biophysical characteristics of skeletal muscle, factors that also relate to overall disease risk. Despite its importance, the exact mechanistic features that connect aerobic metabolism with health status are unknown. To explore this, we applied artificial selection of rats for intrinsic (i.e., untrained) aerobic treadmill running to generate strains of low- and high-capacity runners (LCR and HCR, respectively), subsequently shown to diverge for disease risk. Concurrent breeding of LCR and HCR per generation allows the lines to serve as reciprocal controls for unknown environmental changes. Here we provide the first direct evidence in mitochondria isolated from skeletal muscle that intrinsic mitochondrial capacity is higher in HCR rats. Maximal phosphorylating respiration was ~40% greater in HCR mitochondria, independent of substrate and without altered proton leak or major changes in protein levels or muscle fiber type, consistent with altered control of phosphorylating respiration. Unexpectedly, H(2)O(2) emission was ~20% higher in HCR mitochondria, due to greater reduction of more harmful reactive oxygen species to H(2)O(2); indeed, oxidative modification of mitochondrial proteins was lower. When the higher mitochondrial yield was considered, phosphorylating respiration and H(2)O(2) emission were 70-80% greater in HCR muscle. Greater capacity of HCR muscle for work and H(2)O(2) signaling may result in enhanced and more immediate cellular repair, possibly explaining lowered disease risks.

Pathogen survival trajectories: an eco-environmental approach to the modeling of human campylobacteriosis ecology.

PubMed Central

Skelly, Chris; Weinstein, Phil

2003-01-01

Campylobacteriosis, like many human diseases, has its own ecology in which the propagation of human infection and disease depends on pathogen survival and finding new hosts in order to replicate and sustain the pathogen population. The complexity of this process, a process common to other enteric pathogens, has hampered control efforts. Many unknowns remain, resulting in a poorly understood disease ecology. To provide structure to these unknowns and help direct further research and intervention, we propose an eco-environmental modeling approach for campylobacteriosis. This modeling approach follows the pathogen population as it moves through the environments that define the physical structure of its ecology. In this paper, we term the ecologic processes and environments through which these populations move "pathogen survival trajectories." Although such a modeling approach could have veterinary applications, our emphasis is on human campylobacteriosis and focuses on human exposures to Campylobacter through feces, food, and aquatic environments. The pathogen survival trajectories that lead to human exposure include ecologic filters that limit population size, e.g., cooking food to kill Campylobacter. Environmental factors that influence the size of the pathogen reservoirs include temperature, nutrient availability, and moisture availability during the period of time the pathogen population is moving through the environment between infected and susceptible hosts. We anticipate that the modeling approach proposed here will work symbiotically with traditional epidemiologic and microbiologic research to help guide and evaluate the acquisition of new knowledge about the ecology, eventual intervention, and control of campylobacteriosis. PMID:12515674

Study on the mapping of dark matter clustering from real space to redshift space

NASA Astrophysics Data System (ADS)

Zheng, Yi; Song, Yong-Seon

2016-08-01

The mapping of dark matter clustering from real space to redshift space introduces the anisotropic property to the measured density power spectrum in redshift space, known as the redshift space distortion effect. The mapping formula is intrinsically non-linear, which is complicated by the higher order polynomials due to indefinite cross correlations between the density and velocity fields, and the Finger-of-God effect due to the randomness of the peculiar velocity field. Whilst the full higher order polynomials remain unknown, the other systematics can be controlled consistently within the same order truncation in the expansion of the mapping formula, as shown in this paper. The systematic due to the unknown non-linear density and velocity fields is removed by separately measuring all terms in the expansion directly using simulations. The uncertainty caused by the velocity randomness is controlled by splitting the FoG term into two pieces, 1) the ``one-point" FoG term being independent of the separation vector between two different points, and 2) the ``correlated" FoG term appearing as an indefinite polynomials which is expanded in the same order as all other perturbative polynomials. Using 100 realizations of simulations, we find that the Gaussian FoG function with only one scale-independent free parameter works quite well, and that our new mapping formulation accurately reproduces the observed 2-dimensional density power spectrum in redshift space at the smallest scales by far, up to k~ 0.2 Mpc-1, considering the resolution of future experiments.

Transcriptional Control of Antioxidant Defense by the Circadian Clock

PubMed Central

Patel, Sonal A.; Velingkaar, Nikkhil S.

2014-01-01

Abstract Significance: The circadian clock, an internal timekeeping system, is implicated in the regulation of metabolism and physiology, and circadian dysfunctions are associated with pathological changes in model organisms and increased risk of some diseases in humans. Recent Advances: Data obtained in different organisms, including humans, have established a tight connection between the clock and cellular redox signaling making it among the major candidates for a link between the circadian system and physiological processes. Critical Issues: In spite of the recent progress in understanding the importance of the circadian clock in the regulation of reactive oxygen species homeostasis, molecular mechanisms and key regulators are mostly unknown. Future Directions: Here we review, with an emphasis on transcriptional control, the circadian-clock-dependent control of oxidative stress response system as a potential mechanism in age-associated diseases. We will discuss the roles of the core clock components such as brain and muscle ARNT-like 1, Circadian Locomotor Output Cycles Kaput, the circadian-clock-controlled transcriptional factors such as nuclear factor erythroid-2-related factor, and peroxisome proliferator-activated receptor and circadian clock control chromatin modifying enzymes from sirtuin family in the regulation of cellular and organism antioxidant defense. Antioxid. Redox Signal. 20, 2997–3006. PMID:24111970

A neuroeconomic theory of rational addiction and nonlinear time-perception.

PubMed

Takahashi, Taiki

2011-01-01

Neuroeconomic conditions for "rational addiction" (Becker & Murphy 1988) have been unknown. This paper derived the conditions for "rational addiction" by utilizing a nonlinear time-perception theory of "hyperbolic" discounting, which is mathematically equivalent to the q-exponential intertemporal choice model based on Tsallis' statistics. It is shown that (i) Arrow-Pratt measure for temporal cognition corresponds to the degree of irrationality (i.e., Prelec's "decreasing impatience" parameter of temporal discounting) and (ii) rationality in addicts is controlled by a nondimensionalization parameter of the logarithmic time-perception function. Furthermore, the present theory illustrates the possibility that addictive drugs increase impulsivity via dopaminergic neuroadaptation without increasing irrationality. Future directions in the application of the model to studies in neuroeconomics are discussed.

Characterizing Fatigue: The Effects of Ethnicity and Acculturation

PubMed Central

Cordero, Elizabeth D.; Loredo, Jose S.; Murray, Kate E.; Dimsdale, Joel E.

2012-01-01

It is unknown if fatigue measures like the Multidimensional Fatigue Symptom Inventory-Short Form (MFSI-SF; Stein, Jacobsen, Blanchard, & Thors, 2004) appropriately describe fatigue in Hispanics or if acculturation plays a role in fatigue. This study compared fatigue in community samples of Hispanics and Anglos. The MFSI-SF and pertinent questionnaires were administered to adults in San Diego County via telephone survey. Some differences in fatigue were observed in initial comparisons between Hispanics and Anglos, including when acculturation was considered. When age and education were controlled, Hispanics reported less general fatigue than Anglos, regardless of acculturation status, p = < .01. Exploratory factor analyses indicate that the MFSI-SF general-fatigue subscale was problematic for Hispanics. Implications, limitations, and future directions are discussed. PMID:22773899

Placental expression of anti-angiogenic proteins in mirror syndrome: a case report.

PubMed

Graham, N; Garrod, A; Bullen, P; Heazell, A E P

2012-06-01

Mirror syndrome is a rare disorder in which fetal hydrops is associated with maternal oedema, proteinuria and hypertension. The aetiology of the maternal condition is unknown, but it is thought to be related to preeclampsia. Few descriptions exist of placental morphology in mirror syndrome, but placentomegaly is consistently observed. In this case placental morphology showed villous oedema and syncytial nuclear aggregates where villi were in direct contact. Immunoperoxidase staining for VEGFR1 and Endoglin was more intense in mirror syndrome compared to gestational-age matched controls,and at a similar level to a case of preeclampsia. Placentally-derived anti-angiogenic factors may be involved in the pathogenesis of mirror syndrome. Copyright © 2012 Elsevier Ltd. All rights reserved.

Neural responses to fearful eyes in children with conduct problems and varying levels of callous-unemotional traits.

PubMed

Sebastian, C L; McCrory, E J; Dadds, M R; Cecil, C A M; Lockwood, P L; Hyde, Z H; De Brito, S A; Viding, E

2014-01-01

Children with conduct problems (CP) are a heterogeneous group. Those with high levels of callous-unemotional traits (CP/HCU) appear emotionally under-reactive at behavioural and neural levels whereas those with low levels of CU traits (CP/LCU) appear emotionally over-reactive, compared with typically developing (TD) controls. Investigating the degree to which these patterns of emotional reactivity are malleable may have important translational implications. Instructing participants with CP/HCU to focus on the eyes of fearful faces (i.e. the most salient feature) can ameliorate their fear-recognition deficits, but it is unknown whether this is mediated by amygdala response. It is also unknown whether focusing on fearful eyes is associated with increased amygdala reactivity in CP/LCU. Functional magnetic resonance imaging (fMRI) was used to measure neural responses to fearful and calm faces in children with CP/HCU, CP/LCU and TD controls (n = 17 per group). On half of trials participants looked for a blue dot anywhere within target faces; on the other half, participants were directed to focus on the eye region. Reaction time (RT) data showed that CP/LCU were selectively slowed in the fear/eyes condition. For the same condition, CP/LCU also showed increased amygdala and subgenual anterior cingulate cortex (sgACC)/orbitofrontal cortex (OFC) responses compared with TD controls. RT and amygdala response to fear/eyes were correlated in CP/LCU only. No effects of focusing on the eye region were observed in CP/HCU. These data extend the evidence base suggesting that CU traits index meaningful heterogeneity in conduct problems. Focusing on regulating reactive emotional responses may be a fruitful strategy for children with CP/LCU.

Efficacy and Toxicity of Chemoradiotherapy Using Intensity-Modulated Radiotherapy for Unknown Primary of Head and Neck

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

Sher, David J., E-mail: dsher@lroc.harvard.edu; Balboni, Tracy A.; Haddad, Robert I.

2011-08-01

Purpose: No single standard treatment paradigm is available for head-and-neck squamous cell carcinoma of an unknown primary (HNCUP). Bilateral neck radiotherapy with mucosal axis irradiation is widely used, with or without chemotherapy and/or surgical resection. Intensity-modulated radiotherapy (IMRT) is a highly conformal method for delivering radiation that is becoming the standard of care and might reduce the long-term treatment-related sequelae. We report the Dana-Farber Cancer Institute experience with IMRT-based treatment for HNCUP. Patients and Materials: A retrospective study of all patients treated at the Dana-Farber Cancer Institute for HNCUP with IMRT between August 2004 and January 2009. The primary endpointmore » was overall survival; the secondary endpoints were locoregional and distant control, and acute and chronic toxicity. Results: A total of 24 patients with HNCUP were included. Of these patients, 22 had Stage N2 disease or greater. All patients underwent neck computed tomography, positron emission tomography-computed tomography, and examination under anesthesia with directed biopsies. Of the 24 patients, 22 received concurrent chemotherapy, and 7 (29%) also underwent induction chemotherapy. The median involved nodal dose was 70 Gy, and the median mucosal dose was 60 Gy. With a median follow-up of 2.1 years, the 2-year actuarial overall survival and locoregional control rate was 92% and 100%, respectively. Only 25% of the patients had Grade 2 xerostomia, although 11 patients (46%) required esophageal dilation for stricture. Conclusion: In a single-institution series, IMRT-based chemoradiotherapy for HNCUP was associated with superb overall survival and locoregional control. The xerostomia rates were promising, but the aggressive therapy was associated with significant rates of esophageal stenosis.« less

Outcomes After Direct Thrombectomy or Combined Intravenous and Endovascular Treatment Are Not Different.

PubMed

Abilleira, Sònia; Ribera, Aida; Cardona, Pedro; Rubiera, Marta; López-Cancio, Elena; Amaro, Sergi; Rodríguez-Campello, Ana; Camps-Renom, Pol; Cánovas, David; de Miquel, Maria Angels; Tomasello, Alejandro; Remollo, Sebastian; López-Rueda, Antonio; Vivas, Elio; Perendreu, Joan; Gallofré, Miquel

2017-02-01

Whether intravenous thrombolysis adds a further benefit when given before endovascular thrombectomy (EVT) is unknown. Furthermore, intravenous thrombolysis delays time to groin puncture, mainly among drip and ship patients. Using region-wide registry data, we selected cases that received direct EVT or combined intravenous thrombolysis+EVT for anterior circulation strokes between January 2011 and October 2015. Treatment effect was estimated by stratification on a propensity score. The average odds ratios for the association of treatment with good outcome and death at 3 months and symptomatic bleedings at 24 hours were calculated with the Mantel-Haenszel test statistic. We included 599 direct EVT patients and 567 patients with combined treatment. Stratification through propensity score achieved balance of baseline characteristics across treatment groups. There was no association between treatment modality and good outcome (odds ratio, 0.97; 95% confidence interval, 0.74-1.27), death (odds ratio, 1.07; 95% confidence interval, 0.74-1.54), or symptomatic bleedings (odds ratio, 0.56; 95% confidence interval, 0.25-1.27). This observational study suggests that outcomes after direct EVT or combined intravenous thrombolysis+EVT are not different. If confirmed by a randomized controlled trial, it may have a significant impact on organization of stroke systems of care. © 2017 American Heart Association, Inc.

New developments of a knowledge based system (VEG) for inferring vegetation characteristics

NASA Technical Reports Server (NTRS)

Kimes, D. S.; Harrison, P. A.; Harrison, P. R.

1992-01-01

An extraction technique for inferring physical and biological surface properties of vegetation using nadir and/or directional reflectance data as input has been developed. A knowledge-based system (VEG) accepts spectral data of an unknown target as input, determines the best strategy for inferring the desired vegetation characteristic, applies the strategy to the target data, and provides a rigorous estimate of the accuracy of the inference. Progress in developing the system is presented. VEG combines methods from remote sensing and artificial intelligence, and integrates input spectral measurements with diverse knowledge bases. VEG has been developed to (1) infer spectral hemispherical reflectance from any combination of nadir and/or off-nadir view angles; (2) test and develop new extraction techniques on an internal spectral database; (3) browse, plot, or analyze directional reflectance data in the system's spectral database; (4) discriminate between user-defined vegetation classes using spectral and directional reflectance relationships; and (5) infer unknown view angles from known view angles (known as view angle extension).

Distributed Optimization Design of Continuous-Time Multiagent Systems With Unknown-Frequency Disturbances.

PubMed

Wang, Xinghu; Hong, Yiguang; Yi, Peng; Ji, Haibo; Kang, Yu

2017-05-24

In this paper, a distributed optimization problem is studied for continuous-time multiagent systems with unknown-frequency disturbances. A distributed gradient-based control is proposed for the agents to achieve the optimal consensus with estimating unknown frequencies and rejecting the bounded disturbance in the semi-global sense. Based on convex optimization analysis and adaptive internal model approach, the exact optimization solution can be obtained for the multiagent system disturbed by exogenous disturbances with uncertain parameters.

13-fold resolution gain through turbid layer via translated unknown speckle illumination

PubMed Central

Guo, Kaikai; Zhang, Zibang; Jiang, Shaowei; Liao, Jun; Zhong, Jingang; Eldar, Yonina C.; Zheng, Guoan

2017-01-01

Fluorescence imaging through a turbid layer holds great promise for various biophotonics applications. Conventional wavefront shaping techniques aim to create and scan a focus spot through the turbid layer. Finding the correct input wavefront without direct access to the target plane remains a critical challenge. In this paper, we explore a new strategy for imaging through turbid layer with a large field of view. In our setup, a fluorescence sample is sandwiched between two turbid layers. Instead of generating one focus spot via wavefront shaping, we use an unshaped beam to illuminate the turbid layer and generate an unknown speckle pattern at the target plane over a wide field of view. By tilting the input wavefront, we raster scan the unknown speckle pattern via the memory effect and capture the corresponding low-resolution fluorescence images through the turbid layer. Different from the wavefront-shaping-based single-spot scanning, the proposed approach employs many spots (i.e., speckles) in parallel for extending the field of view. Based on all captured images, we jointly recover the fluorescence object, the unknown optical transfer function of the turbid layer, the translated step size, and the unknown speckle pattern. Without direct access to the object plane or knowledge of the turbid layer, we demonstrate a 13-fold resolution gain through the turbid layer using the reported strategy. We also demonstrate the use of this technique to improve the resolution of a low numerical aperture objective lens allowing to obtain both large field of view and high resolution at the same time. The reported method provides insight for developing new fluorescence imaging platforms and may find applications in deep-tissue imaging. PMID:29359102

Adaptive output-feedback control for switched stochastic uncertain nonlinear systems with time-varying delay.

PubMed

Song, Zhibao; Zhai, Junyong

2018-04-01

This paper addresses the problem of adaptive output-feedback control for a class of switched stochastic time-delay nonlinear systems with uncertain output function, where both the control coefficients and time-varying delay are unknown. The drift and diffusion terms are subject to unknown homogeneous growth condition. By virtue of adding a power integrator technique, an adaptive output-feedback controller is designed to render that the closed-loop system is bounded in probability, and the state of switched stochastic nonlinear system can be globally regulated to the origin almost surely. A numerical example is provided to demonstrate the validity of the proposed control method. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Spacecraft Stabilization and Control for Capture of Non-Cooperative Space Objects

NASA Technical Reports Server (NTRS)

Joshi, Suresh; Kelkar, Atul G.

2014-01-01

This paper addresses stabilization and control issues in autonomous capture and manipulation of non-cooperative space objects such as asteroids, space debris, and orbital spacecraft in need of servicing. Such objects are characterized by unknown mass-inertia properties, unknown rotational motion, and irregular shapes, which makes it a challenging control problem. The problem is further compounded by the presence of inherent nonlinearities, signi cant elastic modes with low damping, and parameter uncertainties in the spacecraft. Robust dissipativity-based control laws are presented and are shown to provide global asymptotic stability in spite of model uncertainties and nonlinearities. It is shown that robust stabilization can be accomplished via model-independent dissipativity-based controllers using thrusters alone, while stabilization with attitude and position control can be accomplished using thrusters and torque actuators.

Adaptive non-predictor control of lower triangular uncertain nonlinear systems with an unknown time-varying delay in the input

NASA Astrophysics Data System (ADS)

Koo, Min-Sung; Choi, Ho-Lim

2018-01-01

In this paper, we consider a control problem for a class of uncertain nonlinear systems in which there exists an unknown time-varying delay in the input and lower triangular nonlinearities. Usually, in the existing results, input delays have been coupled with feedforward (or upper triangular) nonlinearities; in other words, the combination of lower triangular nonlinearities and input delay has been rare. Motivated by the existing controller for input-delayed chain of integrators with nonlinearity, we show that the control of input-delayed nonlinear systems with two particular types of lower triangular nonlinearities can be done. As a control solution, we propose a newly designed feedback controller whose main features are its dynamic gain and non-predictor approach. Three examples are given for illustration.

Destination Unknown.

ERIC Educational Resources Information Center

Brownstein, Andrew; Hoover, Eric

2001-01-01

Explores how, for college students, the events of September 11, 2001, have changed everything; the new directions they have taken vary as much as they do. Presents profiles of several students with differing perspectives. (EV)

Adaptive boundary concentration control using Zakai equation

NASA Astrophysics Data System (ADS)

Tenno, R.; Mendelson, A.

2010-06-01

A mean-variance control problem is formulated with respect to a partially observed nonlinear system that includes unknown constant parameters. A physical prototype of the system is the cathode surface reaction in an electrolysis cell, where the controller aim is to keep the boundary concentration of species in the near vicinity of the cathode surface low but not zero. The boundary concentration is a diffusion-controlled process observed through the measured current density and, in practice, controlled through the applied voltage. The former incomplete data control problem is converted to complete data-to the so-called separated control problem whose solution is given by the infinite-dimensional Zakai equation. In this article, the separated control problem is solved numerically using pathwise integration of the Zakai equation. This article demonstrates precise tracking of the target trajectory with a rapid convergence of estimates to unknown parameters, which take place simultaneously with control.

38. Photographic copy of photograph, photographer unknown, 26 March 1915 ...

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

38. Photographic copy of photograph, photographer unknown, 26 March 1915 (original print located at U.S. Bureau of Reclamation Upper Columbia Area Office, Yakima, Washington). " Dredge after failure of control dam." - Keechelus Dam, Yakima River, 10 miles northwest of Easton, Easton, Kittitas County, WA

39. Photographic copy of photograph, photographer unknown, 26 March 1915 ...

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

39. Photographic copy of photograph, photographer unknown, 26 March 1915 (original print located at U.S. Bureau of Reclamation Upper Columbia Area Office, Yakima, Washington). "View of control dam after failure." - Keechelus Dam, Yakima River, 10 miles northwest of Easton, Easton, Kittitas County, WA

Searching molecular structure databases with tandem mass spectra using CSI:FingerID

PubMed Central

Dührkop, Kai; Shen, Huibin; Meusel, Marvin; Rousu, Juho; Böcker, Sebastian

2015-01-01

Metabolites provide a direct functional signature of cellular state. Untargeted metabolomics experiments usually rely on tandem MS to identify the thousands of compounds in a biological sample. Today, the vast majority of metabolites remain unknown. We present a method for searching molecular structure databases using tandem MS data of small molecules. Our method computes a fragmentation tree that best explains the fragmentation spectrum of an unknown molecule. We use the fragmentation tree to predict the molecular structure fingerprint of the unknown compound using machine learning. This fingerprint is then used to search a molecular structure database such as PubChem. Our method is shown to improve on the competing methods for computational metabolite identification by a considerable margin. PMID:26392543

Procedures and results related to the direct determination of gravity anomalies from satellite and terrestrial gravity data

NASA Technical Reports Server (NTRS)

Rapp, R. H.

1974-01-01

The equations needed for the incorporation of gravity anomalies as unknown parameters in an orbit determination program are described. These equations were implemented in the Geodyn computer program which was used to process optical satellite observations. The arc dependent parameter unknowns, 184 unknown 15 deg and coordinates of 7 tracking stations were considered. Up to 39 arcs (5 to 7 days) involving 10 different satellites, were processed. An anomaly solution from the satellite data and a combination solution with 15 deg terrestrial anomalies were made. The limited data samples indicate that the method works. The 15 deg anomalies from various solutions and the potential coefficients implied by the different solutions are reported.

Disturbance observer based pitch control of wind turbines for disturbance rejection

NASA Astrophysics Data System (ADS)

Yuan, Yuan; Chen, Xu; Tang, Jiong

2016-04-01

In this research, a disturbance observer based (DOB) control scheme is illustrated to reject the unknown low frequency disturbances to wind turbines. Specifically, we aim at maintaining the constant output power but achieving better generator speed regulation when the wind turbine is operated at time-varying and turbulent wind field. The disturbance observer combined with a filter is designed to asymptotically reject the persistent unknown time-varying disturbances. The proposed algorithm is tested in both linearized and nonlinear NREL offshore 5-MW baseline wind turbine. The application of this DOB pitch controller achieves improved power and speed regulation in Region 3 compared with a baseline gain scheduling PID collective controller both in linearized and nonlinear plant.

Decentralized adaptive neural control for high-order interconnected stochastic nonlinear time-delay systems with unknown system dynamics.

PubMed

Si, Wenjie; Dong, Xunde; Yang, Feifei

2018-03-01

This paper is concerned with the problem of decentralized adaptive backstepping state-feedback control for uncertain high-order large-scale stochastic nonlinear time-delay systems. For the control design of high-order large-scale nonlinear systems, only one adaptive parameter is constructed to overcome the over-parameterization, and neural networks are employed to cope with the difficulties raised by completely unknown system dynamics and stochastic disturbances. And then, the appropriate Lyapunov-Krasovskii functional and the property of hyperbolic tangent functions are used to deal with the unknown unmatched time-delay interactions of high-order large-scale systems for the first time. At last, on the basis of Lyapunov stability theory, the decentralized adaptive neural controller was developed, and it decreases the number of learning parameters. The actual controller can be designed so as to ensure that all the signals in the closed-loop system are semi-globally uniformly ultimately bounded (SGUUB) and the tracking error converges in the small neighborhood of zero. The simulation example is used to further show the validity of the design method. Copyright © 2018 Elsevier Ltd. All rights reserved.

Switched-Observer-Based Adaptive Neural Control of MIMO Switched Nonlinear Systems With Unknown Control Gains.

PubMed

Long, Lijun; Zhao, Jun

2017-07-01

In this paper, the problem of adaptive neural output-feedback control is addressed for a class of multi-input multioutput (MIMO) switched uncertain nonlinear systems with unknown control gains. Neural networks (NNs) are used to approximate unknown nonlinear functions. In order to avoid the conservativeness caused by adoption of a common observer for all subsystems, an MIMO NN switched observer is designed to estimate unmeasurable states. A new switched observer-based adaptive neural control technique for the problem studied is then provided by exploiting the classical average dwell time (ADT) method and the backstepping method and the Nussbaum gain technique. It effectively handles the obstacle about the coexistence of multiple Nussbaum-type function terms, and improves the classical ADT method, since the exponential decline property of Lyapunov functions for individual subsystems is no longer satisfied. It is shown that the technique proposed is able to guarantee semiglobal uniformly ultimately boundedness of all the signals in the closed-loop system under a class of switching signals with ADT, and the tracking errors converge to a small neighborhood of the origin. The effectiveness of the approach proposed is illustrated by its application to a two inverted pendulum system.

Preliminary Investigation of Workload on Intrastate Bus Traffic Controllers

NASA Astrophysics Data System (ADS)

Yen Bin, Teo; Azlis-Sani, Jalil; Nur Annuar Mohd Yunos, Muhammad; Ismail, S. M. Sabri S. M.; Tajedi, Noor Aqilah Ahmad

2016-11-01

The daily routine of bus traffic controller which involves high mental processes would have a direct impact on the level of workload. To date, the level of workload on the bus traffic controllers in Malaysia is relatively unknown. Excessive workload on bus traffic controllers would affect the control and efficiency of the system. This paper served to study the workload on bus traffic controllers and justify the needs to conduct further detailed research on this field. The objectives of this research are to identify the level of workload on the intrastate bus traffic controllers. Based on the results, recommendations will be proposed for improvements and future studies. The level of workload for the bus traffic controllers is quantified using questionnaire adapted from NASA TLX. Interview sessions were conducted for validation of workload. Sixteen respondents were involved and it was found that the average level of workload based on NASA TLX was 6.91. It was found that workload is not affected by gender and marital status. This study also showed that the level of workload and working experience of bus traffic controllers has a strong positive linear relationship. This study would serve as a guidance and reference related to this field. Since this study is a preliminary investigation, further detailed studies could be conducted to obtain a better comprehension regarding the bus traffic controllers.

Robust approximation-free prescribed performance control for nonlinear systems and its application

NASA Astrophysics Data System (ADS)

Sun, Ruisheng; Na, Jing; Zhu, Bin

2018-02-01

This paper presents a robust prescribed performance control approach and its application to nonlinear tail-controlled missile systems with unknown dynamics and uncertainties. The idea of prescribed performance function (PPF) is incorporated into the control design, such that both the steady-state and transient control performance can be strictly guaranteed. Unlike conventional PPF-based control methods, we further tailor a recently proposed systematic control design procedure (i.e. approximation-free control) using the transformed tracking error dynamics, which provides a proportional-like control action. Hence, the function approximators (e.g. neural networks, fuzzy systems) that are widely used to address the unknown nonlinearities in the nonlinear control designs are not needed. The proposed control design leads to a robust yet simplified function approximation-free control for nonlinear systems. The closed-loop system stability and the control error convergence are all rigorously proved. Finally, comparative simulations are conducted based on nonlinear missile systems to validate the improved response and the robustness of the proposed control method.

Electromagnetic spectrum management system

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

Seastrand, Douglas R.

A system for transmitting a wireless countermeasure signal to disrupt third party communications is disclosed that include an antenna configured to receive wireless signals and transmit wireless counter measure signals such that the wireless countermeasure signals are responsive to the received wireless signals. A receiver processes the received wireless signals to create processed received signal data while a spectrum control module subtracts known source signal data from the processed received signal data to generate unknown source signal data. The unknown source signal data is based on unknown wireless signals, such as enemy signals. A transmitter is configured to process themore » unknown source signal data to create countermeasure signals and transmit a wireless countermeasure signal over the first antenna or a second antenna to thereby interfere with the unknown wireless signals.« less

Existence conditions for unknown input functional observers

NASA Astrophysics Data System (ADS)

Fernando, T.; MacDougall, S.; Sreeram, V.; Trinh, H.

2013-01-01

This article presents necessary and sufficient conditions for the existence and design of an unknown input Functional observer. The existence of the observer can be verified by computing a nullspace of a known matrix and testing some matrix rank conditions. The existence of the observer does not require the satisfaction of the observer matching condition (i.e. Equation (16) in Hou and Muller 1992, 'Design of Observers for Linear Systems with Unknown Inputs', IEEE Transactions on Automatic Control, 37, 871-875), is not limited to estimating scalar functionals and allows for arbitrary pole placement. The proposed observer always exists when a state observer exists for the unknown input system, and furthermore, the proposed observer can exist even in some instances when an unknown input state observer does not exist.

Benefits and Risks of Cochlear Implants

MedlinePlus

... The cochlear implant stimulates the nerves directly with electrical currents. Although this stimulation appears to be safe, the long term effect of these electrical currents on the nerves is unknown. May not ...

34 CFR 685.203 - Loan limits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... an adverse credit history, or the parent's whereabouts are unknown. A parent's refusal to borrow a... expected family contribution for that period. (k) Any TEACH Grants that have been converted to Direct...

Navigation.

