OVoG Inversion for the Retrieval of Agricultural Crop Structure by Means of Multi-Baseline Polarimetric SAR Interferometry

NASA Astrophysics Data System (ADS)

Pichierri, Manuele; Hajnsek, Irena

2015-04-01

In this work, the potential of multi-baseline Pol-InSAR for crop parameter estimation (e.g. crop height and extinction coefficients) is explored. For this reason, a novel Oriented Volume over Ground (OVoG) inversion scheme is developed, which makes use of multi-baseline observables to estimate the whole stack of model parameters. The proposed algorithm has been initially validated on a set of randomly-generated OVoG scenarios, to assess its stability over crop structure changes and its robustness against volume decorrelation and other decorrelation sources. Then, it has been applied to a collection of multi-baseline repeat-pass SAR data, acquired over a rural area in Germany by DLR's F-SAR.

Preliminary assessment of the robustness of dynamic inversion based flight control laws

NASA Technical Reports Server (NTRS)

Snell, S. A.

1992-01-01

Dynamic-inversion-based flight control laws present an attractive alternative to conventional gain-scheduled designs for high angle-of-attack maneuvering, where nonlinearities dominate the dynamics. Dynamic inversion is easily applied to the aircraft dynamics requiring a knowledge of the nonlinear equations of motion alone, rather than an extensive set of linearizations. However, the robustness properties of the dynamic inversion are questionable especially when considering the uncertainties involved with the aerodynamic database during post-stall flight. This paper presents a simple analysis and some preliminary results of simulations with a perturbed database. It is shown that incorporating integrators into the control loops helps to improve the performance in the presence of these perturbations.

Is tibialis anterior tendon transfer effective for recurrent clubfoot?

PubMed

Gray, Kelly; Burns, Joshua; Little, David; Bellemore, Michael; Gibbons, Paul

2014-02-01

Tibialis anterior tendon transfer surgery forms a part of Ponseti management for children with congenital talipes equinovarus who, after initial correction, present with residual dynamic supination. Although retrospective studies support good outcomes, prospective longitudinal studies in this population are lacking. We assessed strength, plantar loading, ROM, foot alignment, function, satisfaction, and quality of life in patients with clubfoot that recurred after Ponseti casting who met indications for tibialis anterior tendon transfer surgery, and compared them with a group of patients with clubfoot treated with casting but whose deformity did not recur (therefore who were not indicated for tibialis anterior tendon transfer surgery). Twenty children with idiopathic congenital talipes equinovarus indicated for tibialis anterior tendon transfer surgery were recruited. Assessment at baseline (before surgery), and 3, 6, and 12 months (after surgery) included strength (hand-held dynamometry), plantar loading (capacitance transducer matrix platform), ROM (Dimeglio scale), foot alignment (Foot Posture Index(©)), function and satisfaction (disease-specific instrument for clubfoot), and quality of life (Infant Toddler Quality of Life Questionnaire™). Outcomes were compared with those of 12 age-matched children with congenital talipes equinovarus not indicated for tibialis anterior tendon transfer surgery. Followup was 100% in the control group and 95% (19 of 20) in the tibialis anterior transfer group. At baseline, the tibialis anterior tendon transfer group had a significantly worse eversion-to-inversion strength ratio, plantar loading, ROM, foot alignment, and function and satisfaction. At 3 months after surgery, eversion-to-inversion strength, plantar loading, and function and satisfaction were no longer different between groups. Improvements were maintained at 12 months after surgery (eversion-to-inversion strength mean difference, 8% body weight; 95% CI, -26% to 11%; p = 0.412; plantar loading, p > 0.251; function and satisfaction, p = 0.076). ROM remained less and foot alignment more supinated in the tibialis anterior tendon transfer group between baseline and followup (p < 0.001, p < 0.001). Tibialis anterior tendon transfer surgery was an effective procedure, which at 12-month followup restored the balance of eversion-to-inversion strength and resulted in plantar loading and function and satisfaction outcomes similar to those of age-matched children with congenital talipes equinovarus who after Ponseti casting were not indicated for tibialis anterior tendon transfer.

Cryotherapy does not affect peroneal reaction following sudden inversion.

PubMed

Berg, Christine L; Hart, Joseph M; Palmieri-Smith, Riann; Cross, Kevin M; Ingersoll, Christopher D

2007-11-01

If ankle joint cryotherapy impairs the ability of the ankle musculature to counteract potentially injurious forces, the ankle is left vulnerable to injury. To compare peroneal reaction to sudden inversion following ankle joint cryotherapy. Repeated measures design with independent variables, treatment (cryotherapy and control), and time (baseline, immediately post treatment, 15 minutes post treatment, and 30 minutes post treatment). University research laboratory. Twenty-seven healthy volunteers. An ice bag was secured to the lateral ankle joint for 20 minutes. The onset and average root mean square amplitude of EMG activity in the peroneal muscles was calculated following the release of a trap door mechanism causing inversion. There was no statistically significant change from baseline for peroneal reaction time or average peroneal muscle activity at any post treatment time. Cryotherapy does not affect peroneal muscle reaction following sudden inversion perturbation.

A 3D generic inverse dynamic method using wrench notation and quaternion algebra.

PubMed

Dumas, R; Aissaoui, R; de Guise, J A

2004-06-01

In the literature, conventional 3D inverse dynamic models are limited in three aspects related to inverse dynamic notation, body segment parameters and kinematic formalism. First, conventional notation yields separate computations of the forces and moments with successive coordinate system transformations. Secondly, the way conventional body segment parameters are defined is based on the assumption that the inertia tensor is principal and the centre of mass is located between the proximal and distal ends. Thirdly, the conventional kinematic formalism uses Euler or Cardanic angles that are sequence-dependent and suffer from singularities. In order to overcome these limitations, this paper presents a new generic method for inverse dynamics. This generic method is based on wrench notation for inverse dynamics, a general definition of body segment parameters and quaternion algebra for the kinematic formalism.

Laser Powered Launch Vehicle Performance Analyses

NASA Technical Reports Server (NTRS)

Chen, Yen-Sen; Liu, Jiwen; Wang, Ten-See (Technical Monitor)

2001-01-01

The purpose of this study is to establish the technical ground for modeling the physics of laser powered pulse detonation phenomenon. Laser powered propulsion systems involve complex fluid dynamics, thermodynamics and radiative transfer processes. Successful predictions of the performance of laser powered launch vehicle concepts depend on the sophisticate models that reflects the underlying flow physics including the laser ray tracing the focusing, inverse Bremsstrahlung (IB) effects, finite-rate air chemistry, thermal non-equilibrium, plasma radiation and detonation wave propagation, etc. The proposed work will extend the base-line numerical model to an efficient design analysis tool. The proposed model is suitable for 3-D analysis using parallel computing methods.

A time domain inverse dynamic method for the end point tracking control of a flexible manipulator

NASA Technical Reports Server (NTRS)

Kwon, Dong-Soo; Book, Wayne J.

1991-01-01

The inverse dynamic equation of a flexible manipulator was solved in the time domain. By dividing the inverse system equation into the causal part and the anticausal part, we calculated the torque and the trajectories of all state variables for a given end point trajectory. The interpretation of this method in the frequency domain was explained in detail using the two-sided Laplace transform and the convolution integral. The open loop control of the inverse dynamic method shows an excellent result in simulation. For real applications, a practical control strategy is proposed by adding a feedback tracking control loop to the inverse dynamic feedforward control, and its good experimental performance is presented.

Modified Dynamic Inversion to Control Large Flexible Aircraft: What's Going On?

NASA Technical Reports Server (NTRS)

Gregory, Irene M.

1999-01-01

High performance aircraft of the future will be designed lighter, more maneuverable, and operate over an ever expanding flight envelope. One of the largest differences from the flight control perspective between current and future advanced aircraft is elasticity. Over the last decade, dynamic inversion methodology has gained considerable popularity in application to highly maneuverable fighter aircraft, which were treated as rigid vehicles. This paper explores dynamic inversion application to an advanced highly flexible aircraft. An initial application has been made to a large flexible supersonic aircraft. In the course of controller design for this advanced vehicle, modifications were made to the standard dynamic inversion methodology. The results of this application were deemed rather promising. An analytical study has been undertaken to better understand the nature of the made modifications and to determine its general applicability. This paper presents the results of this initial analytical look at the modifications to dynamic inversion to control large flexible aircraft.

Improvement of Forest Height Retrieval By Integration of Dual-Baseline PolInSAR Data And External DEM Data

NASA Astrophysics Data System (ADS)

Xie, Q.; Wang, C.; Zhu, J.; Fu, H.; Wang, C.

2015-06-01

In recent years, a lot of studies have shown that polarimetric synthetic aperture radar interferometry (PolInSAR) is a powerful technique for forest height mapping and monitoring. However, few researches address the problem of terrain slope effect, which will be one of the major limitations for forest height inversion in mountain forest area. In this paper, we present a novel forest height retrieval algorithm by integration of dual-baseline PolInSAR data and external DEM data. For the first time, we successfully expand the S-RVoG (Sloped-Random Volume over Ground) model for forest parameters inversion into the case of dual-baseline PolInSAR configuration. In this case, the proposed method not only corrects terrain slope variation effect efficiently, but also involves more observations to improve the accuracy of parameters inversion. In order to demonstrate the performance of the inversion algorithm, a set of quad-pol images acquired at the P-band in interferometric repeat-pass mode by the German Aerospace Center (DLR) with the Experimental SAR (E-SAR) system, in the frame of the BioSAR2008 campaign, has been used for the retrieval of forest height over Krycklan boreal forest in northern Sweden. At the same time, a high accuracy external DEM in the experimental area has been collected for computing terrain slope information, which subsequently is used as an inputting parameter in the S-RVoG model. Finally, in-situ ground truth heights in stand-level have been collected to validate the inversion result. The preliminary results show that the proposed inversion algorithm promises to provide much more accurate estimation of forest height than traditional dualbaseline inversion algorithms.

Time-lapse joint AVO inversion using generalized linear method based on exact Zoeppritz equations

NASA Astrophysics Data System (ADS)

Zhi, Longxiao; Gu, Hanming

2018-03-01

The conventional method of time-lapse AVO (Amplitude Versus Offset) inversion is mainly based on the approximate expression of Zoeppritz equations. Though the approximate expression is concise and convenient to use, it has certain limitations. For example, its application condition is that the difference of elastic parameters between the upper medium and lower medium is little and the incident angle is small. In addition, the inversion of density is not stable. Therefore, we develop the method of time-lapse joint AVO inversion based on exact Zoeppritz equations. In this method, we apply exact Zoeppritz equations to calculate the reflection coefficient of PP wave. And in the construction of objective function for inversion, we use Taylor series expansion to linearize the inversion problem. Through the joint AVO inversion of seismic data in baseline survey and monitor survey, we can obtain the P-wave velocity, S-wave velocity, density in baseline survey and their time-lapse changes simultaneously. We can also estimate the oil saturation change according to inversion results. Compared with the time-lapse difference inversion, the joint inversion doesn't need certain assumptions and can estimate more parameters simultaneously. It has a better applicability. Meanwhile, by using the generalized linear method, the inversion is easily implemented and its calculation cost is small. We use the theoretical model to generate synthetic seismic records to test and analyze the influence of random noise. The results can prove the availability and anti-noise-interference ability of our method. We also apply the inversion to actual field data and prove the feasibility of our method in actual situation.

Next Generation Robots for STEM Education andResearch at Huston Tillotson University

DTIC Science & Technology

2017-11-10

dynamics through the following command: roslaunch mtb_lab6_feedback_linearization gravity_compensation.launch Part B: Gravity Inversion : After...understood the system’s natural dynamics. roslaunch mtb_lab6_feedback_linearization gravity_compensation.launch Part B: Gravity Inversion ...is created using the following command: roslaunch mtb_lab6_feedback_linearization gravity_inversion.launch Gravity inversion is just one

Using a pseudo-dynamic source inversion approach to improve earthquake source imaging

NASA Astrophysics Data System (ADS)

Zhang, Y.; Song, S. G.; Dalguer, L. A.; Clinton, J. F.

2014-12-01

Imaging a high-resolution spatio-temporal slip distribution of an earthquake rupture is a core research goal in seismology. In general we expect to obtain a higher quality source image by improving the observational input data (e.g. using more higher quality near-source stations). However, recent studies show that increasing the surface station density alone does not significantly improve source inversion results (Custodio et al. 2005; Zhang et al. 2014). We introduce correlation structures between the kinematic source parameters: slip, rupture velocity, and peak slip velocity (Song et al. 2009; Song and Dalguer 2013) in the non-linear source inversion. The correlation structures are physical constraints derived from rupture dynamics that effectively regularize the model space and may improve source imaging. We name this approach pseudo-dynamic source inversion. We investigate the effectiveness of this pseudo-dynamic source inversion method by inverting low frequency velocity waveforms from a synthetic dynamic rupture model of a buried vertical strike-slip event (Mw 6.5) in a homogeneous half space. In the inversion, we use a genetic algorithm in a Bayesian framework (Moneli et al. 2008), and a dynamically consistent regularized Yoffe function (Tinti, et al. 2005) was used for a single-window slip velocity function. We search for local rupture velocity directly in the inversion, and calculate the rupture time using a ray-tracing technique. We implement both auto- and cross-correlation of slip, rupture velocity, and peak slip velocity in the prior distribution. Our results suggest that kinematic source model estimates capture the major features of the target dynamic model. The estimated rupture velocity closely matches the target distribution from the dynamic rupture model, and the derived rupture time is smoother than the one we searched directly. By implementing both auto- and cross-correlation of kinematic source parameters, in comparison to traditional smoothing constraints, we are in effect regularizing the model space in a more physics-based manner without loosing resolution of the source image. Further investigation is needed to tune the related parameters of pseudo-dynamic source inversion and relative weighting between the prior and the likelihood function in the Bayesian inversion.

Approximated Stable Inversion for Nonlinear Systems with Nonhyperbolic Internal Dynamics. Revised

NASA Technical Reports Server (NTRS)

Devasia, Santosh

1999-01-01

A technique to achieve output tracking for nonminimum phase nonlinear systems with non- hyperbolic internal dynamics is presented. The present paper integrates stable inversion techniques (that achieve exact-tracking) with approximation techniques (that modify the internal dynamics) to circumvent the nonhyperbolicity of the internal dynamics - this nonhyperbolicity is an obstruction to applying presently available stable inversion techniques. The theory is developed for nonlinear systems and the method is applied to a two-cart with inverted-pendulum example.

An inverse dynamics approach to trajectory optimization and guidance for an aerospace plane

NASA Technical Reports Server (NTRS)

Lu, Ping

1992-01-01

The optimal ascent problem for an aerospace planes is formulated as an optimal inverse dynamic problem. Both minimum-fuel and minimax type of performance indices are considered. Some important features of the optimal trajectory and controls are used to construct a nonlinear feedback midcourse controller, which not only greatly simplifies the difficult constrained optimization problem and yields improved solutions, but is also suited for onboard implementation. Robust ascent guidance is obtained by using combination of feedback compensation and onboard generation of control through the inverse dynamics approach. Accurate orbital insertion can be achieved with near-optimal control of the rocket through inverse dynamics even in the presence of disturbances.

Handling Qualities of Model Reference Adaptive Controllers with Varying Complexity for Pitch-Roll Coupled Failures

NASA Technical Reports Server (NTRS)

Schaefer, Jacob; Hanson, Curt; Johnson, Marcus A.; Nguyen, Nhan

2011-01-01

Three model reference adaptive controllers (MRAC) with varying levels of complexity were evaluated on a high performance jet aircraft and compared along with a baseline nonlinear dynamic inversion controller. The handling qualities and performance of the controllers were examined during failure conditions that induce coupling between the pitch and roll axes. Results from flight tests showed with a roll to pitch input coupling failure, the handling qualities went from Level 2 with the baseline controller to Level 1 with the most complex MRAC tested. A failure scenario with the left stabilator frozen also showed improvement with the MRAC. Improvement in performance and handling qualities was generally seen as complexity was incrementally added; however, added complexity usually corresponds to increased verification and validation effort required for certification. The tradeoff between complexity and performance is thus important to a controls system designer when implementing an adaptive controller on an aircraft. This paper investigates this relation through flight testing of several controllers of vary complexity.

Time-lapse joint AVO inversion using generalized linear method based on exact Zoeppritz equations

NASA Astrophysics Data System (ADS)

Zhi, L.; Gu, H.

2017-12-01

The conventional method of time-lapse AVO (Amplitude Versus Offset) inversion is mainly based on the approximate expression of Zoeppritz equations. Though the approximate expression is concise and convenient to use, it has certain limitations. For example, its application condition is that the difference of elastic parameters between the upper medium and lower medium is little and the incident angle is small. In addition, the inversion of density is not stable. Therefore, we develop the method of time-lapse joint AVO inversion based on exact Zoeppritz equations. In this method, we apply exact Zoeppritz equations to calculate the reflection coefficient of PP wave. And in the construction of objective function for inversion, we use Taylor expansion to linearize the inversion problem. Through the joint AVO inversion of seismic data in baseline survey and monitor survey, we can obtain P-wave velocity, S-wave velocity, density in baseline survey and their time-lapse changes simultaneously. We can also estimate the oil saturation change according to inversion results. Compared with the time-lapse difference inversion, the joint inversion has a better applicability. It doesn't need some assumptions and can estimate more parameters simultaneously. Meanwhile, by using the generalized linear method, the inversion is easily realized and its calculation amount is small. We use the Marmousi model to generate synthetic seismic records to test and analyze the influence of random noise. Without noise, all estimation results are relatively accurate. With the increase of noise, P-wave velocity change and oil saturation change are stable and less affected by noise. S-wave velocity change is most affected by noise. Finally we use the actual field data of time-lapse seismic prospecting to process and the results can prove the availability and feasibility of our method in actual situation.

Model Following and High Order Augmentation for Rotorcraft Control, Applied via Partial Authority

NASA Astrophysics Data System (ADS)

Spires, James Michael

This dissertation consists of two main studies, a few small studies, and design documentation, all aimed at improving rotorcraft control by employing multi-input multi-output (MIMO) command-modelfollowing control as a baseline, together with a selectable (and de-selectable) MIMO high order compensator that augments the baseline. Two methods of MIMO command-model-following control design are compared for rotorcraft flight control. The first, Explicit Model Following (EMF), employs SISO inverse plants with a dynamic decoupling matrix, which is a purely feed-forward approach to inverting the plant. The second is Dynamic Inversion (DI), which involves both feed-forward and feedback path elements to invert the plant. The EMF design is purely linear, while the DI design has some nonlinear elements in vertical rate control. For each of these methods, an architecture is presented that provides angular rate model-following with selectable vertical rate model-following. Implementation challenges of both EMF and DI are covered, and methods of dealing with them are presented. These two MIMO model-following approaches are evaluated regarding (1) fidelity to the command model, and (2) turbulence rejection. Both are found to provide good tracking of commands and reduction of cross coupling. Next, an architecture and design methodology for high order compensator (HOC) augmentation of a baseline controller for rotorcraft is presented. With this architecture, the HOC compensator is selectable and can easily be authority-limited, which might ease certification. Also, the plant for this augmentative MIMO compensator design is a stabilized helicopter system, so good flight test data could be safely gathered for more accurate plant identification. The design methodology is carried out twice on an example helicopter model, once with turbulence rejection as the objective, and once with the additional objective of closely following pilot commands. The turbulence rejection HOC is feedback only (HOC_FB), while the combined objective HOC has both feedback and feedforward elements (HOC_FBFF). The HOC_FB was found to be better at improving turbulence rejection but generally degrades the following of pilot commands. The HOC_FBFF improves turbulence rejection relative to the Baseline controller, but not by as much as HOC_FB. However, HOC_FBFF also generally improves the following of pilot commands. Future work is suggested and facilitated in the areas of DI, MIMO EMF, and HOC augmentation. High frequency dynamics, neglected in the DI design, unexpectedly change the low frequency behavior of the DI-plant system, in addition to the expected change in high frequency dynamics. This dissertation shows why, and suggests a technique for designing a pseudo-command pre-filter that at least partially restores the intended DI-plant dynamics. For EMF, a procedure is presented that avoids use of a reducedorder model, and instead uses a full-order model or even frequency-domain flight test data. With HOC augmentation, future research might investigate the utility of adding an H? constraint to the design objective, which is known as an equal-weighting mixed-norm H2/H infinity design. Because all the formulas in the published literature either require solution of three coupled Riccati Equations (for which there is no readily available tool), or make assumptions that do not fit the present problem, appropriate equalweighting H2/H infinity design formulas are derived which involve two de-coupled Riccati Equations.

Enhancing Autonomy of Aerial Systems Via Integration of Visual Sensors into Their Avionics Suite

DTIC Science & Technology

2016-09-01

aerial platform for subsequent visual sensor integration. 14. SUBJECT TERMS autonomous system, quadrotors, direct method, inverse ...CONTROLLER ARCHITECTURE .....................................................43 B. INVERSE DYNAMICS IN THE VIRTUAL DOMAIN ......................45 1...control station GPS Global-Positioning System IDVD inverse dynamics in the virtual domain ILP integer linear program INS inertial-navigation system

Adaptive online inverse control of a shape memory alloy wire actuator using a dynamic neural network

NASA Astrophysics Data System (ADS)

Mai, Huanhuan; Song, Gangbing; Liao, Xiaofeng

2013-01-01

Shape memory alloy (SMA) actuators exhibit severe hysteresis, a nonlinear behavior, which complicates control strategies and limits their applications. This paper presents a new approach to controlling an SMA actuator through an adaptive inverse model based controller that consists of a dynamic neural network (DNN) identifier, a copy dynamic neural network (CDNN) feedforward term and a proportional (P) feedback action. Unlike fixed hysteresis models used in most inverse controllers, the proposed one uses a DNN to identify online the relationship between the applied voltage to the actuator and the displacement (the inverse model). Even without a priori knowledge of the SMA hysteresis and without pre-training, the proposed controller can precisely control the SMA wire actuator in various tracking tasks by identifying online the inverse model of the SMA actuator. Experiments were conducted, and experimental results demonstrated real-time modeling capabilities of DNN and the performance of the adaptive inverse controller.

A comprehensive inversion approach for feedforward compensation of piezoactuator system at high frequency

NASA Astrophysics Data System (ADS)

Tian, Lizhi; Xiong, Zhenhua; Wu, Jianhua; Ding, Han

2016-09-01

Motion control of the piezoactuator system over broadband frequencies is limited due to its inherent hysteresis and system dynamics. One of the suggested ways is to use feedforward controller to linearize the input-output relationship of the piezoactuator system. Although there have been many feedforward approaches, it is still a challenge to develop feedforward controller for the piezoactuator system at high frequency. Hence, this paper presents a comprehensive inversion approach in consideration of the coupling of hysteresis and dynamics. In this work, the influence of dynamics compensation on the input-output relationship of the piezoactuator system is investigated first. With system dynamics compensation, the input-output relationship of the piezoactuator system will be further represented as rate-dependent nonlinearity due to the inevitable dynamics compensation error, especially at high frequency. Base on this result, the feedforward controller composed by a cascade of linear dynamics inversion and rate-dependent nonlinearity inversion is developed. Then, the system identification of the comprehensive inversion approach is proposed. Finally, experimental results show that the proposed approach can improve the performance on tracking of both periodic and non-periodic trajectories at medium and high frequency compared with the conventional feedforward approaches.

Uncertainty quantification of CO₂ saturation estimated from electrical resistance tomography data at the Cranfield site

DOE PAGES

Yang, Xianjin; Chen, Xiao; Carrigan, Charles R.; ...

2014-06-03

A parametric bootstrap approach is presented for uncertainty quantification (UQ) of CO₂ saturation derived from electrical resistance tomography (ERT) data collected at the Cranfield, Mississippi (USA) carbon sequestration site. There are many sources of uncertainty in ERT-derived CO₂ saturation, but we focus on how the ERT observation errors propagate to the estimated CO₂ saturation in a nonlinear inversion process. Our UQ approach consists of three steps. We first estimated the observational errors from a large number of reciprocal ERT measurements. The second step was to invert the pre-injection baseline data and the resulting resistivity tomograph was used as the priormore » information for nonlinear inversion of time-lapse data. We assigned a 3% random noise to the baseline model. Finally, we used a parametric bootstrap method to obtain bootstrap CO₂ saturation samples by deterministically solving a nonlinear inverse problem many times with resampled data and resampled baseline models. Then the mean and standard deviation of CO₂ saturation were calculated from the bootstrap samples. We found that the maximum standard deviation of CO₂ saturation was around 6% with a corresponding maximum saturation of 30% for a data set collected 100 days after injection began. There was no apparent spatial correlation between the mean and standard deviation of CO₂ saturation but the standard deviation values increased with time as the saturation increased. The uncertainty in CO₂ saturation also depends on the ERT reciprocal error threshold used to identify and remove noisy data and inversion constraints such as temporal roughness. Five hundred realizations requiring 3.5 h on a single 12-core node were needed for the nonlinear Monte Carlo inversion to arrive at stationary variances while the Markov Chain Monte Carlo (MCMC) stochastic inverse approach may expend days for a global search. This indicates that UQ of 2D or 3D ERT inverse problems can be performed on a laptop or desktop PC.« less

Joint Loads and Cartilage Stress in Intact Joints of Military Transtibial Amputees: Enhancing Quality of Life

DTIC Science & Technology

2017-04-01

crosstalk); analysis of tested subjects underway. 4) Developed analytical methods to obtain knee joint loads using EMG-driven inverse dynamics; analysis of...13/2018. Completion %: 40. Task 1.3: EMG-driven inverse dynamic (ID) analyses with OpenSim for amputee and control group subjects. Target date: 1...predicted by EMG-driven inverse dynamics. Two-three conference papers are being prepared for submission in February 2017. Other achievements. None

Optic nerve dysfunction during gravity inversion. Visual field abnormalities.

PubMed

Sanborn, G E; Friberg, T R; Allen, R

1987-06-01

Inversion in a head-down position (gravity inversion) results in an intraocular pressure of 35 to 40 mm Hg in normal subjects. We used computerized static perimetry to measure the visual fields of normal subjects during gravity inversion. There were no visual field changes in the central 6 degrees of the visual field compared with the baseline (preinversion) values. However, when the central 30 degrees of the visual field was tested, reversible visual field defects were found in 11 of 19 eyes. We believe that the substantial elevation of intraocular pressure during gravity inversion may pose potential risks to the eyes, and we recommend that inversion for extended periods of time be avoided.

Robust state preparation in quantum simulations of Dirac dynamics

NASA Astrophysics Data System (ADS)

Song, Xue-Ke; Deng, Fu-Guo; Lamata, Lucas; Muga, J. G.

2017-02-01

A nonrelativistic system such as an ultracold trapped ion may perform a quantum simulation of a Dirac equation dynamics under specific conditions. The resulting Hamiltonian and dynamics are highly controllable, but the coupling between momentum and internal levels poses some difficulties to manipulate the internal states accurately in wave packets. We use invariants of motion to inverse engineer robust population inversion processes with a homogeneous, time-dependent simulated electric field. This exemplifies the usefulness of inverse-engineering techniques to improve the performance of quantum simulation protocols.

Dynamic inverse models in human-cyber-physical systems

NASA Astrophysics Data System (ADS)

Robinson, Ryan M.; Scobee, Dexter R. R.; Burden, Samuel A.; Sastry, S. Shankar

2016-05-01

Human interaction with the physical world is increasingly mediated by automation. This interaction is characterized by dynamic coupling between robotic (i.e. cyber) and neuromechanical (i.e. human) decision-making agents. Guaranteeing performance of such human-cyber-physical systems will require predictive mathematical models of this dynamic coupling. Toward this end, we propose a rapprochement between robotics and neuromechanics premised on the existence of internal forward and inverse models in the human agent. We hypothesize that, in tele-robotic applications of interest, a human operator learns to invert automation dynamics, directly translating from desired task to required control input. By formulating the model inversion problem in the context of a tracking task for a nonlinear control system in control-a_ne form, we derive criteria for exponential tracking and show that the resulting dynamic inverse model generally renders a portion of the physical system state (i.e., the internal dynamics) unobservable from the human operator's perspective. Under stability conditions, we show that the human can achieve exponential tracking without formulating an estimate of the system's state so long as they possess an accurate model of the system's dynamics. These theoretical results are illustrated using a planar quadrotor example. We then demonstrate that the automation can intervene to improve performance of the tracking task by solving an optimal control problem. Performance is guaranteed to improve under the assumption that the human learns and inverts the dynamic model of the altered system. We conclude with a discussion of practical limitations that may hinder exact dynamic model inversion.

Network Inference via the Time-Varying Graphical Lasso

PubMed Central

Hallac, David; Park, Youngsuk; Boyd, Stephen; Leskovec, Jure

2018-01-01

Many important problems can be modeled as a system of interconnected entities, where each entity is recording time-dependent observations or measurements. In order to spot trends, detect anomalies, and interpret the temporal dynamics of such data, it is essential to understand the relationships between the different entities and how these relationships evolve over time. In this paper, we introduce the time-varying graphical lasso (TVGL), a method of inferring time-varying networks from raw time series data. We cast the problem in terms of estimating a sparse time-varying inverse covariance matrix, which reveals a dynamic network of interdependencies between the entities. Since dynamic network inference is a computationally expensive task, we derive a scalable message-passing algorithm based on the Alternating Direction Method of Multipliers (ADMM) to solve this problem in an efficient way. We also discuss several extensions, including a streaming algorithm to update the model and incorporate new observations in real time. Finally, we evaluate our TVGL algorithm on both real and synthetic datasets, obtaining interpretable results and outperforming state-of-the-art baselines in terms of both accuracy and scalability. PMID:29770256

Computational structures for robotic computations

NASA Technical Reports Server (NTRS)

Lee, C. S. G.; Chang, P. R.

1987-01-01

The computational problem of inverse kinematics and inverse dynamics of robot manipulators by taking advantage of parallelism and pipelining architectures is discussed. For the computation of inverse kinematic position solution, a maximum pipelined CORDIC architecture has been designed based on a functional decomposition of the closed-form joint equations. For the inverse dynamics computation, an efficient p-fold parallel algorithm to overcome the recurrence problem of the Newton-Euler equations of motion to achieve the time lower bound of O(log sub 2 n) has also been developed.

Assessing when chromosomal rearrangements affect the dynamics of speciation: implications from computer simulations

PubMed Central

Feder, Jeffrey L.; Nosil, Patrik; Flaxman, Samuel M.

2014-01-01

Many hypotheses have been put forth to explain the origin and spread of inversions, and their significance for speciation. Several recent genic models have proposed that inversions promote speciation with gene flow due to the adaptive significance of the genes contained within them and because of the effects inversions have on suppressing recombination. However, the consequences of inversions for the dynamics of genome wide divergence across the speciation continuum remain unclear, an issue we examine here. We review a framework for the genomics of speciation involving the congealing of the genome into alternate adaptive states representing species (“genome wide congealing”). We then place inversions in this context as examples of how genetic hitchhiking can potentially hasten genome wide congealing. Specifically, we use simulation models to (i) examine the conditions under which inversions may speed genome congealing and (ii) quantify predicted magnitudes of these effects. Effects of inversions on promoting speciation were most common and pronounced when inversions were initially fixed between populations before secondary contact and adaptation involved many genes with small fitness effects. Further work is required on the role of underdominance and epistasis between a few loci of major effect within inversions. The results highlight five important aspects of the roles of inversions in speciation: (i) the geographic context of the origins and spread of inversions, (ii) the conditions under which inversions can facilitate divergence, (iii) the magnitude of that facilitation, (iv) the extent to which the buildup of divergence is likely to be biased within vs. outside of inversions, and (v) the dynamics of the appearance and disappearance of exceptional divergence within inversions. We conclude by discussing the empirical challenges in showing that inversions play a central role in facilitating speciation with gene flow. PMID:25206365

Output Tracking for Systems with Non-Hyperbolic and Near Non-Hyperbolic Internal Dynamics: Helicopter Hover Control

NASA Technical Reports Server (NTRS)

Devasia, Santosh

1996-01-01

A technique to achieve output tracking for nonminimum phase linear systems with non-hyperbolic and near non-hyperbolic internal dynamics is presented. This approach integrates stable inversion techniques, that achieve exact-tracking, with approximation techniques, that modify the internal dynamics to achieve desirable performance. Such modification of the internal dynamics is used (1) to remove non-hyperbolicity which an obstruction to applying stable inversion techniques and (2) to reduce large pre-actuation time needed to apply stable inversion for near non-hyperbolic cases. The method is applied to an example helicopter hover control problem with near non-hyperbolic internal dynamic for illustrating the trade-off between exact tracking and reduction of pre-actuation time.

Transient Inverse Calibration of Site-Wide Groundwater Model to Hanford Operational Impacts from 1943 to 1996--Alternative Conceptual Model Considering Interaction with Uppermost Basalt Confined Aquifer

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

Vermeul, Vincent R.; Cole, Charles R.; Bergeron, Marcel P.

2001-08-29

The baseline three-dimensional transient inverse model for the estimation of site-wide scale flow parameters, including their uncertainties, using data on the transient behavior of the unconfined aquifer system over the entire historical period of Hanford operations, has been modified to account for the effects of basalt intercommunication between the Hanford unconfined aquifer and the underlying upper basalt confined aquifer. Both the baseline and alternative conceptual models (ACM-1) considered only the groundwater flow component and corresponding observational data in the 3-Dl transient inverse calibration efforts. Subsequent efforts will examine both groundwater flow and transport. Comparisons of goodness of fit measures andmore » parameter estimation results for the ACM-1 transient inverse calibrated model with those from previous site-wide groundwater modeling efforts illustrate that the new 3-D transient inverse model approach will strengthen the technical defensibility of the final model(s) and provide the ability to incorporate uncertainty in predictions related to both conceptual model and parameter uncertainty. These results, however, indicate that additional improvements are required to the conceptual model framework. An investigation was initiated at the end of this basalt inverse modeling effort to determine whether facies-based zonation would improve specific yield parameter estimation results (ACM-2). A description of the justification and methodology to develop this zonation is discussed.« less

Longitudinal study of serum carotenoid, retinol, and tocopherol concentrations in relation to breast cancer risk among postmenopausal women12

PubMed Central

Kim, Mimi; Adams-Campbell, Lucile L; Caan, Bette J; Chlebowski, Rowan T; Neuhouser, Marian L; Shikany, James M; Rohan, Thomas E

2009-01-01

Background: Prospective studies have examined the association of serum and plasma carotenoids and micronutrients and breast cancer; however, to date, studies have only assessed exposure at one point in time. Objective: This study analyzed baseline and repeated serum measurements of carotenoids, retinol, and tocopherols to assess their associations with postmenopausal breast cancer risk. Design: Serum concentrations of α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein + zeaxanthin, retinol, α-tocopherol, and γ-tocopherol were measured in a 6% sample of women in the Women's Health Initiative clinical trials at baseline and at years 1, 3, and 6 and in a 1% sample of women in the observational study at baseline and at year 3. The association of baseline compounds and breast cancer risk was estimated by Cox proportional hazards models. In addition, repeated measurements were analyzed as time-dependent covariates. Of 5450 women with baseline measurements, 190 incident cases of breast cancer were ascertained over a median of 8.0 y of follow-up. Results: After multivariable adjustment, risk of invasive breast cancer was inversely associated with baseline serum α-carotene concentrations (hazard ratio for highest compared with the lowest tertile: 0.55; 95% CI: 0.34, 0.90; P = 0.02) and positively associated with baseline lycopene (hazard ratio: 1.47; 95% CI: 0.98, 2.22; P = 0.06). Analysis of repeated measurements indicated that α-carotene and β-carotene were inversely associated with breast cancer and that γ-tocopherol was associated with increased risk. Conclusions: The present study, which was the first to assess repeated measurements of serum carotenoids and micronutrients in relation to breast cancer, adds to the evidence of an inverse association of specific carotenoids with breast cancer. The positive associations observed for lycopene and γ-tocopherol require confirmation. This trial was registered at clinicaltrials.gov as NCT00000611. PMID:19474140

Prospective inverse associations of sex hormone concentrations in men with biomarkers of inflammation and oxidative stress.

PubMed

Haring, Robin; Baumeister, Sebastian E; Völzke, Henry; Dörr, Marcus; Kocher, Thomas; Nauck, Matthias; Wallaschofski, Henri

2012-01-01

The suggested associations between sex hormone concentrations and inflammatory biomarkers in men originate from cross-sectional studies and small-scale clinical trials. But prior studies have not investigated longitudinal associations. Overall, 1344 men aged 20-79 years from the population-based cohort Study of Health in Pomerania were followed up for 5.0 (median) years. We used multivariable regression models to analyze cross-sectional and longitudinal associations of serum sex hormone concentrations (total testosterone [TT], sex hormone-binding globulin [SHBG], calculated free testosterone [free T], and dehydroepiandrosterone sulfate [DHEAS]) with biomarkers of inflammation (fibrinogen, high-sensitive C-reactive protein [hsCRP], and white blood cell count [WBC]) and oxidative stress (γ-glutamyl transferase [GGT]) using ordinary least square regression and generalized estimating equation models, respectively. Cross-sectional models revealed borderline associations of sex hormone concentrations with hsCRP, WBC, and GGT levels that were not retained after multivariable adjustment. Longitudinal multivariable analyses revealed an inverse association of baseline TT, free T, and DHEAS concentrations with change in fibrinogen levels (per SD decrement in TT, 0.25 [95% confidence interval, 0.04-0.45]; in free T, 0.30 [0.09-0.51]; and in DHEAS, 0.23 [0.11-0.36]). Furthermore, baseline DHEAS concentrations were inversely associated with change in WBC levels (per SD decrement, 0.53 [0.24-0.82]). Baseline TT, SHBG, free T, and DHEAS concentrations were also inversely associated with change in GGT after multivariable adjustment. The present study is the first to demonstrate prospective inverse associations between sex hormone concentrations and markers of inflammation and oxidative stress in men. Additional studies are warranted to elucidate potential mechanisms underlying the revealed associations.

Plasma cytokine IL-6 levels and subjective cognitive decline: preliminary findings.

PubMed

Keegan, Andrew P; Paris, Daniel; Luis, Cheryl A; Abdullah, Laila; Ait-Ghezala, Ghania; Beaulieu-Abdelahad, David; Pryor, Makenzie; Chaykin, Jillian; Crynen, Gogce; Crawford, Fiona; Mullan, Michael

2018-02-01

Detection of Alzheimer's disease (AD) prior to clinical inception will be paramount for introducing disease modifying treatments. We have begun collecting baseline characteristics of a community cohort for longitudinal assessment and testing of antecedent blood-based biomarkers. We describe the baseline visit from the first 131 subjects in relationship to a commonly described cytokine, interleukin 6 (IL-6). Subjects from the community presented for a free memory screening with varying degrees of memory concern. We quantified the baseline plasma levels of the cytokine IL-6 and assessed cognition (Montreal Cognitive Assessment, MoCA) and mood (Geriatric Depression Scale, GDS) in relationship to their memory concern. Baseline MoCA scores were inversely related to age, and this association was influenced by an AD risk factor, Apolipoprotein E (APOE4) carrier status. The degree of subjective cognitive decline correlated with GDS and was inversely related to MoCA scores. Interleukin 6 levels were related to age, body mass index, and years of education. It will be important to assess how these baseline IL-6 levels and forthcoming novel biomarkers relate to future cognitive decline. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Inverse Transformation: Unleashing Spatially Heterogeneous Dynamics with an Alternative Approach to XPCS Data Analysis.

PubMed

Andrews, Ross N; Narayanan, Suresh; Zhang, Fan; Kuzmenko, Ivan; Ilavsky, Jan

2018-02-01

X-ray photon correlation spectroscopy (XPCS), an extension of dynamic light scattering (DLS) in the X-ray regime, detects temporal intensity fluctuations of coherent speckles and provides scattering vector-dependent sample dynamics at length scales smaller than DLS. The penetrating power of X-rays enables probing dynamics in a broad array of materials with XPCS, including polymers, glasses and metal alloys, where attempts to describe the dynamics with a simple exponential fit usually fails. In these cases, the prevailing XPCS data analysis approach employs stretched or compressed exponential decay functions (Kohlrausch functions), which implicitly assume homogeneous dynamics. In this paper, we propose an alternative analysis scheme based upon inverse Laplace or Gaussian transformation for elucidating heterogeneous distributions of dynamic time scales in XPCS, an approach analogous to the CONTIN algorithm widely accepted in the analysis of DLS from polydisperse and multimodal systems. Using XPCS data measured from colloidal gels, we demonstrate the inverse transform approach reveals hidden multimodal dynamics in materials, unleashing the full potential of XPCS.

Inverse Transformation: Unleashing Spatially Heterogeneous Dynamics with an Alternative Approach to XPCS Data Analysis

PubMed Central

Andrews, Ross N.; Narayanan, Suresh; Zhang, Fan; Kuzmenko, Ivan; Ilavsky, Jan

2018-01-01

X-ray photon correlation spectroscopy (XPCS), an extension of dynamic light scattering (DLS) in the X-ray regime, detects temporal intensity fluctuations of coherent speckles and provides scattering vector-dependent sample dynamics at length scales smaller than DLS. The penetrating power of X-rays enables probing dynamics in a broad array of materials with XPCS, including polymers, glasses and metal alloys, where attempts to describe the dynamics with a simple exponential fit usually fails. In these cases, the prevailing XPCS data analysis approach employs stretched or compressed exponential decay functions (Kohlrausch functions), which implicitly assume homogeneous dynamics. In this paper, we propose an alternative analysis scheme based upon inverse Laplace or Gaussian transformation for elucidating heterogeneous distributions of dynamic time scales in XPCS, an approach analogous to the CONTIN algorithm widely accepted in the analysis of DLS from polydisperse and multimodal systems. Using XPCS data measured from colloidal gels, we demonstrate the inverse transform approach reveals hidden multimodal dynamics in materials, unleashing the full potential of XPCS. PMID:29875506

Inferring Muscle-Tendon Unit Power from Ankle Joint Power during the Push-Off Phase of Human Walking: Insights from a Multiarticular EMG-Driven Model

PubMed Central

2016-01-01

Introduction Inverse dynamics joint kinetics are often used to infer contributions from underlying groups of muscle-tendon units (MTUs). However, such interpretations are confounded by multiarticular (multi-joint) musculature, which can cause inverse dynamics to over- or under-estimate net MTU power. Misestimation of MTU power could lead to incorrect scientific conclusions, or to empirical estimates that misguide musculoskeletal simulations, assistive device designs, or clinical interventions. The objective of this study was to investigate the degree to which ankle joint power overestimates net plantarflexor MTU power during the Push-off phase of walking, due to the behavior of the flexor digitorum and hallucis longus (FDHL)–multiarticular MTUs crossing the ankle and metatarsophalangeal (toe) joints. Methods We performed a gait analysis study on six healthy participants, recording ground reaction forces, kinematics, and electromyography (EMG). Empirical data were input into an EMG-driven musculoskeletal model to estimate ankle power. This model enabled us to parse contributions from mono- and multi-articular MTUs, and required only one scaling and one time delay factor for each subject and speed, which were solved for based on empirical data. Net plantarflexing MTU power was computed by the model and quantitatively compared to inverse dynamics ankle power. Results The EMG-driven model was able to reproduce inverse dynamics ankle power across a range of gait speeds (R2 ≥ 0.97), while also providing MTU-specific power estimates. We found that FDHL dynamics caused ankle power to slightly overestimate net plantarflexor MTU power, but only by ~2–7%. Conclusions During Push-off, FDHL MTU dynamics do not substantially confound the inference of net plantarflexor MTU power from inverse dynamics ankle power. However, other methodological limitations may cause inverse dynamics to overestimate net MTU power; for instance, due to rigid-body foot assumptions. Moving forward, the EMG-driven modeling approach presented could be applied to understand other tasks or larger multiarticular MTUs. PMID:27764110

Inferring Muscle-Tendon Unit Power from Ankle Joint Power during the Push-Off Phase of Human Walking: Insights from a Multiarticular EMG-Driven Model.

PubMed

Honert, Eric C; Zelik, Karl E

2016-01-01

Inverse dynamics joint kinetics are often used to infer contributions from underlying groups of muscle-tendon units (MTUs). However, such interpretations are confounded by multiarticular (multi-joint) musculature, which can cause inverse dynamics to over- or under-estimate net MTU power. Misestimation of MTU power could lead to incorrect scientific conclusions, or to empirical estimates that misguide musculoskeletal simulations, assistive device designs, or clinical interventions. The objective of this study was to investigate the degree to which ankle joint power overestimates net plantarflexor MTU power during the Push-off phase of walking, due to the behavior of the flexor digitorum and hallucis longus (FDHL)-multiarticular MTUs crossing the ankle and metatarsophalangeal (toe) joints. We performed a gait analysis study on six healthy participants, recording ground reaction forces, kinematics, and electromyography (EMG). Empirical data were input into an EMG-driven musculoskeletal model to estimate ankle power. This model enabled us to parse contributions from mono- and multi-articular MTUs, and required only one scaling and one time delay factor for each subject and speed, which were solved for based on empirical data. Net plantarflexing MTU power was computed by the model and quantitatively compared to inverse dynamics ankle power. The EMG-driven model was able to reproduce inverse dynamics ankle power across a range of gait speeds (R2 ≥ 0.97), while also providing MTU-specific power estimates. We found that FDHL dynamics caused ankle power to slightly overestimate net plantarflexor MTU power, but only by ~2-7%. During Push-off, FDHL MTU dynamics do not substantially confound the inference of net plantarflexor MTU power from inverse dynamics ankle power. However, other methodological limitations may cause inverse dynamics to overestimate net MTU power; for instance, due to rigid-body foot assumptions. Moving forward, the EMG-driven modeling approach presented could be applied to understand other tasks or larger multiarticular MTUs.

CONTIN XPCS: Software for Inverse Transform Analysis of X-Ray Photon Correlation Spectroscopy Dynamics

PubMed Central

Narayanan, Suresh; Zhang, Fan; Kuzmenko, Ivan; Ilavsky, Jan

2018-01-01

X-ray photon correlation spectroscopy (XPCS) and dynamic light scattering (DLS) both reveal dynamics using coherent scattering, but X-rays permit investigating of dynamics in a much more diverse array of materials. Heterogeneous dynamics occur in many such materials, and we showed how classic tools employed in analysis of heterogeneous DLS dynamics extend to XPCS, revealing additional information that conventional Kohlrausch exponential fitting obscures. This work presents the software implementation of inverse transform analysis of XPCS data called CONTIN XPCS, an extension of traditional CONTIN that accommodates dynamics encountered in equilibrium XPCS measurements. PMID:29875507

CONTIN XPCS: Software for Inverse Transform Analysis of X-Ray Photon Correlation Spectroscopy Dynamics.

PubMed

Andrews, Ross N; Narayanan, Suresh; Zhang, Fan; Kuzmenko, Ivan; Ilavsky, Jan

2018-02-01

X-ray photon correlation spectroscopy (XPCS) and dynamic light scattering (DLS) both reveal dynamics using coherent scattering, but X-rays permit investigating of dynamics in a much more diverse array of materials. Heterogeneous dynamics occur in many such materials, and we showed how classic tools employed in analysis of heterogeneous DLS dynamics extend to XPCS, revealing additional information that conventional Kohlrausch exponential fitting obscures. This work presents the software implementation of inverse transform analysis of XPCS data called CONTIN XPCS, an extension of traditional CONTIN that accommodates dynamics encountered in equilibrium XPCS measurements.

Prognostic Significance of Spot Urine Na/K for Longitudinal Changes in Blood Pressure and Renal Function: The Nagahama Study.

PubMed

Tabara, Yasuharu; Takahashi, Yoshimitsu; Setoh, Kazuya; Kawaguchi, Takahisa; Kosugi, Shinji; Nakayama, Takeo; Matsuda, Fumihiko

2017-09-01

Urinary sodium-to-potassium ratio (Na/K) represents a simple measure of sodium load and has been reported to be associated with blood pressure (BP) levels in a cross-sectional setting even with spot measurements. The aim of the present large-scale cohort study is to determine prognostic significance of spot urine Na/K for longitudinal changes in BP levels and renal function. The present study population consisted of 7,063 individuals from the general population. Clinical parameters were measured at baseline and at a follow-up interval of 5 years. Mean systolic BP was slightly increased during the follow-up period (overall, 124 ± 17 to 125 ± 18 mm Hg; nontreated participants, 119 ± 15 to 122 ± 17 mm Hg). Although, the urinary Na/K demonstrated a linear association with BP in a cross-sectional analysis (P < 0.001), analysis of repeated measured BP values identified baseline Na/K * time interaction, i.e., an intraindividual effect, as an inverse determinant (F = 76.9, P < 0.001) independently of hypertension status and fasting conditions possibly due to regression to the mean of temporary high baseline Na/K values at baseline. Spot urine Na/K values were found to be positively associated with renal function in a cross-sectional analysis (P < 0.001). Although baseline Na/K * time interaction showed inverse associated with renal functional decline (F = 85.8, P < 0.001), this inverse association might not represent physiological relationship in likewise fashion with the analysis for BP. Spot urine Na/K may have limited utility as a prognostic marker of longitudinal BP change, as well as renal functional decline. © American Journal of Hypertension, Ltd 2017. All rights reserved. For Permissions, please email: journals.permissions@oup.com

The Omega-3 Index Is Inversely Associated with Depressive Symptoms among Individuals with Elevated Oxidative Stress Biomarkers123

PubMed Central

Bigornia, Sherman J; Falcón, Luis M; Ordovás, José M; Lai, Chao-Qiang

2016-01-01

Background: Omega-3 (n–3) fatty acid (FA) consumption is thought to improve depressive symptoms. However, current evidence is limited, and whether this association exists among Puerto Ricans, a population burdened by depression, remains uncertain. Objectives: We examined the association between ω-3 FA biomarkers and depressive symptoms as well as the potential influence of oxidative stress. Methods: Baseline and longitudinal analyses were conducted in the Boston Puerto Rican Health Study (n = 787; participants aged 57 ± 0.52 y, 73% women). Urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) concentration, a measure of oxidative stress, and erythrocyte FA composition were collected at baseline. We calculated the omega-3 index as the sum of eicosapentaenoic and docosahexaenoic acids, expressed as a percentage of total FAs. Baseline and 2-y depressive symptoms were characterized by using the Center for Epidemiological Studies–Depression Scale (CES-D). Statistical analyses included linear and logistic regression. Results: Urinary 8-OHdG concentration tended to modify the relation between the erythrocyte omega-3 index and baseline CES-D score (P-interaction = 0.10). In stratified analyses, the omega-3 index was inversely associated with CES-D score (β = −1.74, SE = 0.88; P = 0.02) among those in the top quartile of 8-OHdG concentration but not among those in the lower quartiles. The relation between the omega-3 index and CES-D at 2 y was more clearly modified by 8-OHdG concentration (P-interaction = 0.04), where the omega-3 index was inversely associated with CES-D at 2 y, adjusted for baseline (β = −1.66, SE = 0.66; P = 0.02), only among those with elevated 8-OHdG concentrations. Among individuals not taking antidepressant medications and in the top tertile of urinary 8-OHdG concentration, the omega-3 index was associated with significantly lower odds of a CES-D score ≥16 at baseline (OR: 0.72; 95% CI: 0.53, 0.96) but not at 2 y (OR: 0.83; 95% CI: 0.60, 1.15). Conclusions: An inverse association between the omega-3 index and depressive symptoms was observed among participants with elevated oxidative stress biomarkers. These data suggest that oxidative stress status may identify those who might benefit from ω-3 FA consumption to improve depressive symptoms. PMID:26936135

Cross-sectional and longitudinal relationships of body mass index with glycemic control in children and adolescents with type 1 diabetes mellitus.

PubMed

Nansel, T R; Lipsky, L M; Iannotti, R J

2013-04-01

Weight gain is an oft-cited outcome of improved glycemic control in adults with type 1 diabetes, though few studies have investigated this in youth. The purpose of this paper was to examine cross-sectional and longitudinal associations of body mass index (BMI, kg/m(2)) with glycemic control in youth with type 1 diabetes (n=340, 12.5 ± 1.7 year, 49% female, duration ≥ 1 year) participating in a 2-year multi-center intervention study targeting family diabetes management. BMI was calculated from height and weight measured at clinic visits. Glycohemoglobin (HbA1c) at each visit was assayed centrally. Cross-sectional associations of baseline BMI with glycemic control, and of change in BMI and HbA1c with baseline values, were examined. Longitudinal associations of time-varying BMI and HbA1c were examined using a multilevel linear mixed effects model controlling for time-varying time (months), insulin dose (units/kg/day), regimen, Tanner stage, and time invariant baseline diabetes duration, BMI, treatment group and sociodemographic characteristics. Baseline HbA1c was unrelated to baseline BMI, but was related positively to subsequent BMI change (p=0.04) and inversely to HbA1c change (p=0.002). Baseline BMI was inversely related to BMI change (p=0.01) and unrelated to HbA1c change. In multilevel regression, BMI was related inversely to HbA1c (%) (β ± SE=-0.11 ± 0.02, p<0.001) and positively to insulin dose (0.23 ± 0.07, p=0.001). In the treatment group only, BMI was positively related to pump regimen (0.18 ± 0.08, p=0.02). Increased insulin administered to improve glycemic control may contribute to increased BMI in youth with type 1 diabetes, indicating the importance of determining ways to minimize weight gain while optimizing glycemic control. Published by Elsevier Ireland Ltd.

General Theory and Algorithms for the Non-Casual Inversion, Slewing and Control of Space-Based Articulated Structures

DTIC Science & Technology

1993-10-01

Structures: Simultaneous Trajectory Tracking and Vibration Reduction ... 10 3 . Buckling Control of a Flexible Beam Using Piezoelectric Actuators...bounded solution for the inverse dynamic torque has to be non-causal. Bayo, et. al. [ 3 ], extended the inverse dynamics to planar, multiple-link systems...presented by &ayo and Moulin [4] for the single link system, with provisions for 3 extension to multiple link systems. An equivalent time domain approach for

Getting in shape: Reconstructing three-dimensional long-track speed skating kinematics by comparing several body pose reconstruction techniques.

PubMed

van der Kruk, E; Schwab, A L; van der Helm, F C T; Veeger, H E J

2018-03-01

In gait studies body pose reconstruction (BPR) techniques have been widely explored, but no previous protocols have been developed for speed skating, while the peculiarities of the skating posture and technique do not automatically allow for the transfer of the results of those explorations to kinematic skating data. The aim of this paper is to determine the best procedure for body pose reconstruction and inverse dynamics of speed skating, and to what extend this choice influences the estimation of joint power. The results show that an eight body segment model together with a global optimization method with revolute joint in the knee and in the lumbosacral joint, while keeping the other joints spherical, would be the most realistic model to use for the inverse kinematics in speed skating. To determine joint power, this method should be combined with a least-square error method for the inverse dynamics. Reporting on the BPR technique and the inverse dynamic method is crucial to enable comparison between studies. Our data showed an underestimation of up to 74% in mean joint power when no optimization procedure was applied for BPR and an underestimation of up to 31% in mean joint power when a bottom-up inverse dynamics method was chosen instead of a least square error approach. Although these results are aimed at speed skating, reporting on the BPR procedure and the inverse dynamics method, together with setting a golden standard should be common practice in all human movement research to allow comparison between studies. Copyright © 2018 Elsevier Ltd. All rights reserved.

What you feel is what you see: inverse dynamics estimation underlies the resistive sensation of a delayed cursor.

PubMed

Takamuku, Shinya; Gomi, Hiroaki

2015-07-22

How our central nervous system (CNS) learns and exploits relationships between force and motion is a fundamental issue in computational neuroscience. While several lines of evidence have suggested that the CNS predicts motion states and signals from motor commands for control and perception (forward dynamics), it remains controversial whether it also performs the 'inverse' computation, i.e. the estimation of force from motion (inverse dynamics). Here, we show that the resistive sensation we experience while moving a delayed cursor, perceived purely from the change in visual motion, provides evidence of the inverse computation. To clearly specify the computational process underlying the sensation, we systematically varied the visual feedback and examined its effect on the strength of the sensation. In contrast to the prevailing theory that sensory prediction errors modulate our perception, the sensation did not correlate with errors in cursor motion due to the delay. Instead, it correlated with the amount of exposure to the forward acceleration of the cursor. This indicates that the delayed cursor is interpreted as a mechanical load, and the sensation represents its visually implied reaction force. Namely, the CNS automatically computes inverse dynamics, using visually detected motions, to monitor the dynamic forces involved in our actions. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Inverse transformation: unleashing spatially heterogeneous dynamics with an alternative approach to XPCS data analysis

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

Andrews, Ross N.; Narayanan, Suresh; Zhang, Fan

X-ray photon correlation spectroscopy (XPCS), an extension of dynamic light scattering (DLS) in the X-ray regime, detects temporal intensity fluctuations of coherent speckles and provides scattering-vector-dependent sample dynamics at length scales smaller than DLS. The penetrating power of X-rays enables XPCS to probe the dynamics in a broad array of materials, including polymers, glasses and metal alloys, where attempts to describe the dynamics with a simple exponential fit usually fail. In these cases, the prevailing XPCS data analysis approach employs stretched or compressed exponential decay functions (Kohlrausch functions), which implicitly assume homogeneous dynamics. This paper proposes an alternative analysis schememore » based upon inverse Laplace or Gaussian transformation for elucidating heterogeneous distributions of dynamic time scales in XPCS, an approach analogous to the CONTIN algorithm widely accepted in the analysis of DLS from polydisperse and multimodal systems. In conclusion, using XPCS data measured from colloidal gels, it is demonstrated that the inverse transform approach reveals hidden multimodal dynamics in materials, unleashing the full potential of XPCS.« less

Inverse transformation: unleashing spatially heterogeneous dynamics with an alternative approach to XPCS data analysis

DOE PAGES

Andrews, Ross N.; Narayanan, Suresh; Zhang, Fan; ...

2018-02-01

X-ray photon correlation spectroscopy (XPCS), an extension of dynamic light scattering (DLS) in the X-ray regime, detects temporal intensity fluctuations of coherent speckles and provides scattering-vector-dependent sample dynamics at length scales smaller than DLS. The penetrating power of X-rays enables XPCS to probe the dynamics in a broad array of materials, including polymers, glasses and metal alloys, where attempts to describe the dynamics with a simple exponential fit usually fail. In these cases, the prevailing XPCS data analysis approach employs stretched or compressed exponential decay functions (Kohlrausch functions), which implicitly assume homogeneous dynamics. This paper proposes an alternative analysis schememore » based upon inverse Laplace or Gaussian transformation for elucidating heterogeneous distributions of dynamic time scales in XPCS, an approach analogous to the CONTIN algorithm widely accepted in the analysis of DLS from polydisperse and multimodal systems. In conclusion, using XPCS data measured from colloidal gels, it is demonstrated that the inverse transform approach reveals hidden multimodal dynamics in materials, unleashing the full potential of XPCS.« less

Control of a flexible bracing manipulator: Integration of current research work to realize the bracing manipulator

NASA Technical Reports Server (NTRS)

Kwon, Dong-Soo

1991-01-01

All research results about flexible manipulator control were integrated to show a control scenario of a bracing manipulator. First, dynamic analysis of a flexible manipulator was done for modeling. Second, from the dynamic model, the inverse dynamic equation was derived, and the time domain inverse dynamic method was proposed for the calculation of the feedforward torque and the desired flexible coordinate trajectories. Third, a tracking controller was designed by combining the inverse dynamic feedforward control with the joint feedback control. The control scheme was applied to the tip position control of a single link flexible manipulator for zero and non-zero initial condition cases. Finally, the contact control scheme was added to the position tracking control. A control scenario of a bracing manipulator is provided and evaluated through simulation and experiment on a single link flexible manipulator.

Spatial operator factorization and inversion of the manipulator mass matrix

NASA Technical Reports Server (NTRS)

Rodriguez, Guillermo; Kreutz-Delgado, Kenneth

1992-01-01

This paper advances two linear operator factorizations of the manipulator mass matrix. Embedded in the factorizations are many of the techniques that are regarded as very efficient computational solutions to inverse and forward dynamics problems. The operator factorizations provide a high-level architectural understanding of the mass matrix and its inverse, which is not visible in the detailed algorithms. They also lead to a new approach to the development of computer programs or organize complexity in robot dynamics.

An inverse dynamics approach to trajectory optimization for an aerospace plane

NASA Technical Reports Server (NTRS)

Lu, Ping

1992-01-01

An inverse dynamics approach for trajectory optimization is proposed. This technique can be useful in many difficult trajectory optimization and control problems. The application of the approach is exemplified by ascent trajectory optimization for an aerospace plane. Both minimum-fuel and minimax types of performance indices are considered. When rocket augmentation is available for ascent, it is shown that accurate orbital insertion can be achieved through the inverse control of the rocket in the presence of disturbances.

Inverse dynamic substructuring using the direct hybrid assembly in the frequency domain

NASA Astrophysics Data System (ADS)

D'Ambrogio, Walter; Fregolent, Annalisa

2014-04-01

The paper deals with the identification of the dynamic behaviour of a structural subsystem, starting from the known dynamic behaviour of both the coupled system and the remaining part of the structural system (residual subsystem). This topic is also known as decoupling problem, subsystem subtraction or inverse dynamic substructuring. Whenever it is necessary to combine numerical models (e.g. FEM) and test models (e.g. FRFs), one speaks of experimental dynamic substructuring. Substructure decoupling techniques can be classified as inverse coupling or direct decoupling techniques. In inverse coupling, the equations describing the coupling problem are rearranged to isolate the unknown substructure instead of the coupled structure. On the contrary, direct decoupling consists in adding to the coupled system a fictitious subsystem that is the negative of the residual subsystem. Starting from a reduced version of the 3-field formulation (dynamic equilibrium using FRFs, compatibility and equilibrium of interface forces), a direct hybrid assembly is developed by requiring that both compatibility and equilibrium conditions are satisfied exactly, either at coupling DoFs only, or at additional internal DoFs of the residual subsystem. Equilibrium and compatibility DoFs might not be the same: this generates the so-called non-collocated approach. The technique is applied using experimental data from an assembled system made by a plate and a rigid mass.

Do the wealthy have a health advantage? Cardiovascular disease risk factors and wealth.

PubMed

Hajat, A; Kaufman, J S; Rose, K M; Siddiqi, A; Thomas, J C

2010-12-01

The use of wealth as a measure of socioeconomic status (SES) remains uncommon in epidemiological studies. When used, wealth is often measured crudely and at a single point in time. Our study explores the relationship between wealth and three cardiovascular disease (CVD) risk factors (smoking, obesity and hypertension) in a US population. We improve upon existing literature by using a detailed and validated measure of wealth in a longitudinal setting. We used four waves of data from the Panel Study of Income Dynamics (PSID) collected between 1999 and 2005. Inverse probability weights were employed to control for time-varying confounding and to estimate both relative (risk ratio) and absolute (risk difference) measures of effect. Wealth was defined as inflation-adjusted net worth and specified as a six category variable: one category for those with less than or equal to zero wealth and quintiles of positive wealth. After adjusting for income and other time-varying confounders, as well as baseline covariates, the risk of becoming obese was inversely related to wealth. There was a 40%-89% higher risk of becoming obese among the less wealthy relative to the wealthiest quintile and 11 to 25 excess cases (per 1000 persons) among the less wealthy groups over six years of follow up. Smoking initiation had similar but more moderate effects; risk ratios and differences both revealed a smaller magnitude of effect compared to obesity. Of the three CVD risk factors examined here, hypertension incidence had the weakest association with wealth, showing a smaller increased risk and fewer excess cases among the less wealthy groups. In conclusion, this study found a strong inverse association between wealth and obesity incidence, a moderate inverse association between wealth and smoking initiation and a weak inverse association between wealth and hypertension incidence after controlling for income and other time-varying confounders. Copyright © 2010 Elsevier Ltd. All rights reserved.

Performance recovery of a class of uncertain non-affine systems with unmodelled dynamics: an indirect dynamic inversion method

NASA Astrophysics Data System (ADS)

Yi, Bowen; Lin, Shuyi; Yang, Bo; Zhang, Weidong

2018-02-01

This paper presents an output feedback indirect dynamic inversion (IDI) approach for a class of uncertain nonaffine systems with input unmodelled dynamics. Compared with previous approaches to achieve performance recovery, the proposed method aims at dealing with a broader class of nonaffine-in-control systems with triangular structure. An IDI state feedback law is designed first, in which less knowledge of the model plant is needed compared to earlier approximate dynamic inversion methods, thus yielding more robust performance. After that, an extended high-gain observer is designed to accomplish the task with output feedback. Finally, we prove that the designed IDI controller is equivalent to an adaptive proportional-integral (PI) controller, with respect to both time response equivalence and robustness equivalence. The conclusion implies that for the studied strict-feedback non-affine systems with unmodelled dynamics, there always exits a PI controller to stabilise the systems. The effectiveness and benefits of the designed approach are verified by three examples.

Polarimetric SAR Interferometry Evaluation in Mangroves

NASA Technical Reports Server (NTRS)

Lee, Seung-Kuk; Fatoyinbo,Temilola; Osmanoglu, Batuhan; Sun, Guoqing

2014-01-01

TanDEM-X (TDX) enables to generate an interferometric coherence without temporal decorrelation effect that is the most critical factor for a successful Pol-InSAR inversion, as have recently been used for forest parameter retrieval. This paper presents mangrove forest height estimation only using single-pass/single-baseline/dual-polarization TDX data by means of new dual-Pol-InSAR inversion technique. To overcome a lack of one polarization in a conventional Pol- InSAR inversion (i.e. an underdetermined problem), the ground phase in the Pol-InSAR model is directly estimated from TDX interferograms assuming flat underlying topography in mangrove forest. The inversion result is validated against lidar measurement data (NASA's G-LiHT data).

Association between body weight and composition and plasma 25-hydroxyvitamin D level in the Diabetes Prevention Program.

PubMed

Ceglia, Lisa; Nelson, Jason; Ware, James; Alysandratos, Konstantinos-Dionysios; Bray, George A; Garganta, Cheryl; Nathan, David M; Hu, Frank B; Dawson-Hughes, Bess; Pittas, Anastassios G

2017-02-01

We examined associations between body weight and plasma 25-hydroxyvitamin D concentration (25OHD) in prediabetes and sought to estimate the impact of adiposity on these associations. The study was conducted in the placebo (n = 1082) and intensive lifestyle (n = 1079) groups of the Diabetes Prevention Program (DPP), a multicenter trial to prevent type 2 diabetes in adults with prediabetes. Weight and 25OHD were measured at baseline, month 6, years 1 and 2. In a subset (n = 584), visceral (VAT) and subcutaneous (SAT) adiposity were assessed by computed tomography at baseline and year 1. In cross-sectional analyses, baseline body weight, total fat, VAT, and SAT were inversely associated with plasma 25OHD concentration after multivariable adjustment. VAT accounted for 40 % [95 % CI 11, 69] of the association of body weight with plasma 25OHD concentration. There was no significant contribution by total fat or SAT. Two-year changes in plasma 25OHD concentration varied inversely with changes in body weight (p < 0.0001). One-year changes in total fat, VAT, or SAT were not significant mediators of the association between change in plasma 25OHD concentration and body weight. Our study found an inverse association between body weight and plasma 25OHD concentration at baseline and over a 2-year period in adults with prediabetes. These findings in the DPP, a weight loss intervention study, raise the possibility that weight loss increases plasma 25OHD concentration. Whether adiposity mediates this association remains inconclusive.

Positive and Negative Affect More Concurrent among Blacks than Whites.

PubMed

Lankarani, Maryam Moghani; Assari, Shervin

2017-08-01

While positive and negative affect are inversely linked, people may experience and report both positive and negative emotions simultaneously. However, it is unknown if race alters the magnitude of the association between positive and negative affect. The current study compared Black and White Americans for the association between positive and negative affect. We used data from MIDUS (Midlife in the United States), a national study of Americans with an age range of 25 to 75. A total number of 7108 individuals were followed for 10 years from 1995 to 2004. Positive and negative affect was measured at baseline (1995) and follow-up (2004). Demographic (age and gender), socioeconomic (education and income) as well as health (self-rated health, chronic medical conditions, and body mass index) factors measured at baseline were covariates. A series of linear regressions were used to test the moderating effect of race on the reciprocal association between positive and negative affect at baseline and over time, net of covariates. In the pooled sample, positive and negative affect showed inverse correlation at baseline and over time, net of covariates. Blacks and Whites differed in the magnitude of the association between positive and negative affect, with weaker inverse associations among Blacks compared to Whites, beyond all covariates. Weaker reciprocal association between positive and negative affect in Blacks compared to Whites has implications for cross-racial measurement of affect and mood, including depression. Depression screening programs should be aware that race alters the concordance between positive and negative affect domains and that Blacks endorse higher levels of positive affect compared to Whites in the presence of high negative affect.

Association between body weight and composition and plasma 25-hydroxyvitamin D level in the Diabetes Prevention Program

PubMed Central

CEGLIA, LISA; NELSON, JASON; WARE, JAMES; ALYSANDRATOS, KONSTANTINOS-DIONYSIOS; BRAY, GEORGE A.; GARGANTA, CHERYL; NATHAN, DAVID M.; HU, FRANK B; DAWSON-HUGHES, BESS; PITTAS, ANASTASSIOS G.

2016-01-01

Objective We examined associations between body weight and plasma 25-hydroxyvitamin D concentration (25OHD) in pre-diabetes and sought to estimate the impact of adiposity on these associations. Methods The study was conducted in the placebo (n=1,082) and intensive lifestyle (n=1,079) groups of the Diabetes Prevention Program (DPP), a multicenter trial to prevent type 2 diabetes in adults with pre-diabetes. Weight and 25OHD were measured at baseline, month 6, years 1 and 2. In a subset (n=584), visceral [VAT] and subcutaneous [SAT] adiposity were assessed by computed tomography at baseline and year 1. Results In cross-sectional analyses, baseline body weight, total fat, VAT, and SAT were inversely associated with plasma 25OHD concentration after multivariable adjustment. VAT accounted for 40% [95% CI 11, 69] of the association of body weight with plasma 25OHD concentration. There was no significant contribution by total fat or SAT. Two-year changes in plasma 25OHD concentration varied inversely with changes in body weight (p<0.0001). One-year changes in total fat, VAT, or SAT were not significant mediators of the association between change in plasma 25OHD concentration and body weight. Conclusion Our study found an inverse association between body weight and plasma 25OHD concentration at baseline and over a 2-year period in adults with pre-diabetes. These findings in the DPP, a weight loss intervention study, raise the possibility that weight loss increases plasma 25OHD concentration. Whether adiposity mediates this association remains inconclusive. PMID:26525562

Efficacy of an ankle brace with a subtalar locking system in inversion control in dynamic movements.

PubMed

Zhang, Songning; Wortley, Michael; Chen, Qingjian; Freedman, Julia

2009-12-01

Controlled laboratory study. To examine effectiveness of an ankle brace with a subtalar locking system in restricting ankle inversion during passive and dynamic movements. Semirigid ankle braces are considered more effective in restricting ankle inversion than other types of brace, but a semirigid brace with a subtalar locking system may be even more effective. Nineteen healthy subjects with no history of major lower extremity injuries were included in the study. Participants performed 5 trials of an ankle inversion drop test and a lateral-cutting movement without wearing a brace and while wearing either the Element (with the subtalar locking system), a Functional ankle brace, or an ASO ankle brace. A 2-way repeated-measures analysis of variance (ANOVA) was used to assess brace differences (P?.05). All 3 braces significantly reduced total passive ankle frontal plane range of motion (ROM), with the Element ankle brace being the most effective. For the inversion drop the results showed significant reductions in peak ankle inversion angle and inversion ROM for all 3 braces compared to the no brace condition; and the peak inversion velocity was also reduced for the Element brace and the Functional brace. In the lateral-cutting movement, a small but significant reduction of the peak inversion angle in early foot contact and the peak eversion velocity at push-off were seen when wearing the Element and the Functional ankle braces compared to the no brace condition. Peak vertical ground reaction force was reduced for the Element brace compared to the ASO brace and the no brace conditions. These results suggest that the tested ankle braces, especially the Element brace, provided effective restriction of ankle inversion during both passive and dynamic movements.

Handling Qualities Evaluations of Low Complexity Model Reference Adaptive Controllers for Reduced Pitch and Roll Damping Scenarios

NASA Technical Reports Server (NTRS)

Hanson, Curt; Schaefer, Jacob; Burken, John J.; Johnson, Marcus; Nguyen, Nhan

2011-01-01

National Aeronautics and Space Administration (NASA) researchers have conducted a series of flight experiments designed to study the effects of varying levels of adaptive controller complexity on the performance and handling qualities of an aircraft under various simulated failure or damage conditions. A baseline, nonlinear dynamic inversion controller was augmented with three variations of a model reference adaptive control design. The simplest design consisted of a single adaptive parameter in each of the pitch and roll axes computed using a basic gradient-based update law. A second design was built upon the first by increasing the complexity of the update law. The third and most complex design added an additional adaptive parameter to each axis. Flight tests were conducted using NASA s Full-scale Advanced Systems Testbed, a highly modified F-18 aircraft that contains a research flight control system capable of housing advanced flight controls experiments. Each controller was evaluated against a suite of simulated failures and damage ranging from destabilization of the pitch and roll axes to significant coupling between the axes. Two pilots evaluated the three adaptive controllers as well as the non-adaptive baseline controller in a variety of dynamic maneuvers and precision flying tasks designed to uncover potential deficiencies in the handling qualities of the aircraft, and adverse interactions between the pilot and the adaptive controllers. The work was completed as part of the Integrated Resilient Aircraft Control Project under NASA s Aviation Safety Program.

Relationship Between Lymph Node Volume and Pain Following Certolizumab Therapy for Rheumatoid Arthritis Flare: A Pilot Study.

PubMed

Rahimi, Homaira; Dieudonne, Gregory; Kheyfits, Valeriy; Bouta, Echoe M; Wood, Ronald W; Barrett, Rick; Moorehead, Sharon; Schwarz, Edward M; Ritchlin, Christopher T

2016-01-01

The mechanisms that trigger flare in rheumatoid arthritis (RA) are unknown. In murine arthritis models, dysfunctional lymph node (LN) drainage is associated with joint flare. To examine if LN alterations are associated with RA flare, we analyzed the change in LN volume via contrast-enhanced magnetic resonance imaging (CE-MRI) in patients with active joint flare at baseline and 16 weeks after certolizumab pegol (CZP) therapy. We also assessed the changes in popliteal or epitrochlear LN volumes versus the Rheumatoid and Arthritis Outcome Score (RAOS) (knee), or the Michigan Hand Questionnaire (MHQ; wrist/hand), and Disease Activity Score 28 (DAS28), at baseline and 16 weeks. Total LN volume in 7 of 10 patients with measurable LN on CE-MRI significantly decreased 16 weeks after CZP therapy (mean decrease 37%; P = 0.0019). Improvement in knee pain measured by the RAOS ( P = 0.03) inversely correlated with a decrease in total popliteal LN volume ( R 2 = 0.94). All patients demonstrated significant improvement in DAS28 (mean decrease 1.48; P = 0.0002). For flare in the hand, significant improvement in activities of daily living (ADL) as measured by the MHQ was observed (left hand mean improvement 20%; P = 0.02; right hand mean improvement 37%; P = 0.03). RA patients with the smallest change in LN volume during anti-tumor necrosis factor (anti-TNF) therapy experienced the greatest pain relief in symptomatic knee joints. Moreover, the remarkably linear inverse correlation between LN volume and joint pain observed in this small clinical pilot provides initial evidence to support the concept that dynamic changes in draining LN volume are a biomarker of clinical response to therapy in RA.

Full analogue electronic realisation of the Hodgkin-Huxley neuronal dynamics in weak-inversion CMOS.

PubMed

Lazaridis, E; Drakakis, E M; Barahona, M

2007-01-01

This paper presents a non-linear analog synthesis path towards the modeling and full implementation of the Hodgkin-Huxley neuronal dynamics in silicon. The proposed circuits have been realized in weak-inversion CMOS technology and take advantage of both log-domain and translinear transistor-level techniques.

CONTIN XPCS: software for inverse transform analysis of X-ray photon correlation spectroscopy dynamics

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

Andrews, Ross N.; Narayanan, Suresh; Zhang, Fan

X-ray photon correlation spectroscopy (XPCS) and dynamic light scattering (DLS) reveal materials dynamics using coherent scattering, with XPCS permitting the investigation of dynamics in a more diverse array of materials than DLS. Heterogeneous dynamics occur in many material systems. The authors' recent work has shown how classic tools employed in the DLS analysis of heterogeneous dynamics can be extended to XPCS, revealing additional information that conventional Kohlrausch exponential fitting obscures. The present work describes the software implementation of inverse transform analysis of XPCS data. This software, calledCONTIN XPCS, is an extension of traditionalCONTINanalysis and accommodates the various dynamics encountered inmore » equilibrium XPCS measurements.« less

CONTIN XPCS: software for inverse transform analysis of X-ray photon correlation spectroscopy dynamics

DOE PAGES

Andrews, Ross N.; Narayanan, Suresh; Zhang, Fan; ...

2018-02-01

X-ray photon correlation spectroscopy (XPCS) and dynamic light scattering (DLS) reveal materials dynamics using coherent scattering, with XPCS permitting the investigation of dynamics in a more diverse array of materials than DLS. Heterogeneous dynamics occur in many material systems. The authors' recent work has shown how classic tools employed in the DLS analysis of heterogeneous dynamics can be extended to XPCS, revealing additional information that conventional Kohlrausch exponential fitting obscures. The present work describes the software implementation of inverse transform analysis of XPCS data. This software, calledCONTIN XPCS, is an extension of traditionalCONTINanalysis and accommodates the various dynamics encountered inmore » equilibrium XPCS measurements.« less

Phase Inversion of EPDM/PP Blends: Effect of Viscosity Ratio

NASA Astrophysics Data System (ADS)

Machado, Ana Vera; Antunes, Carla Filipa; van Duin, Martin

2011-07-01

EPDM/PP blends and TPVs with and without crosslinking, respectively, were prepared, in a batch mixer, using three different EPDM rubbers. EPDM/PP based TPVs were dynamic vulcanised using the resol/SnCl2 system. Samples were collected along the time in order to get information on the morphology evolution and crosslinking density during dynamic vulcanisation. The morphology was studied by SEM and the crosslink density by gel content. In the case of low viscosity EPDMs, crosslinking of the EPDM phase was retarded due to its low crosslinking efficiency. This delay on crosslinking reaction enables the observation of the various stages of the morphological mechanism that takes place during dynamic vulcanisation. It could be observed that phase inversion takes place via lamellar mechanism. More detailed insight on phase inversion mechanism during dynamic vulcanisation was accomplished.

