bluuebunny/crossref_metadata_2025 huggingface dataset:
An LMI-Based Hedging Approach to Model Reference Adaptive Control With Actuator Dynamics
Authors: Gruenwald Benjamin C. , Wagner Daniel , Yucelen Tansel , Muse Jonathan A.
Published: January 2016

Although model reference adaptive control has been used in numerous applications to achieve system performance without excessive reliance on dynamical system models, the presence of actuator dynamics can seriously limit the stability and the achievable performance of adaptive controllers. In this paper, an linear matrix inequalities-based hedging approach is developed and evaluated for model reference adaptive control of uncertain dynamical systems in the presence of actuator dynamics. The hedging method modifies the ideal reference model dynamics in order to allow correct adaptation that does not get affected due to the presence of actuator dynamics. Specifically, we first generalize the hedging approach to cover cases in which actuator output and is known and unknown. We next show the stability of the closed-loop dynamical system using tools from Lyapunov stability and linear matrix inequalities. Finally, an illustrative numerical example is provided to demonstrate the efficacy of the proposed linear matrix-inequalities-based hedging approach to model reference adaptive control.
Robust-Optimal Fuzzy Model-Based Control of Flexible Spacecraft With Actuator Amplitude and Rate Constraints
Authors: Sendi Chokri , Ayoubi Mohammad A.
Published: January 2016

This paper presents a robust-optimal fuzzy controller for position and attitude stabilization, and vibration suppression of a flexible spacecraft during antenna retargeting maneuver. The fuzzy controller is based on Takagi-Sugeno (T-S) fuzzy model and uses the dynamic parallel distributed compensator (DPDC) technique to quadratically stabilize the closed-loop system. The proposed controller is robust to parameter and unstructured uncertainties of the model. We improve the performance and the efficiency of the controller by minimizing the upper bound of the actuators amplitude and rate, and maximizing the uncertainties terms included in the T-S fuzzy model. In addition to actuator amplitude and rate constraints, a fuzzy model-based observer is considered for estimating unmeasurable states. Using Lyapunov stability theory and linear matrix inequalities (LMIs), we formulate the problem of designing an optimal-robust fuzzy controller/observer with actuator amplitude and rate constraints as a convex optimization problem. Numerical simulation is provided to demonstrate and compare the stability, performance, and robustness of the proposed fuzzy controller with a baseline nonlinear controller.
Hierarchical Control of Multi-Domain Power Flow in Mobile Systems: Part II — Aircraft Application
Authors: Williams Matthew A. , Koeln Justin P. , Alleyne Andrew G.
Published: January 2016

This two-part paper presents the development of a hierarchical control framework for the control of power flow throughout large-scale systems. Part II presents the application of the graph-based modeling framework and three-level hierarchical control framework to the power systems of an aircraft. The simplified aircraft system includes an engine, electrical, and thermal systems. A graph based approach is used to model the system dynamics, where vertices represent capacitive elements such as fuel tanks, heat exchangers, and batteries with states corresponding to the temperature and state of charge. Edges represent power flows in the form of electricity and heat, which can be actuated using control inputs. The aircraft graph is then partitioned spatially into systems and subsystems, and temporally into fast, medium, and slow dynamics. These partitioned graphs are used to develop models for each of the three levels of the hierarchy. Simulation results show the benefits of hierarchical control compared to a centralized control method.
Hierarchical Control of Multi-Domain Power Flow in Mobile Systems: Part I — Framework Development and Demonstration
Authors: Koeln Justin P. , Williams Matthew A. , Alleyne Andrew G.
Published: January 2016

This two-part paper presents the development of a hierarchical control framework for the control of power flow throughout mobile systems. These vehicles are comprised of multiple interconnected systems each with multiple subsystems which exhibit dynamics over a wide range of timescales. These interconnections and the timescale separation pose a significant challenge when developing an effective control strategy. Part I presents the proposed graph-based modeling approach and the three-level hierarchical control framework developed to directly address these interconnections and timescale separation. The mobile system is represented as a directed graph with vertices corresponding to the states of the vehicle and edges capturing the power flow throughout the vehicle. The mobile system and the corresponding graph are partitioned spatially into systems and subsystems and temporally into vertices of slow, medium, and fast dynamics. The partitioning facilitates the development of models used by model predictive controllers at each level of the hierarchy. A simple example system is used to demonstrate the approach. Part II utilizes this framework to control the power flow in the electrical and thermal systems of an aircraft. Simulation results show the benefits of hierarchical control compared to centralized and decentralized control methods.
Observer-Based Diagnostic Scheme for Lithium-Ion Batteries
Authors: Abdollahi Biron Zoleikha , Pisu Pierluigi , Ayalew Beshah
Published: January 2016

This paper presents an observer-based fault diagnosis approach for Lithium-ion batteries. This method detects and isolates five fault types, which include sensor faults in current, voltage and temperature sensors, failure in fan actuator and a fault in battery State-of-Charge (SOC) dynamics. Current, voltage and temperature of the battery are taken as the only available measurements and a Kalman filter and a sliding mode observer are constructed. Three residuals derived from a combination of these observers generate fault signatures that are used to detect and isolate the sensor, actuator and SOC faults in the system. Simulation results show the effectiveness of the approach.
Analysis and Passive Control of a Four-Bar Linkage for the Rehabilitation of Upper-Limb Motion
Authors: Xydas Evagoras G. , Louca Loucas S. , Mueller Andreas
Published: January 2016