PubMed

Wiltschko, Roswitha

2017-07-01

Experiments with migrating birds displaced during autumn migration outside their normal migration corridor reveal two different navigational strategies: adult migrants compensate for the displacement, and head towards their traditional wintering areas, whereas young first-time migrants continue in their migratory direction. Young birds are guided to their still unknown goal by a genetically coded migration program that indicates duration and direction(s) of the migratory flight by controlling the amount of migratory restlessness and the compass course(s) with respect to the geomagnetic field and celestial rotation. Adult migrants that have already wintered and are familiar with the goal area approach the goal by true navigation, specifically heading towards it and changing their course correspondingly after displacement. During their first journey, young birds experience the distribution of potential navigational factors en route and in their winter home, which allows them to truly navigate on their next migrations. The navigational factors used appear to include magnetic intensity as a component in their multi-modal navigational 'map'; olfactory input is also involved, even if it is not yet entirely clear in what way. The mechanisms of migratory birds for true navigation over long distances appear to be in principle similar to those discussed for by homing pigeons.

Potential for direct interspecies electron transfer in an electric-anaerobic system to increase methane production from sludge digestion

PubMed Central

Zhao, Zhiqiang; Zhang, Yaobin; Wang, Liying; Quan, Xie

2015-01-01

Direct interspecies electron transfer (DIET) between Geobacter species and Methanosaeta species is an alternative to interspecies hydrogen transfer (IHT) in anaerobic digester, which however has not been established in anaerobic sludge digestion as well as in bioelectrochemical systems yet. In this study, it was found that over 50% of methane production of an electric-anaerobic sludge digester was resulted from unknown pathway. Pyrosequencing analysis revealed that Geobacter species were significantly enriched with electrodes. Fluorescence in situ hybridization (FISH) further confirmed that the dominant Geobacter species enriched belonged to Geobacter metallireducens. Together with Methanosaeta species prevailing in the microbial communities, the direct electron exchange between Geobacter species and Methanosaeta species might be an important reason for the “unknown” increase of methane production. Conductivity of the sludge in this electric-anaerobic digester was about 30% higher than that of the sludge in a control digester without electrodes. This study not only revealed for the first time that DIET might be the important mechanism on the methanogenesis of bioelectrochemical system, but also provided a new method to enhance DIET by means of bioelectric enrichment of Geobacter species. PMID:26057581

Policy improvement by a model-free Dyna architecture.

PubMed

Hwang, Kao-Shing; Lo, Chia-Yue

2013-05-01

The objective of this paper is to accelerate the process of policy improvement in reinforcement learning. The proposed Dyna-style system combines two learning schemes, one of which utilizes a temporal difference method for direct learning; the other uses relative values for indirect learning in planning between two successive direct learning cycles. Instead of establishing a complicated world model, the approach introduces a simple predictor of average rewards to actor-critic architecture in the simulation (planning) mode. The relative value of a state, defined as the accumulated differences between immediate reward and average reward, is used to steer the improvement process in the right direction. The proposed learning scheme is applied to control a pendulum system for tracking a desired trajectory to demonstrate its adaptability and robustness. Through reinforcement signals from the environment, the system takes the appropriate action to drive an unknown dynamic to track desired outputs in few learning cycles. Comparisons are made between the proposed model-free method, a connectionist adaptive heuristic critic, and an advanced method of Dyna-Q learning in the experiments of labyrinth exploration. The proposed method outperforms its counterparts in terms of elapsed time and convergence rate.

Comparison of antral tap with endoscopically directed nasal culture.

PubMed

Casiano, R R; Cohn, S; Villasuso, E; Brown, M; Memari, F; Barquist, E; Namias, N

2001-08-01

The diagnosis of acute bacterial rhinosinusitis continues to generate controversy in critically ill patients. The efficacy of endoscopically directed cultures in these patients is unknown. We compared antral tap (AT) with endoscopic tissue culture (ETC) of the osteomeatal complex in an intensive care unit (ICU) setting. Twenty patients admitted to a surgical/trauma ICU were evaluated by AT and ENB for the presence of rhinosinusitis. All patients had 1) a fever of unknown origin without resolution on empiric antibiotic therapy for > or =48 hrs; 2) other sources of fever ruled out; 3) computed tomography scan evidence of mucoperiosteal thickening +/- sinus air/fluid levels; and 4) attempt at conservative treatment with topical decongestants and removal of all nasal intubation. Microbiologic data were collected and analyzed for any statistical difference between groups. A total of 29 sides underwent simultaneous tap and endoscopically directed tissue culture. The mean age was 40 years (range, 23-77 y) with 85% being males. Fifteen of 20 (75%) patients in the AT group were culture-positive. Of the 49 isolates from the AT, 55% yielded Gram-negative bacilli (Acinetobacter sp. 37%) and 45% yielded Gram-positive cocci. The ETC group was culture-positive in 18 of 20 (90%) patients. Of the 52 isolates from the ETC, Gram-negative bacilli were found in 58% (Acinetobacter sp. 33%) and 42% yielded Gram-positive cocci. The ETCs were culture-positive in all but 1 patient with positive taps. There appeared to be a concordance between AT and ETC in 60% of the patients. In five instances (25%), results of the AT or ETC changed ICU management. Two patients ultimately required sinus surgery. Sinus taps and/or endoscopically directed tissue cultures led to a change in ICU care in 25% of ICU patients studied. In patients with fever of unknown origin and computed tomography evidence of sinusitis, an antral tap continues to provide important information concerning maxillary sinusitis. However, ETC may give as good a representation of the microbiology and secondary inflammatory changes responsible for bacterial ICU rhinosinusitis causing fever of unknown origin. Further study on a larger group of patients is needed.

Anodal transcranial direct current stimulation over the primary motor cortex does not enhance the learning benefits of self-controlled feedback schedules.

PubMed

Carter, Michael J; Smith, Victoria; Carlsen, Anthony N; Ste-Marie, Diane M

2018-05-01

A distinct learning advantage has been shown when participants control their knowledge of results (KR) scheduling during practice compared to when the same KR schedule is imposed on the learner without choice (i.e., yoked schedules). Although the learning advantages of self-controlled KR schedules are well-documented, the brain regions contributing to these advantages remain unknown. Identifying key brain regions would not only advance our theoretical understanding of the mechanisms underlying self-controlled learning advantages, but would also highlight regions that could be targeted in more applied settings to boost the already beneficial effects of self-controlled KR schedules. Here, we investigated whether applying anodal transcranial direct current stimulation (tDCS) to the primary motor cortex (M1) would enhance the typically found benefits of learning a novel motor skill with a self-controlled KR schedule. Participants practiced a spatiotemporal task in one of four groups using a factorial combination of KR schedule (self-controlled vs. yoked) and tDCS (anodal vs. sham). Testing occurred on two consecutive days with spatial and temporal accuracy measured on both days and learning was assessed using 24-h retention and transfer tests without KR. All groups improved their performance in practice and a significant effect for practicing with a self-controlled KR schedule compared to a yoked schedule was found for temporal accuracy in transfer, but a similar advantage was not evident in retention. There were no significant differences as a function of KR schedule or tDCS for spatial accuracy in retention or transfer. The lack of a significant tDCS effect suggests that M1 may not strongly contribute to self-controlled KR learning advantages; however, caution is advised with this interpretation as typical self-controlled learning benefits were not strongly replicated in the present experiment.

Opposite optimal current flow directions for induction of neuroplasticity and excitation threshold in the human motor cortex.

PubMed

Sommer, Martin; Norden, Christoph; Schmack, Lars; Rothkegel, Holger; Lang, Nicolas; Paulus, Walter

2013-05-01

Directional sensitivity is relevant for the excitability threshold of the human primary motor cortex, but its importance for externally induced plasticity is unknown. To study the influence of current direction on two paradigms inducing neuroplasticity by repetitive transcranial magnetic stimulation (rTMS). We studied short-lasting after-effects induced in the human primary motor cortex of 8 healthy subjects, using 5 Hz rTMS applied in six blocks of 200 pulses each, at 90% active motor threshold. We controlled for intensity, frequency, waveform and spinal effects. Only biphasic pulses with the effective component delivered in an anterioposterior direction (henceforth posteriorly directed) in the brain yielded an increase of motor-evoked potential (MEP) amplitudes outlasting rTMS. MEP latencies and F-wave amplitudes remained unchanged. Biphasic pulses directed posteroanterior (i.e. anteriorly) were ineffective, as were monophasic pulses from either direction. A 1 Hz study in a group of 12 healthy subjects confirmed facilitation after posteriorly directed biphasic pulses only. The anisotropy of the human primary motor cortex is relevant for induction of plasticity by subtreshold rTMS, with a current flow opposite to that providing lowest excitability thresholds. This is consistent with the idea of TMS primarily targeting cortical columns of the phylogenetically new M1 in the anterior bank of the central sulcus. For these, anteriorly directed currents are soma-depolarizing, therefore optimal for low thresholds, whereas posteriorly directed currents are soma-hyperpolarizing, likely dendrite-depolarizing and bested suited for induction of plasticity. Our findings should help focus and enhance rTMS effects in experimental and clinical settings. Copyright © 2013 Elsevier Inc. All rights reserved.

Spatial curvilinear path following control of underactuated AUV with multiple uncertainties.

PubMed

Miao, Jianming; Wang, Shaoping; Zhao, Zhiping; Li, Yuan; Tomovic, Mileta M

2017-03-01

This paper investigates the problem of spatial curvilinear path following control of underactuated autonomous underwater vehicles (AUVs) with multiple uncertainties. Firstly, in order to design the appropriate controller, path following error dynamics model is constructed in a moving Serret-Frenet frame, and the five degrees of freedom (DOFs) dynamic model with multiple uncertainties is established. Secondly, the proposed control law is separated into kinematic controller and dynamic controller via back-stepping technique. In the case of kinematic controller, to overcome the drawback of dependence on the accurate vehicle model that are present in a number of path following control strategies described in the literature, the unknown side-slip angular velocity and attack angular velocity are treated as uncertainties. Whereas in the case of dynamic controller, the model parameters perturbations, unknown external environmental disturbances and the nonlinear hydrodynamic damping terms are treated as lumped uncertainties. Both kinematic and dynamic uncertainties are estimated and compensated by designed reduced-order linear extended state observes (LESOs). Thirdly, feedback linearization (FL) based control law is implemented for the control model using the estimates generated by reduced-order LESOs. For handling the problem of computational complexity inherent in the conventional back-stepping method, nonlinear tracking differentiators (NTDs) are applied to construct derivatives of the virtual control commands. Finally, the closed loop stability for the overall system is established. Simulation and comparative analysis demonstrate that the proposed controller exhibits enhanced performance in the presence of internal parameter variations, external unknown disturbances, unmodeled nonlinear damping terms, and measurement noises. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Finite-time sliding surface constrained control for a robot manipulator with an unknown deadzone and disturbance.

PubMed

Ik Han, Seong; Lee, Jangmyung

2016-11-01

This paper presents finite-time sliding mode control (FSMC) with predefined constraints for the tracking error and sliding surface in order to obtain robust positioning of a robot manipulator with input nonlinearity due to an unknown deadzone and external disturbance. An assumed model feedforward FSMC was designed to avoid tedious identification procedures for the manipulator parameters and to obtain a fast response time. Two constraint switching control functions based on the tracking error and finite-time sliding surface were added to the FSMC to guarantee the predefined tracking performance despite the presence of an unknown deadzone and disturbance. The tracking error due to the deadzone and disturbance can be suppressed within the predefined error boundary simply by tuning the gain value of the constraint switching function and without the addition of an extra compensator. Therefore, the designed constraint controller has a simpler structure than conventional transformed error constraint methods and the sliding surface constraint scheme can also indirectly guarantee the tracking error constraint while being more stable than the tracking error constraint control. A simulation and experiment were performed on an articulated robot manipulator to validate the proposed control schemes. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Neural network L1 adaptive control of MIMO systems with nonlinear uncertainty.

PubMed

Zhen, Hong-tao; Qi, Xiao-hui; Li, Jie; Tian, Qing-min

2014-01-01

An indirect adaptive controller is developed for a class of multiple-input multiple-output (MIMO) nonlinear systems with unknown uncertainties. This control system is comprised of an L 1 adaptive controller and an auxiliary neural network (NN) compensation controller. The L 1 adaptive controller has guaranteed transient response in addition to stable tracking. In this architecture, a low-pass filter is adopted to guarantee fast adaptive rate without generating high-frequency oscillations in control signals. The auxiliary compensation controller is designed to approximate the unknown nonlinear functions by MIMO RBF neural networks to suppress the influence of uncertainties. NN weights are tuned on-line with no prior training and the project operator ensures the weights bounded. The global stability of the closed-system is derived based on the Lyapunov function. Numerical simulations of an MIMO system coupled with nonlinear uncertainties are used to illustrate the practical potential of our theoretical results.

Identification of the Regulon of AphB and Its Essential Roles in LuxR and Exotoxin Asp Expression in the Pathogen Vibrio alginolyticus.

PubMed

Gao, Xiating; Liu, Yang; Liu, Huan; Yang, Zhen; Liu, Qin; Zhang, Yuanxing; Wang, Qiyao

2017-10-15

In Vibrio species, AphB is essential to activate virulence cascades by sensing low-pH and anaerobiosis signals; however, its regulon remains largely unknown. Here, AphB is found to be a key virulence regulator in Vibrio alginolyticus , a pathogen for marine animals and humans. Chromatin immunoprecipitation followed by high-throughput DNA sequencing (ChIP-seq) enabled the detection of 20 loci in the V. alginolyticus genome that contained AphB-binding peaks. An AphB-specific binding consensus was confirmed by electrophoretic mobility shift assays (EMSAs), and the regulation of genes flanking such binding sites was demonstrated using quantitative real-time PCR analysis. AphB binds directly to its own promoter and positively controls its own expression in later growth stages. AphB also activates the expression of the exotoxin Asp by binding directly to the promoter regions of asp and the master quorum-sensing (QS) regulator luxR DNase I footprinting analysis uncovered distinct AphB-binding sites (BBS) in these promoters. Furthermore, a BBS in the luxR promoter region overlaps that of LuxR-binding site I, which mediates the positive control of luxR promoter activity by AphB. This study provides new insights into the AphB regulon and reveals the mechanisms underlying AphB regulation of physiological adaptation and QS-controlled virulence in V. alginolyticus IMPORTANCE In this work, AphB is determined to play essential roles in the expression of genes associated with QS, physiology, and virulence in V. alginolyticus , a pathogen for marine animals and humans. AphB was found to bind directly to 20 genes and control their expression by a 17-bp consensus binding sequence. Among the 20 genes, the aphB gene itself was identified to be positively autoregulated, and AphB also positively controlled asp and luxR expression. Taken together, these findings improve our understanding of the roles of AphB in controlling physiological adaptation and QS-controlled virulence gene expression. Copyright © 2017 American Society for Microbiology.

Continuous and difficult discrete cognitive tasks promote improved stability in older adults.

PubMed

Lajoie, Yves; Jehu, Deborah A; Richer, Natalie; Chan, Alan

2017-06-01

Directing attention away from postural control and onto a cognitive task affords the emergence of automatic control processes. Perhaps the continuous withdrawal of attention from the postural task facilitates an automatization of posture as opposed to only intermittent withdrawal; however this is unknown in the aging population. Twenty older adults (69.9±3.5years) stood with feet together on a force platform for 60s while performing randomly assigned discrete and continuous cognitive tasks. Participants were instructed to stand comfortably with their arms by their sides while verbally responding to the auditory stimuli as fast as possible during the discrete tasks, or mentally performing the continuous cognitive tasks. Participants also performed single-task standing. Results demonstrate significant reductions in sway amplitude and sway variability for the difficult discrete task as well as the continuous tasks relative to single-task standing. The continuous cognitive tasks also prompted greater frequency of sway in the anterior-posterior direction compared to single-standing and discrete tasks, and greater velocity in both directions compared to single-task standing, which could suggest ankle stiffening. No differences in the simple discrete condition were shown compared to single-task standing, perhaps due to the simplicity of the task. Therefore, we propose that the level of difficulty of the task, the specific neuropsychological process engaged during the cognitive task, and the type of task (discrete vs. continuous) influence postural control in older adults. Dual-tasking is a common activity of daily living; this work provides insight into the age-related changes in postural stability and attention demand. Copyright © 2017 Elsevier B.V. All rights reserved.

The RPG gene of Medicago truncatula controls Rhizobium-directed polar growth during infection

PubMed Central

Arrighi, Jean-François; Godfroy, Olivier; de Billy, Françoise; Saurat, Olivier; Jauneau, Alain; Gough, Clare

2008-01-01

Rhizobia can infect roots of host legume plants and induce new organs called nodules, in which they fix atmospheric nitrogen. Infection generally starts with root hair curling, then proceeds inside newly formed, intracellular tubular structures called infection threads. A successful symbiotic interaction relies on infection threads advancing rapidly at their tips by polar growth through successive cell layers of the root toward developing nodule primordia. To identify a plant component that controls this tip growth process, we characterized a symbiotic mutant of Medicago truncatula, called rpg for rhizobium-directed polar growth. In this mutant, nitrogen-fixing nodules were rarely formed due to abnormally thick and slowly progressing infection threads. Root hair curling was also abnormal, indicating that the RPG gene fulfils an essential function in the process whereby rhizobia manage to dominate the process of induced tip growth for root hair infection. Map-based cloning of RPG revealed a member of a previously unknown plant-specific gene family encoding putative long coiled-coil proteins we have called RRPs (RPG-related proteins) and characterized by an “RRP domain” specific to this family. RPG expression was strongly associated with rhizobial infection, and the RPG protein showed a nuclear localization, indicating that this symbiotic gene constitutes an important component of symbiotic signaling. PMID:18621693

The RPG gene of Medicago truncatula controls Rhizobium-directed polar growth during infection.

PubMed

Arrighi, Jean-François; Godfroy, Olivier; de Billy, Françoise; Saurat, Olivier; Jauneau, Alain; Gough, Clare

2008-07-15

Rhizobia can infect roots of host legume plants and induce new organs called nodules, in which they fix atmospheric nitrogen. Infection generally starts with root hair curling, then proceeds inside newly formed, intracellular tubular structures called infection threads. A successful symbiotic interaction relies on infection threads advancing rapidly at their tips by polar growth through successive cell layers of the root toward developing nodule primordia. To identify a plant component that controls this tip growth process, we characterized a symbiotic mutant of Medicago truncatula, called rpg for rhizobium-directed polar growth. In this mutant, nitrogen-fixing nodules were rarely formed due to abnormally thick and slowly progressing infection threads. Root hair curling was also abnormal, indicating that the RPG gene fulfils an essential function in the process whereby rhizobia manage to dominate the process of induced tip growth for root hair infection. Map-based cloning of RPG revealed a member of a previously unknown plant-specific gene family encoding putative long coiled-coil proteins we have called RRPs (RPG-related proteins) and characterized by an "RRP domain" specific to this family. RPG expression was strongly associated with rhizobial infection, and the RPG protein showed a nuclear localization, indicating that this symbiotic gene constitutes an important component of symbiotic signaling.

Dual measurement self-sensing technique of NiTi actuators for use in robust control

NASA Astrophysics Data System (ADS)

Gurley, Austin; Lambert, Tyler Ross; Beale, David; Broughton, Royall

2017-10-01

Using a shape memory alloy actuator as both an actuator and a sensor provides huge benefits in cost reduction and miniaturization of robotic devices. Despite much effort, reliable and robust self-sensing (using the actuator as a position sensor) had not been achieved for general temperature, loading, hysteresis path, and fatigue conditions. Prior research has sought to model the intricacies of the electrical resistivity changes within the NiTi material. However, for the models to be solvable, nearly every previous technique only models the actuator within very specific boundary conditions. Here, we measure both the voltage across the entire NiTi wire and of a fixed-length segment of it; these dual measurements allow direct calculation of the actuator length without a material model. We review previous self-sensing literature, illustrate the mechanism design that makes the new technique possible, and use the dual measurement technique to determine the length of a single straight wire actuator under controlled conditions. This robust measurement can be used for feedback control in unknown ambient and loading conditions.

Using manufacturing message specification for monitor and control at Venus

NASA Technical Reports Server (NTRS)

Heuser, W. Randy; Chen, Richard L.; Stockett, Michael H.

1993-01-01

The flexibility and robustness of a monitor and control (M&C) system are a direct result of the underlying interprocessor communications architecture. A new architecture for M&C at the Deep Space Communications Complexes (DSCC's) has been developed based on the Manufacturing Message Specification (MMS) process control standard of the Open System Interconnection (OSI) suite of protocols. This architecture has been tested both in a laboratory environment and under operational conditions at the Deep Space Network (DSN) experimental Venus station (DSS-13). The Venus experience in the application of OSI standards to support M&C has been extremely successful. MMS meets the functional needs of the station and provides a level of flexibility and responsiveness previously unknown in that environment. The architecture is robust enough to meet current operational needs and flexible enough to provide a migration path for new subsystems. This paper will describe the architecture of the Venus M&C system, discuss how MMS was used and the requirements this imposed on other parts of the system, and provide results from systems and operational testing at the Venus site.

The Tbr2 Molecular Network Controls Cortical Neuronal Differentiation Through Complementary Genetic and Epigenetic Pathways.

PubMed

Sessa, Alessandro; Ciabatti, Ernesto; Drechsel, Daniela; Massimino, Luca; Colasante, Gaia; Giannelli, Serena; Satoh, Takashi; Akira, Shizuo; Guillemot, Francois; Broccoli, Vania

2017-06-01

The T-box containing Tbr2 gene encodes for a transcription factor essential for the specification of the intermediate neural progenitors (INPs) originating the excitatory neurons of the cerebral cortex. However, its overall mechanism of action, direct target genes and cofactors remain unknown. Herein, we carried out global gene expression profiling combined with genome-wide binding site identification to determine the molecular pathways regulated by TBR2 in INPs. This analysis led to the identification of novel protein-protein interactions that control multiple features of INPs including cell-type identity, morphology, proliferation and migration dynamics. In particular, NEUROG2 and JMJD3 were found to associate with TBR2 revealing unexplored TBR2-dependent mechanisms. These interactions can explain, at least in part, the role of this transcription factor in the implementation of the molecular program controlling developmental milestones during corticogenesis. These data identify TBR2 as a major determinant of the INP-specific traits by regulating both genetic and epigenetic pathways. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Yeast heterochromatin regulators Sir2 and Sir3 act directly at euchromatic DNA replication origins.

PubMed

Hoggard, Timothy A; Chang, FuJung; Perry, Kelsey Rae; Subramanian, Sandya; Kenworthy, Jessica; Chueng, Julie; Shor, Erika; Hyland, Edel M; Boeke, Jef D; Weinreich, Michael; Fox, Catherine A

2018-05-01

Most active DNA replication origins are found within euchromatin, while origins within heterochromatin are often inactive or inhibited. In yeast, origin activity within heterochromatin is negatively controlled by the histone H4K16 deacetylase, Sir2, and at some heterochromatic loci also by the nucleosome binding protein, Sir3. The prevailing view has been that direct functions of Sir2 and Sir3 are confined to heterochromatin. However, growth defects in yeast mutants compromised for loading the MCM helicase, such as cdc6-4, are suppressed by deletion of either SIR2 or SIR3. While these and other observations indicate that SIR2,3 can have a negative impact on at least some euchromatic origins, the genomic scale of this effect was unknown. It was also unknown whether this suppression resulted from direct functions of Sir2,3 within euchromatin, or was an indirect effect of their previously established roles within heterochromatin. Using MCM ChIP-Seq, we show that a SIR2 deletion rescued MCM complex loading at ~80% of euchromatic origins in cdc6-4 cells. Therefore, Sir2 exhibited a pervasive effect at the majority of euchromatic origins. Using MNase-H4K16ac ChIP-Seq, we show that origin-adjacent nucleosomes were depleted for H4K16 acetylation in a SIR2-dependent manner in wild type (i.e. CDC6) cells. In addition, we present evidence that both Sir2 and Sir3 bound to nucleosomes adjacent to euchromatic origins. The relative levels of each of these molecular hallmarks of yeast heterochromatin-SIR2-dependent H4K16 hypoacetylation, Sir2, and Sir3 -correlated with how strongly a SIR2 deletion suppressed the MCM loading defect in cdc6-4 cells. Finally, a screen for histone H3 and H4 mutants that could suppress the cdc6-4 growth defect identified amino acids that map to a surface of the nucleosome important for Sir3 binding. We conclude that heterochromatin proteins directly modify the local chromatin environment of euchromatic DNA replication origins.

Four Chemical Trends Will Shape the Next Decade's Directions in Perfluoroalkyl and Polyfluoroalkyl Substances Research.

PubMed

Kotthoff, Matthias; Bücking, Mark

2018-01-01

Per- and polyfluoroalkyl substances (PFAS) represent a versatile group of ubiquitously occurring chemicals of increasing regulatory concern. The past years lead to an ever expanding portfolio of detected anthropogenic PFAS in numerous products encountered in daily life. Yet no clear picture of the full range of individual substance that comprise PFAS is available and this challenges analytical and engineering sciences. Authorities struggle to cope with uncertainties in managing risk of harm posed by PFAS. This is a result of an incomplete understanding of the range of compounds that they comprise in differing products. There are analytical uncertainties identifying PFAS and estimating the concentrations of the total PFAS load individual molecules remain unknown. There are four major trends from the chemical perspective that will shape PFAS research for the next decade. Mobility: A wide and dynamic distribution of short chain PFAS due to their high polarity, persistency and volatility.Substitution of regulated substances: The ban or restrictions of individual molecules will lead to a replacement with substitutes of similar concern.Increase in structural diversity of existing PFAS molecules: Introduction of e.g., hydrogens and chlorine atoms instead of fluorine, as well as branching and cross-linking lead to a high versatility of unknown target molecules.Unknown "Dark Matter": The amount, identity, formation pathways, and transformation dynamics of polymers and PFAS precursors are largely unknown. These directions require optimized analytical setups, especially multi-methods, and semi-specific tools to determine PFAS-sum parameters in any relevant matrix.

Four Chemical Trends Will Shape the Next Decade's Directions in Perfluoroalkyl and Polyfluoroalkyl Substances Research

PubMed Central

Kotthoff, Matthias; Bücking, Mark

2018-01-01

Per- and polyfluoroalkyl substances (PFAS) represent a versatile group of ubiquitously occurring chemicals of increasing regulatory concern. The past years lead to an ever expanding portfolio of detected anthropogenic PFAS in numerous products encountered in daily life. Yet no clear picture of the full range of individual substance that comprise PFAS is available and this challenges analytical and engineering sciences. Authorities struggle to cope with uncertainties in managing risk of harm posed by PFAS. This is a result of an incomplete understanding of the range of compounds that they comprise in differing products. There are analytical uncertainties identifying PFAS and estimating the concentrations of the total PFAS load individual molecules remain unknown. There are four major trends from the chemical perspective that will shape PFAS research for the next decade. Mobility: A wide and dynamic distribution of short chain PFAS due to their high polarity, persistency and volatility.Substitution of regulated substances: The ban or restrictions of individual molecules will lead to a replacement with substitutes of similar concern.Increase in structural diversity of existing PFAS molecules: Introduction of e.g., hydrogens and chlorine atoms instead of fluorine, as well as branching and cross-linking lead to a high versatility of unknown target molecules.Unknown “Dark Matter”: The amount, identity, formation pathways, and transformation dynamics of polymers and PFAS precursors are largely unknown. These directions require optimized analytical setups, especially multi-methods, and semi-specific tools to determine PFAS-sum parameters in any relevant matrix. PMID:29675408

Dual Rate Adaptive Control for an Industrial Heat Supply Process Using Signal Compensation Approach

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

Chai, Tianyou; Jia, Yao; Wang, Hong

The industrial heat supply process (HSP) is a highly nonlinear cascaded process which uses a steam valve opening as its control input, the steam flow-rate as its inner loop output and the supply water temperature as its outer loop output. The relationship between the heat exchange rate and the model parameters, such as steam density, entropy, and fouling correction factor and heat exchange efficiency are unknown and nonlinear. Moreover, these model parameters vary in line with steam pressure, ambient temperature and the residuals caused by the quality variations of the circulation water. When the steam pressure and the ambient temperaturemore » are of high values and are subjected to frequent external random disturbances, the supply water temperature and the steam flow-rate would interact with each other and fluctuate a lot. This is also true when the process exhibits unknown characteristic variations of the process dynamics caused by the unexpected changes of the heat exchange residuals. As a result, it is difficult to control the supply water temperature and the rates of changes of steam flow-rate well inside their targeted ranges. In this paper, a novel compensation signal based dual rate adaptive controller is developed by representing the unknown variations of dynamics as unmodeled dynamics. In the proposed controller design, such a compensation signal is constructed and added onto the control signal obtained from the linear deterministic model based feedback control design. Such a compensation signal aims at eliminating the unmodeled dynamics and the rate of changes of the currently sample unmodeled dynamics. A successful industrial application is carried out, where it has been shown that both the supply water temperature and the rate of the changes of the steam flow-rate can be controlled well inside their targeted ranges when the process is subjected to unknown variations of its dynamics.« less

Ventral striatal dopamine reflects behavioral and neural signatures of model-based control during sequential decision making.

PubMed

Deserno, Lorenz; Huys, Quentin J M; Boehme, Rebecca; Buchert, Ralph; Heinze, Hans-Jochen; Grace, Anthony A; Dolan, Raymond J; Heinz, Andreas; Schlagenhauf, Florian

2015-02-03

Dual system theories suggest that behavioral control is parsed between a deliberative "model-based" and a more reflexive "model-free" system. A balance of control exerted by these systems is thought to be related to dopamine neurotransmission. However, in the absence of direct measures of human dopamine, it remains unknown whether this reflects a quantitative relation with dopamine either in the striatum or other brain areas. Using a sequential decision task performed during functional magnetic resonance imaging, combined with striatal measures of dopamine using [(18)F]DOPA positron emission tomography, we show that higher presynaptic ventral striatal dopamine levels were associated with a behavioral bias toward more model-based control. Higher presynaptic dopamine in ventral striatum was associated with greater coding of model-based signatures in lateral prefrontal cortex and diminished coding of model-free prediction errors in ventral striatum. Thus, interindividual variability in ventral striatal presynaptic dopamine reflects a balance in the behavioral expression and the neural signatures of model-free and model-based control. Our data provide a novel perspective on how alterations in presynaptic dopamine levels might be accompanied by a disruption of behavioral control as observed in aging or neuropsychiatric diseases such as schizophrenia and addiction.