Stability Result For Dynamic Inversion Devised to Control Large Flexible Aircraft

NASA Technical Reports Server (NTRS)

Gregory, Irene M.

2001-01-01

High performance aircraft of the future will be designed lighter, more maneuverable, and operate over an ever expanding flight envelope. One of the largest differences from the flight control perspective between current and future advanced aircraft is elasticity. Over the last decade, dynamic inversion methodology has gained considerable popularity in application to highly maneuverable fighter aircraft, which were treated as rigid vehicles. This paper is an initial attempt to establish global stability results for dynamic inversion methodology as applied to a large, flexible aircraft. This work builds on a previous result for rigid fighter aircraft and adds a new level of complexity that is the flexible aircraft dynamics, which cannot be ignored even in the most basic flight control. The results arise from observations of the control laws designed for a new generation of the High-Speed Civil Transport aircraft.

Inferior olive mirrors joint dynamics to implement an inverse controller.

PubMed

Alvarez-Icaza, Rodrigo; Boahen, Kwabena

2012-10-01

To produce smooth and coordinated motion, our nervous systems need to generate precisely timed muscle activation patterns that, due to axonal conduction delay, must be generated in a predictive and feedforward manner. Kawato proposed that the cerebellum accomplishes this by acting as an inverse controller that modulates descending motor commands to predictively drive the spinal cord such that the musculoskeletal dynamics are canceled out. This and other cerebellar theories do not, however, account for the rich biophysical properties expressed by the olivocerebellar complex's various cell types, making these theories difficult to verify experimentally. Here we propose that a multizonal microcomplex's (MZMC) inferior olivary neurons use their subthreshold oscillations to mirror a musculoskeletal joint's underdamped dynamics, thereby achieving inverse control. We used control theory to map a joint's inverse model onto an MZMC's biophysics, and we used biophysical modeling to confirm that inferior olivary neurons can express the dynamics required to mirror biomechanical joints. We then combined both techniques to predict how experimentally injecting current into the inferior olive would affect overall motor output performance. We found that this experimental manipulation unmasked a joint's natural dynamics, as observed by motor output ringing at the joint's natural frequency, with amplitude proportional to the amount of current. These results support the proposal that the cerebellum-in particular an MZMC-is an inverse controller; the results also provide a biophysical implementation for this controller and allow one to make an experimentally testable prediction.

Talofibular interval changes after acute ankle sprain: a stress ultrasonography study of ankle laxity.

PubMed

Croy, Theodore; Saliba, Susan; Saliba, Ethan; Anderson, Mark W; Hertel, Jay

2013-11-01

Quantifying talocrural joint laxity after ankle sprain is problematic. Stress ultrasonography (US) can image the lateral talocrural joint and allow the measurement of the talofibular interval, which may suggest injury to the anterior talofibular ligament (ATFL). The acute talofibular interval changes after lateral ankle sprain are unknown. Twenty-five participants (9 male, 16 female; age 21.8 ± 3.2 y, height 167.8 ± 34.1 cm, mass 72.7 ± 13.8 kg) with 27 acute, lateral ankle injuries underwent bilateral stress US imaging at baseline (<7 d) and on the affected ankle at 3 wk and 6 wk from injury in 3 ankle conditions: neutral, anterior drawer, and inversion. Talofibular interval (mm) was measured using imaging software and self-reported function (activities of daily living [ADL] and sports) by the Foot and Ankle Ability Measure (FAAM). The talofibular interval increased with anterior-drawer stress in the involved ankle (22.65 ± 3.75 mm; P = .017) over the uninvolved ankle (19.45 ± 2.35 mm; limb × position F1,26 = 4.9, P = .035) at baseline. Inversion stress also resulted in greater interval changes (23.41 ± 2.81 mm) than in the uninvolved ankles (21.13 ± 2.08 mm). A main effect for time was observed for inversion (F2,52 = 4.3, P = .019, 21.93 ± 2.24 mm) but not for anterior drawer (F2,52 = 3.1, P = .055, 21.18 ± 2.34 mm). A significant reduction in the talofibular interval took place between baseline and week 3 inversion measurements only (F1,26 = 5.6, P = .026). FAAM-ADL and sports results increased significantly from baseline to wk 3 (21.9 ± 16.2, P < .0001 and 23.8 ± 16.9, P < .0001) and from wk 3 to wk 6 (2.5 ± 4.4, P = .009 and 10.5 ± 13.2, P = .001). Stress US methods identified increased talofibular interval changes suggestive of talocrural laxity and ATFL injury using anterior drawer and inversion stress that, despite significant improvements in self-reported function, only marginally improved during the 6 wk after ankle sprain. Stress US provides a safe, repeatable, and quantifiable method of measuring the talofibular interval and may augment manual stress examinations in acute ankle injuries.

Movement Characteristics Analysis and Dynamic Simulation of Collaborative Measuring Robot

NASA Astrophysics Data System (ADS)

guoqing, MA; li, LIU; zhenglin, YU; guohua, CAO; yanbin, ZHENG

2017-03-01

Human-machine collaboration is becoming increasingly more necessary, and so collaborative robot applications are also in high demand. We selected a UR10 robot as our research subject for this study. First, we applied D-H coordinate transformation of the robot to establish a link system, and we then used inverse transformation to solve the robot’s inverse kinematics and find all the joints. Use Lagrange method to analysis UR robot dynamics; use ADAMS multibody dynamics simulation software to dynamic simulation; verifying the correctness of the derived kinetic models.

Using CFD Surface Solutions to Shape Sonic Boom Signatures Propagated from Off-Body Pressure

NASA Technical Reports Server (NTRS)

Ordaz, Irian; Li, Wu

2013-01-01

The conceptual design of a low-boom and low-drag supersonic aircraft remains a challenge despite significant progress in recent years. Inverse design using reversed equivalent area and adjoint methods have been demonstrated to be effective in shaping the ground signature propagated from computational fluid dynamics (CFD) off-body pressure distributions. However, there is still a need to reduce the computational cost in the early stages of design to obtain a baseline that is feasible for low-boom shaping, and in the search for a robust low-boom design over the entire sonic boom footprint. The proposed design method addresses the need to reduce the computational cost for robust low-boom design by using surface pressure distributions from CFD solutions to shape sonic boom ground signatures propagated from CFD off-body pressure.

In-Flight Suppression of an Unstable F/A-18 Structural Mode Using the Space Launch System Adaptive Augmenting Control System

NASA Technical Reports Server (NTRS)

VanZwieten, Tannen S.; Gilligan, Eric T.; Wall, John H.; Miller, Christopher J.; Hanson, Curtis E.; Orr, Jeb S.

2015-01-01

NASA's Space Launch System (SLS) Flight Control System (FCS) includes an Adaptive Augmenting Control (AAC) component which employs a multiplicative gain update law to enhance the performance and robustness of the baseline control system for extreme off-nominal scenarios. The SLS FCS algorithm including AAC has been flight tested utilizing a specially outfitted F/A-18 fighter jet in which the pitch axis control of the aircraft was performed by a Non-linear Dynamic Inversion (NDI) controller, SLS reference models, and the SLS flight software prototype. This paper describes test cases from the research flight campaign in which the fundamental F/A-18 airframe structural mode was identified using post-flight frequency-domain reconstruction, amplified to result in closed loop instability, and suppressed in-flight by the SLS adaptive control system.

Multiple estimation channel decoupling and optimization method based on inverse system

NASA Astrophysics Data System (ADS)

Wu, Peng; Mu, Rongjun; Zhang, Xin; Deng, Yanpeng

2018-03-01

This paper addressed the intelligent autonomous navigation request of intelligent deformation missile, based on the intelligent deformation missile dynamics and kinematics modeling, navigation subsystem solution method and error modeling, and then focuses on the corresponding data fusion and decision fusion technology, decouples the sensitive channel of the filter input through the inverse system of design dynamics to reduce the influence of sudden change of the measurement information on the filter input. Then carrying out a series of simulation experiments, which verified the feasibility of the inverse system decoupling algorithm effectiveness.

Adiponectin Levels and Longitudinal Changes in Metabolic Syndrome: The Healthy Twin Study.

PubMed

Song, Yun-Mi; Lee, Kayoung; Sung, Joohon

2015-09-01

We investigated the association of plasma adiponectin levels with longitudinal changes in metabolic syndrome and the metabolic syndrome-related traits [insulin and homeostasis model assessment of insulin resistance (HOMA-IR)], as well as their genetic and environmental correlations. A total of 1030 Koreans (380 men and 650 women; 44.0 ± 12.7 years old) without diabetes of the Healthy Twin Study visited at baseline (2005-2010) and returned for a follow-up examination 3.7 ± 1.2 years later. Baseline plasma adiponectin, metabolic syndrome components [waist circumference (WC), glucose, blood pressure, high-density lipoprotein cholesterol (HDL-C), and triglycerides (TGs)] and metabolic syndrome-related traits were measured at baseline and follow-up. After adjusting for age, sex, smoking, alcohol consumption, physical activity, caloric intake, education level, body mass index (BMI), family history of diabetes, and changes in BMI, 1 standard deviation increment in baseline adiponectin levels was associated with 38-63% lower odds of incident and persistent metabolic syndrome. After additionally adjusting for the baseline levels of each trait, baseline adiponectin levels were inversely associated with WC, blood pressure, insulin, HOMA-IR, and TGs values at follow-up. After adjusting for age, sex, and baseline values of each trait or sum of metabolic syndrome components, baseline adiponectin levels exhibited significantly inverse genetic and environmental correlations with insulin, HOMA-IR, and HDL-C values and the sum of metabolic syndrome components at follow-up. High adiponectin levels reduce the risk of developing metabolic syndrome and having persistent metabolic syndrome and increase of metabolic syndrome-related traits over time. These associations may be explained by pleiotropic genetic mechanisms.

T2 relaxation time measurements are limited in monitoring progression, once advanced cartilage defects at the knee occur

PubMed Central

Jungmann, P.M.; Kraus, M.S.; Nardo, L.; Liebl, H.; Alizai, H.; Joseph, G.B.; Liu, F.; Lynch, J.; McCulloch, C.E.; Nevitt, M.C.; Link, T.M.

2014-01-01

Purpose To study the natural evolution of cartilage T2 relaxation times in knees with various extents of morphological cartilage abnormalities, assessed with 3T MRI from the Osteoarthritis Initiative. Materials and Methods Right knee MRIs of 245, 45–60 year old individuals without radiographic OA were included. Cartilage was segmented and T2 maps were generated in five compartments (patella, medial and lateral femoral condyle, medial and lateral tibia) at baseline and two-year follow-up. We examined the association of T2 values and two-year change of T2 values with various Whole-Organ MR Imaging Scores (WORMS). Statistical analysis was performed with ANOVA and Students t-tests. Results Higher baseline T2 was associated with more severe cartilage defects at baseline and subsequent cartilage loss (P<0.001). However, longitudinal T2 change was inversely associated with both baseline (P=0.038) and follow-up (P=0.002) severity of cartilage defects. Knees that developed new cartilage defects had smaller increases in T2 than subjects without defects (P=0.045). Individuals with higher baseline T2 showed smaller T2 increases over time (P<0.001). Conclusion An inverse correlation of longitudinal T2 changes versus baseline T2 values and morphological cartilage abnormalities suggests that once morphological cartilage defects occur, T2 values may be limited for evaluating further cartilage degradation. PMID:24038491

Performance evaluation of the inverse dynamics method for optimal spacecraft reorientation

NASA Astrophysics Data System (ADS)

Ventura, Jacopo; Romano, Marcello; Walter, Ulrich

2015-05-01

This paper investigates the application of the inverse dynamics in the virtual domain method to Euler angles, quaternions, and modified Rodrigues parameters for rapid optimal attitude trajectory generation for spacecraft reorientation maneuvers. The impact of the virtual domain and attitude representation is numerically investigated for both minimum time and minimum energy problems. Owing to the nature of the inverse dynamics method, it yields sub-optimal solutions for minimum time problems. Furthermore, the virtual domain improves the optimality of the solution, but at the cost of more computational time. The attitude representation also affects solution quality and computational speed. For minimum energy problems, the optimal solution can be obtained without the virtual domain with any considered attitude representation.

Feedback control laws for highly maneuverable aircraft

NASA Technical Reports Server (NTRS)

Garrard, William L.; Balas, Gary J.

1994-01-01

During the first half of the year, the investigators concentrated their efforts on completing the design of control laws for the longitudinal axis of the HARV. During the second half of the year they concentrated on the synthesis of control laws for the lateral-directional axes. The longitudinal control law design efforts can be briefly summarized as follows. Longitudinal control laws were developed for the HARV using mu synthesis design techniques coupled with dynamic inversion. An inner loop dynamic inversion controller was used to simplify the system dynamics by eliminating the aerodynamic nonlinearities and inertial cross coupling. Models of the errors resulting from uncertainties in the principal longitudinal aerodynamic terms were developed and included in the model of the HARV with the inner loop dynamic inversion controller. This resulted in an inner loop transfer function model which was an integrator with the modeling errors characterized as uncertainties in gain and phase. Outer loop controllers were then designed using mu synthesis to provide robustness to these modeling errors and give desired response to pilot inputs. Both pitch rate and angle of attack command following systems were designed. The following tasks have been accomplished for the lateral-directional controllers: inner and outer loop dynamic inversion controllers have been designed; an error model based on a linearized perturbation model of the inner loop system was derived; controllers for the inner loop system have been designed, using classical techniques, that control roll rate and Dutch roll response; the inner loop dynamic inversion and classical controllers have been implemented on the six degree of freedom simulation; and lateral-directional control allocation scheme has been developed based on minimizing required control effort.

What you feel is what you see: inverse dynamics estimation underlies the resistive sensation of a delayed cursor

PubMed Central

Takamuku, Shinya; Gomi, Hiroaki

2015-01-01

How our central nervous system (CNS) learns and exploits relationships between force and motion is a fundamental issue in computational neuroscience. While several lines of evidence have suggested that the CNS predicts motion states and signals from motor commands for control and perception (forward dynamics), it remains controversial whether it also performs the ‘inverse’ computation, i.e. the estimation of force from motion (inverse dynamics). Here, we show that the resistive sensation we experience while moving a delayed cursor, perceived purely from the change in visual motion, provides evidence of the inverse computation. To clearly specify the computational process underlying the sensation, we systematically varied the visual feedback and examined its effect on the strength of the sensation. In contrast to the prevailing theory that sensory prediction errors modulate our perception, the sensation did not correlate with errors in cursor motion due to the delay. Instead, it correlated with the amount of exposure to the forward acceleration of the cursor. This indicates that the delayed cursor is interpreted as a mechanical load, and the sensation represents its visually implied reaction force. Namely, the CNS automatically computes inverse dynamics, using visually detected motions, to monitor the dynamic forces involved in our actions. PMID:26156766

Robust, nonlinear, high angle-of-attack control design for a supermaneuverable vehicle

NASA Technical Reports Server (NTRS)

Adams, Richard J.

1993-01-01

High angle-of-attack flight control laws are developed for a supermaneuverable fighter aircraft. The methods of dynamic inversion and structured singular value synthesis are combined into an approach which addresses both the nonlinearity and robustness problems of flight at extreme operating conditions. The primary purpose of the dynamic inversion control elements is to linearize the vehicle response across the flight envelope. Structured singular value synthesis is used to design a dynamic controller which provides robust tracking to pilot commands. The resulting control system achieves desired flying qualities and guarantees a large margin of robustness to uncertainties for high angle-of-attack flight conditions. The results of linear simulation and structured singular value stability analysis are presented to demonstrate satisfaction of the design criteria. High fidelity nonlinear simulation results show that the combined dynamics inversion/structured singular value synthesis control law achieves a high level of performance in a realistic environment.

High effective inverse dynamics modelling for dual-arm robot

NASA Astrophysics Data System (ADS)

Shen, Haoyu; Liu, Yanli; Wu, Hongtao

2018-05-01

To deal with the problem of inverse dynamics modelling for dual arm robot, a recursive inverse dynamics modelling method based on decoupled natural orthogonal complement is presented. In this model, the concepts and methods of Decoupled Natural Orthogonal Complement matrices are used to eliminate the constraint forces in the Newton-Euler kinematic equations, and the screws is used to express the kinematic and dynamics variables. On this basis, the paper has developed a special simulation program with symbol software of Mathematica and conducted a simulation research on the a dual-arm robot. Simulation results show that the proposed method based on decoupled natural orthogonal complement can save an enormous amount of CPU time that was spent in computing compared with the recursive Newton-Euler kinematic equations and the results is correct and reasonable, which can verify the reliability and efficiency of the method.

Inverse dynamics of a 3 degree of freedom spatial flexible manipulator

NASA Technical Reports Server (NTRS)

Bayo, Eduardo; Serna, M.

1989-01-01

A technique is presented for solving the inverse dynamics and kinematics of 3 degree of freedom spatial flexible manipulator. The proposed method finds the joint torques necessary to produce a specified end effector motion. Since the inverse dynamic problem in elastic manipulators is closely coupled to the inverse kinematic problem, the solution of the first also renders the displacements and rotations at any point of the manipulator, including the joints. Furthermore the formulation is complete in the sense that it includes all the nonlinear terms due to the large rotation of the links. The Timoshenko beam theory is used to model the elastic characteristics, and the resulting equations of motion are discretized using the finite element method. An iterative solution scheme is proposed that relies on local linearization of the problem. The solution of each linearization is carried out in the frequency domain. The performance and capabilities of this technique are tested through simulation analysis. Results show the potential use of this method for the smooth motion control of space telerobots.

Control of a high beta maneuvering reentry vehicle using dynamic inversion.

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

Watts, Alfred Chapman

2005-05-01

The design of flight control systems for high performance maneuvering reentry vehicles presents a significant challenge to the control systems designer. These vehicles typically have a much higher ballistic coefficient than crewed vehicles like as the Space Shuttle or proposed crew return vehicles such as the X-38. Moreover, the missions of high performance vehicles usually require a steeper reentry flight path angle, followed by a pull-out into level flight. These vehicles then must transit the entire atmosphere and robustly perform the maneuvers required for the mission. The vehicles must also be flown with small static margins in order to performmore » the required maneuvers, which can result in highly nonlinear aerodynamic characteristics that frequently transition from being aerodynamically stable to unstable as angle of attack increases. The control system design technique of dynamic inversion has been applied successfully to both high performance aircraft and low beta reentry vehicles. The objective of this study was to explore the application of this technique to high performance maneuvering reentry vehicles, including the basic derivation of the dynamic inversion technique, followed by the extension of that technique to the use of tabular trim aerodynamic models in the controller. The dynamic inversion equations are developed for high performance vehicles and augmented to allow the selection of a desired response for the control system. A six degree of freedom simulation is used to evaluate the performance of the dynamic inversion approach, and results for both nominal and off nominal aerodynamic characteristics are presented.« less

Plasma lipid levels predict dysglycemia in a biracial cohort of nondiabetic subjects: Potential mechanisms

PubMed Central

Owei, Ibiye; Umekwe, Nkiru; Wan, Jim

2016-01-01

Dyslipidemia and dysglycemia are etiologically associated, but the direction, chronology, and mechanisms of the association are not fully understood. We, therefore, analyzed data from 335 healthy adults (184 black, 151 white) enrolled in the Pathobiology of Prediabetes in A Biracial Cohort study. Subjects underwent oral glucose tolerance test (OGTT) and were enrolled if they had normal fasting and 2-h plasma glucose levels. Assessments during year 1 included anthropometry, fasting lipid profile, insulin sensitivity, and insulin secretion. Thereafter, OGTT was assessed annually for 5.5 years. The primary outcome was occurrence of prediabetes (impaired fasting glucose or impaired glucose tolerance) or diabetes. During a mean follow-up of 2.62 years, 110 participants (32.8%) developed prediabetes (N = 100) or diabetes (N = 10). In multivariate logistic regression models, higher baseline low-density lipoprotein (LDL) cholesterol and triglyceride levels and lower HDL cholesterol levels significantly increased the risk of incident prediabetes. The combined relative risk (95% confidence interval [CI]) of prediabetes for participants with lower baseline HDL cholesterol (10th vs. 90th percentile), higher LDL cholesterol (90th vs. 10th percentile) and high triglycerides levels (90th vs. 10th percentile) was 4.12 (95% CI 1.61–10.56), P = 0.0032. At baseline, lipid values showed significant associations with measures of adiposity, glycemia, insulin sensitivity, and secretion. In both ethnic groups, waist circumference correlated positively with triglycerides and inversely with HDL cholesterol levels (P = 0.0004–<0.0001); fasting plasma glucose correlated positively with triglycerides and LDL cholesterol levels and inversely with HDL cholesterol levels (P = 0.006–<0.0001); insulin sensitivity correlated positively with HDL cholesterol and inversely with triglyceride levels (P < 0.0001), and insulin secretion correlated positively with triglycerides (P = 0.01) and inversely with HDL cholesterol (P < 0.0001). We conclude that a baseline lipidemic signature identifies normoglycemic individuals at high risk for future glycemic progression, via congruent associations with adiposity and glucoregulatory mechanisms. These findings suggest that early lifestyle intervention could ameliorate progressive dyslipidemia and dysglycemia. PMID:27430991

Viscous Design of TCA Configuration

NASA Technical Reports Server (NTRS)

Krist, Steven E.; Bauer, Steven X. S.; Campbell, Richard L.

1999-01-01

The goal in this effort is to redesign the baseline TCA configuration for improved performance at both supersonic and transonic cruise. Viscous analyses are conducted with OVERFLOW, a Navier-Stokes code for overset grids, using PEGSUS to compute the interpolations between overset grids. Viscous designs are conducted with OVERDISC, a script which couples OVERFLOW with the Constrained Direct Iterative Surface Curvature (CDISC) inverse design method. The successful execution of any computational fluid dynamics (CFD) based aerodynamic design method for complex configurations requires an efficient method for regenerating the computational grids to account for modifications to the configuration shape. The first section of this presentation deals with the automated regridding procedure used to generate overset grids for the fuselage/wing/diverter/nacelle configurations analysed in this effort. The second section outlines the procedures utilized to conduct OVERDISC inverse designs. The third section briefly covers the work conducted by Dick Campbell, in which a dual-point design at Mach 2.4 and 0.9 was attempted using OVERDISC; the initial configuration from which this design effort was started is an early version of the optimized shape for the TCA configuration developed by the Boeing Commercial Airplane Group (BCAG), which eventually evolved into the NCV design. The final section presents results from application of the Natural Flow Wing design philosophy to the TCA configuration.

Robust inverse kinematics using damped least squares with dynamic weighting

NASA Technical Reports Server (NTRS)

Schinstock, D. E.; Faddis, T. N.; Greenway, R. B.

1994-01-01

This paper presents a general method for calculating the inverse kinematics with singularity and joint limit robustness for both redundant and non-redundant serial-link manipulators. Damped least squares inverse of the Jacobian is used with dynamic weighting matrices in approximating the solution. This reduces specific joint differential vectors. The algorithm gives an exact solution away from the singularities and joint limits, and an approximate solution at or near the singularities and/or joint limits. The procedure is here implemented for a six d.o.f. teleoperator and a well behaved slave manipulator resulted under teleoperational control.

Investigation into the Effects of Weapon Setback on Various Materials and Geometries.

DTIC Science & Technology

1978-07-01

taking the Laplace Transform of the dynamic equation, rearrangement and taking the inverse transform to find the time-dependent strain. The "dynamic...taking the inverse transform of the above equation: ■»-«fa-to*« 1 E’ ♦ ¥®*> B’ (s+-fj- )(S2+f )T If we neglect the residual strain on the system...partial fractions yields: *t) --f (fr JC-> K, K2 —L_ + + K3 »+-^ s+i(f) s-i(f) performing the inverse transform yields: 4©[K,^> ♦ K2

Inverse problem of HIV cell dynamics using Genetic Algorithms

NASA Astrophysics Data System (ADS)

González, J. A.; Guzmán, F. S.

2017-01-01

In order to describe the cell dynamics of T-cells in a patient infected with HIV, we use a flavour of Perelson's model. This is a non-linear system of Ordinary Differential Equations that describes the evolution of healthy, latently infected, infected T-cell concentrations and the free viral cells. Different parameters in the equations give different dynamics. Considering the concentration of these types of cells is known for a particular patient, the inverse problem consists in estimating the parameters in the model. We solve this inverse problem using a Genetic Algorithm (GA) that minimizes the error between the solutions of the model and the data from the patient. These errors depend on the parameters of the GA, like mutation rate and population, although a detailed analysis of this dependence will be described elsewhere.

Increase in relative skeletal muscle mass over time and its inverse association with metabolic syndrome development: a 7-year retrospective cohort study.

PubMed

Kim, Gyuri; Lee, Seung-Eun; Jun, Ji Eun; Lee, You-Bin; Ahn, Jiyeon; Bae, Ji Cheol; Jin, Sang-Man; Hur, Kyu Yeon; Jee, Jae Hwan; Lee, Moon-Kyu; Kim, Jae Hyeon

2018-02-05

Skeletal muscle mass was negatively associated with metabolic syndrome prevalence in previous cross-sectional studies. The aim of this study was to investigate the impact of baseline skeletal muscle mass and changes in skeletal muscle mass over time on the development of metabolic syndrome in a large population-based 7-year cohort study. A total of 14,830 and 11,639 individuals who underwent health examinations at the Health Promotion Center at Samsung Medical Center, Seoul, Korea were included in the analyses of baseline skeletal muscle mass and those changes from baseline over 1 year, respectively. Skeletal muscle mass was estimated by bioelectrical impedance analysis and was presented as a skeletal muscle mass index (SMI), a body weight-adjusted appendicular skeletal muscle mass value. Using Cox regression models, hazard ratio for developing metabolic syndrome associated with SMI values at baseline or changes of SMI over a year was analyzed. During 7 years of follow-up, 20.1% of subjects developed metabolic syndrome. Compared to the lowest sex-specific SMI tertile at baseline, the highest sex-specific SMI tertile showed a significant inverse association with metabolic syndrome risk (adjusted hazard ratio [AHR] = 0.61, 95% confidence interval [CI] 0.54-0.68). Furthermore, compared with SMI changes < 0% over a year, multivariate-AHRs for metabolic syndrome development were 0.87 (95% CI 0.78-0.97) for 0-1% changes and 0.67 (0.56-0.79) for > 1% changes in SMI over 1 year after additionally adjusting for baseline SMI and glycometabolic parameters. An increase in relative skeletal muscle mass over time has a potential preventive effect on developing metabolic syndrome, independently of baseline skeletal muscle mass and glycometabolic parameters.

Dynamic baseline detection method for power data network service

NASA Astrophysics Data System (ADS)

Chen, Wei

2017-08-01

This paper proposes a dynamic baseline Traffic detection Method which is based on the historical traffic data for the Power data network. The method uses Cisco's NetFlow acquisition tool to collect the original historical traffic data from network element at fixed intervals. This method uses three dimensions information including the communication port, time, traffic (number of bytes or number of packets) t. By filtering, removing the deviation value, calculating the dynamic baseline value, comparing the actual value with the baseline value, the method can detect whether the current network traffic is abnormal.

A theoretical Deduction from the Hubble law based on a Modified Newtonian Dynamics with field of Yukawa inverse

NASA Astrophysics Data System (ADS)

Falcon, N.

2017-07-01

At cosmic scales the dynamics of the Universe are almost exclusively prescribed by the force of gravity; however the assumption of the law of gravitation, depending on the inverse of the distance, leads to the known problems of the rotation curves of galaxies and missing mass (dark matter). The problem of the coupling of gravity to changes in scale and deviations from the law of the inverse square is an old problem (Laplace, 1805; Seeliger 1898), which has motivated alternatives to Newtonian dynamics compatible with observations. The present paper postulates a modified Newtonian dynamics by adding an inverse Yukawa potential: U(r)≡U0(M)(r-r0)e-α/r is the the potential per unit mass (in N/kg) as a function of the barionic mass that causes the field, r0 is of the order of 50h-1 Mpc and alpha is a coupling constant of the order of 2.5 h-1 Mpc. This potential is zero within the solar system, slightly attractive at interstellar distances, very attractive in galactic range and repulsive at cosmic scales. Its origin is the barionic matter, it allows to include the Milgrow MoND theory to explain the rotation curves, it is compatible with the experiments Eovos type, and allows to deduce the law of Hubble to cosmic scales, in the form H0=100h km/s Mpc≍U0(M)/c, where U0(M)≍ 4pi×6.67 10-11m/s2, is obtained from the Laplace's equation, assuming that the gravitational force is the law of the inverse of the square plus a non-linear term type Yukawa inverse. It is concluded that the modification of the law of gravity with nonlinear terms, allows to model the dynamics of the Universe on a large scale and include non-locality without dark matter. (See Falcon et al. 2014, International Journal of Astronomy and Astrophysics, 4, 551-559).

Application of Nonlinear Systems Inverses to Automatic Flight Control Design: System Concepts and Flight Evaluations

NASA Technical Reports Server (NTRS)

Meyer, G.; Cicolani, L.

1981-01-01

A practical method for the design of automatic flight control systems for aircraft with complex characteristics and operational requirements, such as the powered lift STOL and V/STOL configurations, is presented. The method is effective for a large class of dynamic systems requiring multi-axis control which have highly coupled nonlinearities, redundant controls, and complex multidimensional operational envelopes. It exploits the concept of inverse dynamic systems, and an algorithm for the construction of inverse is given. A hierarchic structure for the total control logic with inverses is presented. The method is illustrated with an application to the Augmentor Wing Jet STOL Research Aircraft equipped with a digital flight control system. Results of flight evaluation of the control concept on this aircraft are presented.

The experimental identification of magnetorheological dampers and evaluation of their controllers

NASA Astrophysics Data System (ADS)

Metered, H.; Bonello, P.; Oyadiji, S. O.

2010-05-01

Magnetorheological (MR) fluid dampers are semi-active control devices that have been applied over a wide range of practical vibration control applications. This paper concerns the experimental identification of the dynamic behaviour of an MR damper and the use of the identified parameters in the control of such a damper. Feed-forward and recurrent neural networks are used to model both the direct and inverse dynamics of the damper. Training and validation of the proposed neural networks are achieved by using the data generated through dynamic tests with the damper mounted on a tensile testing machine. The validation test results clearly show that the proposed neural networks can reliably represent both the direct and inverse dynamic behaviours of an MR damper. The effect of the cylinder's surface temperature on both the direct and inverse dynamics of the damper is studied, and the neural network model is shown to be reasonably robust against significant temperature variation. The inverse recurrent neural network model is introduced as a damper controller and experimentally evaluated against alternative controllers proposed in the literature. The results reveal that the neural-based damper controller offers superior damper control. This observation and the added advantages of low-power requirement, extended service life of the damper and the minimal use of sensors, indicate that a neural-based damper controller potentially offers the most cost-effective vibration control solution among the controllers investigated.

Tackling missing radiographic progression data: multiple imputation technique compared with inverse probability weights and complete case analysis.

PubMed

Descalzo, Miguel Á; Garcia, Virginia Villaverde; González-Alvaro, Isidoro; Carbonell, Jordi; Balsa, Alejandro; Sanmartí, Raimon; Lisbona, Pilar; Hernandez-Barrera, Valentín; Jiménez-Garcia, Rodrigo; Carmona, Loreto

2013-02-01

To describe the results of different statistical ways of addressing radiographic outcome affected by missing data--multiple imputation technique, inverse probability weights and complete case analysis--using data from an observational study. A random sample of 96 RA patients was selected for a follow-up study in which radiographs of hands and feet were scored. Radiographic progression was tested by comparing the change in the total Sharp-van der Heijde radiographic score (TSS) and the joint erosion score (JES) from baseline to the end of the second year of follow-up. MI technique, inverse probability weights in weighted estimating equation (WEE) and CC analysis were used to fit a negative binomial regression. Major predictors of radiographic progression were JES and joint space narrowing (JSN) at baseline, together with baseline disease activity measured by DAS28 for TSS and MTX use for JES. Results from CC analysis show larger coefficients and s.e.s compared with MI and weighted techniques. The results from the WEE model were quite in line with those of MI. If it seems plausible that CC or MI analysis may be valid, then MI should be preferred because of its greater efficiency. CC analysis resulted in inefficient estimates or, translated into non-statistical terminology, could guide us into inaccurate results and unwise conclusions. The methods discussed here will contribute to the use of alternative approaches for tackling missing data in observational studies.

Integration of Gravitational Torques in Cerebellar Pathways Allows for the Dynamic Inverse Computation of Vertical Pointing Movements of a Robot Arm

PubMed Central

Gentili, Rodolphe J.; Papaxanthis, Charalambos; Ebadzadeh, Mehdi; Eskiizmirliler, Selim; Ouanezar, Sofiane; Darlot, Christian

2009-01-01

Background Several authors suggested that gravitational forces are centrally represented in the brain for planning, control and sensorimotor predictions of movements. Furthermore, some studies proposed that the cerebellum computes the inverse dynamics (internal inverse model) whereas others suggested that it computes sensorimotor predictions (internal forward model). Methodology/Principal Findings This study proposes a model of cerebellar pathways deduced from both biological and physical constraints. The model learns the dynamic inverse computation of the effect of gravitational torques from its sensorimotor predictions without calculating an explicit inverse computation. By using supervised learning, this model learns to control an anthropomorphic robot arm actuated by two antagonists McKibben artificial muscles. This was achieved by using internal parallel feedback loops containing neural networks which anticipate the sensorimotor consequences of the neural commands. The artificial neural networks architecture was similar to the large-scale connectivity of the cerebellar cortex. Movements in the sagittal plane were performed during three sessions combining different initial positions, amplitudes and directions of movements to vary the effects of the gravitational torques applied to the robotic arm. The results show that this model acquired an internal representation of the gravitational effects during vertical arm pointing movements. Conclusions/Significance This is consistent with the proposal that the cerebellar cortex contains an internal representation of gravitational torques which is encoded through a learning process. Furthermore, this model suggests that the cerebellum performs the inverse dynamics computation based on sensorimotor predictions. This highlights the importance of sensorimotor predictions of gravitational torques acting on upper limb movements performed in the gravitational field. PMID:19384420

In-Flight Suppression of a Destabilized F/A-18 Structural Mode Using the Space Launch System Adaptive Augmenting Control System

NASA Technical Reports Server (NTRS)

Wall, John H.; VanZwieten, Tannen S.; Gilligan, Eric T.; Miller, Christopher J.; Hanson, Curtis E.; Orr, Jeb S.

2015-01-01

NASA's Space Launch System (SLS) Flight Control System (FCS) includes an Adaptive Augmenting Control (AAC) component which employs a multiplicative gain update law to enhance the performance and robustness of the baseline control system for extreme off nominal scenarios. The SLS FCS algorithm including AAC has been flight tested utilizing a specially outfitted F/A-18 fighter jet in which the pitch axis control of the aircraft was performed by a Non-linear Dynamic Inversion (NDI) controller, SLS reference models, and the SLS flight software prototype. This paper describes test cases from the research flight campaign in which the fundamental F/A-18 airframe structural mode was identified using frequency-domain reconstruction of flight data, amplified to result in closed loop instability, and suppressed in-flight by the SLS adaptive control system.

Instantaneous stroke volume in man during lower body negative pressure /LBNP/

NASA Technical Reports Server (NTRS)

Loeppky, J. A.; Richards, K. L.; Greene, E. R.; Eldridge, M. W.; Hoekenga, D. E.; Venters, M. D.; Luft, U. C.

1982-01-01

Results of an examination of the instantaneous time course of the stroke volume (SV) and cardiac output (Q) in response to the onset and release of -50 torr lower body negative pressure (LBNP) are reported. Six male subjects were sealed into a LBNP box up to the iliac crest while being monitored by echocardiograph for centerlamina blood velocity, fluid displacement, stroke volume, heart rate, and leg volume. Particular use was made of pulsed ultrasonic Doppler velocity meters for measuring the blood velocities and flow dynamics. Measurements were made of the subjects continuously beginning from 20 sec prior to and one min after LBNP onset and release. A linear fall in the SV was observed with LBNP at 49% of the baseline value after 33 sec. A 62% drop, the lowest, was detected after 8 min of LBNP. The leg volume was inversely related to Q for the duration of the experiment.

Dynamics and Novel Mechanisms of SN2 Reactions on ab Initio Analytical Potential Energy Surfaces.

PubMed

Szabó, István; Czakó, Gábor

2017-11-30

We describe a novel theoretical approach to the bimolecular nucleophilic substitution (S N 2) reactions that is based on analytical potential energy surfaces (PESs) obtained by fitting a few tens of thousands high-level ab initio energy points. These PESs allow computing millions of quasi-classical trajectories thereby providing unprecedented statistical accuracy for S N 2 reactions, as well as performing high-dimensional quantum dynamics computations. We developed full-dimensional ab initio PESs for the F - + CH 3 Y [Y = F, Cl, I] systems, which describe the direct and indirect, complex-forming Walden-inversion, the frontside attack, and the new double-inversion pathways as well as the proton-transfer channels. Reaction dynamics simulations on the new PESs revealed (a) a novel double-inversion S N 2 mechanism, (b) frontside complex formation, (c) the dynamics of proton transfer, (d) vibrational and rotational mode specificity, (e) mode-specific product vibrational distributions, (f) agreement between classical and quantum dynamics, (g) good agreement with measured scattering angle and product internal energy distributions, and (h) significant leaving group effect in accord with experiments.

Plasma lipidomic profiles and cardiovascular events in a randomized intervention trial with the Mediterranean diet.

PubMed

Toledo, Estefanía; Wang, Dong D; Ruiz-Canela, Miguel; Clish, Clary B; Razquin, Cristina; Zheng, Yan; Guasch-Ferré, Marta; Hruby, Adela; Corella, Dolores; Gómez-Gracia, Enrique; Fiol, Miquel; Estruch, Ramón; Ros, Emilio; Lapetra, José; Fito, Montserrat; Aros, Fernando; Serra-Majem, Luis; Liang, Liming; Salas-Salvadó, Jordi; Hu, Frank B; Martínez-González, Miguel A

2017-10-01

Background: Lipid metabolites may partially explain the inverse association between the Mediterranean diet (MedDiet) and cardiovascular disease (CVD). Objective: We evaluated the associations between 1 ) lipid species and the risk of CVD (myocardial infarction, stroke, or cardiovascular death); 2 ) a MedDiet intervention [supplemented with extra virgin olive oil (EVOO) or nuts] and 1-y changes in these molecules; and 3 ) 1-y changes in lipid species and subsequent CVD. Design: With the use of a case-cohort design, we profiled 202 lipid species at baseline and after 1 y of intervention in the PREDIMED (PREvención con DIeta MEDiterránea) trial in 983 participants [230 cases and a random subcohort of 790 participants (37 overlapping cases)]. Results: Baseline concentrations of cholesterol esters (CEs) were inversely associated with CVD. A shorter chain length and higher saturation of some lipids were directly associated with CVD. After adjusting for multiple testing, direct associations remained significant for 20 lipids, and inverse associations remained significant for 6 lipids. When lipid species were weighted by the number of carbon atoms and double bonds, the strongest inverse association was found for CEs [HR: 0.39 (95% CI: 0.22, 0.68)] between extreme quintiles ( P -trend = 0.002). Participants in the MedDiet + EVOO and MedDiet + nut groups experienced significant ( P < 0.05) 1-y changes in 20 and 17 lipids, respectively, compared with the control group. Of these changes, only those in CE(20:3) in the MedDiet + nuts group remained significant after correcting for multiple testing. None of the 1-y changes was significantly associated with CVD risk after correcting for multiple comparisons. Conclusions: Although the MedDiet interventions induced some significant 1-y changes in the lipidome, they were not significantly associated with subsequent CVD risk. Lipid metabolites with a longer acyl chain and higher number of double bonds at baseline were significantly and inversely associated with the risk of CVD. © 2017 American Society for Nutrition.

The Self-Organization of a Spoken Word

PubMed Central

Holden, John G.; Rajaraman, Srinivasan

2012-01-01

Pronunciation time probability density and hazard functions from large speeded word naming data sets were assessed for empirical patterns consistent with multiplicative and reciprocal feedback dynamics – interaction dominant dynamics. Lognormal and inverse power law distributions are associated with multiplicative and interdependent dynamics in many natural systems. Mixtures of lognormal and inverse power law distributions offered better descriptions of the participant’s distributions than the ex-Gaussian or ex-Wald – alternatives corresponding to additive, superposed, component processes. The evidence for interaction dominant dynamics suggests fundamental links between the observed coordinative synergies that support speech production and the shapes of pronunciation time distributions. PMID:22783213

Inverse Tone Mapping Based upon Retina Response

PubMed Central

Huo, Yongqing; Yang, Fan; Brost, Vincent

2014-01-01

The development of high dynamic range (HDR) display arouses the research of inverse tone mapping methods, which expand dynamic range of the low dynamic range (LDR) image to match that of HDR monitor. This paper proposed a novel physiological approach, which could avoid artifacts occurred in most existing algorithms. Inspired by the property of the human visual system (HVS), this dynamic range expansion scheme performs with a low computational complexity and a limited number of parameters and obtains high-quality HDR results. Comparisons with three recent algorithms in the literature also show that the proposed method reveals more important image details and produces less contrast loss and distortion. PMID:24744678

Inverse algorithms for 2D shallow water equations in presence of wet dry fronts: Application to flood plain dynamics

NASA Astrophysics Data System (ADS)

Monnier, J.; Couderc, F.; Dartus, D.; Larnier, K.; Madec, R.; Vila, J.-P.

2016-11-01

The 2D shallow water equations adequately model some geophysical flows with wet-dry fronts (e.g. flood plain or tidal flows); nevertheless deriving accurate, robust and conservative numerical schemes for dynamic wet-dry fronts over complex topographies remains a challenge. Furthermore for these flows, data are generally complex, multi-scale and uncertain. Robust variational inverse algorithms, providing sensitivity maps and data assimilation processes may contribute to breakthrough shallow wet-dry front dynamics modelling. The present study aims at deriving an accurate, positive and stable finite volume scheme in presence of dynamic wet-dry fronts, and some corresponding inverse computational algorithms (variational approach). The schemes and algorithms are assessed on classical and original benchmarks plus a real flood plain test case (Lèze river, France). Original sensitivity maps with respect to the (friction, topography) pair are performed and discussed. The identification of inflow discharges (time series) or friction coefficients (spatially distributed parameters) demonstrate the algorithms efficiency.

X-38 Experimental Controls Laws

NASA Technical Reports Server (NTRS)

Munday, Steve; Estes, Jay; Bordano, Aldo J.

2000-01-01

X-38 Experimental Control Laws X-38 is a NASA JSC/DFRC experimental flight test program developing a series of prototypes for an International Space Station (ISS) Crew Return Vehicle, often called an ISS "lifeboat." X- 38 Vehicle 132 Free Flight 3, currently scheduled for the end of this month, will be the first flight test of a modem FCS architecture called Multi-Application Control-Honeywell (MACH), originally developed by the Honeywell Technology Center. MACH wraps classical P&I outer attitude loops around a modem dynamic inversion attitude rate loop. The dynamic inversion process requires that the flight computer have an onboard aircraft model of expected vehicle dynamics based upon the aerodynamic database. Dynamic inversion is computationally intensive, so some timing modifications were made to implement MACH on the slower flight computers of the subsonic test vehicles. In addition to linear stability margin analyses and high fidelity 6-DOF simulation, hardware-in-the-loop testing is used to verify the implementation of MACH and its robustness to aerodynamic and environmental uncertainties and disturbances.

Angular dependence of multiangle dynamic light scattering for particle size distribution inversion using a self-adapting regularization algorithm

NASA Astrophysics Data System (ADS)

Li, Lei; Yu, Long; Yang, Kecheng; Li, Wei; Li, Kai; Xia, Min

2018-04-01

The multiangle dynamic light scattering (MDLS) technique can better estimate particle size distributions (PSDs) than single-angle dynamic light scattering. However, determining the inversion range, angular weighting coefficients, and scattering angle combination is difficult but fundamental to the reconstruction for both unimodal and multimodal distributions. In this paper, we propose a self-adapting regularization method called the wavelet iterative recursion nonnegative Tikhonov-Phillips-Twomey (WIRNNT-PT) algorithm. This algorithm combines a wavelet multiscale strategy with an appropriate inversion method and could self-adaptively optimize several noteworthy issues containing the choices of the weighting coefficients, the inversion range and the optimal inversion method from two regularization algorithms for estimating the PSD from MDLS measurements. In addition, the angular dependence of the MDLS for estimating the PSDs of polymeric latexes is thoroughly analyzed. The dependence of the results on the number and range of measurement angles was analyzed in depth to identify the optimal scattering angle combination. Numerical simulations and experimental results for unimodal and multimodal distributions are presented to demonstrate both the validity of the WIRNNT-PT algorithm and the angular dependence of MDLS and show that the proposed algorithm with a six-angle analysis in the 30-130° range can be satisfactorily applied to retrieve PSDs from MDLS measurements.

Inverse Symmetry in Complete Genomes and Whole-Genome Inverse Duplication

PubMed Central

Kong, Sing-Guan; Fan, Wen-Lang; Chen, Hong-Da; Hsu, Zi-Ting; Zhou, Nengji; Zheng, Bo; Lee, Hoong-Chien

2009-01-01

The cause of symmetry is usually subtle, and its study often leads to a deeper understanding of the bearer of the symmetry. To gain insight into the dynamics driving the growth and evolution of genomes, we conducted a comprehensive study of textual symmetries in 786 complete chromosomes. We focused on symmetry based on our belief that, in spite of their extreme diversity, genomes must share common dynamical principles and mechanisms that drive their growth and evolution, and that the most robust footprints of such dynamics are symmetry related. We found that while complement and reverse symmetries are essentially absent in genomic sequences, inverse–complement plus reverse–symmetry is prevalent in complex patterns in most chromosomes, a vast majority of which have near maximum global inverse symmetry. We also discovered relations that can quantitatively account for the long observed but unexplained phenomenon of -mer skews in genomes. Our results suggest segmental and whole-genome inverse duplications are important mechanisms in genome growth and evolution, probably because they are efficient means by which the genome can exploit its double-stranded structure to enrich its code-inventory. PMID:19898631

Modeling and control of magnetorheological fluid dampers using neural networks

NASA Astrophysics Data System (ADS)

Wang, D. H.; Liao, W. H.

2005-02-01

Due to the inherent nonlinear nature of magnetorheological (MR) fluid dampers, one of the challenging aspects for utilizing these devices to achieve high system performance is the development of accurate models and control algorithms that can take advantage of their unique characteristics. In this paper, the direct identification and inverse dynamic modeling for MR fluid dampers using feedforward and recurrent neural networks are studied. The trained direct identification neural network model can be used to predict the damping force of the MR fluid damper on line, on the basis of the dynamic responses across the MR fluid damper and the command voltage, and the inverse dynamic neural network model can be used to generate the command voltage according to the desired damping force through supervised learning. The architectures and the learning methods of the dynamic neural network models and inverse neural network models for MR fluid dampers are presented, and some simulation results are discussed. Finally, the trained neural network models are applied to predict and control the damping force of the MR fluid damper. Moreover, validation methods for the neural network models developed are proposed and used to evaluate their performance. Validation results with different data sets indicate that the proposed direct identification dynamic model using the recurrent neural network can be used to predict the damping force accurately and the inverse identification dynamic model using the recurrent neural network can act as a damper controller to generate the command voltage when the MR fluid damper is used in a semi-active mode.

Relation between wall shear stress and carotid artery wall thickening MRI versus CFD.

PubMed

Cibis, Merih; Potters, Wouter V; Selwaness, Mariana; Gijsen, Frank J; Franco, Oscar H; Arias Lorza, Andres M; de Bruijne, Marleen; Hofman, Albert; van der Lugt, Aad; Nederveen, Aart J; Wentzel, Jolanda J

2016-03-21

Wall shear stress (WSS), a parameter associated with endothelial function, is calculated by computational fluid dynamics (CFD) or phase-contrast (PC) MRI measurements. Although CFD is common in WSS (WSSCFD) calculations, PC-MRI-based WSS (WSSMRI) is more favorable in population studies; since it is straightforward and less time consuming. However, it is not clear if WSSMRI and WSSCFD show similar associations with vascular pathology. Our aim was to test the associations between wall thickness (WT) of the carotid arteries and WSSMRI and WSSCFD. The subjects (n=14) with an asymptomatic carotid plaque who underwent MRI scans two times within 4 years of time were selected from the Rotterdam Study. We compared WSSCFD and WSSMRI at baseline and follow-up. Baseline WSSMRI and WSSCFD values were divided into 3 categories representing low, medium and high WSS tertiles. WT of each tertile was compared by a one-way ANOVA test. The WSSMRI and WSSCFD were 0.50±0.13Pa and 0.73±0.25Pa at baseline. Although WSSMRI was underestimated, a significant regression was found between WSSMRI and WSSCFD (r(2)=0.71). No significant difference was found between baseline and follow-up WSS by CFD and MRI-based calculations. The WT at baseline was 1.36±0.16mm and did not change over time. The WT was 1.55±0.21mm in low, 1.33±0.20mm in medium and 1.21±0.21mm in the high WSSMRI tertiles. Similarly, the WT was 1.49±0.21mm in low, 1.33±0.20mm in medium and 1.26±0.21mm in high WSSCFD tertiles. We found that WSSMRI and WSSCFD were inversely related with WT. WSSMRI and WSSCFD patterns were similar although MRI-based calculations underestimated WSS. Copyright © 2016 Elsevier Ltd. All rights reserved.

Endogenous Androgens and Sex Hormone-Binding Globulin in Women and Risk of Metabolic Syndrome and Type 2 Diabetes.

PubMed

Fenske, Benjamin; Kische, Hanna; Gross, Stefan; Wallaschofski, Henri; Völzke, Henry; Dörr, Marcus; Nauck, Matthias; Keevil, Brian G; Brabant, Georg; Haring, Robin

2015-12-01

The association of endogenous androgens and sex hormone-binding globulin (SHBG) with metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM) mostly 23562 refers to small and selected study samples with immunoassay-based measurements. Thus, we investigated the association of hormone levels with MetS and T2DM in women from a large population-based sample. A total of 2077 women from the Study of Health in Pomerania were assessed at baseline (N = 3160, 1997-2001) and 5-year follow-up (N = 1711, 2002-2006). We investigated associations of total testosterone (T) and androstenedione measured by liquid chromatography-tandem mass spectrometry, SHBG by immunoassay, and free T and free androgen index with MetS and T2DM. Baseline prevalence of MetS and T2DM was 23.1% (N = 365) and 9.5% (N = 196), with an incidence of 17.7 and 7.0 per 1.000 person-years, respectively. Cross-sectional analyses yielded inverse associations of SHBG with MetS (relative risk [RR], 0.67; 95% confidence interval [CI], 0.60-0.74) and T2DM (RR, 0.61; 95% CI, 0.50-0.74) after multivariable adjustment. In longitudinal analyses, only age-adjusted models showed an inverse association of baseline SHBG with incident MetS (RR, 0.61; 95% CI, 0.51-0.73) and T2DM (RR, 0.58; 95% CI, 0.43-0.78). Multivariable-adjusted models stratified by menopausal status revealed an inverse association between SHBG and incident MetS risk in postmenopausal women (RR, 0.65; 95% CI, 0.51-0.81). This longitudinal population-based study revealed independent inverse associations of SHBG with MetS and T2DM, suggesting low SHBG as a potential risk marker for cardiometabolic morbidity, especially among postmenopausal women.

Targeted Maximum Likelihood Estimation for Dynamic and Static Longitudinal Marginal Structural Working Models

PubMed Central

Schwab, Joshua; Gruber, Susan; Blaser, Nello; Schomaker, Michael; van der Laan, Mark

2015-01-01

This paper describes a targeted maximum likelihood estimator (TMLE) for the parameters of longitudinal static and dynamic marginal structural models. We consider a longitudinal data structure consisting of baseline covariates, time-dependent intervention nodes, intermediate time-dependent covariates, and a possibly time-dependent outcome. The intervention nodes at each time point can include a binary treatment as well as a right-censoring indicator. Given a class of dynamic or static interventions, a marginal structural model is used to model the mean of the intervention-specific counterfactual outcome as a function of the intervention, time point, and possibly a subset of baseline covariates. Because the true shape of this function is rarely known, the marginal structural model is used as a working model. The causal quantity of interest is defined as the projection of the true function onto this working model. Iterated conditional expectation double robust estimators for marginal structural model parameters were previously proposed by Robins (2000, 2002) and Bang and Robins (2005). Here we build on this work and present a pooled TMLE for the parameters of marginal structural working models. We compare this pooled estimator to a stratified TMLE (Schnitzer et al. 2014) that is based on estimating the intervention-specific mean separately for each intervention of interest. The performance of the pooled TMLE is compared to the performance of the stratified TMLE and the performance of inverse probability weighted (IPW) estimators using simulations. Concepts are illustrated using an example in which the aim is to estimate the causal effect of delayed switch following immunological failure of first line antiretroviral therapy among HIV-infected patients. Data from the International Epidemiological Databases to Evaluate AIDS, Southern Africa are analyzed to investigate this question using both TML and IPW estimators. Our results demonstrate practical advantages of the pooled TMLE over an IPW estimator for working marginal structural models for survival, as well as cases in which the pooled TMLE is superior to its stratified counterpart. PMID:25909047

Recursive flexible multibody system dynamics using spatial operators

NASA Technical Reports Server (NTRS)

Jain, A.; Rodriguez, G.

1992-01-01

This paper uses spatial operators to develop new spatially recursive dynamics algorithms for flexible multibody systems. The operator description of the dynamics is identical to that for rigid multibody systems. Assumed-mode models are used for the deformation of each individual body. The algorithms are based on two spatial operator factorizations of the system mass matrix. The first (Newton-Euler) factorization of the mass matrix leads to recursive algorithms for the inverse dynamics, mass matrix evaluation, and composite-body forward dynamics for the systems. The second (innovations) factorization of the mass matrix, leads to an operator expression for the mass matrix inverse and to a recursive articulated-body forward dynamics algorithm. The primary focus is on serial chains, but extensions to general topologies are also described. A comparison of computational costs shows that the articulated-body, forward dynamics algorithm is much more efficient than the composite-body algorithm for most flexible multibody systems.

GARCH modelling of covariance in dynamical estimation of inverse solutions

NASA Astrophysics Data System (ADS)

Galka, Andreas; Yamashita, Okito; Ozaki, Tohru

2004-12-01

The problem of estimating unobserved states of spatially extended dynamical systems poses an inverse problem, which can be solved approximately by a recently developed variant of Kalman filtering; in order to provide the model of the dynamics with more flexibility with respect to space and time, we suggest to combine the concept of GARCH modelling of covariance, well known in econometrics, with Kalman filtering. We formulate this algorithm for spatiotemporal systems governed by stochastic diffusion equations and demonstrate its feasibility by presenting a numerical simulation designed to imitate the situation of the generation of electroencephalographic recordings by the human cortex.

Force and Moment Approach for Achievable Dynamics Using Nonlinear Dynamic Inversion

NASA Technical Reports Server (NTRS)

Ostroff, Aaron J.; Bacon, Barton J.

1999-01-01

This paper describes a general form of nonlinear dynamic inversion control for use in a generic nonlinear simulation to evaluate candidate augmented aircraft dynamics. The implementation is specifically tailored to the task of quickly assessing an aircraft's control power requirements and defining the achievable dynamic set. The achievable set is evaluated while undergoing complex mission maneuvers, and perfect tracking will be accomplished when the desired dynamics are achievable. Variables are extracted directly from the simulation model each iteration, so robustness is not an issue. Included in this paper is a description of the implementation of the forces and moments from simulation variables, the calculation of control effectiveness coefficients, methods for implementing different types of aerodynamic and thrust vectoring controls, adjustments for control effector failures, and the allocation approach used. A few examples illustrate the perfect tracking results obtained.

Associations between adiposity, hormones, and gains in height, whole-body height-adjusted bone size, and size-adjusted bone mineral content in 8- to 11-year-old children.

PubMed

Dalskov, S; Ritz, C; Larnkjær, A; Damsgaard, C T; Petersen, R A; Sørensen, L B; Ong, K K; Astrup, A; Michaelsen, K F; Mølgaard, C

2016-04-01

We examined fat-independent associations of hormones with height and whole-body bone size and mineral content in 633 school children. IGF-1 and osteocalcin predict growth in height, while fat, osteocalcin, and in girls also, IGF-1 predict growth in bone size. Leptin and ghrelin are inversely associated with bone size in girls. Obesity causes larger bone size and bone mass, but the role of hormones in this up-regulation of bone in obesity is not well elucidated. We examined longitudinal associations between baseline body fat mass (FM), and fat-independent fasting levels of ghrelin, adiponectin, leptin, insulin, insulin-like growth factor-I (IGF-1), osteocalcin, and intact parathyroid hormone, and subsequent changes in height and in whole-body height-adjusted bone area "BAheight" and size-adjusted bone mineral content "BMCsize" in 8- to 11-year-olds. Analyses were carried out separately for boys (n = 325) and girls (n = 308) including data from baseline, 3 and 6 months from OPUS School Meal Study. In both sexes: gain in BAheight was positively associated with baseline FM (≥2.05 cm(2)/kg, both p ≤ 0.003). Furthermore, gain in height was positively associated with baseline IGF-1 (≥0.02 cm/ng/ml, p = 0.001) and osteocalcin (≥0.13 cm/ng/ml, p ≤ 0.009); and gain in BAheight was positively associated with baseline osteocalcin (≥0.35 cm(2)/ng/ml, p ≤ 0.019). In girls only, gain in BAheight was also positively associated with baseline IGF-1 (0.06 cm(2)/ng/ml, p = 0.017) and inversely associated with both baseline ghrelin (-0.01 cm(2)/pg/ml, p = 0.001) and leptin (-1.21 cm(2)/μg/ml, p = 0.005). In boys, gain in BMCsize was positively associated with osteocalcin (0.18 g/ng/ml, p = 0.030). This large longitudinal study suggests that in 8- to 11-year-old children, IGF-1 and osteocalcin predict growth in height, while FM, osteocalcin, and in girls also, IGF-1 predict growth in BAheight. Fat-independent inverse associations of leptin and ghrelin with BAheight in girls' are contrary to proposed growth-stimulating effects of leptin. Osteocalcin in boys predicts gain in BMCsize.

Real-time inverse kinematics and inverse dynamics for lower limb applications using OpenSim

PubMed Central

Modenese, L.; Lloyd, D.G.

2017-01-01

Real-time estimation of joint angles and moments can be used for rapid evaluation in clinical, sport, and rehabilitation contexts. However, real-time calculation of kinematics and kinetics is currently based on approximate solutions or generic anatomical models. We present a real-time system based on OpenSim solving inverse kinematics and dynamics without simplifications at 2000 frame per seconds with less than 31.5ms of delay. We describe the software architecture, sensitivity analyses to minimise delays and errors, and compare offline and real-time results. This system has the potential to strongly impact current rehabilitation practices enabling the use of personalised musculoskeletal models in real-time. PMID:27723992

Real-time inverse kinematics and inverse dynamics for lower limb applications using OpenSim.

PubMed

Pizzolato, C; Reggiani, M; Modenese, L; Lloyd, D G

2017-03-01

Real-time estimation of joint angles and moments can be used for rapid evaluation in clinical, sport, and rehabilitation contexts. However, real-time calculation of kinematics and kinetics is currently based on approximate solutions or generic anatomical models. We present a real-time system based on OpenSim solving inverse kinematics and dynamics without simplifications at 2000 frame per seconds with less than 31.5 ms of delay. We describe the software architecture, sensitivity analyses to minimise delays and errors, and compare offline and real-time results. This system has the potential to strongly impact current rehabilitation practices enabling the use of personalised musculoskeletal models in real-time.

Inverse problems in the modeling of vibrations of flexible beams

NASA Technical Reports Server (NTRS)

Banks, H. T.; Powers, R. K.; Rosen, I. G.

1987-01-01

The formulation and solution of inverse problems for the estimation of parameters which describe damping and other dynamic properties in distributed models for the vibration of flexible structures is considered. Motivated by a slewing beam experiment, the identification of a nonlinear velocity dependent term which models air drag damping in the Euler-Bernoulli equation is investigated. Galerkin techniques are used to generate finite dimensional approximations. Convergence estimates and numerical results are given. The modeling of, and related inverse problems for the dynamics of a high pressure hose line feeding a gas thruster actuator at the tip of a cantilevered beam are then considered. Approximation and convergence are discussed and numerical results involving experimental data are presented.

Upper limb joint forces and moments during underwater cyclical movements.

PubMed

Lauer, Jessy; Rouard, Annie Hélène; Vilas-Boas, João Paulo

2016-10-03

Sound inverse dynamics modeling is lacking in aquatic locomotion research because of the difficulty in measuring hydrodynamic forces in dynamic conditions. Here we report the successful implementation and validation of an innovative methodology crossing new computational fluid dynamics and inverse dynamics techniques to quantify upper limb joint forces and moments while moving in water. Upper limb kinematics of seven male swimmers sculling while ballasted with 4kg was recorded through underwater motion capture. Together with body scans, segment inertial properties, and hydrodynamic resistances computed from a unique dynamic mesh algorithm capable to handle large body deformations, these data were fed into an inverse dynamics model to solve for joint kinetics. Simulation validity was assessed by comparing the impulse produced by the arms, calculated by integrating vertical forces over a stroke period, to the net theoretical impulse of buoyancy and ballast forces. A resulting gap of 1.2±3.5% provided confidence in the results. Upper limb joint load was within 5% of swimmer׳s body weight, which tends to supports the use of low-load aquatic exercises to reduce joint stress. We expect this significant methodological improvement to pave the way towards deeper insights into the mechanics of aquatic movement and the establishment of practice guidelines in rehabilitation, fitness or swimming performance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nonlinear Stimulated Raman Exact Passage by Resonance-Locked Inverse Engineering

NASA Astrophysics Data System (ADS)

Dorier, V.; Gevorgyan, M.; Ishkhanyan, A.; Leroy, C.; Jauslin, H. R.; Guérin, S.

2017-12-01

We derive an exact and robust stimulated Raman process for nonlinear quantum systems driven by pulsed external fields. The external fields are designed with closed-form expressions from the inverse engineering of a given efficient and stable dynamics. This technique allows one to induce a controlled population inversion which surpasses the usual nonlinear stimulated Raman adiabatic passage efficiency.

The First Time Ever I Saw Your Feet: Inversion Effect in Newborns' Sensitivity to Biological Motion

ERIC Educational Resources Information Center

Bardi, Lara; Regolin, Lucia; Simion, Francesca

2014-01-01

Inversion effect in biological motion perception has been recently attributed to an innate sensitivity of the visual system to the gravity-dependent dynamic of the motion. However, the specific cues that determine the inversion effect in naïve subjects were never investigated. In the present study, we have assessed the contribution of the local…

Guidance of Nonlinear Nonminimum-Phase Dynamic Systems

NASA Technical Reports Server (NTRS)

Devasia, Santosh

1996-01-01

The research work has advanced the inversion-based guidance theory for: systems with non-hyperbolic internal dynamics; systems with parameter jumps; and systems where a redesign of the output trajectory is desired. A technique to achieve output tracking for nonminimum phase linear systems with non-hyperbolic and near non-hyperbolic internal dynamics was developed. This approach integrated stable inversion techniques, that achieve exact-tracking, with approximation techniques, that modify the internal dynamics to achieve desirable performance. Such modification of the internal dynamics was used (a) to remove non-hyperbolicity which is an obstruction to applying stable inversion techniques and (b) to reduce large preactuation times needed to apply stable inversion for near non-hyperbolic cases. The method was applied to an example helicopter hover control problem with near non-hyperbolic internal dynamics for illustrating the trade-off between exact tracking and reduction of preactuation time. Future work will extend these results to guidance of nonlinear non-hyperbolic systems. The exact output tracking problem for systems with parameter jumps was considered. Necessary and sufficient conditions were derived for the elimination of switching-introduced output transient. While previous works had studied this problem by developing a regulator that maintains exact tracking through parameter jumps (switches), such techniques are, however, only applicable to minimum-phase systems. In contrast, our approach is also applicable to nonminimum-phase systems and leads to bounded but possibly non-causal solutions. In addition, for the case when the reference trajectories are generated by an exosystem, we developed an exact-tracking controller which could be written in a feedback form. As in standard regulator theory, we also obtained a linear map from the states of the exosystem to the desired system state, which was defined via a matrix differential equation.

Gravity Wave Dynamics in a Mesospheric Inversion Layer: 1. Reflection, Trapping, and Instability Dynamics

PubMed Central

Laughman, Brian; Wang, Ling; Lund, Thomas S.; Collins, Richard L.

2018-01-01

Abstract An anelastic numerical model is employed to explore the dynamics of gravity waves (GWs) encountering a mesosphere inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. Instabilities occur within the MIL when the GW amplitude approaches that required for GW breaking due to compression of the vertical wavelength accompanying the increasing static stability. Thus, MILs can cause large‐amplitude GWs to yield instabilities and turbulence below the altitude where they would otherwise arise. Smaller‐amplitude GWs encountering a MIL do not lead to instability and turbulence but do exhibit partial reflection and transmission, and the transmission is a smaller fraction of the incident GW when instabilities and turbulence arise within the MIL. Additionally, greater GW transmission occurs for weaker MILs and for GWs having larger vertical wavelengths relative to the MIL depth and for lower GW intrinsic frequencies. These results imply similar dynamics for inversions due to other sources, including the tropopause inversion layer, the high stability capping the polar summer mesopause, and lower frequency GWs or tides having sufficient amplitudes to yield significant variations in stability at large and small vertical scales. MILs also imply much stronger reflections and less coherent GW propagation in environments having significant fine structure in the stability and velocity fields than in environments that are smoothly varying. PMID:29576994

Gravity Wave Dynamics in a Mesospheric Inversion Layer: 1. Reflection, Trapping, and Instability Dynamics

NASA Astrophysics Data System (ADS)

Fritts, David C.; Laughman, Brian; Wang, Ling; Lund, Thomas S.; Collins, Richard L.

2018-01-01

An anelastic numerical model is employed to explore the dynamics of gravity waves (GWs) encountering a mesosphere inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. Instabilities occur within the MIL when the GW amplitude approaches that required for GW breaking due to compression of the vertical wavelength accompanying the increasing static stability. Thus, MILs can cause large-amplitude GWs to yield instabilities and turbulence below the altitude where they would otherwise arise. Smaller-amplitude GWs encountering a MIL do not lead to instability and turbulence but do exhibit partial reflection and transmission, and the transmission is a smaller fraction of the incident GW when instabilities and turbulence arise within the MIL. Additionally, greater GW transmission occurs for weaker MILs and for GWs having larger vertical wavelengths relative to the MIL depth and for lower GW intrinsic frequencies. These results imply similar dynamics for inversions due to other sources, including the tropopause inversion layer, the high stability capping the polar summer mesopause, and lower frequency GWs or tides having sufficient amplitudes to yield significant variations in stability at large and small vertical scales. MILs also imply much stronger reflections and less coherent GW propagation in environments having significant fine structure in the stability and velocity fields than in environments that are smoothly varying.

Spin-charge coupled dynamics driven by a time-dependent magnetization

NASA Astrophysics Data System (ADS)

Tölle, Sebastian; Eckern, Ulrich; Gorini, Cosimo

2017-03-01

The spin-charge coupled dynamics in a thin, magnetized metallic system are investigated. The effective driving force acting on the charge carriers is generated by a dynamical magnetic texture, which can be induced, e.g., by a magnetic material in contact with a normal-metal system. We consider a general inversion-asymmetric substrate/normal-metal/magnet structure, which, by specifying the precise nature of each layer, can mimic various experimentally employed setups. Inversion symmetry breaking gives rise to an effective Rashba spin-orbit interaction. We derive general spin-charge kinetic equations which show that such spin-orbit interaction, together with anisotropic Elliott-Yafet spin relaxation, yields significant corrections to the magnetization-induced dynamics. In particular, we present a consistent treatment of the spin density and spin current contributions to the equations of motion, inter alia, identifying a term in the effective force which appears due to a spin current polarized parallel to the magnetization. This "inverse-spin-filter" contribution depends markedly on the parameter which describes the anisotropy in spin relaxation. To further highlight the physical meaning of the different contributions, the spin-pumping configuration of typical experimental setups is analyzed in detail. In the two-dimensional limit the buildup of dc voltage is dominated by the spin-galvanic (inverse Edelstein) effect. A measuring scheme that could isolate this contribution is discussed.

Static and Dynamic Reservoir Characterization Using High Resolution P-Wave Velocity Data in Delhi Field, la

NASA Astrophysics Data System (ADS)

Hussain, S.; Davis, T.

2012-12-01

Static and dynamic reservoir characterization was done on high resolution P-wave seismic data in Delhi Field, LA to study the complex stratigraphy of the Holt-Bryant sands and to delineate the CO2 flow path. The field is undergoing CO2 injection for enhanced oil recovery. The seismic data was bandwidth extended by Geotrace to decrease the tuning thickness effect. Once the authenticity of the added frequencies in the data was determined, the interpretation helped map thin Tuscaloosa and Paluxy sands. Cross-equalization was done on the baseline and monitor surveys to remove the non-repeatable noise in the data. Acoustic impedance (AI) inversion was done on the baseline and monitor surveys to map the changes in AI with CO2 injection in the field. Figure 1 shows the AI percentage change at Base Paluxy. The analysis helped identify areas that were not being swept by CO2. Figure 2 shows the CO2 flow paths in Tuscaloosa formation. The percentage change of AI with CO2 injection and pressure increase corresponded with the fluid substitution modeling results. Time-lapse interpretation helped in delineating the channels, high permeability zones and the bypassed zones in the reservoir.; Figure 1: P-impedance percentage difference map with a 2 ms window centered at the base of Paluxy with the production data from June 2010 overlain; the black dashed line is the oil-water contact; notice the negative impedance change below the OWC. The lighter yellow color shows area where Paluxy is not being swept completely. ; Figure 2: P-impedance percentage difference map at TUSC 7 top; the white triangles are TUSC 7 injectors and the white circles are TUSC 7 producers; the black polygons show the flow paths of CO2.

Pseudo-dynamic source characterization accounting for rough-fault effects

NASA Astrophysics Data System (ADS)

Galis, Martin; Thingbaijam, Kiran K. S.; Mai, P. Martin

2016-04-01

Broadband ground-motion simulations, ideally for frequencies up to ~10Hz or higher, are important for earthquake engineering; for example, seismic hazard analysis for critical facilities. An issue with such simulations is realistic generation of radiated wave-field in the desired frequency range. Numerical simulations of dynamic ruptures propagating on rough faults suggest that fault roughness is necessary for realistic high-frequency radiation. However, simulations of dynamic ruptures are too expensive for routine applications. Therefore, simplified synthetic kinematic models are often used. They are usually based on rigorous statistical analysis of rupture models inferred by inversions of seismic and/or geodetic data. However, due to limited resolution of the inversions, these models are valid only for low-frequency range. In addition to the slip, parameters such as rupture-onset time, rise time and source time functions are needed for complete spatiotemporal characterization of the earthquake rupture. But these parameters are poorly resolved in the source inversions. To obtain a physically consistent quantification of these parameters, we simulate and analyze spontaneous dynamic ruptures on rough faults. First, by analyzing the impact of fault roughness on the rupture and seismic radiation, we develop equivalent planar-fault kinematic analogues of the dynamic ruptures. Next, we investigate the spatial interdependencies between the source parameters to allow consistent modeling that emulates the observed behavior of dynamic ruptures capturing the rough-fault effects. Based on these analyses, we formulate a framework for pseudo-dynamic source model, physically consistent with the dynamic ruptures on rough faults.

Modeling analysis of pulsed magnetization process of magnetic core based on inverse Jiles-Atherton model

NASA Astrophysics Data System (ADS)

Liu, Yi; Zhang, He; Liu, Siwei; Lin, Fuchang

2018-05-01

The J-A (Jiles-Atherton) model is widely used to describe the magnetization characteristics of magnetic cores in a low-frequency alternating field. However, this model is deficient in the quantitative analysis of the eddy current loss and residual loss in a high-frequency magnetic field. Based on the decomposition of magnetization intensity, an inverse J-A model is established which uses magnetic flux density B as an input variable. Static and dynamic core losses under high frequency excitation are separated based on the inverse J-A model. Optimized parameters of the inverse J-A model are obtained based on particle swarm optimization. The platform for the pulsed magnetization characteristic test is designed and constructed. The hysteresis curves of ferrite and Fe-based nanocrystalline cores at high magnetization rates are measured. The simulated and measured hysteresis curves are presented and compared. It is found that the inverse J-A model can be used to describe the magnetization characteristics at high magnetization rates and to separate the static loss and dynamic loss accurately.

The efficacy of vitamin C supplementation on reducing total serum cholesterol in human subjects: a review and analysis of 51 experimental trials

PubMed Central

McRae, Marc P.

2006-01-01

Abstract Objective Observational studies in humans have shown an inverse relationship between plasma vitamin C concentration and total serum cholesterol. However, experimental studies have shown inconsistent results regarding the ability of vitamin C to reduce total serum cholesterol. Methods Published reports of trials studying the effects of vitamin C on serum lipids were identified by a search of Medline from 1966 to 2004. Data from 51 experimental studies comprising of 1666 pooled subjects were selected for analysis. Results A very strong negative association was observed between baseline total serum cholesterol and the percent change in cholesterol (r = −0.585, p<0.001). When subjects were divided into 4 groups based on their baseline total serum cholesterol levels, the following weighted mean percent changes in cholesterol from baseline were observed: normal cholesterol (<199mg/dl): 0.91±6.8% (n=508); borderline high cholesterol (200–239mg/dl): 3.90±5.78% (n=605); high cholesterol (240–279mg/dl): 11.40±7.96% (n=300); severe cholesterol (>280mg/dl): 14.30±8.36% (n=253). A significant inverse relationship was found between the baseline plasma vitamin C concentrations and mean percent change in total cholesterol from baseline (r = −0.500, p<0.005). It was also observed that the high and severe baseline cholesterol groups possessed lower baseline plasma vitamin C concentrations than those in the normal cholesterol groups (0.79 and 0.55 versus 1.24 mg/dl respectively). Conclusion This finding strengthens the hypothesis that the cholesterol lowering and cardio-protective benefit of vitamin C supplementation may be in its ability to elevate plasma vitamin C concentrations in those patients who initially possess lower than normal vitamin C plasma concentrations. PMID:19674666

Biomechanical Comparison of 3 Ankle Braces With and Without Free Rotation in the Sagittal Plane

PubMed Central

Alfuth, Martin; Klein, Dieter; Koch, Raphael; Rosenbaum, Dieter

2014-01-01

Context: Various designs of braces including hinged and nonhinged models are used to provide external support of the ankle. Hinged ankle braces supposedly allow almost free dorsiflexion and plantar flexion of the foot in the sagittal plane. It is unclear, however, whether this additional degree of freedom affects the stabilizing effect of the brace in the other planes of motion. Objective: To investigate the dynamic and passive stabilizing effects of 3 ankle braces, 2 hinged models that provide free plantar flexion–dorsiflexion in the sagittal plane and 1 ankle brace without a hinge. Design: Crossover study. Setting: University Movement Analysis Laboratory. Patients or Other Participants: Seventeen healthy volunteers (5 women, 12 men; age = 25.4 ± 4.8 years; height = 180.3 ± 6.5 cm; body mass = 75.5 ± 10.4 kg). Intervention(s): We dynamically induced foot inversion on a tilting platform and passively induced foot movements in 6 directions via a custom-built apparatus in 3 brace conditions and a control condition (no brace). Main Outcome Measure(s): Maximum inversion was determined dynamically using an in-shoe electrogoniometer. Passively induced maximal joint angles were measured using a torque and angle sensor. We analyzed differences among the 4 ankle-brace conditions (3 braces, 1 control) for each of the dependent variables with Friedman and post hoc tests (P < .05). Results: Each ankle brace restricted dynamic foot-inversion movements on the tilting platform as compared with the control condition, whereas only the 2 hinged ankle braces differed from each other, with greater movement restriction caused by the Ankle X model. Passive foot inversion was reduced with all ankle braces. Passive plantar flexion was greater in the hinged models as compared with the nonhinged brace. Conclusions: All ankle braces showed stabilizing effects against dynamic and passive foot inversion. Differences between the hinged braces and the nonhinged brace did not appear to be clinically relevant. PMID:25098661

Typical use of inverse dynamics in perceiving motion in autistic adults: Exploring computational principles of perception and action.

PubMed

Takamuku, Shinya; Forbes, Paul A G; Hamilton, Antonia F de C; Gomi, Hiroaki

2018-05-07

There is increasing evidence for motor difficulties in many people with autism spectrum condition (ASC). These difficulties could be linked to differences in the use of internal models which represent relations between motions and forces/efforts. The use of these internal models may be dependent on the cerebellum which has been shown to be abnormal in autism. Several studies have examined internal computations of forward dynamics (motion from force information) in autism, but few have tested the inverse dynamics computation, that is, the determination of force-related information from motion information. Here, we examined this ability in autistic adults by measuring two perceptual biases which depend on the inverse computation. First, we asked participants whether they experienced a feeling of resistance when moving a delayed cursor, which corresponds to the inertial force of the cursor implied by its motion-both typical and ASC participants reported similar feelings of resistance. Second, participants completed a psychophysical task in which they judged the velocity of a moving hand with or without a visual cue implying inertial force. Both typical and ASC participants perceived the hand moving with the inertial cue to be slower than the hand without it. In both cases, the magnitude of the effects did not differ between the two groups. Our results suggest that the neural systems engaged in the inverse dynamics computation are preserved in ASC, at least in the observed conditions. Autism Res 2018. © 2018 International Society for Autism Research, Wiley Periodicals, Inc. We tested the ability to estimate force information from motion information, which arises from a specific "inverse dynamics" computation. Autistic adults and a matched control group reported feeling a resistive sensation when moving a delayed cursor and also judged a moving hand to be slower when it was pulling a load. These findings both suggest that the ability to estimate force information from motion information is intact in autism. © 2018 International Society for Autism Research, Wiley Periodicals, Inc.