In the last two decades robotic rehabilitation research provided significant insight regarding the human-robot interaction, helped understand the process by which the impaired nervous system is retrained to better control movements, and led to the development of a number of mathematical and neurophysiological models that describe both the human motion and the robot control. The human-machine interaction in this research is typically achieved through robotic devices that are based on open kinematic chains. These devices have multiple degrees of freedom (DOF), sophisticated computer control, actuation and sensing. The flexibility of such approach enables the easy implementation of the various models and methods that have to be applied in order to maximize the potential of robotic rehabilitation.

On the other hand, mechanisms with fewer DOF’s that are based on closed kinematic chains can generate specific, yet adequate trajectories for the purposes of robotic rehabilitation. An example of such mechanisms is four-bar linkages that have only 1-DOF but yet can generate paths with complex kinematic characteristics. Design and analysis of four-bar linkages is used to achieve a variety of kinematics in terms of trajectory, velocity and acceleration profiles. The simplicity of these mechanisms is appealing and they can be used in rehabilitation due to their ability to replicate the motion of various human joints and limbs. The focus of the current work is to study the use of a four-bar linkage for generating the natural motion of upper-limb reaching tasks with the intention of using this mechanism for rehabilitation. This natural hand motion is described by a straight-line trajectory with a smooth bellshaped velocity profile, which in turn is generated by the well-established Minimum Jerk Model (MJM). The goal is to design passive control elements in a four-bar linkage that generate the required torque for producing the MJM motion. The passive elements are two linear translational springs that act on the driving link of a straight line generating mechanism. A design optimization is used to minimize the difference between the desired and actual input spring torque while remaining within the predefined design space. The final arrangement is simulated in a Multibody Dynamics software that applies feed-forward dynamics to generate the mechanism’s free response to the torque generated by the designed linear springs.

The results of this work suggest that systematic design of a four-bar linkage can lead to simple mechanisms that can replicate the natural motion of reaching tasks. Relatively inexpensive linear springs can be employed in the design of passive-active controlled therapeutic mechanisms. Further investigation that combines analysis of both active and passive control/actuation elements must be performed for finalizing the control design. Simulations and analysis that incorporate various impaired hand responses must be also performed in order to finalize the design.
Orientation Control Using Oscillating Momentum Wheels
Authors: Wang Shaoqian , Ghasemi Amir H. , Evans Joshua L. , Seigler T. Michael
Published: January 2016

This paper addresses the problem of controlling a rigid body’s orientation by actuating sinusoidal oscillations of internal momentum wheels. We consider the rotational dynamics of a rigid body having three momentum wheels (one for each body-fixed axis) that are attached to the body by springs. Each wheel is actuated by an internal sinusoidal torque of fixed frequency. The frequency of all sinusoidal torques is equal, but the amplitudes and phases can be varied independently. We analyze the inverse-dynamics problem of determining the amplitudes and phases for each sinusoidal torque such that a desired orientation is achieved. We then present two closed-loop orientation controllers based on this analysis. Numerical simulations demonstrate the effectiveness of the control techniques.
Extended Kalman Filter Based Quadrotor State Estimation Based on Asynchronous Multisensor Data
Authors: Sarim Mohammad , Nemati Alireza , Kumar Manish , Cohen Kelly
Published: January 2016

For effective navigation and tracking applications involving Unmanned Aerial Vehicles (UAVs), data fusion from multiple sensors is utilized. However, asynchronous nature of the sensors, coupled with loss of data and communication delays, makes this process not very reliable. For a better estimation of the data, some sort of filtering scheme is needed. This paper presents an Extended Kalman Filter (EKF) based quadrotor state estimation by exploiting the dynamic model of the UAV. The data coming from the sensors is noisy and intermittent. The EKF filters and provides estimated data for the missing timestamps. An indoor flight test establishes the accuracy of the EKF, and another outdoor flight test validates the developed scheme for the real world scenario.
A Hardware-in-the-Loop Strategy for Control of a Wind Turbine Test Bench
Authors: Schkoda Ryan , Bibo Amin
Published: January 2016

This paper presents a strategy for operating and simulating a full scale wind turbine test bench in order to emulate the field conditions experienced by the mechanical portion of a nacelle’s drivetrain. The presented strategy makes use of a real-time simulation of a wind turbine model to provide reference signals for the test bench. These reference signals include the thrust force, lateral force, vertical force, pitch moment, yaw moment, and drivetrain speed at the nacelle’s control point or hub point: a point along a nacelle’s drivetrain representing what would be the center of the nacelle hub. The effectiveness of this approach is studied with the help of a multibody, dynamic model of the 7.5 MW test bench located at Clemson University’s Wind Turbine Drivetrain Testing Facility. Simulation results show that the proposed control strategy is feasible for emulating field conditions on a wind turbine test bench.
Anchorless Design of Electromagnetic Vibration Energy Harvester for Railroad
Authors: Lin Teng , Wang Lirong , Zuo Lei
Published: January 2016