Special Agents Can Promote Cooperation in the Population

PubMed Central

Wang, Xin; Han, Jing; Han, Huawei

2011-01-01

Cooperation is ubiquitous in our real life but everyone would like to maximize her own profits. How does cooperation occur in the group of self-interested agents without centralized control? Furthermore, in a hostile scenario, for example, cooperation is unlikely to emerge. Is there any mechanism to promote cooperation if populations are given and play rules are not allowed to change? In this paper, numerical experiments show that complete population interaction is unfriendly to cooperation in the finite but end-unknown Repeated Prisoner's Dilemma (RPD). Then a mechanism called soft control is proposed to promote cooperation. According to the basic idea of soft control, a number of special agents are introduced to intervene in the evolution of cooperation. They comply with play rules in the original group so that they are always treated as normal agents. For our purpose, these special agents have their own strategies and share knowledge. The capability of the mechanism is studied under different settings. We find that soft control can promote cooperation and is robust to noise. Meanwhile simulation results demonstrate the applicability of the mechanism in other scenarios. Besides, the analytical proof also illustrates the effectiveness of soft control and validates simulation results. As a way of intervention in collective behaviors, soft control provides a possible direction for the study of reciprocal behaviors. PMID:22216202

Effects of Meteorological Data Quality on Snowpack Modeling

NASA Astrophysics Data System (ADS)

Havens, S.; Marks, D. G.; Robertson, M.; Hedrick, A. R.; Johnson, M.

2017-12-01

Detailed quality control of meteorological inputs is the most time-intensive component of running the distributed, physically-based iSnobal snow model, and the effect of data quality of the inputs on the model is unknown. The iSnobal model has been run operationally since WY2013, and is currently run in several basins in Idaho and California. The largest amount of user input during modeling is for the quality control of precipitation, temperature, relative humidity, solar radiation, wind speed and wind direction inputs. Precipitation inputs require detailed user input and are crucial to correctly model the snowpack mass. This research applies a range of quality control methods to meteorological input, from raw input with minimal cleaning, to complete user-applied quality control. The meteorological input cleaning generally falls into two categories. The first is global minimum/maximum and missing value correction that could be corrected and/or interpolated with automated processing. The second category is quality control for inputs that are not globally erroneous, yet are still unreasonable and generally indicate malfunctioning measurement equipment, such as temperature or relative humidity that remains constant, or does not correlate with daily trends observed at nearby stations. This research will determine how sensitive model outputs are to different levels of quality control and guide future operational applications.

Direct and indirect responses of a freshwater food web to a potent synthetic oestrogen

PubMed Central

Kidd, Karen A.; Paterson, Michael J.; Rennie, Michael D.; Podemski, Cheryl L.; Findlay, Dave L.; Blanchfield, Paul J.; Liber, Karsten

2014-01-01

Endocrine-disrupting chemicals (EDCs) in municipal effluents directly affect the sexual development and reproductive success of fishes, but indirect effects on invertebrate prey or fish predators through reduced predation or prey availability, respectively, are unknown. At the Experimental Lakes Area in northwestern Ontario, Canada, a long-term, whole-lake experiment was conducted using a before-after-control-impact design to determine both direct and indirect effects of the synthetic oestrogen used in the birth control pill, 17α-ethynyloestradiol (EE2). Algal, microbial, zooplankton and benthic invertebrate communities showed no declines in abundance during three summers of EE2 additions (5–6 ng l−1), indicating no direct toxic effects. Recruitment of fathead minnow (Pimephales promelas) failed, leading to a near-extirpation of this species both 2 years during (young-of-year, YOY) and 2 years following (adults and YOY) EE2 additions. Body condition of male lake trout (Salvelinus namaycush) and male and female white sucker (Catostomus commersonii) declined before changes in prey abundance, suggesting direct effects of EE2 on this endpoint. Evidence of indirect effects of EE2 was also observed. Increases in zooplankton, Chaoborus, and emerging insects were observed after 2 or 3 years of EE2 additions, strongly suggesting indirect effects mediated through the reduced abundance of several small-bodied fishes. Biomass of top predator lake trout declined by 23–42% during and after EE2 additions, most probably an indirect effect from the loss of its prey species, the fathead minnow and slimy sculpin (Cottus cognatus). Our results demonstrate that small-scale studies focusing solely on direct effects are likely to underestimate the true environmental impacts of oestrogens in municipal wastewaters and provide further evidence of the value of whole-ecosystem experiments for understanding indirect effects of EDCs and other aquatic stressors. PMID:25405967

Perceptions of the Benefits to Using a Secondary Admissions Process in Professional Bachelor's Athletic Training Programs

ERIC Educational Resources Information Center

Bowman, Thomas G.; Mazerolle, Stephanie M.; Dodge, Thomas M.

2016-01-01

Context: Some athletic training program (ATP) directors use direct admit, where students are admitted into the ATP directly out of high school. Other ATP directors admit students into the program after a set time period on campus through a secondary admissions process. It remains unknown why ATP directors use various admissions practices.…

Passive MIMO Radar Detection

DTIC Science & Technology

2013-09-01

investigated using recent results from random matrix theory. Equivalence is established between PMR networks without direct-path signals and passive...approach ignores a potentially useful source of information about the unknown transmit signals . This is particularly true in high-DNR scenarios, in...which the direct-path signal provides a high-quality reference that can be used for (noisy) matched filtering, as in the conventional approach. Thus

The Great Hydrometer Construction Contest!

ERIC Educational Resources Information Center

McGinnis, James Randy; Padilla, Michael J.

1991-01-01

The relationship between specific gravity, salinity, and density in brine solutions is investigated. Students construct hydrometers to reinforce concepts learned in oceanography. Background information, salt requirements for the unknowns, directions, and reproducible worksheets are included. (KR)

Adaptive Fuzzy Control Design for Stochastic Nonlinear Switched Systems With Arbitrary Switchings and Unmodeled Dynamics.

PubMed

Li, Yongming; Sui, Shuai; Tong, Shaocheng

2017-02-01

This paper deals with the problem of adaptive fuzzy output feedback control for a class of stochastic nonlinear switched systems. The controlled system in this paper possesses unmeasured states, completely unknown nonlinear system functions, unmodeled dynamics, and arbitrary switchings. A state observer which does not depend on the switching signal is constructed to tackle the unmeasured states. Fuzzy logic systems are employed to identify the completely unknown nonlinear system functions. Based on the common Lyapunov stability theory and stochastic small-gain theorem, a new robust adaptive fuzzy backstepping stabilization control strategy is developed. The stability of the closed-loop system on input-state-practically stable in probability is proved. The simulation results are given to verify the efficiency of the proposed fuzzy adaptive control scheme.

BicaudalD actively regulates microtubule motor activity in lipid droplet transport.

PubMed

Larsen, Kristoffer S; Xu, Jing; Cermelli, Silvia; Shu, Zhanyong; Gross, Steven P

2008-01-01

A great deal of sub-cellular organelle positioning, and essentially all minus-ended organelle transport, depends on cytoplasmic dynein, but how dynein's function is regulated is not well understood. BicD is established to play a critical role in mediating dynein function-loss of BicD results in improperly localized nuclei, mRNA particles, and a dispersed Golgi apparatus-however exactly what BicD's role is remains unknown. Nonetheless, it is widely believed that BicD may act to tether dynein to cargos. Here we use a combination of biophysical and biochemical studies to investigate BicD's role in lipid droplet transport during Drosophila embryogenesis. Functional loss of BicD impairs the embryo's ability to control the net direction of droplet transport; the developmentally controlled reversal in transport is eliminated. We find that minimal BicD expression (near-BicD(null)) decreases the average run length of both plus and minus end directed microtubule (MT) based transport. A point mutation affecting the BicD N-terminus has very similar effects on transport during cellularization (phase II), but in phase III (gastrulation) motion actually appears better than in the wild-type. In contrast to a simple static tethering model of BicD function, or a role only in initial dynein recruitment to the cargo, our data uncovers a new dynamic role for BicD in actively regulating transport. Lipid droplets move bi-directionally, and our investigations demonstrate that BicD plays a critical-and temporally changing-role in balancing the relative contributions of plus-end and minus-end motors to control the net direction of transport. Our results suggest that while BicD might contribute to recruitment of dynein to the cargo it is not absolutely required for such dynein localization, and it clearly contributes to regulation, helping activation/inactivation of the motors.

L1 adaptive control of uncertain gear transmission servo systems with deadzone nonlinearity.

PubMed

Zuo, Zongyu; Li, Xiao; Shi, Zhiguang

2015-09-01

This paper deals with the adaptive control problem of Gear Transmission Servo (GTS) systems in the presence of unknown deadzone nonlinearity and viscous friction. A global differential homeomorphism based on a novel differentiable deadzone model is proposed first. Since there exist both matched and unmatched state-dependent unknown nonlinearities, a full-state feedback L1 adaptive controller is constructed to achieve uniformly bounded transient response in addition to steady-state performance. Finally, simulation results are included to show the elimination of limit cycles, in addition to demonstrating the main results in this paper. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Nonlinear robust controller design for multi-robot systems with unknown payloads

NASA Technical Reports Server (NTRS)

Song, Y. D.; Anderson, J. N.; Homaifar, A.; Lai, H. Y.

1992-01-01

This work is concerned with the control problem of a multi-robot system handling a payload with unknown mass properties. Force constraints at the grasp points are considered. Robust control schemes are proposed that cope with the model uncertainty and achieve asymptotic path tracking. To deal with the force constraints, a strategy for optimally sharing the task is suggested. This strategy basically consists of two steps. The first detects the robots that need help and the second arranges that help. It is shown that the overall system is not only robust to uncertain payload parameters, but also satisfies the force constraints.

Reproductive endocrinology in chondrichthyans: the present and the future.

PubMed

Awruch, C A

2013-10-01

The class Chondrichthyes, that includes Elasmobranchii and Holocephali, is a diverse group of fish occupying a key position at the base of vertebrate evolution. Their evolutionary success is greatly attributed to their wide range of reproductive strategies controlled by different endocrine mechanics. As in other vertebrates, hormonal control of reproduction in chondrichthyans is mediated by the neuropeptide gonadotropin-releasing hormone (GnRH) that regulates the brain control of gonadal activity via a hypothalamus-pituitary-gonadal (HPG) axis. Chondrichthyans lack of a direct vascular supply from the hypothalamus to the zone of the pituitary where the gonadotropic activity resides, thus transport between these two zones likely occurs via the general circulation. In the brain of elasmobranchs, two groups of GnRH, GnRH-I and GnRH-II were identified, and the presence of two immunoreactive gonadotropins similar to the luteinising (LH) and follicle stimulating (FSH) hormones was identified in the pituitary. In holocephalans, only GnRH-II has been confirmed, and while gonadotropin activity has been found in the buccal pituitary lobe, the presence of gonadotropin receptors in the gonads remains unknowns. The diversity of reproductive strategies display by chondrichthyans makes it difficult to generalize the control of gametogenesis and steroidogenesis; however, some general patterns emerge. In both sexes, androgens and estrogens are the main steroids during gonadal growth; while progestins have maturational activity. Androgens also form the precursors for estrogen steroid production. Estrogens stimulate the hepatic synthesis of yolk and stimulate the development of different part of the reproductive tract in females. The role of other gonadal steroids may play in chondrichthyan reproduction remains largely unknown. Future work should concentrate in filling the gaps into the current knowledge of the HPG axis regulation, and the use of reproductive endocrinology as a non-lethal technique for management of chondrichthyan populations. Copyright © 2013 Elsevier Inc. All rights reserved.

Mindfulness-Meditation-Based Pain Relief Is Not Mediated by Endogenous Opioids.

PubMed

Zeidan, Fadel; Adler-Neal, Adrienne L; Wells, Rebecca E; Stagnaro, Emily; May, Lisa M; Eisenach, James C; McHaffie, John G; Coghill, Robert C

2016-03-16

Mindfulness meditation, a cognitive practice premised on sustaining nonjudgmental awareness of arising sensory events, reliably attenuates pain. Mindfulness meditation activates multiple brain regions that contain a high expression of opioid receptors. However, it is unknown whether mindfulness-meditation-based analgesia is mediated by endogenous opioids. The present double-blind, randomized study examined behavioral pain responses in healthy human volunteers during mindfulness meditation and a nonmanipulation control condition in response to noxious heat and intravenous administration of the opioid antagonist naloxone (0.15 mg/kg bolus + 0.1 mg/kg/h infusion) or saline placebo. Meditation during saline infusion significantly reduced pain intensity and unpleasantness ratings when compared to the control + saline group. However, naloxone infusion failed to reverse meditation-induced analgesia. There were no significant differences in pain intensity or pain unpleasantness reductions between the meditation + naloxone and the meditation + saline groups. Furthermore, mindfulness meditation during naloxone produced significantly greater reductions in pain intensity and unpleasantness than the control groups. These findings demonstrate that mindfulness meditation does not rely on endogenous opioidergic mechanisms to reduce pain. Endogenous opioids have been repeatedly shown to be involved in the cognitive inhibition of pain. Mindfulness meditation, a practice premised on directing nonjudgmental attention to arising sensory events, reduces pain by engaging mechanisms supporting the cognitive control of pain. However, it remains unknown if mindfulness-meditation-based analgesia is mediated by opioids, an important consideration for using meditation to treat chronic pain. To address this question, the present study examined pain reports during meditation in response to noxious heat and administration of the opioid antagonist naloxone and placebo saline. The results demonstrate that meditation-based pain relief does not require endogenous opioids. Therefore, the treatment of chronic pain may be more effective with meditation due to a lack of cross-tolerance with opiate-based medications. Copyright © 2016 the authors 0270-6474/16/363391-07$15.00/0.

Mindfulness-Meditation-Based Pain Relief Is Not Mediated by Endogenous Opioids

PubMed Central

Adler-Neal, Adrienne L.; Wells, Rebecca E.; Stagnaro, Emily; May, Lisa M.; Eisenach, James C.; McHaffie, John G.; Coghill, Robert C.

2016-01-01

Mindfulness meditation, a cognitive practice premised on sustaining nonjudgmental awareness of arising sensory events, reliably attenuates pain. Mindfulness meditation activates multiple brain regions that contain a high expression of opioid receptors. However, it is unknown whether mindfulness-meditation-based analgesia is mediated by endogenous opioids. The present double-blind, randomized study examined behavioral pain responses in healthy human volunteers during mindfulness meditation and a nonmanipulation control condition in response to noxious heat and intravenous administration of the opioid antagonist naloxone (0.15 mg/kg bolus + 0.1 mg/kg/h infusion) or saline placebo. Meditation during saline infusion significantly reduced pain intensity and unpleasantness ratings when compared to the control + saline group. However, naloxone infusion failed to reverse meditation-induced analgesia. There were no significant differences in pain intensity or pain unpleasantness reductions between the meditation + naloxone and the meditation + saline groups. Furthermore, mindfulness meditation during naloxone produced significantly greater reductions in pain intensity and unpleasantness than the control groups. These findings demonstrate that mindfulness meditation does not rely on endogenous opioidergic mechanisms to reduce pain. SIGNIFICANCE STATEMENT Endogenous opioids have been repeatedly shown to be involved in the cognitive inhibition of pain. Mindfulness meditation, a practice premised on directing nonjudgmental attention to arising sensory events, reduces pain by engaging mechanisms supporting the cognitive control of pain. However, it remains unknown if mindfulness-meditation-based analgesia is mediated by opioids, an important consideration for using meditation to treat chronic pain. To address this question, the present study examined pain reports during meditation in response to noxious heat and administration of the opioid antagonist naloxone and placebo saline. The results demonstrate that meditation-based pain relief does not require endogenous opioids. Therefore, the treatment of chronic pain may be more effective with meditation due to a lack of cross-tolerance with opiate-based medications. PMID:26985045

Controlled teleportation with the control of two groups of agents via entanglement

NASA Astrophysics Data System (ADS)

He, Xiao-Ling; Liu, Man; Yang, Chui-Ping

2015-03-01

We present a way for implementing controlled teleportation of an arbitrary unknown pure state of a qutrit with the control of two groups of agents via entanglement. In our proposal, the sender can successfully teleport the qutrit state to a distant receiver with the help of all agents. However, if one agent in each group does not cooperate, the receiver cannot gain any information (including amplitude information or phase information or both) about the qutrit state to be teleported. Since a qubit is a special case of a qutrit when the state lies in a fixed two-dimensional subspace of the qutrit, the present proposal can be also applied in the implementation of controlled teleportation of an arbitrary unknown pure state of a qubit with many control agents in two groups. We note that our proposal is the first one to use two groups of agents to achieve controlled teleportation.

The Roles of Feedback and Feedforward as Humans Learn to Control Unknown Dynamic Systems.

PubMed

Zhang, Xingye; Wang, Shaoqian; Hoagg, Jesse B; Seigler, T Michael

2018-02-01

We present results from an experiment in which human subjects interact with an unknown dynamic system 40 times during a two-week period. During each interaction, subjects are asked to perform a command-following (i.e., pursuit tracking) task. Each subject's performance at that task improves from the first trial to the last trial. For each trial, we use subsystem identification to estimate each subject's feedforward (or anticipatory) control, feedback (or reactive) control, and feedback time delay. Over the 40 trials, the magnitudes of the identified feedback controllers and the identified feedback time delays do not change significantly. In contrast, the identified feedforward controllers do change significantly. By the last trial, the average identified feedforward controller approximates the inverse of the dynamic system. This observation provides evidence that a fundamental component of human learning is updating the anticipatory control until it models the inverse dynamics.

Half-blind remote sensing image restoration with partly unknown degradation

NASA Astrophysics Data System (ADS)

Xie, Meihua; Yan, Fengxia

2017-01-01

The problem of image restoration has been extensively studied for its practical importance and theoretical interest. This paper mainly discusses the problem of image restoration with partly unknown kernel. In this model, the degraded kernel function is known but its parameters are unknown. With this model, we should estimate the parameters in Gaussian kernel and the real image simultaneity. For this new problem, a total variation restoration model is put out and an intersect direction iteration algorithm is designed. Peak Signal to Noise Ratio (PSNR) and Structural Similarity Index Measurement (SSIM) are used to measure the performance of the method. Numerical results show that we can estimate the parameters in kernel accurately, and the new method has both much higher PSNR and much higher SSIM than the expectation maximization (EM) method in many cases. In addition, the accuracy of estimation is not sensitive to noise. Furthermore, even though the support of the kernel is unknown, we can also use this method to get accurate estimation.

Adaptive control of stochastic linear systems with unknown parameters. M.S. Thesis

NASA Technical Reports Server (NTRS)

Ku, R. T.

1972-01-01

The problem of optimal control of linear discrete-time stochastic dynamical system with unknown and, possibly, stochastically varying parameters is considered on the basis of noisy measurements. It is desired to minimize the expected value of a quadratic cost functional. Since the simultaneous estimation of the state and plant parameters is a nonlinear filtering problem, the extended Kalman filter algorithm is used. Several qualitative and asymptotic properties of the open loop feedback optimal control and the enforced separation scheme are discussed. Simulation results via Monte Carlo method show that, in terms of the performance measure, for stable systems the open loop feedback optimal control system is slightly better than the enforced separation scheme, while for unstable systems the latter scheme is far better.

Oxidation of F-actin controls the terminal steps of cytokinesis

PubMed Central

Frémont, Stéphane; Hammich, Hussein; Bai, Jian; Wioland, Hugo; Klinkert, Kerstin; Rocancourt, Murielle; Kikuti, Carlos; Stroebel, David; Romet-Lemonne, Guillaume; Pylypenko, Olena; Houdusse, Anne; Echard, Arnaud

2017-01-01

Cytokinetic abscission, the terminal step of cell division, crucially depends on the local constriction of ESCRT-III helices after cytoskeleton disassembly. While the microtubules of the intercellular bridge are cut by the ESCRT-associated enzyme Spastin, the mechanism that clears F-actin at the abscission site is unknown. Here we show that oxidation-mediated depolymerization of actin by the redox enzyme MICAL1 is key for ESCRT-III recruitment and successful abscission. MICAL1 is recruited to the abscission site by the Rab35 GTPase through a direct interaction with a flat three-helix domain found in MICAL1 C terminus. Mechanistically, in vitro assays on single actin filaments demonstrate that MICAL1 is activated by Rab35. Moreover, in our experimental conditions, MICAL1 does not act as a severing enzyme, as initially thought, but instead induces F-actin depolymerization from both ends. Our work reveals an unexpected role for oxidoreduction in triggering local actin depolymerization to control a fundamental step of cell division. PMID:28230050

Flavin-mediated dual oxidation controls an enzymatic Favorskii-type rearrangement

PubMed Central

Louie, Gordon; Noel, Joseph P.; Baran, Phil S.; Palfey, Bruce; Moore, Bradley S.

2013-01-01

Flavoproteins catalyze a diversity of fundamental redox reactions and are one of the most studied enzyme families1,2. As monooxygenases, they are universally thought to control oxygenation by means of a peroxyflavin species that transfers a single atom of molecular oxygen to an organic substrate1,3,4. Here we report that the bacterial flavoenzyme EncM5,6 catalyzes the peroxyflavin-independent oxygenation-dehydrogenation dual oxidation of a highly reactive poly(β-carbonyl). The crystal structure of EncM with bound substrate mimics coupled with isotope labeling studies reveal previously unknown flavin redox biochemistry. We show that EncM maintains an unanticipated stable flavin oxygenating species, proposed to be a flavin-N5-oxide, to promote substrate oxidation and trigger a rare Favorskii-type rearrangement that is central to the biosynthesis of the antibiotic enterocin. This work provides new insight into the fine-tuning of the flavin cofactor in offsetting the innate reactivity of a polyketide substrate to direct its efficient electrocyclization. PMID:24162851

Subcellular trafficking of FGF controls tracheal invasion of Drosophila flight muscle

PubMed Central

Peterson, Soren J.; Krasnow, Mark A.

2015-01-01

SUMMARY To meet the extreme oxygen demand of insect flight muscle, tracheal (respiratory) tubes ramify not only on its surface, as in other tissues, but also within T-tubules and ultimately surrounding every mitochondrion. Although this remarkable physiological specialization has long been recognized, its cellular and molecular basis is unknown. Here we show that Drosophila tracheoles invade flight muscle T-tubules through transient surface openings. Like other tracheal branching events, invasion requires the Branchless FGF pathway. However, localization of the FGF chemoattractant changes from all muscle membranes to T-tubules as invasion begins. Core regulators of epithelial basolateral membrane identity localize to T-tubules, and knockdown of AP-1γ, required for basolateral trafficking, redirects FGF from T-tubules to surface, increasing tracheal surface ramification and preventing invasion. We propose that tracheal invasion is controlled by an AP-1-dependent switch in FGF trafficking. Thus, subcellular targeting of a chemoattractant can direct outgrowth to specific domains including inside the cell. PMID:25557078

Behavioural and neurobiological implications of linear and non-linear features in larynx phonations of horseshoe bats

PubMed Central

Kobayasi, Kohta I.; Hage, Steffen R.; Berquist, Sean; Feng, Jiang; Zhang, Shuyi; Metzner, Walter

2012-01-01

Mammalian vocalizations exhibit large variations in their spectrotemporal features, although it is still largely unknown which result from intrinsic biomechanical properties of the larynx and which are under direct neuromuscular control. Here we show that mere changes in laryngeal air flow yield several non-linear effects on sound production, in an isolated larynx preparation from horseshoe bats. Most notably, there are sudden jumps between two frequency bands used for either echolocation or communication in natural vocalizations. These jumps resemble changes in “registers” as in yodelling. In contrast, simulated contractions of the main larynx muscle produce linear frequency changes, but are limited to echolocation or communication frequencies. Only by combining non-linear and linear properties can this larynx therefore produce sounds covering the entire frequency range of natural calls. This may give behavioural meaning to yodelling-like vocal behaviour and reshape our thinking about how the brain controls the multitude of spectral vocal features in mammals. PMID:23149729

Next-Generation Sequencing for Infectious Disease Diagnosis and Management: A Report of the Association for Molecular Pathology.

PubMed

Lefterova, Martina I; Suarez, Carlos J; Banaei, Niaz; Pinsky, Benjamin A

2015-11-01

Next-generation sequencing (NGS) technologies are increasingly being used for diagnosis and monitoring of infectious diseases. Herein, we review the application of NGS in clinical microbiology, focusing on genotypic resistance testing, direct detection of unknown disease-associated pathogens in clinical specimens, investigation of microbial population diversity in the human host, and strain typing. We have organized the review into three main sections: i) applications in clinical virology, ii) applications in clinical bacteriology, mycobacteriology, and mycology, and iii) validation, quality control, and maintenance of proficiency. Although NGS holds enormous promise for clinical infectious disease testing, many challenges remain, including automation, standardizing technical protocols and bioinformatics pipelines, improving reference databases, establishing proficiency testing and quality control measures, and reducing cost and turnaround time, all of which would be necessary for widespread adoption of NGS in clinical microbiology laboratories. Copyright © 2015 American Society for Investigative Pathology and the Association for Molecular Pathology. Published by Elsevier Inc. All rights reserved.

Subcellular trafficking of FGF controls tracheal invasion of Drosophila flight muscle.

PubMed

Peterson, Soren J; Krasnow, Mark A

2015-01-15

To meet the extreme oxygen demand of insect flight muscle, tracheal (respiratory) tubes ramify not only on its surface, as in other tissues, but also within T-tubules and ultimately surrounding every mitochondrion. Although this remarkable physiological specialization has long been recognized, its cellular and molecular basis is unknown. Here, we show that Drosophila tracheoles invade flight muscle T-tubules through transient surface openings. Like other tracheal branching events, invasion requires the Branchless FGF pathway. However, localization of the FGF chemoattractant changes from all muscle membranes to T-tubules as invasion begins. Core regulators of epithelial basolateral membrane identity localize to T-tubules, and knockdown of AP-1γ, required for basolateral trafficking, redirects FGF from T-tubules to surface, increasing tracheal surface ramification and preventing invasion. We propose that tracheal invasion is controlled by an AP-1-dependent switch in FGF trafficking. Thus, subcellular targeting of a chemoattractant can direct outgrowth to specific domains, including inside the cell. Copyright © 2015 Elsevier Inc. All rights reserved.

Filopodial dynamics and growth cone stabilization in Drosophila visual circuit development

PubMed Central

Özel, Mehmet Neset; Langen, Marion; Hassan, Bassem A; Hiesinger, P Robin

2015-01-01

Filopodial dynamics are thought to control growth cone guidance, but the types and roles of growth cone dynamics underlying neural circuit assembly in a living brain are largely unknown. To address this issue, we have developed long-term, continuous, fast and high-resolution imaging of growth cone dynamics from axon growth to synapse formation in cultured Drosophila brains. Using R7 photoreceptor neurons as a model we show that >90% of the growth cone filopodia exhibit fast, stochastic dynamics that persist despite ongoing stepwise layer formation. Correspondingly, R7 growth cones stabilize early and change their final position by passive dislocation. N-Cadherin controls both fast filopodial dynamics and growth cone stabilization. Surprisingly, loss of N-Cadherin causes no primary targeting defects, but destabilizes R7 growth cones to jump between correct and incorrect layers. Hence, growth cone dynamics can influence wiring specificity without a direct role in target recognition and implement simple rules during circuit assembly. DOI: http://dx.doi.org/10.7554/eLife.10721.001 PMID:26512889

Spline Trajectory Algorithm Development: Bezier Curve Control Point Generation for UAVs

NASA Technical Reports Server (NTRS)

Howell, Lauren R.; Allen, B. Danette

2016-01-01

A greater need for sophisticated autonomous piloting systems has risen in direct correlation with the ubiquity of Unmanned Aerial Vehicle (UAV) technology. Whether surveying unknown or unexplored areas of the world, collecting scientific data from regions in which humans are typically incapable of entering, locating lost or wanted persons, or delivering emergency supplies, an unmanned vehicle moving in close proximity to people and other vehicles, should fly smoothly and predictably. The mathematical application of spline interpolation can play an important role in autopilots' on-board trajectory planning. Spline interpolation allows for the connection of Three-Dimensional Euclidean Space coordinates through a continuous set of smooth curves. This paper explores the motivation, application, and methodology used to compute the spline control points, which shape the curves in such a way that the autopilot trajectory is able to meet vehicle-dynamics limitations. The spline algorithms developed used to generate these curves supply autopilots with the information necessary to compute vehicle paths through a set of coordinate waypoints.

Prefrontal Parvalbumin Neurons in Control of Attention

PubMed Central

Kim, Hoseok; Ährlund-Richter, Sofie; Wang, Xinming; Deisseroth, Karl; Carlén, Marie

2016-01-01

Summary While signatures of attention have been extensively studied in sensory systems, the neural sources and computations responsible for top-down control of attention are largely unknown. Using chronic recordings in mice, we found that fast-spiking parvalbumin (FS-PV) interneurons in medial prefrontal cortex (mPFC) uniformly show increased and sustained firing during goal-driven attentional processing, correlating to the level of attention. Elevated activity of FS-PV neurons on the timescale of seconds predicted successful execution of behavior. Successful allocation of attention was characterized by strong synchronization of FS-PV neurons, increased gamma oscillations, and phase locking of pyramidal firing. Phase-locked pyramidal neurons showed gamma-phase-dependent rate modulation during successful attentional processing. Optogenetic silencing of FS-PV neurons deteriorated attentional processing, while optogenetic synchronization of FS-PV neurons at gamma frequencies had pro-cognitive effects and improved goal-directed behavior. FS-PV neurons thus act as a functional unit coordinating the activity in the local mPFC circuit during goal-driven attentional processing. PMID:26771492

Obstetric complications and mild to moderate intellectual disability.