How much can history constrain adaptive evolution? A real-time evolutionary approach of inversion polymorphisms in Drosophila subobscura.

PubMed

Fragata, I; Lopes-Cunha, M; Bárbaro, M; Kellen, B; Lima, M; Santos, M A; Faria, G S; Santos, M; Matos, M; Simões, P

2014-12-01

Chromosomal inversions are present in a wide range of animals and plants, having an important role in adaptation and speciation. Although empirical evidence of their adaptive value is abundant, the role of different processes underlying evolution of chromosomal polymorphisms is not fully understood. History and selection are likely to shape inversion polymorphism variation to an extent yet largely unknown. Here, we perform a real-time evolution study addressing the role of historical constraints and selection in the evolution of these polymorphisms. We founded laboratory populations of Drosophila subobscura derived from three locations along the European cline and followed the evolutionary dynamics of inversion polymorphisms throughout the first 40 generations. At the beginning, populations were highly differentiated and remained so throughout generations. We report evidence of positive selection for some inversions, variable between foundations. Signs of negative selection were more frequent, in particular for most cold-climate standard inversions across the three foundations. We found that previously observed convergence at the phenotypic level in these populations was not associated with convergence in inversion frequencies. In conclusion, our study shows that selection has shaped the evolutionary dynamics of inversion frequencies, but doing so within the constraints imposed by previous history. Both history and selection are therefore fundamental to predict the evolutionary potential of different populations to respond to global environmental changes. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

The Source Inversion Validation (SIV) Initiative: A Collaborative Study on Uncertainty Quantification in Earthquake Source Inversions

NASA Astrophysics Data System (ADS)

Mai, P. M.; Schorlemmer, D.; Page, M.

2012-04-01

Earthquake source inversions image the spatio-temporal rupture evolution on one or more fault planes using seismic and/or geodetic data. Such studies are critically important for earthquake seismology in general, and for advancing seismic hazard analysis in particular, as they reveal earthquake source complexity and help (i) to investigate earthquake mechanics; (ii) to develop spontaneous dynamic rupture models; (iii) to build models for generating rupture realizations for ground-motion simulations. In applications (i - iii), the underlying finite-fault source models are regarded as "data" (input information), but their uncertainties are essentially unknown. After all, source models are obtained from solving an inherently ill-posed inverse problem to which many a priori assumptions and uncertain observations are applied. The Source Inversion Validation (SIV) project is a collaborative effort to better understand the variability between rupture models for a single earthquake (as manifested in the finite-source rupture model database) and to develop robust uncertainty quantification for earthquake source inversions. The SIV project highlights the need to develop a long-standing and rigorous testing platform to examine the current state-of-the-art in earthquake source inversion, and to develop and test novel source inversion approaches. We will review the current status of the SIV project, and report the findings and conclusions of the recent workshops. We will briefly discuss several source-inversion methods, how they treat uncertainties in data, and assess the posterior model uncertainty. Case studies include initial forward-modeling tests on Green's function calculations, and inversion results for synthetic data from spontaneous dynamic crack-like strike-slip earthquake on steeply dipping fault, embedded in a layered crustal velocity-density structure.

Is chemical heating a major cause of the mesosphere inversion layer?

NASA Technical Reports Server (NTRS)

Meriwether, John W.; Mlynczak, Martin G.

1995-01-01

A region of thermal enhancement of the mesosphere has been detected on numerous occasions by in situ measurements, remote sensing from space, and lidar techniques. The source of these 'temperature inversion layers' has been attributed in the literature to the dissipation relating to dynamical forcing by gravity wave or tidal activity. However, evidence that gravity wave breaking can produce the inversion layer with amplitude as large as that observed in lidar measurements has been limited to results of numerical modeling. An alternative source for the production of the thermal inversion layer in the mesosphere is the direct deposition of heat by exothermic chemical reactions. Two-dimensional modeling combining a comprehensive model of the mesosphere photochemistry with the dynamical transport of long-lived species shows that the region from 80 to 95 km may be heated as much as 3 to 10 K/d during the night and half this rate during the day. Given the uncertainties in our understanding of the dynamics and chemistry for the mesopause region, separating the two sources by passive observations of the mesosphere thermal structure looks to be difficult. Therefore we have considered an active means for producing a mesopause thermal layer, namely the release of ozone into the upper mesosphere from a rocket payload. The induced effects would include artificial enhancements of the OH and Na airglow intensities as well as the mesopause thermal structure. The advantages of the rocket release of ozone is that detection of these effects by ground-based imaging, radar, and lidar systems and comparison of these effects with model predictions would help quantify the partition of the artificial inversion layer production into sources of dynamical and chemical forcing.

Application of Adaptive Autopilot Designs for an Unmanned Aerial Vehicle

NASA Technical Reports Server (NTRS)

Shin, Yoonghyun; Calise, Anthony J.; Motter, Mark A.

2005-01-01

This paper summarizes the application of two adaptive approaches to autopilot design, and presents an evaluation and comparison of the two approaches in simulation for an unmanned aerial vehicle. One approach employs two-stage dynamic inversion and the other employs feedback dynamic inversions based on a command augmentation system. Both are augmented with neural network based adaptive elements. The approaches permit adaptation to both parametric uncertainty and unmodeled dynamics, and incorporate a method that permits adaptation during periods of control saturation. Simulation results for an FQM-117B radio controlled miniature aerial vehicle are presented to illustrate the performance of the neural network based adaptation.

Constraining inverse-curvature gravity with supernovae.

PubMed

Mena, Olga; Santiago, José; Weller, Jochen

2006-02-03

We show that models of generalized modified gravity, with inverse powers of the curvature, can explain the current accelerated expansion of the Universe without resorting to dark energy and without conflicting with solar system experiments. We have solved the Friedmann equations for the full dynamical range of the evolution of the Universe and performed a detailed analysis of supernovae data in the context of such models that results in an excellent fit. If we further include constraints on the current expansion of the Universe and on its age, we obtain that the matter content of the Universe is 0.07

Spatial operator approach to flexible multibody system dynamics and control

NASA Technical Reports Server (NTRS)

Rodriguez, G.

1991-01-01

The inverse and forward dynamics problems for flexible multibody systems were solved using the techniques of spatially recursive Kalman filtering and smoothing. These algorithms are easily developed using a set of identities associated with mass matrix factorization and inversion. These identities are easily derived using the spatial operator algebra developed by the author. Current work is aimed at computational experiments with the described algorithms and at modelling for control design of limber manipulator systems. It is also aimed at handling and manipulation of flexible objects.

Study of crash energy absorption characteristics of inversion tube on passenger vehicle

NASA Astrophysics Data System (ADS)

Liu, Jiandong; Liu, Tao; Yao, Shengjie; Zhao, Rutao

2017-09-01

This article studied the energy absorption characteristics of the inversion tube and acquired the inversion tube design key dimensions under theoretical conditions by performing formula derivation in the quasi-static and dynamic state based on the working principle of the inversion tube: free inversion. The article further adopted HyperMesh and LS-Dyna to perform simulation and compared the simulation result with the theoretical calculating value for comparison. The design was applied in the full-vehicle model to perform 50km/h front fullwidth crash simulation. The findings showed that the deformation mode of the inversion tube in the full-vehicle crash was consistent with the design mode, and the inversion tube absorbed 33.0% of total energy, thereby conforming to the vehicle safety design requirements.

Coupled land surface-subsurface hydrogeophysical inverse modeling to estimate soil organic carbon content and explore associated hydrological and thermal dynamics in the Arctic tundra

NASA Astrophysics Data System (ADS)

Phuong Tran, Anh; Dafflon, Baptiste; Hubbard, Susan S.

2017-09-01

Quantitative characterization of soil organic carbon (OC) content is essential due to its significant impacts on surface-subsurface hydrological-thermal processes and microbial decomposition of OC, which both in turn are important for predicting carbon-climate feedbacks. While such quantification is particularly important in the vulnerable organic-rich Arctic region, it is challenging to achieve due to the general limitations of conventional core sampling and analysis methods, and to the extremely dynamic nature of hydrological-thermal processes associated with annual freeze-thaw events. In this study, we develop and test an inversion scheme that can flexibly use single or multiple datasets - including soil liquid water content, temperature and electrical resistivity tomography (ERT) data - to estimate the vertical distribution of OC content. Our approach relies on the fact that OC content strongly influences soil hydrological-thermal parameters and, therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. We employ the Community Land Model to simulate nonisothermal surface-subsurface hydrological dynamics from the bedrock to the top of canopy, with consideration of land surface processes (e.g., solar radiation balance, evapotranspiration, snow accumulation and melting) and ice-liquid water phase transitions. For inversion, we combine a deterministic and an adaptive Markov chain Monte Carlo (MCMC) optimization algorithm to estimate a posteriori distributions of desired model parameters. For hydrological-thermal-to-geophysical variable transformation, the simulated subsurface temperature, liquid water content and ice content are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using different numerical experiments and evaluate the influence of measurement errors and benefit of joint inversion on the estimation of OC and other parameters. We also quantify the propagation of uncertainty from the estimated parameters to prediction of hydrological-thermal responses. We find that, compared to inversion of single dataset (temperature, liquid water content or apparent resistivity), joint inversion of these datasets significantly reduces parameter uncertainty. We find that the joint inversion approach is able to estimate OC and sand content within the shallow active layer (top 0.3 m of soil) with high reliability. Due to the small variations of temperature and moisture within the shallow permafrost (here at about 0.6 m depth), the approach is unable to estimate OC with confidence. However, if the soil porosity is functionally related to the OC and mineral content, which is often observed in organic-rich Arctic soil, the uncertainty of OC estimate at this depth remarkably decreases. Our study documents the value of the new surface-subsurface, deterministic-stochastic inversion approach, as well as the benefit of including multiple types of data to estimate OC and associated hydrological-thermal dynamics.

Informativeness of Wind Data in Linear Madden-Julian Oscillation Prediction

DTIC Science & Technology

2016-08-15

Linear inverse models (LIMs) are used to explore predictability and information content of the Madden–Julian Oscillation (MJO). Hindcast skill for...mostly at the largest scales, adds 1–2 days of skill. Keywords: linear inverse modeling; Madden–Julian Oscillation; sub-seasonal prediction 1...tion that may reflect on the MJO’s incompletely under- stood dynamics. Cavanaugh et al. (2014, hereafter C14) explored the skill of linear inverse

Inference of chromosomal inversion dynamics from Pool-Seq data in natural and laboratory populations of Drosophila melanogaster.

PubMed

Kapun, Martin; van Schalkwyk, Hester; McAllister, Bryant; Flatt, Thomas; Schlötterer, Christian

2014-04-01

Sequencing of pools of individuals (Pool-Seq) represents a reliable and cost-effective approach for estimating genome-wide SNP and transposable element insertion frequencies. However, Pool-Seq does not provide direct information on haplotypes so that, for example, obtaining inversion frequencies has not been possible until now. Here, we have developed a new set of diagnostic marker SNPs for seven cosmopolitan inversions in Drosophila melanogaster that can be used to infer inversion frequencies from Pool-Seq data. We applied our novel marker set to Pool-Seq data from an experimental evolution study and from North American and Australian latitudinal clines. In the experimental evolution data, we find evidence that positive selection has driven the frequencies of In(3R)C and In(3R)Mo to increase over time. In the clinal data, we confirm the existence of frequency clines for In(2L)t, In(3L)P and In(3R)Payne in both North America and Australia and detect a previously unknown latitudinal cline for In(3R)Mo in North America. The inversion markers developed here provide a versatile and robust tool for characterizing inversion frequencies and their dynamics in Pool-Seq data from diverse D. melanogaster populations. © 2013 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd.

Inference of chromosomal inversion dynamics from Pool-Seq data in natural and laboratory populations of Drosophila melanogaster

PubMed Central

Kapun, Martin; van Schalkwyk, Hester; McAllister, Bryant; Flatt, Thomas; Schlötterer, Christian

2014-01-01

Sequencing of pools of individuals (Pool-Seq) represents a reliable and cost-effective approach for estimating genome-wide SNP and transposable element insertion frequencies. However, Pool-Seq does not provide direct information on haplotypes so that, for example, obtaining inversion frequencies has not been possible until now. Here, we have developed a new set of diagnostic marker SNPs for seven cosmopolitan inversions in Drosophila melanogaster that can be used to infer inversion frequencies from Pool-Seq data. We applied our novel marker set to Pool-Seq data from an experimental evolution study and from North American and Australian latitudinal clines. In the experimental evolution data, we find evidence that positive selection has driven the frequencies of In(3R)C and In(3R)Mo to increase over time. In the clinal data, we confirm the existence of frequency clines for In(2L)t, In(3L)P and In(3R)Payne in both North America and Australia and detect a previously unknown latitudinal cline for In(3R)Mo in North America. The inversion markers developed here provide a versatile and robust tool for characterizing inversion frequencies and their dynamics in Pool-Seq data from diverse D. melanogaster populations. PMID:24372777

Spin pumping and inverse spin Hall voltages from dynamical antiferromagnets

NASA Astrophysics Data System (ADS)

Johansen, Øyvind; Brataas, Arne

2017-06-01

Dynamical antiferromagnets can pump spins into adjacent conductors. The high antiferromagnetic resonance frequencies represent a challenge for experimental detection, but magnetic fields can reduce these resonance frequencies. We compute the ac and dc inverse spin Hall voltages resulting from dynamical spin excitations as a function of a magnetic field along the easy axis and the polarization of the driving ac magnetic field perpendicular to the easy axis. We consider the insulating antiferromagnets MnF2,FeF2, and NiO. Near the spin-flop transition, there is a significant enhancement of the dc spin pumping and inverse spin Hall voltage for the uniaxial antiferromagnets MnF2 and FeF2. In the uniaxial antiferromagnets it is also found that the ac spin pumping is independent of the external magnetic field when the driving field has the optimal circular polarization. In the biaxial NiO, the voltages are much weaker, and there is no spin-flop enhancement of the dc component.

Dynamical arrest with zero complexity: The unusual behavior of the spherical Blume-Emery-Griffiths disordered model

NASA Astrophysics Data System (ADS)

Rainone, Corrado; Ferrari, Ulisse; Paoluzzi, Matteo; Leuzzi, Luca

2015-12-01

The short- and long-time dynamics of model systems undergoing a glass transition with apparent inversion of Kauzmann and dynamical arrest glass transition lines is investigated. These models belong to the class of the spherical mean-field approximation of a spin-1 model with p -body quenched disordered interaction, with p >2 , termed spherical Blume-Emery-Griffiths models. Depending on temperature and chemical potential the system is found in a paramagnetic or in a glassy phase and the transition between these phases can be of a different nature. In specific regions of the phase diagram coexistence of low-density and high-density paramagnets can occur, as well as the coexistence of spin-glass and paramagnetic phases. The exact static solution for the glassy phase is known to be obtained by the one-step replica symmetry breaking ansatz. Different scenarios arise for both the dynamic and the thermodynamic transitions. These include: (i) the usual random first-order transition (Kauzmann-like) for mean-field glasses preceded by a dynamic transition, (ii) a thermodynamic first-order transition with phase coexistence and latent heat, and (iii) a regime of apparent inversion of static transition line and dynamic transition lines, the latter defined as a nonzero complexity line. The latter inversion, though, turns out to be preceded by a dynamical arrest line at higher temperature. Crossover between different regimes is analyzed by solving mode-coupling-theory equations near the boundaries of paramagnetic solutions and the relationship with the underlying statics is discussed.

Vitamin D supplementation has minor effects on parathyroid hormone and bone turnover markers in vitamin D-deficient bedridden older patients.

PubMed

Björkman, Mikko; Sorva, Antti; Risteli, Juha; Tilvis, Reijo

2008-01-01

to evaluate the effects of vitamin D supplementation on parathyroid function and bone turnover in aged, chronically immobile patients. a randomised double-blind controlled trial. two hundred and eighteen long-term inpatients aged over 65 years. the patients were randomised into treatment groups of I-III, each receiving 0 IU, 400 IU and 1200 IU cholecalciferol per day, respectively. In case of inadequate consumption of dairy products, patients received a daily calcium substitution of 500 mg. plasma concentrations of 25-hydroxyvitamin D (25-OHD), intact parathyroid hormone (PTH), amino-terminal propeptide of type I procollagen (PINP), a marker of bone formation, and carboxy-terminal telopeptide of type I collagen (ICTP), a marker of bone resorption, were measured at baseline and after 6 months. the patients (age 84.5 years) were chronically bedridden. The baseline 25-OHD was low (23 nmol/l), correlated inversely with PINP, and tended to associate inversely with PTH. The prevalence of vitamin D deficiency (VDD) (25-OHD < 50 nmol/l) was 98% and PTH was elevated in 23% of the patients. Vitamin D supplementation significantly increased 25-OHD concentrations (124% group II, 204% group III) and decreased PTH (-7% group II, -8% group III). PINP tended to decrease, but ICTP tended to increase, and only their ratio decreased significantly. The tendency of ICTP to increase was inconsistent. Changes in 25-OHD correlated inversely with those in PTH and PINP. vitamin D supplementation has minor effects on PTH and bone turnover in chronically immobilised aged patients with VDD. Further comparative studies and meta-analyses are warranted to elucidate the confounding effects of different mobility levels on the benefits of vitamin D supplementation in patients with differing baseline PTH levels.

Predicting future learning from baseline network architecture.

PubMed

Mattar, Marcelo G; Wymbs, Nicholas F; Bock, Andrew S; Aguirre, Geoffrey K; Grafton, Scott T; Bassett, Danielle S

2018-05-15

Human behavior and cognition result from a complex pattern of interactions between brain regions. The flexible reconfiguration of these patterns enables behavioral adaptation, such as the acquisition of a new motor skill. Yet, the degree to which these reconfigurations depend on the brain's baseline sensorimotor integration is far from understood. Here, we asked whether spontaneous fluctuations in sensorimotor networks at baseline were predictive of individual differences in future learning. We analyzed functional MRI data from 19 participants prior to six weeks of training on a new motor skill. We found that visual-motor connectivity was inversely related to learning rate: sensorimotor autonomy at baseline corresponded to faster learning in the future. Using three additional scans, we found that visual-motor connectivity at baseline is a relatively stable individual trait. These results suggest that individual differences in motor skill learning can be predicted from sensorimotor autonomy at baseline prior to task execution. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Feasible Muscle Activation Ranges Based on Inverse Dynamics Analyses of Human Walking

PubMed Central

Simpson, Cole S.; Sohn, M. Hongchul; Allen, Jessica L.; Ting, Lena H.

2015-01-01

Although it is possible to produce the same movement using an infinite number of different muscle activation patterns owing to musculoskeletal redundancy, the degree to which observed variations in muscle activity can deviate from optimal solutions computed from biomechanical models is not known. Here, we examined the range of biomechanically permitted activation levels in individual muscles during human walking using a detailed musculoskeletal model and experimentally-measured kinetics and kinematics. Feasible muscle activation ranges define the minimum and maximum possible level of each muscle’s activation that satisfy inverse dynamics joint torques assuming that all other muscles can vary their activation as needed. During walking, 73% of the muscles had feasible muscle activation ranges that were greater than 95% of the total muscle activation range over more than 95% of the gait cycle, indicating that, individually, most muscles could be fully active or fully inactive while still satisfying inverse dynamics joint torques. Moreover, the shapes of the feasible muscle activation ranges did not resemble previously-reported muscle activation patterns nor optimal solutions, i.e. static optimization and computed muscle control, that are based on the same biomechanical constraints. Our results demonstrate that joint torque requirements from standard inverse dynamics calculations are insufficient to define the activation of individual muscles during walking in healthy individuals. Identifying feasible muscle activation ranges may be an effective way to evaluate the impact of additional biomechanical and/or neural constraints on possible versus actual muscle activity in both normal and impaired movements. PMID:26300401

Analyzing industrial energy use through ordinary least squares regression models

NASA Astrophysics Data System (ADS)

Golden, Allyson Katherine

Extensive research has been performed using regression analysis and calibrated simulations to create baseline energy consumption models for residential buildings and commercial institutions. However, few attempts have been made to discuss the applicability of these methodologies to establish baseline energy consumption models for industrial manufacturing facilities. In the few studies of industrial facilities, the presented linear change-point and degree-day regression analyses illustrate ideal cases. It follows that there is a need in the established literature to discuss the methodologies and to determine their applicability for establishing baseline energy consumption models of industrial manufacturing facilities. The thesis determines the effectiveness of simple inverse linear statistical regression models when establishing baseline energy consumption models for industrial manufacturing facilities. Ordinary least squares change-point and degree-day regression methods are used to create baseline energy consumption models for nine different case studies of industrial manufacturing facilities located in the southeastern United States. The influence of ambient dry-bulb temperature and production on total facility energy consumption is observed. The energy consumption behavior of industrial manufacturing facilities is only sometimes sufficiently explained by temperature, production, or a combination of the two variables. This thesis also provides methods for generating baseline energy models that are straightforward and accessible to anyone in the industrial manufacturing community. The methods outlined in this thesis may be easily replicated by anyone that possesses basic spreadsheet software and general knowledge of the relationship between energy consumption and weather, production, or other influential variables. With the help of simple inverse linear regression models, industrial manufacturing facilities may better understand their energy consumption and production behavior, and identify opportunities for energy and cost savings. This thesis study also utilizes change-point and degree-day baseline energy models to disaggregate facility annual energy consumption into separate industrial end-user categories. The baseline energy model provides a suitable and economical alternative to sub-metering individual manufacturing equipment. One case study describes the conjoined use of baseline energy models and facility information gathered during a one-day onsite visit to perform an end-point energy analysis of an injection molding facility conducted by the Alabama Industrial Assessment Center. Applying baseline regression model results to the end-point energy analysis allowed the AIAC to better approximate the annual energy consumption of the facility's HVAC system.

Oxidative stress induces transient O-GlcNAc elevation and tau dephosphorylation in SH-SY5Y cells.

PubMed

Kátai, Emese; Pál, József; Poór, Viktor Soma; Purewal, Rupeena; Miseta, Attila; Nagy, Tamás

2016-12-01

O-linked β-N-acetlyglucosamine or O-GlcNAc modification is a dynamic post-translational modification occurring on the Ser/Thr residues of many intracellular proteins. The chronic imbalance between phosphorylation and O-GlcNAc on tau protein is considered as one of the main hallmarks of Alzheimer's disease. In recent years, many studies also showed that O-GlcNAc levels can elevate upon acute stress and suggested that this might facilitate cell survival. However, many consider chronic stress, including oxidative damage as a major risk factor in the development of the disease. In this study, using the neuronal cell line SH-SY5Y we investigated the dynamic nature of O-GlcNAc after treatment with 0.5 mM H 2 O 2 for 30 min. to induce oxidative stress. We found that overall O-GlcNAc quickly increased and reached peak level at around 2 hrs post-stress, then returned to baseline levels after about 24 hrs. Interestingly, we also found that tau protein phosphorylation at site S262 showed parallel, whereas at S199 and PHF1 sites showed inverse dynamic to O-Glycosylation. In conclusion, our results show that temporary elevation in O-GlcNAc modification after H 2 O 2 -induced oxidative stress is detectable in cells of neuronal origin. Furthermore, oxidative stress changes the dynamic balance between O-GlcNAc and phosphorylation on tau proteins. © 2016 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

Dynamic chirp control of all-optical format-converted pulsed data from a multi-wavelength inverse-optical-comb injected semiconductor optical amplifier.

PubMed

Lin, Gong-Ru; Pan, Ci-Ling; Yu, Kun-Chieh

2007-10-01

By spectrally and temporally reshaping the gain-window of a traveling-wave semiconductor optical amplifier (TWSOA) with a backward injected multi- or single-wavelength inverse-optical-comb, we theoretically and experimentally investigate the dynamic frequency chirp of the all-optical 10GBit/s Return-to-Zero (RZ) data-stream format-converted from the TWSOA under strong cross-gain depletion scheme. The multi-wavelength inverse-optical-comb injection effectively depletes the TWSOA gain spectrally and temporally, remaining a narrow gain-window and a reduced spectral linewidth and provide a converted RZ data with a smaller peak-to-peak frequency chirp of 6.7 GHz. Even at high inverse-optical-comb injection power and highly biased current condition for improving the operational bit-rate, the chirp of the multi-wavelength-injection converted RZ pulse is still 2.1-GHz smaller than that obtained by using single-wavelength injection at a cost of slight pulse-width broadening by 1 ps.

Charge Inversion by Electrostatic Complexation: Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Faraudo, Jordi; Travesset, Alex

2007-03-01

Ions near interfaces play an important role in many biological and physico-chemical processes and exhibit a fascinating diverse range of phenomena. A relevant example is charge inversion, where interfacial charges attract counterions in excess of their own nominal charge, thus leading to an inversion of the sign of the interfacial charge. In this work, we argue that in the case of amphiphilic interfaces, charge inversion can be generated by complexation, that is, electrostatic complexes containing several counterions bound to amphiphilic molecules. The formation of these complexes require the presence at the interface of groups with conformational degrees of freedom with many electronegative atoms. We illustrate this mechanism by analyzing all atomic molecular dynamics simulations of a DMPA (Dimirystoil-Phosphatidic acid) phospholipid monolayer in contact with divalent counterions. The results are found to be in agreement with recent experimental results on Langmuir monolayers. We also discuss the implications for biological systems, as Phosphatidic acid is emerging as a key signaling phospholipid.

Regularity Aspects in Inverse Musculoskeletal Biomechanics

NASA Astrophysics Data System (ADS)

Lund, Marie; Stâhl, Fredrik; Gulliksson, Mârten

2008-09-01

Inverse simulations of musculoskeletal models computes the internal forces such as muscle and joint reaction forces, which are hard to measure, using the more easily measured motion and external forces as input data. Because of the difficulties of measuring muscle forces and joint reactions, simulations are hard to validate. One way of reducing errors for the simulations is to ensure that the mathematical problem is well-posed. This paper presents a study of regularity aspects for an inverse simulation method, often called forward dynamics or dynamical optimization, that takes into account both measurement errors and muscle dynamics. Regularity is examined for a test problem around the optimum using the approximated quadratic problem. The results shows improved rank by including a regularization term in the objective that handles the mechanical over-determinancy. Using the 3-element Hill muscle model the chosen regularization term is the norm of the activation. To make the problem full-rank only the excitation bounds should be included in the constraints. However, this results in small negative values of the activation which indicates that muscles are pushing and not pulling, which is unrealistic but the error maybe small enough to be accepted for specific applications. These results are a start to ensure better results of inverse musculoskeletal simulations from a numerical point of view.

Feedback control by online learning an inverse model.

PubMed

Waegeman, Tim; Wyffels, Francis; Schrauwen, Francis

2012-10-01

A model, predictor, or error estimator is often used by a feedback controller to control a plant. Creating such a model is difficult when the plant exhibits nonlinear behavior. In this paper, a novel online learning control framework is proposed that does not require explicit knowledge about the plant. This framework uses two learning modules, one for creating an inverse model, and the other for actually controlling the plant. Except for their inputs, they are identical. The inverse model learns by the exploration performed by the not yet fully trained controller, while the actual controller is based on the currently learned model. The proposed framework allows fast online learning of an accurate controller. The controller can be applied on a broad range of tasks with different dynamic characteristics. We validate this claim by applying our control framework on several control tasks: 1) the heating tank problem (slow nonlinear dynamics); 2) flight pitch control (slow linear dynamics); and 3) the balancing problem of a double inverted pendulum (fast linear and nonlinear dynamics). The results of these experiments show that fast learning and accurate control can be achieved. Furthermore, a comparison is made with some classical control approaches, and observations concerning convergence and stability are made.

Reconfigurable Control with Neural Network Augmentation for a Modified F-15 Aircraft

NASA Technical Reports Server (NTRS)

Burken, John J.; Williams-Hayes, Peggy; Kaneshige, John T.; Stachowiak, Susan J.

2006-01-01

Description of the performance of a simplified dynamic inversion controller with neural network augmentation follows. Simulation studies focus on the results with and without neural network adaptation through the use of an F-15 aircraft simulator that has been modified to include canards. Simulated control law performance with a surface failure, in addition to an aerodynamic failure, is presented. The aircraft, with adaptation, attempts to minimize the inertial cross-coupling effect of the failure (a control derivative anomaly associated with a jammed control surface). The dynamic inversion controller calculates necessary surface commands to achieve desired rates. The dynamic inversion controller uses approximate short period and roll axis dynamics. The yaw axis controller is a sideslip rate command system. Methods are described to reduce the cross-coupling effect and maintain adequate tracking errors for control surface failures. The aerodynamic failure destabilizes the pitching moment due to angle of attack. The results show that control of the aircraft with the neural networks is easier (more damped) than without the neural networks. Simulation results show neural network augmentation of the controller improves performance with aerodynamic and control surface failures in terms of tracking error and cross-coupling reduction.

Inferring Fault Frictional and Reservoir Hydraulic Properties From Injection-Induced Seismicity

NASA Astrophysics Data System (ADS)

Jagalur-Mohan, Jayanth; Jha, Birendra; Wang, Zheng; Juanes, Ruben; Marzouk, Youssef

2018-02-01

Characterizing the rheological properties of faults and the evolution of fault friction during seismic slip are fundamental problems in geology and seismology. Recent increases in the frequency of induced earthquakes have intensified the need for robust methods to estimate fault properties. Here we present a novel approach for estimation of aquifer and fault properties, which combines coupled multiphysics simulation of injection-induced seismicity with adaptive surrogate-based Bayesian inversion. In a synthetic 2-D model, we use aquifer pressure, ground displacements, and fault slip measurements during fluid injection to estimate the dynamic fault friction, the critical slip distance, and the aquifer permeability. Our forward model allows us to observe nonmonotonic evolutions of shear traction and slip on the fault resulting from the interplay of several physical mechanisms, including injection-induced aquifer expansion, stress transfer along the fault, and slip-induced stress relaxation. This interplay provides the basis for a successful joint inversion of induced seismicity, yielding well-informed Bayesian posterior distributions of dynamic friction and critical slip. We uncover an inverse relationship between dynamic friction and critical slip distance, which is in agreement with the small dynamic friction and large critical slip reported during seismicity on mature faults.

Adaptive Control Using Neural Network Augmentation for a Modified F-15 Aircraft

NASA Technical Reports Server (NTRS)

Burken, John J.; Williams-Hayes, Peggy; Karneshige, J. T.; Stachowiak, Susan J.

2006-01-01

Description of the performance of a simplified dynamic inversion controller with neural network augmentation follows. Simulation studies focus on the results with and without neural network adaptation through the use of an F-15 aircraft simulator that has been modified to include canards. Simulated control law performance with a surface failure, in addition to an aerodynamic failure, is presented. The aircraft, with adaptation, attempts to minimize the inertial cross-coupling effect of the failure (a control derivative anomaly associated with a jammed control surface). The dynamic inversion controller calculates necessary surface commands to achieve desired rates. The dynamic inversion controller uses approximate short period and roll axis dynamics. The yaw axis controller is a sideslip rate command system. Methods are described to reduce the cross-coupling effect and maintain adequate tracking errors for control surface failures. The aerodynamic failure destabilizes the pitching moment due to angle of attack. The results show that control of the aircraft with the neural networks is easier (more damped) than without the neural networks. Simulation results show neural network augmentation of the controller improves performance with aerodynamic and control surface failures in terms of tracking error and cross-coupling reduction.

System Identification for Nonlinear Control Using Neural Networks

NASA Technical Reports Server (NTRS)

Stengel, Robert F.; Linse, Dennis J.

1990-01-01

An approach to incorporating artificial neural networks in nonlinear, adaptive control systems is described. The controller contains three principal elements: a nonlinear inverse dynamic control law whose coefficients depend on a comprehensive model of the plant, a neural network that models system dynamics, and a state estimator whose outputs drive the control law and train the neural network. Attention is focused on the system identification task, which combines an extended Kalman filter with generalized spline function approximation. Continual learning is possible during normal operation, without taking the system off line for specialized training. Nonlinear inverse dynamic control requires smooth derivatives as well as function estimates, imposing stringent goals on the approximating technique.

Inverse Dynamics Model for the Ankle Joint with Applications in Tibia Malleolus Fracture

NASA Astrophysics Data System (ADS)

Budescu, E.; Merticaru, E.; Chirazi, M.

The paper presents a biomechanical model of the ankle joint, in order to determine the force and the torque of reaction into the articulation, through inverse dynamic analysis, in various stages of the gait. Thus, knowing the acceleration of the foot and the reaction force between foot and ground during the gait, determined by experimental measurement, there was calculated, for five different positions of the foot, the joint reaction forces, on the basis of dynamic balance equations. The values numerically determined were compared with the admissible forces appearing in the technical systems of osteosynthesis of tibia malleolus fracture, in order to emphasize the motion restrictions during bone healing.

Kinematics and dynamics of robotic systems with multiple closed loops

NASA Astrophysics Data System (ADS)

Zhang, Chang-De

The kinematics and dynamics of robotic systems with multiple closed loops, such as Stewart platforms, walking machines, and hybrid manipulators, are studied. In the study of kinematics, focus is on the closed-form solutions of the forward position analysis of different parallel systems. A closed-form solution means that the solution is expressed as a polynomial in one variable. If the order of the polynomial is less than or equal to four, the solution has analytical closed-form. First, the conditions of obtaining analytical closed-form solutions are studied. For a Stewart platform, the condition is found to be that one rotational degree of freedom of the output link is decoupled from the other five. Based on this condition, a class of Stewart platforms which has analytical closed-form solution is formulated. Conditions of analytical closed-form solution for other parallel systems are also studied. Closed-form solutions of forward kinematics for walking machines and multi-fingered grippers are then studied. For a parallel system with three three-degree-of-freedom subchains, there are 84 possible ways to select six independent joints among nine joints. These 84 ways can be classified into three categories: Category 3:3:0, Category 3:2:1, and Category 2:2:2. It is shown that the first category has no solutions; the solutions of the second category have analytical closed-form; and the solutions of the last category are higher order polynomials. The study is then extended to a nearly general Stewart platform. The solution is a 20th order polynomial and the Stewart platform has a maximum of 40 possible configurations. Also, the study is extended to a new class of hybrid manipulators which consists of two serially connected parallel mechanisms. In the study of dynamics, a computationally efficient method for inverse dynamics of manipulators based on the virtual work principle is developed. Although this method is comparable with the recursive Newton-Euler method for serial manipulators, its advantage is more noteworthy when applied to parallel systems. An approach of inverse dynamics of a walking machine is also developed, which includes inverse dynamic modeling, foot force distribution, and joint force/torque allocation.

Consumption of spicy foods and total and cause specific mortality: population based cohort study.

PubMed

Lv, Jun; Qi, Lu; Yu, Canqing; Yang, Ling; Guo, Yu; Chen, Yiping; Bian, Zheng; Sun, Dianjianyi; Du, Jianwei; Ge, Pengfei; Tang, Zhenzhu; Hou, Wei; Li, Yanjie; Chen, Junshi; Chen, Zhengming; Li, Liming

2015-08-04

To examine the associations between the regular consumption of spicy foods and total and cause specific mortality. Population based prospective cohort study. China Kadoorie Biobank in which participants from 10 geographically diverse areas across China were enrolled between 2004 and 2008. 199,293 men and 288,082 women aged 30 to 79 years at baseline after excluding participants with cancer, heart disease, and stroke at baseline. Consumption frequency of spicy foods, self reported once at baseline. Total and cause specific mortality. During 3,500,004 person years of follow-up between 2004 and 2013 (median 7.2 years), a total of 11,820 men and 8404 women died. Absolute mortality rates according to spicy food consumption categories were 6.1, 4.4, 4.3, and 5.8 deaths per 1000 person years for participants who ate spicy foods less than once a week, 1 or 2, 3 to 5, and 6 or 7 days a week, respectively. Spicy food consumption showed highly consistent inverse associations with total mortality among both men and women after adjustment for other known or potential risk factors. In the whole cohort, compared with those who ate spicy foods less than once a week, the adjusted hazard ratios for death were 0.90 (95% confidence interval 0.84 to 0.96), 0.86 (0.80 to 0.92), and 0.86 (0.82 to 0.90) for those who ate spicy food 1 or 2, 3 to 5, and 6 or 7 days a week, respectively. Compared with those who ate spicy foods less than once a week, those who consumed spicy foods 6 or 7 days a week showed a 14% relative risk reduction in total mortality. The inverse association between spicy food consumption and total mortality was stronger in those who did not consume alcohol than those who did (P=0.033 for interaction). Inverse associations were also observed for deaths due to cancer, ischemic heart diseases, and respiratory diseases. In this large prospective study, the habitual consumption of spicy foods was inversely associated with total and certain cause specific mortality, independent of other risk factors of death. © Lv et al 2015.

Dynamic identification of growth and survival kinetic parameters of microorganisms in foods

USDA-ARS?s Scientific Manuscript database

Inverse analysis is a mathematical method used in predictive microbiology to determine the kinetic parameters of microbial growth and survival in foods. The traditional approach in inverse analysis relies on isothermal experiments that are time-consuming and labor-intensive, and errors are accumula...

Integrated approach to estimate the ocean's time variable dynamic topography including its covariance matrix

NASA Astrophysics Data System (ADS)

Müller, Silvia; Brockmann, Jan Martin; Schuh, Wolf-Dieter

2015-04-01

The ocean's dynamic topography as the difference between the sea surface and the geoid reflects many characteristics of the general ocean circulation. Consequently, it provides valuable information for evaluating or tuning ocean circulation models. The sea surface is directly observed by satellite radar altimetry while the geoid cannot be observed directly. The satellite-based gravity field determination requires different measurement principles (satellite-to-satellite tracking (e.g. GRACE), satellite-gravity-gradiometry (GOCE)). In addition, hydrographic measurements (salinity, temperature and pressure; near-surface velocities) provide information on the dynamic topography. The observation types have different representations and spatial as well as temporal resolutions. Therefore, the determination of the dynamic topography is not straightforward. Furthermore, the integration of the dynamic topography into ocean circulation models requires not only the dynamic topography itself but also its inverse covariance matrix on the ocean model grid. We developed a rigorous combination method in which the dynamic topography is parameterized in space as well as in time. The altimetric sea surface heights are expressed as a sum of geoid heights represented in terms of spherical harmonics and the dynamic topography parameterized by a finite element method which can be directly related to the particular ocean model grid. Besides the difficult task of combining altimetry data with a gravity field model, a major aspect is the consistent combination of satellite data and in-situ observations. The particular characteristics and the signal content of the different observations must be adequately considered requiring the introduction of auxiliary parameters. Within our model the individual observation groups are combined in terms of normal equations considering their full covariance information; i.e. a rigorous variance/covariance propagation from the original measurements to the final product is accomplished. In conclusion, the developed integrated approach allows for estimating the dynamic topography and its inverse covariance matrix on arbitrary grids in space and time. The inverse covariance matrix contains the appropriate weights for model-data misfits in least-squares ocean model inversions. The focus of this study is on the North Atlantic Ocean. We will present the conceptual design and dynamic topography estimates based on time variable data from seven satellite altimeter missions (Jason-1, Jason-2, Topex/Poseidon, Envisat, ERS-2, GFO, Cryosat2) in combination with the latest GOCE gravity field model and in-situ data from the Argo floats and near-surface drifting buoys.

Semiautomatic and Automatic Cooperative Inversion of Seismic and Magnetotelluric Data

NASA Astrophysics Data System (ADS)

Le, Cuong V. A.; Harris, Brett D.; Pethick, Andrew M.; Takam Takougang, Eric M.; Howe, Brendan

2016-09-01

Natural source electromagnetic methods have the potential to recover rock property distributions from the surface to great depths. Unfortunately, results in complex 3D geo-electrical settings can be disappointing, especially where significant near-surface conductivity variations exist. In such settings, unconstrained inversion of magnetotelluric data is inexorably non-unique. We believe that: (1) correctly introduced information from seismic reflection can substantially improve MT inversion, (2) a cooperative inversion approach can be automated, and (3) massively parallel computing can make such a process viable. Nine inversion strategies including baseline unconstrained inversion and new automated/semiautomated cooperative inversion approaches are applied to industry-scale co-located 3D seismic and magnetotelluric data sets. These data sets were acquired in one of the Carlin gold deposit districts in north-central Nevada, USA. In our approach, seismic information feeds directly into the creation of sets of prior conductivity model and covariance coefficient distributions. We demonstrate how statistical analysis of the distribution of selected seismic attributes can be used to automatically extract subvolumes that form the framework for prior model 3D conductivity distribution. Our cooperative inversion strategies result in detailed subsurface conductivity distributions that are consistent with seismic, electrical logs and geochemical analysis of cores. Such 3D conductivity distributions would be expected to provide clues to 3D velocity structures that could feed back into full seismic inversion for an iterative practical and truly cooperative inversion process. We anticipate that, with the aid of parallel computing, cooperative inversion of seismic and magnetotelluric data can be fully automated, and we hold confidence that significant and practical advances in this direction have been accomplished.

Bayesian inversion analysis of nonlinear dynamics in surface heterogeneous reactions.

PubMed

Omori, Toshiaki; Kuwatani, Tatsu; Okamoto, Atsushi; Hukushima, Koji

2016-09-01

It is essential to extract nonlinear dynamics from time-series data as an inverse problem in natural sciences. We propose a Bayesian statistical framework for extracting nonlinear dynamics of surface heterogeneous reactions from sparse and noisy observable data. Surface heterogeneous reactions are chemical reactions with conjugation of multiple phases, and they have the intrinsic nonlinearity of their dynamics caused by the effect of surface-area between different phases. We adapt a belief propagation method and an expectation-maximization (EM) algorithm to partial observation problem, in order to simultaneously estimate the time course of hidden variables and the kinetic parameters underlying dynamics. The proposed belief propagation method is performed by using sequential Monte Carlo algorithm in order to estimate nonlinear dynamical system. Using our proposed method, we show that the rate constants of dissolution and precipitation reactions, which are typical examples of surface heterogeneous reactions, as well as the temporal changes of solid reactants and products, were successfully estimated only from the observable temporal changes in the concentration of the dissolved intermediate product.

Reduction of Dynamic Loads in Mine Lifting Installations

NASA Astrophysics Data System (ADS)

Kuznetsov, N. K.; Eliseev, S. V.; Perelygina, A. Yu

2018-01-01

Article is devoted to a problem of decrease in the dynamic loadings arising in transitional operating modes of the mine lifting installations leading to heavy oscillating motions of lifting vessels and decrease in efficiency and reliability of work. The known methods and means of decrease in dynamic loadings and oscillating motions of the similar equipment are analysed. It is shown that an approach based on the concept of the inverse problems of dynamics can be effective method of the solution of this problem. The article describes the design model of a one-ended lifting installation in the form of a two-mass oscillation system, in which the inertial elements are the mass of the lifting vessel and the reduced mass of the engine, reducer, drum and pulley. The simplified mathematical model of this system and results of an efficiency research of an active way of reduction of dynamic loadings of lifting installation on the basis of the concept of the inverse problems of dynamics are given.

Preview-Based Stable-Inversion for Output Tracking

NASA Technical Reports Server (NTRS)

Zou, Qing-Ze; Devasia, Santosh

1999-01-01

Stable Inversion techniques can be used to achieve high-accuracy output tracking. However, for nonminimum phase systems, the inverse is non-causal - hence the inverse has to be pre-computed using a pre-specified desired-output trajectory. This requirement for pre-specification of the desired output restricts the use of inversion-based approaches to trajectory planning problems (for nonminimum phase systems). In the present article, it is shown that preview information of the desired output can be used to achieve online inversion-based output tracking of linear systems. The amount of preview-time needed is quantified in terms of the tracking error and the internal dynamics of the system (zeros of the system). The methodology is applied to the online output tracking of a flexible structure and experimental results are presented.

Operational Dynamic Configuration Analysis

NASA Technical Reports Server (NTRS)

Lai, Chok Fung; Zelinski, Shannon

2010-01-01

Sectors may combine or split within areas of specialization in response to changing traffic patterns. This method of managing capacity and controller workload could be made more flexible by dynamically modifying sector boundaries. Much work has been done on methods for dynamically creating new sector boundaries [1-5]. Many assessments of dynamic configuration methods assume the current day baseline configuration remains fixed [6-7]. A challenging question is how to select a dynamic configuration baseline to assess potential benefits of proposed dynamic configuration concepts. Bloem used operational sector reconfigurations as a baseline [8]. The main difficulty is that operational reconfiguration data is noisy. Reconfigurations often occur frequently to accommodate staff training or breaks, or to complete a more complicated reconfiguration through a rapid sequence of simpler reconfigurations. Gupta quantified a few aspects of airspace boundary changes from this data [9]. Most of these metrics are unique to sector combining operations and not applicable to more flexible dynamic configuration concepts. To better understand what sort of reconfigurations are acceptable or beneficial, more configuration change metrics should be developed and their distribution in current practice should be computed. This paper proposes a method to select a simple sequence of configurations among operational configurations to serve as a dynamic configuration baseline for future dynamic configuration concept assessments. New configuration change metrics are applied to the operational data to establish current day thresholds for these metrics. These thresholds are then corroborated, refined, or dismissed based on airspace practitioner feedback. The dynamic configuration baseline selection method uses a k-means clustering algorithm to select the sequence of configurations and trigger times from a given day of operational sector combination data. The clustering algorithm selects a simplified schedule containing k configurations based on stability score of the sector combinations among the raw operational configurations. In addition, the number of the selected configurations is determined based on balance between accuracy and assessment complexity.

Disk brake design for cooling improvement using Computational Fluid Dynamics (CFD)

NASA Astrophysics Data System (ADS)

Munisamy, Kannan M.; Shafik, Ramel

2013-06-01

The car disk brake design is improved with two different blade designs compared to the baseline blade design. The two designs were simulated in Computational fluid dynamics (CFD) to obtain heat transfer properties such as Nusselt number and Heat transfer coefficient. The heat transfer property is compared against the baseline design. The improved shape has the highest heat transfer performance. The curved design is inferior to baseline design in heat transfer performance.

The inverse skin effect in the Z-pinch and plasma focus

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

Usenko, P. L., E-mail: otd4@expd.vniief.ru; Gaganov, V. V.

The inverse skin effect and its influence on the dynamics of high-current Z-pinch and plasma focus discharges in deuterium are analyzed. It is shown that the second compression responsible for the major fraction of the neutron yield can be interpreted as a result of the inverse skin effect resulting in the axial concentration of the longitudinal current density and the appearance of a reversed current in the outer layers of plasma pinches. Possible conditions leading to the enhancement of the inverse skin effect and accessible for experimental verification by modern diagnostics are formulated.

Broadband Structural Dynamics: Understanding the Impulse-Response of Structures Across Multiple Length and Time Scales

DTIC Science & Technology

2010-08-18

Spectral domain response calculated • Time domain response obtained through inverse transform Approach 4: WASABI Wavelet Analysis of Structural Anomalies...differences at unity scale! Time Function Transform Apply Spectral Domain Transfer Function Time Function Inverse Transform Transform Transform  mtP

Real-Time Wing-Vortex and Pressure Distribution Estimation on Wings Via Displacements and Strains in Unsteady and Transitional Flight Conditions

DTIC Science & Technology

2016-09-07

approach in co simulation with fluid-dynamics solvers is used. An original variational formulation is developed for the inverse problem of...by the inverse solution meshing. The same approach is used to map the structural and fluid interface kinematics and loads during the fluid structure...co-simulation. The inverse analysis is verified by reconstructing the deformed solution obtained with a corresponding direct formulation, based on

Quantifying shallow subsurface water and heat dynamics using coupled hydrological-thermal-geophysical inversion

DOE PAGES

Tran, Anh Phuong; Dafflon, Baptiste; Hubbard, Susan S.; ...

2016-04-25

Improving our ability to estimate the parameters that control water and heat fluxes in the shallow subsurface is particularly important due to their strong control on recharge, evaporation and biogeochemical processes. The objectives of this study are to develop and test a new inversion scheme to simultaneously estimate subsurface hydrological, thermal and petrophysical parameters using hydrological, thermal and electrical resistivity tomography (ERT) data. The inversion scheme-which is based on a nonisothermal, multiphase hydrological model-provides the desired subsurface property estimates in high spatiotemporal resolution. A particularly novel aspect of the inversion scheme is the explicit incorporation of the dependence of themore » subsurface electrical resistivity on both moisture and temperature. The scheme was applied to synthetic case studies, as well as to real datasets that were autonomously collected at a biogeochemical field study site in Rifle, Colorado. At the Rifle site, the coupled hydrological-thermal-geophysical inversion approach well predicted the matric potential, temperature and apparent resistivity with the Nash-Sutcliffe efficiency criterion greater than 0.92. Synthetic studies found that neglecting the subsurface temperature variability, and its effect on the electrical resistivity in the hydrogeophysical inversion, may lead to an incorrect estimation of the hydrological parameters. The approach is expected to be especially useful for the increasing number of studies that are taking advantage of autonomously collected ERT and soil measurements to explore complex terrestrial system dynamics.« less

Newly proposed proton-abstraction roundabout with backside attack mechanism for the SN2 reaction at the nitrogen center in F- + NH2Cl.

PubMed

Li, Yongfang; Wang, Dunyou

2018-05-07

Recent studies have improved our understanding of the mechanism and dynamics of the bimolecular nucleophilic substitution (S N 2) reaction at the carbon center. Nonetheless, the S N 2 reaction at the nitrogen center has received scarce attention and is less understood. Herein, we propose a new reaction mechanism for the S N 2 reaction at the nitrogen center in the F - + NH 2 Cl reaction using ab initio molecular dynamics calculations. The newly proposed mechanism involves the rotation of NHCl with one proton of NH 2 Cl abstracted by the nucleophile, followed by the classical backside-attack process. The double-inversion mechanism revealed recently for the S N 2 reaction at the carbon center is also observed for the title reaction at the nitrogen center. In contrast to the F - + CH 3 Cl reaction with a proton abstraction-induced first inversion transition state, the F - + NH 2 Cl reaction is a hydrogen bond-induced inversion. This newly proposed reaction mechanism opens a reaction channel to avoid the proton abstraction mechanism at low collision energy. The double-inversion mechanism of the title reaction with a negative first-inversion transition relative to the energy of the reactants is expected to have larger contribution to the reaction rate than the F - + CH 3 Cl reaction with a positive first-inversion transition state.

Urinary potassium excretion and risk of cardiovascular events.

PubMed

Kieneker, Lyanne M; Gansevoort, Ron T; de Boer, Rudolf A; Brouwers, Frank P; Feskens, Edith Jm; Geleijnse, Johanna M; Navis, Gerjan; Bakker, Stephan Jl; Joosten, Michel M

2016-05-01

Observational studies on dietary potassium and risk of cardiovascular disease (CVD) have reported weak-to-modest inverse associations. Long-term prospective studies with multiple 24-h urinary samples for accurate estimation of habitual potassium intake, however, are scarce. We examined the association between urinary potassium excretion and risk of blood pressure-related cardiovascular outcomes. We studied 7795 subjects free of cardiovascular events at baseline in the Prevention of Renal and Vascular End-stage Disease study, a prospective, observational cohort with oversampling of subjects with albuminuria at baseline. Main cardiovascular outcomes were CVD [including ischemic heart disease (IHD), stroke, and vascular interventions], IHD, stroke, and new-onset heart failure (HF). Potassium excretion was measured in two 24-h urine specimens at the start of the study (1997-1998) and midway through follow-up (2001-2003). Baseline median urinary potassium excretion was 70 mmol/24 h (IQR: 56-84 mmol/24 h). During a median follow-up of 10.5 y (IQR: 9.9-10.8 y), a total of 641 CVD, 465 IHD, 172 stroke, and 265 HF events occurred. After adjustment for age and sex, inverse associations were observed between potassium excretion and risk [HR per each 26-mmol/24-h (1-g/d) increase; 95% CI] of CVD (0.87; 0.78, 0.97) and IHD (0.86; 0.75, 0.97), as well as nonsignificant inverse associations for risk of stroke (0.85; 0.68, 1.06) and HF (0.94; 0.80, 1.10). After further adjustment for body mass index, smoking, alcohol consumption, education, and urinary sodium and magnesium excretion, urinary potassium excretion was not statistically significantly associated with risk (multivariable-adjusted HR per 1-g/d increment; 95% CI) of CVD (0.96; 0.85, 1.09), IHD (0.90; 0.81, 1.04), stroke (1.09; 0.86, 1.39), or HF (0.99; 0.83, 1.18). No associations were observed between the sodium-to-potassium excretion ratio and risk of CVD, IHD, stroke, or HF. In this cohort with oversampling of subjects with albuminuria at baseline, urinary potassium excretion was not independently associated with a lower risk of cardiovascular events. © 2016 American Society for Nutrition.

Coupled land surface–subsurface hydrogeophysical inverse modeling to estimate soil organic carbon content and explore associated hydrological and thermal dynamics in the Arctic tundra

DOE PAGES

Tran, Anh Phuong; Dafflon, Baptiste; Hubbard, Susan S.

2017-09-06

Quantitative characterization of soil organic carbon (OC) content is essential due to its significant impacts on surface–subsurface hydrological–thermal processes and microbial decomposition of OC, which both in turn are important for predicting carbon–climate feedbacks. While such quantification is particularly important in the vulnerable organic-rich Arctic region, it is challenging to achieve due to the general limitations of conventional core sampling and analysis methods, and to the extremely dynamic nature of hydrological–thermal processes associated with annual freeze–thaw events. In this study, we develop and test an inversion scheme that can flexibly use single or multiple datasets – including soil liquid watermore » content, temperature and electrical resistivity tomography (ERT) data – to estimate the vertical distribution of OC content. Our approach relies on the fact that OC content strongly influences soil hydrological–thermal parameters and, therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. We employ the Community Land Model to simulate nonisothermal surface–subsurface hydrological dynamics from the bedrock to the top of canopy, with consideration of land surface processes (e.g., solar radiation balance, evapotranspiration, snow accumulation and melting) and ice–liquid water phase transitions. For inversion, we combine a deterministic and an adaptive Markov chain Monte Carlo (MCMC) optimization algorithm to estimate a posteriori distributions of desired model parameters. For hydrological–thermal-to-geophysical variable transformation, the simulated subsurface temperature, liquid water content and ice content are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using different numerical experiments and evaluate the influence of measurement errors and benefit of joint inversion on the estimation of OC and other parameters. We also quantify the propagation of uncertainty from the estimated parameters to prediction of hydrological–thermal responses. We find that, compared to inversion of single dataset (temperature, liquid water content or apparent resistivity), joint inversion of these datasets significantly reduces parameter uncertainty. We find that the joint inversion approach is able to estimate OC and sand content within the shallow active layer (top 0.3 m of soil) with high reliability. Due to the small variations of temperature and moisture within the shallow permafrost (here at about 0.6 m depth), the approach is unable to estimate OC with confidence. However, if the soil porosity is functionally related to the OC and mineral content, which is often observed in organic-rich Arctic soil, the uncertainty of OC estimate at this depth remarkably decreases. Our study documents the value of the new surface–subsurface, deterministic–stochastic inversion approach, as well as the benefit of including multiple types of data to estimate OC and associated hydrological–thermal dynamics.« less

Coupled land surface–subsurface hydrogeophysical inverse modeling to estimate soil organic carbon content and explore associated hydrological and thermal dynamics in the Arctic tundra

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

Tran, Anh Phuong; Dafflon, Baptiste; Hubbard, Susan S.

Quantitative characterization of soil organic carbon (OC) content is essential due to its significant impacts on surface–subsurface hydrological–thermal processes and microbial decomposition of OC, which both in turn are important for predicting carbon–climate feedbacks. While such quantification is particularly important in the vulnerable organic-rich Arctic region, it is challenging to achieve due to the general limitations of conventional core sampling and analysis methods, and to the extremely dynamic nature of hydrological–thermal processes associated with annual freeze–thaw events. In this study, we develop and test an inversion scheme that can flexibly use single or multiple datasets – including soil liquid watermore » content, temperature and electrical resistivity tomography (ERT) data – to estimate the vertical distribution of OC content. Our approach relies on the fact that OC content strongly influences soil hydrological–thermal parameters and, therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. We employ the Community Land Model to simulate nonisothermal surface–subsurface hydrological dynamics from the bedrock to the top of canopy, with consideration of land surface processes (e.g., solar radiation balance, evapotranspiration, snow accumulation and melting) and ice–liquid water phase transitions. For inversion, we combine a deterministic and an adaptive Markov chain Monte Carlo (MCMC) optimization algorithm to estimate a posteriori distributions of desired model parameters. For hydrological–thermal-to-geophysical variable transformation, the simulated subsurface temperature, liquid water content and ice content are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using different numerical experiments and evaluate the influence of measurement errors and benefit of joint inversion on the estimation of OC and other parameters. We also quantify the propagation of uncertainty from the estimated parameters to prediction of hydrological–thermal responses. We find that, compared to inversion of single dataset (temperature, liquid water content or apparent resistivity), joint inversion of these datasets significantly reduces parameter uncertainty. We find that the joint inversion approach is able to estimate OC and sand content within the shallow active layer (top 0.3 m of soil) with high reliability. Due to the small variations of temperature and moisture within the shallow permafrost (here at about 0.6 m depth), the approach is unable to estimate OC with confidence. However, if the soil porosity is functionally related to the OC and mineral content, which is often observed in organic-rich Arctic soil, the uncertainty of OC estimate at this depth remarkably decreases. Our study documents the value of the new surface–subsurface, deterministic–stochastic inversion approach, as well as the benefit of including multiple types of data to estimate OC and associated hydrological–thermal dynamics.« less

Toeplitz Inverse Covariance-Based Clustering of Multivariate Time Series Data

PubMed Central

Hallac, David; Vare, Sagar; Boyd, Stephen; Leskovec, Jure

2018-01-01

Subsequence clustering of multivariate time series is a useful tool for discovering repeated patterns in temporal data. Once these patterns have been discovered, seemingly complicated datasets can be interpreted as a temporal sequence of only a small number of states, or clusters. For example, raw sensor data from a fitness-tracking application can be expressed as a timeline of a select few actions (i.e., walking, sitting, running). However, discovering these patterns is challenging because it requires simultaneous segmentation and clustering of the time series. Furthermore, interpreting the resulting clusters is difficult, especially when the data is high-dimensional. Here we propose a new method of model-based clustering, which we call Toeplitz Inverse Covariance-based Clustering (TICC). Each cluster in the TICC method is defined by a correlation network, or Markov random field (MRF), characterizing the interdependencies between different observations in a typical subsequence of that cluster. Based on this graphical representation, TICC simultaneously segments and clusters the time series data. We solve the TICC problem through alternating minimization, using a variation of the expectation maximization (EM) algorithm. We derive closed-form solutions to efficiently solve the two resulting subproblems in a scalable way, through dynamic programming and the alternating direction method of multipliers (ADMM), respectively. We validate our approach by comparing TICC to several state-of-the-art baselines in a series of synthetic experiments, and we then demonstrate on an automobile sensor dataset how TICC can be used to learn interpretable clusters in real-world scenarios. PMID:29770257

An Inverse Problem for a Class of Conditional Probability Measure-Dependent Evolution Equations

PubMed Central

Mirzaev, Inom; Byrne, Erin C.; Bortz, David M.

2016-01-01

We investigate the inverse problem of identifying a conditional probability measure in measure-dependent evolution equations arising in size-structured population modeling. We formulate the inverse problem as a least squares problem for the probability measure estimation. Using the Prohorov metric framework, we prove existence and consistency of the least squares estimates and outline a discretization scheme for approximating a conditional probability measure. For this scheme, we prove general method stability. The work is motivated by Partial Differential Equation (PDE) models of flocculation for which the shape of the post-fragmentation conditional probability measure greatly impacts the solution dynamics. To illustrate our methodology, we apply the theory to a particular PDE model that arises in the study of population dynamics for flocculating bacterial aggregates in suspension, and provide numerical evidence for the utility of the approach. PMID:28316360

A Lie-Theoretic Perspective on O(n) Mass Matrix Inversion for Serial Manipulators and Polypeptide Chains.

PubMed

Lee, Kiju; Wang, Yunfeng; Chirikjian, Gregory S

2007-11-01

Over the past several decades a number of O(n) methods for forward and inverse dynamics computations have been developed in the multi-body dynamics and robotics literature. A method was developed in 1974 by Fixman for O(n) computation of the mass-matrix determinant for a serial polymer chain consisting of point masses. In other recent papers, we extended this method in order to compute the inverse of the mass matrix for serial chains consisting of point masses. In the present paper, we extend these ideas further and address the case of serial chains composed of rigid-bodies. This requires the use of relatively deep mathematics associated with the rotation group, SO(3), and the special Euclidean group, SE(3), and specifically, it requires that one differentiates functions of Lie-group-valued argument.

Inverse load calculation procedure for offshore wind turbines and application to a 5-MW wind turbine support structure: Inverse load calculation procedure for offshore wind turbines

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

Pahn, T.; Rolfes, R.; Jonkman, J.

A significant number of wind turbines installed today have reached their designed service life of 20 years, and the number will rise continuously. Most of these turbines promise a more economical performance if they operate for more than 20 years. To assess a continued operation, we have to analyze the load-bearing capacity of the support structure with respect to site-specific conditions. Such an analysis requires the comparison of the loads used for the design of the support structure with the actual loads experienced. This publication presents the application of a so-called inverse load calculation to a 5-MW wind turbine supportmore » structure. The inverse load calculation determines external loads derived from a mechanical description of the support structure and from measured structural responses. Using numerical simulations with the software fast, we investigated the influence of wind-turbine-specific effects such as the wind turbine control or the dynamic interaction between the loads and the support structure to the presented inverse load calculation procedure. fast is used to study the inverse calculation of simultaneously acting wind and wave loads, which has not been carried out until now. Furthermore, the application of the inverse load calculation procedure to a real 5-MW wind turbine support structure is demonstrated. In terms of this practical application, setting up the mechanical system for the support structure using measurement data is discussed. The paper presents results for defined load cases and assesses the accuracy of the inversely derived dynamic loads for both the simulations and the practical application.« less

Low-moderate urine arsenic and biomarkers of thrombosis and inflammation in the Strong Heart Study.

PubMed

Moon, Katherine A; Navas-Acien, Ana; Grau-Pérez, Maria; Francesconi, Kevin A; Goessler, Walter; Guallar, Eliseo; Umans, Jason G; Best, Lyle G; Newman, Jonathan D

2017-01-01

The underlying pathology of arsenic-related cardiovascular disease (CVD) is unknown. Few studies have evaluated pathways through thrombosis and inflammation for arsenic-related CVD, especially at low-moderate arsenic exposure levels (<100 μg/L in drinking water). We evaluated the association of chronic low-moderate arsenic exposure, measured as the sum of inorganic and methylated arsenic species in urine (ΣAs), with plasma biomarkers of thrombosis and inflammation in American Indian adults (45-74 years) in the Strong Heart Study. We evaluated the cross-sectional and longitudinal associations between baseline ΣAs with fibrinogen at three visits (baseline, 1989-91; Visit 2, 1993-95, Visit 3, 1998-99) using mixed models and the associations between baseline ΣAs and Visit 2 plasminogen activator inhibitor-1 (PAI-1) and high sensitivity C-reactive protein (hsCRP) using linear regression. Median (interquartile range) concentrations of baseline ΣAs and fibrinogen, and Visit 2 hsCRP and PAI-1 were 8.4 (5.1, 14.3) μg/g creatinine, 346 (304, 393) mg/dL, 44 (30, 67) mg/L, and 3.8 (2.0, 7.0) ng/mL, respectively. Comparing the difference between the 75th and the 25th percentile of ΣAs (14.3 vs. 5.1 μg/g creatinine), ΣAs was positively associated with baseline fibrinogen among those with diabetes (adjusted geometric mean ratio (GMR): 1.05, 95% CI: 1.02, 1.07) not associated among those without diabetes (GMR: 1.01, 95% CI: 0.99, 1.02) (p-interaction for diabetes = 0.014), inversely associated with PAI-1 (GMR: 0.94, 95% CI: 0.90, 0.99), and not associated with hsCRP (GMR: 1.00, 95% CI: 0.93, 1.08). We found no evidence for an association between baseline ΣAs and annual change in fibrinogen over follow-up (p-interaction = 0.28 and 0.12 for diabetes and non-diabetes, respectively). Low-moderate arsenic exposure was positively associated with baseline fibrinogen in participants with diabetes and unexpectedly inversely associated with PAI-1. Further research should evaluate the role of prothrombotic factors in arsenic-related cardiovascular disease.

NASA Space Geodesy Program: GSFC data analysis, 1992. Crustal Dynamics Project VLBI geodetic results, 1979 - 1991

NASA Technical Reports Server (NTRS)

Ryan, J. W.; Ma, C.; Caprette, D. S.

1993-01-01

The Goddard VLBI group reports the results of analyzing 1648 Mark 3 data sets acquired from fixed and mobile observing sites through the end of 1991, and available to the Crustal Dynamics Project. Two large solutions were used to obtain Earth rotation parameters, nutation offsets, radio source positions, site positions, site velocities, and baseline evolution. Site positions are tabulated on a yearly basis for 1979 to 1995, inclusive. Site velocities are presented in both geocentric Cartesian and topocentric coordinates. Baseline evolution is plotted for 200 baselines, and individual length determinations are presented for an additional 356 baselines. This report includes 155 quasar radio sources, 96 fixed stations and mobile sites, and 556 baselines.

Facile fabrication of highly controllable gating systems based on the combination of inverse opal structure and dynamic covalent chemistry.

PubMed

Wang, Chen; Yang, Haowei; Tian, Li; Wang, Shiqiang; Gao, Ning; Zhang, Wanlin; Wang, Peng; Yin, Xianpeng; Li, Guangtao

2017-06-01

A three-dimensional (3D) inverse opal with periodic and porous structures has shown great potential for applications not only in optics and optoelectronics, but also in functional membranes. In this work, the benzaldehyde group was initially introduced into a 3D nanoporous inverse opal, serving as a platform for fabricating functional membranes. By employing the dynamic covalent approach, a highly controllable gating system was facilely fabricated to achieve modulable and reversible transport features. It was found that the physical/chemical properties and pore size of the gating system could easily be regulated through post-modification with amines. As a demonstration, the gated nanopores were modified with three kinds of amines to control the wettability, surface charge and nanopore size which in turn was exploited to achieve selective mass transport, including hydrophobic molecules, cations and anions, and the transport with respect to the physical steric hindrance. In particular, the gating system showed extraordinary reversibility and could recover to its pristine state by simply changing pH values. Due to the unlimited variety provided by the Schiff base reaction, the inverse opal described here exhibits a significant extendibility and could be easily post-modified with stimuli-responsive molecules for special purposes. Furthermore, this work can be extended to employ other dynamic covalent routes, for example Diels-Alder, ester exchange and disulfide exchange-based routes.

A Scalable O(N) Algorithm for Large-Scale Parallel First-Principles Molecular Dynamics Simulations

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

Osei-Kuffuor, Daniel; Fattebert, Jean-Luc

2014-01-01

Traditional algorithms for first-principles molecular dynamics (FPMD) simulations only gain a modest capability increase from current petascale computers, due to their O(N 3) complexity and their heavy use of global communications. To address this issue, we are developing a truly scalable O(N) complexity FPMD algorithm, based on density functional theory (DFT), which avoids global communications. The computational model uses a general nonorthogonal orbital formulation for the DFT energy functional, which requires knowledge of selected elements of the inverse of the associated overlap matrix. We present a scalable algorithm for approximately computing selected entries of the inverse of the overlap matrix,more » based on an approximate inverse technique, by inverting local blocks corresponding to principal submatrices of the global overlap matrix. The new FPMD algorithm exploits sparsity and uses nearest neighbor communication to provide a computational scheme capable of extreme scalability. Accuracy is controlled by the mesh spacing of the finite difference discretization, the size of the localization regions in which the electronic orbitals are confined, and a cutoff beyond which the entries of the overlap matrix can be omitted when computing selected entries of its inverse. We demonstrate the algorithm's excellent parallel scaling for up to O(100K) atoms on O(100K) processors, with a wall-clock time of O(1) minute per molecular dynamics time step.« less

Recursive Factorization of the Inverse Overlap Matrix in Linear-Scaling Quantum Molecular Dynamics Simulations.

PubMed

Negre, Christian F A; Mniszewski, Susan M; Cawkwell, Marc J; Bock, Nicolas; Wall, Michael E; Niklasson, Anders M N

2016-07-12

We present a reduced complexity algorithm to compute the inverse overlap factors required to solve the generalized eigenvalue problem in a quantum-based molecular dynamics (MD) simulation. Our method is based on the recursive, iterative refinement of an initial guess of Z (inverse square root of the overlap matrix S). The initial guess of Z is obtained beforehand by using either an approximate divide-and-conquer technique or dynamical methods, propagated within an extended Lagrangian dynamics from previous MD time steps. With this formulation, we achieve long-term stability and energy conservation even under the incomplete, approximate, iterative refinement of Z. Linear-scaling performance is obtained using numerically thresholded sparse matrix algebra based on the ELLPACK-R sparse matrix data format, which also enables efficient shared-memory parallelization. As we show in this article using self-consistent density-functional-based tight-binding MD, our approach is faster than conventional methods based on the diagonalization of overlap matrix S for systems as small as a few hundred atoms, substantially accelerating quantum-based simulations even for molecular structures of intermediate size. For a 4158-atom water-solvated polyalanine system, we find an average speedup factor of 122 for the computation of Z in each MD step.

Recursive Factorization of the Inverse Overlap Matrix in Linear Scaling Quantum Molecular Dynamics Simulations

DOE PAGES

Negre, Christian F. A; Mniszewski, Susan M.; Cawkwell, Marc Jon; ...

2016-06-06

We present a reduced complexity algorithm to compute the inverse overlap factors required to solve the generalized eigenvalue problem in a quantum-based molecular dynamics (MD) simulation. Our method is based on the recursive iterative re nement of an initial guess Z of the inverse overlap matrix S. The initial guess of Z is obtained beforehand either by using an approximate divide and conquer technique or dynamically, propagated within an extended Lagrangian dynamics from previous MD time steps. With this formulation, we achieve long-term stability and energy conservation even under incomplete approximate iterative re nement of Z. Linear scaling performance ismore » obtained using numerically thresholded sparse matrix algebra based on the ELLPACK-R sparse matrix data format, which also enables e cient shared memory parallelization. As we show in this article using selfconsistent density functional based tight-binding MD, our approach is faster than conventional methods based on the direct diagonalization of the overlap matrix S for systems as small as a few hundred atoms, substantially accelerating quantum-based simulations even for molecular structures of intermediate size. For a 4,158 atom water-solvated polyalanine system we nd an average speedup factor of 122 for the computation of Z in each MD step.« less

Restart Operator Meta-heuristics for a Problem-Oriented Evolutionary Strategies Algorithm in Inverse Mathematical MISO Modelling Problem Solving

NASA Astrophysics Data System (ADS)

Ryzhikov, I. S.; Semenkin, E. S.

2017-02-01

This study is focused on solving an inverse mathematical modelling problem for dynamical systems based on observation data and control inputs. The mathematical model is being searched in the form of a linear differential equation, which determines the system with multiple inputs and a single output, and a vector of the initial point coordinates. The described problem is complex and multimodal and for this reason the proposed evolutionary-based optimization technique, which is oriented on a dynamical system identification problem, was applied. To improve its performance an algorithm restart operator was implemented.

Inverse cascades and resonant triads in rotating and stratified turbulence

NASA Astrophysics Data System (ADS)

Oks, D.; Mininni, P. D.; Marino, R.; Pouquet, A.

2017-11-01

Kraichnan's seminal ideas on inverse cascades yielded new tools to study common phenomena in geophysical turbulent flows. In the atmosphere and the oceans, rotation and stratification result in a flow that can be approximated as two-dimensional at very large scales but which requires considering three-dimensional effects to fully describe turbulent transport processes and non-linear phenomena. Motions can thus be classified into two classes: fast modes consisting of inertia-gravity waves and slow quasi-geostrophic modes for which the Coriolis force and horizontal pressure gradients are close to balance. In this paper, we review previous results on the strength of the inverse cascade in rotating and stratified flows and then present new results on the effect of varying the strength of rotation and stratification (measured by the inverse Prandtl ratio N/f, of the Coriolis frequency to the Brunt-Väisäla frequency) on the amplitude of the waves and on the flow quasi-geostrophic behavior. We show that the inverse cascade is more efficient in the range of N/f for which resonant triads do not exist, 1 /2 ≤N /f ≤2 . We then use the spatio-temporal spectrum to show that in this range slow modes dominate the dynamics, while the strength of the waves (and their relevance in the flow dynamics) is weaker.

An inverse dynamics approach to face animation.

PubMed

Pitermann, M; Munhall, K G

2001-09-01

Muscle-based models of the human face produce high quality animation but rely on recorded muscle activity signals or synthetic muscle signals that are often derived by trial and error. This paper presents a dynamic inversion of a muscle-based model (Lucero and Munhall, 1999) that permits the animation to be created from kinematic recordings of facial movements. Using a nonlinear optimizer (Powell's algorithm), the inversion produces a muscle activity set for seven muscles in the lower face that minimize the root mean square error between kinematic data recorded with OPTOTRAK and the corresponding nodes of the modeled facial mesh. This inverted muscle activity is then used to animate the facial model. In three tests of the inversion, strong correlations were observed for kinematics produced from synthetic muscle activity, for OPTOTRAK kinematics recorded from a talker for whom the facial model is morphologically adapted and finally for another talker with the model morphology adapted to a different individual. The correspondence between the animation kinematics and the three-dimensional OPTOTRAK data are very good and the animation is of high quality. Because the kinematic to electromyography (EMG) inversion is ill posed, there is no relation between the actual EMG and the inverted EMG. The overall redundancy of the motor system means that many different EMG patterns can produce the same kinematic output.

Vacancy-Induced Formation and Growth of Inversion Domains in Transition-Metal Dichalcogenide Monolayer

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

Lin, Junhao; Pantelides, Sokrates T.; Zhou, Wu

2015-04-23

Sixty degree grain boundaries in semiconducting transition-metal dichalcogenide (TMDC) monolayers have been shown to act as conductive channels that have profound influence on both the transport properties and exciton behavior of the monolayers. We show that annealing TMDC monolayers at high temperature induces the formation of large-scale inversion domains surrounded by such 60° grain boundaries. To study the formation mechanism of such inversion domains, we use the electron beam in a scanning transmission electron microscope to activate the dynamic process within pristine TMDC monolayers. Moreover, the electron beam acts to generate chalcogen vacancies in TMDC monolayers and provide energy formore » them to undergo structural evolution. We directly visualize the nucleation and growth of such inversion domains and their 60° grain boundaries atom-by-atom within a MoSe 2 monolayer and explore their formation mechanism. Combined with density functional theory, we conclude that the nucleation of the inversion domains and migration of their 60° grain boundaries are driven by the collective evolution of Se vacancies and subsequent displacement of Mo atoms, where such a dynamical process reduces the vacancy-induced lattice shrinkage and stabilizes the system. Our results can help to understand the performance of such materials under severe conditions (e.g., high temperature).« less

Hybrid Adaptive Flight Control with Model Inversion Adaptation

NASA Technical Reports Server (NTRS)

Nguyen, Nhan

2011-01-01

This study investigates a hybrid adaptive flight control method as a design possibility for a flight control system that can enable an effective adaptation strategy to deal with off-nominal flight conditions. The hybrid adaptive control blends both direct and indirect adaptive control in a model inversion flight control architecture. The blending of both direct and indirect adaptive control provides a much more flexible and effective adaptive flight control architecture than that with either direct or indirect adaptive control alone. The indirect adaptive control is used to update the model inversion controller by an on-line parameter estimation of uncertain plant dynamics based on two methods. The first parameter estimation method is an indirect adaptive law based on the Lyapunov theory, and the second method is a recursive least-squares indirect adaptive law. The model inversion controller is therefore made to adapt to changes in the plant dynamics due to uncertainty. As a result, the modeling error is reduced that directly leads to a decrease in the tracking error. In conjunction with the indirect adaptive control that updates the model inversion controller, a direct adaptive control is implemented as an augmented command to further reduce any residual tracking error that is not entirely eliminated by the indirect adaptive control.

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.

Crustal dynamics project data analysis, 1991: VLBI geodetic results, 1979 - 1990

NASA Technical Reports Server (NTRS)

Ma, C.; Ryan, J. W.; Caprette, D. S.

1992-01-01

The Goddard VLBI group reports the results of analyzing 1412 Mark II data sets acquired from fixed and mobile observing sites through the end of 1990 and available to the Crustal Dynamics Project. Three large solutions were used to obtain Earth rotation parameters, nutation offsets, global source positions, site velocities, and baseline evolution. Site positions are tabulated on a yearly basis from 1979 through 1992. Site velocities are presented in both geocentric Cartesian coordinates and topocentric coordinates. Baseline evolution is plotted for 175 baselines. Rates are computed for earth rotation and nutation parameters. Included are 104 sources, 88 fixed stations and mobile sites, and 688 baselines.