An electromagnetic energy harvester features anchorless mounting is designed and analyzed. It can harness electrical energy from railroad track deflections induced by passing trains. Anchorless mounting is designed to be easily installed on railroad sleepers without any change to the original foundation, it utilize a spring reset mechanism to capture track motion. This structure eliminates the need of anchoring on the railroad and further reduces any potential risk to change the railroad construction. An energy harvesting mechanism named mechanical motion rectifier (MMR) is created to overcome challenge in harnessing energy from the high pulse-like impact and to transform bidirectional linear vibration into unidirectional rotational motion at high efficiency. Dynamic modeling of MMR and harvester are developed to reveal the working principle and verify overall design. The harvester is targeting at powering major track-side accessories or to be used as back-up power source to enhance track operational safety.
Wiener Modeling of a Closed Loop Vapor Compression System for Extremum Seeking Controller Design
Authors: Keating Bryan , Koeln Justin , Alleyne Andrew
Published: January 2016

This paper demonstrates that the dynamic relationship between the power consumption of a vapor compression system under closed loop control and its evaporator and condenser fan inputs is well described about a nominal operating point by a Wiener model, which is useful for extremum seeking controller design. Information about the input dynamics from the Wiener model is used to evaluate the tradeoff between steady-state error and convergence time for single and dual input extremum seeking controllers in simulation.
Performance Evaluation of a Sensorized Arthroscopic Grasper
Authors: Poursartip Behnaz , Yurkewich Daniel , LeBel Marie-Eve , Patel Rajni V. , Trejos Ana Luisa , Naish Michael D.
Published: January 2016

Force sensing minimally invasive instruments have gained increasing attention in recent years. Integrating these instruments within currently available surgical simulators can enhance the learning experience by measuring the forces applied by trainees and supplementing objective performance assessment. Recently, an arthroscopic grasper was designed and sensorized with Fiber Bragg Grating Sensors at Canadian Surgical Technologies and Advanced Robotics (CSTAR). Moreover, a custom low-cost (LC) interrogation system was developed to accompany the proposed sensorized tool. In this study, the custom LC interrogator was used and compared to the commercially-available Micron Optics sm130 (MO) interrogator. The hypothesis is that both of these systems can be used to measure forces within ±0.5 N as the acceptable margin for accuracy. Experimental results showed that the MO system meets the required accuracy for certain force directions. The LC system demonstrated 49% of the accuracy of the MO interrogator. The main advantage of the LC interrogator is its cost, which is 18% of the commercial interrogation system. For certain force directions, the performance was comparable to the defined criteria.
MPC-Based Energy Management of a Parallel Hybrid Electric Vehicle Using Terrain Information
Authors: Wahba Mohamed , Brennan Sean
Published: January 2016

A parallel hybrid electric vehicle (HEV) combines the power produced by electric machines and a combustion engine to enable improved fuel economy. Optimization of the power-split algorithm managing both torque sources can be readily achieved offline, but online implementation results often show great deviation from expected fuel economy due to traffic, hills, and similar effects that are not easily modeled. Of these external influences, the road grade for a travel route is potentially known a priori given a set destination choice from the driver. To examine whether grade information can improve the performance of a hybrid powertrain controller, we first formulate the vehicle model as a low-order dynamic model, recognizing that the primary dynamics of the energy system are slow. A model predictive control (MPC) strategy utilizing the terrain data is then developed to obtain a time-varying power split between the combustion engine and the electrical machine. Simulation results of the HEV model over multiple standard drive cycles, with different terrain profiles and different cost functions, are presented. Testing of the MPC performance compared to Argonne National Lab’s powertrain simulation software Autonomie shows that the MPC strategy utilizing terrain data gives an improvement of up to 2.2% in fuel economy with respect to the same controller without terrain information, on the same route.
Dynamic Modeling and Analysis for Thin-Wall Plate Machining
Authors: Guo Jiajie , Liu Ruochu , Lee Kok-Meng
Published: January 2016

Complex thin-wall component machining has been a challenging task in advanced manufacturing because distributed deformation and vibration of workpiece render poor precision in final products, which requires displacement field measurements for vibration compensation techniques to enhance product quality. It is desired to capture the distributed and dynamic characteristics of workpiece during the machining of thin-wall plates. In the context of an engineering application where an annular compressor disk is lathe-turned on a duplex machine, this paper has developed an analytical method to capture the effects of stepped thickness on the thin-wall plate dynamics, where the stepped shape emulates the geometry of a workpiece under machining. Modal natural frequencies characterizing varying inertia and stiffness are obtained via a formulated boundary value problem, upon which the effects of cutting tool positions on the frequencies and mode shapes are analyzed. It also provides numerical verification with finite element analysis and validation with experiment.
Torsional Vibrations in the Drivetrain of DFIG- and PMG-Based Wind Turbines: Comparison and Mitigation
Authors: Fateh Fariba , White Warren N. , Gruenbacher Don
Published: January 2016