PubMed

Sussmann, Jessika E; McIntosh, Andrew M; Lawrie, Stephen M; Johnstone, Eve C

2009-03-01

Mild to moderate intellectual disability affects 2.5% of the general population and is associated with an increased risk of several psychiatric disorders. Most cases are of unknown aetiology although genetic factors have an important role. To investigate the role of obstetric and neonatal complications in the aetiology of mild to moderate intellectual disability. Obstetric and neonatal complications recorded at the time of pregnancy and delivery were compared between participants with mild to moderate intellectual disability, age-matched siblings and unrelated controls using logistic regression. Admission to a special care baby unit and not being breastfed on discharge were more common in people with mild to moderate intellectual disability. Not being breastfed on discharge was also more common in those with intellectual disability than unaffected siblings. Foetal distress was more common among controls than among those with mild to moderate intellectual disability. Admission to a special care baby unit and not being breastfed on discharge may be related to the aetiology of intellectual disability, although the direction of this association is unclear.

Cell cycle constraints on capsulation and bacteriophage susceptibility.

PubMed

Ardissone, Silvia; Fumeaux, Coralie; Bergé, Matthieu; Beaussart, Audrey; Théraulaz, Laurence; Radhakrishnan, Sunish Kumar; Dufrêne, Yves F; Viollier, Patrick H

2014-11-25

Despite the crucial role of bacterial capsules in pathogenesis, it is still unknown if systemic cues such as the cell cycle can control capsule biogenesis. In this study, we show that the capsule of the synchronizable model bacterium Caulobacter crescentus is cell cycle regulated and we unearth a bacterial transglutaminase homolog, HvyA, as restriction factor that prevents capsulation in G1-phase cells. This capsule protects cells from infection by a generalized transducing Caulobacter phage (φCr30), and the loss of HvyA confers insensitivity towards φCr30. Control of capsulation during the cell cycle could serve as a simple means to prevent steric hindrance of flagellar motility or to ensure that phage-mediated genetic exchange happens before the onset of DNA replication. Moreover, the multi-layered regulatory circuitry directing HvyA expression to G1-phase is conserved during evolution, and HvyA orthologues from related Sinorhizobia can prevent capsulation in Caulobacter, indicating that alpha-proteobacteria have retained HvyA activity.

Name recognition in autism: EEG evidence of altered patterns of brain activity and connectivity.

PubMed

Nowicka, Anna; Cygan, Hanna B; Tacikowski, Paweł; Ostaszewski, Paweł; Kuś, Rafał

2016-01-01

Impaired orienting to social stimuli is one of the core early symptoms of autism spectrum disorder (ASD). However, in contrast to faces, name processing has rarely been studied in individuals with ASD. Here, we investigated brain activity and functional connectivity associated with recognition of names in the high-functioning ASD group and in the control group. EEG was recorded in 15 young males with ASD and 15 matched one-to-one control individuals. EEG data were analyzed with the event-related potential (ERP), event-related desynchronization and event-related synchronization (ERD/S), as well as coherence and direct transfer function (DTF) methods. Four categories of names were presented visually: one's own, close-other's, famous, and unknown. Differences between the ASD and control groups were found for ERP, coherence, and DTF. In individuals with ASD, P300 (a positive ERP component) to own-name and to a close-other's name were similar whereas in control participants, P300 to own-name was enhanced when compared to all other names. Analysis of coherence and DTF revealed disruption of fronto-posterior task-related connectivity in individuals with ASD within the beta range frequencies. Moreover, DTF indicated the directionality of those impaired connections-they were going from parieto-occipital to frontal regions. DTF also showed inter-group differences in short-range connectivity: weaker connections within the frontal region and stronger connections within the occipital region in the ASD group in comparison to the control group. Our findings suggest a lack of the self-preference effect and impaired functioning of the attentional network during recognition of visually presented names in individuals with ASD.

Molecular Analysis of Sarcoidosis Granulomas Reveals Antimicrobial Targets

PubMed Central

Celada, Lindsay J.; Polosukhin, Vasiliy V.; Atkinson, James B.; Drake, Wonder P.

2016-01-01

Sarcoidosis is a granulomatous disease of unknown cause. Prior molecular and immunologic studies have confirmed the presence of mycobacterial virulence factors, such as catalase peroxidase and superoxide dismutase A, within sarcoidosis granulomas. Molecular analysis of granulomas can identify targets of known antibiotics classes. Currently, major antibiotics are directed against DNA synthesis, protein synthesis, and cell wall formation. We conducted molecular analysis of 40 sarcoidosis diagnostic specimens and compared them with 33 disease control specimens for the presence of mycobacterial genes that encode antibiotic targets. We assessed for genes involved in DNA synthesis (DNA gyrase A [gyrA] and DNA gyrase B), protein synthesis (RNA polymerase subunit β), cell wall synthesis (embCAB operon and enoyl reductase), and catalase peroxidase. Immunohistochemical analysis was conducted to investigate the locale of mycobacterial genes such as gyrA within 12 sarcoidosis specimens and 12 disease controls. Mycobacterial DNA was detected in 33 of 39 sarcoidosis specimens by quantitative real-time polymerase chain reaction compared with 2 of 30 disease control specimens (P < 0.001, two-tailed Fisher’s test). Twenty of 39 were positive for three or more mycobacterial genes, compared with 1 of 30 control specimens (P < 0.001, two-tailed Fisher’s test). Immunohistochemistry analysis localized mycobacterial gyrA nucleic acids to sites of granuloma formation in 9 of 12 sarcoidosis specimens compared with 1 of 12 disease controls (P < 0.01). Microbial genes encoding enzymes that can be targeted by currently available antimycobacterial antibiotics are present in sarcoidosis specimens and localize to sites of granulomatous inflammation. Use of antimicrobials directed against target enzymes may be an innovative treatment alternative. PMID:26807608

Fission meter and neutron detection using poisson distribution comparison

DOEpatents

Rowland, Mark S; Snyderman, Neal J

2014-11-18

A neutron detector system and method for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. Comparison of the observed neutron count distribution with a Poisson distribution is performed to distinguish fissile material from non-fissile material.

Irreversible temperature gating in trpv1 sheds light on channel activation

PubMed Central

Sánchez-Moreno, Ana; Guevara-Hernández, Eduardo; Contreras-Cervera, Ricardo; Rangel-Yescas, Gisela; Ladrón-de-Guevara, Ernesto; Rosenbaum, Tamara

2018-01-01

Temperature-activated TRP channels or thermoTRPs are among the only proteins that can directly convert temperature changes into changes in channel open probability. In spite of a wealth of functional and structural information, the mechanism of temperature activation remains unknown. We have carefully characterized the repeated activation of TRPV1 by thermal stimuli and discovered a previously unknown inactivation process, which is irreversible. We propose that this form of gating in TRPV1 channels is a consequence of the heat absorption process that leads to channel opening. PMID:29869983

Comparison of the efficacy and cost effectiveness of pre-emptive therapy as directed by CMV antigenemia and prophylaxis with ganciclovir in lung transplant recipients.

PubMed

Kelly, J; Hurley, D; Raghu, G

2000-04-01

CMV disease remains a major complication of lung transplantation and attempts to prevent it have met with marginal success. In a previous study we documented that universal prophylaxis did not prevent CMV disease but merely delayed it, and was very costly. We compared the efficacy and cost of pre-emptive therapy with ganciclovir, guided by CMV antigenemia, to that of historic controls that received universal prophylaxis with ganciclovir. CMV antigenemia assay was done routinely and pre-emptive therapy was initiated if greater than 25 CMV positive cells per 100,000 polymorphonuclear cells were found. Nineteen patients were enrolled; 6 of of whom received 12 courses of pre-emptive therapy. The incidence of CMV disease was 26% compared to 38% for the historical controls (p = 0.51). None of the patients that received pre-emptive therapy developed CMV disease following that therapy. Antigenemia failed to predict disease in 5 patients that developed it, and thus it is unknown if pre-emptive therapy could have prevented it. There was no mortality in either the study patients or historic controls directly related to CMV. The net savings with pre-emptive therapy was $2569 per patient. We conclude that pre-emptive therapy with ganciclovir is as safe and effective as universal prophylaxis in preventing CMV disease in lung transplant recipients, and is less expensive. The appropriate surveillance technique and timing remain to be determine to optimize the efficacy of pre-emptive therapy.

Is hand hygiene before putting on nonsterile gloves in the intensive care unit a waste of health care worker time?--a randomized controlled trial.

PubMed

Rock, Clare; Harris, Anthony D; Reich, Nicholas G; Johnson, J Kristie; Thom, Kerri A

2013-11-01

Hand hygiene (HH) is recognized as a basic effective measure in prevention of nosocomial infections. However, the importance of HH before donning nonsterile gloves is unknown, and few published studies address this issue. Despite the lack of evidence, the World Health Organization and other leading bodies recommend this practice. The aim of this study was to assess the utility of HH before donning nonsterile gloves prior to patient contact. A prospective, randomized, controlled trial of health care workers entering Contact Isolation rooms in intensive care units was performed. Baseline finger and palm prints were made from dominant hands onto agar plates. Health care workers were then randomized to directly don nonsterile gloves or perform HH and then don nonsterile gloves. Postgloving finger and palm prints were then made from the gloved hands. Plates were incubated and colony-forming units (CFU) of bacteria were counted. Total bacterial colony counts of gloved hands did not differ between the 2 groups (6.9 vs 8.1 CFU, respectively, P = .52). Staphylococcus aureus was identified from gloves (once in "hand hygiene prior to gloving" group, twice in "direct gloving" group). All other organisms were expected commensal flora. HH before donning nonsterile gloves does not decrease already low bacterial counts on gloves. The utility of HH before donning nonsterile gloves may be unnecessary. Copyright © 2013 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Mosby, Inc. All rights reserved.

Type IV pilins regulate their own expression via direct intramembrane interactions with the sensor kinase PilS.

PubMed

Kilmury, Sara L N; Burrows, Lori L

2016-05-24

Type IV pili are important virulence factors for many pathogens, including Pseudomonas aeruginosa Transcription of the major pilin gene-pilA-is controlled by the PilS-PilR two-component system in response to unknown signals. The absence of a periplasmic sensing domain suggested that PilS may sense an intramembrane signal, possibly PilA. We suggest that direct interactions between PilA and PilS in the inner membrane reduce pilA transcription when PilA levels are high. Overexpression in trans of PilA proteins with diverse and/or truncated C termini decreased native pilA transcription, suggesting that the highly conserved N terminus of PilA was the regulatory signal. Point mutations in PilA or PilS that disrupted their interaction prevented autoregulation of pilA transcription. A subset of PilA point mutants retained the ability to interact with PilS but could no longer decrease pilA transcription, suggesting that interaction between the pilin and sensor kinase is necessary but not sufficient for pilA autoregulation. Furthermore, PilS's phosphatase motif was required for the autoregulation of pilA transcription, suggesting that under conditions where PilA is abundant, the PilA-PilS interaction promotes PilR dephosphorylation and thus down-regulation of further pilA transcription. These data reveal a clever bacterial inventory control strategy in which the major subunit of an important P. aeruginosa virulence factor controls its own expression.

Alterations in metabolic pathways and networks in Alzheimer's disease

PubMed Central

Kaddurah-Daouk, R; Zhu, H; Sharma, S; Bogdanov, M; Rozen, S G; Matson, W; Oki, N O; Motsinger-Reif, A A; Churchill, E; Lei, Z; Appleby, D; Kling, M A; Trojanowski, J Q; Doraiswamy, P M; Arnold, S E

2013-01-01

The pathogenic mechanisms of Alzheimer's disease (AD) remain largely unknown and clinical trials have not demonstrated significant benefit. Biochemical characterization of AD and its prodromal phase may provide new diagnostic and therapeutic insights. We used targeted metabolomics platform to profile cerebrospinal fluid (CSF) from AD (n=40), mild cognitive impairment (MCI, n=36) and control (n=38) subjects; univariate and multivariate analyses to define between-group differences; and partial least square-discriminant analysis models to classify diagnostic groups using CSF metabolomic profiles. A partial correlation network was built to link metabolic markers, protein markers and disease severity. AD subjects had elevated methionine (MET), 5-hydroxyindoleacetic acid (5-HIAA), vanillylmandelic acid, xanthosine and glutathione versus controls. MCI subjects had elevated 5-HIAA, MET, hypoxanthine and other metabolites versus controls. Metabolite ratios revealed changes within tryptophan, MET and purine pathways. Initial pathway analyses identified steps in several pathways that appear altered in AD and MCI. A partial correlation network showed total tau most directly related to norepinephrine and purine pathways; amyloid-β (Ab42) was related directly to an unidentified metabolite and indirectly to 5-HIAA and MET. These findings indicate that MCI and AD are associated with an overlapping pattern of perturbations in tryptophan, tyrosine, MET and purine pathways, and suggest that profound biochemical alterations are linked to abnormal Ab42 and tau metabolism. Metabolomics provides powerful tools to map interlinked biochemical pathway perturbations and study AD as a disease of network failure. PMID:23571809

Control of alternative splicing by forskolin through hnRNP K during neuronal differentiation.

PubMed

Cao, Wenguang; Razanau, Aleh; Feng, Dairong; Lobo, Vincent G; Xie, Jiuyong

2012-09-01

The molecular basis of cell signal-regulated alternative splicing at the 3' splice site remains largely unknown. We isolated a protein kinase A-responsive ribonucleic acid (RNA) element from a 3' splice site of the synaptosomal-associated protein 25 (Snap25) gene for forskolin-inhibited splicing during neuronal differentiation of rat pheochromocytoma PC12 cells. The element binds specifically to heterogeneous nuclear ribonucleo protein (hnRNP) K in a phosphatase-sensitive way, which directly competes with the U2 auxiliary factor U2AF65, an essential component of early spliceosomes. Transcripts with similarly localized hnRNP K target motifs upstream of alternative exons are enriched in genes often associated with neurological diseases. We show that such motifs upstream of the Runx1 exon 6 also bind hnRNP K, and importantly, hnRNP K is required for forskolin-induced repression of the exon. Interestingly, this exon encodes the peptide domain that determines the switch of the transcriptional repressor/activator activity of Runx1, a change known to be critical in specifying neuron lineages. Consistent with an important role of the target genes in neurons, knocking down hnRNP K severely disrupts forskolin-induced neurite growth. Thus, through hnRNP K, the neuronal differentiation stimulus forskolin targets a critical 3' splice site component of the splicing machinery to control alternative splicing of crucial genes. This also provides a regulated direct competitor of U2AF65 for cell signal control of 3' splice site usage.

Alterations in metabolic pathways and networks in Alzheimer's disease.

PubMed

Kaddurah-Daouk, R; Zhu, H; Sharma, S; Bogdanov, M; Rozen, S G; Matson, W; Oki, N O; Motsinger-Reif, A A; Churchill, E; Lei, Z; Appleby, D; Kling, M A; Trojanowski, J Q; Doraiswamy, P M; Arnold, S E

2013-04-09

The pathogenic mechanisms of Alzheimer's disease (AD) remain largely unknown and clinical trials have not demonstrated significant benefit. Biochemical characterization of AD and its prodromal phase may provide new diagnostic and therapeutic insights. We used targeted metabolomics platform to profile cerebrospinal fluid (CSF) from AD (n=40), mild cognitive impairment (MCI, n=36) and control (n=38) subjects; univariate and multivariate analyses to define between-group differences; and partial least square-discriminant analysis models to classify diagnostic groups using CSF metabolomic profiles. A partial correlation network was built to link metabolic markers, protein markers and disease severity. AD subjects had elevated methionine (MET), 5-hydroxyindoleacetic acid (5-HIAA), vanillylmandelic acid, xanthosine and glutathione versus controls. MCI subjects had elevated 5-HIAA, MET, hypoxanthine and other metabolites versus controls. Metabolite ratios revealed changes within tryptophan, MET and purine pathways. Initial pathway analyses identified steps in several pathways that appear altered in AD and MCI. A partial correlation network showed total tau most directly related to norepinephrine and purine pathways; amyloid-β (Ab42) was related directly to an unidentified metabolite and indirectly to 5-HIAA and MET. These findings indicate that MCI and AD are associated with an overlapping pattern of perturbations in tryptophan, tyrosine, MET and purine pathways, and suggest that profound biochemical alterations are linked to abnormal Ab42 and tau metabolism. Metabolomics provides powerful tools to map interlinked biochemical pathway perturbations and study AD as a disease of network failure.

Transport of fluorobenzoate tracers in a vegetated hydrologic control volume: 1. Experimental results

NASA Astrophysics Data System (ADS)

Queloz, Pierre; Bertuzzo, Enrico; Carraro, Luca; Botter, Gianluca; Miglietta, Franco; Rao, P. S. C.; Rinaldo, Andrea

2015-04-01

This paper reports about the experimental evidence collected on the transport of five fluorobenzoate tracers injected under controlled conditions in a vegetated hydrologic volume, a large lysimeter (fitted with load cells, sampling ports, and an underground chamber) where two willows prompting large evapotranspiration fluxes had been grown. The relevance of the study lies in the direct and indirect measures of the ways in which hydrologic fluxes, in this case, evapotranspiration from the upper surface and discharge from the bottom drainage, sample water and solutes in storage at different times under variable hydrologic forcings. Methods involve the accurate control of hydrologic inputs and outputs and a large number of suitable chemical analyses of water samples in discharge waters. Mass extraction from biomass has also been performed ex post. The results of the 2 year long experiment established that our initial premises on the tracers' behavior, known to be sorption-free under saturated conditions which we verified in column leaching tests, were unsuitable as large differences in mass recovery appeared. Issues on reactivity thus arose and were addressed in the paper, in this case attributed to microbial degradation and solute plant uptake. Our results suggest previously unknown features of fluorobenzoate compounds as hydrologic tracers, potentially interesting for catchment studies owing to their suitability for distinguishable multiple injections, and an outlook on direct experimental closures of mass balance in hydrologic transport volumes involving fluxes that are likely to sample differently stored water and solutes.

Downwash of airplane winds

NASA Technical Reports Server (NTRS)

Munk, Max; Cario, Gunther

1923-01-01

The data for the calculation of the air forces acting on the elevators, obtained from previous model experiments are not immediately applicable in practice, as the angle at which the control surfaces meet the air stream is, in general, still unknown. The air stream, when it reaches the elevator has already been deflected by the wings and although the velocity imparted to the air current by the wings is of negligible amount compared with the speed of flight, the air behind the wings has been deflected downwards, so that the elevators work in an airstream which is inclined in a downward direction. The angle at which the air stream meets the elevator surface is, therefore, different from, and, with the usual arrangement of elevators, less than the angle made by the elevator surfaces with the line of flight.

The important role of water in growth of monolayer transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Kastl, Christoph; Chen, Christopher T.; Kuykendall, Tevye; Shevitski, Brian; Darlington, Thomas P.; Borys, Nicholas J.; Krayev, Andrey; Schuck, P. James; Aloni, Shaul; Schwartzberg, Adam M.

2017-06-01

2D transition metal dichalcogenides (TMDs) are commonly grown by chemical vapor deposition using transition metal oxides as solid precursors. Despite the widespread use of this technique, challenges in reproducibility, coverage, and material quality are pervasive, suggestive of unknown and uncontrolled process parameters. In this communication, we demonstrate the impact of water vapor on this growth process. Our results show a direct correlation between gas phase water content and the morphology of TMD films. In particular, we show that the presence of water enhances volatilization, and therefore the vapor transport of tungsten and molybdenum oxide. Surprisingly, we find that water not only plays an important role in volatilization but is also compatible with TMD growth. In fact, carefully controlled humidity can consistently produce high quality, luminescent materials.

Dimensions of Temperament and Depressive Symptoms: Replicating a Three-Way Interaction

PubMed Central

Vasey, Michael W.; Harbaugh, Casaundra N.; Lonigan, Chistopher J.; Phillips, Beth M.; Hankin, Benjamin L.; Willem, Lore; Bijttebier, Patricia

2014-01-01

High negative emotionality (NE), low positive emotionality (PE), and low self-regulatory capacity (i.e., effortful control or EC) are related to depressive symptoms and furthermore, may moderate one another’s relations to such symptoms. Indeed, preliminary evidence suggests they may operate in a three-way interaction (Dinovo & Vasey, 2011), but the replicability of that finding remains unknown. Therefore, we tested this NExPExEC interaction in association with depressive symptoms in 5 independent samples. This interaction was significant in 4 of the 5 samples and a combined sample and approached significance in the fifth sample. In contrast, the NExPExEC interaction was unrelated to general anxious symptoms and thus may be specific to symptoms of depression. Implications, directions for future research, and limitations are discussed. PMID:24493906

Reduction of inappropriate benzodiazepine prescriptions among older adults through direct patient education: the EMPOWER cluster randomized trial.

PubMed

Tannenbaum, Cara; Martin, Philippe; Tamblyn, Robyn; Benedetti, Andrea; Ahmed, Sara

2014-06-01

The American Board of Internal Medicine Foundation Choosing Wisely Campaign recommends against the use of benzodiazepine drugs for adults 65 years and older. The effect of direct patient education to catalyze collaborative care for reducing inappropriate prescriptions remains unknown. To compare the effect of a direct-to-consumer educational intervention against usual care on benzodiazepine therapy discontinuation in community-dwelling older adults. Cluster randomized trial (EMPOWER [Eliminating Medications Through Patient Ownership of End Results] study [2010-2012, 6-month follow-up]). Community pharmacies were randomly allocated to the intervention or control arm in nonstratified, blocked groups of 4. Participants (303 long-term users of benzodiazepine medication aged 65-95 years, recruited from 30 community pharmacies) were screened and enrolled prior to randomization: 15 pharmacies randomized to the educational intervention included 148 participants and 15 pharmacies randomized to the "wait list" control included 155 participants. Participants, physicians, pharmacists, and evaluators were blinded to outcome assessment. The active arm received a deprescribing patient empowerment intervention describing the risks of benzodiazepine use and a stepwise tapering protocol. The control arm received usual care. Benzodiazepine therapy discontinuation at 6 months after randomization, ascertained by pharmacy medication renewal profiles. A total of 261 participants (86%) completed the 6-month follow-up. Of the recipients in the intervention group, 62% initiated conversation about benzodiazepine therapy cessation with a physician and/or pharmacist. At 6 months, 27% of the intervention group had discontinued benzodiazepine use compared with 5% of the control group (risk difference, 23% [95% CI, 14%-32%]; intracluster correlation, 0.008; number needed to treat, 4). Dose reduction occurred in an additional 11% (95% CI, 6%-16%). In multivariate subanalyses, age greater than 80 years, sex, duration of use, indication for use, dose, previous attempt to taper, and concomitant polypharmacy (10 drugs or more per day) did not have a significant interaction effect with benzodiazepine therapy discontinuation. Direct-to-consumer education effectively elicits shared decision making around the overuse of medications that increase the risk of harm in older adults. clinicaltrials.gov Identifier: NCT01148186.

Non-alcoholic beverages, unknown influence on cell proliferation - an in vitro study.

PubMed

Nowacki, Maciej; Adamowicz, Jan; Olkowska, Joanna; Pietkun, Katarzyna; Kloskowski, Tomasz; Bajek, Anna; Drewa, Tomasz

2014-01-01

The aim of the presented study was to check differences between 'Diet' and 'non-Diet' soft drinks on cell proliferation. Coca Cola and Pepsi Cola of different origin and their dietetic versions were examined at concentrations of 2% and 4%. Fructose and glucose as well as medium alone (control) were examined. Cell number was higher in media supplemented with soft drinks, compared to control. Proliferation depended on the soft drink concentration and its origin, but not on sugar and calorific content. An unknown factor is responsible for the increase in proliferation.

Intrinsic aerobic capacity correlates with greater inherent mitochondrial oxidative and H2O2 emission capacities without major shifts in myosin heavy chain isoform

PubMed Central

Seifert, Erin L.; Bastianelli, Mark; Aguer, Céline; Moffat, Cynthia; Estey, Carmen; Koch, Lauren G.; Britton, Steven L.

2012-01-01

Exercise capacity and performance strongly associate with metabolic and biophysical characteristics of skeletal muscle, factors that also relate to overall disease risk. Despite its importance, the exact mechanistic features that connect aerobic metabolism with health status are unknown. To explore this, we applied artificial selection of rats for intrinsic (i.e., untrained) aerobic treadmill running to generate strains of low- and high-capacity runners (LCR and HCR, respectively), subsequently shown to diverge for disease risk. Concurrent breeding of LCR and HCR per generation allows the lines to serve as reciprocal controls for unknown environmental changes. Here we provide the first direct evidence in mitochondria isolated from skeletal muscle that intrinsic mitochondrial capacity is higher in HCR rats. Maximal phosphorylating respiration was ∼40% greater in HCR mitochondria, independent of substrate and without altered proton leak or major changes in protein levels or muscle fiber type, consistent with altered control of phosphorylating respiration. Unexpectedly, H2O2 emission was ∼20% higher in HCR mitochondria, due to greater reduction of more harmful reactive oxygen species to H2O2; indeed, oxidative modification of mitochondrial proteins was lower. When the higher mitochondrial yield was considered, phosphorylating respiration and H2O2 emission were 70–80% greater in HCR muscle. Greater capacity of HCR muscle for work and H2O2 signaling may result in enhanced and more immediate cellular repair, possibly explaining lowered disease risks. PMID:22995392

Study on the mapping of dark matter clustering from real space to redshift space

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

Zheng, Yi; Song, Yong-Seon, E-mail: yizheng@kasi.re.kr, E-mail: ysong@kasi.re.kr

The mapping of dark matter clustering from real space to redshift space introduces the anisotropic property to the measured density power spectrum in redshift space, known as the redshift space distortion effect. The mapping formula is intrinsically non-linear, which is complicated by the higher order polynomials due to indefinite cross correlations between the density and velocity fields, and the Finger-of-God effect due to the randomness of the peculiar velocity field. Whilst the full higher order polynomials remain unknown, the other systematics can be controlled consistently within the same order truncation in the expansion of the mapping formula, as shown inmore » this paper. The systematic due to the unknown non-linear density and velocity fields is removed by separately measuring all terms in the expansion directly using simulations. The uncertainty caused by the velocity randomness is controlled by splitting the FoG term into two pieces, 1) the ''one-point' FoG term being independent of the separation vector between two different points, and 2) the ''correlated' FoG term appearing as an indefinite polynomials which is expanded in the same order as all other perturbative polynomials. Using 100 realizations of simulations, we find that the Gaussian FoG function with only one scale-independent free parameter works quite well, and that our new mapping formulation accurately reproduces the observed 2-dimensional density power spectrum in redshift space at the smallest scales by far, up to k ∼ 0.2 Mpc{sup -1}, considering the resolution of future experiments.« less

On position/force tracking control problem of cooperative robot manipulators using adaptive fuzzy backstepping approach.

PubMed

Baigzadehnoe, Barmak; Rahmani, Zahra; Khosravi, Alireza; Rezaie, Behrooz

2017-09-01

In this paper, the position and force tracking control problem of cooperative robot manipulator system handling a common rigid object with unknown dynamical models and unknown external disturbances is investigated. The universal approximation properties of fuzzy logic systems are employed to estimate the unknown system dynamics. On the other hand, by defining new state variables based on the integral and differential of position and orientation errors of the grasped object, the error system of coordinated robot manipulators is constructed. Subsequently by defining the appropriate change of coordinates and using the backstepping design strategy, an adaptive fuzzy backstepping position tracking control scheme is proposed for multi-robot manipulator systems. By utilizing the properties of internal forces, extra terms are also added to the control signals to consider the force tracking problem. Moreover, it is shown that the proposed adaptive fuzzy backstepping position/force control approach ensures all the signals of the closed loop system uniformly ultimately bounded and tracking errors of both positions and forces can converge to small desired values by proper selection of the design parameters. Finally, the theoretic achievements are tested on the two three-link planar robot manipulators cooperatively handling a common object to illustrate the effectiveness of the proposed approach. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Anti-Neuronal Autoantibodies in Both Drug Responsive and Resistant Focal Seizures with Unknown Cause.

PubMed

Gozubatik-Celik, Gokcen; Ozkara, Cigdem; Ulusoy, Canan; Gunduz, Aysegul; Delil, Sakir; Yeni, Naz; Tuzun, Erdem

2017-09-01

and Objective Autoimmunity is an emerging field of research in the etiology of different neurological disorders including epilepsy. We aimed to investigate the presence of neuronal autoantibodies in focal epilepsy with unknown cause and their clinical correlates in both drug-responsive and resistant patients. Between 2009 and 2010 94 patients were prospectively enrolled, had their antibodies tested and clinically followed." An additional 50 age- and gender-matched controls were also tested for antibodies. Age at examination, gender, age at onset, seizure frequency, risk factors, seizure precipitants, and type of seizures were noted. Plasma obtained from patients was frozen at -80°C and analysed for autoantibodies against VGKC-complex, VGCC, GAD, LGI1, CASPR2, NMDA, AMPA and GABAB receptors with immunocytochemistry and radioimmunoassay as required. Thirteen (13.8%) patients, but none of the controls, had antibodies (p=0.003). Antibodies were directed against the uncharacterized components of VGKC-complex in 5 patients (5.3%), GAD in 4 patients (4.2%), NMDA-R in 1 patient (1%), AMPA-R in 1 patient (1%) and both GAD and VGKC-complex in 2 patients (2.1%). Prognosis of epilepsy, in subsequent follow-up, did not correlate to general presence of anti-neuronal antibodies with slightly more patients with antibodies epilepsy control than without (76.9% vs. 69.1%, not-statistically significant. Three patients with suspected active autoimmunity and epilepsy who were treated, showed a response to treatment with a reduction in the seizure frequency. Although most clinical features were identical between seropositive and seronegative patient groups, seropositive patients were more likely to have inflammatory/autoimmune disorders in their medical history. In keeping with previous studies, we have shown anti-neuronal antibodies in a proportion of focal epilepsy patients. Although autoimmunity might merely occur as a bystander effect in many chronic neurological disorders, association of anti-neuronal antibodies with good response to immunotherapy and coexisting autoimmune disorders suggests that anti-neuronal autoimmunity might participate in seizure formation at least in a subgroup of focal epilepsy patients. Immunity may play a role in some patients with unknown etiology regardless of prognosis and immunmodulatuar treatment may be helpful in seropositive group. Copyright © 2017 Elsevier B.V. All rights reserved.

Nonclinical dose formulation analysis method validation and sample analysis.

