bluuebunny/crossref_metadata_2025 huggingface dataset:
Differentiating Structural Damage From Piezo-Fibre-Based Sensor Damage in Multifunctional Composites
Authors: Mehdizadeh Mohammad , John Sabu , Wang Chun H. , Verijenko Viktor , Rowe Wayne , Ghorbani Kamran , Galehdar Amir , Callus Paul J.
Published: February 2012

Structural health monitoring systems (SHMS) are increasingly being considered for implementation in a wide range of industries, including transport, civil infrastructure, and energy production. As the application of SHM systems increase, it will be increasingly important to quantify the durability, reliability, and reparability of the SHM system. This paper investigates the electrical and electro-mechanical characteristics of piezoelectric sensors in an attempt to distinguish sensor failure from structural damage. This study involved the measurements of pertinent electrical properties for three various types of advanced piezoelectric sensors under fatigue loading. Changes in the capacitance and inductance of these sensors have been recorded, highlighting the deleterious structural changes in the sensor itself without any discernible change in the structure being monitored.
Modeling, Analysis, and Experiments of Interfiber Compaction Effects in FMC Actuators for Bio-Inspired Applications
Authors: Zhang Zhiye , Philen Michael
Published: February 2012

Recently, flexible matrix composite (FMC) actuators were demonstrated in a robotic fish for swimming. When actuated at a specific frequency in the experiments, the sinusoidal component of the thrust was eliminated, leaving only a constant thrust. This elimination of the sinusoidal component of the thrust is due to the hydroelastic tailoring of the tail stiffness with the actuation frequency. The FMC actuators are pressure-driven muscle-like actuators capable of large displacements as well as large blocking forces. The FMC actuators can also exhibit a large change in stiffness through simple valve control when the working fluid has a high bulk modulus. Several analytical models have been developed that capture the geometrical and material nonlinearities, the compliance of the inner liner, and entrapped air in the fluid. This paper focuses on the inter fiber compaction in the composite laminate, which is shown to reduce the effective closed-valve stiffness. In this paper, a new analytical model considering the inter fiber compaction effect as well as the material and geometric nonlinearities is developed. Analysis and experimental results demonstrate that the new compaction model can improve the prediction of the response behavior of the actuator.
Power Output and Dissipation of a Negative Capacitance Shunt Coupled to Piezoelectric Transducers
Authors: Beck Benjamin , Cunefare Kenneth A. , Collet Manuel
Published: February 2012

A negative capacitance shunt is a basic, analog, active circuit electrically connected to a piezoelectric transducer to control vibrations of flexural bodies. The electrical impedance of the negative capacitance shunt modifies the effective modulus of the piezoelectric element to reduce the stiffness and increase the damping which causes a decrease in amplitude of the vibrating structure to which the elements are bonded. The negative capacitance circuit is built around a single operational amplifier using passive circuit elements. To gain insight into the electromechanical coupling, the power consumption of the op-amp and the power dissipated in the resistive element are measured. The power output of the op-amp increases for increasing control gain of the negative capacitance. The power characteristics of the shunt are compared to the reactive input power analysis developed in earlier work.
Design and Development of a Biomimetic Jellyfish Robot That Features Ionic Polymer Metal Composites Actuators
Authors: Najem Joseph , Akle Barbar , Sarles Stephen A. , Leo Donald J.
Published: February 2012

This paper presents the design, fabrication, and characterization of a second generation biomimetic jellyfish robot that uses ionic polymer metal composites (IPMCs) as flexible actuators for propulsion. The shape and swimming style of this underwater vehicle are based on the Aurelia aurita jellyfish, which has an average swimming speed of 13 mm/s and which is known for a high swimming efficiency. The critical components of the vehicle include the flexible bell that provides the overall shape and dimensions of the jellyfish, a central hub used to provide electrical connections and mechanical support to the actuators, and flexible IPMC actuators that extend radially from the central hub. In order to provide increased shape holding ability and reduced weight, the bell is fabricated from a commercially available heat-shrinkable polymer film. A new lightweight hub has been designed and was fabricated by 3D printing using ABS plastic material. The hub features internal electrical contacts for providing voltage to the individual IPMC actuators. Finally, a new set of IPMC actuators are manufactured using the Direct Assembly Process (DAP). The IPMC actuators constructed for this study demonstrated peak-to-peak strains of ∼ 0.7% in water across a frequency range of 0.1–1.0Hz. By tailoring the applied voltage waveform and the flexibility of the bell, the completed robotic jellyfish swam at maximum speed of 1.5 mm/s.
Small-Scale Wind Energy Harvesting From Flow-Induced Vibrations
Authors: Sivadas Vishak , Wickenheiser Adam M.
Published: February 2012