In this paper, torsional vibrations in a five-mass drivetrain of a doubly fed induction generator (DFIG)-based and a permanent magnet generator (PMG)-based wind turbine are investigated through simulations. The simulated model includes aerodynamics of a 750kW wind turbine, as well as the dynamics of the generator, gearbox, and back-to-back power converters. In this study, the effectiveness of a sliding mode based control scheme to damp the drivetrain torsional vibrations for the events of a voltage dip occurring on the power grid and a wind speed variation is presented. The simulation results demonstrate mechanical disturbances have similar impacts on the drivetrain of DFIG-based and PMG-based wind turbines. However, the back-to-back converters in a PMG-based wind turbine effectively isolate the effects of power oscillations on the drivetrain.
Assessment of Human Vulnerability in a Touch-Screen Game; Metrics and Analysis
Authors: Parsinejad Payam , Sipahi Rifat
Published: January 2016

Assistive machine design based on human physiological measurements offers variety of opportunities in both civilian and military applications. In such settings the machine would need to compute certain metrics associated with these measurements to decide how to assist the humans. In this paper, we study a set of metrics pertaining to human behavioral patterns in easy and difficult tasks taken on a touch screen computer game. Analysis of these metrics reveal that some of them can be utilized as indicators of task difficulty showing promise for their use by machines. The metric results are also compared with task performance metrics, as well as a reliable and established metric called pNN50 calculated from subjects’ heart rate measurements and serving as the baseline.
A Finger-Motion Adaptive Algorithm for Braille Reading: Application of Active Disturbance Rejection Control
Authors: Ulusoy Melda , Sipahi Rifat
Published: January 2016

Currently existing refreshable Braille displays suffer from high costs, which prevent their affordability. A rotating wheel with refreshable Braille and utilizing finger-motion adaptation can help create realistic Braille reading experience, while significantly reducing the high costs by offsetting the number of actuators needed to display Braille. In this paper, we design a real-time controller to adjust the speed of the rotating wheel system based on the finger motions of the user. Due to unknown dynamics of the rotating wheel system, active disturbance rejection control (ADRC) has been implemented to estimate the total disturbance acting on the system. This estimate is then used to eliminate the internal disturbance of the system so that disturbances associated with finger touch on the wheel can be predicted. Real-time experimental results show that even without the knowledge of the system model, it is possible to adapt the speed of the rotating wheel based on these finger touch predictions.
Natural Gas Hydrogen Reformer Controller Design With Disturbance Rejection
Authors: Radisavljevic-Gajic Verica , Rose Patrick
Published: January 2016

In this paper we present a controller design for a linearized model of a fuel cell hydrogen gas reformer, which produces hydrogen from natural gas. We design two feedback control loops, one of them with an integrator and another one with proportional state feedback. In the third step, a feed-forward controller is designed whose role is to off-set for the impact of the disturbance represented by the fuel cell current. Both the feedback controller and the feedforward controller are obtained through a rigorous dynamic optimization process of a quadratic performance criterion along trajectories of a linear dynamic system. According to the presented simulation results, the proposed controller copes well with the disturbance and reduces its impact within a few seconds from the time when the disturbance occurs, despite large jumps in the fuel cell current (disturbance).
Stabilization of Inverted Pendulum on a Cart in the Presence of Uncertainties
Authors: Lee Joonho , Choi Jongeun
Published: January 2016

This paper presents an output feedback control design to stabilize the inverted pendulum at the upright equilibrium as an extension of our previous work [1]. Compared to our previous work, we add one more time scale between a pendulum angle and angular velocity to reduce a traveled distance of the cart. State feedback control is designed to enable the pendulum to pass through input singularity configurations. Extended High-Gain Observers are used to estimate velocity and acceleration terms while dynamic inversion utilizes the estimates to deal with input coefficient uncertainties and singularity configurations. The proposed control is verified through numerical simulations.
Optimal Feedback Control of a Flexible Needle Under Anatomical Motion Uncertainty
Authors: Sovizi Javad , Kumar Suren , Krovi Venkat
Published: January 2016

Bevel-tip flexible needles allow for reaching remote/inaccessible organs while avoiding the obstacles (sensitive organs, bones, etc.). Motion planning and control of such systems is a challenging problem due to the uncertainty induced by needle-tissue interactions, anatomical motions (respiratory and cardiac induced motions), imperfect actuation, etc. In this paper, we use an analogy where steering the needle in a soft tissue subject to the uncertain anatomical motions is compared to the Dubins vehicle traveling in the stochastic wind field. Achieving the optimal feedback control policy requires solution of a dynamic programming problem that is often computationally demanding. Efficiency is not central to many optimal control algorithms that often need to be computed only once for a given system/noise statistics. However, intraoperative policy updates may be required for adaptive or patient-specific models. We use the method of approximating Markov chain to approximate the continuous (and controlled) process with its discrete and locally consistent counterpart. We examine the linear programming method of solving the imposed dynamic programming problem that significantly improves the computational efficiency in comparison to the state-of-the-art approaches. In addition, the probability of success and failure are simply the variables of the linear optimization problem and can be directly used for different objective definitions. A numerical example of the 2D needle steering problem is considered to investigate the effectiveness of the proposed method.
Proportional sEMG Based Robotic Assistance in an Isolated Wrist Movement
Authors: Artz Edward J. , Blank Amy A. , O’Malley Marcia K.
Published: January 2016