PubMed

Whitmire, Monica Lee; Bryan, Peter; Henry, Teresa R; Holbrook, John; Lehmann, Paul; Mollitor, Thomas; Ohorodnik, Susan; Reed, David; Wietgrefe, Holly D

2010-12-01

Nonclinical dose formulation analysis methods are used to confirm test article concentration and homogeneity in formulations and determine formulation stability in support of regulated nonclinical studies. There is currently no regulatory guidance for nonclinical dose formulation analysis method validation or sample analysis. Regulatory guidance for the validation of analytical procedures has been developed for drug product/formulation testing; however, verification of the formulation concentrations falls under the framework of GLP regulations (not GMP). The only current related regulatory guidance is the bioanalytical guidance for method validation. The fundamental parameters for bioanalysis and formulation analysis validations that overlap include: recovery, accuracy, precision, specificity, selectivity, carryover, sensitivity, and stability. Divergence in bioanalytical and drug product validations typically center around the acceptance criteria used. As the dose formulation samples are not true "unknowns", the concept of quality control samples that cover the entire range of the standard curve serving as the indication for the confidence in the data generated from the "unknown" study samples may not always be necessary. Also, the standard bioanalytical acceptance criteria may not be directly applicable, especially when the determined concentration does not match the target concentration. This paper attempts to reconcile the different practices being performed in the community and to provide recommendations of best practices and proposed acceptance criteria for nonclinical dose formulation method validation and sample analysis.

MTR CONTROL ROOM WITH CONTROL CONSOLE AND STATUS READOUTS ALONG ...

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

MTR CONTROL ROOM WITH CONTROL CONSOLE AND STATUS READOUTS ALONG WALL. WORKERS MAKE ELECTRICAL AND OTHER CONNECTIONS. INL NEGATIVE NO. 4289. Unknown Photographer, 2/26/1952 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

Neural-network-observer-based optimal control for unknown nonlinear systems using adaptive dynamic programming

NASA Astrophysics Data System (ADS)

Liu, Derong; Huang, Yuzhu; Wang, Ding; Wei, Qinglai

2013-09-01

In this paper, an observer-based optimal control scheme is developed for unknown nonlinear systems using adaptive dynamic programming (ADP) algorithm. First, a neural-network (NN) observer is designed to estimate system states. Then, based on the observed states, a neuro-controller is constructed via ADP method to obtain the optimal control. In this design, two NN structures are used: a three-layer NN is used to construct the observer which can be applied to systems with higher degrees of nonlinearity and without a priori knowledge of system dynamics, and a critic NN is employed to approximate the value function. The optimal control law is computed using the critic NN and the observer NN. Uniform ultimate boundedness of the closed-loop system is guaranteed. The actor, critic, and observer structures are all implemented in real-time, continuously and simultaneously. Finally, simulation results are presented to demonstrate the effectiveness of the proposed control scheme.

Distributed control system for parallel-connected DC boost converters

DOEpatents

Goldsmith, Steven

2017-08-15

The disclosed invention is a distributed control system for operating a DC bus fed by disparate DC power sources that service a known or unknown load. The voltage sources vary in v-i characteristics and have time-varying, maximum supply capacities. Each source is connected to the bus via a boost converter, which may have different dynamic characteristics and power transfer capacities, but are controlled through PWM. The invention tracks the time-varying power sources and apportions their power contribution while maintaining the DC bus voltage within the specifications. A central digital controller solves the steady-state system for the optimal duty cycle settings that achieve a desired power supply apportionment scheme for a known or predictable DC load. A distributed networked control system is derived from the central system that utilizes communications among controllers to compute a shared estimate of the unknown time-varying load through shared bus current measurements and bus voltage measurements.

A disturbance based control/structure design algorithm

NASA Technical Reports Server (NTRS)

Mclaren, Mark D.; Slater, Gary L.

1989-01-01

Some authors take a classical approach to the simultaneous structure/control optimization by attempting to simultaneously minimize the weighted sum of the total mass and a quadratic form, subject to all of the structural and control constraints. Here, the optimization will be based on the dynamic response of a structure to an external unknown stochastic disturbance environment. Such a response to excitation approach is common to both the structural and control design phases, and hence represents a more natural control/structure optimization strategy than relying on artificial and vague control penalties. The design objective is to find the structure and controller of minimum mass such that all the prescribed constraints are satisfied. Two alternative solution algorithms are presented which have been applied to this problem. Each algorithm handles the optimization strategy and the imposition of the nonlinear constraints in a different manner. Two controller methodologies, and their effect on the solution algorithm, will be considered. These are full state feedback and direct output feedback, although the problem formulation is not restricted solely to these forms of controller. In fact, although full state feedback is a popular choice among researchers in this field (for reasons that will become apparent), its practical application is severely limited. The controller/structure interaction is inserted by the imposition of appropriate closed-loop constraints, such as closed-loop output response and control effort constraints. Numerical results will be obtained for a representative flexible structure model to illustrate the effectiveness of the solution algorithms.

Mechanisms of right heart disease in pulmonary hypertension (2017 Grover Conference Series).

PubMed

Asosingh, Kewal; Erzurum, Serpil

2018-01-01

Current dogma is that pathological hypertrophy of the right ventricle is a direct consequence of pulmonary vascular remodeling. However, progression of right ventricle dysfunction is not always lung-dependent. Increased afterload caused by pulmonary vascular remodeling initiates the right ventricle hypertrophy, but determinants leading to adaptive or maladaptive hypertrophy and failure remain unknown. Ischemia in a hypertrophic right ventricle may directly contribute to right heart failure. Rapidly enlarging cardiomyocytes switch from aerobic to anaerobic energy generation resulting in cell growth under relatively hypoxic conditions. Cardiac muscle reacts to an increased afterload by over-activation of the sympathetic system and uncoupling and downregulation of β-adrenergic receptors. Recent studies suggest that β blocker therapy in PH is safe, well tolerated, and preserves right ventricle function and cardiac output by reducing right ventricular glycolysis. Fibrosis, an evolutionary conserved process in host defense and wound healing, is dysregulated in maladaptive cardiac tissue contributing directly to right ventricle failure. Despite several mechanisms having been suggested in right heart disease, the causes of maladaptive cardiac remodeling remain unknown and require further research.

Multilevel adaptive control of nonlinear interconnected systems.

PubMed

Motallebzadeh, Farzaneh; Ozgoli, Sadjaad; Momeni, Hamid Reza

2015-01-01

This paper presents an adaptive backstepping-based multilevel approach for the first time to control nonlinear interconnected systems with unknown parameters. The system consists of a nonlinear controller at the first level to neutralize the interaction terms, and some adaptive controllers at the second level, in which the gains are optimally tuned using genetic algorithm. The presented scheme can be used in systems with strong couplings where completely ignoring the interactions leads to problems in performance or stability. In order to test the suitability of the method, two case studies are provided: the uncertain double and triple coupled inverted pendulums connected by springs with unknown parameters. The simulation results show that the method is capable of controlling the system effectively, in both regulation and tracking tasks. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Maternal retinoids control type 3 innate lymphoid cells and set the offspring immunity

NASA Astrophysics Data System (ADS)

van de Pavert, Serge A.; Ferreira, Manuela; Domingues, Rita G.; Ribeiro, Hélder; Molenaar, Rosalie; Moreira-Santos, Lara; Almeida, Francisca F.; Ibiza, Sales; Barbosa, Inês; Goverse, Gera; Labão-Almeida, Carlos; Godinho-Silva, Cristina; Konijn, Tanja; Schooneman, Dennis; O'Toole, Tom; Mizee, Mark R.; Habani, Yasmin; Haak, Esther; Santori, Fabio R.; Littman, Dan R.; Schulte-Merker, Stefan; Dzierzak, Elaine; Simas, J. Pedro; Mebius, Reina E.; Veiga-Fernandes, Henrique

2014-04-01

The impact of nutritional status during fetal life on the overall health of adults has been recognized; however, dietary effects on the developing immune system are largely unknown. Development of secondary lymphoid organs occurs during embryogenesis and is considered to be developmentally programmed. Secondary lymphoid organ formation depends on a subset of type 3 innate lymphoid cells (ILC3) named lymphoid tissue inducer (LTi) cells. Here we show that mouse fetal ILC3s are controlled by cell-autonomous retinoic acid (RA) signalling in utero, which pre-sets the immune fitness in adulthood. We found that embryonic lymphoid organs contain ILC progenitors that differentiate locally into mature LTi cells. Local LTi cell differentiation was controlled by maternal retinoid intake and fetal RA signalling acting in a haematopoietic cell-autonomous manner. RA controlled LTi cell maturation upstream of the transcription factor RORγt. Accordingly, enforced expression of Rorgt restored maturation of LTi cells with impaired RA signalling, whereas RA receptors directly regulated the Rorgt locus. Finally, we established that maternal levels of dietary retinoids control the size of secondary lymphoid organs and the efficiency of immune responses in the adult offspring. Our results reveal a molecular link between maternal nutrients and the formation of immune structures required for resistance to infection in the offspring.

Maternal retinoids control type 3 innate lymphoid cells and set the offspring immunity.

PubMed

van de Pavert, Serge A; Ferreira, Manuela; Domingues, Rita G; Ribeiro, Hélder; Molenaar, Rosalie; Moreira-Santos, Lara; Almeida, Francisca F; Ibiza, Sales; Barbosa, Inês; Goverse, Gera; Labão-Almeida, Carlos; Godinho-Silva, Cristina; Konijn, Tanja; Schooneman, Dennis; O'Toole, Tom; Mizee, Mark R; Habani, Yasmin; Haak, Esther; Santori, Fabio R; Littman, Dan R; Schulte-Merker, Stefan; Dzierzak, Elaine; Simas, J Pedro; Mebius, Reina E; Veiga-Fernandes, Henrique

2014-04-03

The impact of nutritional status during fetal life on the overall health of adults has been recognized; however, dietary effects on the developing immune system are largely unknown. Development of secondary lymphoid organs occurs during embryogenesis and is considered to be developmentally programmed. Secondary lymphoid organ formation depends on a subset of type 3 innate lymphoid cells (ILC3) named lymphoid tissue inducer (LTi) cells. Here we show that mouse fetal ILC3s are controlled by cell-autonomous retinoic acid (RA) signalling in utero, which pre-sets the immune fitness in adulthood. We found that embryonic lymphoid organs contain ILC progenitors that differentiate locally into mature LTi cells. Local LTi cell differentiation was controlled by maternal retinoid intake and fetal RA signalling acting in a haematopoietic cell-autonomous manner. RA controlled LTi cell maturation upstream of the transcription factor RORγt. Accordingly, enforced expression of Rorgt restored maturation of LTi cells with impaired RA signalling, whereas RA receptors directly regulated the Rorgt locus. Finally, we established that maternal levels of dietary retinoids control the size of secondary lymphoid organs and the efficiency of immune responses in the adult offspring. Our results reveal a molecular link between maternal nutrients and the formation of immune structures required for resistance to infection in the offspring.

Multiple concurrent recursive least squares identification with application to on-line spacecraft mass-property identification

NASA Technical Reports Server (NTRS)

Wilson, Edward (Inventor)

2006-01-01

The present invention is a method for identifying unknown parameters in a system having a set of governing equations describing its behavior that cannot be put into regression form with the unknown parameters linearly represented. In this method, the vector of unknown parameters is segmented into a plurality of groups where each individual group of unknown parameters may be isolated linearly by manipulation of said equations. Multiple concurrent and independent recursive least squares identification of each said group run, treating other unknown parameters appearing in their regression equation as if they were known perfectly, with said values provided by recursive least squares estimation from the other groups, thereby enabling the use of fast, compact, efficient linear algorithms to solve problems that would otherwise require nonlinear solution approaches. This invention is presented with application to identification of mass and thruster properties for a thruster-controlled spacecraft.

MoCha: Molecular Characterization of Unknown Pathways.

PubMed

Lobo, Daniel; Hammelman, Jennifer; Levin, Michael

2016-04-01

Automated methods for the reverse-engineering of complex regulatory networks are paving the way for the inference of mechanistic comprehensive models directly from experimental data. These novel methods can infer not only the relations and parameters of the known molecules defined in their input datasets, but also unknown components and pathways identified as necessary by the automated algorithms. Identifying the molecular nature of these unknown components is a crucial step for making testable predictions and experimentally validating the models, yet no specific and efficient tools exist to aid in this process. To this end, we present here MoCha (Molecular Characterization), a tool optimized for the search of unknown proteins and their pathways from a given set of known interacting proteins. MoCha uses the comprehensive dataset of protein-protein interactions provided by the STRING database, which currently includes more than a billion interactions from over 2,000 organisms. MoCha is highly optimized, performing typical searches within seconds. We demonstrate the use of MoCha with the characterization of unknown components from reverse-engineered models from the literature. MoCha is useful for working on network models by hand or as a downstream step of a model inference engine workflow and represents a valuable and efficient tool for the characterization of unknown pathways using known data from thousands of organisms. MoCha and its source code are freely available online under the GPLv3 license.

Classification of cryo electron microscopy images, noisy tomographic images recorded with unknown projection directions, by simultaneously estimating reconstructions and application to an assembly mutant of Cowpea Chlorotic Mottle Virus and portals of the bacteriophage P22

NASA Astrophysics Data System (ADS)

Lee, Junghoon; Zheng, Yili; Yin, Zhye; Doerschuk, Peter C.; Johnson, John E.

2010-08-01

Cryo electron microscopy is frequently used on biological specimens that show a mixture of different types of object. Because the electron beam rapidly destroys the specimen, the beam current is minimized which leads to noisy images (SNR substantially less than 1) and only one projection image per object (with an unknown projection direction) is collected. For situations where the objects can reasonably be described as coming from a finite set of classes, an approach based on joint maximum likelihood estimation of the reconstruction of each class and then use of the reconstructions to label the class of each image is described and demonstrated on two challenging problems: an assembly mutant of Cowpea Chlorotic Mottle Virus and portals of the bacteriophage P22.

Four chemical trends will shape the next decade's directions in Perfluoroalkyl and Polyfluoroalkyl substances research

NASA Astrophysics Data System (ADS)

Kotthoff, Matthias; Bücking, Mark

2018-04-01

Per- and polyfluoroalkyl substances (PFAS) represent a versatile group of ubiquitously occurring chemicals of increasing regulatory concern. The past years lead to an ever expanding portfolio of detected anthropogenic PFAS in numerous products encountered in daily life. Yet no clear picture of the full range of individual substance that comprise PFAS is available and this challenges analytical and engineering sciences. Authorities struggle to cope with uncertainties in managing risk of harm posed by PFAS.This is a result of an incomplete understanding of the range of compounds that they comprise in differing products. There are analytical uncertainties identifying PFAS and estimating the concentrations of the total PFAS loadindividual molecules remain unknown. There are four major trends from the chemical perspective that will shape PFAS research for the next decade. 1.Mobility: A wide and dynamic distribution of short chain PFAS due to their high polarity, persistency and volatility. 2.Substitution of regulated substances: The ban or restrictions of individual molecules will lead to a replacement with substitutes of similar concern. 3.Increase in structural diversity of existing PFAS molecules: Introduction of e.g. hydrogens and chlorine atoms instead of fluorine, as well as branching and cross-linking lead to a high versatility of unknown target molecules. 4. Unknown “Dark Matter”: The amount, identity, formation pathways, and transformation dynamics of polymers and PFAS precursors are largely unknown. These directions require optimized analytical setups, especially multi-methods, and semi-specific tools to determine PFAS-sum parameters in any relevant matrix.

Observer-based sliding mode control of Markov jump systems with random sensor delays and partly unknown transition rates

NASA Astrophysics Data System (ADS)

Yao, Deyin; Lu, Renquan; Xu, Yong; Ren, Hongru

2017-10-01

In this paper, the sliding mode control problem of Markov jump systems (MJSs) with unmeasured state, partly unknown transition rates and random sensor delays is probed. In the practical engineering control, the exact information of transition rates is hard to obtain and the measurement channel is supposed to subject to random sensor delay. Design a Luenberger observer to estimate the unmeasured system state, and an integral sliding mode surface is constructed to ensure the exponential stability of MJSs. A sliding mode controller based on estimator is proposed to drive the system state onto the sliding mode surface and render the sliding mode dynamics exponentially mean-square stable with H∞ performance index. Finally, simulation results are provided to illustrate the effectiveness of the proposed results.

Silver Nanocube and Nanobar Growth via Anisotropic Monomer Addition and Particle Attachment Processes

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

Xiao, Dongdong; Wu, Zhigang; Song, Miao

Understanding the growth mechanism of noble metal nanocrystals during solution synthesis is of significant importance for shape and property control. However, much remains unknown about the growth pathways of metal nanoparticles due to lack of direct observation. Using an in-situ transmission electron microscopy technique, we directly observed Ag nanocube and nanobar growth in aqueous solution through both classical monomer-by-monomer addition and non-classical particle attachment processes. During the particle attachment process, Ag nanocubes and nanobars formed via both oriented and non-oriented attachment. Our calculations, along with dynamics of the observed attachment, showed that van der Waals force overcame hydrodynamic and frictionmore » forces and drove the particles toward each other. During classical growth, an anisotropic growth was also revealed, and the resulting unsymmetrical shape constituted an intermediate state for Ag nanocube growth. We hypothesized that the temporary symmetry breaking resulted from different growth rates on {001} surfaces due to a local surface concentration variation caused by the imbalance between the consumption of Ag+ near the surface and the diffusion of Ag+ from bulk to surface.« less

HrpG and HrpV proteins from the Type III secretion system of Erwinia amylovora form a stable heterodimer.

PubMed

Gazi, Anastasia D; Charova, Spyridoula; Aivaliotis, Michalis; Panopoulos, Nicholas J; Kokkinidis, Michael

2015-01-01

Bacterial type III secretion systems (T3SSs) are specialized multicomponent nanomachines that mediate the transport of proteins either to extracellular locations or directly into eukaryotic host cell cytoplasm. Erwinia amylovora, the main agent of rosaceous plants fireblight disease, employs an Hrp/Hrc1 T3SS to accomplish its pathogenesis. The regulatory network that controls the activation of this T3SS is largely unknown in E. amylovora. However, in Pseudomonas syringae pathovars, the HrpG/HrpV complex has been shown to directly regulate the activity of transcription factor HrpS and consequently the upregulation of the Hrp/Hrc1 T3SS related genes. In this work, we report the successful recombinant production and purification of a stable E. amylovora HrpG/HrpV complex, using pPROpET, a bicistronic expression vector. Furthermore, we present the first solution structure of this complex based on small-angle X-ray scattering data. © FEMS 2014. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Polarized skylight does not calibrate the compass system of a migratory bat

PubMed Central

Lindecke, Oliver; Voigt, Christian C.; Pētersons, Gunārs; Holland, Richard A.

2015-01-01

In a recent study, Greif et al. (Greif et al. Nat Commun 5, 4488. (doi:10.1038/ncomms5488)) demonstrated a functional role of polarized light for a bat species confronted with a homing task. These non-migratory bats appeared to calibrate their magnetic compass by using polarized skylight at dusk, yet it is unknown if migratory bats also use these cues for calibration. During autumn migration, we equipped Nathusius' bats, Pipistrellus nathusii, with radio transmitters and tested if experimental animals exposed during dusk to a 90° rotated band of polarized light would head in a different direction compared with control animals. After release, bats of both groups continued their journey in the same direction. This observation argues against the use of a polarization-calibrated magnetic compass by this migratory bat and questions that the ability of using polarized light for navigation is a consistent feature in bats. This finding matches with observations in some passerine birds that used polarized light for calibration of their magnetic compass before but not during migration. PMID:26382077

Polarized skylight does not calibrate the compass system of a migratory bat.

PubMed

Lindecke, Oliver; Voigt, Christian C; Pētersons, Gunārs; Holland, Richard A

2015-09-01

In a recent study, Greif et al. (Greif et al. Nat Commun 5, 4488. (doi:10.1038/ncomms5488)) demonstrated a functional role of polarized light for a bat species confronted with a homing task. These non-migratory bats appeared to calibrate their magnetic compass by using polarized skylight at dusk, yet it is unknown if migratory bats also use these cues for calibration. During autumn migration, we equipped Nathusius' bats, Pipistrellus nathusii, with radio transmitters and tested if experimental animals exposed during dusk to a 90° rotated band of polarized light would head in a different direction compared with control animals. After release, bats of both groups continued their journey in the same direction. This observation argues against the use of a polarization-calibrated magnetic compass by this migratory bat and questions that the ability of using polarized light for navigation is a consistent feature in bats. This finding matches with observations in some passerine birds that used polarized light for calibration of their magnetic compass before but not during migration. © 2015 The Author(s).

High-resolution non-destructive three-dimensional imaging of integrated circuits

NASA Astrophysics Data System (ADS)

Holler, Mirko; Guizar-Sicairos, Manuel; Tsai, Esther H. R.; Dinapoli, Roberto; Müller, Elisabeth; Bunk, Oliver; Raabe, Jörg; Aeppli, Gabriel

2017-03-01

Modern nanoelectronics has advanced to a point at which it is impossible to image entire devices and their interconnections non-destructively because of their small feature sizes and the complex three-dimensional structures resulting from their integration on a chip. This metrology gap implies a lack of direct feedback between design and manufacturing processes, and hampers quality control during production, shipment and use. Here we demonstrate that X-ray ptychography—a high-resolution coherent diffractive imaging technique—can create three-dimensional images of integrated circuits of known and unknown designs with a lateral resolution in all directions down to 14.6 nanometres. We obtained detailed device geometries and corresponding elemental maps, and show how the devices are integrated with each other to form the chip. Our experiments represent a major advance in chip inspection and reverse engineering over the traditional destructive electron microscopy and ion milling techniques. Foreseeable developments in X-ray sources, optics and detectors, as well as adoption of an instrument geometry optimized for planar rather than cylindrical samples, could lead to a thousand-fold increase in efficiency, with concomitant reductions in scan times and voxel sizes.

Counteraction of urea-induced protein denaturation by trimethylamine N-oxide: a chemical chaperone at atomic resolution.

PubMed

Bennion, Brian J; Daggett, Valerie

2004-04-27

Proteins are very sensitive to their solvent environments. Urea is a common chemical denaturant of proteins, yet some animals contain high concentrations of urea. These animals have evolved an interesting mechanism to counteract the effects of urea by using trimethylamine N-oxide (TMAO). The molecular basis for the ability of TMAO to act as a chemical chaperone remains unknown. Here, we describe molecular dynamics simulations of a small globular protein, chymotrypsin inhibitor 2, in 8 M urea and 4 M TMAO/8 M urea solutions, in addition to other control simulations, to investigate this effect at the atomic level. In 8 M urea, the protein unfolds, and urea acts in both a direct and indirect manner to achieve this effect. In contrast, introduction of 4 M TMAO counteracts the effect of urea and the protein remains well structured. TMAO makes few direct interactions with the protein. Instead, it prevents unfolding of the protein by structuring the solvent. In particular, TMAO orders the solvent and discourages it from competing with intraprotein H bonds and breaking up the hydrophobic core of the protein.

High-resolution non-destructive three-dimensional imaging of integrated circuits.

PubMed

Holler, Mirko; Guizar-Sicairos, Manuel; Tsai, Esther H R; Dinapoli, Roberto; Müller, Elisabeth; Bunk, Oliver; Raabe, Jörg; Aeppli, Gabriel

2017-03-15

Modern nanoelectronics has advanced to a point at which it is impossible to image entire devices and their interconnections non-destructively because of their small feature sizes and the complex three-dimensional structures resulting from their integration on a chip. This metrology gap implies a lack of direct feedback between design and manufacturing processes, and hampers quality control during production, shipment and use. Here we demonstrate that X-ray ptychography-a high-resolution coherent diffractive imaging technique-can create three-dimensional images of integrated circuits of known and unknown designs with a lateral resolution in all directions down to 14.6 nanometres. We obtained detailed device geometries and corresponding elemental maps, and show how the devices are integrated with each other to form the chip. Our experiments represent a major advance in chip inspection and reverse engineering over the traditional destructive electron microscopy and ion milling techniques. Foreseeable developments in X-ray sources, optics and detectors, as well as adoption of an instrument geometry optimized for planar rather than cylindrical samples, could lead to a thousand-fold increase in efficiency, with concomitant reductions in scan times and voxel sizes.

naked cuticle targets dishevelled to antagonize Wnt signal transduction

PubMed Central

Rousset, Raphaël; Mack, Judith A.; Wharton, Keith A.; Axelrod, Jeffrey D.; Cadigan, Ken M.; Fish, Matthew P.; Nusse, Roel; Scott, Matthew P.

2001-01-01

In Drosophila embryos the protein Naked cuticle (Nkd) limits the effects of the Wnt signal Wingless (Wg) during early segmentation. nkd loss of function results in segment polarity defects and embryonic death, but how nkd affects Wnt signaling is unknown. Using ectopic expression, we find that Nkd affects, in a cell-autonomous manner, a transduction step between the Wnt signaling components Dishevelled (Dsh) and Zeste-white 3 kinase (Zw3). Zw3 is essential for repressing Wg target-gene transcription in the absence of a Wg signal, and the role of Wg is to relieve this inhibition. Our double-mutant analysis shows that, in contrast to Zw3, Nkd acts when the Wg pathway is active to restrain signal transduction. Yeast two hybrid and in vitro experiments indicate that Nkd directly binds to the basic-PDZ region of Dsh. Specially timed Nkd overexpression is capable of abolishing Dsh function in a distinct signaling pathway that controls planar-cell polarity. Our results suggest that Nkd acts directly through Dsh to limit Wg activity and thus determines how efficiently Wnt signals stabilize Armadillo (Arm)/β-catenin and activate downstream genes. PMID:11274052

Cloning the Antibody Response in Humans with Chronic Inflammatory Disease: Immunopanning of Subacute Sclerosing Panencephalitis (SSPE) Brain Sections with Antibody Phage Libraries Prepared from SSPE Brain Enriches for Antibody Recognizing Measles Virus Antigens In Situ

PubMed Central

Owens, Gregory P.; Williamson, R. Anthony; Burgoon, Mark P.; Ghausi, Omar; Burton, Dennis R.; Gilden, Donald H.

2000-01-01

In central nervous system (CNS) infectious and inflammatory diseases of known cause, oligoclonal bands represent antibody directed against the causative agent. To determine whether disease-relevant antibodies can be cloned from diseased brain, we prepared an antibody phage display library from the brain of a human with subacute sclerosing panencephalitis (SSPE), a chronic encephalitis caused by measles virus, and selected the library against SSPE brain sections. Antibodies that were retrieved reacted strongly with measles virus cell extracts by enzyme-linked immunosorbent assay and were specific for the measles virus nucleocapsid protein. These antibodies immunostained cells in different SSPE brains but not in control brain. Our data provide the first demonstration that diseased brain can be used to select in situ for antibodies directed against the causative agent of disease and point to the potential usefulness of this approach in identifying relevant antibodies in chronic CNS or systemic inflammatory diseases of unknown cause. PMID:10627565

Neonatal Restriction of Tactile Inputs Leads to Long-Lasting Impairments of Cross-Modal Processing

PubMed Central

Röder, Brigitte; Hanganu-Opatz, Ileana L.

2015-01-01

Optimal behavior relies on the combination of inputs from multiple senses through complex interactions within neocortical networks. The ontogeny of this multisensory interplay is still unknown. Here, we identify critical factors that control the development of visual-tactile processing by combining in vivo electrophysiology with anatomical/functional assessment of cortico-cortical communication and behavioral investigation of pigmented rats. We demonstrate that the transient reduction of unimodal (tactile) inputs during a short period of neonatal development prior to the first cross-modal experience affects feed-forward subcortico-cortical interactions by attenuating the cross-modal enhancement of evoked responses in the adult primary somatosensory cortex. Moreover, the neonatal manipulation alters cortico-cortical interactions by decreasing the cross-modal synchrony and directionality in line with the sparsification of direct projections between primary somatosensory and visual cortices. At the behavioral level, these functional and structural deficits resulted in lower cross-modal matching abilities. Thus, neonatal unimodal experience during defined developmental stages is necessary for setting up the neuronal networks of multisensory processing. PMID:26600123

Selenomethionine protects against neuronal degeneration by methylmercury in the developing rat cerebrum.

PubMed

Sakamoto, Mineshi; Yasutake, Akira; Kakita, Akiyoshi; Ryufuku, Masae; Chan, Hing Man; Yamamoto, Megumi; Oumi, Sanae; Kobayashi, Sayaka; Watanabe, Chiho

2013-03-19

Although many experimental studies have shown that selenium protects against methylmercury (MeHg) toxicity at different end points, the direct interactive effects of selenium and MeHg on neurons in the brain remain unknown. Our goal is to confirm the protective effects of selenium against neuronal degeneration induced by MeHg in the developing postnatal rat brain using a postnatal rat model that is suitable for extrapolating the effects of MeHg to the fetal brain of humans. As an exposure source of selenium, we used selenomethionine (SeMet), a food-originated selenium. Wistar rats of postnatal days 14 were orally administered with vehicle (control), MeHg (8 mg Hg/kg/day), SeMet (2 mg Se/kg/day), or MeHg plus SeMet coexposure for 10 consecutive days. Neuronal degeneration and reactive astrocytosis were observed in the cerebral cortex of the MeHg-group but the symptoms were prevented by coexposure to SeMet. These findings serve as a proof that dietary selenium can directly protect neurons against MeHg toxicity in the mammalian brain, especially in the developing cerebrum.

Early efforts in modeling the incubation period of infectious diseases with an acute course of illness.