Tuning Fractures With Dynamic Data

NASA Astrophysics Data System (ADS)

Yao, Mengbi; Chang, Haibin; Li, Xiang; Zhang, Dongxiao

2018-02-01

Flow in fractured porous media is crucial for production of oil/gas reservoirs and exploitation of geothermal energy. Flow behaviors in such media are mainly dictated by the distribution of fractures. Measuring and inferring the distribution of fractures is subject to large uncertainty, which, in turn, leads to great uncertainty in the prediction of flow behaviors. Inverse modeling with dynamic data may assist to constrain fracture distributions, thus reducing the uncertainty of flow prediction. However, inverse modeling for flow in fractured reservoirs is challenging, owing to the discrete and non-Gaussian distribution of fractures, as well as strong nonlinearity in the relationship between flow responses and model parameters. In this work, building upon a series of recent advances, an inverse modeling approach is proposed to efficiently update the flow model to match the dynamic data while retaining geological realism in the distribution of fractures. In the approach, the Hough-transform method is employed to parameterize non-Gaussian fracture fields with continuous parameter fields, thus rendering desirable properties required by many inverse modeling methods. In addition, a recently developed forward simulation method, the embedded discrete fracture method (EDFM), is utilized to model the fractures. The EDFM maintains computational efficiency while preserving the ability to capture the geometrical details of fractures because the matrix is discretized as structured grid, while the fractures being handled as planes are inserted into the matrix grids. The combination of Hough representation of fractures with the EDFM makes it possible to tune the fractures (through updating their existence, location, orientation, length, and other properties) without requiring either unstructured grids or regridding during updating. Such a treatment is amenable to numerous inverse modeling approaches, such as the iterative inverse modeling method employed in this study, which is capable of dealing with strongly nonlinear problems. A series of numerical case studies with increasing complexity are set up to examine the performance of the proposed approach.

Coupled Land Surface-Subsurface Hydrogeophysical Inverse Modeling to Estimate Soil Organic Carbon Content in an Arctic Tundra

NASA Astrophysics Data System (ADS)

Tran, A. P.; Dafflon, B.; Hubbard, S.

2017-12-01

Soil organic carbon (SOC) is crucial for predicting carbon climate feedbacks in the vulnerable organic-rich Arctic region. However, it is challenging to achieve this property due to the general limitations of conventional core sampling and analysis methods. In this study, we develop an inversion scheme that uses single or multiple datasets, including soil liquid water content, temperature and ERT data, to estimate the vertical profile of SOC content. Our approach relies on the fact that SOC content strongly influences soil hydrological-thermal parameters, and therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. The scheme includes several advantages. First, this is the first time SOC content is estimated by using a coupled hydrogeophysical inversion. Second, by using the Community Land Model, we can account for the land surface dynamics (evapotranspiration, snow accumulation and melting) and ice/liquid phase transition. Third, we combine a deterministic and an adaptive Markov chain Monte Carlo optimization algorithm to better estimate the posterior distributions of desired model parameters. Finally, the simulated subsurface variables are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using synthetic experiments. The results show that compared to inversion of single dataset, joint inversion of these datasets significantly reduces parameter uncertainty. The joint inversion approach is able to estimate SOC content within the shallow active layer with high reliability. Next, we apply the scheme to estimate OC content along an intensive ERT transect in Barrow, Alaska using multiple datasets acquired in the 2013-2015 period. The preliminary results show a good agreement between modeled and measured soil temperature, thaw layer thickness and electrical resistivity. The accuracy of estimated SOC content will be evaluated by comparison with measurements from soil samples along the transect. Our study presents a new surface-subsurface, deterministic-stochastic hydrogeophysical inversion approach, as well as the benefit of including multiple types of data to estimate SOC and associated hydrological-thermal dynamics.

Dynamics of Genome Rearrangement in Bacterial Populations

PubMed Central

Darling, Aaron E.; Miklós, István; Ragan, Mark A.

2008-01-01

Genome structure variation has profound impacts on phenotype in organisms ranging from microbes to humans, yet little is known about how natural selection acts on genome arrangement. Pathogenic bacteria such as Yersinia pestis, which causes bubonic and pneumonic plague, often exhibit a high degree of genomic rearrangement. The recent availability of several Yersinia genomes offers an unprecedented opportunity to study the evolution of genome structure and arrangement. We introduce a set of statistical methods to study patterns of rearrangement in circular chromosomes and apply them to the Yersinia. We constructed a multiple alignment of eight Yersinia genomes using Mauve software to identify 78 conserved segments that are internally free from genome rearrangement. Based on the alignment, we applied Bayesian statistical methods to infer the phylogenetic inversion history of Yersinia. The sampling of genome arrangement reconstructions contains seven parsimonious tree topologies, each having different histories of 79 inversions. Topologies with a greater number of inversions also exist, but were sampled less frequently. The inversion phylogenies agree with results suggested by SNP patterns. We then analyzed reconstructed inversion histories to identify patterns of rearrangement. We confirm an over-representation of “symmetric inversions”—inversions with endpoints that are equally distant from the origin of chromosomal replication. Ancestral genome arrangements demonstrate moderate preference for replichore balance in Yersinia. We found that all inversions are shorter than expected under a neutral model, whereas inversions acting within a single replichore are much shorter than expected. We also found evidence for a canonical configuration of the origin and terminus of replication. Finally, breakpoint reuse analysis reveals that inversions with endpoints proximal to the origin of DNA replication are nearly three times more frequent. Our findings represent the first characterization of genome arrangement evolution in a bacterial population evolving outside laboratory conditions. Insight into the process of genomic rearrangement may further the understanding of pathogen population dynamics and selection on the architecture of circular bacterial chromosomes. PMID:18650965

Comparison of Antarctic Crustal Thickness from Gravity Inversion and Seismology: Evidence for Mantle Dynamic Uplift under Marie Byrd Land

NASA Astrophysics Data System (ADS)

Ferraccioli, F.; Kusznir, N. J.; Jordan, T. A.

2017-12-01

Using gravity anomaly inversion, we produce comprehensive regional maps of crustal thickness and oceanic lithosphere distribution for Antarctica and the Southern Ocean. Antarctic crustal thicknesses derived from gravity inversion are compared with seismic estimates from Baranov (2011) and An et al. (2015). We determine Moho depth, crustal basement thickness, continental lithosphere thinning (1-1/) and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir 2008). Data used in the gravity inversion are elevation and bathymetry, free-air gravity anomaly, the Bedmap 2 ice thickness and bedrock topography compilation south of 60 degrees south and relatively sparse constraints on sediment thickness. Our gravity inversion study predicts thick crust (> 45 km) under interior East Antarctica, which is penetrated by narrow continental rifts featuring relatively thinner crust. The largest crustal thicknesses predicted from gravity inversion lie in the region of the Gamburtsev Subglacial Mountains, and are consistent with seismic estimates. The East Antarctic Rift System (EARS), a major Permian to Cretaceous age rift system, is imaged by our inversion and appears to extend from the continental margin at the Lambert Rift (LR) to the South Pole region, a distance of 2500 km. Thin crust is predicted under the Ross Sea and beneath the West Antarctic Ice Sheet and delineates the regional extent of the broad West Antarctic Rift System (WARS). Substantial regional uplift is required under Marie Byrd Land to reconcile gravity and seismic estimates. A mantle dynamic uplift origin of the uplift is preferred to a thermal anomaly from a very young rift. The new crustal thickness map produced by this gravity inversion study support the hypothesis that one branch of the WARS links through to the De Gerlache sea-mounts (DG) and Peter I Island (PI) in the Bellingshausen Sea region, while another branch may link to the George V Sound Rift in the Antarctic Peninsula region.

Neural network based adaptive control for nonlinear dynamic regimes

NASA Astrophysics Data System (ADS)

Shin, Yoonghyun

Adaptive control designs using neural networks (NNs) based on dynamic inversion are investigated for aerospace vehicles which are operated at highly nonlinear dynamic regimes. NNs play a key role as the principal element of adaptation to approximately cancel the effect of inversion error, which subsequently improves robustness to parametric uncertainty and unmodeled dynamics in nonlinear regimes. An adaptive control scheme previously named 'composite model reference adaptive control' is further developed so that it can be applied to multi-input multi-output output feedback dynamic inversion. It can have adaptive elements in both the dynamic compensator (linear controller) part and/or in the conventional adaptive controller part, also utilizing state estimation information for NN adaptation. This methodology has more flexibility and thus hopefully greater potential than conventional adaptive designs for adaptive flight control in highly nonlinear flight regimes. The stability of the control system is proved through Lyapunov theorems, and validated with simulations. The control designs in this thesis also include the use of 'pseudo-control hedging' techniques which are introduced to prevent the NNs from attempting to adapt to various actuation nonlinearities such as actuator position and rate saturations. Control allocation is introduced for the case of redundant control effectors including thrust vectoring nozzles. A thorough comparison study of conventional and NN-based adaptive designs for a system under a limit cycle, wing-rock, is included in this research, and the NN-based adaptive control designs demonstrate their performances for two highly maneuverable aerial vehicles, NASA F-15 ACTIVE and FQM-117B unmanned aerial vehicle (UAV), operated under various nonlinearities and uncertainties.

Transitionless driving on adiabatic search algorithm

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

Oh, Sangchul, E-mail: soh@qf.org.qa; Kais, Sabre, E-mail: kais@purdue.edu; Department of Chemistry, Department of Physics and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907

We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian,more » approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics.« less

A Lie-Theoretic Perspective on O(n) Mass Matrix Inversion for Serial Manipulators and Polypeptide Chains

PubMed Central

Lee, Kiju; Wang, Yunfeng; Chirikjian, Gregory S.

2010-01-01

Over the past several decades a number of O(n) methods for forward and inverse dynamics computations have been developed in the multi-body dynamics and robotics literature. A method was developed in 1974 by Fixman for O(n) computation of the mass-matrix determinant for a serial polymer chain consisting of point masses. In other recent papers, we extended this method in order to compute the inverse of the mass matrix for serial chains consisting of point masses. In the present paper, we extend these ideas further and address the case of serial chains composed of rigid-bodies. This requires the use of relatively deep mathematics associated with the rotation group, SO(3), and the special Euclidean group, SE(3), and specifically, it requires that one differentiates functions of Lie-group-valued argument. PMID:20165563

Deformation measurement for a rotating deformable lap based on inverse fringe projection

NASA Astrophysics Data System (ADS)

Liao, Min; Zhang, Qican

2015-03-01

The active deformable lap (also namely stressed lap) is an efficient polishing tool in optical manufacturing. To measure the dynamic deformation caused by outside force on a deformable lap is important and helpful to the opticians to ensure the performance of a deformable lap as expected. In this paper, a manual deformable lap was designed to simulate the dynamic deformation of an active stressed lap, and a measurement system was developed based on inverse projected fringe technique to restore the 3D shape. A redesigned inverse fringe has been projected onto the surface of the measured lap, and the deformations of the tested lap become much obvious and can be easily and quickly evaluated by Fourier fringe analysis. Compared with the conventional projection, this technique is more obvious, and it should be a promising one in the deformation measurement of the active stressed lap in optical manufacturing.

Catalytic-site design for inverse heavy-enzyme isotope effects in human purine nucleoside phosphorylase

PubMed Central

Harijan, Rajesh K.; Zoi, Ioanna; Antoniou, Dimitri; Schwartz, Steven D.; Schramm, Vern L.

2017-01-01

Heavy-enzyme isotope effects (15N-, 13C-, and 2H-labeled protein) explore mass-dependent vibrational modes linked to catalysis. Transition path-sampling (TPS) calculations have predicted femtosecond dynamic coupling at the catalytic site of human purine nucleoside phosphorylase (PNP). Coupling is observed in heavy PNPs, where slowed barrier crossing caused a normal heavy-enzyme isotope effect (kchem light/kchem heavy > 1.0). We used TPS to design mutant F159Y PNP, predicted to improve barrier crossing for heavy F159Y PNP, an attempt to generate a rare inverse heavy-enzyme isotope effect (kchem light/kchem heavy < 1.0). Steady-state kinetic comparison of light and heavy native PNPs to light and heavy F159Y PNPs revealed similar kinetic properties. Pre–steady-state chemistry was slowed 32-fold in F159Y PNP. Pre–steady-state chemistry compared heavy and light native and F159Y PNPs and found a normal heavy-enzyme isotope effect of 1.31 for native PNP and an inverse effect of 0.75 for F159Y PNP. Increased isotopic mass in F159Y PNP causes more efficient transition state formation. Independent validation of the inverse isotope effect for heavy F159Y PNP came from commitment to catalysis experiments. Most heavy enzymes demonstrate normal heavy-enzyme isotope effects, and F159Y PNP is a rare example of an inverse effect. Crystal structures and TPS dynamics of native and F159Y PNPs explore the catalytic-site geometry associated with these catalytic changes. Experimental validation of TPS predictions for barrier crossing establishes the connection of rapid protein dynamics and vibrational coupling to enzymatic transition state passage. PMID:28584087

SURFACE FLUID REGISTRATION OF CONFORMAL REPRESENTATION: APPLICATION TO DETECT DISEASE BURDEN AND GENETIC INFLUENCE ON HIPPOCAMPUS

PubMed Central

Shi, Jie; Thompson, Paul M.; Gutman, Boris; Wang, Yalin

2013-01-01

In this paper, we develop a new automated surface registration system based on surface conformal parameterization by holomorphic 1-forms, inverse consistentsurface fluid registration, and multivariate tensor-based morphometry (mTBM). First, we conformally map a surface onto a planar rectangle space with holomorphic 1-forms. Second, we compute surface conformal representation by combining its local conformal factor and mean curvature and linearly scale the dynamic range of the conformal representation to form the feature image of the surface. Third, we align the feature image with a chosen template image via the fluid image registration algorithm, which has been extended into the curvilinear coordinates to adjust for the distortion introduced by surface parameterization. The inverse consistent image registration algorithm is also incorporated in the system to jointly estimate the forward and inverse transformations between the study and template images. This alignment induces a corresponding deformation on the surface. We tested the system on Alzheimer's Disease Neuroimaging Initiative (ADNI) baseline dataset to study AD symptoms on hippocampus. In our system, by modeling a hippocampus as a 3D parametric surface, we nonlinearly registered each surface with a selected template surface. Then we used mTBM to analyze the morphometrydifference between diagnostic groups. Experimental results show that the new system has better performance than two publically available subcortical surface registration tools: FIRST and SPHARM. We also analyzed the genetic influence of the Apolipoprotein E ε4 allele (ApoE4),which is considered as the most prevalent risk factor for AD.Our work successfully detected statistically significant difference between ApoE4 carriers and non-carriers in both patients of mild cognitive impairment (MCI) and healthy control subjects. The results show evidence that the ApoE genotype may be associated with accelerated brain atrophy so that our workprovides a new MRI analysis tool that may help presymptomatic AD research. PMID:23587689

A baseline for upper crustal velocity variations along the East Pacific Rise at 13 deg N

NASA Astrophysics Data System (ADS)

Kappus, Mary E.; Harding, Alistair J.; Orcutt, John A.

1995-04-01

A wide aperture profile of the East Pacific Rise at 13 deg N provides data necessary to make a high-resolution seismic velocity profile of the uppermost crust along a 52-km segment of ridge crest. Automated and objective processing steps, including r-p analysis and waveform inversion, allow the construction of models in a consistent way so that comparisons are meaningful. A continuous profile is synthesized from 70 independent one-dimensional models spaced at 750-km intervals along the ridge. The resulting seismic velocity structure of the top 500 m of crust is remarkable in its lack of variability. The main features are a thin low-velocity layer 2A at the top with a steep gradient to layer 2B. The seafloor velocity is nearly constant at 2.45 km/s +/- 3% along the entire ridge. The velocity at the top of layer 2B is 5.0 km/s +/- 10%. The depth to the 4 km/s isovelocity contour within layer 2A is 130 +/- 20 m from 13 deg to 13 deg 20 min N, north of which it increases to 180 m. The increase in thickness is coincident with a deviation from axial linearity (DEVAL) noted by both a slight change in axis depth and orientation and in geochemistry. The waveform inversion, providing more details plus velocity gradient information, shows a layer 2A with about 80 m of constant-velocity material underlain by 150 m of high velocity gradient material, putting the base of layer 2A at approximately 230 m depth south of 13 deg 20 min N and about 50 m thicker north of the DEVAL. The overall lack of variability, combined with other recent measurements of layer 2A thickness along and near the axis, indicates that the thickness of volcanic extrusives is controlled not by levels of volcanic productivity, but the dynamics of emplacement. The homogeneity along axis also provides a baseline of inherent variability in crustal structure of about 10% against which other observed variations in similar regimes can be compared.

Plasma prolactin and homovanillic acid as markers for psychopathology and abnormal movements after neuroleptic dose decrease.

PubMed

Newcomer, J W; Riney, S J; Vinogradov, S; Csernansky, J G

1992-01-01

Plasma prolactin concentration (pPRL), plasma homovanillic acid concentration (pHVA), and symptomatology were measured in 24 male subjects with schizophrenia during maintenance haloperidol treatment. Fourteen subjects subsequently underwent 50 percent dose decreases under placebo-controlled, double-blind conditions. At baseline, a significant inverse correlation was found between pPRL and both tardive dyskinesia (TD) and "thinking disorder"; pPRL was directly correlated with negative symptoms. No such relationship was found with pHVA. In the patients who underwent a dose decrease, no relationship was found between baseline pPRL or pHVA and any clinical variable after the decrease. These data do not support the use of baseline pPRL or pHVA as markers of central dopamine function subsequent to a neuroleptic dose decrease.

Super-resolution Time-Lapse Seismic Waveform Inversion

NASA Astrophysics Data System (ADS)

Ovcharenko, O.; Kazei, V.; Peter, D. B.; Alkhalifah, T.

2017-12-01

Time-lapse seismic waveform inversion is a technique, which allows tracking changes in the reservoirs over time. Such monitoring is relatively computationally extensive and therefore it is barely feasible to perform it on-the-fly. Most of the expenses are related to numerous FWI iterations at high temporal frequencies, which is inevitable since the low-frequency components can not resolve fine scale features of a velocity model. Inverted velocity changes are also blurred when there is noise in the data, so the problem of low-resolution images is widely known. One of the problems intensively tackled by computer vision research community is the recovering of high-resolution images having their low-resolution versions. Usage of artificial neural networks to reach super-resolution from a single downsampled image is one of the leading solutions for this problem. Each pixel of the upscaled image is affected by all the pixels of its low-resolution version, which enables the workflow to recover features that are likely to occur in the corresponding environment. In the present work, we adopt machine learning image enhancement technique to improve the resolution of time-lapse full-waveform inversion. We first invert the baseline model with conventional FWI. Then we run a few iterations of FWI on a set of the monitoring data to find desired model changes. These changes are blurred and we enhance their resolution by using a deep neural network. The network is trained to map low-resolution model updates predicted by FWI into the real perturbations of the baseline model. For supervised training of the network we generate a set of random perturbations in the baseline model and perform FWI on the noisy data from the perturbed models. We test the approach on a realistic perturbation of Marmousi II model and demonstrate that it outperforms conventional convolution-based deblurring techniques.

Chocolate consumption and risk of diabetes mellitus in the Physicians’ Health Study1234

PubMed Central

Petrone, Andrew B; Sesso, Howard D; Gaziano, J Michael; Djoussé, Luc

2015-01-01

Background: Previous studies reported beneficial effects of cocoa or chocolate on insulin resistance, oxidative stress, and inflammation, which are important risk factors of type 2 diabetes mellitus (DM). However, it is unclear whether chocolate consumption is associated with risk of DM. Objective: We tested the hypothesis that chocolate consumption is inversely associated with incident DM in the Physicians’ Health Study (PHS). Design: We prospectively analyzed data on 18,235 PHS participants who were free of DM at baseline (1997–2001). Chocolate consumption was obtained from a baseline food-frequency questionnaire. Incident DM was ascertained via annual follow-up questionnaires and validated in a subsample by a review of medical records. We used Cox proportional hazards models to estimate HRs and 95% CIs of DM. Results: The mean (±SD) age at baseline was 66.3 ± 9.2 y. During a mean follow up of 9.2 y, 1123 men (6.2%) developed DM. For self-reported chocolate consumption of none, 1–3 servings/mo, 1 serving/wk, and ≥2 servings/wk, multivariable-adjusted HRs (95% CIs) of DM adjusted for lifestyle, clinical, and dietary risk factors including total energy intake were 1.00 (referent), 0.93 (0.79, 1.09), 0.86 (0.72, 1.04), and 0.83 (0.69, 0.99), respectively (P-trend = 0.047). In secondary analyses, the inverse association of chocolate consumption and risk of DM was slightly stronger in subjects without a history of cardiovascular disease or heart failure (P-trend = 0.023). In addition, both age and BMI modified the chocolate-DM relation (P < 0.05 each). Conclusion: Our data support an inverse relation of chocolate intake with incident DM, which appears only to apply in younger and normal–body weight men after controlling for comprehensive life styles including total energy consumption. PMID:25646334

Adiponectin and catecholamine concentrations during acute exercise in children with type 1 diabetes.

PubMed

2008-06-01

Adiponectin, an adipokine secreted by the adipocyte, is inversely related to adiposity and directly related to insulin sensitivity. In type 1 diabetes mellitus (T1DM), however, data thus far are contradictory. We investigated the relationship between adiponectin and exercise inT1DM. Forty-nine children (14.5 +/- 2.0 yr, range 8-17 yr) with T1DM on an insulin pump were studied during two 75-min exercise sessions with and without continuation of the basal rate within 4 wk. Adiponectin and epinephrine concentrations were measured before and during exercise. Mean preexercise adiponectin concentration was 11.2 +/- 4.7 mg/L (range 2.7-23.0 mg/L) with a mean absolute difference of 1.7 mg/L between the 2 d. Adiponectin concentrations did not change meaningfully during exercise (mean change: -0.1 +/- 1.2 mg/L; p = 0.17). Adiponectin correlated inversely with body mass index percentile (p = 0.02) but not with age, gender, duration of diabetes, hemoglobin A1c, or preexercise glucose. However, those with higher baseline adiponectin concentrations were less likely to become hypoglycemic during exercise, 36% becoming hypoglycemic when baseline adiponectin concentration was <10 mg/L, 42% when 10 to <15 mg/L, and 15% when > or =15 mg/L (p = 0.02). Baseline epinephrine concentrations were not associated with adiponectin, and in those whose nadir glucose was < or =100 mg/dL, there was no correlation between epinephrine response and adiponectin (p = 0.16). Adiponectin concentrations are stable from day to day, are not affected by acute exercise or metabolic control, and vary inversely with adiposity. Higher adiponectin concentration appears to be associated with a decrease in hypoglycemia risk during exercise. Further studies are needed to examine whether adiponectin protects against exercise-induced hypoglycemia by directly enhancing the oxidation of alternate fuels.

Chocolate consumption and risk of diabetes mellitus in the Physicians' Health Study.

PubMed

Matsumoto, Chisa; Petrone, Andrew B; Sesso, Howard D; Gaziano, J Michael; Djoussé, Luc

2015-02-01

Previous studies reported beneficial effects of cocoa or chocolate on insulin resistance, oxidative stress, and inflammation, which are important risk factors of type 2 diabetes mellitus (DM). However, it is unclear whether chocolate consumption is associated with risk of DM. We tested the hypothesis that chocolate consumption is inversely associated with incident DM in the Physicians' Health Study (PHS). We prospectively analyzed data on 18,235 PHS participants who were free of DM at baseline (1997-2001). Chocolate consumption was obtained from a baseline food-frequency questionnaire. Incident DM was ascertained via annual follow-up questionnaires and validated in a subsample by a review of medical records. We used Cox proportional hazards models to estimate HRs and 95% CIs of DM. The mean (±SD) age at baseline was 66.3 ± 9.2 y. During a mean follow up of 9.2 y, 1123 men (6.2%) developed DM. For self-reported chocolate consumption of none, 1-3 servings/mo, 1 serving/wk, and ≥2 servings/wk, multivariable-adjusted HRs (95% CIs) of DM adjusted for lifestyle, clinical, and dietary risk factors including total energy intake were 1.00 (referent), 0.93 (0.79, 1.09), 0.86 (0.72, 1.04), and 0.83 (0.69, 0.99), respectively (P-trend = 0.047). In secondary analyses, the inverse association of chocolate consumption and risk of DM was slightly stronger in subjects without a history of cardiovascular disease or heart failure (P-trend = 0.023). In addition, both age and BMI modified the chocolate-DM relation (P < 0.05 each). Our data support an inverse relation of chocolate intake with incident DM, which appears only to apply in younger and normal-body weight men after controlling for comprehensive life styles including total energy consumption. © 2015 American Society for Nutrition.

Interparental Relationship Dynamics and Cardiac Vagal Functioning in Infancy

PubMed Central

Graham, Alice M.; Ablow, Jennifer C.; Measelle, Jeffrey R.

2010-01-01

This study examined associations between interparental relationship dynamics and vagus system functioning in infancy. The functioning of the vagus system, part of the parasympathetic nervous system, indexes emotional reactivity and regulation. Interparental avoidance and dyadic adjustment constitute the focus of this study in order to bring attention to relationship dynamics not subsumed under overt conflict. Infants’ baseline vagal tone and change in vagal tone in response to a novel toy were assessed at five months in a sample of high-risk mother-infant dyads (n = 77). Maternal report of interparental avoidance demonstrated an association with infants’ baseline vagal tone, while interparental dyadic adjustment was associated with change in infants’ vagal tone from baseline to the novel toy. Infant gender moderated these associations. Maternal sensitivity did not mediate interparental relationship dynamics and infants’ vagal functioning. Results are discussed in the context of emotional security theory. PMID:20727595

Time-lapse joint inversion of geophysical data with automatic joint constraints and dynamic attributes

NASA Astrophysics Data System (ADS)

Rittgers, J. B.; Revil, A.; Mooney, M. A.; Karaoulis, M.; Wodajo, L.; Hickey, C. J.

2016-12-01

Joint inversion and time-lapse inversion techniques of geophysical data are often implemented in an attempt to improve imaging of complex subsurface structures and dynamic processes by minimizing negative effects of random and uncorrelated spatial and temporal noise in the data. We focus on the structural cross-gradient (SCG) approach (enforcing recovered models to exhibit similar spatial structures) in combination with time-lapse inversion constraints applied to surface-based electrical resistivity and seismic traveltime refraction data. The combination of both techniques is justified by the underlying petrophysical models. We investigate the benefits and trade-offs of SCG and time-lapse constraints. Using a synthetic case study, we show that a combined joint time-lapse inversion approach provides an overall improvement in final recovered models. Additionally, we introduce a new approach to reweighting SCG constraints based on an iteratively updated normalized ratio of model sensitivity distributions at each time-step. We refer to the new technique as the Automatic Joint Constraints (AJC) approach. The relevance of the new joint time-lapse inversion process is demonstrated on the synthetic example. Then, these approaches are applied to real time-lapse monitoring field data collected during a quarter-scale earthen embankment induced-piping failure test. The use of time-lapse joint inversion is justified by the fact that a change of porosity drives concomitant changes in seismic velocities (through its effect on the bulk and shear moduli) and resistivities (through its influence upon the formation factor). Combined with the definition of attributes (i.e. specific characteristics) of the evolving target associated with piping, our approach allows localizing the position of the preferential flow path associated with internal erosion. This is not the case using other approaches.

Diets high in total antioxidant capacity improve risk biomarkers of cardiovascular disease: a 9-month observational study among overweight/obese postmenopausal women.

PubMed

Wang, Ying; Yang, Meng; Lee, Sang-Gil; Davis, Catherine G; Koo, Sung I; Fernandez, Maria Luz; Volek, Jeff S; Chun, Ock K

2014-09-01

Previous studies have shown that total antioxidant capacity (TAC) of typical diets is associated with higher plasma TAC and antioxidant enzyme activities. At present, however, little is known for the association between dietary TAC and inflammatory biomarkers. The present study was designed to examine the association between dietary TAC and inflammatory biomarkers in a group of overweight/obese postmenopausal women, a population with high cardiovascular disease (CVD) risk, during a 9-month period. Thirty-five postmenopausal, overweight or obese, but apparently healthy women aged 40-70 years were recruited for a 9-month observational study. Seven-day food records and 12-h fasting blood samples were collected at baseline and at the end of the study for dietary and plasma biomarker assessments. Dietary TAC was calculated theoretically for taking account of both diet and dietary supplements, and energy-adjusted values were obtained using residual method. At baseline, subjects consuming diets with high dietary TAC had lower levels of plasma C-reactive protein (CRP) and monocyte chemoattractant protein-1 (p < 0.05) compared with those with low dietary TAC. Over the 9-month period, change in dietary TAC had a negative partial correlation with plasma CRP levels (p < 0.01) when age, ethnicity, and changes in BMI, blood total cholesterol and triglyceride were adjusted. Findings suggest that consumption of diets high in TAC are inversely associated with plasma CRP levels cross-sectionally and dynamically and may contribute to CVD protection.

Application of the concept of dynamic trim control and nonlinear system inverses to automatic control of a vertical attitude takeoff and landing aircraft

NASA Technical Reports Server (NTRS)

Smith, G. A.; Meyer, G.

1981-01-01

A full envelope automatic flight control system based on nonlinear inverse systems concepts has been applied to a vertical attitude takeoff and landing (VATOL) fighter aircraft. A new method for using an airborne digital aircraft model to perform the inversion of a nonlinear aircraft model is presented together with the results of a simulation study of the nonlinear inverse system concept for the vertical-attitude hover mode. The system response to maneuver commands in the vertical attitude was found to be excellent; and recovery from large initial offsets and large disturbances was found to be very satisfactory.

Impact of heart rate variability, a marker for cardiac health, on lupus disease activity.

PubMed

Thanou, Aikaterini; Stavrakis, Stavros; Dyer, John W; Munroe, Melissa E; James, Judith A; Merrill, Joan T

2016-09-02

Decreased heart rate variability (HRV) is associated with adverse outcomes in cardiovascular diseases and has been observed in patients with systemic lupus erythematosus (SLE). We examined the relationship of HRV with SLE disease activity and selected cytokine pathways. Fifty-three patients from the Oklahoma Lupus Cohort were evaluated at two visits each. Clinical assessments included the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), British Isles Lupus Assessment Group (BILAG) index, physician global assessment (PGA), and Safety of Estrogens in Lupus Erythematosus National Assessment-SLEDAI Flare Index. HRV was assessed with a 5-minute electrocardiogram, and the following HRV parameters were calculated: square root of the mean of the squares of differences between adjacent NN intervals (RMSSD), percentage of pairs of adjacent NN intervals differing by more than 50 milliseconds (pNN50), high-frequency power (HF power), and low frequency to high frequency (LF/HF) ratio, which reflects sympathetic/vagal balance. Plasma cytokine levels were measured with a multiplex, bead-based immunoassay. Serum B lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL) were measured with an enzyme-linked immunosorbent assay. Linear regression analysis was applied. Baseline HRV (pNN50, HF power, LF/HF ratio) was inversely related to disease activity (BILAG, PGA) and flare. Changes in RMSSD between visits were inversely related to changes in SLEDAI (p = 0.007). Age, caffeine, tobacco and medication use had no impact on HRV. Plasma soluble tumor necrosis factor receptor II (sTNFRII) and monokine induced by interferon gamma (MIG) were inversely related with all baseline measures of HRV (p = 0.039 to <0.001). Plasma stem cell factor (SCF), interleukin (IL)-1 receptor antagonist (IL-1RA), and IL-15 showed similar inverse relationships with baseline HRV, and weaker trends were observed for interferon (IFN)-α, interferon gamma-induced protein (IP)-10, and serum BLyS. Changes in the LF/HF ratio between visits were also associated with changes in sTNFRII (p = 0.021), MIG (p = 0.003), IFN-α (p = 0.012), SCF (p = 0.001), IL-1RA (p = 0.023), and IL-15 (p = 0.010). On the basis of multivariate linear regression, MIG was an independent predictor of baseline HRV after adjusting for plasma IL-1RA, SCF, IFN-α, IP-10, and serum BLyS. In a similar model, the sTNFRII impact remained significant after adjusting for the same variables. Impaired HRV, particularly the LF/HF ratio, is associated with lupus disease activity and several cytokines related to IFN type II and TNF pathways. The strongest association was with MIG and sTNFRII, expanding previous immune connections of vagal signaling.

Comparison of Serum Cytokine Levels in Men Who are Obese or Men Who are Lean: Effects of Nonlinear Periodized Resistance Training and Obesity.

PubMed

Nikseresht, Mahmoud

2018-06-01

Nikseresht, M. Comparison of serum cytokine levels in men who are obese or men who are lean: effects of nonlinear periodized resistance training and obesity. J Strength Cond Res 32(6): 1787-1795, 2018-This study examined the capacity of nonlinear resistance training (NRT) to alter some cytokines and markers of insulin resistance in men who are obese. An additional aim was to compare these variables between men who are obese and men who are lean. Age- and fitness-matched men who are obese were randomly allocated to NRT (n = 12) and control (CON, n = 10) groups. An age- and fitness-matched control group of lean men (n = 11) were also recruited for baseline comparison. The NRT (12 weeks, 3 d·wk, 5-11 exercises) performed at different intensities (40-95% of 1 repetition maximum) with flexible periodization. Serum insulin, glucose, interleukin (IL)-6, IL-10, IL-17A, and IL-20 levels were measured at baseline and after training. Men who were obese had significantly lower IL-20 and higher glucose, insulin, insulin resistance (homeostasis model assessment, HOMA-IR), IL-10, and IL-6 than lean participants at baseline (all, p ≤ 0.05). There were significant negative correlations between IL-10 with anthropometric markers and HOMA-IR at baseline, whereas these variables were inversely correlated with IL-20. After training, V[Combining Dot Above]O2peak and 1 repetition maximum for bench press and knee extension of the NRT increased significantly compared with CON, which was accompanied by significant reductions in anthropometric markers, insulin and HOMA-IR. IL-6 and IL-17A did not change significantly in response to training, but IL-10 and IL-20 increased significantly compared with baseline. An inverse relationship between the percent IL-20 increase and the percent waist circumference decrease suggests that adipocytes, or other metabolic factors such as glucose, may exert a lowering-effect on IL-20.

Inverse Correlation between the Atrial Fibrillatory Rate and the Ventricular Repolarization Time: Observations at Baseline and after an Intravenous Infusion of a Combined Potassium and Sodium Current Blocker.

PubMed

Edvardsson, Nils; Aunes, Maria; Frison, Lars; Berggren, Anders R

2016-05-01

The atrial fibrillatory rate (AFR) and the ventricular rate and repolarization (QTcF) were studied at baseline and under the influence of the combined potassium and sodium current blocker AZD7009. Ninety-two patients with atrial fibrillation (AF) were randomized to an intravenous infusion of AZD7009 or placebo. The atrial fibrillatory activity in lead V1 was extracted using spatiotemporal QRST cancellation. The exponential decay (ED) characterized the degree of atrial signal organization. The mean (SD) AFR at baseline was 396  ±  57 (range 253-584) and 410 ± 33 (range 363-469) bpm in patients randomized to AZD7009 and placebo, respectively. The AFR decreased within the first minutes of the AZD7009 infusion and reached its minimum of 235 ± 34 bpm after 18 minutes. On placebo, the AFR was unchanged. On AZD7009, the ED decreased from 1.2 ± 0.3 to reach its lowest level at 0.7 ± 0.2 after 14 minutes. The ventricular rate did not change significantly over time. The AFR was statistically significantly related to the ventricular repolarization at baseline, the QTcF being longer at lower AFR values, and this relationship remained during and after AZD7009. In the full multivariate linear regression model, including age, sex, left ventricular ejection fraction, QRS duration, heart rate, QTcF, AF episode duration, AF history duration, and right atrial or left atrial size, only QTcF and age were statistically significantly correlated with the AFR. The correlation remained when the uncorrected QT interval was used. The QTcF was inversely correlated with AFR, both at baseline and during administration of AZD7009. The AFR was not correlated with the ventricular rate. © 2015 Wiley Periodicals, Inc.

The role of leptin and other hormones related to bone metabolism and appetite regulation as determinants of gain in body fat and fat-free mass in 8-11-year-old children.

PubMed

Dalskov, Stine-Mathilde; Ritz, Christian; Larnkjær, Anni; Damsgaard, Camilla T; Petersen, Rikke A; Sørensen, Louise B; Ong, Ken K; Astrup, Arne; Mølgaard, Christian; Michaelsen, Kim F

2015-03-01

Regulation of body composition during childhood is complex. Numerous hormones are potentially involved. Leptin has been proposed to restrain weight gain, but results are inconsistent. We examined whether baseline fasting levels of ghrelin, adiponectin, leptin, insulin, IGF-I, osteocalcin, and intact parathyroid hormone (iPTH) were associated with body composition cross sectionally and longitudinally in 633 8-11-year-olds. Data on hormones and body composition by dual-energy x-ray absorptiometry from the OPUS School Meal Study were used. We looked at baseline hormones as predictors of baseline fat mass index (FMI) or fat-free mass index (FFMI), and also subsequent changes (3 and 6 months) in FMI or FFMI using models with hormones individually or combined. Cross-sectionally, baseline leptin was positively associated with FMI in girls (0.211 kg/m(2) pr. μg/mL; 97.5% confidence interval [CI],0.186-0.236; P < .001) and boys (0.231 kg/m(2) pr. μg/mL; 97.5% CI, 0.200-0.261; P < .001). IGF-I in both sexes and iPTH in boys were positively associated with FMI. An inverse association between adiponectin and FFMI in boys and a positive association between IGF-I and FFMI were found in girls. In longitudinal models, baseline leptin was inversely associated with subsequent changes in FMI (-0.018 kg/m(2) pr. μg/mL; 97.5% CI, -0.034 - -0.002; P = .028) and FFMI (-0.014 kg/m(2) pr. μg/mL; 97.5% CI, -0.024 - -0.003; P = .006) in girls. Cross-sectional findings support that leptin is produced in proportion to body fat mass, but the longitudinal observations support that leptin inhibits gains in FMI and FFMI in girls, a finding that may reflect preserved leptin sensitivity in this predominantly normal weight population.

NT-proBNP and Heart Failure Risk Among Individuals With and Without Obesity: The ARIC Study

PubMed Central

Ndumele, Chiadi E.; Matsushita, Kunihiro; Sang, Yingying; Lazo, Mariana; Agarwal, Sunil K.; Nambi, Vijay; Deswal, Anita; Blumenthal, Roger S.; Ballantyne, Christie M.; Coresh, Josef; Selvin, Elizabeth

2016-01-01

Background Obesity is a risk factor for heart failure (HF), but is associated with lower N-terminal of pro-Brain Natriuretic Peptide (NT-proBNP) levels. It is unclear whether the prognostic value and implications of NT-proBNP levels for HF risk differ across body mass index (BMI) categories. Methods and Results We followed 12,230 ARIC participants free of prior HF at baseline (visit 2, 1990–1992) with BMI ≥18.5 kg/m2. We quantified and compared the relative and absolute risk associations of NT-proBNP with incident HF across BMI categories. There were 1,861 HF events during a median 20.6 years of follow-up. Despite increased HF risk in obesity, a weak inverse association was seen between baseline BMI and NT-proBNP levels (r = −0.10). Nevertheless, higher baseline NT-proBNP was associated with increased HF risk in all BMI categories. NT-proBNP improved HF risk prediction overall and even among those with severe obesity (BMI ≥35 kg/m2; improvement in c-statistic +0.032 [95% CI 0.011–0.053]). However, given higher HF rates among those with obesity, at each NT-proBNP level, higher BMI was associated with greater absolute HF risk. Indeed, among those with NT-proBNP 100 to < 200 pg/ml, the average 10-year HF risk was <5% among normal weight individuals but >10% if severely obese. Conclusions Despite its inverse relationship with BMI, NT-proBNP provides significant prognostic information regarding the risk of developing HF even among individuals with obesity. Given the higher baseline HF risk among persons with obesity, even slight elevations in NT-proBNP may have implications for increased absolute HF risk in this population. PMID:26746175

Inverse Modelling to Obtain Head Movement Controller Signal

NASA Technical Reports Server (NTRS)

Kim, W. S.; Lee, S. H.; Hannaford, B.; Stark, L.

1984-01-01

Experimentally obtained dynamics of time-optimal, horizontal head rotations have previously been simulated by a sixth order, nonlinear model driven by rectangular control signals. Electromyography (EMG) recordings have spects which differ in detail from the theoretical rectangular pulsed control signal. Control signals for time-optimal as well as sub-optimal horizontal head rotations were obtained by means of an inverse modelling procedures. With experimentally measured dynamical data serving as the input, this procedure inverts the model to produce the neurological control signals driving muscles and plant. The relationships between these controller signals, and EMG records should contribute to the understanding of the neurological control of movements.

Rayleigh lidar observation of tropical mesospheric inversion layer: a comparison between dynamics and chemistry

NASA Astrophysics Data System (ADS)

Ramesh, K.; Sridharan, S.; Raghunath, K.

2018-04-01

The Rayleigh lidar at National Atmospheric Research Laboratory, Gadanki (13.5°N, 79.2°E), India operates at 532 nm green laser with 600 mJ/pulse since 2007. The vertical temperature profiles are derived above 30 km by assuming the atmosphere is in hydrostatic equilibrium and obeys ideal gas law. A large mesospheric inversion layer (MIL) is observed at 77.4-84.6 km on the night of 22 March 2007 over Gadanki. Although dynamics and chemistry play vital role, both the mechanisms are compared for the occurrence of the MIL in the present study.

Preparation time influences ankle and knee joint control during dynamic change of direction movements.

PubMed

Fuerst, Patrick; Gollhofer, Albert; Gehring, Dominic

2017-04-01

The influence of preparation time on ankle joint biomechanics during highly dynamic movements is largely unknown. The aim of this study was to evaluate the impact of limited preparation time on ankle joint loading during highly dynamic run-and-cut movements. Thirteen male basketball players performed 45°-sidestep-cutting and 180°-turning manoeuvres in reaction to light signals which appeared during the approach run. Both movements were executed under (1) an easy condition, in which the light signal appeared very early, (2) a medium condition and (3) a hard condition with very little time to prepare the movements. Maximum ankle inversion angles, moments and velocities during ground contact, as well as EMG signals of three lower extremity muscles, were analysed. In 180°-turning movements, reduced preparation time led to significantly increased maximum ankle inversion velocities. Muscular activation levels, however, did not change. Increased inversion velocities, without accompanying changes in muscular activation, may have the potential to destabilise the ankle joint when less preparation time is available. This may result in a higher injury risk during turning movements and should therefore be considered in ankle injury research and the aetiology of ankle sprains.

Discrete Inverse and State Estimation Problems

NASA Astrophysics Data System (ADS)

Wunsch, Carl

2006-06-01

The problems of making inferences about the natural world from noisy observations and imperfect theories occur in almost all scientific disciplines. This book addresses these problems using examples taken from geophysical fluid dynamics. It focuses on discrete formulations, both static and time-varying, known variously as inverse, state estimation or data assimilation problems. Starting with fundamental algebraic and statistical ideas, the book guides the reader through a range of inference tools including the singular value decomposition, Gauss-Markov and minimum variance estimates, Kalman filters and related smoothers, and adjoint (Lagrange multiplier) methods. The final chapters discuss a variety of practical applications to geophysical flow problems. Discrete Inverse and State Estimation Problems is an ideal introduction to the topic for graduate students and researchers in oceanography, meteorology, climate dynamics, and geophysical fluid dynamics. It is also accessible to a wider scientific audience; the only prerequisite is an understanding of linear algebra. Provides a comprehensive introduction to discrete methods of inference from incomplete information Based upon 25 years of practical experience using real data and models Develops sequential and whole-domain analysis methods from simple least-squares Contains many examples and problems, and web-based support through MIT opencourseware

The Effect of Overskilling Dynamics on Wages

ERIC Educational Resources Information Center

Mavromaras, Kostas; Mahuteau, Stephane; Sloane, Peter; Wei, Zhang

2013-01-01

We use a random-effects dynamic probit model to estimate the effect of overskilling dynamics on wages. We find that overskilling mismatch is common and more likely among those who have been overskilled in the past. It is also highly persistent, in a manner that is inversely related to educational level. Yet, the wages of university graduates are…

One bad apple: experimental effects of psychological conflict on social resilience

PubMed Central

Pincus, David

2014-01-01

Past research suggests that small groups are self-organizing systems, and that social resilience may be measured as the meta-flexibility of group dynamics: the ability to shift back and forth from flexiblity to rigidity in response to conflict. This study extends these prior results, examining the impact of experimentally induced internal conflict and group-level conflict resolution on group dynamics—whether one bad apple can spoil the bunch. Six experimental groups with four members each participated in a series of four 25 min discussions. The first two discussions served as a baseline condition. Internal conflict was induced to one or more group members prior to discussion three, with the prediction that higher levels of conflict induction would lead to significant drops in group flexibility—creating a press on the group's resilience, whereas conflict resolution in discussion four was expected to allow for a rebound in group flexibility. Consistent with prior research, the turn-taking dynamics of each the 24 groups were distributed as inverse power laws (R2 = 0.86–0.99) providing evidence for self-organization. Furthermore, there were significant study-wise negative correlation between levels of personality conflict and two measures of flexibility: information entropy (r = −0.47, p = 0.019) and fractal dimension (r = −0.42, p = 0.037). Altogether, these results suggest that: (i) small groups are self-organizing systems with structure and flexibility providing social resilience and (ii) individual conflict is able to spread to higher level social dynamics, creating pressure on social resilience. Practical implications for assessment of, and intervention with, psychosocial resilience are discussed. PMID:25285194

Dark Matter and the elusive Z' in a dynamical Inverse Seesaw scenario

DOE PAGES

De Romeri, Valentina; Fernandez-Martinez, Enrique; Gehrlein, Julia; ...

2017-10-24

The Inverse Seesaw naturally explains the smallness of neutrino masses via an approximate $B-L$ symmetry broken only by a correspondingly small parameter. In this work the possible dynamical generation of the Inverse Seesaw neutrino mass mechanism from the spontaneous breaking of a gauged $U(1)$ $B-L$ symmetry is investigated. Interestingly, the Inverse Seesaw pattern requires a chiral content such that anomaly cancellation predicts the existence of extra fermions belonging to a dark sector with large, non-trivial, charges under the $U(1)$ $B-L$. We investigate the phenomenology associated to these new states and find that one of them is a viable dark mattermore » candidate with mass around the TeV scale, whose interaction with the Standard Model is mediated by the $Z'$ boson associated to the gauged $U(1)$ $B-L$ symmetry. Given the large charges required for anomaly cancellation in the dark sector, the $B-L$ $Z'$ interacts preferentially with this dark sector rather than with the Standard Model. This suppresses the rate at direct detection searches and thus alleviates the constraints on $Z'$-mediated dark matter relic abundance. Furthermore, the collider phenomenology of this elusive $Z'$ is also discussed.« less

Dynamic Shape Reconstruction of Three-Dimensional Frame Structures Using the Inverse Finite Element Method

NASA Technical Reports Server (NTRS)

Gherlone, Marco; Cerracchio, Priscilla; Mattone, Massimiliano; Di Sciuva, Marco; Tessler, Alexander

2011-01-01

A robust and efficient computational method for reconstructing the three-dimensional displacement field of truss, beam, and frame structures, using measured surface-strain data, is presented. Known as shape sensing , this inverse problem has important implications for real-time actuation and control of smart structures, and for monitoring of structural integrity. The present formulation, based on the inverse Finite Element Method (iFEM), uses a least-squares variational principle involving strain measures of Timoshenko theory for stretching, torsion, bending, and transverse shear. Two inverse-frame finite elements are derived using interdependent interpolations whose interior degrees-of-freedom are condensed out at the element level. In addition, relationships between the order of kinematic-element interpolations and the number of required strain gauges are established. As an example problem, a thin-walled, circular cross-section cantilevered beam subjected to harmonic excitations in the presence of structural damping is modeled using iFEM; where, to simulate strain-gauge values and to provide reference displacements, a high-fidelity MSC/NASTRAN shell finite element model is used. Examples of low and high-frequency dynamic motion are analyzed and the solution accuracy examined with respect to various levels of discretization and the number of strain gauges.

Dark Matter and the elusive Z' in a dynamical Inverse Seesaw scenario

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

De Romeri, Valentina; Fernandez-Martinez, Enrique; Gehrlein, Julia

The Inverse Seesaw naturally explains the smallness of neutrino masses via an approximate $B-L$ symmetry broken only by a correspondingly small parameter. In this work the possible dynamical generation of the Inverse Seesaw neutrino mass mechanism from the spontaneous breaking of a gauged $U(1)$ $B-L$ symmetry is investigated. Interestingly, the Inverse Seesaw pattern requires a chiral content such that anomaly cancellation predicts the existence of extra fermions belonging to a dark sector with large, non-trivial, charges under the $U(1)$ $B-L$. We investigate the phenomenology associated to these new states and find that one of them is a viable dark mattermore » candidate with mass around the TeV scale, whose interaction with the Standard Model is mediated by the $Z'$ boson associated to the gauged $U(1)$ $B-L$ symmetry. Given the large charges required for anomaly cancellation in the dark sector, the $B-L$ $Z'$ interacts preferentially with this dark sector rather than with the Standard Model. This suppresses the rate at direct detection searches and thus alleviates the constraints on $Z'$-mediated dark matter relic abundance. Furthermore, the collider phenomenology of this elusive $Z'$ is also discussed.« less

Multi-Sensor Systems Development for UXO Detection and Discrimination: Man-Portable Dual Magnetic/Electromagnetic Induction Sensor

DTIC Science & Technology

2008-02-01

of the magnetic data to constrain the target depth using joint or cooperative inversions ( Pasion et al. 2002). ERDC/EL TR-08-9 24 Figure 15. EM...baseline ordnance classification test site at Blossom Pt. Naval Research Laboratory. NRL/MR/6110-00-8437, March 20, 1998. Pasion , L., S. Billings, and

Force adaptation transfers to untrained workspace regions in children: evidence for developing inverse dynamic motor models.

PubMed

Jansen-Osmann, Petra; Richter, Stefanie; Konczak, Jürgen; Kalveram, Karl-Theodor

2002-03-01

When humans perform goal-directed arm movements under the influence of an external damping force, they learn to adapt to these external dynamics. After removal of the external force field, they reveal kinematic aftereffects that are indicative of a neural controller that still compensates the no longer existing force. Such behavior suggests that the adult human nervous system uses a neural representation of inverse arm dynamics to control upper-extremity motion. Central to the notion of an inverse dynamic model (IDM) is that learning generalizes. Consequently, aftereffects should be observable even in untrained workspace regions. Adults have shown such behavior, but the ontogenetic development of this process remains unclear. This study examines the adaptive behavior of children and investigates whether learning a force field in one hemifield of the right arm workspace has an effect on force adaptation in the other hemifield. Thirty children (aged 6-10 years) and ten adults performed 30 degrees elbow flexion movements under two conditions of external damping (negative and null). We found that learning to compensate an external damping force transferred to the opposite hemifield, which indicates that a model of the limb dynamics rather than an association of visited space and experienced force was acquired. Aftereffects were more pronounced in the younger children and readaptation to a null-force condition was prolonged. This finding is consistent with the view that IDMs in children are imprecise neural representations of the actual arm dynamics. It indicates that the acquisition of IDMs is a developmental achievement and that the human motor system is inherently flexible enough to adapt to any novel force within the limits of the organism's biomechanics.

Baseline modeling of the Owensboro cable-stayed bridge over the Ohio River.

DOT National Transportation Integrated Search

2006-03-01

This report presents the baseline modeling of the Owensboro cable-stayed bridge which connects Owensboro, Kentucky and Rockport, Indiana over the Ohio River. The objective of this study is to establish the bridge baseline model via the dynamics-based...

Estimation of Dynamic Friction Process of the Akatani Landslide Based on the Waveform Inversion and Numerical Simulation

NASA Astrophysics Data System (ADS)

Yamada, M.; Mangeney, A.; Moretti, L.; Matsushi, Y.

2014-12-01

Understanding physical parameters, such as frictional coefficients, velocity change, and dynamic history, is important issue for assessing and managing the risks posed by deep-seated catastrophic landslides. Previously, landslide motion has been inferred qualitatively from topographic changes caused by the event, and occasionally from eyewitness reports. However, these conventional approaches are unable to evaluate source processes and dynamic parameters. In this study, we use broadband seismic recordings to trace the dynamic process of the deep-seated Akatani landslide that occurred on the Kii Peninsula, Japan, which is one of the best recorded large slope failures. Based on the previous results of waveform inversions and precise topographic surveys done before and after the event, we applied numerical simulations using the SHALTOP numerical model (Mangeney et al., 2007). This model describes homogeneous continuous granular flows on a 3D topography based on a depth averaged thin layer approximation. We assume a Coulomb's friction law with a constant friction coefficient, i. e. the friction is independent of the sliding velocity. We varied the friction coefficients in the simulation so that the resulting force acting on the surface agrees with the single force estimated from the seismic waveform inversion. Figure shows the force history of the east-west components after the band-pass filtering between 10-100 seconds. The force history of the simulation with frictional coefficient 0.27 (thin red line) the best agrees with the result of seismic waveform inversion (thick gray line). Although the amplitude is slightly different, phases are coherent for the main three pulses. This is an evidence that the point-source approximation works reasonably well for this particular event. The friction coefficient during the sliding was estimated to be 0.38 based on the seismic waveform inversion performed by the previous study and on the sliding block model (Yamada et al., 2013), whereas the frictional coefficient estimated from the numerical simulation was about 0.27. This discrepancy may be due to the digital elevation model, to the other forces such as pressure gradients and centrifugal acceleration included in the model. However, quantitative interpretation of this difference requires further investigation.

A Probabilistic Approach to Quantify the Impact of Uncertainty Propagation in Musculoskeletal Simulations

PubMed Central

Myers, Casey A.; Laz, Peter J.; Shelburne, Kevin B.; Davidson, Bradley S.

2015-01-01

Uncertainty that arises from measurement error and parameter estimation can significantly affect the interpretation of musculoskeletal simulations; however, these effects are rarely addressed. The objective of this study was to develop an open-source probabilistic musculoskeletal modeling framework to assess how measurement error and parameter uncertainty propagate through a gait simulation. A baseline gait simulation was performed for a male subject using OpenSim for three stages: inverse kinematics, inverse dynamics, and muscle force prediction. A series of Monte Carlo simulations were performed that considered intrarater variability in marker placement, movement artifacts in each phase of gait, variability in body segment parameters, and variability in muscle parameters calculated from cadaveric investigations. Propagation of uncertainty was performed by also using the output distributions from one stage as input distributions to subsequent stages. Confidence bounds (5–95%) and sensitivity of outputs to model input parameters were calculated throughout the gait cycle. The combined impact of uncertainty resulted in mean bounds that ranged from 2.7° to 6.4° in joint kinematics, 2.7 to 8.1 N m in joint moments, and 35.8 to 130.8 N in muscle forces. The impact of movement artifact was 1.8 times larger than any other propagated source. Sensitivity to specific body segment parameters and muscle parameters were linked to where in the gait cycle they were calculated. We anticipate that through the increased use of probabilistic tools, researchers will better understand the strengths and limitations of their musculoskeletal simulations and more effectively use simulations to evaluate hypotheses and inform clinical decisions. PMID:25404535

Multivariable Dynamic Ankle Mechanical Impedance With Relaxed Muscles

PubMed Central

Lee, Hyunglae; Krebs, Hermano Igo; Hogan, Neville

2015-01-01

Neurological or biomechanical disorders may distort ankle mechanical impedance and thereby impair locomotor function. This paper presents a quantitative characterization of multivariable ankle mechanical impedance of young healthy subjects when their muscles were relaxed, to serve as a baseline to compare with pathophysiological ankle properties of biomechanically and/or neurologically impaired patients. Measurements using a highly backdrivable wearable ankle robot combined with multi-input multi-output stochastic system identification methods enabled reliable characterization of ankle mechanical impedance in two degrees-of-freedom (DOFs) simultaneously, the sagittal and frontal planes. The characterization included important ankle properties unavailable from single DOF studies: coupling between DOFs and anisotropy as a function of frequency. Ankle impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness in both seated (knee flexed) and standing (knee straightened) postures. Stiffness in the sagittal plane was greater than in the frontal plane and furthermore, was greater when standing than when seated, most likely due to the stretch of bi-articular muscles (medial and lateral gastrocnemius). Very low off-diagonal partial coherences implied negligible coupling between dorsiflexion-plantarflexion and inversion-eversion. The directions of principal axes were tilted slightly counterclockwise from the original joint coordinates. The directional variation (anisotropy) of ankle impedance in the 2-D space formed by rotations in the sagittal and frontal planes exhibited a characteristic “peanut” shape, weak in inversion-eversion over a wide range of frequencies from the stiffness dominated region up to the inertia dominated region. Implications for the assessment of neurological and biomechanical impairments are discussed. PMID:24686292

Multivariable dynamic ankle mechanical impedance with relaxed muscles.

PubMed

Lee, Hyunglae; Krebs, Hermano Igo; Hogan, Neville

2014-11-01

Neurological or biomechanical disorders may distort ankle mechanical impedance and thereby impair locomotor function. This paper presents a quantitative characterization of multivariable ankle mechanical impedance of young healthy subjects when their muscles were relaxed, to serve as a baseline to compare with pathophysiological ankle properties of biomechanically and/or neurologically impaired patients. Measurements using a highly backdrivable wearable ankle robot combined with multi-input multi-output stochastic system identification methods enabled reliable characterization of ankle mechanical impedance in two degrees-of-freedom (DOFs) simultaneously, the sagittal and frontal planes. The characterization included important ankle properties unavailable from single DOF studies: coupling between DOFs and anisotropy as a function of frequency. Ankle impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness in both seated (knee flexed) and standing (knee straightened) postures. Stiffness in the sagittal plane was greater than in the frontal plane and furthermore, was greater when standing than when seated, most likely due to the stretch of bi-articular muscles (medial and lateral gastrocnemius). Very low off-diagonal partial coherences implied negligible coupling between dorsiflexion-plantarflexion and inversion-eversion. The directions of principal axes were tilted slightly counterclockwise from the original joint coordinates. The directional variation (anisotropy) of ankle impedance in the 2-D space formed by rotations in the sagittal and frontal planes exhibited a characteristic "peanut" shape, weak in inversion-eversion over a wide range of frequencies from the stiffness dominated region up to the inertia dominated region. Implications for the assessment of neurological and biomechanical impairments are discussed.

COMBINED DELAY AND GRAPH EMBEDDING OF EPILEPTIC DISCHARGES IN EEG REVEALS COMPLEX AND RECURRENT NONLINEAR DYNAMICS.

PubMed

Erem, B; Hyde, D E; Peters, J M; Duffy, F H; Brooks, D H; Warfield, S K

2015-04-01

The dynamical structure of the brain's electrical signals contains valuable information about its physiology. Here we combine techniques for nonlinear dynamical analysis and manifold identification to reveal complex and recurrent dynamics in interictal epileptiform discharges (IEDs). Our results suggest that recurrent IEDs exhibit some consistent dynamics, which may only last briefly, and so individual IED dynamics may need to be considered in order to understand their genesis. This could potentially serve to constrain the dynamics of the inverse source localization problem.

Brain regions sensitive to the face inversion effect: a functional magnetic resonance imaging study in humans.

PubMed

Leube, Dirk T; Yoon, Hyo Woon; Rapp, Alexander; Erb, Michael; Grodd, Wolfgang; Bartels, Mathias; Kircher, Tilo T J

2003-05-22

Perception of upright faces relies on configural processing. Therefore recognition of inverted, compared to upright faces is impaired. In a functional magnetic resonance imaging experiment we investigated the neural correlate of a face inversion task. Thirteen healthy subjects were presented with a equal number of upright and inverted faces alternating with a low level baseline with an upright and inverted picture of an abstract symbol. Brain activation was calculated for upright minus inverted faces. For this differential contrast, we found a signal change in the right superior temporal sulcus and right insula. Configural properties are processed in a network comprising right superior temporal and insular cortex.

The origin, global distribution, and functional impact of the human 8p23 inversion polymorphism.

PubMed

Salm, Maximilian P A; Horswell, Stuart D; Hutchison, Claire E; Speedy, Helen E; Yang, Xia; Liang, Liming; Schadt, Eric E; Cookson, William O; Wierzbicki, Anthony S; Naoumova, Rossi P; Shoulders, Carol C

2012-06-01

Genomic inversions are an increasingly recognized source of genetic variation. However, a lack of reliable high-throughput genotyping assays for these structures has precluded a full understanding of an inversion's phylogenetic, phenotypic, and population genetic properties. We characterize these properties for one of the largest polymorphic inversions in man (the ∼4.5-Mb 8p23.1 inversion), a structure that encompasses numerous signals of natural selection and disease association. We developed and validated a flexible bioinformatics tool that utilizes SNP data to enable accurate, high-throughput genotyping of the 8p23.1 inversion. This tool was applied retrospectively to diverse genome-wide data sets, revealing significant population stratification that largely follows a clinal "serial founder effect" distribution model. Phylogenetic analyses establish the inversion's ancestral origin within the Homo lineage, indicating that 8p23.1 inversion has occurred independently in the Pan lineage. The human inversion breakpoint was localized to an inverted pair of human endogenous retrovirus elements within the large, flanking low-copy repeats; experimental validation of this breakpoint confirmed these elements as the likely intermediary substrates that sponsored inversion formation. In five data sets, mRNA levels of disease-associated genes were robustly associated with inversion genotype. Moreover, a haplotype associated with systemic lupus erythematosus was restricted to the derived inversion state. We conclude that the 8p23.1 inversion is an evolutionarily dynamic structure that can now be accommodated into the understanding of human genetic and phenotypic diversity.

The origin, global distribution, and functional impact of the human 8p23 inversion polymorphism

PubMed Central

Salm, Maximilian P.A.; Horswell, Stuart D.; Hutchison, Claire E.; Speedy, Helen E.; Yang, Xia; Liang, Liming; Schadt, Eric E.; Cookson, William O.; Wierzbicki, Anthony S.; Naoumova, Rossi P.; Shoulders, Carol C.

2012-01-01

Genomic inversions are an increasingly recognized source of genetic variation. However, a lack of reliable high-throughput genotyping assays for these structures has precluded a full understanding of an inversion's phylogenetic, phenotypic, and population genetic properties. We characterize these properties for one of the largest polymorphic inversions in man (the ∼4.5-Mb 8p23.1 inversion), a structure that encompasses numerous signals of natural selection and disease association. We developed and validated a flexible bioinformatics tool that utilizes SNP data to enable accurate, high-throughput genotyping of the 8p23.1 inversion. This tool was applied retrospectively to diverse genome-wide data sets, revealing significant population stratification that largely follows a clinal “serial founder effect” distribution model. Phylogenetic analyses establish the inversion's ancestral origin within the Homo lineage, indicating that 8p23.1 inversion has occurred independently in the Pan lineage. The human inversion breakpoint was localized to an inverted pair of human endogenous retrovirus elements within the large, flanking low-copy repeats; experimental validation of this breakpoint confirmed these elements as the likely intermediary substrates that sponsored inversion formation. In five data sets, mRNA levels of disease-associated genes were robustly associated with inversion genotype. Moreover, a haplotype associated with systemic lupus erythematosus was restricted to the derived inversion state. We conclude that the 8p23.1 inversion is an evolutionarily dynamic structure that can now be accommodated into the understanding of human genetic and phenotypic diversity. PMID:22399572

Entropy-Bayesian Inversion of Time-Lapse Tomographic GPR data for Monitoring Dielectric Permittivity and Soil Moisture Variations

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

Hou, Z; Terry, N; Hubbard, S S

2013-02-12

In this study, we evaluate the possibility of monitoring soil moisture variation using tomographic ground penetrating radar travel time data through Bayesian inversion, which is integrated with entropy memory function and pilot point concepts, as well as efficient sampling approaches. It is critical to accurately estimate soil moisture content and variations in vadose zone studies. Many studies have illustrated the promise and value of GPR tomographic data for estimating soil moisture and associated changes, however, challenges still exist in the inversion of GPR tomographic data in a manner that quantifies input and predictive uncertainty, incorporates multiple data types, handles non-uniquenessmore » and nonlinearity, and honors time-lapse tomograms collected in a series. To address these challenges, we develop a minimum relative entropy (MRE)-Bayesian based inverse modeling framework that non-subjectively defines prior probabilities, incorporates information from multiple sources, and quantifies uncertainty. The framework enables us to estimate dielectric permittivity at pilot point locations distributed within the tomogram, as well as the spatial correlation range. In the inversion framework, MRE is first used to derive prior probability distribution functions (pdfs) of dielectric permittivity based on prior information obtained from a straight-ray GPR inversion. The probability distributions are then sampled using a Quasi-Monte Carlo (QMC) approach, and the sample sets provide inputs to a sequential Gaussian simulation (SGSim) algorithm that constructs a highly resolved permittivity/velocity field for evaluation with a curved-ray GPR forward model. The likelihood functions are computed as a function of misfits, and posterior pdfs are constructed using a Gaussian kernel. Inversion of subsequent time-lapse datasets combines the Bayesian estimates from the previous inversion (as a memory function) with new data. The memory function and pilot point design takes advantage of the spatial-temporal correlation of the state variables. We first apply the inversion framework to a static synthetic example and then to a time-lapse GPR tomographic dataset collected during a dynamic experiment conducted at the Hanford Site in Richland, WA. We demonstrate that the MRE-Bayesian inversion enables us to merge various data types, quantify uncertainty, evaluate nonlinear models, and produce more detailed and better resolved estimates than straight-ray based inversion; therefore, it has the potential to improve estimates of inter-wellbore dielectric permittivity and soil moisture content and to monitor their temporal dynamics more accurately.« less

Entropy-Bayesian Inversion of Time-Lapse Tomographic GPR data for Monitoring Dielectric Permittivity and Soil Moisture Variations

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

Hou, Zhangshuan; Terry, Neil C.; Hubbard, Susan S.

2013-02-22

In this study, we evaluate the possibility of monitoring soil moisture variation using tomographic ground penetrating radar travel time data through Bayesian inversion, which is integrated with entropy memory function and pilot point concepts, as well as efficient sampling approaches. It is critical to accurately estimate soil moisture content and variations in vadose zone studies. Many studies have illustrated the promise and value of GPR tomographic data for estimating soil moisture and associated changes, however, challenges still exist in the inversion of GPR tomographic data in a manner that quantifies input and predictive uncertainty, incorporates multiple data types, handles non-uniquenessmore » and nonlinearity, and honors time-lapse tomograms collected in a series. To address these challenges, we develop a minimum relative entropy (MRE)-Bayesian based inverse modeling framework that non-subjectively defines prior probabilities, incorporates information from multiple sources, and quantifies uncertainty. The framework enables us to estimate dielectric permittivity at pilot point locations distributed within the tomogram, as well as the spatial correlation range. In the inversion framework, MRE is first used to derive prior probability density functions (pdfs) of dielectric permittivity based on prior information obtained from a straight-ray GPR inversion. The probability distributions are then sampled using a Quasi-Monte Carlo (QMC) approach, and the sample sets provide inputs to a sequential Gaussian simulation (SGSIM) algorithm that constructs a highly resolved permittivity/velocity field for evaluation with a curved-ray GPR forward model. The likelihood functions are computed as a function of misfits, and posterior pdfs are constructed using a Gaussian kernel. Inversion of subsequent time-lapse datasets combines the Bayesian estimates from the previous inversion (as a memory function) with new data. The memory function and pilot point design takes advantage of the spatial-temporal correlation of the state variables. We first apply the inversion framework to a static synthetic example and then to a time-lapse GPR tomographic dataset collected during a dynamic experiment conducted at the Hanford Site in Richland, WA. We demonstrate that the MRE-Bayesian inversion enables us to merge various data types, quantify uncertainty, evaluate nonlinear models, and produce more detailed and better resolved estimates than straight-ray based inversion; therefore, it has the potential to improve estimates of inter-wellbore dielectric permittivity and soil moisture content and to monitor their temporal dynamics more accurately.« less

Guidance of Nonlinear Nonminimum-Phase Dynamic Systems

NASA Technical Reports Server (NTRS)

Devasia, Santosh

1997-01-01

The first two years research work has advanced the inversion-based guidance theory for: (1) systems with non-hyperbolic internal dynamics; (2) systems with parameter jumps; (3) systems where a redesign of the output trajectory is desired; and (4) the generation of recovery guidance maneuvers.

All-electrical detection of spin dynamics in magnetic antidot lattices by the inverse spin Hall effect

DOE PAGES

Jungfleisch, Matthias B.; Zhang, Wei; Ding, Junjia; ...

2016-02-03

The understanding of spin dynamics in laterally confined structures on sub-micron length scales has become a significant aspect of the development of novel magnetic storage technologies. Numerous ferromagnetic resonance measurements, optical characterization by Kerr microscopy and Brillouin light scattering spectroscopy and x-ray studies were carried out to detect the dynamics in patterned magnetic antidot lattices. Here, we investigate Oersted-field driven spin dynamics in rectangular Ni80Fe20/Pt antidot lattices with different lattice parameters by electrical means. When the system is driven to resonance, a dc voltage across the length of the sample is detected that changes its sign upon field reversal, whichmore » is in agreement with a rectification mechanism based on the inverse spin Hall effect. Furthermore, we show that the voltage output scales linearly with the applied microwave drive in the investigated range of powers. Lastly, our findings have direct implications on the development of engineered magnonics applications and devices.« less

Estimation of the full-field dynamic response of a floating bridge using Kalman-type filtering algorithms

NASA Astrophysics Data System (ADS)

Petersen, Ø. W.; Øiseth, O.; Nord, T. S.; Lourens, E.

2018-07-01

Numerical predictions of the dynamic response of complex structures are often uncertain due to uncertainties inherited from the assumed load effects. Inverse methods can estimate the true dynamic response of a structure through system inversion, combining measured acceleration data with a system model. This article presents a case study of full-field dynamic response estimation of a long-span floating bridge: the Bergøysund Bridge in Norway. This bridge is instrumented with a network of 14 triaxial accelerometers. The system model consists of 27 vibration modes with natural frequencies below 2 Hz, obtained from a tuned finite element model that takes the fluid-structure interaction with the surrounding water into account. Two methods, a joint input-state estimation algorithm and a dual Kalman filter, are applied to estimate the full-field response of the bridge. The results demonstrate that the displacements and the accelerations can be estimated at unmeasured locations with reasonable accuracy when the wave loads are the dominant source of excitation.

Identification of dynamic characteristics of flexible rotors as dynamic inverse problem

NASA Technical Reports Server (NTRS)

Roisman, W. P.; Vajingortin, L. D.

1991-01-01

The problem of dynamic and balancing of flexible rotors were considered, which were set and solved as the problem of the identification of flexible rotor systems, which is the same as the inverse problem of the oscillation theory dealing with the task of the identifying the outside influences and system parameters on the basis of the known laws of motion. This approach to the problem allows the disclosure the picture of disbalances throughout the rotor-under-test (which traditional methods of flexible rotor balancing, based on natural oscillations, could not provide), and identify dynamic characteristics of the system, which correspond to a selected mathematical model. Eventually, various methods of balancing were developed depending on the special features of the machines as to their design, technology, and operation specifications. Also, theoretical and practical methods are given for the flexible rotor balancing at far from critical rotation frequencies, which does not necessarily require the knowledge forms of oscillation, dissipation, and elasticity and inertia characteristics, and to use testing masses.

Neural networks with excitatory and inhibitory components: Direct and inverse problems by a mean-field approach

NASA Astrophysics Data System (ADS)

di Volo, Matteo; Burioni, Raffaella; Casartelli, Mario; Livi, Roberto; Vezzani, Alessandro

2016-01-01

We study the dynamics of networks with inhibitory and excitatory leak-integrate-and-fire neurons with short-term synaptic plasticity in the presence of depressive and facilitating mechanisms. The dynamics is analyzed by a heterogeneous mean-field approximation, which allows us to keep track of the effects of structural disorder in the network. We describe the complex behavior of different classes of excitatory and inhibitory components, which give rise to a rich dynamical phase diagram as a function of the fraction of inhibitory neurons. Using the same mean-field approach, we study and solve a global inverse problem: reconstructing the degree probability distributions of the inhibitory and excitatory components and the fraction of inhibitory neurons from the knowledge of the average synaptic activity field. This approach unveils new perspectives on the numerical study of neural network dynamics and the possibility of using these models as a test bed for the analysis of experimental data.

Low-moderate urine arsenic and biomarkers of thrombosis and inflammation in the Strong Heart Study

PubMed Central

Navas-Acien, Ana; Grau-Pérez, Maria; Francesconi, Kevin A.; Goessler, Walter; Guallar, Eliseo; Umans, Jason G.; Best, Lyle G.; Newman, Jonathan D.

2017-01-01

The underlying pathology of arsenic-related cardiovascular disease (CVD) is unknown. Few studies have evaluated pathways through thrombosis and inflammation for arsenic-related CVD, especially at low-moderate arsenic exposure levels (<100 μg/L in drinking water). We evaluated the association of chronic low-moderate arsenic exposure, measured as the sum of inorganic and methylated arsenic species in urine (ΣAs), with plasma biomarkers of thrombosis and inflammation in American Indian adults (45–74 years) in the Strong Heart Study. We evaluated the cross-sectional and longitudinal associations between baseline ΣAs with fibrinogen at three visits (baseline, 1989–91; Visit 2, 1993–95, Visit 3, 1998–99) using mixed models and the associations between baseline ΣAs and Visit 2 plasminogen activator inhibitor-1 (PAI-1) and high sensitivity C-reactive protein (hsCRP) using linear regression. Median (interquartile range) concentrations of baseline ΣAs and fibrinogen, and Visit 2 hsCRP and PAI-1 were 8.4 (5.1, 14.3) μg/g creatinine, 346 (304, 393) mg/dL, 44 (30, 67) mg/L, and 3.8 (2.0, 7.0) ng/mL, respectively. Comparing the difference between the 75th and the 25th percentile of ΣAs (14.3 vs. 5.1 μg/g creatinine), ΣAs was positively associated with baseline fibrinogen among those with diabetes (adjusted geometric mean ratio (GMR): 1.05, 95% CI: 1.02, 1.07) not associated among those without diabetes (GMR: 1.01, 95% CI: 0.99, 1.02) (p-interaction for diabetes = 0.014), inversely associated with PAI-1 (GMR: 0.94, 95% CI: 0.90, 0.99), and not associated with hsCRP (GMR: 1.00, 95% CI: 0.93, 1.08). We found no evidence for an association between baseline ΣAs and annual change in fibrinogen over follow-up (p-interaction = 0.28 and 0.12 for diabetes and non-diabetes, respectively). Low-moderate arsenic exposure was positively associated with baseline fibrinogen in participants with diabetes and unexpectedly inversely associated with PAI-1. Further research should evaluate the role of prothrombotic factors in arsenic-related cardiovascular disease. PMID:28771557

Baseline modeling of the Maysville cable-stayed bridge over the Ohio River.

DOT National Transportation Integrated Search

2005-07-01

This report presents the baseline modeling of the Maysville cable-stayed bridge which connects Maysville, Kentucky and Aberdeen, Ohio over the Ohio River. The objective of this study is to establish the bridge baseline model via the dynamics-based te...

Recovery of dynamic balance after general anesthesia with sevoflurane in short-duration oral surgery.

PubMed

Fujisawa, Toshiaki; Miyamoto, Eriko; Takuma, Shigeru; Shibuya, Makiko; Kurozumi, Akihiro; Kimura, Yukifumi; Kamekura, Nobuhito; Fukushima, Kazuaki

2009-01-01

Recovery of dynamic balance, involving adjustment of the center of gravity, is essential for safe discharge on foot after ambulatory anesthesia. The purpose of this study was to assess the recovery of dynamic balance after general anesthesia with sevoflurane, using two computerized dynamic posturographies. Nine hospitalized patients undergoing oral surgery of less than 2 h duration under general anesthesia (air-oxygensevoflurane) were studied. A dynamic balance test, assessing the ability of postural control against unpredictable perturbation stimuli (Stability System; Biodex Medical), a walking analysis test using sheets with foot pressure sensors (Walk Way-MG1000; Anima), and two simple psychomotor function tests were performed before anesthesia (baseline), and 150 and 210 min after the emergence from anesthesia. Only the double-stance phase in the walking analysis test showed a significant difference between baseline and results at 150 min. None of the other variables showed any differences among results at baseline and at 150 and 210 min. The recovery times for dynamic balance and psychomotor function seem to be within 150 min after emergence from general anesthesia with sevoflurane in patients undergoing oral surgery of less than 2-h duration.

Abnormal intrinsic dynamics of dendritic spines in a fragile X syndrome mouse model in vivo.

PubMed

Nagaoka, Akira; Takehara, Hiroaki; Hayashi-Takagi, Akiko; Noguchi, Jun; Ishii, Kazuhiko; Shirai, Fukutoshi; Yagishita, Sho; Akagi, Takanori; Ichiki, Takanori; Kasai, Haruo

2016-05-25

Dendritic spine generation and elimination play an important role in learning and memory, the dynamics of which have been examined within the neocortex in vivo. Spine turnover has also been detected in the absence of specific learning tasks, and is frequently exaggerated in animal models of autistic spectrum disorder (ASD). The present study aimed to examine whether the baseline rate of spine turnover was activity-dependent. This was achieved using a microfluidic brain interface and open-dura surgery, with the goal of abolishing neuronal Ca(2+) signaling in the visual cortex of wild-type mice and rodent models of fragile X syndrome (Fmr1 knockout [KO]). In wild-type and Fmr1 KO mice, the majority of baseline turnover was found to be activity-independent. Accordingly, the application of matrix metalloproteinase-9 inhibitors selectively restored the abnormal spine dynamics observed in Fmr1 KO mice, without affecting the intrinsic dynamics of spine turnover in wild-type mice. Such findings indicate that the baseline turnover of dendritic spines is mediated by activity-independent intrinsic dynamics. Furthermore, these results suggest that the targeting of abnormal intrinsic dynamics might pose a novel therapy for ASD.

Coffee consumption, serum gamma-glutamyltransferase and risk of type II diabetes.