Numerous studies have demonstrated the efficacy of robots for motor therapy. Surface electromyography (sEMG) is appealing for user intent detection as the signal relates the individual’s desired muscle contractile force. A drawback to sEMG interfaces is subject- and session-dependent calibration. We sought to investigate the effect of a simple sEMG assistive controller on user performance in the MAHI Exo-II, therapeutic exoskeleton. Agonist-antagonist muscles were related after normalization based on sub-maximal isometric contraction. Six subjects performed a target tracking task with four levels of assistance in wrist flexion-extension. Performance metrics were mean absolute position error and estimated muscular activity. In low levels of assistance, subject performance was not significantly affected, while increasing the assistance resulted in higher position errors. In characterizing the performance assistance trade-off, we better understand the capabilities of this simple controller. This investigation validates the feasibility of using a proportional control scheme for a therapeutic wrist exoskeleton system and motivates further testing with impaired subjects to optimize the system for use in a clinical setting.
A Nonlinear Tension Control Scheme for Web Transport Through Heating Processes
Authors: Lu Youwei , Pagilla Prabhakar R.
Published: January 2016

In this paper we develop a model-based nonlinear tension control scheme for transport of flexible materials (webs) through heating processes. Heat transfer processes are widely employed in Roll-to-Roll (R2R) process machines that are used to perform processing operations on a moving web on rollers. Heat transfer processes induce thermal expansion/contraction of the flexible material during transport. Because web strain and elastic modulus are functions of temperature distribution in the web, web tension resulting from elastic strain is affected by heating/cooling of the web. Based on a web tension governing equation that includes both elastic and thermal effects, a nonlinear tension control scheme is developed for control of tension in each tension zone of an R2R system. The control scheme is implemented on an R2R experimental platform containing two heat transfer rollers, one for heating the web and one for subsequently cooling the web prior to winding of the web. Experimental results are presented and discussed.
A New, Necessary and Sufficient Vertex Solution for Robust Stability Check of Unstructured Convex Combination Matrix Families
Authors: Yedavalli Rama K.
Published: January 2016

This paper revisits the problem of checking the robust stability of matrix families generated by ‘Unstructured Convex Combinations’ of user supplied or externally supplied Vertex Matrices. A previous solution given by the author for this problem involved complete dependence on the quantitative (eigenvalue information) of a set of special matrices labeled the Kronecker Nonsingularity (KN) matrices. In this solution, the ‘convexity’ property is not explicit and transparent, to the extent that, unfortunately, the accuracy of the solution itself is being questioned and not embraced by the peer community. To erase this unforunate and unwarranted image of this author (in this specific problem) in the minds of the peer community, in this paper, the author treads a new path to find a solution that brings out the convexity property in an explicit and understandable way. In the new solution presented in this paper, we combine the qualitative (sign) as well as quantitative (magnitude) information of these KN matrices and present a vertex solution in which the convexity property of the solution is transparent making it more elegant and accepatble to the peer community, than the previous solution. The new solution clearly underscores the importance of using the sign structure of a matrix in assessing the stability of a matrix. This new solution is made possible by the new insight provided by the qualitative (sign) stability/instability derived from ecological principles. Examples are given which clearly demonstrate effectiveness of the new, convexity based algorithm. It is hoped that this new solution will be embraced by the peer community.
Novel heart valve prosthesis with self-endothelialization potential made of modified polyhedral oligomeric silsesquioxane-nanocomposite material
Authors: Ghanbari Hossein , Radenkovic Dina , Marashi Sayed Mahdi , Parsno Shirin , Roohpour Nima , Burriesci Gaetano , Seifalian Alexander M.
Published: January 2016