Significant wind energy exists in the boundary layers around naturally occurring and manmade structures. This energy source has remained largely untapped, even though it presents a significant source of energy for powering wireless devices in built-up areas. This paper discusses a study on harnessing energy from piezoelectric transducers by using bluff body and vortex-induced vibration phenomena induced by low-speed flows. The proposed devices are miniature, scalable, aeroelastic wind harvesters designed for extracting turbulent, low-speed wind energy from the boundary layers around structures. The design configuration consists of a bluff body with a flexible piezoelectric cantilever attached to the trailing edge. In this design, transverse vibrations are induced in the piezoelectric members by alternating vortex shedding. The multi-physics software package COMSOL is used for coupled simulation of the fluid and structural domains, and Matlab is used to couple the structural deformations to the attached power harvesting circuitry. The design and environmental parameters are varied to optimize the configuration and to identify the significant parameters in the design. The lock-in phenomenon, in which the vortex shedding frequency is entrained to the fundamental structural frequency, is exploited to achieve resonance over a range of flow velocities, thus increasing the velocity “bandwidth” of the devices. Simulations are run for different characteristic dimensions or shapes for the bluff body to study the strength and nature of vortex shedding in the presence of vibrating beam sections. The results of parameter variation for the design configuration is presented and discussed with regard to broadband wind energy harvesting.
Lamb Wave Propagation Through Off-Axis Media
Authors: Brown Jacob , Reynolds Whitney , Doyle Derek , Zagrai Andrei
Published: February 2012

The use of elastic wave based Structural Health Monitoring has shown its usefulness in both characterizing and diagnosing composite structures. Techniques using elastic wave SHM are being developed to allow for improved efficiency and assurance in all stages of space structure development and deployment. These techniques utilize precise understanding of wave propagation characteristics to extract meaningful information regarding the health and validity of a component, assembly, or structure. However, many of these techniques focus on the diagnostic of traditional, isotropic materials, and questions remain as to the effect of the orthotropic properties of resin matrix composite material on the propagation of elastic waves. As the demands and expectations placed upon composite structures continue to expand in the space community, these questions must be addressed to allow the development of elastic wave based SHM techniques that will enable advancements in areas such as automated build validation and qualification, and in-situ characterization and evaluation of increasingly complex space structures. This study attempts to aid this development by examines the effect of cross ply, off-axis fiber orientation on the propagation characteristics of lamb waves. This is achieved by observing the result of symmetric and anti-symmetric wave propagation across materials in cases containing both off-axis and axially-aligned elements. In both cases the surface plies of the test specimen are axially aligned with the wave propagation direction. Using these results, the relative effect of core ply orientation on lamb wave propagation, and lamb wave sensitivity to bulk properties, or alternatively, the dominance of surface properties on propagation characteristics, can be seen, and this information can be used to aid in future research and application of lamb waves for interrogation of advanced, high-strain composite space structures. It was found that the core orientation caused significant variation in the S0 wave velocity, while yielding little influence on the A0 wave velocity.
Modeling the Conductance of the Peptide Alamethicin With and Without Ion Gradients
Authors: Creasy M. Austin , Leo Donald J.
Published: February 2012

Alamethicin is an antibiotic peptide from the fungus Trichoderma viride that forms ion channels in bilayer lipid membranes. Each peptide consists of 20 amino acids that can form larger channels with the congregation of multiple monomers of the peptide. These formed ion channels have some voltage dependent characteristics when a potential is induced across the bilayer. This potential can be from an applied voltage source or from an ion concentration gradient inducing a transmembrane potential across the membrane. The peptide alamethicin can be modeled as a conductor that allows the flow of ions through the membrane. The formed channels have distinct conductance level states caused by accumulation of additional alamethicin monomers being added to an individual ion channel. The voltage dependence of the accumulation of multiple ion channels can be modeled for the average response. A probabilistic model is used to capture the statistics of the state changes of individual channels. This type of model can be summed to simulate the conductance of multiple channels within a bilayer. This work focuses on obtaining the statistic for individual ion channels and using those statistics to show that a probabilistic model of the peptide’s conductance can capture some of the dynamics seen in aggregated responses. The Nernst equation is used to estimate the transmembrane potential caused by an ion gradient of a bilayer in equilibrium. This potential is used in the model to assist in determining the current conductance states of an individual channel of the peptide in the presence of an ion gradient. This paper will show the experimental results of ion currents across a bilayer induced by membrane potentials and the ion currents induced by ion gradients. The statistics of the measurements are used in a probabilistic conductance model of the peptide alamethicin.
A High-Performance Dual-Stage Hydrogen Compressor System Using Ca0.2Mm0.8Ni5 Metal Hydride
Authors: Bhuiya Md Mainul Hossain , Lee Chi Young , Hopkins Ryan , Yoon Hyungkee , Kim Sunwoo , Park Sang Heup , Kim Kwang J.
Published: February 2012