PubMed

Bidel, S; Silventoinen, K; Hu, G; Lee, D-H; Kaprio, J; Tuomilehto, J

2008-02-01

To study the joint association of coffee consumption and serum gamma-glutamyltransferase (GGT) levels on the risk of developing type II diabetes. A total of 21,826 Finnish men and women who were 35-74 years of age and without any history of diabetes at baseline (years 1982, 1987, 1992 and 1997) were included in the present analyses. They were prospectively followed up for onset of type II diabetes (n=862 cases), death or until the end of the year 2002. Coffee consumption, serum GGT and other study parameters were determined at baseline using standardized measurements. Analyses were stratified by the serum GGT level classified into two classes using the 75th sex-specific percentiles as the cut point. Coffee consumption was significantly and inversely associated with incident diabetes among both men and women. Serum GGT modified the association between coffee consumption and incident diabetes. Subjects in the high category of coffee consumption with the GGT level > or = 75th percentile showed a significant inverse association for women, and for both sexes combined. The association was not significant in subjects with the GGT level < or = 75th percentile. There was a significant interaction effect of GGT and coffee consumption on risk of type II diabetes in data of women (P=0.05) and in both sexes combined (P=0.02). Habitual coffee consumption is associated with lower incidence of type II diabetes particularly in those with higher baseline serum GGT levels.

Density of calcium in the ascending thoracic aorta and risk of incident cardiovascular disease events.

PubMed

Thomas, Isac C; McClelland, Robyn L; Michos, Erin D; Allison, Matthew A; Forbang, Nketi I; Longstreth, W T; Post, Wendy S; Wong, Nathan D; Budoff, Matthew J; Criqui, Michael H

2017-10-01

The volume and density of coronary artery calcium (CAC) both independently predict cardiovascular disease (CVD) beyond standard risk factors, with CAC density inversely associated with incident CVD after accounting for CAC volume. We tested the hypothesis that ascending thoracic aorta calcium (ATAC) volume and density predict incident CVD events independently of CAC. The Multi-Ethnic Study of Atherosclerosis (MESA) is a prospective cohort study of participants without clinical CVD at baseline. ATAC and CAC were measured from baseline cardiac computed tomography (CT). Cox regression models were used to estimate the associations of ATAC volume and density with incident coronary heart disease (CHD) events and CVD events, after adjustment for standard CVD risk factors and CAC volume and density. Among 6811 participants, 234 (3.4%) had prevalent ATAC and 3395 (49.8%) had prevalent CAC. Over 10.3 years, 355 CHD and 562 CVD events occurred. One-standard deviation higher ATAC density was associated with a lower risk of CHD (HR 0.48 [95% CI 0.29-0.79], p<0.01) and CVD (HR 0.56 [0.37-0.84], p<0.01) after full adjustment. ATAC volume was not associated with outcomes after full adjustment. ATAC was uncommon in a cohort free of clinical CVD at baseline. However, ATAC density was inversely associated with incident CHD and CVD after adjustment for CVD risk factors and CAC volume and density. Copyright © 2017 Elsevier B.V. All rights reserved.

Dietary fiber and progression of atherosclerosis: the Los Angeles Atherosclerosis Study.

PubMed

Wu, Huiyun; Dwyer, Kathleen M; Fan, Zhihong; Shircore, Anne; Fan, Jing; Dwyer, James H

2003-12-01

Several epidemiologic studies found weak protective relations between dietary fiber intake and the risk of cardiovascular disease events. However, few of the studies addressed possible mechanisms of the effect. In the present study, we estimated relations between the progression of atherosclerosis and the intake of selective dietary fiber fractions. Mediation of the relations by serum lipids was also investigated. Participants who were free of heart disease and aged 40-60 y were recruited into the cohort (n = 573; 47% women). The intima-media thickness (IMT) of the common carotid arteries was measured ultrasonographically at the baseline examination and at 2 follow-up examinations (n = 500), dietary intakes were assessed with six 24-h recalls (3 at baseline and 3 at the first follow-up examination), and blood samples were analyzed at baseline and at both follow-up examinations. A significant inverse association was observed between IMT progression and the intakes of viscous fiber (P = 0.05) and pectin (P = 0.01). Correction for measurement error increased the magnitude of these estimated effects. The ratio of total to HDL cholesterol was inversely related to the intakes of total fiber (P = 0.01), viscous fiber (P = 0.05), and pectin (P = 0.01). The magnitude of the association between IMT progression and the intakes of viscous fiber and pectin was attenuated by adjustment for serum lipids. The intake of viscous fiber, especially pectin, appears to protect against IMT progression. Serum lipids may act as a mediator between dietary fiber intake and IMT progression.

Query-based learning for aerospace applications.

PubMed

Saad, E W; Choi, J J; Vian, J L; Wunsch, D C Ii

2003-01-01

Models of real-world applications often include a large number of parameters with a wide dynamic range, which contributes to the difficulties of neural network training. Creating the training data set for such applications becomes costly, if not impossible. In order to overcome the challenge, one can employ an active learning technique known as query-based learning (QBL) to add performance-critical data to the training set during the learning phase, thereby efficiently improving the overall learning/generalization. The performance-critical data can be obtained using an inverse mapping called network inversion (discrete network inversion and continuous network inversion) followed by oracle query. This paper investigates the use of both inversion techniques for QBL learning, and introduces an original heuristic to select the inversion target values for continuous network inversion method. Efficiency and generalization was further enhanced by employing node decoupled extended Kalman filter (NDEKF) training and a causality index (CI) as a means to reduce the input search dimensionality. The benefits of the overall QBL approach are experimentally demonstrated in two aerospace applications: a classification problem with large input space and a control distribution problem.

Revealing a double-inversion mechanism for the F⁻+CH₃Cl SN2 reaction.

PubMed

Szabó, István; Czakó, Gábor

2015-01-19

Stereo-specific reaction mechanisms play a fundamental role in chemistry. The back-side attack inversion and front-side attack retention pathways of the bimolecular nucleophilic substitution (SN2) reactions are the textbook examples for stereo-specific chemical processes. Here, we report an accurate global analytic potential energy surface (PES) for the F(-)+CH₃Cl SN2 reaction, which describes both the back-side and front-side attack substitution pathways as well as the proton-abstraction channel. Moreover, reaction dynamics simulations on this surface reveal a novel double-inversion mechanism, in which an abstraction-induced inversion via a FH···CH₂Cl(-) transition state is followed by a second inversion via the usual [F···CH₃···Cl](-) saddle point, thereby opening a lower energy reaction path for retention than the front-side attack. Quasi-classical trajectory computations for the F(-)+CH₃Cl(ν1=0, 1) reactions show that the front-side attack is a fast direct, whereas the double inversion is a slow indirect process.

Anomalous Subsidence at Rifted Continental Margins: Distinguishing Mantle Dynamic Topography from Anomalous Oceanic Crustal Thickness

NASA Astrophysics Data System (ADS)

Cowie, L.; Kusznir, N. J.

2012-12-01

It has been proposed that some continental rifted margins have anomalous subsidence histories and that at breakup they were elevated at shallower bathymetries than the isostatic response of classical rift models (McKenzie 1978) would predict. The existence of anomalous syn or post breakup subsidence of this form would have important implications for our understanding of the geodynamics of continental breakup and rifted continental margin formation, margin subsidence history and the evolution of syn and post breakup depositional systems. We have investigated three rifted continental margins; the Gulf of Aden, Galicia Bank and the Gulf of Lions, to determine whether the oceanic crust in the ocean-continent transition of these margins has present day anomalous subsidence and if so, whether it is caused by mantle dynamic topography or anomalous oceanic crustal thickness. Residual depth anomalies (RDA) corrected for sediment loading, using flexural backstripping and decompaction, have been calculated by comparing observed and age predicted oceanic bathymetries in order to identify anomalous oceanic bathymetry and subsidence at these margins. Age predicted bathymetric anomalies have been calculated using the thermal plate model predictions from Crosby & McKenzie (2009). Non-zero sediment corrected RDAs may result from anomalous oceanic crustal thickness with respect to the global average, or from mantle dynamic uplift. Positive RDAs may result from thicker than average oceanic crust or mantle dynamic uplift; negative RDAs may result from thinner than average oceanic crust or mantle dynamic subsidence. Gravity inversion incorporating a lithosphere thermal gravity anomaly correction and sediment thickness from 2D seismic data has been used to determine Moho depth and oceanic crustal basement thickness. The reference Moho depths used in the gravity inversion have been calibrated against seismic refraction Moho depths. The gravity inversion crustal basement thicknesses together with Airy isostasy have been used to predict a "synthetic" gravity derived RDA. Sediment corrected RDA for oceanic crust in the Gulf of Aden are positive (+750m) indicating anomalous uplift with respect to normal subsidence. Gravity inversion predicts normal thickness oceanic crust and a zero "synthetic" gravity derived RDA in the oceanic domain. The difference between the positive sediment corrected RDA and the zero "synthetic" gravity derived RDA, implies that the anomalous subsidence reported in the Gulf of Aden is the result of mantle dynamic uplift. For the oceanic crust outboard of Galicia Bank both the sediment corrected RDA and the "synthetic" gravity derived RDA are negative (-800m) and of similar magnitude, indicating anomalous subsidence, which is the result of anomalously thin oceanic crust, not mantle dynamic topography. We conclude that there is negligible mantle dynamic topography influencing the Galicia Bank region. In the Gulf of Lions, gravity inversion predicts thinner than average oceanic crust. Both sediment corrected RDA (-1km) and "synthetic" gravity derived RDA (-500m) are negative. The more negative sediment corrected RDA compared with the "synthetic" gravity derived RDA implies that the anomalous subsidence in the Gulf of Lions is the result of mantle dynamic subsidence as well as thinner than average oceanic crust.

Nonlinear Problems in Fluid Dynamics and Inverse Scattering

DTIC Science & Technology

1993-05-31

nonlinear Kadomtsev - Petviashvili (KP) equations , have solutions which will become infinite in finite time. This phenomenon is sometimes referred to as...40 (November 1992). 4 7. Wave Collapse and Instability of Solitary Waves of a Generalized Nonlinear Kaoiomtsev- Petviashvili Equation , X.P. Wang, M.J...words) The inverse scattering of a class of differential-difference equations and multidimensional operators has been constructed. Solutions of nonlinear

The Tropopause Inversion Layer: New Observations, New Theories

NASA Astrophysics Data System (ADS)

Tandon, N.; Randel, W. J.; Pan, L.; Son, S.; Polvani, L. M.

2009-12-01

There is now great interest in the tropopause inversion inversion layer (TIL), a 1-2 km region just above the tropopause where there is a spike in static stability. Radio occultation data from the COSMIC GPS mission are providing an unprecedented level of spatial and temporal resolution with which to analyze the TIL. We start by showing the agreement between GPS data and radiosondes. We then examine the causes and consequences of the TIL. Observations from the ACE satellite and fixed dynamical heating calculations suggest strong roles for water vapor and ozone in the formation and modulation of the TIL. This agrees with observations showing a large TIL in the polar winter, where water vapor levels are persistently high. It is also clear that TIL strength is related to vorticity, but observations and models have important differences that need to be reconciled. These dynamical considerations dovetail with observations showing high TIL variability in the storm-track regions. Finally there is evidence from ozonesonde data that the TIL may be coupled to transport across the tropopause.

Application of neural models as controllers in mobile robot velocity control loop

NASA Astrophysics Data System (ADS)

Cerkala, Jakub; Jadlovska, Anna

2017-01-01

This paper presents the application of an inverse neural models used as controllers in comparison to classical PI controllers for velocity tracking control task used in two-wheel, differentially driven mobile robot. The PI controller synthesis is based on linear approximation of actuators with equivalent load. In order to obtain relevant datasets for training of feed-forward multi-layer perceptron based neural network used as neural model, the mathematical model of mobile robot, that combines its kinematic and dynamic properties such as chassis dimensions, center of gravity offset, friction and actuator parameters is used. Neural models are trained off-line to act as an inverse dynamics of DC motors with particular load using data collected in simulation experiment for motor input voltage step changes within bounded operating area. The performances of PI controllers versus inverse neural models in mobile robot internal velocity control loops are demonstrated and compared in simulation experiment of navigation control task for line segment motion in plane.

Efficient preconditioning of the electronic structure problem in large scale ab initio molecular dynamics simulations

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

Schiffmann, Florian; VandeVondele, Joost, E-mail: Joost.VandeVondele@mat.ethz.ch

2015-06-28

We present an improved preconditioning scheme for electronic structure calculations based on the orbital transformation method. First, a preconditioner is developed which includes information from the full Kohn-Sham matrix but avoids computationally demanding diagonalisation steps in its construction. This reduces the computational cost of its construction, eliminating a bottleneck in large scale simulations, while maintaining rapid convergence. In addition, a modified form of Hotelling’s iterative inversion is introduced to replace the exact inversion of the preconditioner matrix. This method is highly effective during molecular dynamics (MD), as the solution obtained in earlier MD steps is a suitable initial guess. Filteringmore » small elements during sparse matrix multiplication leads to linear scaling inversion, while retaining robustness, already for relatively small systems. For system sizes ranging from a few hundred to a few thousand atoms, which are typical for many practical applications, the improvements to the algorithm lead to a 2-5 fold speedup per MD step.« less

The control of satellites with microgravity constraints: The COMET Control System

NASA Astrophysics Data System (ADS)

Grossman, Walter; Freesland, Douglas

1994-05-01

The COMET attitude determination and control system, using inverse dynamics and a novel torque distribution/momentum management technique, has shown great flexibility, performance, and robustness. Three-axis control with two wheels is an inherent consequence of inverse dynamics control which allows for reduction in spacecraft weight and cost, or alternatively, provides a simple means of failure-redundancy for three-wheel spacecraft. The control system, without modification, has continued to perform well in spite of large changes in spacecraft mass properties and mission orbit altitude that have occurred during development. This flexibility has obviated imposition of early stringent ADACS design constraints and has greatly reduced commonly incurred ADACS modification costs and delay associated with program maturation.

The control of satellites with microgravity constraints: The COMET Control System

NASA Technical Reports Server (NTRS)

Grossman, Walter; Freesland, Douglas

1994-01-01

The COMET attitude determination and control system, using inverse dynamics and a novel torque distribution/momentum management technique, has shown great flexibility, performance, and robustness. Three-axis control with two wheels is an inherent consequence of inverse dynamics control which allows for reduction in spacecraft weight and cost, or alternatively, provides a simple means of failure-redundancy for three-wheel spacecraft. The control system, without modification, has continued to perform well in spite of large changes in spacecraft mass properties and mission orbit altitude that have occurred during development. This flexibility has obviated imposition of early stringent ADACS design constraints and has greatly reduced commonly incurred ADACS modification costs and delay associated with program maturation.

Comparison of iterative inverse coarse-graining methods

NASA Astrophysics Data System (ADS)

Rosenberger, David; Hanke, Martin; van der Vegt, Nico F. A.

2016-10-01

Deriving potentials for coarse-grained Molecular Dynamics (MD) simulations is frequently done by solving an inverse problem. Methods like Iterative Boltzmann Inversion (IBI) or Inverse Monte Carlo (IMC) have been widely used to solve this problem. The solution obtained by application of these methods guarantees a match in the radial distribution function (RDF) between the underlying fine-grained system and the derived coarse-grained system. However, these methods often fail in reproducing thermodynamic properties. To overcome this deficiency, additional thermodynamic constraints such as pressure or Kirkwood-Buff integrals (KBI) may be added to these methods. In this communication we test the ability of these methods to converge to a known solution of the inverse problem. With this goal in mind we have studied a binary mixture of two simple Lennard-Jones (LJ) fluids, in which no actual coarse-graining is performed. We further discuss whether full convergence is actually needed to achieve thermodynamic representability.

Neural-Based Compensation of Nonlinearities in an Airplane Longitudinal Model with Dynamic-Inversion Control

PubMed Central

Li, YuHui; Jin, FeiTeng

2017-01-01

The inversion design approach is a very useful tool for the complex multiple-input-multiple-output nonlinear systems to implement the decoupling control goal, such as the airplane model and spacecraft model. In this work, the flight control law is proposed using the neural-based inversion design method associated with the nonlinear compensation for a general longitudinal model of the airplane. First, the nonlinear mathematic model is converted to the equivalent linear model based on the feedback linearization theory. Then, the flight control law integrated with this inversion model is developed to stabilize the nonlinear system and relieve the coupling effect. Afterwards, the inversion control combined with the neural network and nonlinear portion is presented to improve the transient performance and attenuate the uncertain effects on both external disturbances and model errors. Finally, the simulation results demonstrate the effectiveness of this controller. PMID:29410680

Baseline factors associated with incident HIV and STI in four microbicide trials.

PubMed

Feldblum, Paul J; Lie, Che-Chin; Weaver, Mark A; Van Damme, Lut; Halpern, Vera; Adeiga, Adesina; Bakare, Rashidi; Schwartz, Jill; Becker, Marissa; Solomon, Suniti

2010-10-01

Analyzing pooled data from 4 recent microbicide trials, we aimed to determine characteristics of participants at higher risk of HIV and sexually transmitted infections (STIs), to inform targeted recruitment, preserved study power, and potentially smaller study sizes in future trials. We evaluated the relationships between participants' characteristics and the incidence of HIV, STIs, and reproductive tract infections (RTIs). We calculated incidence rates as the number of infection events divided by the person-years of observation. We applied Cox regression models to assess the relationships between baseline demographic, reproductive and behavioral factors and incident HIV, STIs and RTIs. The pooled incidence rates for HIV, chlamydia, and gonorrhea were 2.1, 6.4 and 9.9 per 100 person-years, respectively. Proportions of participants with trichomoniasis, bacterial vaginosis (BV), and candidiasis were 0.06, 0.40, and 0.40, respectively. In final multivariable models, age and education were significantly (and inversely) associated with incident HIV; baseline chlamydia, baseline trichomoniasis, and younger age were associated with incident Chlamydia; and baseline gonorrhea infection, younger age, less education, nulliparous status, baseline chlamydia, and condom use for contraception were associated with incident gonorrhea. Three factors were associated with trichomoniasis: baseline trichomoniasis infection, baseline chlamydia, and baseline BV. Only younger age was robustly associated with multiple STI outcomes in our multivariable analyses. Although there was little evidence of associations between baseline STIs and incident HIV, they were strongly associated with incident STIs. We found no evidence that measured baseline sexual behavior factors were associated with incident HIV or STIs.

Deformation Time-Series of the Lost-Hills Oil Field using a Multi-Baseline Interferometric SAR Inversion Algorithm with Finite Difference Smoothing Constraints

NASA Astrophysics Data System (ADS)

Werner, C. L.; Wegmüller, U.; Strozzi, T.

2012-12-01

The Lost-Hills oil field located in Kern County,California ranks sixth in total remaining reserves in California. Hundreds of densely packed wells characterize the field with one well every 5000 to 20000 square meters. Subsidence due to oil extraction can be grater than 10 cm/year and is highly variable both in space and time. The RADARSAT-1 SAR satellite collected data over this area with a 24-day repeat during a 2 year period spanning 2002-2004. Relatively high interferometric correlation makes this an excellent region for development and test of deformation time-series inversion algorithms. Errors in deformation time series derived from a stack of differential interferograms are primarily due to errors in the digital terrain model, interferometric baselines, variability in tropospheric delay, thermal noise and phase unwrapping errors. Particularly challenging is separation of non-linear deformation from variations in troposphere delay and phase unwrapping errors. In our algorithm a subset of interferometric pairs is selected from a set of N radar acquisitions based on criteria of connectivity, time interval, and perpendicular baseline. When possible, the subset consists of temporally connected interferograms, otherwise the different groups of interferograms are selected to overlap in time. The maximum time interval is constrained to be less than a threshold value to minimize phase gradients due to deformation as well as minimize temporal decorrelation. Large baselines are also avoided to minimize the consequence of DEM errors on the interferometric phase. Based on an extension of the SVD based inversion described by Lee et al. ( USGS Professional Paper 1769), Schmidt and Burgmann (JGR, 2003), and the earlier work of Berardino (TGRS, 2002), our algorithm combines estimation of the DEM height error with a set of finite difference smoothing constraints. A set of linear equations are formulated for each spatial point that are functions of the deformation velocities during the time intervals spanned by the interferogram and a DEM height correction. The sensitivity of the phase to the height correction depends on the length of the perpendicular baseline of each interferogram. This design matrix is augmented with a set of additional weighted constraints on the acceleration that penalize rapid velocity variations. The weighting factor γ can be varied from 0 (no smoothing) to a large values (> 10) that yield an essentially linear time-series solution. The factor can be tuned to take into account a priori knowledge of the deformation non-linearity. The difference between the time-series solution and the unconstrained time-series can be interpreted as due to a combination of tropospheric path delay and baseline error. Spatial smoothing of the residual phase leads to an improved atmospheric model that can be fed back into the model and iterated. Our analysis shows non-linear deformation related to changes in the oil extraction as well as local height corrections improving on the low resolution 3 arc-sec SRTM DEM.

Nut consumption and total and cause-specific mortality: results from the Golestan Cohort Study

PubMed Central

Eslamparast, Tannaz; Sharafkhah, Maryam; Poustchi, Hossein; Hashemian, Maryam; Dawsey, Sanford M; Freedman, Neal D; Boffetta, Paolo; Abnet, Christian C; Etemadi, Arash; Pourshams, Akram; Malekshah, Akbar Fazeltabar; Islami, Farhad; Kamangar, Farin; Merat, Shahin; Brennan, Paul; Hekmatdoost, Azita; Malekzadeh, Reza

2017-01-01

Abstract Background: A number of prospective studies have observed inverse associations between nut consumption and chronic diseases. However, these studies have predominantly been conducted in Western countries, where nut consumption tends to be more common among individuals with healthier lifestyles. It is important to examine the association in other parts of the world, and particularly among populations with different patterns of disease, socioeconomic status, lifestyles and disease risk factors. Our objective was to examine the association between nut consumption and mortality in a population whose nut consumption does not track with a healthy lifestyle. Methods: We examined the association between nut consumption and all-cause and cause-specific mortality in the 50 045 participants of the Golestan Cohort Study. Participants were aged 40 and older at baseline in 2004, and have been actively followed since that time. Dietary data were collected using a validated semi-quantitative food frequency questionnaire that was administered at baseline. Results: During 349 677 person-years of follow-up, 3981 cohort participants died, including 1732 women and 2249 men. Nut consumption was associated inversely with all-cause mortality. The pooled multivariate adjusted hazard ratios for death among participants who ate nuts, as compared with those who did not, were 0.89 [95% confidence interval (CI), 0.82-0.95] for the consumption of less than one serving of nuts per week, 0.75 (95% CI, 0.67-0.85) for one to less than three servings per week and 0.71 (95% CI, 0.58-0.86) for three or more servings per week (P < 0.001 for trend). Among specific causes, significant inverse associations were observed between nut consumption and deaths due to cardiovascular disease, all cancers and gastrointestinal cancers. Conclusions: This study provides evidence for an inverse association between nut consumption and mortality in a developing country, where nut consumption does not track with a healthy lifestyle. Further work is needed to establish the underlying mechanisms responsible for this association. PMID:26946539

Dynamic model inversion techniques for breath-by-breath measurement of carbon dioxide from low bandwidth sensors.

PubMed

Sivaramakrishnan, Shyam; Rajamani, Rajesh; Johnson, Bruce D

2009-01-01

Respiratory CO(2) measurement (capnography) is an important diagnosis tool that lacks inexpensive and wearable sensors. This paper develops techniques to enable use of inexpensive but slow CO(2) sensors for breath-by-breath tracking of CO(2) concentration. This is achieved by mathematically modeling the dynamic response and using model-inversion techniques to predict input CO(2) concentration from the slow-varying output. Experiments are designed to identify model-dynamics and extract relevant model-parameters for a solidstate room monitoring CO(2) sensor. A second-order model that accounts for flow through the sensor's filter and casing is found to be accurate in describing the sensor's slow response. The resulting estimate is compared with a standard-of-care respiratory CO(2) analyzer and shown to effectively track variation in breath-by-breath CO(2) concentration. This methodology is potentially useful for measuring fast-varying inputs to any slow sensor.

Movement decoupling control for two-axis fast steering mirror

NASA Astrophysics Data System (ADS)

Wang, Rui; Qiao, Yongming; Lv, Tao

2017-02-01

Based on flexure hinge and piezoelectric actuator of two-axis fast steering mirror is a complex system with time varying, uncertain and strong coupling. It is extremely difficult to achieve high precision decoupling control with the traditional PID control method. The feedback error learning method was established an inverse hysteresis model which was based inner product dynamic neural network nonlinear and no-smooth for piezo-ceramic. In order to improve the actuator high precision, a method was proposed, which was based piezo-ceramic inverse model of two dynamic neural network adaptive control. The experiment result indicated that, compared with two neural network adaptive movement decoupling control algorithm, static relative error is reduced from 4.44% to 0.30% and coupling degree is reduced from 12.71% to 0.60%, while dynamic relative error is reduced from 13.92% to 2.85% and coupling degree is reduced from 2.63% to 1.17%.

Predilution versus postdilution during continuous venovenous hemofiltration: a comparison of circuit thrombogenesis.

PubMed

de Pont, Anne-Cornélie J M; Bouman, Catherine S C; Bakhtiari, Kamran; Schaap, Marianne C L; Nieuwland, Rienk; Sturk, Augueste; Hutten, Barbara A; de Jonge, Evert; Vroom, Margreeth B; Meijers, Joost C M; Büller, Harry R

2006-01-01

During continuous venovenous hemofiltration, predilution can prolong circuit survival time, but the underlying mechanism has not been elucidated. The aim of the present study was to compare predilution with postdilution, with respect to circuit thrombogenesis. Eight critically ill patients were treated with both predilutional and postdilutional continuous venovenous hemofiltration in a crossover fashion. A filtration flow of 60 ml/min was used in both modes. We chose blood flows of 140 and 200 ml/min during predilution and postdilution, respectively, to keep the total flow through the hemofilter constant. Extracorporeal circuit pressures were measured hourly, and samples of blood and ultrafiltrate were collected at five different time points. Thrombin-antithrombin complexes and prothrombin fragments F1 + 2 were measured by ELISA, and platelet activation was assessed by flow cytometry. No signs of thrombin generation or platelet activation were found during either mode. During postdilution, baseline platelet count and maximal prefilter pressure had a linear relation, whereas both parameters were inversely related with circuit survival time. In summary, predilution and postdilution did not differ with respect to extracorporeal circuit thrombogenesis. During postdilution, baseline platelet count and maximal prefilter pressure were inversely related with circuit survival time.

A matrix-based approach to solving the inverse Frobenius-Perron problem using sequences of density functions of stochastically perturbed dynamical systems

NASA Astrophysics Data System (ADS)

Nie, Xiaokai; Coca, Daniel

2018-01-01

The paper introduces a matrix-based approach to estimate the unique one-dimensional discrete-time dynamical system that generated a given sequence of probability density functions whilst subjected to an additive stochastic perturbation with known density.

A matrix-based approach to solving the inverse Frobenius-Perron problem using sequences of density functions of stochastically perturbed dynamical systems.

PubMed

Nie, Xiaokai; Coca, Daniel

2018-01-01

The paper introduces a matrix-based approach to estimate the unique one-dimensional discrete-time dynamical system that generated a given sequence of probability density functions whilst subjected to an additive stochastic perturbation with known density.

Warthin tumor of the parotid gland: diagnostic value of MR imaging with histopathologic correlation.

PubMed

Ikeda, Mitsuaki; Motoori, Ken; Hanazawa, Toyoyuki; Nagai, Yuichiro; Yamamoto, Seiji; Ueda, Takuya; Funatsu, Hiroyuki; Ito, Hisao

2004-08-01

The purpose of our study was to describe the MR imaging appearance of Warthin tumors multiple MR imaging techniques and to interpret the difference in appearance from that of malignant parotid tumors. T1-weighted, T2-weighted, short inversion time inversion recovery, diffusion-weighted, and contrast-enhanced dynamic MR images of 19 Warthin tumors and 17 malignant parotid tumors were reviewed. MR imaging results were compared with those of pathologic analysis. Epithelial stromata and lymphoid tissue with slitlike small cysts in Warthin tumors showed early enhancement and a high washout rate (> or =30%) on dynamic contrast-enhanced images, and accumulations of complicated cysts showed early enhancement and a low washout ratio (< 30%). The areas containing complicated cysts showed high signal intensity on T1-weighted images, whereas some foci in those areas showed low signal intensity on short tau inversion recovery images. The mean minimum signal intensity ratios (SIRmin) of Warthin tumor on short tau inversion recovery (0.29 +/- 0.22 SD) (P < .01) and T2-weighted images (0.28 +/- 0.09) (P < .05) were significantly lower than those of malignant parotid tumors (0.53 +/- 0.19, 0.48 +/- 0.19). The average washout ratio of Warthin tumors (44.0 +/- 20.4%) was higher than that of malignant parotid tumors (11.9 +/- 11.6%). The mean apparent diffusion coefficient of Warthin tumors (0.96 +/- 0.13 x 10(-3)mm2/s) was significantly lower (P < .01) than that of malignant tumors (1.19 +/- 0.19 x 10(-3)mm2/s). Detecting hypointense areas of short tau inversion recovery and T2-weighted images or low apparent diffusion coefficient values on diffusion-weighted images was useful for predicting whether salivary gland tumors were Warthin tumors. The findings of the dynamic contrast-enhanced study also were useful.

Infrared thermography based studies on the effect of age on localized cold stress induced thermoregulation in human

NASA Astrophysics Data System (ADS)

Lahiri, B. B.; Bagavathiappan, S.; Nishanthi, K.; Mohanalakshmi, K.; Veni, L.; Saumya; Yacin, S. M.; Philip, John

2016-05-01

Thermoregulatory control of blood flow plays an important role in maintaining the human body temperature and it provides physiological resistance against extreme environmental thermal stresses. To understand the role of age on thermal signals from veins and the thermoregulatory mechanism, the dynamic variation of the vein temperature on the hands of 17 human subjects, under a localized cold stress, was studied using infrared thermography. It was observed that the vein temperature of the stimulated hand initially decreased with time up to a time interval (called 'inversion time'), which was attributed to the localized cutaneous vasoconstriction. Beyond inversion time, a rise in the vein temperature of the stimulated hand was observed. A shift in the inversion time to higher values was observed for the older subjects, which was attributed to the reduced efficiency and responsiveness of the cutaneous vasoconstriction mechanism in these subjects. Our studies indicated that the inversion time increased linearly with subject age with strong positive Pearson's correlation coefficient of 0.94. It was also observed that the contralateral symmetry in vasoconstriction was much lower in older subjects than the younger subjects. The absolute difference between the left and right inversion time varied between 11-118 s and 5-28 s for the older and younger subjects, respectively. Our study clearly demonstrated that infrared thermography is one of the most effective experimental tool for studying dynamic variation in vein pixel temperature under localized thermal stresses.

Decomposed direct matrix inversion for fast non-cartesian SENSE reconstructions.

PubMed

Qian, Yongxian; Zhang, Zhenghui; Wang, Yi; Boada, Fernando E

2006-08-01

A new k-space direct matrix inversion (DMI) method is proposed here to accelerate non-Cartesian SENSE reconstructions. In this method a global k-space matrix equation is established on basic MRI principles, and the inverse of the global encoding matrix is found from a set of local matrix equations by taking advantage of the small extension of k-space coil maps. The DMI algorithm's efficiency is achieved by reloading the precalculated global inverse when the coil maps and trajectories remain unchanged, such as in dynamic studies. Phantom and human subject experiments were performed on a 1.5T scanner with a standard four-channel phased-array cardiac coil. Interleaved spiral trajectories were used to collect fully sampled and undersampled 3D raw data. The equivalence of the global k-space matrix equation to its image-space version, was verified via conjugate gradient (CG) iterative algorithms on a 2x undersampled phantom and numerical-model data sets. When applied to the 2x undersampled phantom and human-subject raw data, the decomposed DMI method produced images with small errors (< or = 3.9%) relative to the reference images obtained from the fully-sampled data, at a rate of 2 s per slice (excluding 4 min for precalculating the global inverse at an image size of 256 x 256). The DMI method may be useful for noise evaluations in parallel coil designs, dynamic MRI, and 3D sodium MRI with fixed coils and trajectories. Copyright 2006 Wiley-Liss, Inc.

The impact of GPS receiver modifications and ionospheric activity on Swarm baseline determination

NASA Astrophysics Data System (ADS)

Mao, X.; Visser, P. N. A. M.; van den IJssel, J.

2018-05-01

The European Space Agency (ESA) Swarm mission is a satellite constellation launched on 22 November 2013 aiming at observing the Earth geomagnetic field and its temporal variations. The three identical satellites are equipped with high-precision dual-frequency Global Positioning System (GPS) receivers, which make the constellation an ideal test bed for baseline determination. From October 2014 to August 2016, a number of GPS receiver modifications and a new GPS Receiver Independent Exchange Format (RINEX) converter were implemented. Moreover, the on-board GPS receiver performance has been influenced by the ionospheric scintillations. The impact of these factors is assessed for baseline determination of the pendulum formation flying Swarm-A and -C satellites. In total 30 months of data - from 15 July 2014 to the end of 2016 - is analyzed. The assessment includes analysis of observation residuals, success rate of GPS carrier phase ambiguity fixing, a consistency check between the so-called kinematic and reduced-dynamic baseline solution, and validations of orbits by comparing with Satellite Laser Ranging (SLR) observations. External baseline solutions from The German Space Operations Center (GSOC) and Astronomisches Institut - Universität Bern (AIUB) are also included in the comparison. Results indicate that the GPS receiver modifications and RINEX converter changes are effective to improve the baseline determination. This research eventually shows a consistency level of 9.3/4.9/3.0 mm between kinematic and reduced-dynamic baselines in the radial/along-track/cross-track directions. On average 98.3% of the epochs have kinematic solutions. Consistency between TU Delft and external reduced-dynamic baseline solutions is at a level of 1 mm level in all directions.

Validity of the top-down approach of inverse dynamics analysis in fast and large rotational trunk movements.

PubMed

Iino, Yoichi; Kojima, Takeji

2012-08-01

This study investigated the validity of the top-down approach of inverse dynamics analysis in fast and large rotational movements of the trunk about three orthogonal axes of the pelvis for nine male collegiate students. The maximum angles of the upper trunk relative to the pelvis were approximately 47°, 49°, 32°, and 55° for lateral bending, flexion, extension, and axial rotation, respectively, with maximum angular velocities of 209°/s, 201°/s, 145°/s, and 288°/s, respectively. The pelvic moments about the axes during the movements were determined using the top-down and bottom-up approaches of inverse dynamics and compared between the two approaches. Three body segment inertial parameter sets were estimated using anthropometric data sets (Ae et al., Biomechanism 11, 1992; De Leva, J Biomech, 1996; Dumas et al., J Biomech, 2007). The root-mean-square errors of the moments and the absolute errors of the peaks of the moments were generally smaller than 10 N·m. The results suggest that the pelvic moment in motions involving fast and large trunk movements can be determined with a certain level of validity using the top-down approach in which the trunk is modeled as two or three rigid-link segments.

The effect of subtalar inversion/eversion on the dynamic function of the tibialis anterior, soleus, and gastrocnemius during the stance phase of gait.

PubMed

Wang, Ruoli; Gutierrez-Farewik, Elena M

2011-05-01

The purpose of this study was to determine how gait deviation in one plane (i.e. excessive subtalar inversion/eversion) can affect the dynamic function of the tibialis anterior, gastrocnemius, and soleus to accelerate the subtalar, ankle, knee and hip joints, as well as the body center of mass. Induced acceleration analysis was performed based on a subject-specific three-dimensional linkage model configured by stance phase gait data and driven by one unit of muscle force. Eight healthy adult subjects were examined in gait analysis. The subtalar inversion/eversion was modeled by offsetting up to 20° from the normal subtalar angle while other configurations remained unaltered. This study showed that the gastrocnemius, soleus and tibialis anterior generally functioned as their anatomical definition in normal gait, but counterintuitive function was occasionally found in the bi-articular gastrocnemius. The plantarflexors play important roles in the body support and forward progression. Excessive subtalar eversion was found to enlarge the plantarflexors and tibialis anterior's function. Induced acceleration analysis demonstrated its ability to isolate the contributions of individual muscle to a given factor, and as a means of studying effect of pathological gait on the dynamic muscle functions. Copyright © 2011 Elsevier B.V. All rights reserved.

Quantifying the value of information for uncertainty reduction in chemical EOR modeling

NASA Astrophysics Data System (ADS)

Leray, Sarah; Yeates, Christopher; Douarche, Frédéric; Roggero, Frédéric

2016-04-01

Reservoir modeling is a powerful tool to assess the technical and economic feasibility of chemical Enhanced Oil Recovery methods such as the joint injection of surfactant and polymer. Laboratory recovery experiments are usually undertaken on cores to understand recovery mechanisms and to estimate properties, that will be further used to build large scale models. To capture the different processes involved in chemical EOR, models are described by a large number of parameters which are basically only partially constrained by recovery experiments and additional characterizations, mainly because of cost and time restrictions or limited representativeness. Among the most uncertain properties, features the surfactant adsorption which cannot be straightforwardly derived from bulk or simplified dynamic measurements (e.g. single phase dynamic adsorption experiments). It is unfortunately critical for the economics of the process. Identifying the most informative observations (e.g. saturation scans, pressure differential, surfactant production, oil recovery) is of primary interest to compensate deficiency of some characterizations and improve models robustness and their predictive capability. Building a consistent set of recovery experiments that will allow to seize recovery mechanisms is critical as well. To address these inverse methodology issues, we create a synthetic numerical model with a well-defined set of parameter values, considered to be our reference case. This choice of model is based on a similar real data set and a broad literature review. It consists of a water-wet sandstone subject to typical surfactant-polymer injections. We first study the effect of a salinity gradient injected after a surfactant-polymer slug, as it is known to significantly improve oil recovery. We show that reaching optimal conditions of salinity gradient is a fragile balance between surfactant desorption and interfacial tension increase. This high dependence on surfactant adsorption properties indicates that two recovery tests with and without salinity gradient are of great interest for model inversion and characterization of surfactant adsorption. Second, we analyze our capacity to find again the reference model using an assisted history matching method to reproduce a set of synthetic core-scale experiments. To do so, we use the reference model over five configurations with respect to chemicals injection to provide baseline recovery data. Then, we consider some uncertainty on model parameters, regarding surfactant adsorption properties amongst others, leading to a total of twelve uncertain parameters. Finally, we extensively explore the parameter space to find several reasonable matches. We show that an additional sixth recovery experiment is necessary to fully constrain the model, and specifically characterize surfactant adsorption. We besides show that production data are not equally informative: pressure differential is for instance the less informative data while a saturation scan at the end of the polymer post-flush can greatly help in the inversion. The inverse methodology carried out here has also been successfully tested with a real set of coreflood experiments.

Chromium exposure and incidence of metabolic syndrome among American young adults over a 23-year follow-up: the CARDIA Trace Element Study

PubMed Central

Bai, Jianling; Xun, Pengcheng; Morris, Steve; Jacobs, David R.; Liu, Kiang; He, Ka

2015-01-01

Studies suggest that chromium deficiency is associated with elevated levels of fasting blood glucose, circulating insulin, cholesterol and triglycerides, and decreased proportion of lean body mass. However, data directly relating chromium levels to metabolic syndrome (MetS) risk are lacking. A total of 3,648 American adults from the Coronary Artery Risk Development in Young Adults (CARDIA) study, aged 20–32 years, were prospectively examined for the incidence of MetS and its five components from 1987–88 to 2010–11. Baseline toenail chromium levels were measured with instrumental neutron-activation analysis. Incident MetS was defined by the NCEP-ATP III criteria. During the 23-year follow-up, 878 incident MetS cases were identified. Baseline toenail chromium was inversely associated with incidence of MetS as well as its blood lipid components. The multivariable-adjusted hazard ratio (HR) (95% confidence interval [CI]) of MetS comparing the highest to the lowest quartiles of toenail chromium levels was 0.80 (0.66–0.98; Plinear trend = 0.006). The adjusted HRs were 0.82 (0.68–0.98; Ptrend = 0.045) for having abnormal triglycerides levels and 0.75 (0.64–0.88; Ptrend  = 0.030) for having abnormal HDL cholesterol levels. Toenail chromium levels were inversely and longitudinally associated with incidence of MetS in American young adults. This inverse association was mainly explained by its relation to blood lipids. PMID:26489690

Inverse association between soya food consumption and insulin resistance in Japanese adults.

PubMed

Nakamoto, Mariko; Uemura, Hirokazu; Sakai, Tohru; Katsuura-Kamano, Sakurako; Yamaguchi, Miwa; Hiyoshi, Mineyoshi; Arisawa, Kokichi

2015-08-01

The purpose of the present study was to examine the association between soya food consumption and insulin resistance using baseline data of the Japan Multi-Institutional Collaborative Cohort (J-MICC) Study in Tokushima, Japan. This cross-sectional study included 1274 subjects, aged 34-70 years at baseline, living in Tokushima Prefecture between 2008 and 2013. Fasting blood samples were collected and information on lifestyle characteristics including soya food intake and medical history were obtained using a structured self-administered questionnaire. The homeostasis model assessment of insulin resistance (HOMA-IR) was measured and those with HOMA-IR ≥ 2.5 were defined as having insulin resistance. Multiple logistic regression models were used to analyse the association between soya product intake and the prevalence of insulin resistance. Rural communities located in Tokushima Prefecture, Japan, between 2008 and 2013. A total of 1148 adults (565 men and 583 women), aged 34-70 years. The frequency of intake of miso soup, total non-fried soya products and total soya products showed significant inverse dose-response relationships with insulin resistance, after adjustments for potential confounders. When soya product intake was calculated as soya protein and isoflavone, the odds ratios of insulin resistance decreased significantly as the estimated intake of soya protein increased. Furthermore, significant inverse dose-response relationships were observed for total non-fried soya products and total soya products, after adjustment for total vegetable or total fibre consumption. The present results indicate that the intake of soya products and non-fried soya products is associated with reduced insulin resistance in the Japanese population.

Reducing the risk of falls through proprioceptive dynamic posture training in osteoporotic women with kyphotic posturing: a randomized pilot study.

PubMed

Sinaki, Mehrsheed; Lynn, Susan G

2002-04-01

To assess the effect of a proprioceptive dynamic posture training program on balance in osteoporotic women with kyphotic posture. Subjects were randomly assigned to either a proprioceptive dynamic posture training program or exercise only group. Anthropometric measurements, muscle strength, level of physical activity, computerized dynamic posturography, and spine radiography were performed at baseline and 1 mo. At the 1-mo follow-up, three groups were formed on the basis of the baseline computerized dynamic posturography results. In general, groups 1 and 2 had no significant change at 1 mo, whereas group 3 improved balance significantly at 1 mo. The subjects who had abnormal balance and used the proprioceptive dynamic posture training program had the most significant improvement in balance. Improved balance could reduce the risk of falls.

A novel approach to locomotion learning: Actor-Critic architecture using central pattern generators and dynamic motor primitives.

PubMed

Li, Cai; Lowe, Robert; Ziemke, Tom

2014-01-01

In this article, we propose an architecture of a bio-inspired controller that addresses the problem of learning different locomotion gaits for different robot morphologies. The modeling objective is split into two: baseline motion modeling and dynamics adaptation. Baseline motion modeling aims to achieve fundamental functions of a certain type of locomotion and dynamics adaptation provides a "reshaping" function for adapting the baseline motion to desired motion. Based on this assumption, a three-layer architecture is developed using central pattern generators (CPGs, a bio-inspired locomotor center for the baseline motion) and dynamic motor primitives (DMPs, a model with universal "reshaping" functions). In this article, we use this architecture with the actor-critic algorithms for finding a good "reshaping" function. In order to demonstrate the learning power of the actor-critic based architecture, we tested it on two experiments: (1) learning to crawl on a humanoid and, (2) learning to gallop on a puppy robot. Two types of actor-critic algorithms (policy search and policy gradient) are compared in order to evaluate the advantages and disadvantages of different actor-critic based learning algorithms for different morphologies. Finally, based on the analysis of the experimental results, a generic view/architecture for locomotion learning is discussed in the conclusion.

A novel approach to locomotion learning: Actor-Critic architecture using central pattern generators and dynamic motor primitives

PubMed Central

Li, Cai; Lowe, Robert; Ziemke, Tom

2014-01-01

In this article, we propose an architecture of a bio-inspired controller that addresses the problem of learning different locomotion gaits for different robot morphologies. The modeling objective is split into two: baseline motion modeling and dynamics adaptation. Baseline motion modeling aims to achieve fundamental functions of a certain type of locomotion and dynamics adaptation provides a “reshaping” function for adapting the baseline motion to desired motion. Based on this assumption, a three-layer architecture is developed using central pattern generators (CPGs, a bio-inspired locomotor center for the baseline motion) and dynamic motor primitives (DMPs, a model with universal “reshaping” functions). In this article, we use this architecture with the actor-critic algorithms for finding a good “reshaping” function. In order to demonstrate the learning power of the actor-critic based architecture, we tested it on two experiments: (1) learning to crawl on a humanoid and, (2) learning to gallop on a puppy robot. Two types of actor-critic algorithms (policy search and policy gradient) are compared in order to evaluate the advantages and disadvantages of different actor-critic based learning algorithms for different morphologies. Finally, based on the analysis of the experimental results, a generic view/architecture for locomotion learning is discussed in the conclusion. PMID:25324773

Stability analysis of an implicitly defined labor market model

NASA Astrophysics Data System (ADS)

Mendes, Diana A.; Mendes, Vivaldo M.

2008-06-01

Until very recently, the pervasive existence of models exhibiting well-defined backward dynamics but ill-defined forward dynamics in economics and finance has apparently posed no serious obstacles to the analysis of their dynamics and stability, despite the problems that may arise from possible erroneous conclusions regarding theoretical considerations and policy prescriptions from such models. A large number of papers have dealt with this problem in the past by assuming the existence of symmetry between forward and backward dynamics, even in the case when the map cannot be invertible either forward or backwards. However, this procedure has been seriously questioned over the last few years in a series of papers dealing with implicit difference equations and inverse limit spaces. This paper explores the search and matching labor market model developed by Bhattacharya and Bunzel [J. Bhattacharya, H. Bunzel, Chaotic Planning Solution in the Textbook Model of Equilibrium Labor Market Search and Matching, Mimeo, Iowa State University, 2002; J. Bhattacharya, H. Bunzel, Economics Bulletin 5 (19) (2003) 1-10], with the following objectives in mind: (i) to show that chaotic dynamics may still be present in the model for acceptable parameter values, (ii) to clarify some open questions related with the admissible dynamics in the forward looking setting, by providing a rigorous proof of the existence of cyclic and chaotic dynamics through the application of tools from symbolic dynamics and inverse limit theory.

Recursive mass matrix factorization and inversion: An operator approach to open- and closed-chain multibody dynamics

NASA Technical Reports Server (NTRS)

Rodriguez, G.; Kreutz, K.

1988-01-01

This report advances a linear operator approach for analyzing the dynamics of systems of joint-connected rigid bodies.It is established that the mass matrix M for such a system can be factored as M=(I+H phi L)D(I+H phi L) sup T. This yields an immediate inversion M sup -1=(I-H psi L) sup T D sup -1 (I-H psi L), where H and phi are given by known link geometric parameters, and L, psi and D are obtained recursively by a spatial discrete-step Kalman filter and by the corresponding Riccati equation associated with this filter. The factors (I+H phi L) and (I-H psi L) are lower triangular matrices which are inverses of each other, and D is a diagonal matrix. This factorization and inversion of the mass matrix leads to recursive algortihms for forward dynamics based on spatially recursive filtering and smoothing. The primary motivation for advancing the operator approach is to provide a better means to formulate, analyze and understand spatial recursions in multibody dynamics. This is achieved because the linear operator notation allows manipulation of the equations of motion using a very high-level analytical framework (a spatial operator algebra) that is easy to understand and use. Detailed lower-level recursive algorithms can readily be obtained for inspection from the expressions involving spatial operators. The report consists of two main sections. In Part 1, the problem of serial chain manipulators is analyzed and solved. Extensions to a closed-chain system formed by multiple manipulators moving a common task object are contained in Part 2. To retain ease of exposition in the report, only these two types of multibody systems are considered. However, the same methods can be easily applied to arbitrary multibody systems formed by a collection of joint-connected regid bodies.

Thermal Diagnostics with the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory: A Validated Method for Differential Emission Measure Inversions

NASA Astrophysics Data System (ADS)

Cheung, Mark C. M.; Boerner, P.; Schrijver, C. J.; Testa, P.; Chen, F.; Peter, H.; Malanushenko, A.

2015-07-01

We present a new method for performing differential emission measure (DEM) inversions on narrow-band EUV images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. The method yields positive definite DEM solutions by solving a linear program. This method has been validated against a diverse set of thermal models of varying complexity and realism. These include (1) idealized Gaussian DEM distributions, (2) 3D models of NOAA Active Region 11158 comprising quasi-steady loop atmospheres in a nonlinear force-free field, and (3) thermodynamic models from a fully compressible, 3D MHD simulation of active region (AR) corona formation following magnetic flux emergence. We then present results from the application of the method to AIA observations of Active Region 11158, comparing the region's thermal structure on two successive solar rotations. Additionally, we show how the DEM inversion method can be adapted to simultaneously invert AIA and Hinode X-ray Telescope data, and how supplementing AIA data with the latter improves the inversion result. The speed of the method allows for routine production of DEM maps, thus facilitating science studies that require tracking of the thermal structure of the solar corona in time and space.

Frequency swept microwaves for hyperfine decoupling and time domain dynamic nuclear polarization

PubMed Central

Hoff, Daniel E.M.; Albert, Brice J.; Saliba, Edward P.; Scott, Faith J.; Choi, Eric J.; Mardini, Michael; Barnes, Alexander B.

2015-01-01

Hyperfine decoupling and pulsed dynamic nuclear polarization (DNP) are promising techniques to improve high field DNP NMR. We explore experimental and theoretical considerations to implement them with magic angle spinning (MAS). Microwave field simulations using the high frequency structural simulator (HFSS) software suite are performed to characterize the inhomogeneous phase independent microwave field throughout a 198 GHz MAS DNP probe. Our calculations show that a microwave power input of 17 W is required to generate an average EPR nutation frequency of 0.84 MHz. We also present a detailed calculation of microwave heating from the HFSS parameters and find that 7.1% of the incident microwave power contributes to dielectric sample heating. Voltage tunable gyrotron oscillators are proposed as a class of frequency agile microwave sources to generate microwave frequency sweeps required for the frequency modulated cross effect, electron spin inversions, and hyperfine decoupling. Electron spin inversions of stable organic radicals are simulated with SPINEVOLUTION using the inhomogeneous microwave fields calculated by HFSS. We calculate an electron spin inversion efficiency of 56% at a spinning frequency of 5 kHz. Finally, we demonstrate gyrotron acceleration potentials required to generate swept microwave frequency profiles for the frequency modulated cross effect and electron spin inversions. PMID:26482131

THERMAL DIAGNOSTICS WITH THE ATMOSPHERIC IMAGING ASSEMBLY ON BOARD THE SOLAR DYNAMICS OBSERVATORY: A VALIDATED METHOD FOR DIFFERENTIAL EMISSION MEASURE INVERSIONS

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

Cheung, Mark C. M.; Boerner, P.; Schrijver, C. J.

We present a new method for performing differential emission measure (DEM) inversions on narrow-band EUV images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. The method yields positive definite DEM solutions by solving a linear program. This method has been validated against a diverse set of thermal models of varying complexity and realism. These include (1) idealized Gaussian DEM distributions, (2) 3D models of NOAA Active Region 11158 comprising quasi-steady loop atmospheres in a nonlinear force-free field, and (3) thermodynamic models from a fully compressible, 3D MHD simulation of active region (AR) corona formation following magneticmore » flux emergence. We then present results from the application of the method to AIA observations of Active Region 11158, comparing the region's thermal structure on two successive solar rotations. Additionally, we show how the DEM inversion method can be adapted to simultaneously invert AIA and Hinode X-ray Telescope data, and how supplementing AIA data with the latter improves the inversion result. The speed of the method allows for routine production of DEM maps, thus facilitating science studies that require tracking of the thermal structure of the solar corona in time and space.« less

Frequency swept microwaves for hyperfine decoupling and time domain dynamic nuclear polarization.

PubMed

Hoff, Daniel E M; Albert, Brice J; Saliba, Edward P; Scott, Faith J; Choi, Eric J; Mardini, Michael; Barnes, Alexander B

2015-11-01

Hyperfine decoupling and pulsed dynamic nuclear polarization (DNP) are promising techniques to improve high field DNP NMR. We explore experimental and theoretical considerations to implement them with magic angle spinning (MAS). Microwave field simulations using the high frequency structural simulator (HFSS) software suite are performed to characterize the inhomogeneous phase independent microwave field throughout a 198GHz MAS DNP probe. Our calculations show that a microwave power input of 17W is required to generate an average EPR nutation frequency of 0.84MHz. We also present a detailed calculation of microwave heating from the HFSS parameters and find that 7.1% of the incident microwave power contributes to dielectric sample heating. Voltage tunable gyrotron oscillators are proposed as a class of frequency agile microwave sources to generate microwave frequency sweeps required for the frequency modulated cross effect, electron spin inversions, and hyperfine decoupling. Electron spin inversions of stable organic radicals are simulated with SPINEVOLUTION using the inhomogeneous microwave fields calculated by HFSS. We calculate an electron spin inversion efficiency of 56% at a spinning frequency of 5kHz. Finally, we demonstrate gyrotron acceleration potentials required to generate swept microwave frequency profiles for the frequency modulated cross effect and electron spin inversions. Copyright © 2015 Elsevier Inc. All rights reserved.

Formation and Development of the Dynamic Stall Vortex on a Wing with Leading Edge Tubercles

NASA Astrophysics Data System (ADS)

Hrynuk, John; Bohl, Douglas

2015-11-01

Humpback whales are unique in that their flippers have leading edge ``bumps'' or tubercles. Past work on airfoils inspired by whale flippers has centered on the static aerodynamic characteristics of these airfoils. The current study uses Molecular Tagging Velocimetry (MTV) to investigate the effects of tubercles on dynamically pitching NACA 0012 airfoils. A baseline (i.e. straight leading edge) wing and one modified with leading edge tubercles are investigated. Tracking of the Dynamic Stall Vortex (DSV) is performed to quantitatively compare the DSV formation location, path, and convective velocity for tubercled and baseline wings. The results show that there is a spanwise variation in the initial formation location and motion of the DSV on the modified wing. Once formed, the DSV aligns into a more uniform spanwise structure. As the pitching motion progresses, the DSV on the modified wing convects away from the airfoil surface later and slower than is observed for the baseline airfoil. The results indicate that the tubercles may delay stall when compared to the baseline airfoil. This work was supported by NSF Grant # 0845882.

Enhanced GPS-based GRACE baseline determination by using a new strategy for ambiguity resolution and relative phase center variation corrections

NASA Astrophysics Data System (ADS)

Gu, Defeng; Ju, Bing; Liu, Junhong; Tu, Jia

2017-09-01

Precise relative position determination is a prerequisite for radar interferometry by formation flying satellites. It has been shown that this can be achieved by high-quality, dual-frequency GPS receivers that provide precise carrier-phase observations. The precise baseline determination between satellites flying in formation can significantly improve the accuracy of interferometric products, and has become a research interest. The key technologies of baseline determination using spaceborne dual-frequency GPS for gravity recovery and climate experiment (GRACE) formation are presented, including zero-difference (ZD) reduced dynamic orbit determination, double-difference (DD) reduced dynamic relative orbit determination, integer ambiguity resolution and relative receiver antenna phase center variation (PCV) estimation. We propose an independent baseline determination method based on a new strategy of integer ambiguity resolution and correction of relative receiver antenna PCVs, and implement the method in the NUDTTK software package. The algorithms have been tested using flight data over a period of 120 days from GRACE. With the original strategy of integer ambiguity resolution based on Melbourne-Wübbena (M-W) combinations, the average success rate is 85.6%, and the baseline precision is 1.13 mm. With the new strategy of integer ambiguity resolution based on a priori relative orbit, the average success rate and baseline precision are improved by 5.8% and 0.11 mm respectively. A relative ionosphere-free phase pattern estimation result is given in this study, and with correction of relative receiver antenna PCVs, the baseline precision is further significantly improved by 0.34 mm. For ZD reduced dynamic orbit determination, the orbit precision for each GRACE satellite A or B in three dimensions (3D) is about 2.5 cm compared to Jet Propulsion Laboratory (JPL) post science orbits. For DD reduced dynamic relative orbit determination, the final baseline precision for two GRACE satellites formation is 0.68 mm validated by K-Band Ranging (KBR) observations, and average ambiguity success rate of about 91.4% could be achieved.

Interplay between dewetting and layer inversion in poly(4-vinylpyridine)/polystyrene bilayers.

PubMed

Thickett, Stuart C; Harris, Andrew; Neto, Chiara

2010-10-19

We investigated the morphology and dynamics of the dewetting of metastable poly(4-vinylpyridine) (P4VP) thin films situated on top of polystyrene (PS) thin films as a function of the molecular weight and thickness of both films. We focused on the competition between the dewetting process, occurring as a result of unfavorable intermolecular interactions at the P4VP/PS interface, and layer inversion due to the lower surface energy of PS. By means of optical and atomic force microscopy (AFM), we observed how both the dynamics of the instability and the morphology of the emerging patterns depend on the ratio of the molecular weights of the polymer films. When the bottom PS layer was less viscous than the top P4VP layer (liquid-liquid dewetting), nucleated holes in the P4VP film typically stopped growing at long annealing times because of a combination of viscous dissipation in the bottom layer and partial layer inversion. Full layer inversion was achieved when the viscosity of the top P4VP layer was significantly greater (>10⁴) than the viscosity of the PS layer underneath, which is attributed to strongly different mobilities of the two layers. The density of holes produced by nucleation dewetting was observed for the first time to depend on the thickness of the top film as well as the polymer molecular weight. The final (completely dewetted) morphology of isolated droplets could be achieved only if the time frame of layer inversion was significantly slower than that of dewetting, which was characteristic of high-viscosity PS underlayers that allowed dewetting to fall into a liquid-solid regime. Assuming a simple reptation model for layer inversion occurring at the dewetting front, the observed surface morphologies could be predicted on the basis of the relative rates of dewetting and layer inversion.

A mesostate-space model for EEG and MEG.

PubMed

Daunizeau, Jean; Friston, Karl J

2007-10-15

We present a multi-scale generative model for EEG, that entails a minimum number of assumptions about evoked brain responses, namely: (1) bioelectric activity is generated by a set of distributed sources, (2) the dynamics of these sources can be modelled as random fluctuations about a small number of mesostates, (3) mesostates evolve in a temporal structured way and are functionally connected (i.e. influence each other), and (4) the number of mesostates engaged by a cognitive task is small (e.g. between one and a few). A Variational Bayesian learning scheme is described that furnishes the posterior density on the models parameters and its evidence. Since the number of meso-sources specifies the model, the model evidence can be used to compare models and find the optimum number of meso-sources. In addition to estimating the dynamics at each cortical dipole, the mesostate-space model and its inversion provide a description of brain activity at the level of the mesostates (i.e. in terms of the dynamics of meso-sources that are distributed over dipoles). The inclusion of a mesostate level allows one to compute posterior probability maps of each dipole being active (i.e. belonging to an active mesostate). Critically, this model accommodates constraints on the number of meso-sources, while retaining the flexibility of distributed source models in explaining data. In short, it bridges the gap between standard distributed and equivalent current dipole models. Furthermore, because it is explicitly spatiotemporal, the model can embed any stochastic dynamical causal model (e.g. a neural mass model) as a Markov process prior on the mesostate dynamics. The approach is evaluated and compared to standard inverse EEG techniques, using synthetic data and real data. The results demonstrate the added-value of the mesostate-space model and its variational inversion.

A dynamic processes study of PM retention by trees under different wind conditions.

PubMed

Xie, Changkun; Kan, Liyan; Guo, Jiankang; Jin, Sijia; Li, Zhigang; Chen, Dan; Li, Xin; Che, Shengquan

2018-02-01

Particulate matter (PM) is one of the most serious environmental problems, exacerbating respiratory and vascular illnesses. Plants have the ability to reduce non-point source PM pollution through retention on leaves and branches. Studies of the dynamic processes of PM retention by plants and the mechanisms influencing this process will help to improve the efficiency of urban greening for PM reduction. We examined dynamic processes of PM retention and the major factors influencing PM retention by six trees with different branch structure characteristics in wind tunnel experiments at three different wind speeds. The results showed that the changes of PM numbers retained by plant leaves over time were complex dynamic processes for which maximum values could exceed minimum values by over 10 times. The average value of PM measured in multiple periods and situations can be considered a reliable indicator of the ability of the plant to retain PM. The dynamic processes were similar for PM 10 and PM 2.5 . They could be clustered into three groups simulated by continually-rising, inverse U-shaped, and U-shaped polynomial functions, respectively. The processes were the synthetic effect of characteristics such as species, wind speed, period of exposure and their interactions. Continually-rising functions always explained PM retention in species with extremely complex branch structure. Inverse U-shaped processes explained PM retention in species with relatively simple branch structure and gentle wind. The U-shaped processes mainly explained PM retention at high wind speeds and in species with a relatively simple crown. These results indicate that using plants with complex crowns in urban greening and decreasing wind speed in plant communities increases the chance of continually-rising or inverse U-shaped relationships, which have a positive effect in reducing PM pollution. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Bayesian methodological framework for accommodating interannual variability of nutrient loading with the SPARROW model

NASA Astrophysics Data System (ADS)

Wellen, Christopher; Arhonditsis, George B.; Labencki, Tanya; Boyd, Duncan

2012-10-01

Regression-type, hybrid empirical/process-based models (e.g., SPARROW, PolFlow) have assumed a prominent role in efforts to estimate the sources and transport of nutrient pollution at river basin scales. However, almost no attempts have been made to explicitly accommodate interannual nutrient loading variability in their structure, despite empirical and theoretical evidence indicating that the associated source/sink processes are quite variable at annual timescales. In this study, we present two methodological approaches to accommodate interannual variability with the Spatially Referenced Regressions on Watershed attributes (SPARROW) nonlinear regression model. The first strategy uses the SPARROW model to estimate a static baseline load and climatic variables (e.g., precipitation) to drive the interannual variability. The second approach allows the source/sink processes within the SPARROW model to vary at annual timescales using dynamic parameter estimation techniques akin to those used in dynamic linear models. Model parameterization is founded upon Bayesian inference techniques that explicitly consider calibration data and model uncertainty. Our case study is the Hamilton Harbor watershed, a mixed agricultural and urban residential area located at the western end of Lake Ontario, Canada. Our analysis suggests that dynamic parameter estimation is the more parsimonious of the two strategies tested and can offer insights into the temporal structural changes associated with watershed functioning. Consistent with empirical and theoretical work, model estimated annual in-stream attenuation rates varied inversely with annual discharge. Estimated phosphorus source areas were concentrated near the receiving water body during years of high in-stream attenuation and dispersed along the main stems of the streams during years of low attenuation, suggesting that nutrient source areas are subject to interannual variability.

Biotic responses buffer warming-induced soil organic carbon loss in Arctic tundra.

PubMed

Liang, Junyi; Xia, Jiangyang; Shi, Zheng; Jiang, Lifen; Ma, Shuang; Lu, Xingjie; Mauritz, Marguerite; Natali, Susan M; Pegoraro, Elaine; Penton, C Ryan; Plaza, César; Salmon, Verity G; Celis, Gerardo; Cole, James R; Konstantinidis, Konstantinos T; Tiedje, James M; Zhou, Jizhong; Schuur, Edward A G; Luo, Yiqi

2018-05-26

Climate warming can result in both abiotic (e.g., permafrost thaw) and biotic (e.g., microbial functional genes) changes in Arctic tundra. Recent research has incorporated dynamic permafrost thaw in Earth system models (ESMs) and indicates that Arctic tundra could be a significant future carbon (C) source due to the enhanced decomposition of thawed deep soil C. However, warming-induced biotic changes may influence biologically related parameters and the consequent projections in ESMs. How model parameters associated with biotic responses will change under warming and to what extent these changes affect projected C budgets have not been carefully examined. In this study, we synthesized six data sets over five years from a soil warming experiment at the Eight Mile Lake, Alaska, into the Terrestrial ECOsystem (TECO) model with a probabilistic inversion approach. The TECO model used multiple soil layers to track dynamics of thawed soil under different treatments. Our results show that warming increased light use efficiency of vegetation photosynthesis but decreased baseline (i.e., environment-corrected) turnover rates of SOC in both the fast and slow pools in comparison with those under control. Moreover, the parameter changes generally amplified over time, suggesting processes of gradual physiological acclimation and functional gene shifts of both plants and microbes. The TECO model predicted that field warming from 2009 to 2013 resulted in cumulative C losses of 224 or 87 g m -2 , respectively, without or with changes in those parameters. Thus, warming-induced parameter changes reduced predicted soil C loss by 61%. Our study suggests that it is critical to incorporate biotic changes in ESMs to improve the model performance in predicting C dynamics in permafrost regions. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Proposed satellite laser ranging and very long baseline interferometry sites for crustal dynamics investigations

NASA Technical Reports Server (NTRS)

Lowman, P. D.; Allenby, R. J.; Frey, H. V.

1979-01-01

Recommendations are presented for a global network of 125 sites for geodetic measurements by satellite laser ranging and very long baseline interferometry. The sites were proposed on the basis of existing facilities and scientific value for investigation of crustal dynamics as related to earthquake hazards. Tectonic problems are discussed for North America peripheral regions and for the world. The sites are presented in tables and maps, with bibliographic references.

Solving of the coefficient inverse problems for a nonlinear singularly perturbed reaction-diffusion-advection equation with the final time data

NASA Astrophysics Data System (ADS)

Lukyanenko, D. V.; Shishlenin, M. A.; Volkov, V. T.

2018-01-01

We propose the numerical method for solving coefficient inverse problem for a nonlinear singularly perturbed reaction-diffusion-advection equation with the final time observation data based on the asymptotic analysis and the gradient method. Asymptotic analysis allows us to extract a priory information about interior layer (moving front), which appears in the direct problem, and boundary layers, which appear in the conjugate problem. We describe and implement the method of constructing a dynamically adapted mesh based on this a priory information. The dynamically adapted mesh significantly reduces the complexity of the numerical calculations and improve the numerical stability in comparison with the usual approaches. Numerical example shows the effectiveness of the proposed method.

Trajectory optimization for the National Aerospace Plane

NASA Technical Reports Server (NTRS)

Lu, Ping

1992-01-01

The primary objective of this research is to develop an efficient and robust trajectory optimization tool for the optimal ascent problem of the National Aerospace Plane (NASP). This report is organized in the following order to summarize the complete work: Section two states the formulation and models of the trajectory optimization problem. An inverse dynamics approach to the problem is introduced in Section three. Optimal trajectories corresponding to various conditions and performance parameters are presented in Section four. A midcourse nonlinear feedback controller is developed in Section five. Section six demonstrates the performance of the inverse dynamics approach and midcourse controller during disturbances. Section seven discusses rocket assisted ascent which may be beneficial when orbital altitude is high. Finally, Section eight recommends areas of future research.

Constraints on Pacific plate kinematics and dynamics with global positioning system measurements

NASA Technical Reports Server (NTRS)

Dixon, T. H.; Golombek, M. P.; Thornton, C. L.

1985-01-01

A measurement program designed to investigate kinematic and dynamic aspects of plate tectonics in the Pacific region by means of satellite observations is proposed. Accuracy studies are summarized showing that for short baselines (less than 100 km), the measuring accuracy of global positioning system (GPS) receivers can be in the centimeter range. For longer baselines, uncertainty in the orbital ephemerides of the GPS satellites could be a major source of error. Simultaneous observations at widely (about 300 km) separated fiducial stations over the Pacific region, should permit an accuracy in the centimeter range for baselines of up to several thousand kilometers. The optimum performance level is based on the assumption of that fiducial baselines are known a priori to the centimeter range. An example fiducial network for a GPS study of the South Pacific region is described.

Baseline estimation from simultaneous satellite laser tracking

NASA Technical Reports Server (NTRS)

Dedes, George C.

1987-01-01

Simultaneous Range Differences (SRDs) to Lageos are obtained by dividing the observing stations into pairs with quasi-simultaneous observations. For each of those pairs the station with the least number of observations is identified, and at its observing epochs interpolated ranges for the alternate station are generated. The SRD observables are obtained by subtracting the actually observed laser range of the station having the least number of observations from the interpolated ranges of the alternate station. On the basis of these observables semidynamic single baseline solutions were performed. The aim of these solutions is to further develop and implement the SRD method in the real data environment, to assess its accuracy, its advantages and disadvantages as related to the range dynamic mode methods, when the baselines are the only parameters of interest. Baselines, using simultaneous laser range observations to Lageos, were also estimated through the purely geometric method. These baselines formed the standards the standards of comparison in the accuracy assessment of the SRD method when compared to that of the range dynamic mode methods. On the basis of this comparison it was concluded that for baselines of regional extent the SRD method is very effective, efficient, and at least as accurate as the range dynamic mode methods, and that on the basis of a simple orbital modeling and a limited orbit adjustment. The SRD method is insensitive to the inconsistencies affecting the terrestrial reference frame and simultaneous adjustment of the Earth Rotation Parameters (ERPs) is not necessary.

Dynamical inversion of the energy landscape promotes non-equilibrium self-assembly of binary mixtures

DOE PAGES

Pestana, Luis Ruiz; Minnetian, Natalie; Lammers, Laura Nielsen; ...

2018-01-02

When driven out of equilibrium, many diverse systems can form complex spatial and dynamical patterns, even in the absence of attractive interactions. Using kinetic Monte Carlo simulations, we investigate the phase behavior of a binary system of particles of dissimilar size confined between semiflexible planar surfaces, in which the nanoconfinement introduces a non-local coupling between particles, which we model as an activation energy barrier to diffusion that decreases with the local fraction of the larger particle. The system autonomously reaches a cyclical non-equilibrium state characterized by the formation and dissolution of metastable micelle-like clusters with the small particles in themore » core and the large ones in the surrounding corona. The power spectrum of the fluctuations in the aggregation number exhibits 1/f noise reminiscent of self-organized critical systems. Finally, we suggest that the dynamical metastability of the micellar structures arises from an inversion of the energy landscape, in which the relaxation dynamics of one of the species induces a metastable phase for the other species.« less

Dynamical inversion of the energy landscape promotes non-equilibrium self-assembly of binary mixtures

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

Pestana, Luis Ruiz; Minnetian, Natalie; Lammers, Laura Nielsen

When driven out of equilibrium, many diverse systems can form complex spatial and dynamical patterns, even in the absence of attractive interactions. Using kinetic Monte Carlo simulations, we investigate the phase behavior of a binary system of particles of dissimilar size confined between semiflexible planar surfaces, in which the nanoconfinement introduces a non-local coupling between particles, which we model as an activation energy barrier to diffusion that decreases with the local fraction of the larger particle. The system autonomously reaches a cyclical non-equilibrium state characterized by the formation and dissolution of metastable micelle-like clusters with the small particles in themore » core and the large ones in the surrounding corona. The power spectrum of the fluctuations in the aggregation number exhibits 1/f noise reminiscent of self-organized critical systems. Finally, we suggest that the dynamical metastability of the micellar structures arises from an inversion of the energy landscape, in which the relaxation dynamics of one of the species induces a metastable phase for the other species.« less

Large-baseline InSAR for precise topographic mapping: a framework for TanDEM-X large-baseline data

NASA Astrophysics Data System (ADS)

Pinheiro, Muriel; Reigber, Andreas; Moreira, Alberto

2017-09-01

The global Digital Elevation Model (DEM) resulting from the TanDEM-X mission provides information about the world topography with outstanding precision. In fact, performance analysis carried out with the already available data have shown that the global product is well within the requirements of 10 m absolute vertical accuracy and 2 m relative vertical accuracy for flat to moderate terrain. The mission's science phase took place from October 2014 to December 2015. During this phase, bistatic acquisitions with across-track separation between the two satellites up to 3.6 km at the equator were commanded. Since the relative vertical accuracy of InSAR derived elevation models is, in principle, inversely proportional to the system baseline, the TanDEM-X science phase opened the doors for the generation of elevation models with improved quality with respect to the standard product. However, the interferometric processing of the large-baseline data is troublesome due to the increased volume decorrelation and very high frequency of the phase variations. Hence, in order to fully profit from the increased baseline, sophisticated algorithms for the interferometric processing, and, in particular, for the phase unwrapping have to be considered. This paper proposes a novel dual-baseline region-growing framework for the phase unwrapping of the large-baseline interferograms. Results from two experiments with data from the TanDEM-X science phase are discussed, corroborating the expected increased level of detail of the large-baseline DEMs.

Characterization of six human disease-associated inversion polymorphisms.

PubMed

Antonacci, Francesca; Kidd, Jeffrey M; Marques-Bonet, Tomas; Ventura, Mario; Siswara, Priscillia; Jiang, Zhaoshi; Eichler, Evan E

2009-07-15

The human genome is a highly dynamic structure that shows a wide range of genetic polymorphic variation. Unlike other types of structural variation, little is known about inversion variants within normal individuals because such events are typically balanced and are difficult to detect and analyze by standard molecular approaches. Using sequence-based, cytogenetic and genotyping approaches, we characterized six large inversion polymorphisms that map to regions associated with genomic disorders with complex segmental duplications mapping at the breakpoints. We developed a metaphase FISH-based assay to genotype inversions and analyzed the chromosomes of 27 individuals from three HapMap populations. In this subset, we find that these inversions are less frequent or absent in Asians when compared with European and Yoruban populations. Analyzing multiple individuals from outgroup species of great apes, we show that most of these large inversion polymorphisms are specific to the human lineage with two exceptions, 17q21.31 and 8p23 inversions, which are found to be similarly polymorphic in other great ape species and where the inverted allele represents the ancestral state. Investigating linkage disequilibrium relationships with genotyped SNPs, we provide evidence that most of these inversions appear to have arisen on at least two different haplotype backgrounds. In these cases, discovery and genotyping methods based on SNPs may be confounded and molecular cytogenetics remains the only method to genotype these inversions.

Attained educational level and incident atherothrombotic events in low- and middle-income compared with high-income countries.

PubMed

Goyal, Abhinav; Bhatt, Deepak L; Steg, P Gabriel; Gersh, Bernard J; Alberts, Mark J; Ohman, E Magnus; Corbalán, Ramón; Eagle, Kim A; Gaxiola, Efrain; Gao, Runlin; Goto, Shinya; D'Agostino, Ralph B; Califf, Robert M; Smith, Sidney C; Wilson, Peter W F

2010-09-21

Studies report a protective effect of higher attained educational level (AEL) on cardiovascular outcomes. However, most of these studies have been conducted in high-income countries (HICs) and lack representation from low- and middle-income countries (LMICs), which bear >80% of the global burden of cardiovascular disease. The Reduction of Atherothrombosis for Continued Health (REACH) Registry is a prospective study of 67 888 subjects with either established atherothrombotic (coronary, cerebrovascular, and/or peripheral arterial) disease or multiple atherothrombotic risk factors enrolled from 5587 physician practices in 44 countries. At baseline, AEL (0 to 8 years, 9 to 12 years, trade or technical school, and university) was self-reported for 61 332 subjects. Outcomes included the baseline prevalence of atherothrombotic risk factors and the rate of incident cardiovascular events (cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke) through 23 months across AEL groups, stratified by sex and world region (LMICs or HICs). Educational attainment was inversely associated with age and diabetes mellitus and directly associated with hypercholesterolemia in all subjects. However, for other risk factors such as obesity, smoking, hypertension, and baseline burden of vascular disease, AEL was protective (inversely associated) in HICs but not protective in LMICs. The protective effect of greater AEL on incident cardiovascular events was strongest in men from HICs (P<0.0001), more modest in women from HICs (P=0.0026) and in men from LMICs (P=0.082), and essentially absent in women from LMICs (P=0.32). In contrast to HICs, higher AEL may not be protective against cardiovascular events in LMICs, particularly in women.

Do bonding and bridging social capital affect self-rated health, depressive mood and cognitive decline in older Japanese? A prospective cohort study.

PubMed

Murayama, Hiroshi; Nishi, Mariko; Matsuo, Eri; Nofuji, Yu; Shimizu, Yumiko; Taniguchi, Yu; Fujiwara, Yoshinori; Shinkai, Shoji

2013-12-01

Little is known regarding the longitudinal effects of bonding and bridging social capital on health. This study examined the longitudinal associations of bonding and bridging social capital with self-rated health, depressive mood, and cognitive decline in community-dwelling older Japanese. Data analyzed in this study were from the 2010 (baseline) and 2012 (follow-up) Hatoyama Cohort Study. Bonding social capital was assessed by individual perception of homogeneity of the neighborhood (the level of homogeneity among neighbors) and of networks (the amount of homogeneous personal networks) in relation to age, gender, and socioeconomic status. Bridging social capital was assessed by individual perception of heterogeneity of networks (the amount of heterogeneous personal networks) in relation to age, gender, and socioeconomic status. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the effects of baseline social capital on poor health outcome at follow-up by logistic regression analysis. In total, 681 people completed baseline and follow-up surveys. The mean age of participants was 71.8 ± 5.1 years, and 57.9% were male. After adjusting for sociodemographics, lifestyle factors, comorbidity, functional capacity, baseline score of each outcome, and other bonding/bridging social capital, stronger perceived neighborhood homogeneity was inversely associated with poor self-rated health (OR = 0.55, 95% CI = 0.30-1.00) and depressive mood assessed by the Geriatric Depression Scale (OR = 0.58, 95% CI = 0.34-0.99). When participants who reported a depressive mood at baseline were excluded, stronger perceived heterogeneous network was inversely associated with depressive mood (OR = 0.40, 95% CI = 0.19-0.87). Neither bonding nor bridging social capital was significantly associated with cognitive decline assessed by the Mini-Mental State Examination. In conclusion, bonding and bridging social capital affect health in different ways, but they both have beneficial effects on the health of older Japanese. Our findings suggest that intervention focusing on bonding and bridging social capital may improve various health outcomes in old age. Copyright © 2013 Elsevier Ltd. All rights reserved.

Alcohol intake in relation to non-fatal and fatal coronary heart disease and stroke: EPIC-CVD case-cohort study.