In the cardiovascular system, the endothelial layer provides a natural antithrombogenic surface on the inner portion of the heart and associated vessels. For a synthetic material therefore, the ability to attract and retain endothelial or endothelial progenitor cells (EPCs), ultimately creating a single endothelial layer on its surface, is of prime importance. The authors have developed a nanocomposite polymer, based on a combination of polyhedral oligomeric silsesquioxane nanoparticles and polycarbonate urea urethane (POSS-PCU), which is biocompatible and has been used in human for the world's first synthetic trachea, tear duct, and bypass graft. In this study, the authors modified the surface of this casted nanocomposite by grafting fibronectin derived bioactive peptides [glycine-arginine-glycine-aspartic acid-glycine (GRGDG) and lauric acid conjugated GRGDG (GRGDG-LA)] to enhance the endothelialization for using heart valves leaflets from circulating EPCs. Human peripheral blood mononuclear cells were separated using Ficoll–Paque centrifugation, with harvested EPCs purified using CD34 microbead labeling and magnetic-activated cell sorting. Cells were seeded onto 96 well plates coated with POSS-PCU, GRGDG/GRGDG-LA modified POSS-PCU and PCU polymers, for a period of 21 days. Cells were studied under light, confocal, and scanning electron microscope (SEM). Fluorescence-activated cell sorting was used to analyze cell surface markers. Cell attachment and proliferation was observed in all POSS-PCU samples, significantly higher than the activity seen within the control PCU polymers (p < 0.05). Microscopic examination revealed clonal expansion and morphological changes in cells seeded on POSS-PCU. The cells expressed increasing levels of mature endothelial cell markers over time with a concurrent reduction in hematopoietic stem cell marker expression. SEM showed a mixed population of morphologically differentiated endothelial cells and EPCs. These results support the use of heart valve made with the POSS-PCU polymer and demonstrate that suitable chemical modification of this nanocomposite could increase self-endothelialization potential and reduce associated thrombotic events.
Secondary ion emission from leucine and isoleucine under argon gas-cluster ion bombardment
Authors: Gnaser Hubert , Kusakari Masakazu , Fujii Makiko , Seki Toshio , Aoki Takaaki , Matsuo Jiro
Published: January 2016

The emission of sputtered ions from isoleucine and leucine specimens under bombardment by 10 keV argon gas-cluster ions Ar1000+ was investigated by orthogonal time-of-flight secondary ion mass spectrometry, in an attempt to examine the possibility of discriminating these amino acids by means of specific differences in their mass spectra. Apart from of the protonated molecular ions (M+H)+ a prolific flux of singly charged and doubly charged molecular cluster ions, (Mn+H)+ (1 ≤ n ≤ 15) and (Mn+2H)2+ (8 ≤ n ≤ 29) was observed. The distributions of the cluster yields Yn as a function of their size n were found to be very similar for both amino acids. In addition, the fraction of emitted fragment and other ion species is typically low, and no distinct differences were detected for isoleucine and leucine. Therefore, the present data seem to indicate that a discrimination of isoleucine and leucine via mass spectrometric means is not possible.
A multimodal spectral approach to characterize rhythm in natural speech
Authors: Alexandrou Anna Maria , Saarinen Timo , Kujala Jan , Salmelin Riitta
Published: January 2016

Human utterances demonstrate temporal patterning, also referred to as rhythm. While simple oromotor behaviors (e.g., chewing) feature a salient periodical structure, conversational speech displays a time-varying quasi-rhythmic pattern. Quantification of periodicity in speech is challenging. Unimodal spectral approaches have highlighted rhythmic aspects of speech. However, speech is a complex multimodal phenomenon that arises from the interplay of articulatory, respiratory, and vocal systems. The present study addressed the question of whether a multimodal spectral approach, in the form of coherence analysis between electromyographic (EMG) and acoustic signals, would allow one to characterize rhythm in natural speech more efficiently than a unimodal analysis. The main experimental task consisted of speech production at three speaking rates; a simple oromotor task served as control. The EMG–acoustic coherence emerged as a sensitive means of tracking speech rhythm, whereas spectral analysis of either EMG or acoustic amplitude envelope alone was less informative. Coherence metrics seem to distinguish and highlight rhythmic structure in natural speech.
Vibroacoustics of orthotropic plates ribbed in both directions: Application to stiffened rectangular wood panels
Authors: Trévisan Benjamin , Ege Kerem , Laulagnet Bernard
Published: January 2016

This paper is focused on the vibroacoustic behavior of a rectangular ribbed wood panel. This is done by developing an analytical model based on a variational approach, taking into account the kinetic and strain energies of a special orthotropic plate, 11 ribs oriented in a first direction and 1 other strong stiffener oriented in the perpendicular direction, which are considered as beams tied to the plate. A modal decomposition is adopted on the basis of the simply supported orthotropic plate. This allows calculating the modes of the wood panel (ribbed modes) in the frequency range 0–5000 Hz. The acoustical radiation of the baffled panel is also calculated. The radiation coefficients of the ribbed modes are presented and compared, when possible, to similar unribbed plate modes. Finally, the vibroacoustic analysis of the structure shows that an excitation placed on the hard point makes the panel particularly radiative and decreases the apparent critical frequency.
The Human Disease-Associated Aβ Amyloid Core Sequence Forms Functional Amyloids in a Fungal Adhesin
Authors: Rameau Rachele D. , Jackson Desmond N. , Beaussart Audrey , Dufrêne Yves F. , Lipke Peter N.
Published: January 2016

There is increasing evidence that many amyloids in living cells have physiological functions. On the surfaces of fungal cells, amyloid core sequences in adhesins can aggregate into 100- to 1,000-nm-wide patches to form high-avidity adhesion nanodomains on the cell surface. The nanodomains form through interactions that have amyloid-like properties: binding of amyloid dyes, perturbation by antiamyloid agents, and interaction with homologous sequences. To test whether these functional interactions are mediated by typical amyloid interactions, we substituted an amyloid core sequence, LVFFA, from human Aβ protein for the native sequence IVIVA in the 1,419-residue
Candida albicans
adhesin Als5p. The chimeric protein formed cell surface nanodomains and mediated cellular aggregation. The native sequence and chimeric adhesins responded similarly to the amyloid dye thioflavin T and to amyloid perturbants. However, unlike the native protein, the nanodomains formed by the chimeric protein were not force activated and formed less-robust aggregates under flow. These results showed the similarity of amyloid interactions in the amyloid core sequences of native Als5p and Aβ, but they also highlighted emergent properties of the native sequence. Also, a peptide composed of the Aβ amyloid sequence flanked by amino acids from the adhesin formed two-dimensional sheets with sizes similar to the cell surface patches of the adhesins. These results inform an initial model for the structure of fungal cell surface amyloid nanodomains.