Dual stage hydrogen compressor with high pressure compression ability can operate efficiently using geothermal, low temperature solar, waste energy as well as combination of these energy sources. In this study, a dual stage thermal compressor system for hydrogen compression was investigated using three different hydrogen storage materials: LaNi5, Ca0.6Mm0.4Ni5 and Ca0.2Mm0.8Ni5. Compression ratio of Ca0.2Mm0.8Ni5 was found to be 56% and 14.7% higher than those of LaNi5 and Ca0.6Mm0.4Ni5 respectively, for single stage thermal compressor system with inlet supply pressure of 600 psig. On the other hand, compression performance of Ca0.2Mm0.8Ni5 was similar to that of LaNi5 at low supply pressure (e.g. 200 psig) condition. In this paper, a dual stage hydrogen compressor system with LaNi5 in first stage and Ca0.2Mm0.8Ni5 in second stage is proposed for high pressure hydrogen compression based on the experimental results of single stage system. Results show that 53% higher compression ratio can be attained using dual stage hydrogen compressor when appropriate storage materials are selected for two stages.
Identification of a Force Sensing Resistor for Tactile Applications
Authors: Saadeh Mohammad Y. , Trabia Mohamed B.
Published: February 2012

A force sensing resistor (FSR) is a conductive polymer that changes resistance with the application of pressure at its surface. FSR can be used for tactile applications. In this work, the use of FSR to measure the fingertip force within an electronic Braille reading device is considered. To achieve this goal, an experimental procedure to test the FSR’s response is proposed. In this experiment, the FSR is placed between a linear actuator and a load cell. The linear actuator generates different loading profiles to mimic various tactile forces. Identification process starts by applying static loadings at the FSR’s surface. These loads are used to calibrate the FSR and study its time drift. In the next phase of the process, an up-chirp signal is used to identify the dynamics of the FSR. The resulting data are modeled using system identification techniques to obtain possible dynamic models for the FSR. Both linear and nonlinear models are proposed. The linear model is compared to Hammerstein, Wiener, and Hammerstein-Wiener nonlinear models. The accuracy and robustness of the four models are assessed using various loading profiles. Numerical criteria are developed to compare these models with respect to the experimental results.
FEA Evaluation of the Mechanical and Electromagnetic Performance of Slot Log-Spiral Antennas in Conformal Load-Bearing Antenna Structure (CLAS)
Authors: Daliri Ali , Wang Chun H. , John Sabu , Galehdar Amir , Rowe Wayne S. T. , Ghorbani Kamran , Callus Paul J.
Published: February 2012

Conformal load-bearing antenna structures (CLAS) have been attracting the attention of aerospace industries in recent years. This type of multifunctional structures combines the features of conventional antennas with load-bearing capacity and has important applications in military and commercial airplanes especially for Unmanned Aerial Vehicles (UAVs). Equiangular slot spiral antennas are an alternative to traditional rectangular slots because of its wideband radiation characteristics. However, the mechanical characteristics of such a spiral antenna integrated into a structure are so far largely unexplored. In this paper, the electromagnetic (scattering parameter, radiation pattern and gain) and mechanical properties (stress concentration factor (SCF)) of spiral antennas is investigated using finite element analysis (FEA). The results lead to a recommendation for using this type of antenna for future CLAS concepts.
Characterization of Sectored-Electrode IPMC-Based Propulsors for Underwater Locomotion
Authors: Hubbard Joel J. , Fleming Maxwell , Leang Kam K. , Palmre Viljar , Pugal David , Kim Kwang J.
Published: February 2012

Ionic polymer-metal composite (IPMC) actuators with sectored (patterned) electrodes have been fabricated for realizing bending and twisting motion. Such IPMCs can be used to create next-generation artificial fish-like propulsors that can mimic the undulatory, flapping, and complex motions of real fish fins. Herein, a thorough experimental study is performed on sectored IPMCs to characterize their performance. Specifically, results are presented to show (1) the achievable twisting response; (2) blocking force and torque; (3) power consumption and effectiveness; and (4) propulsion characteristics. The results can be utilized to guide the design of practical marine systems driven by IPMC propulsors. The design of an example underwater robotic system is also described which employs the IPMC actuators, and the performance of the robotic system is reported.
Innovation and Miniaturization in Applications of Explosives
Authors: Kennedy James E.
Published: February 2012

Explosives represent a readily transported, single-use energy source that can drive materials at a very high local power density. Effects of generated forces may be contained or may act upon a target at a distance. Specific energy release from detonating explosives is, to first order, independent of the size or the confinement of a charge. This enables engineering analysis for design or effects estimation over orders of magnitude in scale. Thus miniaturization of devices or applications is possible down to a scale that corresponds to the minimum charge size that is capable of supporting detonation, and this scale can be smaller than 1 mm. This talk is directed toward those without prior training in or exposure to explosives, to open communication between developers of smart systems and practitioners of explosives. The explosives field is highly interdisciplinary, as is the field of smart systems. The talk describes basic processes of detonation operation and coupling to surroundings, and addresses limitations to the use of explosives for applications. Perhaps the major engineering challenges in miniaturized applications of explosives are emplacement of the explosive in the desired form at the desired location in an assembly, and provision for introduction of external power to bring about initiation of detonation at the desired location or locus within an explosive charge. Initiation sources may be electrical, mechanical or laser-based. Explosive component families that are commercially available and that are innovative and still under development are described.
Maximum and Practical Sustainably Harvestable Vibrational Power From Avian Subjects
Authors: Shafer Michael W. , Garcia Ephrahim
Published: February 2012