PubMed

Ricci, Cristian; Wood, Angela; Muller, David; Gunter, Marc J; Agudo, Antonio; Boeing, Heiner; van der Schouw, Yvonne T; Warnakula, Samantha; Saieva, Calogero; Spijkerman, Annemieke; Sluijs, Ivonne; Tjønneland, Anne; Kyrø, Cecilie; Weiderpass, Elisabete; Kühn, Tilman; Kaaks, Rudolf; Sánchez, Maria-Jose; Panico, Salvatore; Agnoli, Claudia; Palli, Domenico; Tumino, Rosario; Engström, Gunnar; Melander, Olle; Bonnet, Fabrice; Boer, Jolanda M A; Key, Timothy J; Travis, Ruth C; Overvad, Kim; Verschuren, W M Monique; Quirós, J Ramón; Trichopoulou, Antonia; Papatesta, Eleni-Maria; Peppa, Eleni; Iribas, Conchi Moreno; Gavrila, Diana; Forslund, Ann-Sofie; Jansson, Jan-Håkan; Matullo, Giuseppe; Arriola, Larraitz; Freisling, Heinz; Lassale, Camille; Tzoulaki, Ioanna; Sharp, Stephen J; Forouhi, Nita G; Langenberg, Claudia; Saracci, Rodolfo; Sweeting, Michael; Brennan, Paul; Butterworth, Adam S; Riboli, Elio; Wareham, Nick J; Danesh, John; Ferrari, Pietro

2018-05-29

To investigate the association between alcohol consumption (at baseline and over lifetime) and non-fatal and fatal coronary heart disease (CHD) and stroke. Multicentre case-cohort study. A study of cardiovascular disease (CVD) determinants within the European Prospective Investigation into Cancer and nutrition cohort (EPIC-CVD) from eight European countries. 32 549 participants without baseline CVD, comprised of incident CVD cases and a subcohort for comparison. Non-fatal and fatal CHD and stroke (including ischaemic and haemorrhagic stroke). There were 9307 non-fatal CHD events, 1699 fatal CHD, 5855 non-fatal stroke, and 733 fatal stroke. Baseline alcohol intake was inversely associated with non-fatal CHD, with a hazard ratio of 0.94 (95% confidence interval 0.92 to 0.96) per 12 g/day higher intake. There was a J shaped association between baseline alcohol intake and risk of fatal CHD. The hazard ratios were 0.83 (0.70 to 0.98), 0.65 (0.53 to 0.81), and 0.82 (0.65 to 1.03) for categories 5.0-14.9 g/day, 15.0-29.9 g/day, and 30.0-59.9 g/day of total alcohol intake, respectively, compared with 0.1-4.9 g/day. In contrast, hazard ratios for non-fatal and fatal stroke risk were 1.04 (1.02 to 1.07), and 1.05 (0.98 to 1.13) per 12 g/day increase in baseline alcohol intake, respectively, including broadly similar findings for ischaemic and haemorrhagic stroke. Associations with cardiovascular outcomes were broadly similar with average lifetime alcohol consumption as for baseline alcohol intake, and across the eight countries studied. There was no strong evidence for interactions of alcohol consumption with smoking status on the risk of CVD events. Alcohol intake was inversely associated with non-fatal CHD risk but positively associated with the risk of different stroke subtypes. This highlights the opposing associations of alcohol intake with different CVD types and strengthens the evidence for policies to reduce alcohol consumption. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Focused and Corrective Feedback Versus Structured and Supported Debriefing in a Simulation-Based Cardiac Arrest Team Training: A Pilot Randomized Controlled Study.

PubMed

Kim, Ji-Hoon; Kim, Young-Min; Park, Seong Heui; Ju, Eun A; Choi, Se Min; Hong, Tai Yong

2017-06-01

The aim of the study was to compare the educational impact of two postsimulation debriefing methods-focused and corrective feedback (FCF) versus Structured and Supported Debriefing (SSD)-on team dynamics in simulation-based cardiac arrest team training. This was a pilot randomized controlled study conducted at a simulation center. Fourth-year medical students were randomly assigned to the FCF or SSD group, with each team composed of six students and a confederate. Each team participated in two simulations and the assigned debriefing (FCF or SSD) sessions and then underwent a test simulation. Two trained raters blindly assessed all of the recorded simulations using checklists. The primary outcome was the improvement in team dynamics scores between baseline and test simulation. The secondary outcomes were improvements before and after training in team clinical performance scores, self-assessed comprehension of and confidence in cardiac arrest management and team dynamics, as well as evaluations of the postsimulation debriefing intervention. In total, 95 students participated [FCF (8 teams, n = 47) and SSD (8 teams, n = 48)]. The SSD team dynamics score during the test simulation was higher than at baseline [baseline: 74.5 (65.9-80.9), test: 85.0 (71.9-87.6), P = 0.035]. However, there were no differences in the improvement in the team dynamics or team clinical performance scores between the two groups (P = 0.328, respectively). There was no significant difference in improvement in team dynamics scores during the test simulation compared with baseline between the SSD and FCF groups in a simulation-based cardiac arrest team training in fourth-year Korean medical students.

MERIDIONAL FLOW IN THE SOLAR CONVECTION ZONE. II. HELIOSEISMIC INVERSIONS OF GONG DATA

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

Jackiewicz, J.; Serebryanskiy, A.; Kholikov, S., E-mail: jasonj@nmsu.edu

2015-06-01

Meridional flow is thought to play a very important role in the dynamics of the solar convection zone; however, because of its relatively small amplitude, precisely measuring it poses a significant challenge. Here we present a complete time–distance helioseismic analysis of about 2 years of ground-based Global Oscillation Network Group (GONG) Doppler data to retrieve the meridional circulation profile for modest latitudes in an attempt to corroborate results from other studies. We use an empirical correction to the travel times due to an unknown center-to-limb systematic effect. The helioseismic inversion procedure is first tested and reasonably validated on artificial datamore » from a large-scale numerical simulation followed by a test to broadly recover the solar differential rotation found from global seismology. From GONG data, we measure poleward photospheric flows at all latitudes with properties that are comparable with earlier studies and a shallow equatorward flow about 65 Mm beneath the surface, in agreement with recent findings from Helioseismic and Magnetic Imager (HMI) data. No strong evidence of multiple circulation cells in depth or latitude is found, yet the whole phase space has not yet been explored. Tests of mass flux conservation are then carried out on the inferred GONG and HMI flows and compared to a fiducial numerical baseline from models, and we find that the continuity equation is poorly satisfied. While the two disparate data sets do give similar results for about the outer 15% of the interior radius, the total inverted circulation pattern appears to be unphysical in terms of mass conservation when interpreted over modest time scales. We can likely attribute this to both the influence of realization noise and subtle effects in the data and measurement procedure.« less

Forward and inverse functional variations in rotationally inelastic scattering

NASA Astrophysics Data System (ADS)

Guzman, Robert; Rabitz, Herschel

1986-09-01

This paper considers the response of various rotational energy transfer processes to functional variations about an assumed model intermolecular potential. Attention is focused on the scattering of an atom and a linear rigid rotor. The collision dynamics are approximated by employing both the infinite order sudden (IOS) and exponential distorted wave (EDW) methods to describe Ar-N2 and He-H2, respectively. The following cross sections are considered: state-to-state differential and integral, final state summed differential and integral, and effective diffusion and viscosity cross sections. Attention is first given to the forward sensitivity densities δ0/δV(R,r) where 0 denotes any of the aforementioned cross sections, R is the intermolecular distance, and r is the internal coordinates. These forward sensitivity densities (functional derivatives) offer a quantitative measure of the importance of different regions of the potential surface to a chosen cross section. Via knowledge of the forward sensitivities and a particular variation δV(R,r) the concomitant response δ0 is generated. It was found that locally a variation in the potential can give rise to a large response in the cross sections as measured by these forward densities. In contrast, a unit percent change in the overall potential produced a 1%-10% change in the cross sections studied indicating that the large + and - responses to local variations tend to cancel. In addition, inverse sensitivity densities δV(R,r)/δ0 are obtained. These inverse densities are of interest since they are the exact solution to the infinitesimal inverse scattering problem. Although the inverse sensitivity densities do not in themselves form an inversion algorithm, they do offer a quantitative measure of the importance of performing particular measurements for the ultimate purpose of inversion. Using a set of state-to-state integral cross sections we found that the resultant responses from the infinitesimal inversion were typically small such that ‖δV(R,r)‖≪‖V(R,r)‖. From the viewpoint of an actual inversion, these results indicate that only through an extensive effort will significant knowledge of the potential be gained from the cross sections. All of these calculations serve to illustrate the methodology, and other observables as well as dynamical schemes could be explored as desired.

Improved real-time dynamics from imaginary frequency lattice simulations

NASA Astrophysics Data System (ADS)

Pawlowski, Jan M.; Rothkopf, Alexander

2018-03-01

The computation of real-time properties, such as transport coefficients or bound state spectra of strongly interacting quantum fields in thermal equilibrium is a pressing matter. Since the sign problem prevents a direct evaluation of these quantities, lattice data needs to be analytically continued from the Euclidean domain of the simulation to Minkowski time, in general an ill-posed inverse problem. Here we report on a novel approach to improve the determination of real-time information in the form of spectral functions by setting up a simulation prescription in imaginary frequencies. By carefully distinguishing between initial conditions and quantum dynamics one obtains access to correlation functions also outside the conventional Matsubara frequencies. In particular the range between ω0 and ω1 = 2πT, which is most relevant for the inverse problem may be more highly resolved. In combination with the fact that in imaginary frequencies the kernel of the inverse problem is not an exponential but only a rational function we observe significant improvements in the reconstruction of spectral functions, demonstrated in a simple 0+1 dimensional scalar field theory toy model.

[Comparisons and analysis of the spectral response functions' difference between FY-2E's and FY2C's split window channels].

PubMed

Zhang, Yong; Li, Yuan; Rong, Zhi-Guo

2010-06-01

Remote sensors' channel spectral response function (SRF) was one of the key factors to influence the quantitative products' inversion algorithm, accuracy and the geophysical characteristics. Aiming at the adjustments of FY-2E's split window channels' SRF, detailed comparisons between the FY-2E and FY-2C corresponding channels' SRF differences were carried out based on three data collections: the NOAA AVHRR corresponding channels' calibration look up tables, field measured water surface radiance and atmospheric profiles at Lake Qinghai and radiance calculated from the PLANK function within all dynamic range of FY-2E/C. The results showed that the adjustments of FY-2E's split window channels' SRF would result in the spectral range's movements and influence the inversion algorithms of some ground quantitative products. On the other hand, these adjustments of FY-2E SRFs would increase the brightness temperature differences between FY-2E's two split window channels within all dynamic range relative to FY-2C's. This would improve the inversion ability of FY-2E's split window channels.

Atomic-scale origin of dynamic viscoelastic response and creep in disordered solids

NASA Astrophysics Data System (ADS)

Milkus, Rico; Zaccone, Alessio

2017-02-01

Viscoelasticity has been described since the time of Maxwell as an interpolation of purely viscous and purely elastic response, but its microscopic atomic-level mechanism in solids has remained elusive. We studied three model disordered solids: a random lattice, the bond-depleted fcc lattice, and the fcc lattice with vacancies. Within the harmonic approximation for central-force lattices, we applied sum rules for viscoelastic response derived on the basis of nonaffine atomic motions. The latter motions are a direct result of local structural disorder, and in particular, of the lack of inversion symmetry in disordered lattices. By defining a suitable quantitative and general atomic-level measure of nonaffinity and inversion symmetry, we show that the viscoelastic responses of all three systems collapse onto a master curve upon normalizing by the overall strength of inversion-symmetry breaking in each system. Close to the isostatic point for central-force lattices, power-law creep G (t ) ˜t-1 /2 emerges as a consequence of the interplay between soft vibrational modes and nonaffine dynamics, and various analytical scalings, supported by numerical calculations, are predicted by the theory.

Estimating Soil and Root Parameters of Biofuel Crops using a Hydrogeophysical Inversion

NASA Astrophysics Data System (ADS)

Kuhl, A.; Kendall, A. D.; Van Dam, R. L.; Hyndman, D. W.

2017-12-01

Transpiration is the dominant pathway for continental water exchange to the atmosphere, and therefore a crucial aspect of modeling water balances at many scales. The root water uptake dynamics that control transpiration are dependent on soil water availability, as well as the root distribution. However, the root distribution is determined by many factors beyond the plant species alone, including climate conditions and soil texture. Despite the significant contribution of transpiration to global water fluxes, modelling the complex critical zone processes that drive root water uptake remains a challenge. Geophysical tools such as electrical resistivity (ER), have been shown to be highly sensitive to water dynamics in the unsaturated zone. ER data can be temporally and spatially robust, covering large areas or long time periods non-invasively, which is an advantage over in-situ methods. Previous studies have shown the value of using hydrogeophysical inversions to estimate soil properties. Others have used hydrological inversions to estimate both soil properties and root distribution parameters. In this study, we combine these two approaches to create a coupled hydrogeophysical inversion that estimates root and retention curve parameters for a HYDRUS model. To test the feasibility of this new approach, we estimated daily water fluxes and root growth for several biofuel crops at a long-term ecological research site in Southwest Michigan, using monthly ER data from 2009 through 2011. Time domain reflectometry data at seven depths was used to validate modeled soil moisture estimates throughout the model period. This hydrogeophysical inversion method shows promise for improving root distribution and transpiration estimates across a wide variety of settings.

Efficient mapping algorithms for scheduling robot inverse dynamics computation on a multiprocessor system

NASA Technical Reports Server (NTRS)

Lee, C. S. G.; Chen, C. L.

1989-01-01

Two efficient mapping algorithms for scheduling the robot inverse dynamics computation consisting of m computational modules with precedence relationship to be executed on a multiprocessor system consisting of p identical homogeneous processors with processor and communication costs to achieve minimum computation time are presented. An objective function is defined in terms of the sum of the processor finishing time and the interprocessor communication time. The minimax optimization is performed on the objective function to obtain the best mapping. This mapping problem can be formulated as a combination of the graph partitioning and the scheduling problems; both have been known to be NP-complete. Thus, to speed up the searching for a solution, two heuristic algorithms were proposed to obtain fast but suboptimal mapping solutions. The first algorithm utilizes the level and the communication intensity of the task modules to construct an ordered priority list of ready modules and the module assignment is performed by a weighted bipartite matching algorithm. For a near-optimal mapping solution, the problem can be solved by the heuristic algorithm with simulated annealing. These proposed optimization algorithms can solve various large-scale problems within a reasonable time. Computer simulations were performed to evaluate and verify the performance and the validity of the proposed mapping algorithms. Finally, experiments for computing the inverse dynamics of a six-jointed PUMA-like manipulator based on the Newton-Euler dynamic equations were implemented on an NCUBE/ten hypercube computer to verify the proposed mapping algorithms. Computer simulation and experimental results are compared and discussed.

Reconfigurable Control with Neural Network Augmentation for a Modified F-15 Aircraft

NASA Technical Reports Server (NTRS)

Burken, John J.

2007-01-01

This paper describes the performance of a simplified dynamic inversion controller with neural network supplementation. This 6 DOF (Degree-of-Freedom) simulation study focuses on the results with and without adaptation of neural networks using a simulation of the NASA modified F-15 which has canards. One area of interest is the performance of a simulated surface failure while attempting to minimize the inertial cross coupling effect of a [B] matrix failure (a control derivative anomaly associated with a jammed or missing control surface). Another area of interest and presented is simulated aerodynamic failures ([A] matrix) such as a canard failure. The controller uses explicit models to produce desired angular rate commands. The dynamic inversion calculates the necessary surface commands to achieve the desired rates. The simplified dynamic inversion uses approximate short period and roll axis dynamics. Initial results indicated that the transient response for a [B] matrix failure using a Neural Network (NN) improved the control behavior when compared to not using a neural network for a given failure, However, further evaluation of the controller was comparable, with objections io the cross coupling effects (after changes were made to the controller). This paper describes the methods employed to reduce the cross coupling effect and maintain adequate tracking errors. The IA] matrix failure results show that control of the aircraft without adaptation is more difficult [leas damped) than with active neural networks, Simulation results show Neural Network augmentation of the controller improves performance in terms of backing error and cross coupling reduction and improved performance with aerodynamic-type failures.

A real-time inverse quantised transform for multi-standard with dynamic resolution support

NASA Astrophysics Data System (ADS)

Sun, Chi-Chia; Lin, Chun-Ying; Zhang, Ce

2016-06-01

In this paper, a real-time configurable intelligent property (IP) core is presented for image/video decoding process in compatibility with the standard MPEG-4 Visual and the standard H.264/AVC. The inverse quantised discrete cosine and integer transform can be used to perform inverse quantised discrete cosine transform and inverse quantised inverse integer transforms which only required shift and add operations. Meanwhile, COordinate Rotation DIgital Computer iterations and compensation steps are adjustable in order to compensate for the video compression quality regarding various data throughput. The implementations are embedded in publicly available software XVID Codes 1.2.2 for the standard MPEG-4 Visual and the H.264/AVC reference software JM 16.1, where the experimental results show that the balance between the computational complexity and video compression quality is retained. At the end, FPGA synthesised results show that the proposed IP core can bring advantages to low hardware costs and also provide real-time performance for Full HD and 4K-2K video decoding.

The adaptive parallel UKF inversion method for the shape of space objects based on the ground-based photometric data

NASA Astrophysics Data System (ADS)

Du, Xiaoping; Wang, Yang; Liu, Hao

2018-04-01

The space object in highly elliptical orbit is always presented as an image point on the ground-based imaging equipment so that it is difficult to resolve and identify the shape and attitude directly. In this paper a novel algorithm is presented for the estimation of spacecraft shape. The apparent magnitude model suitable for the inversion of object information such as shape and attitude is established based on the analysis of photometric characteristics. A parallel adaptive shape inversion algorithm based on UKF was designed after the achievement of dynamic equation of the nonlinear, Gaussian system involved with the influence of various dragging forces. The result of a simulation study demonstrate the viability and robustness of the new filter and its fast convergence rate. It realizes the inversion of combination shape with high accuracy, especially for the bus of cube and cylinder. Even though with sparse photometric data, it still can maintain a higher success rate of inversion.

Computational Fluid Dynamics (CFD) investigation onto passenger car disk brake design

NASA Astrophysics Data System (ADS)

Munisamy, Kannan M.; Kanasan Moorthy, Shangkari K.

2013-06-01

The aim of this study is to investigate the flow and heat transfer in ventilated disc brakes using Computational Fluid Dynamics (CFD). NACA Series blade is designed for ventilated disc brake and the cooling characteristic is compared to the baseline design. The ventilated disc brakes are simulated using commercial CFD software FLUENTTM using simulation configuration that was obtained from experiment data. The NACA Series blade design shows improvements in Nusselt number compared to baseline design.

Estimating error statistics for Chambon-la-Forêt observatory definitive data

NASA Astrophysics Data System (ADS)

Lesur, Vincent; Heumez, Benoît; Telali, Abdelkader; Lalanne, Xavier; Soloviev, Anatoly

2017-08-01

We propose a new algorithm for calibrating definitive observatory data with the goal of providing users with estimates of the data error standard deviations (SDs). The algorithm has been implemented and tested using Chambon-la-Forêt observatory (CLF) data. The calibration process uses all available data. It is set as a large, weakly non-linear, inverse problem that ultimately provides estimates of baseline values in three orthogonal directions, together with their expected standard deviations. For this inverse problem, absolute data error statistics are estimated from two series of absolute measurements made within a day. Similarly, variometer data error statistics are derived by comparing variometer data time series between different pairs of instruments over few years. The comparisons of these time series led us to use an autoregressive process of order 1 (AR1 process) as a prior for the baselines. Therefore the obtained baselines do not vary smoothly in time. They have relatively small SDs, well below 300 pT when absolute data are recorded twice a week - i.e. within the daily to weekly measures recommended by INTERMAGNET. The algorithm was tested against the process traditionally used to derive baselines at CLF observatory, suggesting that statistics are less favourable when this latter process is used. Finally, two sets of definitive data were calibrated using the new algorithm. Their comparison shows that the definitive data SDs are less than 400 pT and may be slightly overestimated by our process: an indication that more work is required to have proper estimates of absolute data error statistics. For magnetic field modelling, the results show that even on isolated sites like CLF observatory, there are very localised signals over a large span of temporal frequencies that can be as large as 1 nT. The SDs reported here encompass signals of a few hundred metres and less than a day wavelengths.

CD4/CD8 ratio, age, and risk of serious non-communicable diseases in HIV-infected adults on antiretroviral therapy

PubMed Central

CASTILHO, Jessica L.; SHEPHERD, Bryan E.; KOETHE, John; TURNER, Megan; BEBAWY, Sally; LOGAN, James; ROGERS, William B.; RAFFANTI, Stephen; STERLING, Timothy R.

2015-01-01

Objective In virologically suppressed HIV-infected adults, non-communicable diseases (NCDs) have been associated with immune senescence and low CD4/CD8 lymphocyte ratio. Age differences in the relationship between CD4/CD8 ratio and NCDs have not been described. Design Observational cohort study. Methods We assessed CD4/CD8 ratio and incident NCDs (cardiovascular, cancer, liver, and renal diseases) in HIV-infected adults started on antiretroviral therapy between 1998–2012. Study inclusion began once patients maintained virologic suppression for 12 months (defined as baseline). We examined age and baseline CD4/CD8 ratio and used Cox proportional hazard models to assess baseline CD4/CD8 ratio and NCDs. Results This study included 2,006 patients. Low baseline CD4/CD8 ratio was associated with older age, male sex, and low CD4 lymphocyte counts. In models adjusting for CD4 lymphocyte count, CD4/CD8 ratio was inversely associated with age (p <0.01). Among all patients, 182 had incident NCDs, including 46 with coronary artery disease (CAD) events. CD4/CD8 ratio was inversely associated with risk of CAD events (adjusted HR per 0.1 increase in CD4/CD8 ratio = 0.87, 95% CI: 0.76–0.99, p=0.03). This association was driven by those under age 50 years (adjusted HR 0.83 [0.70–0.97], p = 0.02) versus those over age 50 years (adjusted HR = 0.96 [0.79–1.18], p = 0.71). CD4/CD8 ratio was not significantly associated with incident non-cardiac NCDs. Conclusions Higher CD4/CD8 ratio after one year of HIV virologic suppression was independently predictive of decreased CAD risk, particularly among younger adults. Advanced immune senescence may contribute to CAD events in younger HIV patients on antiretroviral therapy. PMID:26959354

N-Terminal Pro-Brain Natriuretic Peptide and Heart Failure Risk Among Individuals With and Without Obesity: The Atherosclerosis Risk in Communities (ARIC) Study.

PubMed

Ndumele, Chiadi E; Matsushita, Kunihiro; Sang, Yingying; Lazo, Mariana; Agarwal, Sunil K; Nambi, Vijay; Deswal, Anita; Blumenthal, Roger S; Ballantyne, Christie M; Coresh, Josef; Selvin, Elizabeth

2016-02-16

Obesity is a risk factor for heart failure (HF) but is associated with lower N-terminal pro-brain natriuretic peptide (NT-proBNP) levels. It is unclear whether the prognostic value and implications of NT-proBNP levels for HF risk differ across body mass index (BMI) categories. We followed up 12 230 ARIC participants free of prior HF at baseline (visit 2, 1990-1992) with BMI ≥18.5 kg/m(2). We quantified and compared the relative and absolute risk associations of NT-proBNP with incident HF across BMI categories. There were 1861 HF events during a median 20.6 years of follow-up. Despite increased HF risk in obesity, a weak inverse association was seen between baseline BMI and NT-proBNP levels (r=-0.10). Nevertheless, higher baseline NT-proBNP was associated with increased HF risk in all BMI categories. NT-proBNP improved HF risk prediction overall, even among those with severe obesity (BMI ≥35 kg/m(2); improvement in C statistic, 0.032; 95% confidence interval, 0.011-0.053). However, given the higher HF rates among those with obesity, at each NT-proBNP level, higher BMI was associated with greater absolute HF risk. Indeed, among those with NT-proBNP of 100 to <200 pg/mL, the average 10-year HF risk was <5% among normal-weight individuals but >10% among the severely obese. Despite its inverse relationship with BMI, NT-proBNP provides significant prognostic information on the risk of developing HF even among individuals with obesity. Given the higher baseline HF risk among persons with obesity, even slight elevations in NT-proBNP may have implications for increased absolute HF risk in this population. © 2016 American Heart Association, Inc.

Relativistic diffusive motion in random electromagnetic fields

NASA Astrophysics Data System (ADS)

Haba, Z.

2011-08-01

We show that the relativistic dynamics in a Gaussian random electromagnetic field can be approximated by the relativistic diffusion of Schay and Dudley. Lorentz invariant dynamics in the proper time leads to the diffusion in the proper time. The dynamics in the laboratory time gives the diffusive transport equation corresponding to the Jüttner equilibrium at the inverse temperature β-1 = mc2. The diffusion constant is expressed by the field strength correlation function (Kubo's formula).

Inference of effective river properties from remotely sensed observations of water surface

NASA Astrophysics Data System (ADS)

Garambois, Pierre-André; Monnier, Jérôme

2015-05-01

The future SWOT mission (Surface Water and Ocean Topography) will provide cartographic measurements of inland water surfaces (elevation, widths and slope) at an unprecedented spatial and temporal resolution. Given synthetic SWOT like data, forward flow models of hierarchical-complexity are revisited and few inverse formulations are derived and assessed for retrieving the river low flow bathymetry, roughness and discharge (A0, K, Q) . The concept of an effective low flow bathymetry A0 (the real one being never observed) and roughness K , hence an effective river dynamics description, is introduced. The few inverse models elaborated for inferring (A0, K, Q) are analyzed in two contexts: (1) only remotely sensed observations of the water surface (surface elevation, width and slope) are available; (2) one additional water depth measurement (or estimate) is available. The inverse models elaborated are independent of data acquisition dynamics; they are assessed on 91 synthetic test cases sampling a wide range of steady-state river flows (the Froude number varying between 0.05 and 0.5 for 1 km reaches) and in the case of a flood on the Garonne River (France) characterized by large spatio-temporal variabilities. It is demonstrated that the most complete shallow-water like model allowing to separate the roughness and bathymetry terms is the so-called low Froude model. In Case (1), the resulting RMSE on infered discharges are on the order of 15% for first guess errors larger than 50%. An important feature of the present inverse methods is the fairly good accuracy of the discharge Q obtained, while the identified roughness coefficient K includes the measurement errors and the misfit of physics between the real flow and the hypothesis on which the inverse models rely; the later neglecting the unobserved temporal variations of the flow and the inertia effects. A compensation phenomena between the indentifiedvalues of K and the unobserved bathymetry A0 is highlighted, while the present inverse models lead to an effective river dynamics model that is accurate in the range of the discharge variability observed. In Case (2), the effective bathymetry profile for 80 km of the Garonne River is retrieved with 1% relative error only. Next, accurate effective topography-friction pairs and also discharge can be inferred. Finally, defining river reaches from the observation grid tends to average the river properties in each reach, hence tends to smooth the hydraulic variability.

An order (n) algorithm for the dynamics simulation of robotic systems

NASA Technical Reports Server (NTRS)

Chun, H. M.; Turner, J. D.; Frisch, Harold P.

1989-01-01

The formulation of an Order (n) algorithm for DISCOS (Dynamics Interaction Simulation of Controls and Structures), which is an industry-standard software package for simulation and analysis of flexible multibody systems is presented. For systems involving many bodies, the new Order (n) version of DISCOS is much faster than the current version. Results of the experimental validation of the dynamics software are also presented. The experiment is carried out on a seven-joint robot arm at NASA's Goddard Space Flight Center. The algorithm used in the current version of DISCOS requires the inverse of a matrix whose dimension is equal to the number of constraints in the system. Generally, the number of constraints in a system is roughly proportional to the number of bodies in the system, and matrix inversion requires O(p exp 3) operations, where p is the dimension of the matrix. The current version of DISCOS is therefore considered an Order (n exp 3) algorithm. In contrast, the Order (n) algorithm requires inversion of matrices which are small, and the number of matrices to be inverted increases only linearly with the number of bodies. The newly-developed Order (n) DISCOS is currently capable of handling chain and tree topologies as well as multiple closed loops. Continuing development will extend the capability of the software to deal with typical robotics applications such as put-and-place, multi-arm hand-off and surface sliding.

Feedback control laws for highly maneuverable aircraft

NASA Technical Reports Server (NTRS)

Garrard, William L.; Balas, Gary J.

1995-01-01

During this year, we concentrated our efforts on the design of controllers for lateral/directional control using mu synthesis. This proved to be a more difficult task than we anticipated and we are still working on the designs. In the lateral-directional control problem, the inputs are pilot lateral stick and pedal commands and the outputs are roll rate about the velocity vector and side slip angle. The control effectors are ailerons, rudder deflection, and directional thrust vectoring vane deflection which produces a yawing moment about the body axis. Our math model does not contain any provision for thrust vectoring of rolling moment. This has resulted in limitations of performance at high angles of attack. During 1994-95, the following tasks for the lateral-directional controllers were accomplished: (1) Designed both inner and outer loop dynamic inversion controllers. These controllers are implemented using accelerometer outputs rather than an a priori model of the vehicle aerodynamics; (2) Used classical techniques to design controllers for the system linearized by dynamics inversion. These controllers acted to control roll rate and Dutch roll response; (3) Implemented the inner loop dynamic inversion and classical controllers on the six DOF simulation; (4) Developed a lateral-directional control allocation scheme based on minimizing required control effort among the ailerons, rudder, and directional thrust vectoring; and (5) Developed mu outer loop controllers combined with classical inner loop controllers.

Success Stories in Control: Nonlinear Dynamic Inversion Control

NASA Technical Reports Server (NTRS)

Bosworth, John T.

2010-01-01

NASA plays an important role in advancing the state of the art in flight control systems. In the case of Nonlinear Dynamic Inversion (NDI) NASA supported initial implementation of the theory in an aircraft and demonstration in a space vehicle. Dr. Dale Enns of Honeywell Aerospace Advanced Technology performed this work in cooperation with NASA and under NASA contract. Honeywell and Lockheed Martin were subsequently contracted by AFRL to create "Design Guidelines for Multivariable Control Theory". This foundational work directly contributed to the advancement of the technology and the credibility of the control law as a design option. As a result Honeywell collaborated with Lockheed Martin to produce a Nonlinear Dynamic Inversion controller for the X-35 and subsequently Lockheed Martin did the same for the production Lockheed Martin F-35 vehicle. The theory behind NDI is to use a systematic generalized approach to controlling a vehicle. Using general aircraft nonlinear equations of motion and onboard aerodynamic, mass properties, and engine models specific to the vehicle, a relationship between control effectors and desired aircraft motion can be formulated. Using this formulation a control combination is used that provides a predictable response to commanded motion. Control loops around this formulation shape the response as desired and provide robustness to modeling errors. Once the control law is designed it can be used on a similar class of vehicle with only an update to the vehicle specific onboard models.

Mediterranean diet, overweight and body composition in children from eight European countries: cross-sectional and prospective results from the IDEFICS study.

PubMed

Tognon, G; Hebestreit, A; Lanfer, A; Moreno, L A; Pala, V; Siani, A; Tornaritis, M; De Henauw, S; Veidebaum, T; Molnár, D; Ahrens, W; Lissner, L

2014-02-01

A Mediterranean-like dietary pattern has been shown to be inversely associated with many diseases, but its role in early obesity prevention is not clear. We aimed to determine if this pattern is common among European children and whether it is associated with overweight and obesity. The IDEFICS study recruited 16,220 children aged 2-9 years from study centers in eight European countries. Weight, height, waist circumference, and skinfolds were measured at baseline and in 9114 children of the original cohort after two years. Diet was evaluated by a parental questionnaire reporting children's usual consumption of 43 food items. Adherence to a Mediterranean-like diet was calculated by a food frequency-based Mediterranean Diet Score (fMDS). The highest fMDS levels were observed in Sweden, the lowest in Cyprus. High scores were inversely associated with overweight including obesity (OR = 0.85, 95% CI: 0.77; 0.94) and percent fat mass (β = -0.22, 95% CI: -0.43; -0.01) independently of age, sex, socioeconomic status, study center and physical activity. High fMDS at baseline protected against increases in BMI (OR = 0.87, 95% CI: 0.78; 0.98), waist circumference (OR = 0.87, 95% CI: 0.77; 0.98) and waist-to-height ratio (OR = 0.88, 95% CI: 0.78; 0.99) with a similar trend observed for percent fat mass (p = 0.06). Although a Mediterranean dietary pattern is inversely associated with childhood obesity, it is not common in children living in the Mediterranean region and should therefore be advocated as part of EU obesity prevention strategies. Copyright © 2013 Elsevier B.V. All rights reserved.

Characterization of macromolecular baseline of human brain using metabolite cycled semi-LASER at 9.4T.

PubMed

Giapitzakis, Ioannis-Angelos; Avdievich, Nikolai; Henning, Anke

2018-08-01

Macromolecular resonances (MM) arise mainly from cytosolic proteins and overlap with metabolites, influencing metabolite quantification. Macromolecules can serve as valuable biomarkers for diseases and pathologies. The objectives of this study were to characterize MM at 9.4T in the human brain (occipital and left parietal lobe) and to describe the RF coil setup used for MM acquisition in the two regions. An adiabatic inversion pulse was optimised for metabolite nulling at 9.4T using double inversion recovery and was combined for the first time with metabolite cycled (MC) semi-LASER and appropriate coil configuration. MM spectra (seven volunteers) from two brain locations were averaged and smoothed creating MM templates, which were then parametrized using simulated Voigt-shaped lines within LCModel. Quantification was performed on individual data sets, including corrections for different tissue composition and the T 1 and T 2 relaxation of water. Our coil configuration method resulted in efficient B1+ (>30 T/√kW) for both brain regions. The 15 MM components were detected and quantified in MM baselines of the two brain areas. No significant differences in concentration levels of MM between different regions were found. Two new MM peaks were reported (M7 & M8). Double inversion, which was combined with MC semi-LASER, enabled the acquisition of high spectral resolution MM spectra for both brain regions at 9.4T. The 15 MM components were detected and quantified. Two new MM peaks were reported for the first time (M7 & M8) and preliminarily assigned to β-methylene protons of aspartyl-groups. Magn Reson Med 80:462-473, 2018. © 2018 International Society for Magnetic Resonance in Medicine. © 2018 International Society for Magnetic Resonance in Medicine.

Hemodynamic and neurochemical determinates of renal function in chronic heart failure.

PubMed

Gilbert, Cameron; Cherney, David Z I; Parker, Andrea B; Mak, Susanna; Floras, John S; Al-Hesayen, Abdul; Parker, John D

2016-01-15

Abnormal renal function is common in acute and chronic congestive heart failure (CHF) and is related to the severity of congestion. However, treatment of congestion often leads to worsening renal function. Our objective was to explore basal determinants of renal function and their response to hemodynamic interventions. Thirty-seven patients without CHF and 59 patients with chronic CHF (ejection fraction; 23 ± 8%) underwent right heart catheterization, measurements of glomerular filtration rate (GFR; inulin) and renal plasma flow (RPF; para-aminohippurate), and radiotracer estimates of renal sympathetic activity. A subset (26 without, 36 with CHF) underwent acute pharmacological intervention with dobutamine or nitroprusside. We explored the relationship between baseline and drug-induced hemodynamic changes and changes in renal function. In CHF, there was an inverse relationship among right atrial mean pressure (RAM) pressure, RPF, and GFR. By contrast, mean arterial pressure (MAP), cardiac index (CI), and measures of renal sympathetic activity were not significant predictors. In those with CHF there was also an inverse relationship among the drug-induced changes in RAM as well as pulmonary artery mean pressure and the change in GFR. Changes in MAP and CI did not predict the change in GFR in those with CHF. Baseline values and changes in RAM pressure did not correlate with GFR in those without CHF. In the CHF group there was a positive correlation between RAM pressure and renal sympathetic activity. There was also an inverse relationship among RAM pressure, GFR, and RPF in patients with chronic CHF. The observation that acute reductions in RAM pressure is associated with an increase in GFR in patients with CHF has important clinical implications. Copyright © 2016 the American Physiological Society.

Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study.

PubMed

Hertog, M G; Feskens, E J; Hollman, P C; Katan, M B; Kromhout, D

1993-10-23

Flavonoids are polyphenolic antioxidants naturally present in vegetables, fruits, and beverages such as tea and wine. In vitro, flavonoids inhibit oxidation of low-density lipoprotein and reduce thrombotic tendency, but their effects on atherosclerotic complications in human beings are unknown. We measured the content in various foods of the flavonoids quercetin, kaempferol, myricetin, apigenin, and luteolin. We then assessed the flavonoid intake of 805 men aged 65-84 years in 1985 by a cross-check dietary history; the men were then followed up for 5 years. Mean baseline flavonoid intake was 25.9 mg daily. The major sources of intake were tea (61%), onions (13%), and apples (10%). Between 1985 and 1990, 43 men died of coronary heart disease. Fatal or non-fatal myocardial infarction occurred in 38 of 693 men with no history of myocardial infarction at baseline. Flavonoid intake (analysed in tertiles) was significantly inversely associated with mortality from coronary heart disease (p for trend = 0.015) and showed an inverse relation with incidence of myocardial infarction, which was of borderline significance (p for trend = 0.08). The relative risk of coronary heart disease mortality in the highest versus the lowest tertile of flavonoid intake was 0.42 (95% CI 0.20-0.88). After adjustment for age, body-mass index, smoking, serum total and high-density-lipoprotein cholesterol, blood pressure, physical activity, coffee consumption, and intake of energy, vitamin C, vitamin E, beta-carotene, and dietary fibre, the risk was still significant (0.32 [0.15-0.71]). Intakes of tea, onions, and apples were also inversely related to coronary heart disease mortality, but these associations were weaker. Flavonoids in regularly consumed foods may reduce the risk of death from coronary heart disease in elderly men.

Plasma carotenoids and tocopherols in relation to prostate-specific antigen (PSA) levels among men with biochemical recurrence of prostate cancer.

PubMed

Antwi, Samuel O; Steck, Susan E; Zhang, Hongmei; Stumm, Lareissa; Zhang, Jiajia; Hurley, Thomas G; Hebert, James R

2015-10-01

Although men presenting with clinically localized prostate cancer (PrCA) often are treated with radical prostatectomy or radiation therapy with curative intent, about 25-40% develop biochemically recurrent PrCA within 5 years of treatment, which has no known cure. Studies suggest that carotenoid and tocopherol intake may be associated with PrCA risk and progression. We examined plasma carotenoid and tocopherol levels in relation to prostate-specific antigen (PSA) levels among men with PSA-defined biochemical recurrence of PrCA. Data analyzed were from a 6-month diet, physical activity and stress-reduction intervention trial conducted in South Carolina among biochemically recurrent PrCA patients (n=39). Plasma carotenoids and tocopherol levels were measured using high-performance liquid chromatography (HPLC). Linear regression was used to estimate least-square means comparing PSA levels of men with high versus low carotenoid/tocopherol levels, adjusting for covariates. After adjusting for baseline PSA level, plasma cis-lutein/zeaxanthin level at 3 months was related inversely to PSA level at 3 months (P=0.0008), while α-tocopherol (P=0.01), β-cryptoxanthin (P=0.01), and all-trans-lycopene (P=0.004) levels at 3 months were related inversely to PSA levels at 6-months. Percent increase in α-tocopherol and trans-β-carotene levels from baseline to month 3 were associated with lower PSA levels at 3 and 6 months. Percent increase in β-cryptoxanthin, cis-lutein/zeaxanthin and all-trans-lycopene were associated with lower PSA levels at 6 months only. Certain plasma carotenoids and tocopherols were related inversely to PSA levels at various timepoints, suggesting that greater intake of foods containing these micronutrients might be beneficial to men with PSA-defined PrCA recurrence. Copyright © 2015. Published by Elsevier Ltd.

Relationships between serum leptin levels and bone mineral parameters in school-aged children: a 3-year follow-up study.

PubMed

Kouda, Katsuyasu; Ohara, Kumiko; Fujita, Yuki; Nakamura, Harunobu; Tachiki, Takahiro; Iki, Masayuki

2018-02-02

Leptin regulates bone cell differentiation and functions via direct and indirect actions in experimental settings. Epidemiologically, however, the impact of leptin on the regulation of bone metabolism remains unclear. While some studies have reported a positive relationship between leptin and bone mineral parameters, other studies found an inverse or no association. We analyzed data from a population-based follow-up survey of community-dwelling children in Hamamatsu, Japan, to investigate relationships between leptin levels and bone mineral parameters. Multiple regression analysis was performed. Multicollinearity was quantified using the variance infiltration factor (VIF). Among 408 children who participated in the baseline survey (at age 11.2 years), 254 (121 boys and 133 girls) completed the follow-up survey (at age 14.2 years). Leptin levels were strongly related to fat mass (r = 0.87 in boys, r = 0.80 in girls). Leptin levels at baseline were significantly (P < 0.05) positively related to total body less head (TBLH) areal bone mineral density (aBMD) at follow-up in girls (standardized partial regression coefficient: β = 0.302, VIF = 2.246), after adjusting for body fat percentage (%). On the other hand, leptin levels were inversely related to TBLH aBMD in boys (β = - 0.395, VIF = 4.116), after adjusting for body fat mass (kg). Positive relationships between leptin levels and bone mineral parameters were observed with VIF values < 4.0, whereas inverse relationships were observed with VIF values ≥ 4.0. These findings suggest that positive relationships between leptin levels and bone mineral parameters are weak, or not always observed, due to statistical problems (i.e., multicollinearity) and other factors derived from adipose tissue.

Dynamic Paper Constructions for Easier Visualization of Molecular Symmetry

ERIC Educational Resources Information Center

Sein, Lawrence T., Jr.

2010-01-01

A system for construction of simple poster-board models is described. The models dynamically demonstrate the symmetry operations of proper rotation, improper rotation, reflection, and inversion for the chemically important point groups D[subscript 3h], D[subscript 4h], D[subscript 5h], D[subscript 6h], T[subscript d], and O[subscript h]. The…

Boreal soil carbon dynamics under a changing climate: a model inversion approach

Treesearch

Zhaosheng Fan; Jason C. Neff; Jennifer W. Harden; Kimberly P. Wickland

2008-01-01

Several fundamental but important factors controlling the feedback of boreal organic carbon (OC) to climate change were examined using a mechanistic model of soil OC dynamics, including the combined effects of temperature and moisture on the decomposition of OC and the factors controlling carbon quality and decomposition with depth. To estimate decomposition rates and...

Salt-induced effects on natural and inverse DPPC lipid membranes: Molecular dynamics simulation.

PubMed

Rezaei Sani, Seyed Mojtaba; Akhavan, Mojdeh; Jalili, Seifollah

2018-08-01

Molecular dynamics (MD) simulations of a dipalmitoylphosphatidylcholine (DPPC) bilayer and its neutral inverse-phosphocholine equivalent (DPCPe) were performed to find salt-induced effects on their surface structure and the nature of ion-lipid interactions. We found that the area per lipid is not considerably affected by the inversion, but the deuterium order parameter of carbon atoms in the region of carbonyl carbons changes dramatically. MD simulations indicate that Ca 2+ ions can bind to the surface of both DPPC and DPCPe membranes, but K + ions do not bind to them. In the case of Na + , however, the ions can bind to natural lipids but not to the inverse ones. Also, our results demonstrate that the hydration level of CPe bilayers is substantially lower than PC bilayers and the averaged orientation of water dipoles in the region of CPe headgroups is effectively inverted compared to PC lipids. This might be important in the interaction of the bilayer with its biological environment. Furthermore, it was found for the CPe bilayers that the enhanced peaks of the electrostatic potential profiles shift further away from the bilayer center relative to those of PC bilayers. This behavior makes the penetration of cations into the bilayer more difficult and possibly explains the experimentally observed enhanced release rates of anionic compounds in the CPe membrane. Copyright © 2018 Elsevier B.V. All rights reserved.

Goal Directed Model Inversion: A Study of Dynamic Behavior

NASA Technical Reports Server (NTRS)

Colombano, Silvano P.; Compton, Michael; Raghavan, Bharathi; Lum, Henry, Jr. (Technical Monitor)

1994-01-01

Goal Directed Model Inversion (GDMI) is an algorithm designed to generalize supervised learning to the case where target outputs are not available to the learning system. The output of the learning system becomes the input to some external device or transformation, and only the output of this device or transformation can be compared to a desired target. The fundamental driving mechanism of GDMI is to learn from success. Given that a wrong outcome is achieved, one notes that the action that produced that outcome 0 "would have been right if the outcome had been the desired one." The algorithm then proceeds as follows: (1) store the action that produced the wrong outcome as a "target" (2) redefine the wrong outcome as a desired goal (3) submit the new desired goal to the system (4) compare the new action with the target action and modify the system by using a suitable algorithm for credit assignment (Back propagation in our example) (5) resubmit the original goal. Prior publications by our group in this area focused on demonstrating empirical results based on the inverse kinematic problem for a simulated robotic arm. In this paper we apply the inversion process to much simpler analytic functions in order to elucidate the dynamic behavior of the system and to determine the sensitivity of the learning process to various parameters. This understanding will be necessary for the acceptance of GDMI as a practical tool.

Inverse stochastic-dynamic models for high-resolution Greenland ice core records

NASA Astrophysics Data System (ADS)

Boers, Niklas; Chekroun, Mickael D.; Liu, Honghu; Kondrashov, Dmitri; Rousseau, Denis-Didier; Svensson, Anders; Bigler, Matthias; Ghil, Michael

2017-12-01

Proxy records from Greenland ice cores have been studied for several decades, yet many open questions remain regarding the climate variability encoded therein. Here, we use a Bayesian framework for inferring inverse, stochastic-dynamic models from δ18O and dust records of unprecedented, subdecadal temporal resolution. The records stem from the North Greenland Ice Core Project (NGRIP), and we focus on the time interval 59-22 ka b2k. Our model reproduces the dynamical characteristics of both the δ18O and dust proxy records, including the millennial-scale Dansgaard-Oeschger variability, as well as statistical properties such as probability density functions, waiting times and power spectra, with no need for any external forcing. The crucial ingredients for capturing these properties are (i) high-resolution training data, (ii) cubic drift terms, (iii) nonlinear coupling terms between the δ18O and dust time series, and (iv) non-Markovian contributions that represent short-term memory effects.

Gravitational Field as a Pressure Force from Logarithmic Lagrangians and Non-Standard Hamiltonians: The Case of Stellar Halo of Milky Way

NASA Astrophysics Data System (ADS)

El-Nabulsi, Rami Ahmad

2018-03-01

Recently, the notion of non-standard Lagrangians was discussed widely in literature in an attempt to explore the inverse variational problem of nonlinear differential equations. Different forms of non-standard Lagrangians were introduced in literature and have revealed nice mathematical and physical properties. One interesting form related to the inverse variational problem is the logarithmic Lagrangian, which has a number of motivating features related to the Liénard-type and Emden nonlinear differential equations. Such types of Lagrangians lead to nonlinear dynamics based on non-standard Hamiltonians. In this communication, we show that some new dynamical properties are obtained in stellar dynamics if standard Lagrangians are replaced by Logarithmic Lagrangians and their corresponding non-standard Hamiltonians. One interesting consequence concerns the emergence of an extra pressure term, which is related to the gravitational field suggesting that gravitation may act as a pressure in a strong gravitational field. The case of the stellar halo of the Milky Way is considered.

Investigating large-scale brain dynamics using field potential recordings: analysis and interpretation.

PubMed

Pesaran, Bijan; Vinck, Martin; Einevoll, Gaute T; Sirota, Anton; Fries, Pascal; Siegel, Markus; Truccolo, Wilson; Schroeder, Charles E; Srinivasan, Ramesh

2018-06-25

New technologies to record electrical activity from the brain on a massive scale offer tremendous opportunities for discovery. Electrical measurements of large-scale brain dynamics, termed field potentials, are especially important to understanding and treating the human brain. Here, our goal is to provide best practices on how field potential recordings (electroencephalograms, magnetoencephalograms, electrocorticograms and local field potentials) can be analyzed to identify large-scale brain dynamics, and to highlight critical issues and limitations of interpretation in current work. We focus our discussion of analyses around the broad themes of activation, correlation, communication and coding. We provide recommendations for interpreting the data using forward and inverse models. The forward model describes how field potentials are generated by the activity of populations of neurons. The inverse model describes how to infer the activity of populations of neurons from field potential recordings. A recurring theme is the challenge of understanding how field potentials reflect neuronal population activity given the complexity of the underlying brain systems.

Chiral aldehydes in hydrocarbons: diastereoselective nucleophilic addition, NMR, and CD spectroscopy reveal dynamic solvation effects.

PubMed

Cainelli, Gianfranco; Galletti, Paola; Pieraccini, Silvia; Quintavalla, Arianna; Giacomini, Daria; Piero Spada, Gian

2004-01-01

Temperature-dependent studies on the diastereoselective nucleophilic addition of n- BuLi to alpha-chiral aldehydes as (S)-O-(t-butyl-dimethylsilyl)lactal, (S)-O-(t-butyl-dimethylsilyl) mandelic aldehyde, and (R)-2-phenylpropanal in n-decane and n-dodecane reveal dynamic solvation phenomena with the presence of inversion temperatures (T(inv)) in the Eyring plots of ln (anti/syn) vs. 1/ T. These dynamic solvent effects were disclosed by temperature-dependent studies of the (13)C NMR, CD, and UV spectra of the starting aldehydes in solution of n-decane and n-dodecane. The concomitant presence of three peculiar temperatures T(CD), T(UV), and T(NMR), whose values are identical and match T(inv), clearly confirms our earlier interpretation of the solvent-dependent nature of T(inv). The inversion temperature, as well as T(CD), T(UV), and T(NMR) represents the interconversion temperature of two different solvation clusters which act as two different supramolecules with different stereoselectivities. Copyright 2003 Wiley-Liss, Inc.

Electronic structure and molecular dynamics of Na2Li

NASA Astrophysics Data System (ADS)

Malcolm, Nathaniel O. J.; McDouall, Joseph J. W.

Following the first report (Mile, B., Sillman, P. D., Yacob, A. R. and Howard, J. A., 1996, J. chem. Soc. Dalton Trans , 653) of the EPR spectrum of the mixed alkali-metal trimer Na2Li a detailed study has been made of the electronic structure and structural dynamics of this species. Two isomeric forms have been found: one of the type, Na-Li-Na, of C , symmetry and another, Li-Na-Na, of C symmetry. Also, there are two linear saddle points which correspond to 'inversion' transition structures, and a saddle point of C symmetry which connects the two minima. A molecular dynamics investigation of these species shows that, at the temperature of the reported experiments (170 K), the C minimum is not 'static', but undergoes quite rapid inversion. At higher temperatures the C minimum converts to the C form, but by a mechanism very different from that suggested by minimum energy path considerations. 2 2v s s 2v 2v s

Estimating tropical-forest density profiles from multibaseline interferometric SAR

NASA Technical Reports Server (NTRS)

Treuhaft, Robert; Chapman, Bruce; dos Santos, Joao Roberto; Dutra, Luciano; Goncalves, Fabio; da Costa Freitas, Corina; Mura, Jose Claudio; de Alencastro Graca, Paulo Mauricio

2006-01-01

Vertical profiles of forest density are potentially robust indicators of forest biomass, fire susceptibility and ecosystem function. Tropical forests, which are among the most dense and complicated targets for remote sensing, contain about 45% of the world's biomass. Remote sensing of tropical forest structure is therefore an important component to global biomass and carbon monitoring. This paper shows preliminary results of a multibasline interfereomtric SAR (InSAR) experiment over primary, secondary, and selectively logged forests at La Selva Biological Station in Costa Rica. The profile shown results from inverse Fourier transforming 8 of the 18 baselines acquired. A profile is shown compared to lidar and field measurements. Results are highly preliminary and for qualitative assessment only. Parameter estimation will eventually replace Fourier inversion as the means to producing profiles.

Chemically Patterned Inverse Opal Created by a Selective Photolysis Modification Process.

PubMed

Tian, Tian; Gao, Ning; Gu, Chen; Li, Jian; Wang, Hui; Lan, Yue; Yin, Xianpeng; Li, Guangtao

2015-09-02

Anisotropic photonic crystal materials have long been pursued for their broad applications. A novel method for creating chemically patterned inverse opals is proposed here. The patterning technique is based on selective photolysis of a photolabile polymer together with postmodification on released amine groups. The patterning method allows regioselective modification within an inverse opal structure, taking advantage of selective chemical reaction. Moreover, combined with the unique signal self-reporting feature of the photonic crystal, the fabricated structure is capable of various applications, including gradient photonic bandgap and dynamic chemical patterns. The proposed method provides the ability to extend the structural and chemical complexity of the photonic crystal, as well as its potential applications.

The Lanchester square-law model extended to a (2,2) conflict

NASA Astrophysics Data System (ADS)

Colegrave, R. K.; Hyde, J. M.

1993-01-01

A natural extension of the Lanchester (1,1) square-law model is the (M,N) linear model in which M forces oppose N forces with constant attrition rates. The (2,2) model is treated from both direct and inverse viewpoints. The inverse problem means that the model is to be fitted to a minimum number of observed force levels, i.e. the attrition rates are to be found from the initial force levels together with the levels observed at two subsequent times. An approach based on Hamiltonian dynamics has enabled the authors to derive a procedure for solving the inverse problem, which is readily computerized. Conflicts in which participants unexpectedly rally or weaken must be excluded.

The distribution of seismic velocities and attenuation in the earth. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Hart, R. S.

1977-01-01

Estimates of the radial distribution of seismic velocities and density and of seismic attenuation within the earth are obtained through inversion of body wave, surface wave, and normal mode data. The effect of attenuation related dispersion on gross earth structure, and on the reliability of eigenperiod identifications is discussed. The travel time baseline discrepancies between body waves and free oscillation models are examined and largely resolved.

Reexamination of Total Fluid Intake and Bladder Cancer in the Health Professionals Follow-Up Study Cohort

PubMed Central

Zhou, Jiachen; Smith, Scott; Giovannucci, Edward; Michaud, Dominique S.

2012-01-01

It has been hypothesized that high fluid intake may reduce contact time between carcinogens and bladder epithelium and consequently reduce carcinogenesis. Epidemiologic studies examining fluid intake and bladder cancer have been extremely inconsistent, ranging from strong inverse to strong positive associations. The authors reevaluated the association between fluid intake and bladder cancer among 47,909 participants in the prospective Health Professionals Follow-up Study over a period of 22 years. During follow-up (1986–2008), 823 incident bladder cancer cases were diagnosed. Information on fluid intake was collected by using the food frequency questionnaire at baseline and every 4 years thereafter. Cox proportional hazard regression analysis was used to adjust for risk factors for bladder cancer. Total fluid intake was inversely associated with bladder cancer when the analysis was based on the baseline diet (relative risk = 0.76, 95% confidence interval: 0.60, 0.97), comparing the highest total daily fluid intake quintile (>2,531 mL/day) with the lowest quintile (<1,290 mL/day) (Ptrend = 0.01). However, no association was detected when the analysis was based on recent diet or cumulative updated diet. The updated analysis for total fluid intake and bladder cancer was attenuated compared with the original findings from the first 10-year follow-up period. PMID:22355034

Body Mass Index and Waist Circumference in Relation to Lung Cancer Risk in the Women's Health Initiative

PubMed Central

Kim, Mimi; Hunt, Julie R.; Chlebowski, Rowan T.; Rohan, Thomas E.

2008-01-01

Investigators in several epidemiologic studies have observed an inverse association between body mass index (BMI) and lung cancer risk, while others have not. The authors used data from the Women's Health Initiative to study the association of anthropometric factors with lung cancer risk. Over 8 years of follow-up (1998–2006), 1,365 incident lung cancer cases were ascertained among 161,809 women. Cox proportional hazards models were used to estimate hazard ratios adjusted for covariates. Baseline BMI was inversely associated with lung cancer in current smokers (highest quintile vs. lowest: hazard ratio (HR) = 0.62, 95% confidence interval (CI): 0.42, 0.92). When BMI and waist circumference were mutually adjusted, BMI was inversely associated with lung cancer risk in both current smokers and former smokers (HR = 0.40 (95% CI: 0.22, 0.72) and HR = 0.61 (95% CI: 0.40, 0.94), respectively), and waist circumference was positively associated with risk (HR = 1.56 (95% CI: 0.91, 2.69) and HR = 1.50 (95% CI: 0.98, 2.31), respectively). In never smokers, height showed a borderline positive association with lung cancer. These findings suggest that in smokers, BMI is inversely associated with lung cancer risk and that waist circumference is positively associated with risk. PMID:18483121

Quantum dynamics of a two-state system induced by a chirped zero-area pulse

NASA Astrophysics Data System (ADS)

Lee, Han-gyeol; Song, Yunheung; Kim, Hyosub; Jo, Hanlae; Ahn, Jaewook

2016-02-01

It is well known that area pulses make Rabi oscillation and chirped pulses in the adiabatic interaction regime induce complete population inversion of a two-state system. Here we show that chirped zero-area pulses could engineer an interplay between the adiabatic evolution and Rabi-like rotations. In a proof-of-principle experiment utilizing spectral chirping of femtosecond laser pulses with a resonant spectral hole, we demonstrate that the chirped zero-area pulses could induce, for example, complete population inversion and return of the cold rubidium atom two-state system. Experimental result agrees well with the theoretically considered overall dynamics, which could be approximately modeled to a Ramsey-like three-pulse interaction, where the x and z rotations are driven by the hole and the main pulse, respectively.

Toroidal Interaction and Propeller Chirality of Hexaarylbenzenes. Dynamic Domino Inversion Revealed by Combined Experimental and Theoretical Circular Dichroism Studies.

PubMed

Kosaka, Tomoyo; Inoue, Yoshihisa; Mori, Tadashi

2016-03-03

Hexaarylbenzenes (HABs) have greatly attracted much attention due to their unique propeller-shaped structure and potential application in materials science, such as liquid crystals, molecular capsules/rotors, redox materials, nonlinear optical materials, as well as molecular wires. Less attention has however been paid to their propeller chirality. By introducing small point-chiral group(s) at the periphery of HABs, propeller chirality was effectively induced, provoking strong Cotton effects in the circular dichroism (CD) spectrum. Temperature and solvent polarity manipulate the dynamics of propeller inversion in solution. As such, whizzing toroids become more substantial in polar solvents and at an elevated temperature, where radial aromatic rings (propeller blades) prefer orthogonal alignment against the central benzene ring (C6 core), maximizing toroidal interactions.

Peculiarities of spike multimode generation of a superradiant distributed feedback laser

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

Kocharovskaya, E R; Ginzburg, N S; Sergeev, A S

2011-08-31

Using one-dimensional semiclassical Maxwell - Bloch equations with account for the coherent polarisation dynamics, we have studied spike generation regimes of a superradiant distributed feedback laser in the case of inhomogeneous broadening of the spectral line of an active medium. By analysing the dynamic spectra of inversion of the active medium and laser radiation, we have revealed the relationship of individual spikes of radiation and their modulation with specific parts in the spectral line of the active medium and mode beatings. It has been shown that the broadening and shift of the lasing spectrum with respect to the initial electromagneticmore » Bragg-cavity modes is accompanied by a strong spectral gradient of inversion that is typical of the superradiant regimes. (control of radiation parameters)« less

A dynamical regularization algorithm for solving inverse source problems of elliptic partial differential equations

NASA Astrophysics Data System (ADS)

Zhang, Ye; Gong, Rongfang; Cheng, Xiaoliang; Gulliksson, Mårten

2018-06-01

This study considers the inverse source problem for elliptic partial differential equations with both Dirichlet and Neumann boundary data. The unknown source term is to be determined by additional boundary conditions. Unlike the existing methods found in the literature, which usually employ the first-order in time gradient-like system (such as the steepest descent methods) for numerically solving the regularized optimization problem with a fixed regularization parameter, we propose a novel method with a second-order in time dissipative gradient-like system and a dynamical selected regularization parameter. A damped symplectic scheme is proposed for the numerical solution. Theoretical analysis is given for both the continuous model and the numerical algorithm. Several numerical examples are provided to show the robustness of the proposed algorithm.

Dynamic rupture models of earthquakes on the Bartlett Springs Fault, Northern California

USGS Publications Warehouse

Lozos, Julian C.; Harris, Ruth A.; Murray, Jessica R.; Lienkaemper, James J.

2015-01-01

The Bartlett Springs Fault (BSF), the easternmost branch of the northern San Andreas Fault system, creeps along much of its length. Geodetic data for the BSF are sparse, and surface creep rates are generally poorly constrained. The two existing geodetic slip rate inversions resolve at least one locked patch within the creeping zones. We use the 3-D finite element code FaultMod to conduct dynamic rupture models based on both geodetic inversions, in order to determine the ability of rupture to propagate into the creeping regions, as well as to assess possible magnitudes for BSF ruptures. For both sets of models, we find that the distribution of aseismic creep limits the extent of coseismic rupture, due to the contrast in frictional properties between the locked and creeping regions.

Engineering Risk Assessment of Space Thruster Challenge Problem

NASA Technical Reports Server (NTRS)

Mathias, Donovan L.; Mattenberger, Christopher J.; Go, Susie

2014-01-01

The Engineering Risk Assessment (ERA) team at NASA Ames Research Center utilizes dynamic models with linked physics-of-failure analyses to produce quantitative risk assessments of space exploration missions. This paper applies the ERA approach to the baseline and extended versions of the PSAM Space Thruster Challenge Problem, which investigates mission risk for a deep space ion propulsion system with time-varying thruster requirements and operations schedules. The dynamic mission is modeled using a combination of discrete and continuous-time reliability elements within the commercially available GoldSim software. Loss-of-mission (LOM) probability results are generated via Monte Carlo sampling performed by the integrated model. Model convergence studies are presented to illustrate the sensitivity of integrated LOM results to the number of Monte Carlo trials. A deterministic risk model was also built for the three baseline and extended missions using the Ames Reliability Tool (ART), and results are compared to the simulation results to evaluate the relative importance of mission dynamics. The ART model did a reasonable job of matching the simulation models for the baseline case, while a hybrid approach using offline dynamic models was required for the extended missions. This study highlighted that state-of-the-art techniques can adequately adapt to a range of dynamic problems.

Dynamics of Mount Somma-Vesuvius edifice: from stress field inversion to analogue and numerical modelling

NASA Astrophysics Data System (ADS)

De Matteo, Ada; Massa, Bruno; D'Auria, Luca; Castaldo, Raffaele

2017-04-01

Geological processes are generally very complex and too slow to be directly observed in their completeness; modelling procedures overcome this limit. The state of stress in the upper lithosphere is the main responsible for driving geodynamical processes; in order to retrieve the active stress field in a rock volume, stress inversion techniques can be applied on both seismological and structural datasets. This approach has been successfully applied to active tectonics as well as volcanic areas. In this context the best approach in managing heterogeneous datasets in volcanic environments consists in the analysis of spatial variations of the stress field by applying robust techniques of inversion. The study of volcanic seismicity is an efficient tool to retrieve spatial and temporal pattern of the pre-, syn- and inter-eruptive stress field: magma migration as well as dynamics of magma chamber and hydrothermal system are directly connected to the volcanic seismicity. Additionally, analysis of the temporal variations of stress field pattern in volcanoes could be a useful monitoring tool. Recently the stress field acting on several active volcanoes has been investigated by using stress inversion techniques on seismological datasets (Massa et al., 2016). The Bayesian Right Trihedra Method (BRTM; D'Auria and Massa, 2015) is able to successfully manage heterogeneous datasets allowing the identification of regional fields locally overcame by the stress field due to volcano specific dynamics. In particular, the analysis of seismicity and stress field inversion at the Somma-Vesuvius highlighted the presence of two superposed volumes characterized by different behaviour and stress field pattern: a top volume dominated by an extensional stress field, in accordance with a gravitational spreading-style of deformation, and a bottom volume related to a regional extensional stress field. In addition, in order to evaluate the dynamics of deformation, both analogue and numerical modelling are being performed. Scaled analogue models of the Somma-Vesuvius are being built accordingly with the actual geometrical asymmetry of the volcano, varying just few parameters connected to the uncertainty of the depth and thickness of a buried decoupling layer. Experiments are being monitored by an optical stereo image system, useful to build a 3D time-lapsed models used to retrieve the model deformations. Simultaneously, a time-dependent 3D Finite Element model is being carried out in a fluid-dynamic context by fixing the same parameters of the proposed analogue model. Finally, a comparative analysis is being made between the model deformations and the DInSAR measurements derived from satellite data in order to estimate the uncertain parameters (i.e., thickness and viscosity of ductile layer). Preliminary results of the analogue models fit with the hypothesis of a spreading deformation active at the Somma-Vesuvius.

Molecular dynamics in principal component space.

PubMed

Michielssens, Servaas; van Erp, Titus S; Kutzner, Carsten; Ceulemans, Arnout; de Groot, Bert L

2012-07-26

A molecular dynamics algorithm in principal component space is presented. It is demonstrated that sampling can be improved without changing the ensemble by assigning masses to the principal components proportional to the inverse square root of the eigenvalues. The setup of the simulation requires no prior knowledge of the system; a short initial MD simulation to extract the eigenvectors and eigenvalues suffices. Independent measures indicated a 6-7 times faster sampling compared to a regular molecular dynamics simulation.

On the origin of bursts and heavy tails in animal dynamics

NASA Astrophysics Data System (ADS)

Reynolds, A. M.

2011-01-01

Over recent years there has been an accumulation of evidence that many animal behaviours are characterised by common scale-invariant patterns of switching between two contrasting activities over a period of time. This is evidenced in mammalian wake-sleep patterns, in the intermittent stop-start locomotion of Drosophila fruit flies, and in the Lévy walk movement patterns of a diverse range of animals in which straight-line movements are punctuated by occasional turns. Here it is shown that these dynamics can be modelled by a stochastic variant of Barabási’s model [A.-L. Barabási, The origin of bursts and heavy tails in human dynamics, Nature 435 (2005) 207-211] for bursts and heavy tails in human dynamics. The new model captures a tension between two competing and conflicting activities. The durations of one type of activity are distributed according to an inverse-square power-law, mirroring the ubiquity of inverse-square power-law scaling seen in empirical data. The durations of the second type of activity follow exponential distributions with characteristic timescales that depend on species and metabolic rates. This again is a common feature of animal behaviour. Bursty human dynamics, on the other hand, are characterised by power-law distributions with scaling exponents close to -1 and -3/2.

Review of Modelling Techniques for In Vivo Muscle Force Estimation in the Lower Extremities during Strength Training

PubMed Central

Schellenberg, Florian; Oberhofer, Katja; Taylor, William R.

2015-01-01

Background. Knowledge of the musculoskeletal loading conditions during strength training is essential for performance monitoring, injury prevention, rehabilitation, and training design. However, measuring muscle forces during exercise performance as a primary determinant of training efficacy and safety has remained challenging. Methods. In this paper we review existing computational techniques to determine muscle forces in the lower limbs during strength exercises in vivo and discuss their potential for uptake into sports training and rehabilitation. Results. Muscle forces during exercise performance have almost exclusively been analysed using so-called forward dynamics simulations, inverse dynamics techniques, or alternative methods. Musculoskeletal models based on forward dynamics analyses have led to considerable new insights into muscular coordination, strength, and power during dynamic ballistic movement activities, resulting in, for example, improved techniques for optimal performance of the squat jump, while quasi-static inverse dynamics optimisation and EMG-driven modelling have helped to provide an understanding of low-speed exercises. Conclusion. The present review introduces the different computational techniques and outlines their advantages and disadvantages for the informed usage by nonexperts. With sufficient validation and widespread application, muscle force calculations during strength exercises in vivo are expected to provide biomechanically based evidence for clinicians and therapists to evaluate and improve training guidelines. PMID:26417378

Learn the Lagrangian: A Vector-Valued RKHS Approach to Identifying Lagrangian Systems.

PubMed

Cheng, Ching-An; Huang, Han-Pang

2016-12-01

We study the modeling of Lagrangian systems with multiple degrees of freedom. Based on system dynamics, canonical parametric models require ad hoc derivations and sometimes simplification for a computable solution; on the other hand, due to the lack of prior knowledge in the system's structure, modern nonparametric models in machine learning face the curse of dimensionality, especially in learning large systems. In this paper, we bridge this gap by unifying the theories of Lagrangian systems and vector-valued reproducing kernel Hilbert space. We reformulate Lagrangian systems with kernels that embed the governing Euler-Lagrange equation-the Lagrangian kernels-and show that these kernels span a subspace capturing the Lagrangian's projection as inverse dynamics. By such property, our model uses only inputs and outputs as in machine learning and inherits the structured form as in system dynamics, thereby removing the need for the mundane derivations for new systems as well as the generalization problem in learning from scratches. In effect, it learns the system's Lagrangian, a simpler task than directly learning the dynamics. To demonstrate, we applied the proposed kernel to identify the robot inverse dynamics in simulations and experiments. Our results present a competitive novel approach to identifying Lagrangian systems, despite using only inputs and outputs.

Review of Modelling Techniques for In Vivo Muscle Force Estimation in the Lower Extremities during Strength Training.

PubMed

Schellenberg, Florian; Oberhofer, Katja; Taylor, William R; Lorenzetti, Silvio

2015-01-01

Knowledge of the musculoskeletal loading conditions during strength training is essential for performance monitoring, injury prevention, rehabilitation, and training design. However, measuring muscle forces during exercise performance as a primary determinant of training efficacy and safety has remained challenging. In this paper we review existing computational techniques to determine muscle forces in the lower limbs during strength exercises in vivo and discuss their potential for uptake into sports training and rehabilitation. Muscle forces during exercise performance have almost exclusively been analysed using so-called forward dynamics simulations, inverse dynamics techniques, or alternative methods. Musculoskeletal models based on forward dynamics analyses have led to considerable new insights into muscular coordination, strength, and power during dynamic ballistic movement activities, resulting in, for example, improved techniques for optimal performance of the squat jump, while quasi-static inverse dynamics optimisation and EMG-driven modelling have helped to provide an understanding of low-speed exercises. The present review introduces the different computational techniques and outlines their advantages and disadvantages for the informed usage by nonexperts. With sufficient validation and widespread application, muscle force calculations during strength exercises in vivo are expected to provide biomechanically based evidence for clinicians and therapists to evaluate and improve training guidelines.

Impact of baseline systolic blood pressure on visit-to-visit blood pressure variability: the Kailuan study.

PubMed

Wang, Anxin; Li, Zhifang; Yang, Yuling; Chen, Guojuan; Wang, Chunxue; Wu, Yuntao; Ruan, Chunyu; Liu, Yan; Wang, Yilong; Wu, Shouling

2016-01-01

To investigate the relationship between baseline systolic blood pressure (SBP) and visit-to-visit blood pressure variability in a general population. This is a prospective longitudinal cohort study on cardiovascular risk factors and cardiovascular or cerebrovascular events. Study participants attended a face-to-face interview every 2 years. Blood pressure variability was defined using the standard deviation and coefficient of variation of all SBP values at baseline and follow-up visits. The coefficient of variation is the ratio of the standard deviation to the mean SBP. We used multivariate linear regression models to test the relationships between SBP and standard deviation, and between SBP and coefficient of variation. Approximately 43,360 participants (mean age: 48.2±11.5 years) were selected. In multivariate analysis, after adjustment for potential confounders, baseline SBPs <120 mmHg were inversely related to standard deviation (P<0.001) and coefficient of variation (P<0.001). In contrast, baseline SBPs ≥140 mmHg were significantly positively associated with standard deviation (P<0.001) and coefficient of variation (P<0.001). Baseline SBPs of 120-140 mmHg were associated with the lowest standard deviation and coefficient of variation. The associations between baseline SBP and standard deviation, and between SBP and coefficient of variation during follow-ups showed a U curve. Both lower and higher baseline SBPs were associated with increased blood pressure variability. To control blood pressure variability, a good target SBP range for a general population might be 120-139 mmHg.

Crustal dynamics project session 4 validation and intercomparison experiments 1979-1980 report

NASA Technical Reports Server (NTRS)

Liebrecht, P.; Kolenkiewicz, R.; Ryan, J.; Hothem, L.

1983-01-01

As part of the Crustal Dynamics Project, an experiment was performed to verify the ability of Satellite Laser Ranging (SLR), Very Long Baseline interferometry (VLBI) and Doppler Satellite Positioning System (Doppler) techniques to estimate the baseline distances between several locations. The Goddard Space Flight Center (GSFC) lasers were in operation at all five sites available to them. The ten baselines involved were analyzed using monthly orbits and various methods of selecting data. The standard deviation of the monthly SLR baseline lengths was at the 7 cm level. The GSFC VLBI (Mark III) data was obtained during three separate experiments. November 1979 at Haystack and Owens Valley, and April and July 1980 at Haystack, Owens Valley, and Fort Davis. Repeatability of the VLBI in determining baseline lengths was calculated to be at the 2 cm level. Jet Propulsion Laboratory (JPL) VLBI (Mark II) data was acquired on the Owens Valley to Goldstone baseline on ten occasions between August 1979 and November 1980. The repeatability of these baseline length determinations was calculated to be at the 5 cm level. National Geodetic Survey (NGS) Doppler data was acquired at all five sites in January 1980. Repeatability of the Doppler determined baseline lengths results were calculated at approximately 30 cm. An intercomparison between baseline distances and associated parameters was made utilizing SLR, VLBI, and Doppler results on all available baselines. The VLBI and SLR length determinations were compared on four baselines with a resultant mean difference of -1 cm and a maximum difference of 12 cm. The SLR and Doppler length determinations were compared on ten baselines with a resultant mean difference of about 30 cm and a maximum difference of about 60 cm. The VLBI and Doppler lengths from seven baselines showed a resultant mean difference of about 30 cm and maximum difference of about 1 meter. The intercomparison of baseline orientation parameters were consistent with past analysis.

Cholesterol Efflux Capacity, High-Density Lipoprotein Particle Number, and Incident Cardiovascular Events: An Analysis From the JUPITER Trial (Justification for the Use of Statins in Prevention: An Intervention Trial Evaluating Rosuvastatin).

PubMed

Khera, Amit V; Demler, Olga V; Adelman, Steven J; Collins, Heidi L; Glynn, Robert J; Ridker, Paul M; Rader, Daniel J; Mora, Samia

2017-06-20

Recent failures of drugs that raised high-density lipoprotein (HDL) cholesterol levels to reduce cardiovascular events in clinical trials have led to increased interest in alternative indices of HDL quality, such as cholesterol efflux capacity, and HDL quantity, such as HDL particle number. However, no studies have directly compared these metrics in a contemporary population that includes potent statin therapy and low low-density lipoprotein cholesterol. HDL cholesterol levels, apolipoprotein A-I, cholesterol efflux capacity, and HDL particle number were assessed at baseline and 12 months in a nested case-control study of the JUPITER trial (Justification for the Use of Statins in Prevention: An Intervention Trial Evaluating Rosuvastatin), a randomized primary prevention trial that compared rosuvastatin treatment to placebo in individuals with normal low-density lipoprotein cholesterol but increased C-reactive protein levels. In total, 314 cases of incident cardiovascular disease (CVD) (myocardial infarction, unstable angina, arterial revascularization, stroke, or cardiovascular death) were compared to age- and gender-matched controls. Conditional logistic regression models adjusting for risk factors evaluated associations between HDL-related biomarkers and incident CVD. Cholesterol efflux capacity was moderately correlated with HDL cholesterol, apolipoprotein A-I, and HDL particle number (Spearman r = 0.39, 0.48, and 0.39 respectively; P <0.001). Baseline HDL particle number was inversely associated with incident CVD (adjusted odds ratio per SD increment [OR/SD], 0.69; 95% confidence interval [CI], 0.56-0.86; P <0.001), whereas no significant association was found for baseline cholesterol efflux capacity (OR/SD, 0.89; 95% CI, 0.72-1.10; P =0.28), HDL cholesterol (OR/SD, 0.82; 95% CI, 0.66-1.02; P =0.08), or apolipoprotein A-I (OR/SD, 0.83; 95% CI, 0.67-1.03; P =0.08). Twelve months of rosuvastatin (20 mg/day) did not change cholesterol efflux capacity (average percentage change -1.5%, 95% CI, -13.3 to +10.2; P =0.80), but increased HDL cholesterol (+7.7%), apolipoprotein A-I (+4.3%), and HDL particle number (+5.2%). On-statin cholesterol efflux capacity was inversely associated with incident CVD (OR/SD, 0.62; 95% CI, 0.42-0.92; P =0.02), although HDL particle number again emerged as the strongest predictor (OR/SD, 0.51; 95% CI, 0.33-0.77; P <0.001). In JUPITER, cholesterol efflux capacity was associated with incident CVD in individuals on potent statin therapy but not at baseline. For both baseline and on-statin analyses, HDL particle number was the strongest of 4 HDL-related biomarkers as an inverse predictor of incident events and biomarker of residual risk. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00239681. © 2017 American Heart Association, Inc.

Interferometric inverse synthetic aperture radar imaging for space targets based on wideband direct sampling using two antennas

NASA Astrophysics Data System (ADS)

Tian, Biao; Liu, Yang; Xu, Shiyou; Chen, Zengping

2014-01-01

Interferometric inverse synthetic aperture radar (InISAR) imaging provides complementary information to monostatic inverse synthetic aperture radar (ISAR) imaging. This paper proposes a new InISAR imaging system for space targets based on wideband direct sampling using two antennas. The system is easy to realize in engineering since the motion trajectory of space targets can be known in advance, which is simpler than that of three receivers. In the preprocessing step, high speed movement compensation is carried out by designing an adaptive matched filter containing speed that is obtained from the narrow band information. Then, the coherent processing and keystone transform for ISAR imaging are adopted to reserve the phase history of each antenna. Through appropriate collocation of the system, image registration and phase unwrapping can be avoided. Considering the situation not to be satisfied, the influence of baseline variance is analyzed and compensation method is adopted. The corresponding size can be achieved by interferometric processing of the two complex ISAR images. Experimental results prove the validity of the analysis and the three-dimensional imaging algorithm.