IMPORTANCE
Protein amyloid aggregates are markers of neurodegenerative diseases such as Alzheimer’s and Parkinsonism. Nevertheless, there are also functional amyloids, including biofilm-associated amyloids in bacteria and fungi. In fungi, glycoprotein adhesins aggregate into cell surface patches through amyloid-like interactions, and the adhesin clustering strengthens cell-cell binding. These fungal surface amyloid nanodomains mediate biofilm persistence under flow, and they also moderate host inflammatory responses in fungal infections. To determine whether the amyloid-like properties of fungal surface nanodomains are sequence specific, we ask whether a disease-associated amyloid core sequence has properties equivalent to those of the native sequence in a fungal adhesin. A chimeric adhesin with an amyloid sequence from the Alzheimer’s disease protein Aβ instead of its native sequence effectively clustered the adhesins on the cell surface, but it showed a different response to hydrodynamic shear. These results begin an analysis of the sequence dependence for newly discovered activities for fungal surface amyloid nanodomains.
Analysis of the Protein Kinase A-Regulated Proteome of Cryptococcus neoformans Identifies a Role for the Ubiquitin-Proteasome Pathway in Capsule Formation
Authors: Geddes J. M. H. , Caza M. , Croll D. , Stoynov N. , Foster L. J. , Kronstad J. W.
Published: January 2016

The opportunistic fungal pathogen
Cryptococcus neoformans
causes life-threatening meningitis in immunocompromised individuals. The expression of virulence factors, including capsule and melanin, is in part regulated by the cyclic-AMP/protein kinase A (cAMP/PKA) signal transduction pathway. In this study, we investigated the influence of PKA on the composition of the intracellular proteome to obtain a comprehensive understanding of the regulation that underpins virulence. Through quantitative proteomics, enrichment and bioinformatic analyses, and an interactome study, we uncovered a pattern of PKA regulation for proteins associated with translation, the proteasome, metabolism, amino acid biosynthesis, and virulence-related functions. PKA regulation of the ubiquitin-proteasome pathway in
C. neoformans
showed a striking parallel with connections between PKA and protein degradation in chronic neurodegenerative disorders and other human diseases. Further investigation of proteasome function with the inhibitor bortezomib revealed an impact on capsule production as well as hypersusceptibility for strains with altered expression or activity of PKA. Parallel studies with tunicamycin also linked endoplasmic reticulum stress with capsule production and PKA. Taken together, the data suggest a model whereby expression of PKA regulatory and catalytic subunits and the activation of PKA influence proteostasis and the function of the endoplasmic reticulum to control the elaboration of the polysaccharide capsule. Overall, this study revealed both broad and conserved influences of the cAMP/PKA pathway on the proteome and identified proteostasis as a potential therapeutic target for the treatment of cryptococcosis.

IMPORTANCE
Fungi cause life-threatening diseases, but very few drugs are available to effectively treat fungal infections. The pathogenic fungus
Cryptococcus neoformans
causes a substantial global burden of life-threatening meningitis in patients suffering from HIV/AIDS. An understanding of the mechanisms by which fungi deploy virulence factors to cause disease is critical for developing new therapeutic approaches. We employed a quantitative proteomic approach to define the changes in the protein complement that occur upon modulating the cAMP signaling pathway that regulates virulence in
C. neoformans
. This approach identified a conserved role for cAMP signaling in the regulation of the ubiquitin-proteasome pathway and revealed a link between this pathway and elaboration of a major virulence determinant, the polysaccharide capsule. Targeting the ubiquitin-proteasome pathway opens new therapeutic options for the treatment of cryptococcosis.
Herpesviral ICP0 Protein Promotes Two Waves of Heterochromatin Removal on an Early Viral Promoter during Lytic Infection
Authors: Lee Jennifer S. , Raja Priya , Knipe David M.
Published: January 2016