In this study we investigate the maximum sustainably harvestable vibrational power from a bird for the purpose of creating new long life tracking tags. We develop a model for harvestable power based on known maximum laden mass capabilities of various bird species and a standard power model for bird flight. Both maximum harvestable power and practically harvestable powers are derived. Practically harvestable power was derived assuming a payload mass and a given specific power for the vibrational harvester. Based on these models, data from various species ranging from 2.55 g to 11.6 kg in mass is used to show relationships between harvestable power and mass. Using estimates for a piezoelectric energy harvester specific power, the practically harvestable power ranges from tens of microwatts to hundreds of milliwatts, depending on the species.
Linear and Nonlinear Aeroelastic Energy Harvesting Using Electromagnetic Induction
Authors: Anice´zio Marcela de Melo , Erturk Alper , De Marqui Junior Carlos , Inman Daniel J.
Published: February 2012

Transforming aeroelastic vibrations into electricity for low-power generation has received growing attention over the past couple of years. The goal is to convert wind energy into electricity for powering small electronic components employed in wireless applications such as structural health monitoring. The potential applications of interest for aeroelastic energy harvesting range from lifting components in aircraft structures to several other engineering problems involving wireless electronic components located in high wind areas. This paper investigates linear and nonlinear aeroelastic energy harvesting using electromagnetic induction. A two-dimensional airfoil with plunge and pitch degrees of freedom (DOF) is considered. The electromagnetic induction is introduced to the plunge DOF by means of a coil-magnet combination and the nonlinearities are introduced through the pitch DOF. The governing dimensionless aeroelastic equations are given with electromagnetic coupling and a resistive load in the electrical domain. The effects of several dimensionless system parameters (electromechanical coupling, load resistance, and coil inductance) on the dimensionless electrical power as well as the dimensionless linear flutter speed are investigated. After considering the linear problem, combined nonlinearities are investigated to improve the electrical output. A cubic stiffness of the hardening type is combined with the free play nonlinearity to make the resulting nonlinear oscillations bounded with acceptable amplitude over a wide range of airflow speeds. The results and the dimensionless simulations presented in this work can be employed for designing and optimizing scalable aeroelastic energy harvesters for wind energy harvesting using electromagnetic induction.
Active Nanoporous Membranes for Desalination
Authors: Sundaresan Vishnu Baba , Carr James Patrick
Published: February 2012

Current water desalination technologies such as reverse osmosis (RO) and nanofiltration (NF) use tortuous structures and cylindrical nanopores to reject salts by size exclusion. The selective rejection of salts dissolved in water using nanopores requires large pressure gradients across the membranes to produce reasonable flow rates. The electrical power required for generating large pressure gradients increases the operational cost for desalination and limits its application as portable units in small communities and in third-world countries. Further, recently proposed desalination methods using carbon nanotubes and nanofluidic diodes have limited lifetime due to clogging and fouling from contaminants in feed water. Thus, existing or evolving technologies are expensive, bulky and not practical where it is needed the most. In order to develop a desalination system that is not limited by the disadvantages of existing systems, this article investigates the feasibility of a novel active nanopore membrane with superior ion rejection and water transport properties. An active nanopore is a shape-changing hyperboloidal pore that is formed in a rugged electroactive composite membrane and utilizes coupled electrostatic, hydrodynamic and mechanical interactions due to reversible mechanical oscillations between the charged pore walls and dissolved ions in water for desalination. This novel approach takes advantage of the shape of the pore to create a pumping action in the hyperboloidal channel to selectively transport water molecules. In order to demonstrate the applicability of this novel concept for water desalination, the paper will use a theoretical model to model the ion rejection properties and flow rate of salt-free water through an active nanoporous membrane.
Planar RF Antenna Reconfiguration With Ni-Ti Shape Memory Alloys
Authors: Wolcott P. J. , Dapino M. J. , Wang Z. , Zhang L.
Published: February 2012

Nickel-titanium shape memory alloys (SMA) are utilized to achieve a multi-band RF (radio frequency) antenna through reconfiguration. Switches made from shape memory alloys electronically connect together a planar antenna arrangement, creating several electrical signal pathways and reconfiguration to be realized. The changes in geometry induced by the switching create different working frequencies of the antenna leading to multiple bands. The switches open and close due to an induced phase change from martensite to austenite via resistive heating from a separate electric circuit. Switch design is based on a previously successful switch geometry with the goal of miniaturizing the reconfigurable antenna system. Simulations were performed to determine an optimal geometry for reconfiguration with the switches to generate measurable changes in working frequency in a planar antenna. Based on these simulations, a planar antenna consisting of a dielectric material between conductive copper layers was designed and constructed for use with the SMA switches. The antenna design is based on a patch antenna that is reconfigured to new geometries as the SMA switches are activated. The working frequency of the planar antenna arrangement can be tuned to between 2.25 GHz and 2.43 GHz depending on geometry as measured with S11 signal reflection.
Electromagnetic Radiation From the Detonation of Metal Encased Explosives
Authors: Brown W. T. , Schmidt M. F. , Dzwilewski P. T.
Published: February 2012