PubMed

Nishiura, Hiroshi

2007-05-11

The incubation period of infectious diseases, the time from infection with a microorganism to onset of disease, is directly relevant to prevention and control. Since explicit models of the incubation period enhance our understanding of the spread of disease, previous classic studies were revisited, focusing on the modeling methods employed and paying particular attention to relatively unknown historical efforts. The earliest study on the incubation period of pandemic influenza was published in 1919, providing estimates of the incubation period of Spanish flu using the daily incidence on ships departing from several ports in Australia. Although the study explicitly dealt with an unknown time of exposure, the assumed periods of exposure, which had an equal probability of infection, were too long, and thus, likely resulted in slight underestimates of the incubation period. After the suggestion that the incubation period follows lognormal distribution, Japanese epidemiologists extended this assumption to estimates of the time of exposure during a point source outbreak. Although the reason why the incubation period of acute infectious diseases tends to reveal a right-skewed distribution has been explored several times, the validity of the lognormal assumption is yet to be fully clarified. At present, various different distributions are assumed, and the lack of validity in assuming lognormal distribution is particularly apparent in the case of slowly progressing diseases. The present paper indicates that (1) analysis using well-defined short periods of exposure with appropriate statistical methods is critical when the exact time of exposure is unknown, and (2) when assuming a specific distribution for the incubation period, comparisons using different distributions are needed in addition to estimations using different datasets, analyses of the determinants of incubation period, and an understanding of the underlying disease mechanisms.

Market-Based Coordination of Thermostatically Controlled Loads—Part II: Unknown Parameters and Case Studies

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

Li, Sen; Zhang, Wei; Lian, Jianming

This two-part paper considers the coordination of a population of Thermostatically Controlled Loads (TCLs) with unknown parameters to achieve group objectives. The problem involves designing the bidding and market clearing strategy to motivate self-interested users to realize efficient energy allocation subject to a peak power constraint. The companion paper (Part I) formulates the problem and proposes a load coordination framework using the mechanism design approach. To address the unknown parameters, Part II of this paper presents a joint state and parameter estimation framework based on the expectation maximization algorithm. The overall framework is then validated using real-world weather data andmore » price data, and is compared with other approaches in terms of aggregated power response. Simulation results indicate that our coordination framework can effectively improve the efficiency of the power grid operations and reduce power congestion at key times.« less

Off-Policy Integral Reinforcement Learning Method to Solve Nonlinear Continuous-Time Multiplayer Nonzero-Sum Games.

PubMed

Song, Ruizhuo; Lewis, Frank L; Wei, Qinglai

2017-03-01

This paper establishes an off-policy integral reinforcement learning (IRL) method to solve nonlinear continuous-time (CT) nonzero-sum (NZS) games with unknown system dynamics. The IRL algorithm is presented to obtain the iterative control and off-policy learning is used to allow the dynamics to be completely unknown. Off-policy IRL is designed to do policy evaluation and policy improvement in the policy iteration algorithm. Critic and action networks are used to obtain the performance index and control for each player. The gradient descent algorithm makes the update of critic and action weights simultaneously. The convergence analysis of the weights is given. The asymptotic stability of the closed-loop system and the existence of Nash equilibrium are proved. The simulation study demonstrates the effectiveness of the developed method for nonlinear CT NZS games with unknown system dynamics.

Market-Based Coordination of Thermostatically Controlled Loads—Part I: A Mechanism Design Formulation

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

Li, Sen; Zhang, Wei; Lian, Jianming

This paper focuses on the coordination of a population of Thermostatically Controlled Loads (TCLs) with unknown parameters to achieve group objectives. The problem involves designing the bidding and market clearing strategy to motivate self-interested users to realize efficient energy allocation subject to a peak power constraint. Using the mechanism design approach, we propose a market-based coordination framework, which can effectively incorporate heterogeneous load dynamics, systematically deal with user preferences, account for the unknown load model parameters, and enable the real-world implementation with limited communication resources. This paper is divided into two parts. Part I presents a mathematical formulation of themore » problem and develops a coordination framework using the mechanism design approach. Part II presents a learning scheme to account for the unknown load model parameters, and evaluates the proposed framework through realistic simulations.« less

Analysis of sensorless control of brushless DC motor using unknown input observer with different gains

NASA Astrophysics Data System (ADS)

Astik, Mitesh B.; Bhatt, Praghnesh; Bhalja, Bhavesh R.

2017-03-01

A sensorless control scheme based on an unknown input observer is presented in this paper in which back EMF of the Brushless DC Motor (BLDC) is continuously estimated from available line voltages and currents. During negative rotation of motor, actual and estimated speed fail to track the reference speed and if the corrective action is not taken by the observer, the motor goes into saturation. To overcome this problem, the speed estimation algorithm has been implemented in this paper to control the dynamic behavior of the motor during negative rotation. The Ackermans method was used to calculate the gains of an unknown input observer which is based on the appropriate choice of the eigenvalues in advance. The criteria to choose eigenvalue is to obtain a balance between faster convergence rate and the least noise level. Simulations have been carried out for different disturbances such as step changes in motor reference speed and load torque. The comparative simulation results clearly depict that the disturbance effects in actual and estimated responses minimizes as observer gain setting increases.

Three-dimensional cinematography with control object of unknown shape.

PubMed

Dapena, J; Harman, E A; Miller, J A

1982-01-01

A technique for reconstruction of three-dimensional (3D) motion which involves a simple filming procedure but allows the deduction of coordinates in large object volumes was developed. Internal camera parameters are calculated from measurements of the film images of two calibrated crosses while external camera parameters are calculated from the film images of points in a control object of unknown shape but at least one known length. The control object, which includes the volume in which the activity is to take place, is formed by a series of poles placed at unknown locations, each carrying two targets. From the internal and external camera parameters, and from locations of the images of point in the films of the two cameras, 3D coordinates of the point can be calculated. Root mean square errors of the three coordinates of points in a large object volume (5m x 5m x 1.5m) were 15 mm, 13 mm, 13 mm and 6 mm, and relative errors in lengths averaged 0.5%, 0.7% and 0.5%, respectively.

Analysis of select Dalbergia and trade timber using direct analysis in real time and time-of-flight mass spectrometry for CITES enforcement.

PubMed

Lancaster, Cady; Espinoza, Edgard

2012-05-15

International trade of several Dalbergia wood species is regulated by The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In order to supplement morphological identification of these species, a rapid chemical method of analysis was developed. Using Direct Analysis in Real Time (DART) ionization coupled with Time-of-Flight (TOF) Mass Spectrometry (MS), selected Dalbergia and common trade species were analyzed. Each of the 13 wood species was classified using principal component analysis and linear discriminant analysis (LDA). These statistical data clusters served as reliable anchors for species identification of unknowns. Analysis of 20 or more samples from the 13 species studied in this research indicates that the DART-TOFMS results are reproducible. Statistical analysis of the most abundant ions gave good classifications that were useful for identifying unknown wood samples. DART-TOFMS and LDA analysis of 13 species of selected timber samples and the statistical classification allowed for the correct assignment of unknown wood samples. This method is rapid and can be useful when anatomical identification is difficult but needed in order to support CITES enforcement. Published 2012. This article is a US Government work and is in the public domain in the USA.

Controlled Synthesis of Polyenes by Catalytic Methods. Progress Report, December 1, 1989 -- November 30, 1992

DOE R&D Accomplishments Database

Schrock, R. R.

1992-01-01

A more direct approach to polyenes by the direct polymerization of acetylenes has been achieved. We were able to show that polymerization of acetylene itself can be controlled with a well- characterized alkylidene catalyst, but only if a base such as quinuclidine is present in order to slow down the rate of propagation relative to initiation. (Quinuclidine may also stabilize vinylalkylidene intermediates formed in the reaction). Unfortunately, living polyenes were no more stable than isolated polyenes, and so this approach had its limitations. Direct polymerization of acetylene by Mo(CH-t-Bu)(NAr)(O-t-Bu){sub 2} was more successful, but inherent polyene instability was still a problem. The most important result of the past grant period is the finding that dipropargyl derivatives (HC=CCH{sub 2}XCH{sub 2}C=CH; X = CH{sub 2}, C(CO{sub 2}R){sub 2}, SiR{sub 2}, etc.), which have been reported to be cyclopolymerized by various classical catalysts by as yet unknown mechanisms, are polymerized by Mo(CH-t-Bu)(NAr)[OCMe(CF{sub 3}){sub 2}]{sub 2} in dimethoxyethane. We speculate that intramolecular formation of a five-membered ring in the product of {alpha} addition is fast enough to yield another terminal alkylidene on the time scale of the polymerization reaction, while a six-membered ring is formed in a reaction involving a more reaction terminal alkylidene. Either intermediate alkylidene, but most likely the terminal alkylidene, could react with additional monomer to lead to growth of a chain having dangling triple bonds that eventually could be employed to form crosslinks.

Fuzzy Adaptive Decentralized Optimal Control for Strict Feedback Nonlinear Large-Scale Systems.

PubMed

Sun, Kangkang; Sui, Shuai; Tong, Shaocheng

2018-04-01

This paper considers the optimal decentralized fuzzy adaptive control design problem for a class of interconnected large-scale nonlinear systems in strict feedback form and with unknown nonlinear functions. The fuzzy logic systems are introduced to learn the unknown dynamics and cost functions, respectively, and a state estimator is developed. By applying the state estimator and the backstepping recursive design algorithm, a decentralized feedforward controller is established. By using the backstepping decentralized feedforward control scheme, the considered interconnected large-scale nonlinear system in strict feedback form is changed into an equivalent affine large-scale nonlinear system. Subsequently, an optimal decentralized fuzzy adaptive control scheme is constructed. The whole optimal decentralized fuzzy adaptive controller is composed of a decentralized feedforward control and an optimal decentralized control. It is proved that the developed optimal decentralized controller can ensure that all the variables of the control system are uniformly ultimately bounded, and the cost functions are the smallest. Two simulation examples are provided to illustrate the validity of the developed optimal decentralized fuzzy adaptive control scheme.

Control Of A Serpentine Robot For Inspection Tasks

NASA Technical Reports Server (NTRS)

Seraji, Homayoun; Colbaugh, Richard D.; Glass, Kristin L.

1996-01-01

Efficient, robust kinematic control scheme developed to control serpentine robot designed to inspect complex structure. Takes full advantage of multiple redundant degrees of freedom of robot to provide considerable dexterity for maneuvering through workspace cluttered with stationary obstacles at initially unknown positions. Control scheme produces slithering motion.

Fire behavior, fuel treatments, and fire suppression on the Hayman Fire - Part 4: Relation of roads to burn severity

Treesearch

Charles W. McHugh; Mark A. Finney

2003-01-01

Effects of roads on fire behavior intensity and severity can be studied directly or indirectly. A direct study of road effects would include uses by fire suppression, burnout operations, and delay of fire progress at the roadside. Interpretations after the fire burns are easily confounded by the unknown nature of suppression activities and fire arrival time, and fire...

A new genus of long-legged flies displaying remarkable wing directional asymmetry

Treesearch

Justin B. Runyon; Richard L. Hurley

2004-01-01

A previously unknown group of flies is described whose males exhibit directional asymmetry, in that the left wing is larger than, and of a different shape from, the right wing. To our knowledge, wing asymmetry of this degree has not previously been reported in an animal capable of flight. Such consistent asymmetry must result from a left­right axis during development...

Numerical inverse method predicting acoustic spinning modes radiated by a ducted fan from free-field test data.

PubMed

Lewy, Serge

2008-07-01

Spinning modes generated by a ducted turbofan at a given frequency determine the acoustic free-field directivity. An inverse method starting from measured directivity patterns is interesting in providing information on the noise sources without requiring tedious spinning-mode experimental analyses. According to a previous article, equations are based on analytical modal splitting inside a cylindrical duct and on a Rayleigh or a Kirchhoff integral on the duct exit cross section to get far-field directivity. Equations are equal in number to free-field measurement locations and the unknowns are the propagating mode amplitudes (there are generally more unknowns than equations). A MATLAB procedure has been implemented by using either the pseudoinverse function or the backslash operator. A constraint comes from the fact that squared modal amplitudes must be positive which involves an iterative least squares fitting. Numerical simulations are discussed along with several examples based on tests performed by Rolls-Royce in the framework of a European project. It is assessed that computation is very fast and it well fits the measured directivities, but the solution depends on the method and is not unique. This means that the initial set of modes should be chosen according to any known physical property of the acoustic sources.

Compensatory changes accompanying chronic forced use of the nondominant hand by unilateral amputees.

PubMed

Philip, Benjamin A; Frey, Scott H

2014-03-05

Amputation of the dominant hand forces patients to use the nondominant hand exclusively, including for tasks (e.g., writing and drawing) that were formerly the sole domain of the dominant hand. The behavioral and neurological effects of this chronic forced use of the nondominant hand remain largely unknown. Yet, these effects may shed light on the potential to compensate for degradation or loss of dominant hand function, as well as the mechanisms that support motor learning under conditions of very long-term training. We used a novel precision drawing task and fMRI to investigate 8 adult human amputees with chronic (mean 33 years) unilateral dominant (right) hand absence, and right-handed matched controls (8 for fMRI, 19 for behavior). Amputees' precision drawing performances with their left hands reached levels of smoothness (associated with left hemisphere control), acceleration time (associated with right hemisphere control), and speed equivalent to controls' right hands, whereas accuracy maintained a level comparable with controls' left hands. This compensation is supported by an experience-dependent shift from heavy reliance on the dorsodorsal parietofrontal pathway (feedback control) to the ventrodorsal pathway and prefrontal regions involved in the cognitive control of goal-directed actions. Relative to controls, amputees also showed increased activity within the former cortical sensorimotor hand territory in the left (ipsilateral) hemisphere. These data demonstrate that, with chronic and exclusive forced use, the speed and quality of nondominant hand precision endpoint control in drawing can achieve levels nearly comparable with the dominant hand.

Detection of brain-directed autoantibodies in the serum of non-small cell lung cancer patients.

PubMed

Banjara, Manoj; Ghosh, Chaitali; Dadas, Aaron; Mazzone, Peter; Janigro, Damir

2017-01-01

Antibodies against brain proteins were identified in the plasma of cancer patients and are defined to cause paraneoplastic neurological syndromes. The profiles of brain-directed antibodies in non-small cell lung cancer (NSCLC) are largely unknown. Here, for the first time, we compared autoantibodies against brain proteins in NSCLC (n = 18) against those present in age-matched non-cancer control subjects (n = 18) with a similar life-style, habit, and medical history. Self-recognizing immunoglobulin (IgG) are primarily directed against cells in the cortex (P = 0.008), hippocampus (P = 0.003-0.05), and cerebellum (P = 0.02). More specifically, IgG targets were prominent in the pyramidal, Purkinje, and granule cell layers. Furthermore, autoimmune IgG signals were localized to neurons (81%), astrocytes (48%), and endothelial (29%) cells. While cancer sera yielded overall higher intensity signals, autoantigens of 100, 65, 45, 37, and 30 kDa molecular weights were the most represented. Additionally, a group of 100 kDa proteins seem more prevalent in female adenocarcinoma patients (4/5, 80%). In conclusion, our results revealed autoantigen specificity in NSCLC, which implicitly depends on patient's demographics and disease history. Patients at risk for lung cancer but with no active disease revealed that the immune profile in NSCLC is disease-dependent.

Novel prescribed performance neural control of a flexible air-breathing hypersonic vehicle with unknown initial errors.

PubMed

Bu, Xiangwei; Wu, Xiaoyan; Zhu, Fujing; Huang, Jiaqi; Ma, Zhen; Zhang, Rui

2015-11-01

A novel prescribed performance neural controller with unknown initial errors is addressed for the longitudinal dynamic model of a flexible air-breathing hypersonic vehicle (FAHV) subject to parametric uncertainties. Different from traditional prescribed performance control (PPC) requiring that the initial errors have to be known accurately, this paper investigates the tracking control without accurate initial errors via exploiting a new performance function. A combined neural back-stepping and minimal learning parameter (MLP) technology is employed for exploring a prescribed performance controller that provides robust tracking of velocity and altitude reference trajectories. The highlight is that the transient performance of velocity and altitude tracking errors is satisfactory and the computational load of neural approximation is low. Finally, numerical simulation results from a nonlinear FAHV model demonstrate the efficacy of the proposed strategy. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Nosocomial infection control in healthcare settings: Protection against emerging infectious diseases.

PubMed

Fu, Chuanxi; Wang, Shengyong

2016-04-12

The Middle East respiratory syndrome (MERS) outbreak in Korea in 2015 may be attributable to poor nosocomial infection control procedures implemented. Strict infection control measures were taken in the hospital where an imported case with MERS was treated in southern China and 53 health care workers were confirmed to be MERS-CoV negative. Infection control in healthcare settings, in which patients with emerging infectious diseases such as MERS, Ebola virus disease, and the severe acute respiratory syndrome (SARS) are diagnosed and treated, are often imperfect. When it comes to emerging or unknown infectious diseases, before the imported case was finally identified or community transmission was reported, cases have often occurred in clusters in healthcare settings. Nosocomial infection control measures should be further strengthened among the workers and inpatients in designated healthcare settings that accommodate suspected cases suffering from emerging or unknown infectious diseases.

Planar maneuvering control of underwater snake robots using virtual holonomic constraints.

PubMed

Kohl, Anna M; Kelasidi, Eleni; Mohammadi, Alireza; Maggiore, Manfredi; Pettersen, Kristin Y

2016-11-24

This paper investigates the problem of planar maneuvering control for bio-inspired underwater snake robots that are exposed to unknown ocean currents. The control objective is to make a neutrally buoyant snake robot which is subject to hydrodynamic forces and ocean currents converge to a desired planar path and traverse the path with a desired velocity. The proposed feedback control strategy enforces virtual constraints which encode biologically inspired gaits on the snake robot configuration. The virtual constraints, parametrized by states of dynamic compensators, are used to regulate the orientation and forward speed of the snake robot. A two-state ocean current observer based on relative velocity sensors is proposed. It enables the robot to follow the path in the presence of unknown constant ocean currents. The efficacy of the proposed control algorithm for several biologically inspired gaits is verified both in simulations for different path geometries and in experiments.

Helping to combat chronic wasting disease

USGS Publications Warehouse

,

2003-01-01

Chronic wasting disease (CWD) is a disease of the nervous system that results in distinctive brain lesions. CWD affects elk, white-tailed deer, and mule deer, but has not been documented in livestock or humans. The origins of the disease, as well as the modes of transmission, remain unknown. Infected deer and elk appear robust and healthy in the early stages of CWD; clinical signs might not show for years. Mortality typically occurs within months after the appearance of clinical signs. The route of transmission is unknown; likely routes include direct transmission between infected and noninfected animals and infected animals contaminating local environments.

Irreversible temperature gating in trpv1 sheds light on channel activation.

PubMed

Sánchez-Moreno, Ana; Guevara-Hernández, Eduardo; Contreras-Cervera, Ricardo; Rangel-Yescas, Gisela; Ladrón-de-Guevara, Ernesto; Rosenbaum, Tamara; Islas, León D

2018-06-05

Temperature-activated TRP channels or thermoTRPs are among the only proteins that can directly convert temperature changes into changes in channel open probability. In spite of a wealth of functional and structural information, the mechanism of temperature activation remains unknown. We have carefully characterized the repeated activation of TRPV1 by thermal stimuli and discovered a previously unknown inactivation process, which is irreversible. We propose that this form of gating in TRPV1 channels is a consequence of the heat absorption process that leads to channel opening. © 2018, Sánchez-Moreno et al.

Organochlorine pesticide level in patients with chronic kidney disease of unknown etiology and its association with renal function.

PubMed

Ghosh, Rishila; Siddarth, Manushi; Singh, Neeru; Tyagi, Vipin; Kare, Pawan Kumar; Banerjee, Basu Dev; Kalra, Om Prakash; Tripathi, Ashok Kumar

2017-05-26

Involvement of agrochemicals have been suggested in the development of chronic kidney disease of unknown etiology (CKDu). The association between CKDu and blood level of organochlorine pesticides (OCPs) in CKDu patients has been examined in the present study. All the recruited study subjects (n = 300) were divided in three groups, namely, healthy control (n = 100), patients with chronic kidney disease of unknown etiology (n = 100), and patients with chronic kidney disease of known etiology (CKDk) (n = 100). Blood OCP levels of all three study groups were analyzed by gas chromatography. Increased level of OCPs, namely α-HCH, aldrin, and β-endosulfan, were observed in CKDu patients as compared to healthy control and CKD patients of known etiology. The levels of these pesticides significantly correlated negatively with the estimated glomerular filtration rate (eGFR) and positively with urinary albumin of CKD patients. Logistic regression analysis revealed association of γ-HCH, p, p'-DDE, and β-endosulfan with CKDu on adjustment of age, sex, BMI, and total lipid content. Increased blood level of certain organochlorine pesticides is associated with the development of chronic kidney disease of unknown etiology.

IMPLICIT DUAL CONTROL BASED ON PARTICLE FILTERING AND FORWARD DYNAMIC PROGRAMMING.

PubMed

Bayard, David S; Schumitzky, Alan

2010-03-01

This paper develops a sampling-based approach to implicit dual control. Implicit dual control methods synthesize stochastic control policies by systematically approximating the stochastic dynamic programming equations of Bellman, in contrast to explicit dual control methods that artificially induce probing into the control law by modifying the cost function to include a term that rewards learning. The proposed implicit dual control approach is novel in that it combines a particle filter with a policy-iteration method for forward dynamic programming. The integration of the two methods provides a complete sampling-based approach to the problem. Implementation of the approach is simplified by making use of a specific architecture denoted as an H-block. Practical suggestions are given for reducing computational loads within the H-block for real-time applications. As an example, the method is applied to the control of a stochastic pendulum model having unknown mass, length, initial position and velocity, and unknown sign of its dc gain. Simulation results indicate that active controllers based on the described method can systematically improve closed-loop performance with respect to other more common stochastic control approaches.

Opposite-directional sex change in functional female protandrous anemonefish, Amphiprion clarkii: effect of aromatase inhibitor on the ovarian tissue.

PubMed

Nakamura, Masaru; Miura, Saori; Nozu, Ryo; Kobayashi, Yasuhisa

2015-01-01

The anemonefish, Amphiprion clarkii, is a protandrous hermaphrodite. Under appropriate social conditions, male fish can become female. Previous studies indicated that estrogens are important regulators of sex change in this fish. However, the mechanism of sexual plasticity in the gonad of this fish is still unknown. To elucidate the mechanisms underlying the sexual plasticity in the ovary of female anemonefish, an aromatase inhibitor (AI, 500 μg/g diet) was administered to the functional female fish for 80 days. The levels of estradiol-17β (E2) in the fish treated with AI were significantly lower than those in the control group. Three out of five fish had ambisexual gonads with active spermatogenic germ cells in the ovarian tissue. However, female fish in the AI-treated group prior to treatment and those in the control group displayed no testicular characteristics in their developed ovaries. This result strongly suggests that germ cells with bipotentiality or spermatogonial cells remain in the functional ovaries of anemonefish following sex change from functional males to functional females. There is a possibility that estrogen depletion due to AI treatment might have caused the opposite-directional sex change from functional female to male in the anemonefish. The anemonefish keeps their high sexual bipotential in the ovary after sex change.

Genome-wide Expression Profiling, In Vivo DNA Binding Analysis, and Probabilistic Motif Prediction Reveal Novel Abf1 Target Genes during Fermentation, Respiration, and Sporulation in Yeast

PubMed Central

Schlecht, Ulrich; Erb, Ionas; Demougin, Philippe; Robine, Nicolas; Borde, Valérie; van Nimwegen, Erik; Nicolas, Alain

2008-01-01

The autonomously replicating sequence binding factor 1 (Abf1) was initially identified as an essential DNA replication factor and later shown to be a component of the regulatory network controlling mitotic and meiotic cell cycle progression in budding yeast. The protein is thought to exert its functions via specific interaction with its target site as part of distinct protein complexes, but its roles during mitotic growth and meiotic development are only partially understood. Here, we report a comprehensive approach aiming at the identification of direct Abf1-target genes expressed during fermentation, respiration, and sporulation. Computational prediction of the protein's target sites was integrated with a genome-wide DNA binding assay in growing and sporulating cells. The resulting data were combined with the output of expression profiling studies using wild-type versus temperature-sensitive alleles. This work identified 434 protein-coding loci as being transcriptionally dependent on Abf1. More than 60% of their putative promoter regions contained a computationally predicted Abf1 binding site and/or were bound by Abf1 in vivo, identifying them as direct targets. The present study revealed numerous loci previously unknown to be under Abf1 control, and it yielded evidence for the protein's variable DNA binding pattern during mitotic growth and meiotic development. PMID:18305101

Directly administered antiretroviral therapy for HIV-infected drug users does not have an impact on antiretroviral resistance: results from a randomized controlled trial.

PubMed

Maru, Duncan Smith-Rohrberg; Kozal, Michael J; Bruce, R Douglas; Springer, Sandra A; Altice, Frederick L

2007-12-15

Directly administered antiretroviral therapy (DAART) is an effective intervention that improves clinical outcomes among HIV-infected drug users. Its effects on antiretroviral drug resistance, however, are unknown. We conducted a community-based, prospective, randomized controlled trial of DAART compared with self-administered therapy (SAT). We performed a modified intention-to-treat analysis among 115 subjects who provided serum samples for HIV genotypic resistance testing at baseline and at follow-up. The main outcomes measures included total genotypic sensitivity score, future drug options, number of new drug resistance mutations (DRMs), and number of new major International AIDS Society (IAS) mutations. The adjusted probability of developing at least 1 new DRM did not differ between the 2 arms (SAT: 0.41 per person-year [PPY], DAART: 0.49 PPY; adjusted relative risk [RR] = 1.04; P = 0.90), nor did the number of new mutations (SAT: 0.76 PPY, DAART: 0.83 PPY; adjusted RR = 0.99; P = 0.99) or the probability of developing new major IAS new drug mutations (SAT: 0.30 PPY, DAART: 0.33 PPY; adjusted RR = 1.12; P = 0.78). On measures of GSS and FDO, the 2 arms also did not differ. In this trial, DAART provided on-treatment virologic benefit for HIV-infected drug users without affecting the rate of development of antiretroviral medication resistance.

Establishment of multiple sublineages of H5N1 influenza virus in Asia: Implications for pandemic control

PubMed Central

Chen, H.; Smith, G. J. D.; Li, K. S.; Wang, J.; Fan, X. H.; Rayner, J. M.; Vijaykrishna, D.; Zhang, J. X.; Zhang, L. J.; Guo, C. T.; Cheung, C. L.; Xu, K. M.; Duan, L.; Huang, K.; Qin, K.; Leung, Y. H. C.; Wu, W. L.; Lu, H. R.; Chen, Y.; Xia, N. S.; Naipospos, T. S. P.; Yuen, K. Y.; Hassan, S. S.; Bahri, S.; Nguyen, T. D.; Webster, R. G.; Peiris, J. S. M.; Guan, Y.

2006-01-01

Preparedness for a possible influenza pandemic caused by highly pathogenic avian influenza A subtype H5N1 has become a global priority. The spread of the virus to Europe and continued human infection in Southeast Asia have heightened pandemic concern. It remains unknown from where the pandemic strain may emerge; current attention is directed at Vietnam, Thailand, and, more recently, Indonesia and China. Here, we report that genetically and antigenically distinct sublineages of H5N1 virus have become established in poultry in different geographical regions of Southeast Asia, indicating the long-term endemicity of the virus, and the isolation of H5N1 virus from apparently healthy migratory birds in southern China. Our data show that H5N1 influenza virus, has continued to spread from its established source in southern China to other regions through transport of poultry and bird migration. The identification of regionally distinct sublineages contributes to the understanding of the mechanism for the perpetuation and spread of H5N1, providing information that is directly relevant to control of the source of infection in poultry. It points to the necessity of surveillance that is geographically broader than previously supposed and that includes H5N1 viruses of greater genetic and antigenic diversity. PMID:16473931

MicroRNAs control hepatocyte proliferation during liver regeneration.

PubMed

Song, Guisheng; Sharma, Amar Deep; Roll, Garrett R; Ng, Raymond; Lee, Andrew Y; Blelloch, Robert H; Frandsen, Niels M; Willenbring, Holger

2010-05-01

MicroRNAs (miRNAs) constitute a new class of regulators of gene expression. Among other actions, miRNAs have been shown to control cell proliferation in development and cancer. However, whether miRNAs regulate hepatocyte proliferation during liver regeneration is unknown. We addressed this question by performing 2/3 partial hepatectomy (2/3 PH) on mice with hepatocyte-specific inactivation of DiGeorge syndrome critical region gene 8 (DGCR8), an essential component of the miRNA processing pathway. Hepatocytes of these mice were miRNA-deficient and exhibited a delay in cell cycle progression involving the G(1) to S phase transition. Examination of livers of wildtype mice after 2/3 PH revealed differential expression of a subset of miRNAs, notably an induction of miR-21 and repression of miR-378. We further discovered that miR-21 directly inhibits Btg2, a cell cycle inhibitor that prevents activation of forkhead box M1 (FoxM1), which is essential for DNA synthesis in hepatocytes after 2/3 PH. In addition, we found that miR-378 directly inhibits ornithine decarboxylase (Odc1), which is known to promote DNA synthesis in hepatocytes after 2/3 PH. Our results show that miRNAs are critical regulators of hepatocyte proliferation during liver regeneration. Because these miRNAs and target gene interactions are conserved, our findings may also be relevant to human liver regeneration.

Tropical forest loss and its multitrophic effects on insect herbivory.

PubMed

Morante-Filho, José Carlos; Arroyo-Rodríguez, Víctor; Lohbeck, Madelon; Tscharntke, Teja; Faria, Deborah

2016-12-01

Forest loss threatens biodiversity, but its potential effects on multitrophic ecological interactions are poorly understood. Insect herbivory depends on complex bottom-up (e.g., resource availability and plant antiherbivore defenses) and top-down forces (e.g., abundance of predators and herbivorous), but its determinants in human-altered tropical landscapes are largely unknown. Using structural equation models, we assessed the direct and indirect effects of forest loss on insect herbivory in 40 landscapes (115 ha each) from two regions with contrasting land-use change trajectories in the Brazilian Atlantic rainforest. We considered landscape forest cover as an exogenous predictor and (1) forest structure, (2) abundance of predators (birds and arthropods), and (3) abundance of herbivorous arthropods as endogenous predictors of insect leaf damage. From 12 predicted pathways, 11 were significant and showed that (1) leaf damage increases with forest loss (direct effect); (2) leaf damage increases with forest loss through the simplification of vegetation structure and its associated dominance of herbivorous insects (indirect effect); and further demonstrate (3) a lack of top-down control of herbivores by predators (birds and arthropods). We conclude that forest loss favors insect herbivory by undermining the bottom-up control (presumably reduced plant antiherbivore defense mechanisms) in forests dominated by fast-growing pioneer plant species, and by improving the conditions required for herbivores proliferation. © 2016 by the Ecological Society of America.