Herpesviruses must contend with host cell epigenetic silencing responses acting on their genomes upon entry into the host cell nucleus. In this study, we confirmed that unchromatinized herpes simplex virus 1 (HSV-1) genomes enter primary human foreskin fibroblasts and are rapidly subjected to assembly of nucleosomes and association with repressive heterochromatin modifications such as histone 3 (H3) lysine 9-trimethylation (H3K9me3) and lysine 27-trimethylation (H3K27me3) during the first 1 to 2 h postinfection. Kinetic analysis of the modulation of nucleosomes and heterochromatin modifications over the course of lytic infection demonstrates a progressive removal that coincided with initiation of viral gene expression. We obtained evidence for three phases of heterochromatin removal from an early gene promoter: an initial removal of histones and heterochromatin not dependent on ICP0, a second ICP0-dependent round of removal of H3K9me3 that is independent of viral DNA synthesis, and a third phase of H3K27me3 removal that is dependent on ICP0 and viral DNA synthesis. The presence of ICP0 in transfected cells is also sufficient to promote removal of histones and H3K9me3 modifications of cotransfected genes. Overall, these results show that ICP0 promotes histone removal, a reduction of H3K9me3 modifications, and a later indirect reduction of H3K27me3 modifications following viral early gene expression and DNA synthesis. Therefore, HSV ICP0 promotes the reversal of host epigenetic silencing mechanisms by several mechanisms.

IMPORTANCE
The human pathogen herpes simplex virus (HSV) has evolved multiple strategies to counteract host-mediated epigenetic silencing during productive infection. However, the mechanisms by which viral and cellular effectors contribute to these processes are not well defined. The results from this study demonstrate that HSV counteracts host epigenetic repression in a dynamic stepwise process to remove histone 3 (H3) and subsequently target specific heterochromatin modifications in two distinct waves. This provides the first evidence of a stepwise reversal of host epigenetic silencing by viral proteins. This work also suggests that targets capable of disrupting the kinetics of epigenetic regulation could serve as potential antiviral therapeutic agents.
Targeting Autophagy in Dendritic Cells as a Mechanism to Limit Immunopathogenesis in Herpetic Stromal Keratitis
Authors: Blaho John A.
Published: January 2016

In a recent
mBio
article, Y. Jiang, X. Yin, P. M. Stuart, and D. A. Lieb [mBio 6(6):e01426-15, 2015, doi:10.1128/mBio.01426-15] presented an elegant set of experiments that utilized a transgenic, knockout strain of mice whose dendritic cells (DCs) are incapable of undergoing autophagy, to dissect out the aspects of the chronic inflammatory response following viral infection of corneal epithelial cells. The authors’ results provide a potential proof of concept that the DC autophagy pathway may be a valid target for therapeutic drug design in certain inflammatory pathologies.
Small Intestine Bacterial Overgrowth and Environmental Enteropathy in Bangladeshi Children
Authors: Donowitz Jeffrey R. , Haque Rashidul , Kirkpatrick Beth D. , Alam Masud , Lu Miao , Kabir Mamun , Kakon Shahria Hafiz , Islam Bushra Zarin , Afreen Sajia , Musa Abu , Khan Shaila Sharmeen , Colgate E. Ross , Carmolli Marya P. , Ma Jennie Z. , Petri William A.
Published: January 2016

Recent studies suggest small intestine bacterial overgrowth (SIBO) is common among developing world children. SIBO’s pathogenesis and effect in the developing world are unclear. Our objective was to determine the prevalence of SIBO in Bangladeshi children and its association with malnutrition. Secondary objectives included determination of SIBO’s association with sanitation, diarrheal disease, and environmental enteropathy. We performed a cross-sectional analysis of 90 Bangladeshi 2-year-olds monitored since birth from an impoverished neighborhood. SIBO was diagnosed via glucose hydrogen breath testing, with a cutoff of a 12-ppm increase over baseline used for SIBO positivity. Multivariable logistic regression was performed to investigate SIBO predictors. Differences in concomitant inflammation and permeability between SIBO-positive and -negative children were compared with multiple comparison adjustment. A total of 16.7% (15/90) of the children had SIBO. The strongest predictors of SIBO were decreased length-for-ageZ score since birth (odds ratio [OR], 0.13; 95% confidence interval [CI], 0.03 to 0.60) and an open sewer outside the home (OR, 4.78; 95% CI, 1.06 to 21.62). Recent or frequent diarrheal disease did not predict SIBO. The markers of intestinal inflammation fecal Reg 1β (116.8 versus 65.6 µg/ml;P= 0.02) and fecal calprotectin (1,834.6 versus 766.7 µg/g;P= 0.004) were elevated in SIBO-positive children. Measures of intestinal permeability and systemic inflammation did not differ between the groups. These findings suggest linear growth faltering and poor sanitation are associated with SIBO independently of recent or frequent diarrheal disease. SIBO is associated with intestinal inflammation but not increased permeability or systemic inflammation.

IMPORTANCEA total of 165 million children worldwide are considered stunted, which is associated with increased risk of death prior to age 5 years and cognitive disability. Stunting has, in part, been attributed to the presence of environmental enteropathy. Environmental enteropathy is a poorly understood condition leading to chronic intestinal inflammation. It has been postulated that small intestine bacterial overgrowth contributes to the pathogenesis of environmental enteropathy as overgrowth has been associated with intestinal inflammation and micronutrient malabsorption when it develops in other clinical contexts. This study confirms the finding that overgrowth occurs at high rates in the developing world. This is the first study to show that overgrowth is associated with intestinal inflammation and linear growth delay in this setting and is the first to examine why children with no known gastrointestinal dysfunction develop overgrowth from the developing world environment.