Electromagnetic radiation accompanying the detonation of chemical explosives was first reported in 1954. Such emissions result from detonations of both bare and cased explosives. However, the dominant wavelengths of emissions from these two types of explosions generally differ by as much as three or four orders of magnitude. We present results of far-field and near-field experimental measurements of electric fields emitted by metal encased explosives, and show that metal fracture is the dominant mechanism leading to these emissions. Additionally, we present results of computational analysis of explosive fracture of steel cylinders performed to investigate the correlation between the time-dependent fragment size distribution and the pattern of electromagnetic emissions.
Advanced Development of a Smart Material Design, Modeling, and Selection Tool
Authors: Park Jung-Kyu , Washington Gregory
Published: February 2012

Smart materials have significantly varied properties and their various types are used broadly in many different engineering applications. It is important to develop tools which enable one to determine the best material for a particular application. In this research, system-level simulation models and collected material data are compiled in a GUI-based computer software called Polymers and Smart Materials Database (PSMD). This material selection tool encompasses material properties and material-level models as well as potential smart material applications. This type of compiled data can expedite the material selection process when designing smart material based systems by allowing one to choose the most effective material for the application. The software tool offers a wide variety of design and selection features. Material property and performance charts are provided to compare material properties and to choose the best material for optimal performance. The tool enables users to categorize material properties and create their own databases. This paper also highlights the modeling strategies being conducted in the area of elastomers and smart materials.
Simultaneous Energy Harvesting and Gust Alleviation for a Multifunctional Wing Spar Using Reduced Energy Control Laws via Piezoceramics
Authors: Wang Ya , Inman Daniel J.
Published: February 2012

The increasing need for lightweight structures in Unmanned Aerial Vehicle (UAV) applications raise issues involving gust alleviation. Here we examine the gust alleviation problem using a self-sensing, self-charging, and self-actuating structure. The basic idea is that the wing itself is able to harvest and store energy from the normal vibrations during flight along with any available sunlight. If the wing experiences any strong, unexpected wind gust, it will sense the increased vibration levels and provide vibration control to maintain its stability. In this paper, a multifunctional wing spar is designed, which integrates a flexible solar cell array, piezoceramic wafers, a thin film battery and an electronics module into a composite structure. This multifunctional wing spar therefore carries on the functions of energy harvesting and storage, as well as the functions of gust alleviation via piezoelectric materials. The piezoceramic wafers act as sensors, actuators, and harvesters. The global modulus and stiffness of this multifunctional wing spar are estimated using both the rule of mixtures and the cross section transformation method. These values are then used in an Euler-Bernoulli cantilever beam model of the multifunctional spar. The first two dominant modes are predicted analytically for the distributed parameter model. The finite element method is employed to confirm the analytical eigenvalues estimation. Special attention is given to the self-contained gust alleviation with the goal of using harvested energy. The gust signals are generated using a Gaussian white noise source n (t) ∼ N (0,1) fed into a linear filter, with the required intensity, scale lengths, and power spectral density (PSD) function for the given flight velocity and height. The Dryden PSD function is implemented for atmospheric turbulence modeling. The recently developed reduced energy control law is combined with a positive strain feedback controller to minimize the actuation energy and the dissipated heat energy. Positive feedback operation amplifiers (op-amps) and voltage buffer op-amps are implemented for two dominant mode gust disturbance controls. This work builds off of our previous research in self-charging structures and holds promise for improving UAV performance in wind gust alleviation.
Laser Welding of Nickel Titanium and 304 Stainless Steel Tubes
Authors: Hahnlen Ryan , Fox Gordon , Dapino Marcelo J.
Published: February 2012

Shape memory nickel-titanium (NiTi) can generate large blocking stresses and high recovery strains, up to 8%, which make NiTi a good candidate for solid state actuators, resulting in substantial weight and space savings when they replace traditional electric or hydraulic systems. A challenge surrounding NiTi based actuators is integration of the NiTi components into a given system; this alloy is difficult and expensive to machine and weld to itself and structural materials. In this research, we join NiTi and 304 stainless steel tubes 9.52 mm (0.375 in) in diameter through laser welding to create joints with weld depths up to 1650 μm (0.065 in). By joining NiTi to a common structural material that is easily machined and readily welded to other materials, the challenges surrounding system integration are reduced. The joints prepared in this study were characterized through optical microscopy, hardness mapping, and mechanical testing. The average ultimate shear strength of these joints is 423 MPa (61.3 ksi) and the resulting HAZ has a maximum width of 21.9 μm with a maximum hardness of 929 HV.
Piezoelectric Vibration Damping Using Autonomous Synchronized Switching on Inductance
Authors: Delpero Tommaso , Di Lillo Luigi , Bergamini Andrea , Ermanni Paolo
Published: February 2012