Don't break a leg: running birds from quail to ostrich prioritise leg safety and economy on uneven terrain.

PubMed

Birn-Jeffery, Aleksandra V; Hubicki, Christian M; Blum, Yvonne; Renjewski, Daniel; Hurst, Jonathan W; Daley, Monica A

2014-11-01

Cursorial ground birds are paragons of bipedal running that span a 500-fold mass range from quail to ostrich. Here we investigate the task-level control priorities of cursorial birds by analysing how they negotiate single-step obstacles that create a conflict between body stability (attenuating deviations in body motion) and consistent leg force-length dynamics (for economy and leg safety). We also test the hypothesis that control priorities shift between body stability and leg safety with increasing body size, reflecting use of active control to overcome size-related challenges. Weight-support demands lead to a shift towards straighter legs and stiffer steady gait with increasing body size, but it remains unknown whether non-steady locomotor priorities diverge with size. We found that all measured species used a consistent obstacle negotiation strategy, involving unsteady body dynamics to minimise fluctuations in leg posture and loading across multiple steps, not directly prioritising body stability. Peak leg forces remained remarkably consistent across obstacle terrain, within 0.35 body weights of level running for obstacle heights from 0.1 to 0.5 times leg length. All species used similar stance leg actuation patterns, involving asymmetric force-length trajectories and posture-dependent actuation to add or remove energy depending on landing conditions. We present a simple stance leg model that explains key features of avian bipedal locomotion, and suggests economy as a key priority on both level and uneven terrain. We suggest that running ground birds target the closely coupled priorities of economy and leg safety as the direct imperatives of control, with adequate stability achieved through appropriately tuned intrinsic dynamics. © 2014. Published by The Company of Biologists Ltd.

Don't break a leg: running birds from quail to ostrich prioritise leg safety and economy on uneven terrain

PubMed Central

Birn-Jeffery, Aleksandra V.; Hubicki, Christian M.; Blum, Yvonne; Renjewski, Daniel; Hurst, Jonathan W.; Daley, Monica A.

2014-01-01

Cursorial ground birds are paragons of bipedal running that span a 500-fold mass range from quail to ostrich. Here we investigate the task-level control priorities of cursorial birds by analysing how they negotiate single-step obstacles that create a conflict between body stability (attenuating deviations in body motion) and consistent leg force–length dynamics (for economy and leg safety). We also test the hypothesis that control priorities shift between body stability and leg safety with increasing body size, reflecting use of active control to overcome size-related challenges. Weight-support demands lead to a shift towards straighter legs and stiffer steady gait with increasing body size, but it remains unknown whether non-steady locomotor priorities diverge with size. We found that all measured species used a consistent obstacle negotiation strategy, involving unsteady body dynamics to minimise fluctuations in leg posture and loading across multiple steps, not directly prioritising body stability. Peak leg forces remained remarkably consistent across obstacle terrain, within 0.35 body weights of level running for obstacle heights from 0.1 to 0.5 times leg length. All species used similar stance leg actuation patterns, involving asymmetric force–length trajectories and posture-dependent actuation to add or remove energy depending on landing conditions. We present a simple stance leg model that explains key features of avian bipedal locomotion, and suggests economy as a key priority on both level and uneven terrain. We suggest that running ground birds target the closely coupled priorities of economy and leg safety as the direct imperatives of control, with adequate stability achieved through appropriately tuned intrinsic dynamics. PMID:25355848

Transcription Factor Interplay between LEAFY and APETALA1/CAULIFLOWER during Floral Initiation1

PubMed Central

Zheng, Beibei; Kwaśniewska, Kamila; Thomson, Bennett

2017-01-01

The transcription factors LEAFY (LFY) and APETALA1 (AP1), together with the AP1 paralog CAULIFLOWER (CAL), control the onset of flower development in a partially redundant manner. This redundancy is thought to be mediated, at least in part, through the regulation of a shared set of target genes. However, whether these genes are independently or cooperatively regulated by LFY and AP1/CAL is currently unknown. To better understand the regulatory relationship between LFY and AP1/CAL and to obtain deeper insights into the control of floral initiation, we monitored the activity of LFY in the absence of AP1/CAL function. We found that the regulation of several known LFY target genes is unaffected by AP1/CAL perturbation, while others appear to require AP1/CAL activity. Furthermore, we obtained evidence that LFY and AP1/CAL control the expression of some genes in an antagonistic manner. Notably, these include key regulators of floral initiation such as TERMINAL FLOWER1 (TFL1), which had been previously reported to be directly repressed by both LFY and AP1. We show here that TFL1 expression is suppressed by AP1 but promoted by LFY. We further demonstrate that LFY has an inhibitory effect on flower formation in the absence of AP1/CAL activity. We propose that LFY and AP1/CAL act as part of an incoherent feed-forward loop, a network motif where two interconnected pathways or transcription factors act in opposite directions on a target gene, to control the establishment of a stable developmental program for the formation of flowers. PMID:28385730

Transcription Factor Interplay between LEAFY and APETALA1/CAULIFLOWER during Floral Initiation.

PubMed

Goslin, Kevin; Zheng, Beibei; Serrano-Mislata, Antonio; Rae, Liina; Ryan, Patrick T; Kwaśniewska, Kamila; Thomson, Bennett; Ó'Maoiléidigh, Diarmuid S; Madueño, Francisco; Wellmer, Frank; Graciet, Emmanuelle

2017-06-01

The transcription factors LEAFY (LFY) and APETALA1 (AP1), together with the AP1 paralog CAULIFLOWER (CAL), control the onset of flower development in a partially redundant manner. This redundancy is thought to be mediated, at least in part, through the regulation of a shared set of target genes. However, whether these genes are independently or cooperatively regulated by LFY and AP1/CAL is currently unknown. To better understand the regulatory relationship between LFY and AP1/CAL and to obtain deeper insights into the control of floral initiation, we monitored the activity of LFY in the absence of AP1/CAL function. We found that the regulation of several known LFY target genes is unaffected by AP1/CAL perturbation, while others appear to require AP1/CAL activity. Furthermore, we obtained evidence that LFY and AP1/CAL control the expression of some genes in an antagonistic manner. Notably, these include key regulators of floral initiation such as TERMINAL FLOWER1 ( TFL1 ), which had been previously reported to be directly repressed by both LFY and AP1. We show here that TFL1 expression is suppressed by AP1 but promoted by LFY. We further demonstrate that LFY has an inhibitory effect on flower formation in the absence of AP1/CAL activity. We propose that LFY and AP1/CAL act as part of an incoherent feed-forward loop, a network motif where two interconnected pathways or transcription factors act in opposite directions on a target gene, to control the establishment of a stable developmental program for the formation of flowers. © 2017 American Society of Plant Biologists. All Rights Reserved.

Fast grasping of unknown objects using principal component analysis

NASA Astrophysics Data System (ADS)

Lei, Qujiang; Chen, Guangming; Wisse, Martijn

2017-09-01

Fast grasping of unknown objects has crucial impact on the efficiency of robot manipulation especially subjected to unfamiliar environments. In order to accelerate grasping speed of unknown objects, principal component analysis is utilized to direct the grasping process. In particular, a single-view partial point cloud is constructed and grasp candidates are allocated along the principal axis. Force balance optimization is employed to analyze possible graspable areas. The obtained graspable area with the minimal resultant force is the best zone for the final grasping execution. It is shown that an unknown object can be more quickly grasped provided that the component analysis principle axis is determined using single-view partial point cloud. To cope with the grasp uncertainty, robot motion is assisted to obtain a new viewpoint. Virtual exploration and experimental tests are carried out to verify this fast gasping algorithm. Both simulation and experimental tests demonstrated excellent performances based on the results of grasping a series of unknown objects. To minimize the grasping uncertainty, the merits of the robot hardware with two 3D cameras can be utilized to suffice the partial point cloud. As a result of utilizing the robot hardware, the grasping reliance is highly enhanced. Therefore, this research demonstrates practical significance for increasing grasping speed and thus increasing robot efficiency under unpredictable environments.

Forensic DNA Phenotyping: Predicting human appearance from crime scene material for investigative purposes.

PubMed

Kayser, Manfred

2015-09-01

Forensic DNA Phenotyping refers to the prediction of appearance traits of unknown sample donors, or unknown deceased (missing) persons, directly from biological materials found at the scene. "Biological witness" outcomes of Forensic DNA Phenotyping can provide investigative leads to trace unknown persons, who are unidentifiable with current comparative DNA profiling. This intelligence application of DNA marks a substantially different forensic use of genetic material rather than that of current DNA profiling presented in the courtroom. Currently, group-specific pigmentation traits are already predictable from DNA with reasonably high accuracies, while several other externally visible characteristics are under genetic investigation. Until individual-specific appearance becomes accurately predictable from DNA, conventional DNA profiling needs to be performed subsequent to appearance DNA prediction. Notably, and where Forensic DNA Phenotyping shows great promise, this is on a (much) smaller group of potential suspects, who match the appearance characteristics DNA-predicted from the crime scene stain or from the deceased person's remains. Provided sufficient funding being made available, future research to better understand the genetic basis of human appearance will expectedly lead to a substantially more detailed description of an unknown person's appearance from DNA, delivering increased value for police investigations in criminal and missing person cases involving unknowns. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Parametric system identification of catamaran for improving controller design

NASA Astrophysics Data System (ADS)

Timpitak, Surasak; Prempraneerach, Pradya; Pengwang, Eakkachai

2018-01-01

This paper presents an estimation of simplified dynamic model for only surge- and yaw- motions of catamaran by using system identification (SI) techniques to determine associated unknown parameters. These methods will enhance the performance of designing processes for the motion control system of Unmanned Surface Vehicle (USV). The simulation results demonstrate an effective way to solve for damping forces and to determine added masses by applying least-square and AutoRegressive Exogenous (ARX) methods. Both methods are then evaluated according to estimated parametric errors from the vehicle’s dynamic model. The ARX method, which yields better estimated accuracy, can then be applied to identify unknown parameters as well as to help improving a controller design of a real unmanned catamaran.

Adaptive Sliding Mode Control of Dynamic Systems Using Double Loop Recurrent Neural Network Structure.

PubMed

Fei, Juntao; Lu, Cheng

2018-04-01

In this paper, an adaptive sliding mode control system using a double loop recurrent neural network (DLRNN) structure is proposed for a class of nonlinear dynamic systems. A new three-layer RNN is proposed to approximate unknown dynamics with two different kinds of feedback loops where the firing weights and output signal calculated in the last step are stored and used as the feedback signals in each feedback loop. Since the new structure has combined the advantages of internal feedback NN and external feedback NN, it can acquire the internal state information while the output signal is also captured, thus the new designed DLRNN can achieve better approximation performance compared with the regular NNs without feedback loops or the regular RNNs with a single feedback loop. The new proposed DLRNN structure is employed in an equivalent controller to approximate the unknown nonlinear system dynamics, and the parameters of the DLRNN are updated online by adaptive laws to get favorable approximation performance. To investigate the effectiveness of the proposed controller, the designed adaptive sliding mode controller with the DLRNN is applied to a -axis microelectromechanical system gyroscope to control the vibrating dynamics of the proof mass. Simulation results demonstrate that the proposed methodology can achieve good tracking property, and the comparisons of the approximation performance between radial basis function NN, RNN, and DLRNN show that the DLRNN can accurately estimate the unknown dynamics with a fast speed while the internal states of DLRNN are more stable.

Bidirectional control of social hierarchy by synaptic efficacy in medial prefrontal cortex.

PubMed

Wang, Fei; Zhu, Jun; Zhu, Hong; Zhang, Qi; Lin, Zhanmin; Hu, Hailan

2011-11-04

Dominance hierarchy has a profound impact on animals' survival, health, and reproductive success, but its neural circuit mechanism is virtually unknown. We found that dominance ranking in mice is transitive, relatively stable, and highly correlates among multiple behavior measures. Recording from layer V pyramidal neurons of the medial prefrontal cortex (mPFC) showed higher strength of excitatory synaptic inputs in mice with higher ranking, as compared with their subordinate cage mates. Furthermore, molecular manipulations that resulted in an increase and decrease in the synaptic efficacy in dorsal mPFC neurons caused an upward and downward movement in the social rank, respectively. These results provide direct evidence for mPFC's involvement in social hierarchy and suggest that social rank is plastic and can be tuned by altering synaptic strength in mPFC pyramidal cells.

Commercial absorption chiller models for evaluation of control strategies

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

Koeppel, E.A.; Klein, S.A.; Mitchell, J.W.

1995-08-01

A steady-state computer simulation model of a direct fired double-effect water-lithium bromide absorption chiller in the parallel-flow configuration was developed from first principles. Unknown model parameters such as heat transfer coefficients were determined by matching the model`s calculated state points and coefficient of performance (COP) against nominal full-load operating data and COPs obtained from a manufacturer`s catalog. The model compares favorably with the manufacturer`s performance ratings for varying water circuit (chilled and cooling) temperatures at full load conditions and for chiller part-load performance. The model was used (1) to investigate the effect of varying the water circuit flow rates withmore » the chiller load and (2) to optimize chiller part-load performance with respect to the distribution and flow of the weak solution.« less

Application of Novel Lateral Tire Force Sensors to Vehicle Parameter Estimation of Electric Vehicles.

PubMed

Nam, Kanghyun

2015-11-11

This article presents methods for estimating lateral vehicle velocity and tire cornering stiffness, which are key parameters in vehicle dynamics control, using lateral tire force measurements. Lateral tire forces acting on each tire are directly measured by load-sensing hub bearings that were invented and further developed by NSK Ltd. For estimating the lateral vehicle velocity, tire force models considering lateral load transfer effects are used, and a recursive least square algorithm is adapted to identify the lateral vehicle velocity as an unknown parameter. Using the estimated lateral vehicle velocity, tire cornering stiffness, which is an important tire parameter dominating the vehicle's cornering responses, is estimated. For the practical implementation, the cornering stiffness estimation algorithm based on a simple bicycle model is developed and discussed. Finally, proposed estimation algorithms were evaluated using experimental test data.

Overexpression of Wnt5a in mouse epidermis causes no psoriasis phenotype but an impairment of hair follicle anagen development.

PubMed

Zhu, Xuming; Wu, Yumei; Huang, Sixia; Chen, Yingwei; Tao, Yixin; Wang, Yushu; He, Shigang; Shen, Sanbing; Wu, Ji; Guo, Xizhi; Li, Baojie; He, Lin; Ma, Gang

2014-12-01

Increased Wnt5a expression has been observed in psoriatic plaques. However, whether Wnt5a overexpression directly causes psoriasis is unknown. In this study, we generated transgenic (TG) mice with epidermal Wnt5a overexpression under the control of the human K14 promoter. The skin of Wnt5a TG mice was not psoriatic, but characterized with normal proliferation and homeostasis of epidermis. Instead, these TG mice displayed impaired hair follicle transition from telogen to anagen, most likely due to impaired canonical Wnt signalling. These results suggest that increased Wnt5a expression alone is inadequate to induce psoriasis in the skin and possible involvement of Wnt5a in hair follicle cycling. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Geometric control of capillary architecture via cell-matrix mechanical interactions.

PubMed

Sun, Jian; Jamilpour, Nima; Wang, Fei-Yue; Wong, Pak Kin

2014-03-01

Capillary morphogenesis is a multistage, multicellular activity that plays a pivotal role in various developmental and pathological situations. In-depth understanding of the regulatory mechanism along with the capability of controlling the morphogenic process will have direct implications on tissue engineering and therapeutic angiogenesis. Extensive research has been devoted to elucidate the biochemical factors that regulate capillary morphogenesis. The roles of geometric confinement and cell-matrix mechanical interactions on the capillary architecture, nevertheless, remain largely unknown. Here, we show geometric control of endothelial network topology by creating physical confinements with microfabricated fences and wells. Decreasing the thickness of the matrix also results in comparable modulation of the network architecture, supporting the boundary effect is mediated mechanically. The regulatory role of cell-matrix mechanical interaction on the network topology is further supported by alternating the matrix stiffness by a cell-inert PEG-dextran hydrogel. Furthermore, reducing the cell traction force with a Rho-associated protein kinase inhibitor diminishes the boundary effect. Computational biomechanical analysis delineates the relationship between geometric confinement and cell-matrix mechanical interaction. Collectively, these results reveal a mechanoregulation scheme of endothelial cells to regulate the capillary network architecture via cell-matrix mechanical interactions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Interactions between aromatase (estrogen synthase) and dopamine in the control of male sexual behavior in quail.

PubMed

Balthazart, Jacques; Baillien, Michelle; Ball, Gregory F

2002-05-01

In male quail, like in other vertebrates including rodents, testosterone acting especially through its estrogenic metabolites is necessary for the activation of male sexual behavior. Also, the administration of dopamine agonists and antagonists profoundly influences male sexual behavior. How the steroid-sensitive neural network and dopamine interact physiologically, remains largely unknown. It is often implicitly assumed that testosterone or its metabolite estradiol, stimulates male sexual behavior via the modification of dopaminergic transmission. We have now identified in quail two possible ways in which dopamine could potentially affect sexual behavior by modulating the aromatization of testosterone into an estrogen. One is a long-acting mechanism that presumably involves the modification of dopaminergic transmission followed by the alteration of the genomic expression of aromatase. The other is a more rapid mechanism that does not appear to be dopamine receptor-mediated and may involve a direct interaction of dopamine with aromatase (possibly via substrate competition). We review here the experimental data supporting the existence of these controls of aromatase activity by dopamine and discuss the possible contribution of these controls to the activation of male sexual behavior.

Protocol for a Controlled Experiment to Identify the Causal Role of Acute Alcohol Consumption in Condomless Sex among HIV-Positive MSM: Study Procedures, Ethical Considerations, and Implications for HIV Prevention.

PubMed

Shuper, Paul A; Joharchi, Narges; Rehm, Jürgen

2016-01-01

Although alcohol consumption is frequently perceived as a driver of condomless sex and subsequent HIV acquisition, the causal nature of this relationship remains unclear, and little is known about alcohol's direct versus indirect impact on the sexual risk dynamics of those who are HIV-positive. To address this gap, we present the protocol for an in-progress NIAAA-funded controlled experiment, wherein a sample of HIV-positive men-who-have-sex-with-men (MSM) undergoes an alcohol consumption manipulation (alcohol/placebo/control) and sexual arousal induction (sexually aroused/non-aroused), and then reports intentions to engage in condom-protected and condomless sexual acts with hypothetical sexual partners differing in HIV serostatus (HIV+/HIV-/HIV status unknown), condom use preference (use/don't use/not stated), and physical attractiveness (attractive/unattractive). Study outcomes will identify alcohol's impact on HIV-positive MSM's condomless sex intentions in the context of experimentally-manipulated factors as well as risk-relevant personality traits and alcohol-related expectancies. Detailed experimental procedures, ethical considerations, and potential implications for HIV prevention are discussed.

Effect of a mind-body therapeutic program for infertile women repeating in vitro fertilization treatment on uncertainty, anxiety, and implantation rate.

PubMed

Kim, Miok; Kim, Sue; Chang, Soon-bok; Yoo, Ji-Soo; Kim, Hee Kyung; Cho, Jung Hyun

2014-03-01

The study aimed to develop a mind-body therapeutic program and evaluate its effects on mitigating uncertainty, anxiety, and implantation rate of second-trial in vitro fertilization (IVF) women. This study employed a nonequivalent control group nonsynchronized design. The conceptual framework and program content were developed from a preliminary survey of eight infertile women and the extensive review of the literature. Program focuses on three uncertainty-induced anxieties in infertile women: cognitive, emotional, and biological responses. To evaluate the effect of the intervention, the infertile women with unknown cause preparing for a second IVF treatment were sampled at convenience (26 experimental and 24 control). The experimental group in the study showed greater decrease in uncertainty and anxiety in premeasurements and postmeasurements than the control group did. However, no statistically significant differences in the implantation rate between groups were observed. This study is meaningful as the first intervention program for alleviating uncertainty and anxiety provided during the IVF treatment process. The positive effects of the mind-body therapeutic program in alleviating both uncertainty and anxiety have direct meaning for clinical applications. Copyright © 2014. Published by Elsevier B.V.

Reduced Specificity of Personal Goals and Explanations for Goal Attainment in Major Depression

PubMed Central

Dickson, Joanne M.; Moberly, Nicholas J.

2013-01-01

Objectives Overgeneralization has been investigated across many domains of cognitive functioning in major depression, including the imagination of future events. However, it is unknown whether this phenomenon extends to representations of personal goals, which are important in structuring long-term behaviour and providing meaning in life. Furthermore, it is not clear whether depressed individuals provide less specific explanations for and against goal attainment. Method Clinically depressed individuals and controls generated personally important approach and avoidance goals, and then generated explanations why they would and would not achieve these goals. Goals and causal explanations were subsequently coded as either specific or general. Results Compared to controls, depressed individuals did not generate significantly fewer goals or causal explanations for or against goal attainment. However, compared to controls, depressed individuals generated less specific goals, less specific explanations for approach (but not avoidance) goal attainment, and less specific explanations for goal nonattainment. Significance Our results suggest that motivational deficits in depression may stem partly from a reduction in the specificity of personal goal representations and related cognitions that support goal-directed behaviour. Importantly, the findings have the potential to inform the ongoing development of psychotherapeutic approaches in the treatment of depression. PMID:23691238

Motor competence and characteristics within the preschool environment.

PubMed

True, Larissa; Pfeiffer, Karin Allor; Dowda, Marsha; Williams, Harriet G; Brown, William H; O'Neill, Jennifer R; Pate, Russell R

2017-08-01

Environmental characteristics within preschools that influence children's motor competence are largely unknown. The purpose of the present study was to examine the contribution of various preschool environmental characteristics to children's locomotor, object control, and total gross motor scores. Cross-sectional, observational study of 3-5 year-old children (n=229) from 22 preschools in South Carolina. The Children's Activity and Movement in Preschool Study (CHAMPS) Motor Skills Protocol assessed MC. Preschool directors provided information regarding policies and practices. The research team measured playgrounds and classrooms, and the Early Childhood Environment Rating Scale-Revised assessed preschool quality. Time spent in open space and electronic media use were also assessed using direct observation. The aforementioned variables predicted children's object control, locomotor, and total gross motor scores. Classroom size/child ratio, teacher education, playground size, electronic media use, and trips to outside organizations emerged as significant predictors of locomotor score and total motor score. The object control model was non-significant. Preschools may be able to promote motor competence by allowing children more time in open spaces, structured activity experiences, and by expanding existing outdoor playground space whenever possible. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Effects of intravenous furosemide on mucociliary transport and rheological properties of patients under mechanical ventilation

PubMed Central

Kondo, Cláudia Seiko; Macchionne, Mariângela; Nakagawa, Naomi Kondo; de Carvalho, Carlos Roberto Ribeiro; King, Malcolm; Saldiva, Paulo Hilário Nascimento; Lorenzi-Filho, Geraldo

2002-01-01

The use of intravenous (IV) furosemide is common practice in patients under mechanical ventilation (MV), but its effects on respiratory mucus are largely unknown. Furosemide can affect respiratory mucus either directly through inhibition of the NaK(Cl)2 co-transporter on the basolateral surface of airway epithelium or indirectly through increased diuresis and dehydration. We investigated the physical properties and transportability of respiratory mucus obtained from 26 patients under MV distributed in two groups, furosemide (n = 12) and control (n = 14). Mucus collection was done at 0, 1, 2, 3 and 4 hours. The rheological properties of mucus were studied with a microrheometer, and in vitro mucociliary transport (MCT) (frog palate), contact angle (CA) and cough clearance (CC) (simulated cough machine) were measured. After the administration of furosemide, MCT decreased by 17 ± 19%, 24 ± 11%, 18 ± 16% and 18 ± 13% at 1, 2, 3 and 4 hours respectively, P < 0.001 compared with control. In contrast, no significant changes were observed in the control group. The remaining parameters did not change significantly in either group. Our results support the hypothesis that IV furosemide might acutely impair MCT in patients under MV. PMID:11940271

Adaptive Control Based Harvesting Strategy for a Predator-Prey Dynamical System.

PubMed

Sen, Moitri; Simha, Ashutosh; Raha, Soumyendu

2018-04-23

This paper deals with designing a harvesting control strategy for a predator-prey dynamical system, with parametric uncertainties and exogenous disturbances. A feedback control law for the harvesting rate of the predator is formulated such that the population dynamics is asymptotically stabilized at a positive operating point, while maintaining a positive, steady state harvesting rate. The hierarchical block strict feedback structure of the dynamics is exploited in designing a backstepping control law, based on Lyapunov theory. In order to account for unknown parameters, an adaptive control strategy has been proposed in which the control law depends on an adaptive variable which tracks the unknown parameter. Further, a switching component has been incorporated to robustify the control performance against bounded disturbances. Proofs have been provided to show that the proposed adaptive control strategy ensures asymptotic stability of the dynamics at a desired operating point, as well as exact parameter learning in the disturbance-free case and learning with bounded error in the disturbance prone case. The dynamics, with uncertainty in the death rate of the predator, subjected to a bounded disturbance has been simulated with the proposed control strategy.

On the functional relevance of frontal cortex for passive and voluntarily controlled bistable vision.

PubMed

de Graaf, Tom A; de Jong, Maartje C; Goebel, Rainer; van Ee, Raymond; Sack, Alexander T

2011-10-01

In bistable vision, one constant ambiguous stimulus leads to 2 alternating conscious percepts. This perceptual switching occurs spontaneously but can also be influenced through voluntary control. Neuroimaging studies have reported that frontal regions are activated during spontaneous perceptual switches, leading some researchers to suggest that frontal regions causally induce perceptual switches. But the opposite also seems possible: frontal activations may themselves be caused by spontaneous switches. Classically implicated in attentional processes, these same regions are also candidates for the origins of voluntary control over bistable vision. Here too, it remains unknown whether frontal cortex is actually functionally relevant. It is even possible that spontaneous perceptual switches and voluntarily induced switches are mediated by the same top-down mechanisms. To directly address these issues, we here induced "virtual lesions," with transcranial magnetic stimulation, in frontal, parietal, and 2 lower level visual cortices using an established ambiguous structure-from-motion stimulus. We found that dorsolateral prefrontal cortex was causally relevant for voluntary control over perceptual switches. In contrast, we failed to find any evidence for an active role of frontal cortex in passive bistable vision. Thus, it seems the same pathway used for willed top-down modulation of bistable vision is not used during passive bistable viewing.

Cervical neoplasia and human papilloma virus infection in prostitutes.

PubMed

Gitsch, G; Kainz, C; Reinthaller, A; Kopp, W; Tatra, G; Breitenecker, G

1991-12-01

To evaluate the prevalence and incidence of PAP smears indicating cervical dysplasia as well as human papillomavirus (HPV) infection in prostitutes. Prevalence and incidence study of cervical dysplasia and HPV infection in prostitutes. For detection and typing of HPV-DNA In Situ Hybridisation (ISH) was performed in tissue samples with CIN gained by colposcopically directed punch biopsies. Second Department of Obstetrics and Gynecology, University of Vienna Medical School and STD Clinic of the Public Health Office, Vienna. Registered prostitutes attending the STD Clinic of the Public Health Office and a control group. 978 prostitutes and 5493 women with unknown cytological anamnesis were compared. Frequency of positive PAP smears was significantly higher in prostitutes (6.13% versus 1.43%). To determine the pick-up rate of cervical dysplasia during one year after negative cytology we compared 722 prostitutes and 3162 controls. Prostitutes showed a significant higher dysplasia pick-up rate (3.05% to 1.07%) compared with controls. HPV detection rate in prostitutes was similar to that in the control group. The distribution of HPV types revealed a higher frequency of "high risk" HPV 16/18 and 31/33 in prostitutes. The results demonstrate a higher incidence and prevalence of cervical dysplasia in prostitutes and therefore suggest regular cervical PAP smear screening in registered prostitutes twice a year.