Optimal aperture synthesis radar imaging

NASA Astrophysics Data System (ADS)

Hysell, D. L.; Chau, J. L.

2006-03-01

Aperture synthesis radar imaging has been used to investigate coherent backscatter from ionospheric plasma irregularities at Jicamarca and elsewhere for several years. Phenomena of interest include equatorial spread F, 150-km echoes, the equatorial electrojet, range-spread meteor trails, and mesospheric echoes. The sought-after images are related to spaced-receiver data mathematically through an integral transform, but direct inversion is generally impractical or suboptimal. We instead turn to statistical inverse theory, endeavoring to utilize fully all available information in the data inversion. The imaging algorithm used at Jicamarca is based on an implementation of the MaxEnt method developed for radio astronomy. Its strategy is to limit the space of candidate images to those that are positive definite, consistent with data to the degree required by experimental confidence limits; smooth (in some sense); and most representative of the class of possible solutions. The algorithm was improved recently by (1) incorporating the antenna radiation pattern in the prior probability and (2) estimating and including the full error covariance matrix in the constraints. The revised algorithm is evaluated using new 28-baseline electrojet data from Jicamarca.

A systematic linear space approach to solving partially described inverse eigenvalue problems

NASA Astrophysics Data System (ADS)

Hu, Sau-Lon James; Li, Haujun

2008-06-01

Most applications of the inverse eigenvalue problem (IEP), which concerns the reconstruction of a matrix from prescribed spectral data, are associated with special classes of structured matrices. Solving the IEP requires one to satisfy both the spectral constraint and the structural constraint. If the spectral constraint consists of only one or few prescribed eigenpairs, this kind of inverse problem has been referred to as the partially described inverse eigenvalue problem (PDIEP). This paper develops an efficient, general and systematic approach to solve the PDIEP. Basically, the approach, applicable to various structured matrices, converts the PDIEP into an ordinary inverse problem that is formulated as a set of simultaneous linear equations. While solving simultaneous linear equations for model parameters, the singular value decomposition method is applied. Because of the conversion to an ordinary inverse problem, other constraints associated with the model parameters can be easily incorporated into the solution procedure. The detailed derivation and numerical examples to implement the newly developed approach to symmetric Toeplitz and quadratic pencil (including mass, damping and stiffness matrices of a linear dynamic system) PDIEPs are presented. Excellent numerical results for both kinds of problem are achieved under the situations that have either unique or infinitely many solutions.

Earthquake Source Inversion Blindtest: Initial Results and Further Developments

NASA Astrophysics Data System (ADS)

Mai, P.; Burjanek, J.; Delouis, B.; Festa, G.; Francois-Holden, C.; Monelli, D.; Uchide, T.; Zahradnik, J.

2007-12-01

Images of earthquake ruptures, obtained from modelling/inverting seismic and/or geodetic data exhibit a high degree in spatial complexity. This earthquake source heterogeneity controls seismic radiation, and is determined by the details of the dynamic rupture process. In turn, such rupture models are used for studying source dynamics and for ground-motion prediction. But how reliable and trustworthy are these earthquake source inversions? Rupture models for a given earthquake, obtained by different research teams, often display striking disparities (see http://www.seismo.ethz.ch/srcmod) However, well resolved, robust, and hence reliable source-rupture models are an integral part to better understand earthquake source physics and to improve seismic hazard assessment. Therefore it is timely to conduct a large-scale validation exercise for comparing the methods, parameterization and data-handling in earthquake source inversions.We recently started a blind test in which several research groups derive a kinematic rupture model from synthetic seismograms calculated for an input model unknown to the source modelers. The first results, for an input rupture model with heterogeneous slip but constant rise time and rupture velocity, reveal large differences between the input and inverted model in some cases, while a few studies achieve high correlation between the input and inferred model. Here we report on the statistical assessment of the set of inverted rupture models to quantitatively investigate their degree of (dis-)similarity. We briefly discuss the different inversion approaches, their possible strength and weaknesses, and the use of appropriate misfit criteria. Finally we present new blind-test models, with increasing source complexity and ambient noise on the synthetics. The goal is to attract a large group of source modelers to join this source-inversion blindtest in order to conduct a large-scale validation exercise to rigorously asses the performance and reliability of current inversion methods and to discuss future developments.

Identification and Control of Non-Linear Time-Varying Dynamical Systems Using Artificial Neural Networks

DTIC Science & Technology

1992-09-01

finding an inverse plant such as was done by Bertrand [BD91] and by Levin, Gewirtzman and Inbar in a binary type inverse controller [LGI91], to self tuning...gain robust control. 2) Self oscillating adaptive controller. 3) Gain scheduling. 4) Self tuning. 5) Model-reference adaptive systems. Although the...of multidimensional systems (CS881 as well as aircraft [HG90]. The self oscillating method is also a feedback based mechanism, utilizing a relay in the

Representation of Complex Spectra in Auditory Cortex

DTIC Science & Technology

1997-01-01

predict the response to any broadband dynamic sound. Fourier Transform Inverse Transform ∫ [.] exp(±2πjΩx±2πjwt) 2 1 2 / 1 1 a 2 1 2 / 1 1 a...Systems Research University of Maryland Spectro-Temporal Transform Ω wx = log f t w = “ripple velocity” Ω = “ripple frequency” Fourier Transform Inverse ... Transform ∫ [.] exp(±2πjΩx±2πjwt) Real functions in the spectro-temporal domain give rise to complex conjugate symmetric functions in the Fourier

Mantle Circulation Models with variational data assimilation: Inferring past mantle flow and structure from plate motion histories and seismic tomography

NASA Astrophysics Data System (ADS)

Bunge, H.; Hagelberg, C.; Travis, B.

2002-12-01

EarthScope will deliver data on structure and dynamics of continental North America and the underlying mantle on an unprecedented scale. Indeed, the scope of EarthScope makes its mission comparable to the large remote sensing efforts that are transforming the oceanographic and atmospheric sciences today. Arguably the main impact of new solid Earth observing systems is to transform our use of geodynamic models increasingly from conditions that are data poor to an environment that is data rich. Oceanographers and meteorologists already have made substantial progress in adapting to this environment, by developing new approaches of interpreting oceanographic and atmospheric data objectively through data assimilation methods in their models. However, a similarly rigorous theoretical framework for merging EarthScope derived solid Earth data with geodynamic models has yet to be devised. Here we explore the feasibility of data assimilation in mantle convection studies in an attempt to fit global geodynamic model calculations explicitly to tomographic and tectonic constraints. This is an inverse problem not quite unlike the inverse problem of finding optimal seismic velocity structures faced by seismologists. We derive the generalized inverse of mantle convection from a variational approach and present the adjoint equations of mantle flow. The substantial computational burden associated with solutions to the generalized inverse problem of mantle convection is made feasible using a highly efficient finite element approach based on the 3-D spherical fully parallelized mantle dynamics code TERRA, implemented on a cost-effective topical PC-cluster (geowulf) dedicated specifically to large-scale geophysical simulations. This dedicated geophysical modeling computer allows us to investigate global inverse convection problems having a spatial discretization of less than 50 km throughout the mantle. We present a synthetic high-resolution modeling experiment to demonstrate that mid-Cretaceous mantle structure can be inferred accurately from our inverse approach assuming present-day mantle structure is well-known, even if an initial first guess assumption about the mid-Cretaceous mantle involved only a simple 1-D radial temperature profile. We suggest that geodynamic inverse modeling should make it possible to infer a number of flow parameters from observational constraints of the mantle.

The selection of the optimal baseline in the front-view monocular vision system

NASA Astrophysics Data System (ADS)

Xiong, Bincheng; Zhang, Jun; Zhang, Daimeng; Liu, Xiaomao; Tian, Jinwen

2018-03-01

In the front-view monocular vision system, the accuracy of solving the depth field is related to the length of the inter-frame baseline and the accuracy of image matching result. In general, a longer length of the baseline can lead to a higher precision of solving the depth field. However, at the same time, the difference between the inter-frame images increases, which increases the difficulty in image matching and the decreases matching accuracy and at last may leads to the failure of solving the depth field. One of the usual practices is to use the tracking and matching method to improve the matching accuracy between images, but this algorithm is easy to cause matching drift between images with large interval, resulting in cumulative error in image matching, and finally the accuracy of solving the depth field is still very low. In this paper, we propose a depth field fusion algorithm based on the optimal length of the baseline. Firstly, we analyze the quantitative relationship between the accuracy of the depth field calculation and the length of the baseline between frames, and find the optimal length of the baseline by doing lots of experiments; secondly, we introduce the inverse depth filtering technique for sparse SLAM, and solve the depth field under the constraint of the optimal length of the baseline. By doing a large number of experiments, the results show that our algorithm can effectively eliminate the mismatch caused by image changes, and can still solve the depth field correctly in the large baseline scene. Our algorithm is superior to the traditional SFM algorithm in time and space complexity. The optimal baseline obtained by a large number of experiments plays a guiding role in the calculation of the depth field in front-view monocular.

Dietary fat intake and quality of life: the SUN project.

PubMed

Ruano, Cristina; Henriquez, Patricia; Bes-Rastrollo, Maira; Ruiz-Canela, Miguel; del Burgo, Cristina López; Sánchez-Villegas, Almudena

2011-11-02

Few studies have related nutritional factors with quality of life in healthy populations. The purpose of the study was to assess whether dietary fat intake is associated to mental and physical quality of life. This analysis included 8,430 participants from the SUN (Seguimiento Universidad de Navarra) Project. The intake of saturated fatty acids (SFA), polyunsaturated fatty acids (PUFA), trans unsaturated fatty acids (TFA), and monounsaturated fatty acids (MUFA) was assessed through a 136-item food frequency questionnaire at baseline. Quality of life was measured with the SF-36 Health Survey after 4 years of follow-up. Generalized Linear Models were fitted to assess the regression coefficients (b) and their 95% confidence intervals (95% CI) for the 8 domains of the SF-36 according to successive quintiles of each kind of fatty acids intake. The multivariate-adjusted models revealed a significant inverse association for SFA intake (in quintiles) and two of the physical domains (physical functioning and general health). E.g. for general health domain: (highest quintile of intake (Q5) vs. lowest quintile (Q1), b = -1.6; 95% CI = -3.1, -0.1. General health also showed a dose-response relationship (p for trend < 0.05). For TFA intake (in quintiles), a significant inverse association was found for most of the mental domains (vitality, social functioning and role emotional). E.g. for vitality domain (Q5) vs. (Q1), b = -2.0, 95% CI = -3.4 to -0.6. We also found an inverse association between TFA intake and the bodily pain domain: (Q5 vs. Q1), b = -2.6; 95% CI = -4.4 to -0.8, with a statistically significant dose-response relationship (p for trend < 0.05). Except for TFA intake and the mental domains, the rest of the associations were attenuated when we repeated the analysis adjusting for adherence to the Mediterranean diet. A detrimental relationship between TFA intake at baseline and most of the SF-36 mental domains measured 4 years later were found, whereas weak inverse associations were found for SFA intake and some physical domains.

Scandinavia studies of recent crustal movements and the space geodetic baseline network

NASA Technical Reports Server (NTRS)

Anderson, A. J.

1980-01-01

A brief review of crustal movements within the Fenno-Scandia shield is given. Results from postglacial studies, projects for measuring active fault regions, and dynamic ocean loading experiments are presented. The 1979 Scandinavian Doppler Campaign Network is discussed. This network includes Doppler translocation baseline determination of future very long baseline interferometry baselines to be measured in Scandinavia. Intercomparison of earlier Doppler translocation measurements with a high precision terrestrial geodetic baseline in Scandinavia has yielded internal agreement of 6 cm over 887 km. This is a precision of better than 1 part in to the 7th power.

Inverse Analysis of Cavitation Impact Phenomena on Structures

DTIC Science & Technology

2007-07-02

can occur within different types of dynamic water environments of structures. Case study analyses using experimental data are used to demonstrate the...cavitation impact phenomena, and ultimately, with cavitation erosion of structures within turbulent water environments. 02-07-2007 Memorandum Report...of dynamic water environments of structures. Case study analyses using experimental data are used to demonstrate the fundamentals of various aspects

Langevin Dynamics Simulations of Genome Packing in Bacteriophage

PubMed Central

Forrey, Christopher; Muthukumar, M.

2006-01-01

We use Langevin dynamics simulations to study the process by which a coarse-grained DNA chain is packaged within an icosahedral container. We focus our inquiry on three areas of interest in viral packing: the evolving structure of the packaged DNA condensate; the packing velocity; and the internal buildup of energy and resultant forces. Each of these areas has been studied experimentally, and we find that we can qualitatively reproduce experimental results. However, our findings also suggest that the phage genome packing process is fundamentally different than that suggested by the inverse spool model. We suggest that packing in general does not proceed in the deterministic fashion of the inverse-spool model, but rather is stochastic in character. As the chain configuration becomes compressed within the capsid, the structure, energy, and packing velocity all become dependent upon polymer dynamics. That many observed features of the packing process are rooted in condensed-phase polymer dynamics suggests that statistical mechanics, rather than mechanics, should serve as the proper theoretical basis for genome packing. Finally we suggest that, as a result of an internal protein unique to bacteriophage T7, the T7 genome may be significantly more ordered than is true for bacteriophage in general. PMID:16617089

Langevin dynamics simulations of genome packing in bacteriophage.

PubMed

Forrey, Christopher; Muthukumar, M

2006-07-01

We use Langevin dynamics simulations to study the process by which a coarse-grained DNA chain is packaged within an icosahedral container. We focus our inquiry on three areas of interest in viral packing: the evolving structure of the packaged DNA condensate; the packing velocity; and the internal buildup of energy and resultant forces. Each of these areas has been studied experimentally, and we find that we can qualitatively reproduce experimental results. However, our findings also suggest that the phage genome packing process is fundamentally different than that suggested by the inverse spool model. We suggest that packing in general does not proceed in the deterministic fashion of the inverse-spool model, but rather is stochastic in character. As the chain configuration becomes compressed within the capsid, the structure, energy, and packing velocity all become dependent upon polymer dynamics. That many observed features of the packing process are rooted in condensed-phase polymer dynamics suggests that statistical mechanics, rather than mechanics, should serve as the proper theoretical basis for genome packing. Finally we suggest that, as a result of an internal protein unique to bacteriophage T7, the T7 genome may be significantly more ordered than is true for bacteriophage in general.

Simultaneous functional photoacoustic microscopy and electrocorticography reveal the impact of rtPA on dynamic neurovascular functions after cerebral ischemia.

PubMed

Bandla, Aishwarya; Liao, Lun-De; Chan, Su Jing; Ling, Ji Min; Liu, Yu-Hang; Shih, Yen-Yu Ian; Pan, Han-Chi; Wong, Peter Tsun-Hon; Lai, Hsin-Yi; King, Nicolas Kon Kam; Chen, You-Yin; Ng, Wai Hoe; Thakor, Nitish V

2018-06-01

The advance of thrombolytic therapy has been hampered by the lack of optimization of the therapy during the hyperacute phase of focal ischemia. Here, we investigate neurovascular dynamics using a custom-designed hybrid electrocorticography (ECoG)-functional photoacoustic microscopy (fPAM) imaging system during the hyperacute phase (first 6 h) of photothrombotic ischemia (PTI) in male Wistar rats following recombinant tissue plasminogen activator (rtPA)-mediated thrombolysis. We reported, for the first time, the changes in neural activity and cerebral hemodynamic responses following rtPA infusion at different time points post PTI. Interestingly, very early administration of rtPA (< 1 h post PTI) resulted in only partial recovery of neurovascular dynamics (specifically , neural activity recovered to 71 ± 3.5% of baseline and hemodynamics to only 52 ± 2.6% of baseline) and late administration of rtPA (> 4 h post PTI) resulted in the deterioration of neurovascular function. A therapeutic window between 1 and 3 h post PTI was found to improve recovery of neurovascular function (i.e. significant restoration of neural activity to 93 ± 4.2% of baseline and hemodynamics to 81 ± 2.1% of baseline, respectively). The novel combination of fPAM and ECoG enables direct mapping of neurovascular dynamics and serves as a platform to evaluate potential interventions for stroke.

Intakes of Vitamin B6 and Dietary Fiber and Clinical Course of Systemic Lupus Erythematosus: A Prospective Study of Japanese Female Patients

PubMed Central

Minami, Yuko; Hirabayashi, Yasuhiko; Nagata, Chisato; Ishii, Tomonori; Harigae, Hideo; Sasaki, Takeshi

2011-01-01

Background Intakes of selected vitamins and dietary fiber may influence the clinical course of systemic lupus erythematosus (SLE). Using a cohort study method, we investigated the associations of dietary intake of vitamin B6 and B12, folate, and dietary fiber with the risk of active disease and atherosclerotic vascular events in SLE. Methods The study included female SLE patients in the Miyagi Lupus Cohort, which was founded in 1995. Dietary nutrients at baseline were estimated by a semiquantitative food frequency questionnaire. The association of each nutrient intake with the risk of active disease was investigated in 216 patients who had inactive disease at baseline. The association with atherosclerotic vascular events was assessed in 196 women who had inactive disease and no history of atherosclerotic diseases at baseline. Results Forty-three cases of active disease were identified during 9966 person-months of follow-up (1995–1999). During 19 575 person-months of follow-up (1995–2005), 20 atherosclerotic vascular events were documented. The Cox proportional hazards model revealed an inverse association between vitamin B6 intake and the risk of active disease (hazard ratio for the highest as compared with the lowest tertile, 0.41; 95% confidence interval, 0.18–0.97; P for trend = 0.04). An inverse association was also found for dietary fiber intake (P for trend = 0.01). However, no significant association was observed between intakes of these nutrients and the risk of atherosclerotic vascular events. Conclusions Higher intake of vitamin B6 and dietary fiber may prevent the occurrence of active disease in SLE. PMID:21515941

Micronutrient status in middle childhood and age at menarche: results from the Bogotá School Children Cohort.

PubMed

Villamor, Eduardo; Marín, Constanza; Mora-Plazas, Mercedes; Oliveros, Henry

2017-12-01

Childhood intake of animal foods is associated with age at first menstrual period (menarche). It is unknown whether the micronutrients present in these foods could explain this association. Our objective was to investigate the associations of micronutrient status biomarkers in middle childhood with age at menarche. We quantified circulating Hb, ferritin, mean corpuscular volume, Zn, vitamin B12, erythrocyte folate and retinol in 1464 pre-menarcheal girls aged 5-12 years in Bogotá, Colombia, and followed them for a median 5·7 years for the occurrence and date of menarche. We estimated median age at menarche and hazard ratios (HR) with 95 % CI by levels of each biomarker with use of Kaplan-Meier survival probabilities and Cox regression, respectively. Median age at menarche was 12·4 years. Middle childhood Hb was inversely related to age at menarche whereas plasma ferritin was positively associated with this outcome in a linear manner. HR of menarche for every 1 sd of Hb (11 g/l) and ferritin (23·2 µg/l) were 1·11 (95 % CI 1·04, 1·18; P=0·001) and 0·94 (95 % CI 0·88, 0·99; P=0·02), respectively, after adjustment for baseline age, C-reactive protein concentration, maternal age at menarche and parity and socioeconomic status. The association with ferritin was stronger in girls aged 9-10 years at baseline. Additional adjustment for baseline height- and BMI-for-age did not change the results. We conclude that higher Fe status in middle childhood is related to later age at menarche whereas Hb concentrations are inversely associated with age at onset of menses.

Vitamin D Supplementation Does Not Impact Insulin Resistance in Black and White Children.

PubMed

Ferira, Ashley J; Laing, Emma M; Hausman, Dorothy B; Hall, Daniel B; McCabe, George P; Martin, Berdine R; Hill Gallant, Kathleen M; Warden, Stuart J; Weaver, Connie M; Peacock, Munro; Lewis, Richard D

2016-04-01

Vitamin D supplementation trials with diabetes-related outcomes have been conducted almost exclusively in adults and provide equivocal findings. The objective of this study was to determine the dose-response of vitamin D supplementation on fasting glucose, insulin, and a surrogate measure of insulin resistance in white and black children aged 9–13 years, who participated in the Georgia, Purdue, and Indiana University (or GAPI) trial: a 12-week multisite, randomized, triple-masked, dose-response, placebo-controlled vitamin D trial. Black and white children in the early stages of puberty (N = 323, 50% male, 51% black) were equally randomized to receive vitamin D3 (0, 400, 1000, 2000, or 4000 IU/day) for 12 weeks. Fasting serum 25-hydroxyvitamin D (25(OH)D), glucose and insulin were assessed at baseline and weeks 6 and 12. Homeostasis model assessment of insulin resistance was used as a surrogate measure of insulin resistance. Statistical analyses were conducted as intent-to-treat using a mixed effects model. Baseline serum 25(OH)D was inversely associated with insulin (r = −0.140, P = 0.017) and homeostasis model assessment of insulin resistance (r = −0.146, P = 0.012) after adjusting for race, sex, age, pubertal maturation, fat mass, and body mass index. Glucose, insulin, and insulin resistance increased (F > 5.79, P < .003) over the 12 weeks, despite vitamin D dose-dependent increases in serum 25(OH)D. Despite significant baseline inverse relationships between serum 25(OH)D and measures of insulin resistance, vitamin D supplementation had no impact on fasting glucose, insulin, or a surrogate measure of insulin resistance over 12 weeks in apparently healthy children.

Three-dimensional audio-magnetotelluric sounding in monitoring coalbed methane reservoirs

NASA Astrophysics Data System (ADS)

Wang, Nan; Zhao, Shanshan; Hui, Jian; Qin, Qiming

2017-03-01

Audio-magnetotelluric (AMT) sounding is widely employed in rapid resistivity delineation of objective geometry in near surface exploration. According to reservoir patterns and electrical parameters obtained in Qinshui Basin, China, two-dimensional and three-dimensional synthetic "objective anomaly" models were designed and inverted with the availability of a modular system for electromagnetic inversion (ModEM). The results revealed that 3-D full impedance inversion yielded the subsurface models closest to synthetic models. One or more conductive targets were correctly recovered. Therefore, conductive aquifers in the study area, including hydrous coalbed methane (CBM) reservoirs, were suggested to be the interpretation signs for reservoir characterization. With the aim of dynamic monitoring of CBM reservoirs, the AMT surveys in continuous years (June 2013-May 2015) were carried out. 3-D inversion results demonstrated that conductive anomalies accumulated around the producing reservoirs at the corresponding depths if CBM reservoirs were in high water production rates. In contrast, smaller conductive anomalies were generally identical with rapid gas production or stopping production of reservoirs. These analyses were in accordance with actual production history of CBM wells. The dynamic traces of conductive anomalies revealed that reservoir water migrated deep or converged in axial parts and wings of folds, which contributed significantly to formations of CBM traps. Then the well spacing scenario was also evaluated based on the dynamic production analysis. Wells distributed near closed faults or flat folds, rather than open faults, had CBM production potential to ascertain stable gas production. Therefore, three-dimensional AMT sounding becomes an attractive option with the ability of dynamic monitoring of CBM reservoirs, and lays a solid foundation of quantitative evaluation of reservoir parameters.

Onset of normal and inverse homoclinic bifurcation in a double plasma system near a plasma fireball

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

Mitra, Vramori; Sarma, Bornali; Sarma, Arun

Plasma fireballs are generated due to a localized discharge and appear as a luminous glow with a sharp boundary, which suggests the presence of a localized electric field such as electrical sheath or double layer structure. The present work reports the observation of normal and inverse homoclinic bifurcation phenomena in plasma oscillations that are excited in the presence of fireball in a double plasma device. The controlling parameters for these observations are the ratio of target to source chamber (n{sub T}/n{sub S}) densities and applied electrode voltage. Homoclinic bifurcation is noticed in the plasma potential fluctuations as the system evolvesmore » from narrow to long time period oscillations and vice versa with the change of control parameter. The dynamical transition in plasma fireball is demonstrated by spectral analysis, recurrence quantification analysis (RQA), and statistical measures, viz., skewness and kurtosis. The increasing trend of normalized variance reflects that enhancing n{sub T}/n{sub S} induces irregularity in plasma dynamics. The exponential growth of the time period is strongly indicative of homoclinic bifurcation in the system. The gradual decrease of skewness and increase of kurtosis with the increase of n{sub T}/n{sub S} also reflect growing complexity in the system. The visual change of recurrence plot and gradual enhancement of RQA variables DET, L{sub max}, and ENT reflects the bifurcation behavior in the dynamics. The combination of RQA and spectral analysis is a clear evidence that homoclinic bifurcation occurs due to the presence of plasma fireball with different density ratios. However, inverse bifurcation takes place due to the change of fireball voltage. Some of the features observed in the experiment are consistent with a model that describes the dynamics of ionization instabilities.« less

Inverse Force Determination on a Small Scale Launch Vehicle Model Using a Dynamic Balance

NASA Technical Reports Server (NTRS)

Ngo, Christina L.; Powell, Jessica M.; Ross, James C.

2017-01-01

A launch vehicle can experience large unsteady aerodynamic forces in the transonic regime that, while usually only lasting for tens of seconds during launch, could be devastating if structural components and electronic hardware are not designed to account for them. These aerodynamic loads are difficult to experimentally measure and even harder to computationally estimate. The current method for estimating buffet loads is through the use of a few hundred unsteady pressure transducers and wind tunnel test. Even with a large number of point measurements, the computed integrated load is not an accurate enough representation of the total load caused by buffeting. This paper discusses an attempt at using a dynamic balance to experimentally determine buffet loads on a generic scale hammer head launch vehicle model tested at NASA Ames Research Center's 11' x 11' transonic wind tunnel. To use a dynamic balance, the structural characteristics of the model needed to be identified so that the natural modal response could be and removed from the aerodynamic forces. A finite element model was created on a simplified version of the model to evaluate the natural modes of the balance flexures, assist in model design, and to compare to experimental data. Several modal tests were conducted on the model in two different configurations to check for non-linearity, and to estimate the dynamic characteristics of the model. The experimental results were used in an inverse force determination technique with a psuedo inverse frequency response function. Due to the non linearity, the model not being axisymmetric, and inconsistent data between the two shake tests from different mounting configuration, it was difficult to create a frequency response matrix that satisfied all input and output conditions for wind tunnel configuration to accurately predict unsteady aerodynamic loads.

Simulation of the Tsunami Resulting from the M 9.2 2004 Sumatra-Andaman Earthquake - Dynamic Rupture vs. Seismic Inversion Source Model

NASA Astrophysics Data System (ADS)

Vater, Stefan; Behrens, Jörn

2017-04-01

Simulations of historic tsunami events such as the 2004 Sumatra or the 2011 Tohoku event are usually initialized using earthquake sources resulting from inversion of seismic data. Also, other data from ocean buoys etc. is sometimes included in the derivation of the source model. The associated tsunami event can often be well simulated in this way, and the results show high correlation with measured data. However, it is unclear how the derived source model compares to the particular earthquake event. In this study we use the results from dynamic rupture simulations obtained with SeisSol, a software package based on an ADER-DG discretization solving the spontaneous dynamic earthquake rupture problem with high-order accuracy in space and time. The tsunami model is based on a second-order Runge-Kutta discontinuous Galerkin (RKDG) scheme on triangular grids and features a robust wetting and drying scheme for the simulation of inundation events at the coast. Adaptive mesh refinement enables the efficient computation of large domains, while at the same time it allows for high local resolution and geometric accuracy. The results are compared to measured data and results using earthquake sources based on inversion. With the approach of using the output of actual dynamic rupture simulations, we can estimate the influence of different earthquake parameters. Furthermore, the comparison to other source models enables a thorough comparison and validation of important tsunami parameters, such as the runup at the coast. This work is part of the ASCETE (Advanced Simulation of Coupled Earthquake and Tsunami Events) project, which aims at an improved understanding of the coupling between the earthquake and the generated tsunami event.

Relations of hedonic hunger and behavioral change to weight loss among adults in a behavioral weight loss program utilizing meal-replacement products.

PubMed

Theim, Kelly R; Brown, Joshua D; Juarascio, Adrienne S; Malcolm, Robert R; O'Neil, Patrick M

2013-11-01

Greater self-regulatory behavior usage is associated with greater weight loss within behavioral weight loss treatments. Hedonic hunger (i.e., susceptibility to environmental food cues) may impede successful behavior change and weight loss. Adult men and women (N = 111, body mass index M ± SD = 35.89 ± 6.97 kg/m(2)) were assessed before and after a 15-week lifestyle change weight loss program with a partial meal-replacement diet. From pre- to post-treatment, reported weight control behavior usage improved and hedonic hunger decreased, and these changes were inversely related. Individuals with higher hedonic hunger scores at baseline showed the greatest weight loss. Similarly, participants with lower baseline use of weight control behaviors lost more weight, and increased weight control behavior usage was associated with greater weight loss-particularly among individuals with low baseline hedonic hunger. Further study is warranted regarding the significance of hedonic hunger in weight loss treatments.

The Impact of Exercise, Cognitive Activities, and Socialization on Cognitive Function: Results From the National Long-Term Care Survey

PubMed Central

Jedrziewski, M. Kathryn; Ewbank, Douglas C.; Wang, Haidong; Trojanowski, John Q.

2014-01-01

Currently, there are no effective treatments for Alzheimer’s disease and related disorders and age continues to be a robust risk factor. Thus, population aging in the United States may have catastrophic results if interventions are not found and implemented. This study examines possible associations between cognitive impairment and exercise, cognitive activities, and socialization. Cognitive activities, socialization, and exercise were assessed at baseline, and cognitive function was measured at baseline, 5-year, and 10-year follow-up. Controlling for baseline cognitive function, age, sex, education, diabetes, and hypertension, linear regression was performed. Engagement in cognitive activities was inversely associated with the onset of cognitive impairment at 5-year follow-up but was no longer significant at 10-year follow-up. Exercise was associated with a lower risk of cognitive impairment at 10-year follow-up but was not significant at 5-year follow-up. Associations with socialization were not statistically significant at either follow-up. PMID:24408752

Antisynchronization of Two Complex Dynamical Networks

NASA Astrophysics Data System (ADS)

Banerjee, Ranjib; Grosu, Ioan; Dana, Syamal K.

A nonlinear type open-plus-closed-loop (OPCL) coupling is investi-gated for antisynchronization of two complex networks under unidirectional and bidirectional interactions where each node of the networks is considered as a continuous dynamical system. We present analytical results for antisynchroni-zation in identical networks. A numerical example is given for unidirectional coupling with each node represented by a spiking-bursting type Hindmarsh-Rose neuron model. Antisynchronization for mutual interaction is allowed only to inversion symmetric dynamical systems as chosen nodes.

Continuous time random walk model with asymptotical probability density of waiting times via inverse Mittag-Leffler function

NASA Astrophysics Data System (ADS)

Liang, Yingjie; Chen, Wen

2018-04-01

The mean squared displacement (MSD) of the traditional ultraslow diffusion is a logarithmic function of time. Recently, the continuous time random walk model is employed to characterize this ultraslow diffusion dynamics by connecting the heavy-tailed logarithmic function and its variation as the asymptotical waiting time density. In this study we investigate the limiting waiting time density of a general ultraslow diffusion model via the inverse Mittag-Leffler function, whose special case includes the traditional logarithmic ultraslow diffusion model. The MSD of the general ultraslow diffusion model is analytically derived as an inverse Mittag-Leffler function, and is observed to increase even more slowly than that of the logarithmic function model. The occurrence of very long waiting time in the case of the inverse Mittag-Leffler function has the largest probability compared with the power law model and the logarithmic function model. The Monte Carlo simulations of one dimensional sample path of a single particle are also performed. The results show that the inverse Mittag-Leffler waiting time density is effective in depicting the general ultraslow random motion.

Recurrent Neural Network for Computing the Drazin Inverse.

PubMed

Stanimirović, Predrag S; Zivković, Ivan S; Wei, Yimin

2015-11-01

This paper presents a recurrent neural network (RNN) for computing the Drazin inverse of a real matrix in real time. This recurrent neural network (RNN) is composed of n independent parts (subnetworks), where n is the order of the input matrix. These subnetworks can operate concurrently, so parallel and distributed processing can be achieved. In this way, the computational advantages over the existing sequential algorithms can be attained in real-time applications. The RNN defined in this paper is convenient for an implementation in an electronic circuit. The number of neurons in the neural network is the same as the number of elements in the output matrix, which represents the Drazin inverse. The difference between the proposed RNN and the existing ones for the Drazin inverse computation lies in their network architecture and dynamics. The conditions that ensure the stability of the defined RNN as well as its convergence toward the Drazin inverse are considered. In addition, illustrative examples and examples of application to the practical engineering problems are discussed to show the efficacy of the proposed neural network.

The impact of inversion and mirror reflection symmetry on Raman scattering of T'transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Yan, Jun; Chen, Shao-Yu; Naylor, Carl; Goldstein, Thomas; Johnson, Charlie; Venkataraman, Dhandapani; Ramasubramaniam, Ashwin

Distorted octahedral (T') transition metal dichalcogenides (TMDCs) are topologically interesting material systems. Inversion-symmetry-broken bulk T'-TMDCs are predicted to be type II Weyl semimetals and inversion-symmetric monolayer (1L) T'-TMDCs are shown to be 2D topological insulators. In this talk, I will show that both the inversion symmetry and the mirror symmetry are important for understanding the lattice dynamics and Raman scattering of T'-TMDCs. The mirror plane that is perpendicular to the zigzag transition metal atomic chain classifies lattice vibrations into z-modes and m-modes where ` z' stands for zigzag and ` m' stands for mirror. Raman active z- and m- modes can be experimentally determined with light-polarization and crystal angle-resolved Raman tensor analysis. We report observation of all 9 even-parity zone-center phonons in 1L-T'-MoTe2. In bulk T'-MoTe2, we monitor inversion symmetry breaking with the shear lattice vibrations, which is important for supporting Weyl fermions. This work is supported by the Armstrong Fund for Science and NSF EFRI 2DARE EFMA-1542879.

Chromospheric Inversions of a Micro-flaring Region

NASA Astrophysics Data System (ADS)

Reid, A.; Henriques, V.; Mathioudakis, M.; Doyle, J. G.; Ray, T.

2017-08-01

We use spectropolarimetric observations of the Ca II 8542 Å line, taken from the Swedish 1 m Solar Telescope, in an attempt to recover dynamic activity in a micro-flaring region near a sunspot via inversions. These inversions show localized mean temperature enhancements of ˜1000 K in the chromosphere and upper photosphere, along with co-spatial bi-directional Doppler shifting of 5-10 km s-1. This heating also extends along a nearby chromospheric fibril, which is co-spatial to 10-15 km s-1 downflows. Strong magnetic flux cancellation is also apparent in one of the footpoints, and is concentrated in the chromosphere. This event more closely resembles that of an Ellerman Bomb, though placed slightly higher in the atmosphere than what is typically observed.

Simulation gravity modeling to spacecraft-tracking data - Analysis and application

NASA Technical Reports Server (NTRS)

Phillips, R. J.; Sjogren, W. L.; Abbott, E. A.; Zisk, S. H.

1978-01-01

It is proposed that line-of-sight gravity measurements derived from spacecraft-tracking data can be used for quantitative subsurface density modeling by suitable orbit simulation procedures. Such an approach avoids complex dynamic reductions and is analogous to the modeling of conventional surface gravity data. This procedure utilizes the vector calculations of a given gravity model in a simplified trajectory integration program that simulates the line-of-sight gravity. Solutions from an orbit simulation inversion and a dynamic inversion on Doppler observables compare well (within 1% in mass and size), and the error sources in the simulation approximation are shown to be quite small. An application of this technique is made to lunar crater gravity anomalies by simulating the complete Bouguer correction to several large young lunar craters. It is shown that the craters all have negative Bouguer anomalies.

Experimental evaluation of model predictive control and inverse dynamics control for spacecraft proximity and docking maneuvers

NASA Astrophysics Data System (ADS)

Virgili-Llop, Josep; Zagaris, Costantinos; Park, Hyeongjun; Zappulla, Richard; Romano, Marcello

2018-03-01

An experimental campaign has been conducted to evaluate the performance of two different guidance and control algorithms on a multi-constrained docking maneuver. The evaluated algorithms are model predictive control (MPC) and inverse dynamics in the virtual domain (IDVD). A linear-quadratic approach with a quadratic programming solver is used for the MPC approach. A nonconvex optimization problem results from the IDVD approach, and a nonlinear programming solver is used. The docking scenario is constrained by the presence of a keep-out zone, an entry cone, and by the chaser's maximum actuation level. The performance metrics for the experiments and numerical simulations include the required control effort and time to dock. The experiments have been conducted in a ground-based air-bearing test bed, using spacecraft simulators that float over a granite table.

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.

Recursive inverse kinematics for robot arms via Kalman filtering and Bryson-Frazier smoothing

NASA Technical Reports Server (NTRS)

Rodriguez, G.; Scheid, R. E., Jr.

1987-01-01

This paper applies linear filtering and smoothing theory to solve recursively the inverse kinematics problem for serial multilink manipulators. This problem is to find a set of joint angles that achieve a prescribed tip position and/or orientation. A widely applicable numerical search solution is presented. The approach finds the minimum of a generalized distance between the desired and the actual manipulator tip position and/or orientation. Both a first-order steepest-descent gradient search and a second-order Newton-Raphson search are developed. The optimal relaxation factor required for the steepest descent method is computed recursively using an outward/inward procedure similar to those used typically for recursive inverse dynamics calculations. The second-order search requires evaluation of a gradient and an approximate Hessian. A Gauss-Markov approach is used to approximate the Hessian matrix in terms of products of first-order derivatives. This matrix is inverted recursively using a two-stage process of inward Kalman filtering followed by outward smoothing. This two-stage process is analogous to that recently developed by the author to solve by means of spatial filtering and smoothing the forward dynamics problem for serial manipulators.

Coffee and Tea Consumption Are Inversely Associated with Mortality in a Multiethnic Urban Population123

PubMed Central

Gardener, Hannah; Rundek, Tatjana; Wright, Clinton B.; Elkind, Mitchell S. V.; Sacco, Ralph L.

2013-01-01

Coffee and tea are commonly consumed beverages. Inverse associations with mortality have been suggested for coffee and tea, but the relationships with cause-specific mortality are not well understood. We examined regular and decaffeinated coffee and tea in relation to mortality due to all causes, vascular, nonvascular, and cancer in the multi-ethnic, prospective, population-based Northern Manhattan Study. The study population included 2461 participants with diet data who were free of stroke, myocardial infarction, and cancer at baseline (mean age 68.30 ± 10.23 y, 36% men, 19% white, 23% black, 56% Hispanic). During a mean follow-up of 11 y, we examined the associations between coffee and tea consumption, assessed by food frequency questionnaire, and 863 deaths (342 vascular related and 444 nonvascular including 160 cancer deaths) using multivariable-adjusted Cox models. Coffee consumption was inversely associated with all-cause mortality [for each additional cup/d, HR = 0.93 (95% CI: 0.88, 0.99); P = 0.02]. Caffeinated coffee was inversely associated with all-cause mortality, driven by a strong protection among those who drank ≥4 cups/d. An inverse dose-response relationship between tea and all-cause mortality was suggested [for each additional cup/d, HR = 0.91 (95% CI: 0.84, 0.99); P = 0.01]. Coffee consumption ≥4/d was protective against nonvascular death [vs. <1/mo, HR = 0.57 (95% CI: 0.33, 0.97)] and tea consumption ≥2/d was protective against nonvascular death [HR = 0.63 (95% CI: 0.41, 0.95)] and cancer [HR = 0.33 (95% CI: 0.14, 0.80)]. There was a strong inverse association between coffee and vascular-related mortality among Hispanics only. Further study is needed, including investigation into the mechanisms and compounds in coffee and tea responsible for the inverse associations with mortality. The differential relationship between coffee and vascular death across race/ethnicity underscores the need for research in similar multi-ethnic cohorts including Hispanics. PMID:23784068

Genomic evidence for role of inversion 3RP of Drosophila melanogaster in facilitating climate change adaptation.

PubMed

Rane, Rahul V; Rako, Lea; Kapun, Martin; Lee, Siu F; Hoffmann, Ary A

2015-05-01

Chromosomal inversion polymorphisms are common in animals and plants, and recent models suggest that alternative arrangements spread by capturing different combinations of alleles acting additively or epistatically to favour local adaptation. It is also thought that inversions typically maintain favoured combinations for a long time by suppressing recombination between alternative chromosomal arrangements. Here, we consider patterns of linkage disequilibrium and genetic divergence in an old inversion polymorphism in Drosophila melanogaster (In(3R)Payne) known to be associated with climate change adaptation and a recent invasion event into Australia. We extracted, karyotyped and sequenced whole chromosomes from two Australian populations, so that changes in the arrangement of the alleles between geographically separated tropical and temperate areas could be compared. Chromosome-wide linkage disequilibrium (LD) analysis revealed strong LD within the region spanned by In(3R)Payne. This genomic region also showed strong differentiation between the tropical and the temperate populations, but no differentiation between different karyotypes from the same population, after controlling for chromosomal arrangement. Patterns of differentiation across the chromosome arm and in gene ontologies were enhanced by the presence of the inversion. These data support the notion that inversions are strongly selected by bringing together combinations of genes, but it is still not clear if such combinations act additively or epistatically. Our data suggest that climatic adaptation through inversions can be dynamic, reflecting changes in the relative abundance of different forms of an inversion and ongoing evolution of allelic content within an inversion. © 2015 John Wiley & Sons Ltd.

An Inverse Neural Controller Based on the Applicability Domain of RBF Network Models

PubMed Central

Alexandridis, Alex; Stogiannos, Marios; Papaioannou, Nikolaos; Zois, Elias; Sarimveis, Haralambos

2018-01-01

This paper presents a novel methodology of generic nature for controlling nonlinear systems, using inverse radial basis function neural network models, which may combine diverse data originating from various sources. The algorithm starts by applying the particle swarm optimization-based non-symmetric variant of the fuzzy means (PSO-NSFM) algorithm so that an approximation of the inverse system dynamics is obtained. PSO-NSFM offers models of high accuracy combined with small network structures. Next, the applicability domain concept is suitably tailored and embedded into the proposed control structure in order to ensure that extrapolation is avoided in the controller predictions. Finally, an error correction term, estimating the error produced by the unmodeled dynamics and/or unmeasured external disturbances, is included to the control scheme to increase robustness. The resulting controller guarantees bounded input-bounded state (BIBS) stability for the closed loop system when the open loop system is BIBS stable. The proposed methodology is evaluated on two different control problems, namely, the control of an experimental armature-controlled direct current (DC) motor and the stabilization of a highly nonlinear simulated inverted pendulum. For each one of these problems, appropriate case studies are tested, in which a conventional neural controller employing inverse models and a PID controller are also applied. The results reveal the ability of the proposed control scheme to handle and manipulate diverse data through a data fusion approach and illustrate the superiority of the method in terms of faster and less oscillatory responses. PMID:29361781

Crustal Dynamics Project data analysis, 1990

NASA Technical Reports Server (NTRS)

Caprette, D. S.; Ma, C.; Ryan, J. W.

1990-01-01

The Goddard Very Long Baseline Interferometry (VLBI) group reports the results of analyzing 1073 Mark 3 data sets acquired from fixed and mobile observing sites through the end of 1989 and available to the Crustal Dynamics Project. Two large solutions, GLB656 and GLB657, were used to establish a VLBI reference frame with an origin coincident with the ITRF89. Another large solution, GLB658, was used to obtain Earth rotation parameters, nutation offsets, and global source positions. Site velocities were obtained from another large solution, GLB659. A fifth large solution, GLB660, was used to obtain baseline evolution. Site positions are tabulated on a yearly basis from 1979 through 1992. Site velocities are presented in both Cartesian and topocentric coordinates. The results include 76 sources, 80 sites, and 422 baselines.

Inverse modeling methods for indoor airborne pollutant tracking: literature review and fundamentals.

PubMed

Liu, X; Zhai, Z

2007-12-01

Reduction in indoor environment quality calls for effective control and improvement measures. Accurate and prompt identification of contaminant sources ensures that they can be quickly removed and contaminated spaces isolated and cleaned. This paper discusses the use of inverse modeling to identify potential indoor pollutant sources with limited pollutant sensor data. The study reviews various inverse modeling methods for advection-dispersion problems and summarizes the methods into three major categories: forward, backward, and probability inverse modeling methods. The adjoint probability inverse modeling method is indicated as an appropriate model for indoor air pollutant tracking because it can quickly find source location, strength and release time without prior information. The paper introduces the principles of the adjoint probability method and establishes the corresponding adjoint equations for both multi-zone airflow models and computational fluid dynamics (CFD) models. The study proposes a two-stage inverse modeling approach integrating both multi-zone and CFD models, which can provide a rapid estimate of indoor pollution status and history for a whole building. Preliminary case study results indicate that the adjoint probability method is feasible for indoor pollutant inverse modeling. The proposed method can help identify contaminant source characteristics (location and release time) with limited sensor outputs. This will ensure an effective and prompt execution of building management strategies and thus achieve a healthy and safe indoor environment. The method can also help design optimal sensor networks.

The Shock and Vibration Bulletin. Part 2. Structural Analysis, Design Techniques

DTIC Science & Technology

1973-06-01

FLOATING SHOCK PLATFORM SUBJECTED TO UNDERWATER EXPLOSIONS R. P. Brooks, and B. C, McNalght Naval Air Engineering Center Philadelphia, Pa, A lumped...Lohwasser, Air Force Flight Dynamics Laboratory, Wright -Patterson APB, Ohio AN ALGORITHM FOR SEMI-INVERSE ANALYSIS OF NONLINEAR DYNAMIC SYSTEMS ... 65 R...MATHEMATICAL MODEL OF A TYPICAL.FOATING SHOCK PLATFORM SSUBJECTED TO-UNDERWATE- EXPLOSIONS .......... ...................... 143 R. P. Brooks and B. C

Robust dynamic inversion controller design and analysis (using the X-38 vehicle as a case study)

NASA Astrophysics Data System (ADS)

Ito, Daigoro

A new way to approach robust Dynamic Inversion controller synthesis is addressed in this paper. A Linear Quadratic Gaussian outer-loop controller improves the robustness of a Dynamic Inversion inner-loop controller in the presence of uncertainties. Desired dynamics are given by the dynamic compensator, which shapes the loop. The selected dynamics are based on both performance and stability robustness requirements. These requirements are straightforwardly formulated as frequency-dependent singular value bounds during synthesis of the controller. Performance and robustness of the designed controller is tested using a worst case time domain quadratic index, which is a simple but effective way to measure robustness due to parameter variation. Using this approach, a lateral-directional controller for the X-38 vehicle is designed and its robustness to parameter variations and disturbances is analyzed. It is found that if full state measurements are available, the performance of the designed lateral-directional control system, measured by the chosen cost function, improves by approximately a factor of four. Also, it is found that the designed system is stable up to a parametric variation of 1.65 standard deviation with the set of uncertainty considered. The system robustness is determined to be highly sensitive to the dihedral derivative and the roll damping coefficients. The controller analysis is extended to the nonlinear system where both control input displacements and rates are bounded. In this case, the considered nonlinear system is stable up to 48.1° in bank angle and 1.59° in sideslip angle variations, indicating it is more sensitive to variations in sideslip angle than in bank angle. This nonlinear approach is further extended for the actuator failure mode analysis. The results suggest that the designed system maintains a high level of stability in the event of aileron failure. However, only 35% or less of the original stability range is maintained for the rudder failure case. Overall, this combination of controller synthesis and robustness criteria compares well with the mu-synthesis technique. It also is readily accessible to the practicing engineer, in terms of understanding and use.

Dynamic Source Inversion of a M6.5 Intraslab Earthquake in Mexico: Application of a New Parallel Genetic Algorithm

NASA Astrophysics Data System (ADS)

Díaz-Mojica, J. J.; Cruz-Atienza, V. M.; Madariaga, R.; Singh, S. K.; Iglesias, A.

2013-05-01

We introduce a novel approach for imaging the earthquakes dynamics from ground motion records based on a parallel genetic algorithm (GA). The method follows the elliptical dynamic-rupture-patch approach introduced by Di Carli et al. (2010) and has been carefully verified through different numerical tests (Díaz-Mojica et al., 2012). Apart from the five model parameters defining the patch geometry, our dynamic source description has four more parameters: the stress drop inside the nucleation and the elliptical patches; and two friction parameters, the slip weakening distance and the change of the friction coefficient. These parameters are constant within the rupture surface. The forward dynamic source problem, involved in the GA inverse method, uses a highly accurate computational solver for the problem, namely the staggered-grid split-node. The synthetic inversion presented here shows that the source model parameterization is suitable for the GA, and that short-scale source dynamic features are well resolved in spite of low-pass filtering of the data for periods comparable to the source duration. Since there is always uncertainty in the propagation medium as well as in the source location and the focal mechanisms, we have introduced a statistical approach to generate a set of solution models so that the envelope of the corresponding synthetic waveforms explains as much as possible the observed data. We applied the method to the 2012 Mw6.5 intraslab Zumpango, Mexico earthquake and determined several fundamental source parameters that are in accordance with different and completely independent estimates for Mexican and worldwide earthquakes. Our weighted-average final model satisfactorily explains eastward rupture directivity observed in the recorded data. Some parameters found for the Zumpango earthquake are: Δτ = 30.2+/-6.2 MPa, Er = 0.68+/-0.36x10^15 J, G = 1.74+/-0.44x10^15 J, η = 0.27+/-0.11, Vr/Vs = 0.52+/-0.09 and Mw = 6.64+/-0.07; for the stress drop, radiated energy, fracture energy, radiation efficiency, rupture velocity and moment magnitude, respectively. Mw6.5 intraslab Zumpango earthquake location, stations location and tectonic setting in central Mexico

Dynamics of omnidirectional unmanned rescue vehicle with mecanum wheels

NASA Astrophysics Data System (ADS)

Typiak, Andrzej; Łopatka, Marian Janusz; Rykała, Łukasz; Kijek, Magdalena

2018-01-01

The work presents the dynamic equations of motion of a unmanned six-wheeled vehicle with mecanum wheels for rescue applications derived with the of Lagrange equations of the second kind with multipliers. Analysed vehicle through using mecanum wheels has three degrees of freedom and can move on a flat ground in any direction with any configuration of platform's frame. In order to derive dynamic equations of motion of mentioned object, kinetic potential of the system and generalized forces affecting the system are determined. The results of a solution of inverse dynamics problem are also published.

Inferring HIV-1 Transmission Dynamics in Germany From Recently Transmitted Viruses.

PubMed

Pouran Yousef, Kaveh; Meixenberger, Karolin; Smith, Maureen R; Somogyi, Sybille; Gromöller, Silvana; Schmidt, Daniel; Gunsenheimer-Bartmeyer, Barbara; Hamouda, Osamah; Kücherer, Claudia; von Kleist, Max

2016-11-01

Although HIV continues to spread globally, novel intervention strategies such as treatment as prevention (TasP) may bring the epidemic to a halt. However, their effective implementation requires a profound understanding of the underlying transmission dynamics. We analyzed parameters of the German HIV epidemic based on phylogenetic clustering of viral sequences from recently infected seroconverters with known infection dates. Viral baseline and follow-up pol sequences (n = 1943) from 1159 drug-naïve individuals were selected from a nationwide long-term observational study initiated in 1997. Putative transmission clusters were computed based on a maximum likelihood phylogeny. Using individual follow-up sequences, we optimized our clustering threshold to maximize the likelihood of co-clustering individuals connected by direct transmission. The sizes of putative transmission clusters scaled inversely with their abundance and their distribution exhibited a heavy tail. Clusters based on the optimal clustering threshold were significantly more likely to contain members of the same or bordering German federal states. Interinfection times between co-clustered individuals were significantly shorter (26 weeks; interquartile range: 13-83) than in a null model. Viral intraindividual evolution may be used to select criteria that maximize co-clustering of transmission pairs in the absence of strong adaptive selection pressure. Interinfection times of co-clustered individuals may then be an indicator of the typical time to onward transmission. Our analysis suggests that onward transmission may have occurred early after infection, when individuals are typically unaware of their serological status. The latter argues that TasP should be combined with HIV testing campaigns to reduce the possibility of transmission before TasP initiation.

Nonlinear Inversion for Dynamic Rupture Parameters from the 2004 Mw6.0 Parkfield Earthquake

NASA Astrophysics Data System (ADS)

Jimenez, R. M.; Olsen, K. B.

2007-12-01

The Parkfield section of the San Andreas Fault has produced repeated moderate-size earthquakes at fairly regular intervals and is therefore an important target for investigations of rupture initiation, propagation and arrest, which could eventually lead to clues on earthquake prediction. The most recent member of the Parkfield series of earthquakes, the 2004 Mw6.0 event, produced a considerable amount of high-resolution strong motion data, and provides an ideal test bed for analysis of the dynamic rupture propagation. Here, we use a systematic nonlinear direct-search method to invert strong-ground motion data (less than 1 Hz) at 37 stations to obtain models of the slip weakening distance and spatially-varying stress drop (8 by 4 subfaults) on the (vertical) causative segment of the San Andreas fault (40 km long by 15 km wide), along with spatial-temporal coseismic slip distributions. The rupture and wave propagation modeling is performed by a three-dimensional finite-difference method with a slip- weakening friction law and the stress-glut dynamic-rupture formulation (Andrews, 1999), and the inversion is carried out by a neighborhood algorithm (Sambridge, 1999), minimizing the least-squares misfit between the calculated and observed seismograms. The dynamic rupture is nucleated artificially by lowering the yield stress in a 3 km by 3 km patch centered at the location of the hypocenter estimated from strong motion data. Outside the nucleation patch the yield stress is kept constant (5-10 MPa), and we constrain the slip-weakening distance to values less than 1 m. We compare the inversion results for two different velocity models: (1) a 3-D model based on the P-wave velocity structure by Thurber (2006), with S-wave and density relations based on Brocher (2005), and (2) a combination of two different 1-D layered velocity structures on either side of the fault, as proposed by Liu et al. (2006). Due to the non-uniqueness of the problem, the inversion provides an ensemble of equally valid rupture models that produce synthetics with comparable fit to the observed strong motion data. Our preliminary results with the smallest misfits, out of about 3000 tested rupture models, suggest an average slip-weakening distance of 19-81 cm and an average stress drop across the fault of 6.7 - 8.4 MPa. Compared to the kinematic inversion results by Liu et al. (2006) our models with the smallest misfits produce a larger maximum slip (up to about 81 cm) and smaller rupture area, but similar rupture duration (5-7s). The inversions carried out for the layered models tend to produce smaller misfit between data and synthetics as compared to the results using the 3D structure. This suggests that our 3D structure needs improvement, including the Vs-Vp and density-Vp relation. We expect further decrease in the misfit values by increasing the number of tested rupture models.

Symmetry realization via a dynamical inverse Higgs mechanism

NASA Astrophysics Data System (ADS)

Rothstein, Ira Z.; Shrivastava, Prashant

2018-05-01

The Ward identities associated with spontaneously broken symmetries can be saturated by Goldstone bosons. However, when space-time symmetries are broken, the number of Goldstone bosons necessary to non-linearly realize the symmetry can be less than the number of broken generators. The loss of Goldstones may be due to a redundancy or the generation of a gap. In either case the associated Goldstone may be removed from the spectrum. This phenomena is called an Inverse Higgs Mechanism (IHM) and its appearance has a well defined mathematical condition. However, there are cases when a Goldstone boson associated with a broken generator does not appear in the low energy theory despite the lack of the existence of an associated IHM. In this paper we will show that in such cases the relevant broken symmetry can be realized, without the aid of an associated Goldstone, if there exists a proper set of operator constraints, which we call a Dynamical Inverse Higgs Mechanism (DIHM). We consider the spontaneous breaking of boosts, rotations and conformal transformations in the context of Fermi liquids, finding three possible paths to symmetry realization: pure Goldstones, no Goldstones and DIHM, or some mixture thereof. We show that in the two dimensional degenerate electron system the DIHM route is the only consistent way to realize spontaneously broken boosts and dilatations, while in three dimensions these symmetries could just as well be realized via the inclusion of non-derivatively coupled Goldstone bosons. We present the action, including the leading order non-linearities, for the rotational Goldstone (angulon), and discuss the constraint associated with the possible DIHM that would need to be imposed to remove it from the spectrum. Finally we discuss the conditions under which Goldstone bosons are non-derivatively coupled, a necessary condition for the existence of a Dynamical Inverse Higgs Constraint (DIHC), generalizing the results for Vishwanath and Wantanabe.

Baseline biopsychosocial determinants of telomere length and 6-year attrition rate.

PubMed

Révész, Dóra; Milaneschi, Yuri; Terpstra, Erik M; Penninx, Brenda W J H

2016-05-01

Short leukocyte telomere length (TL) and accelerated telomere attrition have been associated with various deleterious health outcomes, although their determinants have not been explored collectively in a large-scale study. Leukocyte TL was measured (baseline N=2936; 6-year follow-up N=1860) in participants (18-65 years) from the NESDA study. Baseline determinants of TL included sociodemographics, lifestyle, chronic diseases, psychosocial stressors, and metabolic and physiological stress markers. Multivariate linear regression models were used to examine the associations between these determinants and (1) baseline TL, and (2) 6-year TL change. Multinomial logistic regression analyses were used to examine the predictors of telomere attrition and lengthening, as compared to stable TL. Short baseline TL was associated with older age, male sex, non-European ethnicity, cigarette smoking, recent life events, and higher triglycerides, glucose and pre-ejection period (R(2)=11.3%). The 6-year telomere attrition was inversely associated with baseline TL (R(2)=51.6%); also older age, long sleep, not having a partner, high childhood trauma index, and gastrointestinal disease were associated with 6-year TL attrition (additional R(2)=3.7%). Telomere attrition seemed to have slightly more predictors than lengthening. Sociodemographic, lifestyle, psychosocial stress and metabolic and physiological stress factors are cross-sectionally linked with TL. Telomere attrition over six years was strongly associated with baseline TL, suggesting an internal homeostatic influence. Modulation of the identified determinants may become target of future studies to promote telomere maintenance and healthy aging. Copyright © 2016 Elsevier Ltd. All rights reserved.

Pathway concepts experiment for head-down synthetic vision displays

NASA Astrophysics Data System (ADS)

Prinzel, Lawrence J., III; Arthur, Jarvis J., III; Kramer, Lynda J.; Bailey, Randall E.

2004-08-01

Eight 757 commercial airline captains flew 22 approaches using the Reno Sparks 16R Visual Arrival under simulated Category I conditions. Approaches were flown using a head-down synthetic vision display to evaluate four tunnel ("minimal", "box", "dynamic pathway", "dynamic crow's feet") and three guidance ("ball", "tadpole", "follow-me aircraft") concepts and compare their efficacy to a baseline condition (i.e., no tunnel, ball guidance). The results showed that the tunnel concepts significantly improved pilot performance and situation awareness and lowered workload compared to the baseline condition. The dynamic crow's feet tunnel and follow-me aircraft guidance concepts were found to be the best candidates for future synthetic vision head-down displays. These results are discussed with implications for synthetic vision display design and future research.

Subsonic static and dynamic stability characteristics of the test technique demonstrator NASP configuration

NASA Technical Reports Server (NTRS)

Boyden, Richmond P.; Dress, David A.; Fox, Charles H., Jr.; Huffman, Jarrett K.; Cruz, Christopher I.

1993-01-01

The paper describes the procedure used for and the results obtained of wind-tunnel tests of the National Aerospace Plane (NASP) configuration, which were conducted in the NASA Langley Research Center High Speed Tunnel using a blended body NASP configuration designed by the research center. Static and dynamic stability characteristics were measured at Mach numbers 0.3, 0.6, and 0.8. In addition to tests of the baseline configuration, component buildup tests with a canard surface and with a body flap were carried out. Results demonstrated a positive static stability of the baseline configuration, except at the higher angles of attack at Mach 0.8. A good agreement was found between the inphase dynamic parameters and the corresponding static data.

Nutritional Factors and Preservation of C-Peptide in Youth With Recently Diagnosed Type 1 Diabetes

PubMed Central

Mayer-Davis, Elizabeth J.; Dabelea, Dana; Crandell, Jamie L.; Crume, Tessa; D’Agostino, Ralph B.; Dolan, Lawrence; King, Irena B.; Lawrence, Jean M.; Norris, Jill M.; Pihoker, Catherine; The, Natalie

2013-01-01

OBJECTIVE To test the novel hypothesis that nutritional factors previously associated with type 1 diabetes etiology or with insulin secretion are prospectively associated with fasting C-peptide (FCP) concentration among youth recently diagnosed with type 1 diabetes. RESEARCH DESIGN AND METHODS Included were 1,316 youth with autoantibody-positive type 1 diabetes who participated in the SEARCH for Diabetes in Youth study (baseline disease duration, 9.9 months; SD, 6.3). Nutritional exposures included breastfeeding and age at introduction of complementary foods, baseline plasma long-chain omega-3 fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), vitamin D, vitamin E, and, from a baseline food frequency questionnaire, estimated intake of the branched-chain amino acid leucine and total carbohydrate. Multiple linear regression models were conducted to relate each nutritional factor to baseline FCP adjusted for demographics, disease-related factors, and other confounders. Prospective analyses included the subset of participants with preserved β-cell function at baseline (baseline FCP ≥0.23 ng/mL) with additional adjustment for baseline FCP and time (mean follow-up, 24.3 months; SD, 8.2; n = 656). FCP concentration was analyzed as log(FCP). RESULTS In adjusted prospective analyses, baseline EPA (P = 0.02), EPA plus DHA (P = 0.03), and leucine (P = 0.03) were each associated positively and significantly with FCP at follow-up. Vitamin D was unexpectedly inversely associated with FCP (P = 0.002). CONCLUSIONS Increased intake of branched-chain amino acids and long-chain omega-3 fatty acids may support preservation of β-cell function. This represents a new direction for research to improve prognosis for type 1 diabetes. PMID:23801797

Nutritional factors and preservation of C-peptide in youth with recently diagnosed type 1 diabetes: SEARCH Nutrition Ancillary Study.

PubMed

Mayer-Davis, Elizabeth J; Dabelea, Dana; Crandell, Jamie L; Crume, Tessa; D'Agostino, Ralph B; Dolan, Lawrence; King, Irena B; Lawrence, Jean M; Norris, Jill M; Pihoker, Catherine; The, Natalie

2013-07-01

To test the novel hypothesis that nutritional factors previously associated with type 1 diabetes etiology or with insulin secretion are prospectively associated with fasting C-peptide (FCP) concentration among youth recently diagnosed with type 1 diabetes. Included were 1,316 youth with autoantibody-positive type 1 diabetes who participated in the SEARCH for Diabetes in Youth study (baseline disease duration, 9.9 months; SD, 6.3). Nutritional exposures included breastfeeding and age at introduction of complementary foods, baseline plasma long-chain omega-3 fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), vitamin D, vitamin E, and, from a baseline food frequency questionnaire, estimated intake of the branched-chain amino acid leucine and total carbohydrate. Multiple linear regression models were conducted to relate each nutritional factor to baseline FCP adjusted for demographics, disease-related factors, and other confounders. Prospective analyses included the subset of participants with preserved β-cell function at baseline (baseline FCP ≥0.23 ng/mL) with additional adjustment for baseline FCP and time (mean follow-up, 24.3 months; SD, 8.2; n = 656). FCP concentration was analyzed as log(FCP). In adjusted prospective analyses, baseline EPA (P = 0.02), EPA plus DHA (P = 0.03), and leucine (P = 0.03) were each associated positively and significantly with FCP at follow-up. Vitamin D was unexpectedly inversely associated with FCP (P = 0.002). Increased intake of branched-chain amino acids and long-chain omega-3 fatty acids may support preservation of β-cell function. This represents a new direction for research to improve prognosis for type 1 diabetes.

Investigation of Dynamic Properties of Water-Saturated Sand by the Results of the Inverse Experiment Technique

NASA Astrophysics Data System (ADS)

Bragov, A. M.; Balandin, Vl. V.; Kotov, V. L.; Balandin, Vl. Vl.

2018-04-01

We present new experimental results on the investigation of the dynamic properties of sand soil on the basis of the inverse experiment technique using a measuring rod with a flat front-end face. A limited applicability has been shown of the method using the procedure for correcting the shape of the deformation pulse due to dispersion during its propagation in the measuring rod. Estimates of the pulse maximum have been obtained and the results of comparison of numerical calculations with experimental data are given. The sufficient accuracy in determining the drag force during the quasi-stationary stage of penetration has been established. The parameters of dynamic compressibility and resistance to shear of water-saturated sand have been determined in the course of the experimental-theoretical analysis of the maximum values of the drag force and its values at the quasi-stationary stage of penetration. It has been shown that with almost complete water saturation of sand its shear properties are reduced but remain significant in the practically important range of penetration rates.

Analysis and numerical modelling of eddy current damper for vibration problems

NASA Astrophysics Data System (ADS)

Irazu, L.; Elejabarrieta, M. J.

2018-07-01

This work discusses a contactless eddy current damper, which is used to attenuate structural vibration. Eddy currents can remove energy from dynamic systems without any contact and, thus, without adding mass or modifying the rigidity of the structure. An experimental modal analysis of a cantilever beam in the absence of and under a partial magnetic field is conducted in the bandwidth of 01 kHz. The results show that the eddy current phenomenon can attenuate the vibration of the entire structure without modifying the natural frequencies or the mode shapes of the structure itself. In this study, a new inverse method to numerically determine the dynamic properties of the contactless eddy current damper is proposed. The proposed inverse method and the eddy current model based on a lineal viscous force are validated by a practical application. The numerically obtained transfer function correlates with the experimental one, thus showing good agreement in the entire bandwidth of 01 kHz. The proposed method provides an easy and quick tool to model and predict the dynamic behaviour of the contactless eddy current damper, thereby avoiding the use of complex analytical models.

Dynamic Behaviour of Tetramethylethylene Diamine (TMEDA) Ligands in Solid Organolithium Compounds: A Variable Temperature 13C and I5N CP/MAS NMR Study

NASA Astrophysics Data System (ADS)

Baumann, Wolfgang; Oprunenko, Yuri; Günther, Harald

1995-05-01

The dynamic behaviour of tetramethylethylene diamine (TMEDA) ligands in three organometallic complexes, dimeric phenyllithium, [Li(tmeda)μ-Ph]2 (1), lithium cyclopentadienide, [Li(tmeda)]C5H5 (2), and dilithium naphthalendiide, trans-[Li(tmeda)]2C10H8 (3), has been studied by CP/MAS 13C and 15N as well as 7Li MAS NMR spectroscopy of powdered samples. Two dynamic processes with free activation enthalpies of 40 and 68 kJ mol-1, respectively, were detected for 1. The first one can be assigned to ring inversion of the five-membered Li-TMEDA rings, while the second is caused by a complete rotation of the TMEDA ligands or a ring inversion of the central four-membered C-Li-C-Li metallacycle. Fast rotation of the ligands on the NMR time scale was found for 2, while 3 shows 180° ring flips of the Li-TMEDA groups, which are characterized by an energy barrier ΔG" (317) of 64 kJ mol-1

Dynamics and control of a multimode laser: Reduction of space-dependent rate equations to a low-dimensional system.

PubMed

Pyragas, K; Lange, F; Letz, T; Parisi, J; Kittel, A

2001-01-01

We suggest a quantitatively correct procedure for reducing the spatial degrees of freedom of the space-dependent rate equations of a multimode laser that describe the dynamics of the population inversion of the active medium and the mode intensities of the standing waves in the laser cavity. The key idea of that reduction is to take advantage of the small value of the parameter that defines the ratio between the population inversion decay rate and the cavity decay rate. We generalize the reduction procedure for the case of an intracavity frequency doubled laser. Frequency conversion performed by an optically nonlinear crystal placed inside the laser cavity may cause a pronounced instability in the laser performance, leading to chaotic oscillations of the output intensity. Based on the reduced equations, we analyze the dynamical properties of the system as well as the problem of stabilizing the steady state. The numerical analysis is performed considering the specific system of a Nd:YAG (neodymium-doped yttrium aluminum garnet) laser with an intracavity KTP (potassium titanyl phosphate) crystal.

Study of a Simulation Tool to Determine Achievable Control Dynamics and Control Power Requirements with Perfect Tracking

NASA Technical Reports Server (NTRS)

Ostroff, Aaron J.

1998-01-01

This paper contains a study of two methods for use in a generic nonlinear simulation tool that could be used to determine achievable control dynamics and control power requirements while performing perfect tracking maneuvers over the entire flight envelope. The two methods are NDI (nonlinear dynamic inversion) and the SOFFT(Stochastic Optimal Feedforward and Feedback Technology) feedforward control structure. Equivalent discrete and continuous SOFFT feedforward controllers have been developed. These equivalent forms clearly show that the closed-loop plant model loop is a plant inversion and is the same as the NDI formulation. The main difference is that the NDI formulation has a closed-loop controller structure whereas SOFFT uses an open-loop command model. Continuous, discrete, and hybrid controller structures have been developed and integrated into the formulation. Linear simulation results show that seven different configurations all give essentially the same response, with the NDI hybrid being slightly different. The SOFFT controller gave better tracking performance compared to the NDI controller when a nonlinear saturation element was added. Future plans include evaluation using a nonlinear simulation.

Baseline psychophysiological and cortisol reactivity as a predictor of PTSD treatment outcome in virtual reality exposure therapy

PubMed Central

Norrholm, Seth Davin; Jovanovic, Tanja; Gerardi, Maryrose; Breazeale, Kathryn G.; Price, Matthew; Davis, Michael; Duncan, Erica; Ressler, Kerry J.; Bradley, Bekh; Rizzo, Albert; Tuerk, Peter W.; Rothbaum, Barbara O.

2017-01-01

Baseline cue-dependent physiological reactivity may serve as an objective measure of posttraumatic stress disorder (PTSD) symptoms. Additionally, prior animal model and psychological studies would suggest that subjects with greatest symptoms at baseline may have the greatest violation of expectancy to danger when undergoing exposure based psychotherapy; thus treatment approaches which enhanced the learning under these conditions would be optimal for those with maximal baseline cue-dependent reactivity. However methods to study this hypothesis objectively are lacking. Virtual reality (VR) methodologies have been successfully employed as an enhanced form of imaginal prolonged exposure therapy for the treatment of PTSD. Our goal was to examine the predictive nature of initial psychophysiological (e.g., startle, skin conductance, heart rate) and stress hormone responses (e.g., cortisol) during presentation of VR-based combat-related stimuli on PTSD treatment outcome. Combat veterans with PTSD underwent 6 weeks of VR exposure therapy combined with either D-cycloserine (DCS), alprazolam (ALP), or placebo (PBO). In the DCS group, startle response to VR scenes prior to initiation of treatment accounted for 76% of the variance in CAPS change scores, p < 0.001, in that higher responses predicted greater changes in symptom severity over time. Additionally, baseline cortisol reactivity was inversely associated with treatment response in the ALP group, p = 0.04. We propose that baseline cue-activated physiological measures will be sensitive to predicting patients’ level of response to exposure therapy, in particular in the presence of enhancement (e.g., DCS). PMID:27183343

Dynamic characterization of high damping viscoelastic materials from vibration test data

NASA Astrophysics Data System (ADS)

Martinez-Agirre, Manex; Elejabarrieta, María Jesús

2011-08-01

The numerical analysis and design of structural systems involving viscoelastic damping materials require knowledge of material properties and proper mathematical models. A new inverse method for the dynamic characterization of high damping and strong frequency-dependent viscoelastic materials from vibration test data measured by forced vibration tests with resonance is presented. Classical material parameter extraction methods are reviewed; their accuracy for characterizing high damping materials is discussed; and the bases of the new analysis method are detailed. The proposed inverse method minimizes the residue between the experimental and theoretical dynamic response at certain discrete frequencies selected by the user in order to identify the parameters of the material constitutive model. Thus, the material properties are identified in the whole bandwidth under study and not just at resonances. Moreover, the use of control frequencies makes the method insensitive to experimental noise and the efficiency is notably enhanced. Therefore, the number of tests required is drastically reduced and the overall process is carried out faster and more accurately. The effectiveness of the proposed method is demonstrated with the characterization of a CLD (constrained layer damping) cantilever beam. First, the elastic properties of the constraining layers are identified from the dynamic response of a metallic cantilever beam. Then, the viscoelastic properties of the core, represented by a four-parameter fractional derivative model, are identified from the dynamic response of a CLD cantilever beam.

Earthquake Rupture Process Inferred from Joint Inversion of 1-Hz GPS and Strong Motion Data: The 2008 Iwate-Miyagi Nairiku, Japan, Earthquake

NASA Astrophysics Data System (ADS)

Yokota, Y.; Koketsu, K.; Hikima, K.; Miyazaki, S.

2009-12-01

1-Hz GPS data can be used as a ground displacement seismogram. The capability of high-rate GPS to record seismic wave fields for large magnitude (M8 class) earthquakes has been demonstrated [Larson et al., 2003]. Rupture models were inferred solely and supplementarily from 1-Hz GPS data [Miyazaki et al., 2004; Ji et al., 2004; Kobayashi et al., 2006]. However, none of the previous studies have succeeded in inferring the source process of the medium-sized (M6 class) earthquake solely from 1-Hz GPS data. We first compared 1-Hz GPS data with integrated strong motion waveforms for the 2008 Iwate-Miyagi Nairiku, Japan, earthquake. We performed a waveform inversion for the rupture process using 1-Hz GPS data only [Yokota et al., 2009]. We here discuss the rupture processes inferred from the inversion of 1-Hz GPS data of GEONET only, the inversion of strong motion data of K-NET and KiK-net only, and the joint inversion of 1-Hz GPS and strong motion data. The data were inverted to infer the rupture process of the earthquake using the inversion codes by Yoshida et al. [1996] with the revisions by Hikima and Koketsu [2005]. In the 1-Hz GPS inversion result, the total seismic moment is 2.7×1019 Nm (Mw: 6.9) and the maximum slip is 5.1 m. These results are approximately equal to 2.4×1019 Nm and 4.5 m from the inversion of strong motion data. The difference in the slip distribution on the northern fault segment may come from long-period motions possibly recorded only in 1-Hz GPS data. In the joint inversion result, the total seismic moment is 2.5×1019 Nm and the maximum slip is 5.4 m. These values also agree well with the result of 1-Hz GPS inversion. In all the series of snapshots that show the dynamic features of the rupture process, the rupture propagated bilaterally from the hypocenter to the south and north. The northern rupture speed is faster than the northern one. These agreements demonstrate the ability of 1-Hz GPS data to infer not only static, but also dynamic features of a medium-sized (M6 class) earthquake, although some details, such as the shallow extension of the southern asperity, are missing, due possibly to their limitations such as the sampling interval of 1 s and the sparse GPS stations distiribution in the near field of the earthquake. The result of the joint inversion indiates that these minor discrepancies can be reduced by the introduction of strong motion data. Continuous GPS monitoring at a much higher rate (e.g., 10 Hz) will also be helpful for reducing the minor discrepancies.

Dynamic Bus Travel Time Prediction Models on Road with Multiple Bus Routes

PubMed Central

Bai, Cong; Peng, Zhong-Ren; Lu, Qing-Chang; Sun, Jian

2015-01-01

Accurate and real-time travel time information for buses can help passengers better plan their trips and minimize waiting times. A dynamic travel time prediction model for buses addressing the cases on road with multiple bus routes is proposed in this paper, based on support vector machines (SVMs) and Kalman filtering-based algorithm. In the proposed model, the well-trained SVM model predicts the baseline bus travel times from the historical bus trip data; the Kalman filtering-based dynamic algorithm can adjust bus travel times with the latest bus operation information and the estimated baseline travel times. The performance of the proposed dynamic model is validated with the real-world data on road with multiple bus routes in Shenzhen, China. The results show that the proposed dynamic model is feasible and applicable for bus travel time prediction and has the best prediction performance among all the five models proposed in the study in terms of prediction accuracy on road with multiple bus routes. PMID:26294903

Dynamic Bus Travel Time Prediction Models on Road with Multiple Bus Routes.

PubMed

Bai, Cong; Peng, Zhong-Ren; Lu, Qing-Chang; Sun, Jian

2015-01-01

Accurate and real-time travel time information for buses can help passengers better plan their trips and minimize waiting times. A dynamic travel time prediction model for buses addressing the cases on road with multiple bus routes is proposed in this paper, based on support vector machines (SVMs) and Kalman filtering-based algorithm. In the proposed model, the well-trained SVM model predicts the baseline bus travel times from the historical bus trip data; the Kalman filtering-based dynamic algorithm can adjust bus travel times with the latest bus operation information and the estimated baseline travel times. The performance of the proposed dynamic model is validated with the real-world data on road with multiple bus routes in Shenzhen, China. The results show that the proposed dynamic model is feasible and applicable for bus travel time prediction and has the best prediction performance among all the five models proposed in the study in terms of prediction accuracy on road with multiple bus routes.

Development of a fulcrum methodology to replicate the lateral ankle sprain mechanism and measure dynamic inversion speed.

PubMed

Knight, Adam C; Weimar, Wendi H

2012-09-01

When the ankle is forced into inversion, the speed at which this movement occurs may affect the extent of injury. The purpose of this investigation was to develop a fulcrum device to mimic the mechanism of a lateral ankle sprain and to determine the reliability and validity of the temporal variables produced by this device. Additionally, this device was used to determine if a single previous lateral ankle sprain or ankle taping effected the time to maximum inversion and/or mean inversion speed. Twenty-six participants (13 with history of a single lateral ankle sprain and 13 with no history of injury) completed the testing. The participants completed testing on three separate days, performing 10 trials with the fulcrum per leg on each testing day, and tape was applied to both ankles on one testing day. No significant interactions or main effects were found for either previous injury or ankle taping, but good reliability was found for time to maximum inversion (ICC = .81) and mean inversion speed (ICC = .79). The findings suggest that although neither variable was influenced by the history of a single previous lateral ankle sprain or ankle taping, both variables demonstrated good reliability and construct validity, but not discriminative validity.

The impact of neighborhood on physical activity in the Jackson Heart Study.