Shunted piezoelectric transducers can be used to dissipate vibration energy of a host structure. The Synchronized Switch Damping on Inductance (SSDI) is a shunting technique featured by a nearly rectangular shape of the resulting voltage on the transducer being in anti-phase with the structure’s velocity. As for these systems, previous studies have reported the strong connection of the dissipated energy on the slope of the voltage signal occurring during the switch. This implies that any electrical losses have to be minimized in order to increase the slope of the voltage signal and, thus, the damping performance of the shunt. Moreover, the rate of change of the voltage signal represents a critical issue for autonomous shunts, where the switch can be inefficient because the power for switching the circuit is not supplied by an external source but is supplied by the vibrating structure itself. In this study, a new technique for improving the damping performance of autonomous switching shunt is proposed based on reducing the electrical losses of the switch. Finally, an experimental validation of the novel shunting technique is carried out.
Novel Flow Energy Converter Based on Dielectric Elastomers
Authors: Maas Ju¨rgen , Graf Christian
Published: February 2012

While the usefulness of small scale prototypes for harvesting the energy of waves have already been demonstrated, the utilization of the capability of flow energy in rivers based on electroactive polymers is still a significant challenge. To harvest the energy of flowing waters, a novel flow energy converter based on a simple and environmentally sustainable mechanical design is developed, consisting of an elastomeric tube with a closing mechanism at the outlet side. Because the stationary stretch of the tube is comparably small, the tube has to be operated in resonance, which offers a high resonant magnification of the tube deformation. The resonant operation can be obtained, when the tube is closed rapidly and a shock wave is induced into the tube, which is often referred to as water hammer. Based on a small-scale prototype, this expected mechanical behavior of the tube was demonstrated.
Comment on “Phonemic Diversity Supports a Serial Founder Effect Model of Language Expansion from Africa”
Authors: Cysouw Michael , Dediu Dan , Moran Steven
Published: February 2012

We show that Atkinson’s (Reports, 15 April 2011, p. 346) intriguing proposal—that global linguistic diversity supports a single language origin in Africa—is an artifact of using suboptimal data, biased methodology, and unjustified assumptions. We criticize his approach using more suitable data, and we additionally provide new results suggesting a more complex scenario for the emergence of global linguistic diversity.
Structure and Allostery of the PKA RIIβ Tetrameric Holoenzyme
Authors: Zhang Ping , Smith-Nguyen Eric V. , Keshwani Malik M. , Deal Michael S. , Kornev Alexandr P. , Taylor Susan S.
Published: February 2012

Keeping a Kinase in Check

Cyclic adenosine monophosphate (cAMP)–dependent protein kinase (PKA) is involved in the regulation of several key metabolic pathways. It exists in mammalian cells as an inactive tetramer composed of a regulatory (R) subunit dimer and two catalytic (C) subunits. cAMP binding causes activation by releasing the C subunits. Insight into PKA regulation has come from structures of R and C subunit heterodimers; however, further understanding requires knowledge of the holoenzyme structure.

P. Zhang
et al.

(p.
712
) report a high-resolution structure of the RIIβ
2
:C
2
tetramer. The structure reveals interactions at an interface between the two RC heterodimers and provides insight into the mechanism of allosteric activation upon cAMP binding.
One-Step Fabrication of Supramolecular Microcapsules from Microfluidic Droplets
Authors: Zhang Jing , Coulston Roger J. , Jones Samuel T. , Geng Jin , Scherman Oren A. , Abell Chris
Published: February 2012

Be My Guests

For a range of applications, including medical diagnostics or drug delivery, it is necessary to encapsulate one or more components into a microcapsule. While there are many methods that can do this, most either produce a range of capsule size or are not easily scalable for making large quantities.

J. Zhang
et al.

(p.
690
) developed a microfluidic-based system for making capsules using host-guest chemistry. Cucurbit[8]uril, which readily forms complexes in water, was used as the host molecule and could accommodate two different guest molecules. Rapid complexation was observed of methyl viologen–modified gold nanoparticles and a naphthol-containing copolymer.
€22 Billion Stimulus Brings Worries About
Egalité
Authors: Casassus Barbara
Published: February 2012

On 3 February, French Prime Minister Francois Fillon announced five new winners in the €7.7 billion Excellence Initiatives, which aims to help create a group of five to 10 world-class research and higher education clusters.
Using Nucleic Acid Microarrays To Perform Molecular Epidemiology and Detect Novel β-Lactamases: a Snapshot of Extended-Spectrum β-Lactamases throughout the World
Authors: Lascols Christine , Hackel Meredith , Hujer Andrea M. , Marshall Steven H. , Bouchillon Sam K. , Hoban Daryl J. , Hawser Stephen P. , Badal Robert E. , Bonomo Robert A.
Published: February 2012