PBMC telomerase activity, but not leukocyte telomere length, correlates with hippocampal volume in major depression

PubMed Central

Wolkowitz, Owen M.; Mellon, Synthia H.; Lindqvist, Daniel; Epel, Elissa S.; Blackburn, Elizabeth H.; Lin, Jue; Reus, Victor I.; Burke, Heather; Rosser, Rebecca; Mahan, Laura; Mackin, Scott; Yang, Tony; Weiner, Michael; Mueller, Susanne

2015-01-01

Accelerated cell aging, indexed in peripheral leukocytes by telomere length and in peripheral blood mononuclear cells (PBMCs) by telomerase activity, has been reported in several studies of major depressive disorder (MDD). However, the relevance of these peripheral measures for brain indices that are presumably more directly related to MDD pathophysiology is unknown. In this study, we explored the relationship between PBMC telomerase activity and leukocyte telomere length and magnetic resonance imaging-estimated hippocampal volume in un-medicated depressed individuals and healthy controls. We predicted that, to the extent peripheral and central telomerase activity are directly related, PBMC telomerase activity would be positively correlated with hippocampal volume, perhaps due to hippocampal telomerase-associated neurogenesis, neuroprotection or neurotrophic facilitation, and that this effect would be clearer in individuals with increased PBMC telomerase activity, as previously reported in un-medicated MDD. We did not have specific hypotheses regarding the relationship between leukocyte telomere length and hippocampal volume, due to conflicting reports in the published literature. We found, in 25 un-medicated MDD subjects, that PBMC telomerase activity was significantly positively correlated with hippocampal volume; this relationship was not observed in 18 healthy controls. Leukocyte telomere length was not significantly related to hippocampal volume in either group (19 unmedicated MDD subjects and 17 healthy controls). Although the nature of the relationship between peripheral telomerase activity and telomere length and the hippocampus is unclear, these preliminary data are consistent with the possibility that PBMC telomerase activity indexes, and may provide a novel window into, hippocampal neuroprotection and/or neurogenesis in MDD. PMID:25773002

Control of alternative splicing by forskolin through hnRNP K during neuronal differentiation

PubMed Central

Cao, Wenguang; Razanau, Aleh; Feng, Dairong; Lobo, Vincent G.; Xie, Jiuyong

2012-01-01

The molecular basis of cell signal-regulated alternative splicing at the 3′ splice site remains largely unknown. We isolated a protein kinase A-responsive ribonucleic acid (RNA) element from a 3′ splice site of the synaptosomal-associated protein 25 (Snap25) gene for forskolin-inhibited splicing during neuronal differentiation of rat pheochromocytoma PC12 cells. The element binds specifically to heterogeneous nuclear ribonucleo protein (hnRNP) K in a phosphatase-sensitive way, which directly competes with the U2 auxiliary factor U2AF65, an essential component of early spliceosomes. Transcripts with similarly localized hnRNP K target motifs upstream of alternative exons are enriched in genes often associated with neurological diseases. We show that such motifs upstream of the Runx1 exon 6 also bind hnRNP K, and importantly, hnRNP K is required for forskolin-induced repression of the exon. Interestingly, this exon encodes the peptide domain that determines the switch of the transcriptional repressor/activator activity of Runx1, a change known to be critical in specifying neuron lineages. Consistent with an important role of the target genes in neurons, knocking down hnRNP K severely disrupts forskolin-induced neurite growth. Thus, through hnRNP K, the neuronal differentiation stimulus forskolin targets a critical 3′ splice site component of the splicing machinery to control alternative splicing of crucial genes. This also provides a regulated direct competitor of U2AF65 for cell signal control of 3′ splice site usage. PMID:22684629

How to Decide? Multi-Objective Early-Warning Monitoring Networks for Water Suppliers

NASA Astrophysics Data System (ADS)

Bode, Felix; Loschko, Matthias; Nowak, Wolfgang

2015-04-01

Groundwater is a resource for drinking water and hence needs to be protected from contaminations. However, many well catchments include an inventory of known and unknown risk sources, which cannot be eliminated, especially in urban regions. As a matter of risk control, all these risk sources should be monitored. A one-to-one monitoring situation for each risk source would lead to a cost explosion and is even impossible for unknown risk sources. However, smart optimization concepts could help to find promising low-cost monitoring network designs. In this work we develop a concept to plan monitoring networks using multi-objective optimization. Our considered objectives are to maximize the probability of detecting all contaminations, to enhance the early warning time before detected contaminations reach the drinking water well, and to minimize the installation and operating costs of the monitoring network. Using multi-objectives optimization, we avoid the problem of having to weight these objectives to a single objective-function. These objectives are clearly competing, and it is impossible to know their mutual trade-offs beforehand - each catchment differs in many points and it is hardly possible to transfer knowledge between geological formations and risk inventories. To make our optimization results more specific to the type of risk inventory in different catchments we do risk prioritization of all known risk sources. Due to the lack of the required data, quantitative risk ranking is impossible. Instead, we use a qualitative risk ranking to prioritize the known risk sources for monitoring. Additionally, we allow for the existence of unknown risk sources that are totally uncertain in location and in their inherent risk. Therefore, they can neither be located nor ranked. Instead, we represent them by a virtual line of risk sources surrounding the production well. We classify risk sources into four different categories: severe, medium and tolerable for known risk sources and an extra category for the unknown ones. With that, early warning time and detection probability become individual objectives for each risk class. Thus, decision makers can identify monitoring networks valid for controlling the top risk sources, and evaluate the capabilities (or search for least-cost upgrades) to also cover moderate, tolerable and unknown risk sources. Monitoring networks, which are valid for the remaining risk also cover all other risk sources, but only with a relatively poor early-warning time. The data provided for the optimization algorithm are calculated in a preprocessing step by a flow and transport model. It simulates, which potential contaminant plumes from the risk sources would be detectable where and when by all possible candidate positions for monitoring wells. Uncertainties due to hydro(geo)logical phenomena are taken into account by Monte-Carlo simulations. These include uncertainty in ambient flow direction of the groundwater, uncertainty of the conductivity field, and different scenarios for the pumping rates of the production wells. To avoid numerical dispersion during the transport simulations, we use particle-tracking random walk methods when simulating transport.

An Evidence-Based Review Literature About Risk Indicators and Management of Unknown-Origin Xerostomia

PubMed Central

Agha-Hosseini, Farzaneh; Moosavi, Mahdieh-Sadat

2013-01-01

This evidence-based article reviews risk indicators and management of unknown-origin xerostomia. Xerostomia and hyposalivation refer to different aspects of dry mouth. Xerostomia is a subjective sensation of dry mouth, whilst hyposalivation is defined as an objective assessment of reduced salivary flow rate. About 30% of the elderly (65 years and older) experience xerostomia and hyposalivation. Structural and functional factors, or both may lead to salivary gland dysfunction. The EBM literature search was conducted by using the medical literature database MEDLINE via PubMed and OvidMedline search engines. Results were limited to English language articles (1965 to present) including clinical trials (CT), randomized controlled trials (RCT), systematic reviews and review articles. Case control or cohort studies were included for the etiology. Neuropathic etiology such as localized oral alteration of thermal sensations, saliva composition change (for example higher levels of K, Cl, Ca, IgA, amylase, calcium, PTH and cortisol), lower levels of estrogen and progesterone, smaller salivary gland size, and illnesses such as lichen planus, are risk indicators for unknown-origin xerostomia. The management is palliative and preventative. Management of symptoms includes drug administration (systemic secretogogues, saliva substitutes and bile secretion-stimulator), night guard, diet and habit modifications. Other managements may be indicated to treat adverse effects. Neuropathic etiology, saliva composition change, smaller salivary gland size, and illnesses such as oral lichen planus can be suggestive causes for unknown-origin xerostomia. However, longitudinal studies will be important to elucidate the causes of unknown-origin xerostomia. PMID:25512755

Familiarity and face emotion recognition in patients with schizophrenia.

PubMed

Lahera, Guillermo; Herrera, Sara; Fernández, Cristina; Bardón, Marta; de los Ángeles, Victoria; Fernández-Liria, Alberto

2014-01-01

To assess the emotion recognition in familiar and unknown faces in a sample of schizophrenic patients and healthy controls. Face emotion recognition of 18 outpatients diagnosed with schizophrenia (DSM-IVTR) and 18 healthy volunteers was assessed with two Emotion Recognition Tasks using familiar faces and unknown faces. Each subject was accompanied by 4 familiar people (parents, siblings or friends), which were photographed by expressing the 6 Ekman's basic emotions. Face emotion recognition in familiar faces was assessed with this ad hoc instrument. In each case, the patient scored (from 1 to 10) the subjective familiarity and affective valence corresponding to each person. Patients with schizophrenia not only showed a deficit in the recognition of emotions on unknown faces (p=.01), but they also showed an even more pronounced deficit on familiar faces (p=.001). Controls had a similar success rate in the unknown faces task (mean: 18 +/- 2.2) and the familiar face task (mean: 17.4 +/- 3). However, patients had a significantly lower score in the familiar faces task (mean: 13.2 +/- 3.8) than in the unknown faces task (mean: 16 +/- 2.4; p<.05). In both tests, the highest number of errors was with emotions of anger and fear. Subjectively, the patient group showed a lower level of familiarity and emotional valence to their respective relatives (p<.01). The sense of familiarity may be a factor involved in the face emotion recognition and it may be disturbed in schizophrenia. © 2013.

Detecting regulatory gene-environment interactions with unmeasured environmental factors.

PubMed

Fusi, Nicoló; Lippert, Christoph; Borgwardt, Karsten; Lawrence, Neil D; Stegle, Oliver

2013-06-01

Genomic studies have revealed a substantial heritable component of the transcriptional state of the cell. To fully understand the genetic regulation of gene expression variability, it is important to study the effect of genotype in the context of external factors such as alternative environmental conditions. In model systems, explicit environmental perturbations have been considered for this purpose, allowing to directly test for environment-specific genetic effects. However, such experiments are limited to species that can be profiled in controlled environments, hampering their use in important systems such as human. Moreover, even in seemingly tightly regulated experimental conditions, subtle environmental perturbations cannot be ruled out, and hence unknown environmental influences are frequent. Here, we propose a model-based approach to simultaneously infer unmeasured environmental factors from gene expression profiles and use them in genetic analyses, identifying environment-specific associations between polymorphic loci and individual gene expression traits. In extensive simulation studies, we show that our method is able to accurately reconstruct environmental factors and their interactions with genotype in a variety of settings. We further illustrate the use of our model in a real-world dataset in which one environmental factor has been explicitly experimentally controlled. Our method is able to accurately reconstruct the true underlying environmental factor even if it is not given as an input, allowing to detect genuine genotype-environment interactions. In addition to the known environmental factor, we find unmeasured factors involved in novel genotype-environment interactions. Our results suggest that interactions with both known and unknown environmental factors significantly contribute to gene expression variability. and implementation: Software available at http://pmbio.github.io/envGPLVM/. Supplementary data are available at Bioinformatics online.

32 CFR 290.7 - Procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... submitted directly to the appropriate DCAA organizational element listed in appendix B of this rule. If the appropriate DCAA organizational element is either unknown or cannot be ascertained, and the record is likely... any other identifying particulars should be provided whenever possible. DCAA organizational elements...

Pathway Profiling and Tissue Modeling Using ToxCast HTS Data

EPA Science Inventory

High-throughput screening (HTS) and high-content screening (HCS) assays are providing data-rich studies to probe and profile the direct cellular effects of thousands of chemical compounds in commerce or potentially entering the environment. In vitro profiling may compare unknown ...

Tuning into Scorpius X-1: adapting a continuous gravitational-wave search for a known binary system

NASA Astrophysics Data System (ADS)

Meadors, Grant David; Goetz, Evan; Riles, Keith

2016-05-01

We describe how the TwoSpect data analysis method for continuous gravitational waves (GWs) has been tuned for directed sources such as the low-mass X-ray binary (LMXB), Scorpius X-1 (Sco X-1). A comparison of five search algorithms generated simulations of the orbital and GW parameters of Sco X-1. Whereas that comparison focused on relative performance, here the simulations help quantify the sensitivity enhancement and parameter estimation abilities of this directed method, derived from an all-sky search for unknown sources, using doubly Fourier-transformed data. Sensitivity is shown to be enhanced when the source sky location and period are known, because we can run a fully templated search, bypassing the all-sky hierarchical stage using an incoherent harmonic sum. The GW strain and frequency, as well as the projected semi-major axis of the binary system, are recovered and uncertainty estimated, for simulated signals that are detected. Upper limits for GW strain are set for undetected signals. Applications to future GW observatory data are discussed. Robust against spin-wandering and computationally tractable despite an unknown frequency, this directed search is an important new tool for finding gravitational signals from LMXBs.

Adaptive neural network decentralized backstepping output-feedback control for nonlinear large-scale systems with time delays.

PubMed

Tong, Shao Cheng; Li, Yong Ming; Zhang, Hua-Guang

2011-07-01

In this paper, two adaptive neural network (NN) decentralized output feedback control approaches are proposed for a class of uncertain nonlinear large-scale systems with immeasurable states and unknown time delays. Using NNs to approximate the unknown nonlinear functions, an NN state observer is designed to estimate the immeasurable states. By combining the adaptive backstepping technique with decentralized control design principle, an adaptive NN decentralized output feedback control approach is developed. In order to overcome the problem of "explosion of complexity" inherent in the proposed control approach, the dynamic surface control (DSC) technique is introduced into the first adaptive NN decentralized control scheme, and a simplified adaptive NN decentralized output feedback DSC approach is developed. It is proved that the two proposed control approaches can guarantee that all the signals of the closed-loop system are semi-globally uniformly ultimately bounded, and the observer errors and the tracking errors converge to a small neighborhood of the origin. Simulation results are provided to show the effectiveness of the proposed approaches.

Optimal Fault-Tolerant Control for Discrete-Time Nonlinear Strict-Feedback Systems Based on Adaptive Critic Design.

PubMed

Wang, Zhanshan; Liu, Lei; Wu, Yanming; Zhang, Huaguang

2018-06-01

This paper investigates the problem of optimal fault-tolerant control (FTC) for a class of unknown nonlinear discrete-time systems with actuator fault in the framework of adaptive critic design (ACD). A pivotal highlight is the adaptive auxiliary signal of the actuator fault, which is designed to offset the effect of the fault. The considered systems are in strict-feedback forms and involve unknown nonlinear functions, which will result in the causal problem. To solve this problem, the original nonlinear systems are transformed into a novel system by employing the diffeomorphism theory. Besides, the action neural networks (ANNs) are utilized to approximate a predefined unknown function in the backstepping design procedure. Combined the strategic utility function and the ACD technique, a reinforcement learning algorithm is proposed to set up an optimal FTC, in which the critic neural networks (CNNs) provide an approximate structure of the cost function. In this case, it not only guarantees the stability of the systems, but also achieves the optimal control performance as well. In the end, two simulation examples are used to show the effectiveness of the proposed optimal FTC strategy.

Back-stepping active disturbance rejection control design for integrated missile guidance and control system via reduced-order ESO.

PubMed

Xingling, Shao; Honglun, Wang

2015-07-01

This paper proposes a novel composite integrated guidance and control (IGC) law for missile intercepting against unknown maneuvering target with multiple uncertainties and control constraint. First, by using back-stepping technique, the proposed IGC law design is separated into guidance loop and control loop. The unknown target maneuvers and variations of aerodynamics parameters in guidance and control loop are viewed as uncertainties, which are estimated and compensated by designed model-assisted reduced-order extended state observer (ESO). Second, based on the principle of active disturbance rejection control (ADRC), enhanced feedback linearization (FL) based control law is implemented for the IGC model using the estimates generated by reduced-order ESO. In addition, performance analysis and comparisons between ESO and reduced-order ESO are examined. Nonlinear tracking differentiator is employed to construct the derivative of virtual control command in the control loop. Third, the closed-loop stability for the considered system is established. Finally, the effectiveness of the proposed IGC law in enhanced interception performance such as smooth interception course, improved robustness against multiple uncertainties as well as reduced control consumption during initial phase are demonstrated through simulations. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Can healthy, young adults uncover personal details of unknown target individuals in their dreams?

PubMed

Smith, Carlyle

2013-01-01

We investigated the possibility that undergraduate college students could incubate dreams containing information about unknown target individuals with significant life problems. In Experiment 1, students provided two baseline dreams. They were then exposed to a photo of an individual and invited to dream about a health problem (unknown to them and the experimenter) of that individual and asked to provide two more dreams. From a class of 65 students, 12 dreamers volunteered dreams about the unknown target. In Experiment 2, 66 students were asked to dream about the life problems of a second individual, simply by looking at the photo (experimental group). Another 56 students were exposed to this same paradigm, but the photo that they examined was computer generated and the target individual was fictitious (control group). The dream elements were objectively scored with categories devised using the Hall-Van de Castle system as a model. Data were ordinal, and the nonparametric Wilcoxon signed rank test was used to examine preincubation (baseline) versus postincubation (photo examination and incubation) dream content in Experiment 1. In Experiment 2, a Z score for proportions was used to compare differences in frequency of devised categories between experimental and control groups. In Experiment 1, the comparison of postincubation dreams (all categories combined) was significant compared with the preincubation dreams (Z = 2.09, P = .036). The postincubation dreams reflected the health problem of the target. In Experiment 2, the proportion of scored categories in experimental and control groups were compared at the preincubation and postincubation conditions. The proportions of "Combined" (all categories) was very significantly larger at the postincubation condition (Z = 6.27, P < .00001). The groups did not differ at the preincubation condition (Z = -1.12, not significant). Individual postincubation condition comparisons of the experimental versus control groups revealed significant differences in three of the devised scoring categories, ranging from P < .002 to P < .05. There were no experimental versus control preincubation differences. The postincubation dreams of the experimental group were related to the problems of the target individual. Young, healthy adults are capable of dreaming details about the personal problems of an unknown individual simply by examining a picture of the target and then planning to dream about that individual's problems. Copyright © 2013 Elsevier Inc. All rights reserved.

Interactions between the visual and the magnetoreception system: different effects of bichromatic light regimes on the directional behavior of migratory birds.

PubMed

Wiltschko, Roswitha; Dehe, Lars; Gehring, Dennis; Thalau, Peter; Wiltschko, Wolfgang

2013-01-01

When magnetic compass orientation of migratory robins was tested, the birds proved well oriented under low intensity monochromatic light of shorter wavelengths up to 565 nm green; from 583 nm yellow onward, they were disoriented. In the present study, we tested robins under bichromatic lights composed (1) of 424 nm blue and 565 nm green and (2) of 565 nm green and 583 nm yellow at two intensities. Under dim blue-green light with a total quantal flux of ca. 8 × 10(15)quanta/sm(2), the birds were well oriented in their migratory direction by their inclination compass; under blue-green light of twice this intensity, their orientation became axial. In both cases, the magnetic directional information was mediated by the radical pair processes in the eye. When green and yellow light were combined, however, the nature of the behavior changed. Under green-yellow light of the higher intensity, the birds showed a 'fixed direction' response that was polar, no longer controlled by the normal inclination compass; under dim green-yellow light, the response became axial. Under these two light conditions, the respective directional information was mediated by the magnetite-based receptors in the skin of the upper beak. Apparently, yellow light leads to a change from one magnetoreception system to the other. How this change is effected is still unknown; it appears to reflect complex interactions between the visual and the two magnetoreception systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Increased Depression and Anxiety Symptoms are Associated with More Breakdowns in Cognitive Control to Cocaine Cues in Veterans with Cocaine Use Disorder.

PubMed

DiGirolamo, Gregory J; Gonzalez, Gerardo; Smelson, David; Guevremont, Nathan; Andre, Michael I; Patnaik, Pooja O; Zaniewski, Zachary R

2017-01-01

Cue-elicited craving is a clinically important aspect of cocaine addiction directly linked to cognitive control breakdowns and relapse to cocaine-taking behavior. However, whether craving drives breakdowns in cognitive control toward cocaine cues in veterans, who experience significantly more co-occurring mood disorders, is unknown. The present study tests whether veterans have breakdowns in cognitive control because of cue-elicited craving or current anxiety or depression symptoms. Twenty-four veterans with cocaine use disorder were cue-exposed, then tested on an antisaccade task in which participants were asked to control their eye movements toward cocaine or neutral cues by looking away from the cue. The relationship among cognitive control breakdowns (as measured by eye errors), cue-induced craving (changes in self-reported craving following cocaine cue exposure), and mood measures (depression and anxiety) was investigated. Veterans made significantly more errors toward cocaine cues than neutral cues. Depression and anxiety scores, but not cue-elicited craving, were significantly associated with increased subsequent errors toward cocaine cues for veterans. Increased depression and anxiety are specifically related to more cognitive control breakdowns toward cocaine cues in veterans. Depression and anxiety must be considered further in the etiology and treatment of cocaine use disorder in veterans. Furthermore, treating depression and anxiety as well, rather than solely alleviating craving levels, may prove a more effective combined treatment option in veterans with cocaine use disorder.

Rif1 acts through Protein Phosphatase 1 but independent of replication timing to suppress telomere extension in budding yeast.

PubMed

Kedziora, Sylwia; Gali, Vamsi K; Wilson, Rosemary H C; Clark, Kate R M; Nieduszynski, Conrad A; Hiraga, Shin-Ichiro; Donaldson, Anne D

2018-05-04

The Rif1 protein negatively regulates telomeric TG repeat length in the budding yeast Saccharomyces cerevisiae, but how it prevents telomere over-extension is unknown. Rif1 was recently shown to control DNA replication by acting as a Protein Phosphatase 1 (PP1)-targeting subunit. Therefore, we investigated whether Rif1 controls telomere length by targeting PP1 activity. We find that a Rif1 mutant defective for PP1 interaction causes a long-telomere phenotype, similar to that of rif1Δ cells. Tethering PP1 at a specific telomere partially substitutes for Rif1 in limiting TG repeat length, confirming the importance of PP1 in telomere length control. Ablating Rif1-PP1 interaction is known to cause precocious activation of telomere-proximal replication origins and aberrantly early telomere replication. However, we find that Rif1 still limits telomere length even if late replication is forced through deletion of nearby replication origins, indicating that Rif1 can control telomere length independent of replication timing. Moreover we find that, even at a de novo telomere created after DNA synthesis during a mitotic block, Rif1-PP1 interaction is required to suppress telomere lengthening and prevent inappropriate recruitment of Tel1 kinase. Overall, our results show that Rif1 controls telomere length by recruiting PP1 to directly suppress telomerase-mediated TG repeat lengthening.

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

PubMed

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

2009-06-01

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.

An aposymbiotic primary coral polyp counteracts acidification by active pH regulation

NASA Astrophysics Data System (ADS)

Ohno, Yoshikazu; Iguchi, Akira; Shinzato, Chuya; Inoue, Mayuri; Suzuki, Atsushi; Sakai, Kazuhiko; Nakamura, Takashi

2017-01-01

Corals build their skeletons using extracellular calcifying fluid located in the tissue-skeleton interface. However, the mechanism by which corals control the transport of calcium and other ions from seawater and the mechanism of constant alkalization of calcifying fluid are largely unknown. To address these questions, we performed direct pH imaging at calcification sites (subcalicoblastic medium, SCM) to visualize active pH upregulation in live aposymbiotic primary coral polyps treated with HCl-acidified seawater. Active alkalization was observed in all individuals using vital staining method while the movement of HPTS and Alexa Fluor to SCM suggests that certain ions such as H+ could diffuse via a paracellular pathway to SCM. Among them, we discovered acid-induced oscillations in the pH of SCM (pHSCM), observed in 24% of polyps examined. In addition, we discovered acid-induced pH up-regulation waves in 21% of polyps examined, which propagated among SCMs after exposure to acidified seawater. Our results showed that corals can regulate pHSCM more dynamically than was previously believed. These observations will have important implications for determining how corals regulate pHSCM during calcification. We propose that corals can sense ambient seawater pH via their innate pH-sensitive systems and regulate pHSCM using several unknown pH-regulating ion transporters that coordinate with multicellular signaling occurring in coral tissue.

Ct shift: A novel and accurate real-time PCR quantification model for direct comparison of different nucleic acid sequences and its application for transposon quantifications.

PubMed

Kolacsek, Orsolya; Pergel, Enikő; Varga, Nóra; Apáti, Ágota; Orbán, Tamás I

2017-01-20

There are numerous applications of quantitative PCR for both diagnostic and basic research. As in many other techniques the basis of quantification is that comparisons are made between different (unknown and known or reference) specimens of the same entity. When the aim is to compare real quantities of different species in samples, one cannot escape their separate precise absolute quantification. We have established a simple and reliable method for this purpose (Ct shift method) which combines the absolute and the relative approach. It requires a plasmid standard containing both sequences of amplicons to be compared (e.g. the target of interest and the endogenous control). It can serve as a reference sample with equal copies of templates for both targets. Using the ΔΔCt formula we can quantify the exact ratio of the two templates in each unknown sample. The Ct shift method has been successfully applied for transposon gene copy measurements, as well as for comparison of different mRNAs in cDNA samples. This study provides the proof of concept and introduces some potential applications of the method; the absolute nature of results even without the need for real reference samples can contribute to the universality of the method and comparability of different studies. Copyright © 2016 Elsevier B.V. All rights reserved.

Impact of perinatal environmental tobacco smoke on the development of childhood allergic diseases.

PubMed

Yang, Hyeon-Jong

2016-08-01

Allergic diseases such as asthma, allergic rhinitis, atopic dermatitis, and food allergy, are most common chronic, noncommunicable diseases in childhood. In the past few decades, the prevalence has increased abruptly worldwide. There are 2 possible explanations for the rising prevalence of allergic diseases worldwide, that an increased disease-awareness of physician, patient, or caregivers, and an abrupt exposure to unknown hazards. Unfortunately, the underlying mechanisms remain largely unknown. Despite the continuing efforts worldwide, the etiologies and rising prevalence remain unclear. Thus, it is important to identify and control risk factors in the susceptible individual for the best prevention and management. Genetic susceptibility or environments may be a potential background for the development of allergic disease, however they alone cannot explain the rising prevalence worldwide. There is growing evidence that epigenetic change depends on the gene, environment, and their interactions, may induce a long-lasting altered gene expression and the consequent development of allergic diseases. In epigenetic mechanisms, environmental tobacco smoke (ETS) exposure during critical period (i.e., during pregnancy and early life) are considered as a potential cause of the development of childhood allergic diseases. However, the causal relationship is still unclear. This review aimed to highlight the impact of ETS exposure during the perinatal period on the development of childhood allergic diseases and to propose a future research direction.

Chaos control in delayed phase space constructed by the Takens embedding theory

NASA Astrophysics Data System (ADS)

Hajiloo, R.; Salarieh, H.; Alasty, A.

2018-01-01

In this paper, the problem of chaos control in discrete-time chaotic systems with unknown governing equations and limited measurable states is investigated. Using the time-series of only one measurable state, an algorithm is proposed to stabilize unstable fixed points. The approach consists of three steps: first, using Takens embedding theory, a delayed phase space preserving the topological characteristics of the unknown system is reconstructed. Second, a dynamic model is identified by recursive least squares method to estimate the time-series data in the delayed phase space. Finally, based on the reconstructed model, an appropriate linear delayed feedback controller is obtained for stabilizing unstable fixed points of the system. Controller gains are computed using a systematic approach. The effectiveness of the proposed algorithm is examined by applying it to the generalized hyperchaotic Henon system, prey-predator population map, and the discrete-time Lorenz system.

Output-Feedback Control of Unknown Linear Discrete-Time Systems With Stochastic Measurement and Process Noise via Approximate Dynamic Programming.

PubMed

Wang, Jun-Sheng; Yang, Guang-Hong

2017-07-25

This paper studies the optimal output-feedback control problem for unknown linear discrete-time systems with stochastic measurement and process noise. A dithered Bellman equation with the innovation covariance matrix is constructed via the expectation operator given in the form of a finite summation. On this basis, an output-feedback-based approximate dynamic programming method is developed, where the terms depending on the innovation covariance matrix are available with the aid of the innovation covariance matrix identified beforehand. Therefore, by iterating the Bellman equation, the resulting value function can converge to the optimal one in the presence of the aforementioned noise, and the nearly optimal control laws are delivered. To show the effectiveness and the advantages of the proposed approach, a simulation example and a velocity control experiment on a dc machine are employed.

Training a Network of Electronic Neurons for Control of a Mobile Robot

NASA Astrophysics Data System (ADS)

Vromen, T. G. M.; Steur, E.; Nijmeijer, H.

An adaptive training procedure is developed for a network of electronic neurons, which controls a mobile robot driving around in an unknown environment while avoiding obstacles. The neuronal network controls the angular velocity of the wheels of the robot based on the sensor readings. The nodes in the neuronal network controller are clusters of neurons rather than single neurons. The adaptive training procedure ensures that the input-output behavior of the clusters is identical, even though the constituting neurons are nonidentical and have, in isolation, nonidentical responses to the same input. In particular, we let the neurons interact via a diffusive coupling, and the proposed training procedure modifies the diffusion interaction weights such that the neurons behave synchronously with a predefined response. The working principle of the training procedure is experimentally validated and results of an experiment with a mobile robot that is completely autonomously driving in an unknown environment with obstacles are presented.

Observed-Based Adaptive Fuzzy Tracking Control for Switched Nonlinear Systems With Dead-Zone.

PubMed

Tong, Shaocheng; Sui, Shuai; Li, Yongming

2015-12-01

In this paper, the problem of adaptive fuzzy output-feedback control is investigated for a class of uncertain switched nonlinear systems in strict-feedback form. The considered switched systems contain unknown nonlinearities, dead-zone, and immeasurable states. Fuzzy logic systems are utilized to approximate the unknown nonlinear functions, a switched fuzzy state observer is designed and thus the immeasurable states are obtained by it. By applying the adaptive backstepping design principle and the average dwell time method, an adaptive fuzzy output-feedback tracking control approach is developed. It is proved that the proposed control approach can guarantee that all the variables in the closed-loop system are bounded under a class of switching signals with average dwell time, and also that the system output can track a given reference signal as closely as possible. The simulation results are given to check the effectiveness of the proposed approach.

Cryogenic propellant thermal control system design considerations, analyses, and concepts applied to a Mars human exploration mission

NASA Technical Reports Server (NTRS)

Plachta, David W.; Tucker, Stephen; Hoffman, David J.

1993-01-01

This paper analyzes, defines, and sizes cryogenic storage thermal control systems that meet the requirements of future NASA Mars human exploration missions. The design issues of this system include the projection of the existing Multilayer Insulation data base for cryogenic storage to much thicker (10 cm or more) insulation systems, the unknown heat leak from mechanical interfaces, and the thermal and structural performance effects of the large tank sizes required for a Mars mission. Acknowledging these unknown effects, heat loss projections are made based on extrapolation of the existing data base. The results indicate that hydrogen, methane, and oxygen are feasible propellants, and that the best suited thermal control sytems are 'thick' MLI, thermodynamic vent sytems, cryocoolers, and vacuum jackets.

Kinematics and Dynamics of Motion Control Based on Acceleration Control

NASA Astrophysics Data System (ADS)

Ohishi, Kiyoshi; Ohba, Yuzuru; Katsura, Seiichiro

The first IEEE International Workshop on Advanced Motion Control was held in 1990 pointed out the importance of physical interpretation of motion control. The software servoing technology is now common in machine tools, robotics, and mechatronics. It has been intensively developed for the numerical control (NC) machines. Recently, motion control in unknown environment will be more and more important. Conventional motion control is not always suitable due to the lack of adaptive capability to the environment. A more sophisticated ability in motion control is necessary for compliant contact with environment. Acceleration control is the key technology of motion control in unknown environment. The acceleration control can make a motion system to be a zero control stiffness system without losing the robustness. Furthermore, a realization of multi-degree-of-freedom motion is necessary for future human assistance. A human assistant motion will require various control stiffness corresponding to the task. The review paper focuses on the modal coordinate system to integrate the various control stiffness in the virtual axes. A bilateral teleoperation is a good candidate to consider the future human assistant motion and integration of decentralized systems. Thus the paper reviews and discusses the bilateral teleoperation from the control stiffness and the modal control design points of view.