PubMed

Robinson, Jennifer C; Wyatt, Sharon B; Dubbert, Patricia M; May, Warren; Sims, Mario

2016-09-01

Physical inactivity is an independent risk factor for many diseases. Most research has focused on individual-level factors for physical activity (PA), but evidence suggests that neighborhood is also important. We examined baseline data collected between 2000 and 2004 from 5236 participants in the Jackson Heart Study to determine the effects of neighborhood on 2 types of PA: Active Living (AL), and Sports and Exercise (Sport) in an all-African American cohort. Participants were georeferenced and data from individual baseline questionnaires and US Census were analyzed using descriptive, bivariate, and multilevel models. In both types of PA, neighborhood factors had an independent and additive effect on AL and Sport. Living in an urban (p=0.003) or neighborhood with a higher percentage of residents with less than a high school education (p<0.001) was inversely associated with AL. There was an inverse interaction effect between individual and lower neighborhood education (p=0.01), as well as between age and urban neighborhoods (p=0.02) on AL. Individual level education (OR=1.30) and per capita income (OR=1.07) increased the odds of moderate-to-high sports. Future studies should focus on what contextual aspects of urban or less educated neighborhoods are influential in determining PA, as well as longitudinal multilevel analyses of neighborhood effects on PA. Copyright © 2016 Elsevier Inc. All rights reserved.

Chocolate consumption in relation to blood pressure and risk of cardiovascular disease in German adults.

PubMed

Buijsse, Brian; Weikert, Cornelia; Drogan, Dagmar; Bergmann, Manuela; Boeing, Heiner

2010-07-01

To investigate the association of chocolate consumption with measured blood pressure (BP) and the incidence of cardiovascular disease (CVD). Dietary intake, including chocolate, and BP were assessed at baseline (1994-98) in 19 357 participants (aged 35-65 years) free of myocardial infarction (MI) and stroke and not using antihypertensive medication of the Potsdam arm of the European Prospective Investigation into Cancer and Nutrition. Incident cases of MI (n = 166) and stroke (n = 136) were identified after a mean follow-up of approximately 8 years. Mean systolic BP was 1.0 mmHg [95% confidence interval (CI) -1.6 to -0.4 mmHg] and mean diastolic BP 0.9 mmHg (95% CI -1.3 to -0.5 mmHg) lower in the top quartile compared with the bottom quartile of chocolate consumption. The relative risk of the combined outcome of MI and stroke for top vs. bottom quartiles was 0.61 (95% CI 0.44-0.87; P linear trend = 0.014). Baseline BP explained 12% of this lower risk (95% CI 3-36%). The inverse association was stronger for stroke than for MI. Chocolate consumption appears to lower CVD risk, in part through reducing BP. The inverse association may be stronger for stroke than for MI. Further research is needed, in particular randomized trials.

Conditions for the formation of prominences as inferred from optical observations

NASA Technical Reports Server (NTRS)

Martin, Sara F.

1990-01-01

It is suggested that three conditions, if dynamically maintained for a sufficient period of time, will result in the formation of a solar prominence. These conditions are the presence of a coronal arcade that connects the magnetic fields on opposite sides of a prominence; the existence of a long-term (hours to days) converging flow of small patches of opposite-polarity magnetic flux toward a common-polarity inversion zone; and the cancellation of encountered patches of magnetic flux of opposite polarity at a photospheric polarity inversion boundary.

Duality and symmetry lost in solid mechanics

NASA Astrophysics Data System (ADS)

Bui, Huy Duong

2008-01-01

Some conservation laws in Solids and Fracture Mechanics present a lack of symmetry between kinematic and dynamic variables. It is shown that Duality is the right tool to re-establish the symmetry between equations and variables and to provide conservation laws of the pure divergence type which provide true path independent integrals. The loss of symmetry of some energetic expressions is exploited to derive a new method for solving some inverse problems. In particular, the earthquake inverse problem is solved analytically. To cite this article: H.D. Bui, C. R. Mecanique 336 (2008).

Structural analysis of stratocumulus convection

NASA Technical Reports Server (NTRS)

Siems, S. T.; Baker, M. B.; Bretherton, C. S.

1990-01-01

The 1 and 20 Hz data are examined from the Electra flights made on July 5, 1987. The flight legs consisted of seven horizontal turbulent legs at the inversion, midcloud, and below clouds, plus 4 soundings made within the same period. The Rosemont temperature sensor and the top and bottom dewpoint sensors were used to measure temperature and humidity at 1 Hz. Inversion structure and entrainment; local dynamics and large scale forcing; convective elements; and decoupling of cloud and subcloud are discussed in relationship to the results of the Electra flight.

Inverse energy cascades in three-dimensional turbulence

NASA Technical Reports Server (NTRS)

Hossain, Murshed

1991-01-01

Fully three-dimensional magnetohydrodynamic (MHD) turbulence at large kinetic and low magnetic Reynolds numbers is considered in the presence of a strong uniform magnetic field. It is shown by numerical simulation of a model of MHD that the energy inverse cascades to longer length scales when the interaction parameter is large. While the steady-state dynamics of the driven problem is three-dimensional in character, the behavior has resemblance to two-dimensional hydrodynamics. These results have implications in turbulence theory, MHD power generator, planetary dynamos, and fusion reactor blanket design.

Improving rotorcraft survivability to RPG attack using inverse methods

NASA Astrophysics Data System (ADS)

Anderson, D.; Thomson, D. G.

2009-09-01

This paper presents the results of a preliminary investigation of optimal threat evasion strategies for improving the survivability of rotorcraft under attack by rocket propelled grenades (RPGs). The basis of this approach is the application of inverse simulation techniques pioneered for simulation of aggressive helicopter manoeuvres to the RPG engagement problem. In this research, improvements in survivability are achieved by computing effective evasive manoeuvres. The first step in this process uses the missile approach warning system camera (MAWS) on the aircraft to provide angular information of the threat. Estimates of the RPG trajectory and impact point are then estimated. For the current flight state an appropriate evasion response is selected then realised via inverse simulation of the platform dynamics. Results are presented for several representative engagements showing the efficacy of the approach.

Phylogenetic niche conservatism explains an inverse latitudinal diversity gradient in freshwater arthropods

NASA Astrophysics Data System (ADS)

Morinière, Jérôme; van Dam, Matthew H.; Hawlitschek, Oliver; Bergsten, Johannes; Michat, Mariano C.; Hendrich, Lars; Ribera, Ignacio; Toussaint, Emmanuel F. A.; Balke, Michael

2016-05-01

The underlying mechanisms responsible for the general increase in species richness from temperate regions to the tropics remain equivocal. Many hypotheses have been proposed to explain this astonishing pattern but additional empirical studies are needed to shed light on the drivers at work. Here we reconstruct the evolutionary history of the cosmopolitan diving beetle subfamily Colymbetinae, the majority of which are found in the Northern hemisphere, hence exhibiting an inversed latitudinal diversity gradient. We reconstructed a dated phylogeny using 12 genes, to investigate the biogeographical history and diversification dynamics in the Colymbetinae. We aimed to identify the role that phylogenetic niche conservatism plays in the inversed diversification pattern seen in this group. Our results suggest that Colymbetinae originated in temperate climates, which supports the hypothesis that their distribution is the result of an ancestral adaptation to temperate environmental conditions rather than tropical origins, and that temperate niche conservatism can generate and/or maintain inverse latitudinal diversity gradients.

Analysis of Raman lasing without inversion

NASA Astrophysics Data System (ADS)

Sheldon, Paul Martin

1999-12-01

Properties of lasing without inversion were studied analytically and numerically using Maple computer assisted algebra software. Gain for probe electromagnetic field without population inversion in detuned three level atomic schemes has been found. Matter density matrix dynamics and coherence is explored using Pauli matrices in 2-level systems and Gell-Mann matrices in 3-level systems. It is shown that extreme inversion produces no coherence and hence no lasing. Unitary transformation from the strict field-matter Hamiltonian to an effective two-photon Raman Hamiltonian for multilevel systems has been derived. Feynman diagrams inherent in the derivation show interesting physics. An additional picture change was achieved and showed cw gain possible. Properties of a Raman-like laser based on injection of 3- level coherently driven Λ-type atoms whose Hamiltonian contains the Raman Hamiltonian and microwave coupling the two bottom states have been studied in the limits of small and big photon numbers in the drive field. Another picture change removed the microwave coupler to all orders and simplified analysis. New possibilities of inversionless generation were found.

Transfer and Dynamic Inversion of Coassembled Supramolecular Chirality through 2D-Sheet to Rolled-Up Tubular Structure.

PubMed

Choi, Heekyoung; Cho, Kang Jin; Seo, Hyowon; Ahn, Junho; Liu, Jinying; Lee, Shim Sung; Kim, Hyungjun; Feng, Chuanliang; Jung, Jong Hwa

2017-12-13

Transfer and inversion of supramolecular chirality from chiral calix[4]arene analogs (3D and 3L) with an alanine moiety to an achiral bipyridine derivative (1) with glycine moieties in a coassembled hydrogel are demonstrated. Molecular chirality of 3D and 3L could transfer supramolecular chirality to an achiral bipyridine derivative 1. Moreover, addition of 0.6 equiv of 3D or 3L to 1 induced supramolecular chirality inversion of 1. More interestingly, the 2D-sheet structure of the coassembled hydrogels formed with 0.2 equiv of 3D or 3L changed to a rolled-up tubular structure in the presence of 0.6 equiv of 3D or 3L. The chirality inversion and morphology change are mainly mediated by intermolecular hydrogen-bonding interactions between the achiral and chiral molecules, which might be induced by reorientations of the assembled molecules, confirmed by density functional theory calculations.

Phylogenetic niche conservatism explains an inverse latitudinal diversity gradient in freshwater arthropods

PubMed Central

Morinière, Jérôme; Van Dam, Matthew H.; Hawlitschek, Oliver; Bergsten, Johannes; Michat, Mariano C.; Hendrich, Lars; Ribera, Ignacio; Toussaint, Emmanuel F.A.; Balke, Michael

2016-01-01

The underlying mechanisms responsible for the general increase in species richness from temperate regions to the tropics remain equivocal. Many hypotheses have been proposed to explain this astonishing pattern but additional empirical studies are needed to shed light on the drivers at work. Here we reconstruct the evolutionary history of the cosmopolitan diving beetle subfamily Colymbetinae, the majority of which are found in the Northern hemisphere, hence exhibiting an inversed latitudinal diversity gradient. We reconstructed a dated phylogeny using 12 genes, to investigate the biogeographical history and diversification dynamics in the Colymbetinae. We aimed to identify the role that phylogenetic niche conservatism plays in the inversed diversification pattern seen in this group. Our results suggest that Colymbetinae originated in temperate climates, which supports the hypothesis that their distribution is the result of an ancestral adaptation to temperate environmental conditions rather than tropical origins, and that temperate niche conservatism can generate and/or maintain inverse latitudinal diversity gradients. PMID:27215956

A fast new algorithm for a robot neurocontroller using inverse QR decomposition

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

Morris, A.S.; Khemaissia, S.

2000-01-01

A new adaptive neural network controller for robots is presented. The controller is based on direct adaptive techniques. Unlike many neural network controllers in the literature, inverse dynamical model evaluation is not required. A numerically robust, computationally efficient processing scheme for neutral network weight estimation is described, namely, the inverse QR decomposition (INVQR). The inverse QR decomposition and a weighted recursive least-squares (WRLS) method for neural network weight estimation is derived using Cholesky factorization of the data matrix. The algorithm that performs the efficient INVQR of the underlying space-time data matrix may be implemented in parallel on a triangular array.more » Furthermore, its systolic architecture is well suited for VLSI implementation. Another important benefit is well suited for VLSI implementation. Another important benefit of the INVQR decomposition is that it solves directly for the time-recursive least-squares filter vector, while avoiding the sequential back-substitution step required by the QR decomposition approaches.« less

Rheology of U-Shaped Granular Particles

NASA Astrophysics Data System (ADS)

Hill, Matthew; Franklin, Scott

We study the response of cylindrical samples of U-shaped granular particles (staples) to extensional loads. Samples elongate in discrete bursts (events) corresponding to particles rearranging and re-entangling. Previous research on samples of constant cross-sectional area found a Weibullian weakest-link theory could explain the distribution of yield points. We now vary the cross-sectional area, and find that the maximum yield pressure (force/area) is a function of particle number density and independent of area. The probability distribution function of important event characteristics -- the stress increase before an event and stress released during an event -- both fall of inversely with magnitude, reminiscent of avalanche dynamics. Fourier transforms of the fluctuating force (or stress) scales inversely with frequency, suggesting dry friction plays a role in the rearrangements. Finally, there is some evidence that dynamics are sensitive to the stiffness of the tensile testing machine, although an explanation for this behavior is unknown.

Influence of grain size on the mechanical properties of nano-crystalline copper; insights from molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Rida, A.; Makke, A.; Rouhaud, E.; Micoulaut, M.

2017-10-01

We use molecular dynamics simulations to study the mechanical properties of a columnar nanocrystalline copper with a mean grain size between 8.91 nm and 24 nm. The used samples were generated by using a melting cooling method. These samples were submitted to uniaxial tensile test. The results reveal the presence of a critical mean grain size between 16 and 20 nm, where there is an inversion in the conventional Hall-Petch tendency. This inversion is illustrated by the increase of flow stress with the increase of the mean grain size. This transition is caused by shifting of the deformation mechanism from dislocations to a combination of grain boundaries sliding and dislocations. Moreover, the effect of temperature on the mechanical properties of nanocrystalline copper has been investigated. The results show a decrease of the flow stress and Young's modulus when the temperature increases.

Low-temperature anomalies in the dynamic elastic moduli of cubic AIIBVI crystals with 3d-transition metal impurities

NASA Astrophysics Data System (ADS)

Lonchakov, A. T.

2011-04-01

A negative paramagnetic contribution to the dynamic elastic moduli is identified in AIIBVI:3d wide band-gap compounds for the first time. It appears as a paramagnetic elastic, or, briefly, paraelastic, susceptibility. These compounds are found to have a linear temperature dependence for the inverse paraelastic susceptibility. This is explained by a contribution from the diagonal matrix elements of the orbit-lattice interaction operators in the energy of the spin-orbital states of the 3d-ion as a function of applied stress (by analogy with the Curie contribution to the magnetic susceptibility). The inverse paraelastic susceptibility of AIIBVI crystals containing non-Kramers 3d-ions is found to deviate from linearity with decreasing temperature and reaches saturation. This effect is explained by a contribution from nondiagonal matrix elements (analogous to the well known van Vleck contribution to the magnetic susceptibility of paramagnets).

X-38 Application of Dynamic Inversion Flight Control

NASA Technical Reports Server (NTRS)

Wacker, Roger; Munday, Steve; Merkle, Scott

2001-01-01

This paper summarizes the application of a nonlinear dynamic inversion (DI) flight control system (FCS) to an autonomous flight test vehicle in NASA's X-38 Project, a predecessor to the International Space Station (ISS) Crew Return Vehicle (CRV). Honeywell's Multi-Application Control-H (MACH) is a parameterized FCS design architecture including both model-based DI rate-compensation and classical P+I command-tracking. MACH was adopted by X-38 in order to shorten the design cycle time for different vehicle shapes and flight envelopes and evolving aerodynamic databases. Specific design issues and analysis results are presented for the application of MACH to the 3rd free flight (FF3) of X-38 Vehicle 132 (V132). This B-52 drop test, occurring on March 30, 2000, represents the first flight test of MACH and one of the first few known applications of DI in the primary FCS of an autonomous flight test vehicle.

Using Ankle Bracing and Taping to Decrease Range of Motion and Velocity During Inversion Perturbation While Walking.

PubMed

Hall, Emily A; Simon, Janet E; Docherty, Carrie L

2016-04-01

Prophylactic ankle supports are commonly used. However, the effectiveness of external supports in preventing an inversion stress has been debated. To evaluate how ankle bracing and taping affect inversion range of motion, time to maximum inversion, inversion velocity, and perceived ankle stability compared with a control condition during a dynamic inversion perturbation while walking. Crossover study. Research laboratory. A total of 42 physically active participants (16 men, 26 women; age = 21.2 ± 3.3 years, height = 168.9 ± 8.9 cm, mass = 66.1 ± 11.4 kg) volunteered. Participants walked on a custom-built walkway that suddenly inverted their ankles to 30° in 3 conditions: brace, tape, and control (no external support). We used an ASO ankle brace for the brace condition and a closed basketweave technique for the tape condition. Three trials were completed for each condition. Main Outcome Measure(s) Maximum inversion (degrees), time to maximum inversion (milliseconds), and inversion velocity (degrees per second) were measured using an electrogoniometer, and perceived stability (centimeters) was measured using a visual analog scale. Maximum inversion decreased more in the brace condition (20.1°) than in the control (25.3°) or tape (22.3°) conditions (both P values = .001), and the tape condition restricted inversion more than the control condition (P = .001). Time to maximum inversion was greater in the brace condition (143.5 milliseconds) than in the control (123.7 milliseconds; P = .001) or tape (130.7 milliseconds; P = .009) conditions and greater in the tape than in the control condition (P = .02). Inversion velocity was slower in the brace condition (142.6°/s) than in the control (209.1°/s) or tape (174.3°/s) conditions (both P values = .001) and slower in the tape than in the control condition (P = .001). Both the brace and tape conditions provided more perceived stability (0.98 cm and 0.94 cm, respectively) than the control condition (2.38 cm; both P values = .001). Both prophylactic conditions affected inversion range of motion, time to maximum inversion, inversion velocity, and perceived ankle stability. However, bracing provided more restriction at a slower rate than taping.

Using Ankle Bracing and Taping to Decrease Range of Motion and Velocity During Inversion Perturbation While Walking

PubMed Central

Hall, Emily A.; Simon, Janet E.; Docherty, Carrie L.

2016-01-01

Context:  Prophylactic ankle supports are commonly used. However, the effectiveness of external supports in preventing an inversion stress has been debated. Objective:  To evaluate how ankle bracing and taping affect inversion range of motion, time to maximum inversion, inversion velocity, and perceived ankle stability compared with a control condition during a dynamic inversion perturbation while walking. Design:  Crossover study. Setting:  Research laboratory. Patients or Other Participants:  A total of 42 physically active participants (16 men, 26 women; age = 21.2 ± 3.3 years, height = 168.9 ± 8.9 cm, mass = 66.1 ± 11.4 kg) volunteered. Intervention(s):  Participants walked on a custom-built walkway that suddenly inverted their ankles to 30° in 3 conditions: brace, tape, and control (no external support). We used an ASO ankle brace for the brace condition and a closed basketweave technique for the tape condition. Three trials were completed for each condition. Main Outcome Measure(s):  Maximum inversion (degrees), time to maximum inversion (milliseconds), and inversion velocity (degrees per second) were measured using an electrogoniometer, and perceived stability (centimeters) was measured using a visual analog scale. Results:  Maximum inversion decreased more in the brace condition (20.1°) than in the control (25.3°) or tape (22.3°) conditions (both P values = .001), and the tape condition restricted inversion more than the control condition (P = .001). Time to maximum inversion was greater in the brace condition (143.5 milliseconds) than in the control (123.7 milliseconds; P = .001) or tape (130.7 milliseconds; P = .009) conditions and greater in the tape than in the control condition (P = .02). Inversion velocity was slower in the brace condition (142.6°/s) than in the control (209.1°/s) or tape (174.3°/s) conditions (both P values = .001) and slower in the tape than in the control condition (P = .001). Both the brace and tape conditions provided more perceived stability (0.98 cm and 0.94 cm, respectively) than the control condition (2.38 cm; both P values = .001). Conclusions:  Both prophylactic conditions affected inversion range of motion, time to maximum inversion, inversion velocity, and perceived ankle stability. However, bracing provided more restriction at a slower rate than taping. PMID:27111586

Dynamic data integration and stochastic inversion of a confined aquifer

NASA Astrophysics Data System (ADS)

Wang, D.; Zhang, Y.; Irsa, J.; Huang, H.; Wang, L.

2013-12-01

Much work has been done in developing and applying inverse methods to aquifer modeling. The scope of this paper is to investigate the applicability of a new direct method for large inversion problems and to incorporate uncertainty measures in the inversion outcomes (Wang et al., 2013). The problem considered is a two-dimensional inverse model (50×50 grid) of steady-state flow for a heterogeneous ground truth model (500×500 grid) with two hydrofacies. From the ground truth model, decreasing number of wells (12, 6, 3) were sampled for facies types, based on which experimental indicator histograms and directional variograms were computed. These parameters and models were used by Sequential Indicator Simulation to generate 100 realizations of hydrofacies patterns in a 100×100 (geostatistical) grid, which were conditioned to the facies measurements at wells. These realizations were smoothed with Simulated Annealing, coarsened to the 50×50 inverse grid, before they were conditioned with the direct method to the dynamic data, i.e., observed heads and groundwater fluxes at the same sampled wells. A set of realizations of estimated hydraulic conductivities (Ks), flow fields, and boundary conditions were created, which centered on the 'true' solutions from solving the ground truth model. Both hydrofacies conductivities were computed with an estimation accuracy of ×10% (12 wells), ×20% (6 wells), ×35% (3 wells) of the true values. For boundary condition estimation, the accuracy was within × 15% (12 wells), 30% (6 wells), and 50% (3 wells) of the true values. The inversion system of equations was solved with LSQR (Paige et al, 1982), for which coordinate transform and matrix scaling preprocessor were used to improve the condition number (CN) of the coefficient matrix. However, when the inverse grid was refined to 100×100, Gaussian Noise Perturbation was used to limit the growth of the CN before the matrix solve. To scale the inverse problem up (i.e., without smoothing and coarsening and therefore reducing the associated estimation uncertainty), a parallel LSQR solver was written and verified. For the 50×50 grid, the parallel solver sped up the serial solution time by 14X using 4 CPUs (research on parallel performance and scaling is ongoing). A sensitivity analysis was conducted to examine the relation between the observed data and the inversion outcomes, where measurement errors of increasing magnitudes (i.e., ×1, 2, 5, 10% of the total head variation and up to ×2% of the total flux variation) were imposed on the observed data. Inversion results were stable but the accuracy of Ks and boundary estimation degraded with increasing errors, as expected. In particular, quality of the observed heads is critical to hydraulic head recovery, while quality of the observed fluxes plays a dominant role in K estimation. References: Wang, D., Y. Zhang, J. Irsa, H. Huang, and L. Wang (2013), Data integration and stochastic inversion of a confined aquifer with high performance computing, Advances in Water Resources, in preparation. Paige, C. C., and M. A. Saunders (1982), LSQR: an algorithm for sparse linear equations and sparse least squares, ACM Transactions on Mathematical Software, 8(1), 43-71.

Elite synchronized swimmers display decreased energy availability during intensified training.

PubMed

Schaal, K; Tiollier, E; Le Meur, Y; Casazza, G; Hausswirth, C

2017-09-01

Elite synchronized swimmers follow high-volume training regimen that result in elevated rates of exercise energy expenditure (ExEE). While adequate energy intake (EI) is important to optimize recovery, a number of sport-specific constraints may lead to chronically low energy availability (EA = EI-ExEE). This study aimed to quantify changes in EA, endocrine markers of energy conservation, and perceived fatigue in synchronized swimmers, during a week of baseline training followed by 4 weeks of intensified training (IT). EI, ExEE, and body composition were measured in nine swimmers at Baseline, midpoint (IT WK 2 ), and end of IT (IT WK 4 ). Waking saliva samples were obtained to measure [leptin] s , [ghrelin] s , and [cortisol] s . Fatigue ratings were provided daily. ExEE increased by 27% during IT. Swimmers increased EI from Baseline to IT WK 2 , but decreased it significantly from IT WK 2 to IT WK 4 . EA, fat mass, and [leptin] s decreased from Baseline to IT WK 4 , while [ghrelin] s increased significantly. Fatigue at IT WK 4 was inversely correlated with Baseline EI and EA. The significant decrease in EA was accompanied by endocrine signs of energy conservation in elite swimmers. As perceived fatigue was associated with low EA, particular attention should be paid to these athletes' energy intake during phases of heavy training. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Tissue factor pathway inhibitor, activated protein C resistance, and risk of ischemic stroke due to postmenopausal hormone therapy

PubMed Central

Rossouw, Jacques E; Johnson, Karen C; Pettinger, Mary; Cushman, Mary; Sandset, Per Morten; Kuller, Lewis; Rosendaal, Frits; Rosing, Jan; Wasserthal-Smoller, Sylvia; Martin, Lisa W; Manson, JoAnn E; Lakshminarayan, Kamakshi; Merino, Jose G; Lynch, John

2012-01-01

Background and Purpose To test whether changes in plasma tissue factor pathway inhibitor (TFPI) levels or activated protein C resistance (normalized APC resistance ratio, nAPCsr) modify the increased risk of ischemic stroke due to postmenopausal hormone therapy (PHT). Methods Nested case-control study of 455 cases of ischemic stroke and 565 matched controls in the Women’s Health Initiative trials of PHT. Results Baseline free TFPI was associated with ischemic stroke risk, OR (95% CI) per SD increase = 1.17 (1.01, 1.37, p=0.039, but baseline nAPCsr was not, OR per SD increase = 0.89 (0.75, 1.05), p=0.15. Baseline TFPI levels and nAPCsr did not modify the effect of PHT on ischemic stroke. Treatment-induced mean changes of -28% in free TFPI and +65% in nAPCsr did not change the risk of ischemic stroke (interaction p = 0.452 and 0.971 respectively). In subgroup analyses baseline nAPCsr was inversely associated with lacunar strokes, OR per SD increase = 0.74 (0.57, 0.96), p=0.025, and baseline free TFPI interacted with treatment to increase large vessel atherosclerotic strokes, p=0.008. Conclusions Pro-coagulant changes in TFPI or nAPCsr do not modify the increased ischemic stroke risk due to PHT. PMID:22363056

Geodetic positioning using a global positioning system of satellites

NASA Technical Reports Server (NTRS)

Fell, P. J.

1980-01-01

Geodetic positioning using range, integrated Doppler, and interferometric observations from a constellation of twenty-four Global Positioning System satellites is analyzed. A summary of the proposals for geodetic positioning and baseline determination is given which includes a description of measurement techniques and comments on rank deficiency and error sources. An analysis of variance comparison of range, Doppler, and interferometric time delay to determine their relative geometric strength for baseline determination is included. An analytic examination to the effect of a priori constraints on positioning using simultaneous observations from two stations is presented. Dynamic point positioning and baseline determination using range and Doppler is examined in detail. Models for the error sources influencing dynamic positioning are developed. Included is a discussion of atomic clock stability, and range and Doppler observation error statistics based on random correlated atomic clock error are derived.

Robust Adaptive Flight Control Design of Air-breathing Hypersonic Vehicles

DTIC Science & Technology

2016-12-07

dynamic inversion controller design for a non -minimum phase hypersonic vehicle is derived by Kuipers et al. [2008]. Moreover, integrated guidance and...stabilization time for inner loop variables is lesser than the intermediate loop variables because of the three-loop-control design methodology . The control...adaptive design . Control Engineering Practice, 2016. Michael A Bolender and David B Doman. A non -linear model for the longitudinal dynamics of a

A Discrete Events Delay Differential System Model for Transmission of Vancomycin-Resistant Enterococcus (VRE) in Hospitals

DTIC Science & Technology

2010-09-19

estimated directly form the surveillance data Infection control measures were implemented in the form of health care worker hand - hygiene before and after...hospital infections , is used to motivate possibilities of modeling nosocomial infec- tion dynamics. This is done in the context of hospital monitoring and...model development. Key Words: Delay equations, discrete events, nosocomial infection dynamics, surveil- lance data, inverse problems, parameter

Construction of non-Markovian coarse-grained models employing the Mori-Zwanzig formalism and iterative Boltzmann inversion

NASA Astrophysics Data System (ADS)

Yoshimoto, Yuta; Li, Zhen; Kinefuchi, Ikuya; Karniadakis, George Em

2017-12-01

We propose a new coarse-grained (CG) molecular simulation technique based on the Mori-Zwanzig (MZ) formalism along with the iterative Boltzmann inversion (IBI). Non-Markovian dissipative particle dynamics (NMDPD) taking into account memory effects is derived in a pairwise interaction form from the MZ-guided generalized Langevin equation. It is based on the introduction of auxiliary variables that allow for the replacement of a non-Markovian equation with a Markovian one in a higher dimensional space. We demonstrate that the NMDPD model exploiting MZ-guided memory kernels can successfully reproduce the dynamic properties such as the mean square displacement and velocity autocorrelation function of a Lennard-Jones system, as long as the memory kernels are appropriately evaluated based on the Volterra integral equation using the force-velocity and velocity-velocity correlations. Furthermore, we find that the IBI correction of a pair CG potential significantly improves the representation of static properties characterized by a radial distribution function and pressure, while it has little influence on the dynamic processes. Our findings suggest that combining the advantages of both the MZ formalism and IBI leads to an accurate representation of both the static and dynamic properties of microscopic systems that exhibit non-Markovian behavior.

Activated dynamics in dense fluids of attractive nonspherical particles. II. Elasticity, barriers, relaxation, fragility, and self-diffusion

NASA Astrophysics Data System (ADS)

Tripathy, Mukta; Schweizer, Kenneth S.

2011-04-01

In paper II of this series we apply the center-of-mass version of Nonlinear Langevin Equation theory to study how short-range attractive interactions influence the elastic shear modulus, transient localization length, activated dynamics, and kinetic arrest of a variety of nonspherical particle dense fluids (and the spherical analog) as a function of volume fraction and attraction strength. The activation barrier (roughly the natural logarithm of the dimensionless relaxation time) is predicted to be a rich function of particle shape, volume fraction, and attraction strength, and the dynamic fragility varies significantly with particle shape. At fixed volume fraction, the barrier grows in a parabolic manner with inverse temperature nondimensionalized by an onset value, analogous to what has been established for thermal glass-forming liquids. Kinetic arrest boundaries lie at significantly higher volume fractions and attraction strengths relative to their dynamic crossover analogs, but their particle shape dependence remains the same. A limited universality of barrier heights is found based on the concept of an effective mean-square confining force. The mean hopping time and self-diffusion constant in the attractive glass region of the nonequilibrium phase diagram is predicted to vary nonmonotonically with attraction strength or inverse temperature, qualitatively consistent with recent computer simulations and colloid experiments.

Reactivating dynamics for the susceptible-infected-susceptible model: a simple method to simulate the absorbing phase

NASA Astrophysics Data System (ADS)

Macedo-Filho, A.; Alves, G. A.; Costa Filho, R. N.; Alves, T. F. A.

2018-04-01

We investigated the susceptible-infected-susceptible model on a square lattice in the presence of a conjugated field based on recently proposed reactivating dynamics. Reactivating dynamics consists of reactivating the infection by adding one infected site, chosen randomly when the infection dies out, avoiding the dynamics being trapped in the absorbing state. We show that the reactivating dynamics can be interpreted as the usual dynamics performed in the presence of an effective conjugated field, named the reactivating field. The reactivating field scales as the inverse of the lattice number of vertices n, which vanishes at the thermodynamic limit and does not affect any scaling properties including ones related to the conjugated field.

Closed-form dynamics of a hexarot parallel manipulator by means of the principle of virtual work

NASA Astrophysics Data System (ADS)

Pedrammehr, Siamak; Nahavandi, Saeid; Abdi, Hamid

2018-04-01

In this research, a systematic approach to solving the inverse dynamics of hexarot manipulators is addressed using the methodology of virtual work. For the first time, a closed form of the mathematical formulation of the standard dynamic model is presented for this class of mechanisms. An efficient algorithm for solving this closed-form dynamic model of the mechanism is developed and it is used to simulate the dynamics of the system for different trajectories. Validation of the proposed model is performed using SimMechanics and it is shown that the results of the proposed mathematical model match with the results obtained by the SimMechanics model.

Dynamic loading and stress life analysis of permanent space station modules

NASA Astrophysics Data System (ADS)

Anisimov, A. V.; Krokhin, I. A.; Likhoded, A. I.; Malinin, A. A.; Panichkin, N. G.; Sidorov, V. V.; Titov, V. A.

2016-11-01

Some methodological approaches to solving several key problems of dynamic loading and structural strength analysis of Permanent Space Station (PSS)modules developed on the basis of the working experience of Soviet and Russian PSS and the International Space station (ISS) are presented. The solutions of the direct and semi-inverse problems of PSS structure dynamics are mathematically stated. Special attention is paid to the use of the results of ground structural strength tests of space station modules and the data on the actual flight actions on the station and its dynamic responses in the orbital operation regime. The procedure of determining the dynamics and operation life parameters of elements of the PSS modules is described.

Prospective in-patient cohort study of moves between levels of therapeutic security: the DUNDRUM-1 triage security, DUNDRUM-3 programme completion and DUNDRUM-4 recovery scales and the HCR-20.

PubMed

Davoren, Mary; O'Dwyer, Sarah; Abidin, Zareena; Naughton, Leena; Gibbons, Olivia; Doyle, Elaine; McDonnell, Kim; Monks, Stephen; Kennedy, Harry G

2012-07-13

We examined whether new structured professional judgment instruments for assessing need for therapeutic security, treatment completion and recovery in forensic settings were related to moves from higher to lower levels of therapeutic security and added anything to assessment of risk. This was a prospective naturalistic twelve month observational study of a cohort of patients in a forensic hospital placed according to their need for therapeutic security along a pathway of moves from high to progressively less secure units in preparation for discharge. Patients were assessed using the DUNDRUM-1 triage security scale, the DUNDRUM-3 programme completion scale and the DUNDRUM-4 recovery scale and assessments of risk of violence, self harm and suicide, symptom severity and global function. Patients were subsequently observed for positive moves to less secure units and negative moves to more secure units. There were 86 male patients at baseline with mean follow-up 0.9 years, 11 positive and 9 negative moves. For positive moves, logistic regression indicated that along with location at baseline, the DUNDRUM-1, HCR-20 dynamic and PANSS general symptom scores were associated with subsequent positive moves. The receiver operating characteristic was significant for the DUNDRUM-1 while ANOVA co-varying for both location at baseline and HCR-20 dynamic score was significant for DUNDRUM-1. For negative moves, logistic regression showed DUNDRUM-1 and HCR-20 dynamic scores were associated with subsequent negative moves, along with DUNDRUM-3 and PANSS negative symptoms in some models. The receiver operating characteristic was significant for the DUNDRUM-4 recovery and HCR-20 dynamic scores with DUNDRUM-1, DUNDRUM-3, PANSS general and GAF marginal. ANOVA co-varying for both location at baseline and HCR-20 dynamic scores showed only DUNDRUM-1 and PANSS negative symptoms associated with subsequent negative moves. Clinicians appear to decide moves based on combinations of current and imminent (dynamic) risk measured by HCR-20 dynamic score and historical seriousness of risk as measured by need for therapeutic security (DUNDRUM-1) in keeping with Scott's formulation of risk and seriousness. The DUNDRUM-3 programme completion and DUNDRUM-4 recovery scales have utility as dynamic measures that can off-set perceived 'dangerousness'.

Prospective in-patient cohort study of moves between levels of therapeutic security: the DUNDRUM-1 triage security, DUNDRUM-3 programme completion and DUNDRUM-4 recovery scales and the HCR-20

PubMed Central

2012-01-01

Background We examined whether new structured professional judgment instruments for assessing need for therapeutic security, treatment completion and recovery in forensic settings were related to moves from higher to lower levels of therapeutic security and added anything to assessment of risk. Methods This was a prospective naturalistic twelve month observational study of a cohort of patients in a forensic hospital placed according to their need for therapeutic security along a pathway of moves from high to progressively less secure units in preparation for discharge. Patients were assessed using the DUNDRUM-1 triage security scale, the DUNDRUM-3 programme completion scale and the DUNDRUM-4 recovery scale and assessments of risk of violence, self harm and suicide, symptom severity and global function. Patients were subsequently observed for positive moves to less secure units and negative moves to more secure units. Results There were 86 male patients at baseline with mean follow-up 0.9 years, 11 positive and 9 negative moves. For positive moves, logistic regression indicated that along with location at baseline, the DUNDRUM-1, HCR-20 dynamic and PANSS general symptom scores were associated with subsequent positive moves. The receiver operating characteristic was significant for the DUNDRUM-1 while ANOVA co-varying for both location at baseline and HCR-20 dynamic score was significant for DUNDRUM-1. For negative moves, logistic regression showed DUNDRUM-1 and HCR-20 dynamic scores were associated with subsequent negative moves, along with DUNDRUM-3 and PANSS negative symptoms in some models. The receiver operating characteristic was significant for the DUNDRUM-4 recovery and HCR-20 dynamic scores with DUNDRUM-1, DUNDRUM-3, PANSS general and GAF marginal. ANOVA co-varying for both location at baseline and HCR-20 dynamic scores showed only DUNDRUM-1 and PANSS negative symptoms associated with subsequent negative moves. Conclusions Clinicians appear to decide moves based on combinations of current and imminent (dynamic) risk measured by HCR-20 dynamic score and historical seriousness of risk as measured by need for therapeutic security (DUNDRUM-1) in keeping with Scott's formulation of risk and seriousness. The DUNDRUM-3 programme completion and DUNDRUM-4 recovery scales have utility as dynamic measures that can off-set perceived 'dangerousness'. PMID:22794187

Evaluation of rotor-bearing system dynamic response to unbalance. [air conditioning equipment

NASA Technical Reports Server (NTRS)

Thaller, R. E.; Ozimek, D. W.

1979-01-01

The vibration environment within air conditioner rotating machinery referred to as an air cycle machine (ACM) was investigated to effectively increase ACM reliability. To assist in the selection of design changes which would result in improved ACM performance, various design modifications were incorporated into a baseline ACM configuration. For each design change, testing was conducted with the best balance achieveable (baseline) and with various degrees of unbalance. Relationships between unbalance (within the context of design changes) and the parameters associated with design goals were established. The results of rotor dynamics tests used to establish these relationships are presented.

ALMA Long Baseline Observations of the Dynamical Atmospheres of AGB Stars

NASA Astrophysics Data System (ADS)

Vlemmings, Wouter

2018-04-01

I will present the current status of ALMA long baseline observations of W Hya, R Leo, R Dor and Mira. We have recently obtained band 4, 6 and 7 observations of the line and continuum emission tracing the temperature and dynamics in their extended atmosphere. Our preliminary analysis confirms our previous detection of a hotspot on W Hya, and reveals unexpected lines in most of the sources, as well as possible fast rotation in the atmopshere of one of the stars. The observations show the unique power of ALMA in observing the extended stellar atmospheres.

Computing Generalized Matrix Inverse on Spiking Neural Substrate.

PubMed

Shukla, Rohit; Khoram, Soroosh; Jorgensen, Erik; Li, Jing; Lipasti, Mikko; Wright, Stephen

2018-01-01

Emerging neural hardware substrates, such as IBM's TrueNorth Neurosynaptic System, can provide an appealing platform for deploying numerical algorithms. For example, a recurrent Hopfield neural network can be used to find the Moore-Penrose generalized inverse of a matrix, thus enabling a broad class of linear optimizations to be solved efficiently, at low energy cost. However, deploying numerical algorithms on hardware platforms that severely limit the range and precision of representation for numeric quantities can be quite challenging. This paper discusses these challenges and proposes a rigorous mathematical framework for reasoning about range and precision on such substrates. The paper derives techniques for normalizing inputs and properly quantizing synaptic weights originating from arbitrary systems of linear equations, so that solvers for those systems can be implemented in a provably correct manner on hardware-constrained neural substrates. The analytical model is empirically validated on the IBM TrueNorth platform, and results show that the guarantees provided by the framework for range and precision hold under experimental conditions. Experiments with optical flow demonstrate the energy benefits of deploying a reduced-precision and energy-efficient generalized matrix inverse engine on the IBM TrueNorth platform, reflecting 10× to 100× improvement over FPGA and ARM core baselines.

Changes in Physical Activity Domains During the Transition Out of High School: Psychosocial and Environmental Correlates.

PubMed

Molina-García, Javier; Queralt, Ana; Castillo, Isabel; Sallis, James F

2015-10-01

This study examined changes in multiple physical activity domains during the transition out of high school and psychosocial and environmental determinants of these changes. A 1-year prospective study was designed. The baseline sample was composed of 244 last-year high school students (58.6% female) from Valencia, Spain. Follow-up rate was 46%. Physical activity and potential determinants were measured by the Global Physical Activity Questionnaire and other evaluated scales in 2 waves. Total physical activity and active commuting (AC) decreased, respectively, by 21% and 36%, only in males. At time 1, access to car/motorbike (inverse), planning/psychosocial barriers (inverse), street connectivity (positive) and parental education (inverse) were significantly associated with AC (P < .05). Prospectively, the increase in distance to school/workplace was associated with AC decrease among males (P < .001). In both genders, there was a decrease in leisure-time physical activity (LTPA; -35% in males, -43% in females). At time 1, self-efficacy and social support were positive correlates of LTPA (P < .05). Social support decreases were associated with reductions in LTPA for males (P < .05). Several psychosocial and environmental correlates of physical activity change were identified, and these are promising targets for interventions.

TOPEX/POSEIDON tides estimated using a global inverse model

NASA Technical Reports Server (NTRS)

Egbert, Gary D.; Bennett, Andrew F.; Foreman, Michael G. G.

1994-01-01

Altimetric data from the TOPEX/POSEIDON mission will be used for studies of global ocean circulation and marine geophysics. However, it is first necessary to remove the ocean tides, which are aliased in the raw data. The tides are constrained by the two distinct types of information: the hydrodynamic equations which the tidal fields of elevations and velocities must satisfy, and direct observational data from tide gauges and satellite altimetry. Here we develop and apply a generalized inverse method, which allows us to combine rationally all of this information into global tidal fields best fitting both the data and the dynamics, in a least squares sense. The resulting inverse solution is a sum of the direct solution to the astronomically forced Laplace tidal equations and a linear combination of the representers for the data functionals. The representer functions (one for each datum) are determined by the dynamical equations, and by our prior estimates of the statistics or errors in these equations. Our major task is a direct numerical calculation of these representers. This task is computationally intensive, but well suited to massively parallel processing. By calculating the representers we reduce the full (infinite dimensional) problem to a relatively low-dimensional problem at the outset, allowing full control over the conditioning and hence the stability of the inverse solution. With the representers calculated we can easily update our model as additional TOPEX/POSEIDON data become available. As an initial illustration we invert harmonic constants from a set of 80 open-ocean tide gauges. We then present a practical scheme for direct inversion of TOPEX/POSEIDON crossover data. We apply this method to 38 cycles of geophysical data records (GDR) data, computing preliminary global estimates of the four principal tidal constituents, M(sub 2), S(sub 2), K(sub 1) and O(sub 1). The inverse solution yields tidal fields which are simultaneously smoother, and in better agreement with altimetric and ground truth data, than previously proposed tidal models. Relative to the 'default' tidal corrections provided with the TOPEX/POSEIDON GDR, the inverse solution reduces crossover difference variances significantly (approximately 20-30%), even though only a small number of free parameters (approximately equal to 1000) are actually fit to the crossover data.

Use of a Textured Insole to Improve the Association Between Postural Balance and Ankle Discrimination in Young Male and Female Dancers.

PubMed

Steinberg, Nili; Waddington, Gordon; Adams, Roger; Karin, Janet; Tirosh, Oren

2015-12-01

Ballet dancers require a high level of postural balance (PB) and proprioception ability during performance. As textured insoles inserted into ballet shoes were found to improve proprioception ability, and better proprioceptive acuity was associated with better PB, the aim of the present study was to investigate whether the association between ankle inversion movement discrimination (AIMD) and PB changed following wearing textured insoles in young male and female dancers. Forty-four dancers from the Australian Ballet School, ages 14-19 yrs, were tested for static and dynamic PB and AIMD under two conditions: in ballet shoes, and in ballet shoes with textured insoles inserted. Female dancers demonstrated a significant inverse relationship between AIMD and static PB in the medio-lateral direction when wearing ballet shoes, but not when wearing textured insoles. Male dancers showed a non-monotonic relationship when tested with ballet shoes only, but a significant inverse relationship between AIMD and dynamic PB in the vertical direction and with the waist/head cross-correlation acceleration in the three movement directions when they were tested with textured insoles. Male dancers demonstrated an improved association between dynamic PB and proprioception ability when using textured insoles, suggesting that the increased afferent information from the plantar surface had a beneficial effect on proprioception feedback about their PB. Conversely, for female dancers, that association was present when wearing ballet shoes, but not when using textured insoles, suggesting that the increased afferent information for female dancers who already had high proprioception ability was "overloaded" by wearing the textured insoles.

Tidal stirring and phytoplankton bloom dynamics in an estuary

USGS Publications Warehouse

Cloern, J.E.

1991-01-01

In South San Francisco Bay, estuarine phytoplankton biomass fluctuates at the time scale of days to weeks; much of this variability is associated with fluctuations in tidal energy. During the spring seasons of every year from 1980-1990, episodic blooms occurred in which phytoplankton biomass rose from a baseline of 2-4mg chlorophyll a m-3, peaked at 20-40 chlorophyll a m-3, then returned to baseline values, all within several weeks. Each episode of biomass increase occurred during neap tides, and each bloom decline coincided with spring tides. This suggests that daily variations in the rate of vertical mixing by tidal stirring might control phytoplankton bloom dynamics in some estuaries. Simulation experiments with a numerical model of phytoplankton population dynamics support this hypothesis. -from Author

Pathway Concepts Experiment for Head-Down Synthetic Vision Displays

NASA Technical Reports Server (NTRS)

Prinzel, Lawrence J., III; Arthur, Jarvis J., III; Kramer, Lynda J.; Bailey, Randall E.

2004-01-01

Eight 757 commercial airline captains flew 22 approaches using the Reno Sparks 16R Visual Arrival under simulated Category I conditions. Approaches were flown using a head-down synthetic vision display to evaluate four tunnel ("minimal", "box", "dynamic pathway", "dynamic crow s feet") and three guidance ("ball", "tadpole", "follow-me aircraft") concepts and compare their efficacy to a baseline condition (i.e., no tunnel, ball guidance). The results showed that the tunnel concepts significantly improved pilot performance and situation awareness and lowered workload compared to the baseline condition. The dynamic crow s feet tunnel and follow-me aircraft guidance concepts were found to be the best candidates for future synthetic vision head-down displays. These results are discussed with implications for synthetic vision display design and future research.

Utilizing High-Performance Computing to Investigate Parameter Sensitivity of an Inversion Model for Vadose Zone Flow and Transport

NASA Astrophysics Data System (ADS)

Fang, Z.; Ward, A. L.; Fang, Y.; Yabusaki, S.

2011-12-01

High-resolution geologic models have proven effective in improving the accuracy of subsurface flow and transport predictions. However, many of the parameters in subsurface flow and transport models cannot be determined directly at the scale of interest and must be estimated through inverse modeling. A major challenge, particularly in vadose zone flow and transport, is the inversion of the highly-nonlinear, high-dimensional problem as current methods are not readily scalable for large-scale, multi-process models. In this paper we describe the implementation of a fully automated approach for addressing complex parameter optimization and sensitivity issues on massively parallel multi- and many-core systems. The approach is based on the integration of PNNL's extreme scale Subsurface Transport Over Multiple Phases (eSTOMP) simulator, which uses the Global Array toolkit, with the Beowulf-Cluster inspired parallel nonlinear parameter estimation software, BeoPEST in the MPI mode. In the eSTOMP/BeoPEST implementation, a pre-processor generates all of the PEST input files based on the eSTOMP input file. Simulation results for comparison with observations are extracted automatically at each time step eliminating the need for post-process data extractions. The inversion framework was tested with three different experimental data sets: one-dimensional water flow at Hanford Grass Site; irrigation and infiltration experiment at the Andelfingen Site; and a three-dimensional injection experiment at Hanford's Sisson and Lu Site. Good agreements are achieved in all three applications between observations and simulations in both parameter estimates and water dynamics reproduction. Results show that eSTOMP/BeoPEST approach is highly scalable and can be run efficiently with hundreds or thousands of processors. BeoPEST is fault tolerant and new nodes can be dynamically added and removed. A major advantage of this approach is the ability to use high-resolution geologic models to preserve the spatial structure in the inverse model, which leads to better parameter estimates and improved predictions when using the inverse-conditioned realizations of parameter fields.

Modeling the Dynamics of the Atmospheric Boundary Layer Over the Antarctic Plateau With a General Circulation Model

NASA Astrophysics Data System (ADS)

Vignon, Etienne; Hourdin, Frédéric; Genthon, Christophe; Van de Wiel, Bas J. H.; Gallée, Hubert; Madeleine, Jean-Baptiste; Beaumet, Julien

2018-01-01

Observations evidence extremely stable boundary layers (SBL) over the Antarctic Plateau and sharp regime transitions between weakly and very stable conditions. Representing such features is a challenge for climate models. This study assesses the modeling of the dynamics of the boundary layer over the Antarctic Plateau in the LMDZ general circulation model. It uses 1 year simulations with a stretched-grid over Dome C. The model is nudged with reanalyses outside of the Dome C region such as simulations can be directly compared to in situ observations. We underline the critical role of the downward longwave radiation for modeling the surface temperature. LMDZ reasonably represents the near-surface seasonal profiles of wind and temperature but strong temperature inversions are degraded by enhanced turbulent mixing formulations. Unlike ERA-Interim reanalyses, LMDZ reproduces two SBL regimes and the regime transition, with a sudden increase in the near-surface inversion with decreasing wind speed. The sharpness of the transition depends on the stability function used for calculating the surface drag coefficient. Moreover, using a refined vertical grid leads to a better reversed "S-shaped" relationship between the inversion and the wind. Sudden warming events associated to synoptic advections of warm and moist air are also well reproduced. Near-surface supersaturation with respect to ice is not allowed in LMDZ but the impact on the SBL structure is moderate. Finally, climate simulations with the free model show that the recommended configuration leads to stronger inversions and winds over the ice-sheet. However, the near-surface wind remains underestimated over the slopes of East-Antarctica.

Mantle viscosity structure constrained by joint inversions of seismic velocities and density

NASA Astrophysics Data System (ADS)

Rudolph, M. L.; Moulik, P.; Lekic, V.

2017-12-01

The viscosity structure of Earth's deep mantle affects the thermal evolution of Earth, the ascent of mantle upwellings, sinking of subducted oceanic lithosphere, and the mixing of compositional heterogeneities in the mantle. Modeling the long-wavelength dynamic geoid allows us to constrain the radial viscosity profile of the mantle. Typically, in inversions for the mantle viscosity structure, wavespeed variations are mapped into density variations using a constant- or depth-dependent scaling factor. Here, we use a newly developed joint model of anisotropic Vs, Vp, density and transition zone topographies to generate a suite of solutions for the mantle viscosity structure directly from the seismologically constrained density structure. The density structure used to drive our forward models includes contributions from both thermal and compositional variations, including important contributions from compositionally dense material in the Large Low Velocity Provinces at the base of the mantle. These compositional variations have been neglected in the forward models used in most previous inversions and have the potential to significantly affect large-scale flow and thus the inferred viscosity structure. We use a transdimensional, hierarchical, Bayesian approach to solve the inverse problem, and our solutions for viscosity structure include an increase in viscosity below the base of the transition zone, in the shallow lower mantle. Using geoid dynamic response functions and an analysis of the correlation between the observed geoid and mantle structure, we demonstrate the underlying reason for this inference. Finally, we present a new family of solutions in which the data uncertainty is accounted for using covariance matrices associated with the mantle structure models.

Unscented Kalman filter assimilation of time-lapse self-potential data for monitoring solute transport

NASA Astrophysics Data System (ADS)

Cui, Yi-an; Liu, Lanbo; Zhu, Xiaoxiong

2017-08-01

Monitoring the extent and evolution of contaminant plumes in local and regional groundwater systems from existing landfills is critical in contamination control and remediation. The self-potential survey is an efficient and economical nondestructive geophysical technique that can be used to investigate underground contaminant plumes. Based on the unscented transform, we have built a Kalman filtering cycle to conduct time-lapse data assimilation for monitoring the transport of solute based on the solute transport experiment using a bench-scale physical model. The data assimilation was formed by modeling the evolution based on the random walk model and observation correcting based on the self-potential forward. Thus, monitoring self-potential data can be inverted by the data assimilation technique. As a result, we can reconstruct the dynamic process of the contaminant plume instead of using traditional frame-to-frame static inversion, which may cause inversion artifacts. The data assimilation inversion algorithm was evaluated through noise-added synthetic time-lapse self-potential data. The result of the numerical experiment shows validity, accuracy and tolerance to the noise of the dynamic inversion. To validate the proposed algorithm, we conducted a scaled-down sandbox self-potential observation experiment to generate time-lapse data that closely mimics the real-world contaminant monitoring setup. The results of physical experiments support the idea that the data assimilation method is a potentially useful approach for characterizing the transport of contamination plumes using the unscented Kalman filter (UKF) data assimilation technique applied to field time-lapse self-potential data.

Slip history and dynamic implications of the 1999 Chi-Chi, Taiwan, earthquake

USGS Publications Warehouse

Ji, C.; Helmberger, D.V.; Wald, D.J.; Ma, K.-F.

2003-01-01

We investigate the rupture process of the 1999 Chi-Chi, Taiwan, earthquake using extensive near-source observations, including three-component velocity waveforms at 36 strong motion stations and 119 GPS measurements. A three-plane fault geometry derived from our previous inversion using only static data [Ji et al., 2001] is applied. The slip amplitude, rake angle, rupture initiation time, and risetime function are inverted simultaneously with a recently developed finite fault inverse method that combines a wavelet transform approach with a simulated annealing algorithm [Ji et al., 2002b]. The inversion results are validated by the forward prediction of an independent data set, the teleseismic P and SH ground velocities, with notable agreement. The results show that the total seismic moment release of this earthquake is 2.7 ?? 1020 N m and that most of the slip occured in a triangular-shaped asperity involving two fault segments, which is consistent with our previous static inversion. The rupture front propagates with an average rupture velocity of ???2.0 km s-1, and the average slip duration (risetime) is 7.2 s. Several interesting observations related to the temporal evolution of the Chi-Chi earthquake are also investigated, including (1) the strong effect of the sinuous fault plane of the Chelungpu fault on spatial and temporal variations in slip history, (2) the intersection of fault 1 and fault 2 not being a strong impediment to the rupture propagation, and (3 the observation that the peak slip velocity near the surface is, in general, higher than on the deeper portion of the fault plane, as predicted by dynamic modeling.

Electron-phonon thermalization in a scalable method for real-time quantum dynamics

NASA Astrophysics Data System (ADS)

Rizzi, Valerio; Todorov, Tchavdar N.; Kohanoff, Jorge J.; Correa, Alfredo A.

2016-01-01

We present a quantum simulation method that follows the dynamics of out-of-equilibrium many-body systems of electrons and oscillators in real time. Its cost is linear in the number of oscillators and it can probe time scales from attoseconds to hundreds of picoseconds. Contrary to Ehrenfest dynamics, it can thermalize starting from a variety of initial conditions, including electronic population inversion. While an electronic temperature can be defined in terms of a nonequilibrium entropy, a Fermi-Dirac distribution in general emerges only after thermalization. These results can be used to construct a kinetic model of electron-phonon equilibration based on the explicit quantum dynamics.

Nonlinear system guidance in the presence of transmission zero dynamics

NASA Technical Reports Server (NTRS)

Meyer, G.; Hunt, L. R.; Su, R.

1995-01-01

An iterative procedure is proposed for computing the commanded state trajectories and controls that guide a possibly multiaxis, time-varying, nonlinear system with transmission zero dynamics through a given arbitrary sequence of control points. The procedure is initialized by the system inverse with the transmission zero effects nulled out. Then the 'steady state' solution of the perturbation model with the transmission zero dynamics intact is computed and used to correct the initial zero-free solution. Both time domain and frequency domain methods are presented for computing the steady state solutions of the possibly nonminimum phase transmission zero dynamics. The procedure is illustrated by means of linear and nonlinear examples.

Control of particle and power exhaust in pellet fuelled ITER DT scenarios employing integrated models

NASA Astrophysics Data System (ADS)

Wiesen, S.; Köchl, F.; Belo, P.; Kotov, V.; Loarte, A.; Parail, V.; Corrigan, G.; Garzotti, L.; Harting, D.

2017-07-01

The integrated model JINTRAC is employed to assess the dynamic density evolution of the ITER baseline scenario when fuelled by discrete pellets. The consequences on the core confinement properties, α-particle heating due to fusion and the effect on the ITER divertor operation, taking into account the material limitations on the target heat loads, are discussed within the integrated model. Using the model one can observe that stable but cyclical operational regimes can be achieved for a pellet-fuelled ITER ELMy H-mode scenario with Q  =  10 maintaining partially detached conditions in the divertor. It is shown that the level of divertor detachment is inversely correlated with the core plasma density due to α-particle heating, and thus depends on the density evolution cycle imposed by pellet ablations. The power crossing the separatrix to be dissipated depends on the enhancement of the transport in the pedestal region being linked with the pressure gradient evolution after pellet injection. The fuelling efficacy of the deposited pellet material is strongly dependent on the E  ×  B plasmoid drift. It is concluded that integrated models like JINTRAC, if validated and supported by realistic physics constraints, may help to establish suitable control schemes of particle and power exhaust in burning ITER DT-plasma scenarios.

Adaptive Flight Control Design with Optimal Control Modification on an F-18 Aircraft Model

NASA Technical Reports Server (NTRS)

Burken, John J.; Nguyen, Nhan T.; Griffin, Brian J.

2010-01-01

In the presence of large uncertainties, a control system needs to be able to adapt rapidly to regain performance. Fast adaptation is referred to as the implementation of adaptive control with a large adaptive gain to reduce the tracking error rapidly; however, a large adaptive gain can lead to high-frequency oscillations which can adversely affect the robustness of an adaptive control law. A new adaptive control modification is presented that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. The modification is based on the minimization of the Y2 norm of the tracking error, which is formulated as an optimal control problem. The optimality condition is used to derive the modification using the gradient method. The optimal control modification results in a stable adaptation and allows a large adaptive gain to be used for better tracking while providing sufficient robustness. A damping term (v) is added in the modification to increase damping as needed. Simulations were conducted on a damaged F-18 aircraft (McDonnell Douglas, now The Boeing Company, Chicago, Illinois) with both the standard baseline dynamic inversion controller and the adaptive optimal control modification technique. The results demonstrate the effectiveness of the proposed modification in tracking a reference model.

A novel protocol to evaluate ankle movements during reaching tasks using pediAnklebot.

PubMed

Martelli, Francesca; Palermo, Eduardo; Rossi, Stefano

2017-07-01

The aim of the study is to design a novel protocol to characterize the ankle movements during dorsal and plantar flexion reaching tasks using the pediAnklebot. Five healthy children were instructed to control a pointer and hit targets appearing on the monitor, by moving their ankle alternatively up and down. The protocol consisted of 60 targets, 30 up and 30 down, reachable via dorsiflexion and plantarflexion movements, respectively. Ankle angular displacements and torques were gathered by encoders and load cells embedded in the robot. Ankle motor performance was evaluated by means of kinematic, submovements and dynamic indices. Results suggest that (i) plantarflexion movements are faster and more accurate than the dorsiflexion ones, but children are able to perform with a higher level of smoothness the latter ones; (ii) children are able to stop the ankle movement more easily at the end of dorsiflexion rather than plantarflexion; (iii) the central nervous system plans plantarflexion and dorsiflexion movements with the same efficiency; (iv) children apply different torque levels during the two motor tasks and they cannot balance the inversion and eversion moments during dorsiflexion. These findings provide an important starting point for the assessment of a reference baseline of motor indices for the ankle joint.

An Inverse Optimal Control Approach to Explain Human Arm Reaching Control Based on Multiple Internal Models.

PubMed

Oguz, Ozgur S; Zhou, Zhehua; Glasauer, Stefan; Wollherr, Dirk

2018-04-03

Human motor control is highly efficient in generating accurate and appropriate motor behavior for a multitude of tasks. This paper examines how kinematic and dynamic properties of the musculoskeletal system are controlled to achieve such efficiency. Even though recent studies have shown that the human motor control relies on multiple models, how the central nervous system (CNS) controls this combination is not fully addressed. In this study, we utilize an Inverse Optimal Control (IOC) framework in order to find the combination of those internal models and how this combination changes for different reaching tasks. We conducted an experiment where participants executed a comprehensive set of free-space reaching motions. The results show that there is a trade-off between kinematics and dynamics based controllers depending on the reaching task. In addition, this trade-off depends on the initial and final arm configurations, which in turn affect the musculoskeletal load to be controlled. Given this insight, we further provide a discomfort metric to demonstrate its influence on the contribution of different inverse internal models. This formulation together with our analysis not only support the multiple internal models (MIMs) hypothesis but also suggest a hierarchical framework for the control of human reaching motions by the CNS.

Integration of Visual and Joint Information to Enable Linear Reaching Motions

NASA Astrophysics Data System (ADS)

Eberle, Henry; Nasuto, Slawomir J.; Hayashi, Yoshikatsu

2017-01-01

A new dynamics-driven control law was developed for a robot arm, based on the feedback control law which uses the linear transformation directly from work space to joint space. This was validated using a simulation of a two-joint planar robot arm and an optimisation algorithm was used to find the optimum matrix to generate straight trajectories of the end-effector in the work space. We found that this linear matrix can be decomposed into the rotation matrix representing the orientation of the goal direction and the joint relation matrix (MJRM) representing the joint response to errors in the Cartesian work space. The decomposition of the linear matrix indicates the separation of path planning in terms of the direction of the reaching motion and the synergies of joint coordination. Once the MJRM is numerically obtained, the feedfoward planning of reaching direction allows us to provide asymptotically stable, linear trajectories in the entire work space through rotational transformation, completely avoiding the use of inverse kinematics. Our dynamics-driven control law suggests an interesting framework for interpreting human reaching motion control alternative to the dominant inverse method based explanations, avoiding expensive computation of the inverse kinematics and the point-to-point control along the desired trajectories.

A non-local structural derivative model for characterization of ultraslow diffusion in dense colloids

NASA Astrophysics Data System (ADS)

Liang, Yingjie; Chen, Wen

2018-03-01

Ultraslow diffusion has been observed in numerous complicated systems. Its mean squared displacement (MSD) is not a power law function of time, but instead a logarithmic function, and in some cases grows even more slowly than the logarithmic rate. The distributed-order fractional diffusion equation model simply does not work for the general ultraslow diffusion. Recent study has used the local structural derivative to describe ultraslow diffusion dynamics by using the inverse Mittag-Leffler function as the structural function, in which the MSD is a function of inverse Mittag-Leffler function. In this study, a new stretched logarithmic diffusion law and its underlying non-local structural derivative diffusion model are proposed to characterize the ultraslow diffusion in aging dense colloidal glass at both the short and long waiting times. It is observed that the aging dynamics of dense colloids is a class of the stretched logarithmic ultraslow diffusion processes. Compared with the power, the logarithmic, and the inverse Mittag-Leffler diffusion laws, the stretched logarithmic diffusion law has better precision in fitting the MSD of the colloidal particles at high densities. The corresponding non-local structural derivative diffusion equation manifests clear physical mechanism, and its structural function is equivalent to the first-order derivative of the MSD.

Simulation of Constrained Musculoskeletal Systems in Task Space.

PubMed

Stanev, Dimitar; Moustakas, Konstantinos

2018-02-01

This paper proposes an operational task space formalization of constrained musculoskeletal systems, motivated by its promising results in the field of robotics. The change of representation requires different algorithms for solving the inverse and forward dynamics simulation in the task space domain. We propose an extension to the direct marker control and an adaptation of the computed muscle control algorithms for solving the inverse kinematics and muscle redundancy problems, respectively. Experimental evaluation demonstrates that this framework is not only successful in dealing with the inverse dynamics problem, but also provides an intuitive way of studying and designing simulations, facilitating assessment prior to any experimental data collection. The incorporation of constraints in the derivation unveils an important extension of this framework toward addressing systems that use absolute coordinates and topologies that contain closed kinematic chains. Task space projection reveals a more intuitive encoding of the motion planning problem, allows for better correspondence between observed and estimated variables, provides the means to effectively study the role of kinematic redundancy, and most importantly, offers an abstract point of view and control, which can be advantageous toward further integration with high level models of the precommand level. Task-based approaches could be adopted in the design of simulation related to the study of constrained musculoskeletal systems.

Chronically raised C-reactive protein is inversely associated with cortical β-amyloid in older adults with subjective memory complaints.

PubMed

Hooper, Claudie; De Souto Barreto, Philipe; Cantet, Christelle; Cesari, Matteo; Payoux, Pierre; Salabert, Anne Sophie; Vellas, Bruno

2018-04-25

Inflammation promotes amyloidogenesis in animals and markers of inflammation are associated with β-amyloid (Aβ) in humans. Hence, we sought to examine the cross-sectional associations between chronically elevated plasma C reactive protein (CRP) and cortical Aβ in 259 non-demented elderly individuals reporting subjective memory complaints from the Multidomain Alzheimer Preventive Trial (MAPT). Cortical-to-cerebellar standard uptake value ratios were obtained using [ 18 F] florbetapir positron emission tomography (PET). CRP was measured in plasma using immunoturbidity. Chronically raised CRP was defined as having 2 consecutively high CRP readings (>3 mg/l ≤ 10 mg/l) between study baseline and the 1 year visit (visits were performed at baseline, 6 months, 1 year and then annually). Associations were explored using adjusted multiple linear regression. Chronically raised CRP was found to be inversely associated with cortical Aβ (B-coefficient: -0.054, SE: 0.026, p = 0.040) and this association seemed to be specific to apolipoprotein E (Apo E) ε4 carriers (B-coefficient: -0.130, SE: 0.058, p = 0.027). CRP as an isolated reading measured closest to PET scan was also inversely associated with cortical Aβ when CRP was treated as a dichotomized variable (high CRP > 3 mg/l ≤ 10 mg/l, B-coefficient: -0.048, SE: 0.023, p = 0.043). Our preliminary findings suggest that inflammation might be beneficial in the early stages of Alzheimer's disease as the immune systems attempts to combat Aβ pathology particularly in ApoE ε4 carriers. Investigating the temporal relationships between cerebral Aβ and a panel of inflammatory markers would provide further evidence as to whether chronic inflammation might modulate amyloidogenesis in vivo. Copyright © 2018 Elsevier Inc. All rights reserved.

Near Infrared Cavity Ring-Down Spectroscopy for Isotopic Analyses of CH4 on Future Martian Surface Missions

NASA Technical Reports Server (NTRS)

Chen, Y.; Mahaffy P.; Holmes, V.; Burris, J.; Morey, P.; Lehmann, K.K.; Lollar, B. Sherwood; Lacrampe-Couloume, G.; Onstott, T.C.

2014-01-01

A compact Near Infrared Continuous Wave Cavity Ring-Down Spectrometer (near-IR-cw-CRDS) was developed as a candidate for future planetary surface missions. The optical cavity was made of titanium with rugged quartz windows to protect the delicate super cavity from the harsh environmental changes that it would experience during space flight and a Martian surface mission. This design assured the long-term stability of the system. The system applied three distributed feedback laser diodes (DFB-LD), two of which were tuned to the absorption line peaks of (sup 12)CH4 and (sup 13)CH4 at 6046.954 inverse centimeters and 6049.121 inverse centimeters, respectively. The third laser was tuned to a spectral-lines-free region for measuring the baseline cavity loss. The multiple laser design compensated for typical baseline drift of a CRDS system and, thus, improved the overall precision. A semiconductor optical amplifier (SOA) was used instead of an Acousto-Optic Module (AOM) to initiate the cavity ring-down events. It maintained high acquisition rates such as AOM, but consumed less power. High data acquisition rates combined with improved long-term stability yielded precise isotopic measurements in this near-IR region even though the strongest CH4 absorption line in this region is 140 times weaker than that of the strongest mid-IR absorption band. The current system has a detection limit of 1.4 times 10( sup –12) inverse centimeters for (sup 13)CH4. This limit corresponds to approximately 7 parts per trillion volume of CH4 at 100 Torrs. With no further improvements the detection limit of our current near IR-cw-CRDS at an ambient Martian pressure of approximately 6 Torrs (8 millibars) would be 0.25 parts per billion volume for one 3.3 minute long analysis.

Alcohol consumption and cardiovascular mortality accounting for possible misclassification of intake: 11-year follow-up of the Melbourne Collaborative Cohort Study.

PubMed

Harriss, Linton R; English, Dallas R; Hopper, John L; Powles, John; Simpson, Julie A; O'Dea, Kerin; Giles, Graham G; Tonkin, Andrew M

2007-10-01

To investigate the relationship between usual daily alcohol intake, beverage type and drinking frequency on cardiovascular (CVD) and coronary heart disease (CHD) mortality, accounting for systematic misclassification of intake. Prospective cohort study with mean follow-up of 11.4 years. Setting The Melbourne Collaborative Cohort Study, Australia. A total of 38 200 volunteers (23 044 women) aged 40-69 years at baseline (1990-1994). Self-reported alcohol intake using beverage-specific quantity-frequency questions (usual intake) and drinking diary for previous week. Compared with life-time abstention, usual daily alcohol intake was associated with lower CVD and CHD mortality risk for women but not men. For women, the hazard ratio [HR (95% CI)] for CVD for those drinking > 20 g/day alcohol was 0.43 (0.19-0.95; P trend = 0.18), and for CHD, 0.19 (0.05-0.82; P trend = 0.24). Male former drinkers had over twice the mortality risk for CVD [HR = 2.58 (1.51-4.41)] and CHD [HR = 2.91 (1.59-5.33)]. Wine was the only beverage associated inversely with mortality for women. Compared with drinkers who consumed no alcohol in the week before baseline, drinking frequency was associated inversely with CVD and CHD mortality risk for men but not women. HR for men drinking 6-7 days/week was 0.49 (0.29-0.81; P trend = 0.02) for CVD, and 0.49 (0.26-0.92: P trend = 0.23) for CHD. Usual daily alcohol intake was associated with reduced CVD and CHD mortality for women but not men. This benefit appeared to be mainly from wine, although comparison of beverages was not possible. Drinking frequency was associated inversely with CVD and CHD death for men but not women.

Oxidative Stress and Inflammation Differentially Elevated in Objective Versus Habitual Subjective Reduced Sleep Duration in Obstructive Sleep Apnea.

PubMed

DeMartino, Theresanne; Ghoul, Rawad El; Wang, Lu; Bena, James; Hazen, Stanley L; Tracy, Russel; Patel, Sanjay R; Auckley, Dennis; Mehra, Reena

2016-07-01

Data have demonstrated adverse health effects of sleep deprivation. We postulate that oxidative stress and systemic inflammation biomarkers will be elevated in relation to short-term and long-term sleep duration reduction. We analyzed data from the baseline examination of a randomized controlled trial involving participants with moderate to severe obstructive sleep apnea (OSA). Baseline polysomnography provided the total sleep time (PSG-TST, primary predictor); self-reported habitual sleep duration (SR-HSD) data was collected. Morning measures of oxidative stress and systemic inflammation included: myeloperoxidase (MPO, pmol/L), oxidized low-density lipoprotein (ox-LDL, U/L), F2-isoprostane (ng/mg), paraoxonase 1 (PON1, nmol·min(-1)·mL(-1)), and aryl esterase (μmol·min(-1)·mL(-1)). Linear models adjusted for age, sex, race, body mass index (BMI), cardiovascular disease (CVD), smoking, statin/anti-inflammatory medications, and apnea-hypopnea index were utilized (beta estimates and 95% confidence intervals). One hundred forty-seven participants comprised the final analytic sample; they were overall middle-aged (51.0 ± 11.7 y), obese (BMI = 37.3 ± 8.1 kg/m(2)), and 17% had CVD. Multivariable models demonstrated a significant inverse association of PSG-TST and MPO (β [95% CI] = -20.28 [-37.48, -3.08], P = 0.021), i.e., 20.3 pmol/L MPO reduction per hour increase PSG-TST. Alternatively, a significant inverse association with ox-LDL and SR-HSD was observed (β [95% CI] = 0.98 [0.96, 0.99], P = 0.027), i.e., 2% ox-LDL reduction per hour increase SR-HSD. Even after consideration of obesity and OSA severity, inverse significant findings were observed such that reduced PSG-TST was associated with elevated MPO levels and SR-HSD with ox-LDL, suggesting differential up-regulation of oxidative stress and pathways of inflammation in acute versus chronic sleep curtailment. NIH clinical trials registry number NCT00607893. © 2016 Associated Professional Sleep Societies, LLC.

Association between a dietary carbohydrate index and cardiovascular disease in the SUN (Seguimiento Universidad de Navarra) Project.

PubMed

Zazpe, I; Santiago, S; Gea, A; Ruiz-Canela, M; Carlos, S; Bes-Rastrollo, M; Martínez-González, M A

2016-11-01

Beyond the quantity of carbohydrate intake, further research is needed to know the relevance of carbohydrate quality following operational indices. No previous longitudinal study has assessed the association between an index for quality of dietary carbohydrate intake and the risk of cardiovascular disease (CVD). Here, we examined the association between a carbohydrate quality index (CQI) and the risk of CVD. We used a validated semi-quantitative 136-item food-frequency questionnaire (FFQ) in a prospective follow-up study of 17,424 middle-aged adults from Spain. The CQI was defined by four criteria: dietary fiber intake, glycemic index, whole-grain/total-grain carbohydrate ratio, and solid/total carbohydrate ratio. We observed 129 incident cases of CVD during 10.1 y of median follow-up. An inverse association for CQI was found (hazard ratio = 0.44, 95% confidence interval (CI): 0.25-0.78 for the highest versus the lowest tertile, p for trend = 0.008). Participants in the highest tertile of the whole-grain/total-grain carbohydrate ratio had 47% lower risk of CVD (95% CI: 0.33-0.85, p for trend = 0.008). Participants with higher baseline CQI and higher baseline energy from carbohydrates had the lowest risk of CVD. In this Mediterranean cohort, a better quality of dietary carbohydrates measured by the CQI, showed a significant inverse association with the incidence of CVD. Specially, a higher proportion of carbohydrates from whole grains was strongly inversely associated with CVD. "Heart-healthy" diets should be focused not only on carbohydrate quantity but also on a multidimensional assessment of the type and quality of carbohydrates. Copyright © 2016 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.

Stroke With Unknown Time of Symptom Onset: Baseline Clinical and Magnetic Resonance Imaging Data of the First Thousand Patients in WAKE-UP (Efficacy and Safety of MRI-Based Thrombolysis in Wake-Up Stroke: A Randomized, Doubleblind, Placebo-Controlled Trial).

PubMed

Thomalla, Götz; Boutitie, Florent; Fiebach, Jochen B; Simonsen, Claus Z; Nighoghossian, Norbert; Pedraza, Salvador; Lemmens, Robin; Roy, Pascal; Muir, Keith W; Ebinger, Martin; Ford, Ian; Cheng, Bastian; Galinovic, Ivana; Cho, Tae-Hee; Puig, Josep; Thijs, Vincent; Endres, Matthias; Fiehler, Jens; Gerloff, Christian

2017-03-01

We describe clinical and magnetic resonance imaging (MRI) characteristics of stroke patients with unknown time of symptom onset potentially eligible for thrombolysis from a large prospective cohort. We analyzed baseline data from WAKE-UP (Efficacy and Safety of MRI-Based Thrombolysis in Wake-Up Stroke: A Randomized, Doubleblind, Placebo-Controlled Trial), an investigator-initiated, randomized, placebo-controlled trial of MRI-based thrombolysis in stroke patients with unknown time of symptom onset. MRI judgment included assessment of the mismatch between visibility of the acute ischemic lesion on diffusion-weighted imaging and fluid-attenuated inversion recovery. Of 1005 patients included, diffusion-weighted imaging and fluid-attenuated inversion recovery mismatch was present in 479 patients (48.0%). Patients with daytime-unwitnessed stroke (n=138, 13.7%) had a shorter delay between symptom recognition and hospital arrival (1.5 versus 1.8 hours; P =0.002), a higher National Institutes of Stroke Scale score on admission (8 versus 6; P <0.001), and more often aphasia (72.5% versus 34.0%; P <0.001) when compared with stroke patients waking up from nighttime sleep. Frequency of diffusion-weighted imaging and fluid-attenuated inversion recovery mismatch was comparable between both groups (43.7% versus 48.7%; P =0.30). Almost half of the patients with unknown time of symptom onset stroke otherwise eligible for thrombolysis had MRI findings making them likely to be within a time window for safe and effective thrombolysis. Patients with daytime onset unwitnessed stroke differ from wake-up stroke patients with regards to clinical characteristics but are comparable in terms of MRI characteristics of lesion age. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01525290. URL: https://www.clinicaltrialsregister.eu. Unique identifier: 2011-005906-32. © 2017 American Heart Association, Inc.

RadioAstron Observations of the Quasar 3C273: A Challenge to the Brightness Temperature Limit

NASA Astrophysics Data System (ADS)

Kovalev, Y. Y.; Kardashev, N. S.; Kellermann, K. I.; Lobanov, A. P.; Johnson, M. D.; Gurvits, L. I.; Voitsik, P. A.; Zensus, J. A.; Anderson, J. M.; Bach, U.; Jauncey, D. L.; Ghigo, F.; Ghosh, T.; Kraus, A.; Kovalev, Yu. A.; Lisakov, M. M.; Petrov, L. Yu.; Romney, J. D.; Salter, C. J.; Sokolovsky, K. V.

2016-03-01

Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of 1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI) at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as small as 26 μas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive black holes and require a much higher Doppler factor than what is determined from jet apparent kinematics.

Improved Measurement of Reactor Flux and Spectrum at Daya Bay

NASA Astrophysics Data System (ADS)

Zhan, Liang; Daya Bay Collaboration

2017-09-01

A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay experiment is reported. With a live time of 621 days, more than 1.2 million inverse beta decay (IBD) candidates were collected by eight antineutrino detectors (ADs) deployed in two near (560 m and 600 m flux-weighted baselines) and one far (16400 m flux-weighted baseline) underground experimental halls. The IBD yield was measured and the ratio to the predicted flux using the Huber+Mueller (ILL+Vogel) model was determined to be 0.946 ± 0.020 (0.992 ± 0.021). A 2.9 σ deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4-6 MeV was found with a local significance of 4.4 σ.