The worldwide dissemination of extended-spectrum-β-lactamase (ESBL)- and carbapenemase-producing
Enterobacteriaceae
is a major concern in both hospital and community settings. Rapid identification of these resistant pathogens and the genetic determinants they possess is needed to assist in clinical practice and epidemiological studies. A collection of
Escherichia coli
,
Klebsiella pneumoniae
,
Klebsiella oxytoca
, and
Proteus mirabilis
isolates, including phenotypically ESBL-positive (
n
= 1,093) and ESBL-negative isolates (
n
= 59), obtained in 2008–2009 from a longitudinal surveillance study (SMART) was examined using an
in vitro
nucleic acid-based microarray. This approach was used to detect and identify
bla
ESBL
(
bla
SHV
,
bla
TEM
, and
bla
CTX-M
genes of groups 1, 2, 9, and 8/25) and
bla
KPC
genes and was combined with selective PCR amplification and DNA sequencing for complete characterization of the
bla
ESBL
and
bla
KPC
genes. Of the 1,093 phenotypically ESBL-positive isolates, 1,041 were identified as possessing at least one
bla
ESBL
gene (95.2% concordance), and 59 phenotypically ESBL-negative isolates, used as negative controls, were negative. Several ESBL variants of
bla
TEM
(
n
= 5),
bla
SHV
(
n
= 11),
bla
CTX-M
(
n
= 19), and
bla
KPC
(
n
= 3) were detected. A new
bla
SHV
variant,
bla
SHV-129
, and a new
bla
KPC
variant,
bla
KPC-11
, were also identified. The most common
bla
genes found in this study were
bla
CTX-M-15
,
bla
CTX-M-14
, and
bla
SHV-12
. Using nucleic acid microarrays, we obtained a “molecular snapshot” of
bla
ESBL
genes in a current global population; we report that CTX-M-15 is still the dominant ESBL and provide the first report of the new β-lactamase variants
bla
SHV-129
and
bla
KPC-11
.
Nuclear Export and Expression of Human T-Cell Leukemia Virus Type 1
tax
/
rex
mRNA Are RxRE/Rex Dependent
Authors: Bai X. T. , Sinha-Datta U. , Ko N. L. , Bellon M. , Nicot C.
Published: February 2012

Human T-cell leukemia virus type 1 (HTLV-1) is a complex retrovirus associated with the lymphoproliferative disease adult T-cell leukemia/lymphoma (ATL) and the neurodegenerative disorder tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). Replication of HTLV-1 is under the control of two major
trans
-acting proteins, Tax and Rex. Previous studies suggested that Tax activates transcription from the viral long terminal repeat (LTR) through recruitment of cellular CREB and transcriptional coactivators. Other studies reported that Rex acts posttranscriptionally and allows the cytoplasmic export of unspliced or incompletely spliced viral mRNAs carrying
gag/pol
and
env
only. As opposed to HIV's Rev-responsive element (RRE), the Rex-responsive element (RxRE) is present in all viral mRNAs in HTLV-1. However, based on indirect observations, it is believed that nuclear export and expression of the doubly spliced
tax/rex
RNA are Rex independent. In this study, we demonstrate that Rex does stimulate Tax expression, through nuclear-cytoplasmic export of the
tax
/
rex
RNA, even though a Rex-independent basal export mechanism exists. This effect was dependent upon the RxRE element and the RNA-binding activity of Rex. In addition, Rex-mediated export of
tax
/
rex
RNA was CRM1 dependent and inhibited by leptomycin B treatment. RNA immunoprecipitation (RNA-IP) experiments confirmed Rex binding to the
tax
/
rex
RNA in both transfected cells with HTLV-1 molecular clones and HTLV-1-infected T cells. Since both Rex and p30 interact with the
tax/rex
RNA and with one another, this may offer a temporal and dynamic regulation of HTLV-1 replication. Our results shed light on HTLV-1 replication and reveal a more complex regulatory network than previously anticipated.
Nonstructural Proteins 7 and 8 of Feline Coronavirus Form a 2:1 Heterotrimer That Exhibits Primer-Independent RNA Polymerase Activity
Authors: Xiao Yibei , Ma Qingjun , Restle Tobias , Shang Weifeng , Svergun Dmitri I. , Ponnusamy Rajesh , Sczakiel Georg , Hilgenfeld Rolf
Published: February 2012

Nonstructural proteins 7 and 8 of severe acute respiratory syndrome coronavirus (SARS-CoV) have previously been shown by X-ray crystallography to form an 8:8 hexadecamer. In addition, it has been demonstrated that N-terminally His
6
-tagged SARS-CoV Nsp8 is a primase able to synthesize RNA oligonucleotides with a length of up to 6 nucleotides. We present here the 2.6-Å crystal structure of the feline coronavirus (FCoV) Nsp7:Nsp8 complex, which is a 2:1 heterotrimer containing two copies of the α-helical Nsp7 with conformational differences between them, and one copy of Nsp8 that consists of an α/β domain and a long-α-helix domain. The same stoichiometry is found for the Nsp7:Nsp8 complex in solution, as demonstrated by chemical cross-linking, size exclusion chromatography, and small-angle X-ray scattering. Furthermore, we show that FCoV Nsp8, like its SARS-CoV counterpart, is able to synthesize short oligoribonucleotides of up to 6 nucleotides in length when carrying an N-terminal His
6
tag. Remarkably, the same protein harboring the sequence GPLG instead of the His
6
tag at its N terminus exhibits a substantially increased, primer-independent RNA polymerase activity. Upon addition of Nsp7, the RNA polymerase activity is further enhanced so that RNA up to template length (67 nucleotides) can be synthesized. Further, we show that the unprocessed intermediate polyprotein Nsp7-10 of human coronavirus (HCoV) 229E is also capable of synthesizing oligoribonucleotides up to a chain length of six. These results indicate that in case of FCoV as well as of HCoV 229E, the formation of a hexadecameric Nsp7:Nsp8 complex is not necessary for RNA polymerase activity. Further, the FCoV Nsp7:Nsp8 complex functions as a noncanonical RNA polymerase capable of synthesizing RNA of up to template length.
The Human Respiratory Syncytial Virus Matrix Protein Is Required for Maturation of Viral Filaments
Authors: Mitra Ruchira , Baviskar Pradyumna , Duncan-Decocq Rebecca R. , Patel Darshna , Oomens Antonius G. P.
Published: February 2012

An experimental system was developed to generate infectious human respiratory syncytial virus (HRSV) lacking matrix (M) protein expression (M-null virus) from cDNA. The role of the M protein in virus assembly was then examined by infecting HEp-2 and Vero cells with the M-null virus and assessing the impact on infectious virus production and viral protein trafficking. In the absence of M, the production of infectious progeny was strongly impaired. Immunofluorescence (IF) microscopy analysis using antibodies against the nucleoprotein (N), attachment protein (G), and fusion protein (F) failed to detect the characteristic virus-induced cell surface filaments, which are believed to represent infectious virions. In addition, a large proportion of the N protein was detected in viral replication factories termed inclusion bodies (IBs). High-resolution analysis of the surface of M-null virus-infected cells by field emission scanning electron microscopy (SEM) revealed the presence of large areas with densely packed, uniformly short filaments. Although unusually short, these filaments were otherwise similar to those induced by an M-containing control virus, including the presence of the viral G and F proteins. The abundance of the short, stunted filaments in the absence of M indicates that M is not required for the initial stages of filament formation but plays an important role in the maturation or elongation of these structures. In addition, the absence of mature viral filaments and the simultaneous increase in the level of the N protein within IBs suggest that the M protein is involved in the transport of viral ribonucleoprotein (RNP) complexes from cytoplasmic IBs to sites of budding.
Plasmacytoid Dendritic Cells Reduce HIV Production in Elite Controllers
Authors: Machmach K. , Leal M. , Gras C. , Viciana P. , Genebat M. , Franco E. , Boufassa F. , Lambotte O. , Herbeuval J. P. , Ruiz-Mateos E.
Published: February 2012

HIV elite controllers (EC) are a rare group of HIV-infected patients who are able to maintain undetectable viral loads during a long period of time in the absence of antiretroviral treatment. Adaptive immunity and host genetic factors, although implicated, do not entirely explain this phenomenon. On the other hand, plasmacytoid dendritic cells (pDCs) are the principal type I interferon (IFN) producers in response to viral infection, and it is unknown whether pDCs are involved in the control of HIV infection in EC. In our study, we analyzed peripheral pDC levels and IFN-α production by peripheral blood mononuclear cells (PBMCs) in EC compared to other groups of HIV-infected patients, the ability of pDCs to reduce HIV production
in vitro
, and the mechanisms potentially involved. We showed preserved pDC counts and IFN-α production in EC. We also observed a higher capacity of pDCs from EC to reduce HIV production and to induce T cell apoptosis, whereas pDCs from viremic patients barely responded without previous Toll-like receptor 9 (TLR-9) stimulus. The preserved functionality of pDCs from EC to reduce viral production may be one of the mechanisms involved in the control of HIV viremia in these subjects. These results demonstrate the importance of innate immunity in HIV pathogenesis, and an understanding of pDC mechanisms would be helpful for the design of new therapies.
Live Attenuated Herpes Simplex Virus 2 Glycoprotein E Deletion Mutant as a Vaccine Candidate Defective in Neuronal Spread
Authors: Awasthi Sita , Zumbrun Elizabeth E. , Si Huaxin , Wang Fushan , Shaw Carolyn E. , Cai Michael , Lubinski John M. , Barrett Shana M. , Balliet John W. , Flynn Jessica A. , Casimiro Danilo R. , Bryan Janine T. , Friedman Harvey M.
Published: February 2012

A herpes simplex virus 2 (HSV-2) glycoprotein E deletion mutant (gE2-del virus) was evaluated as a replication-competent, attenuated live virus vaccine candidate. The gE2-del virus is defective in epithelial cell-to-axon spread and in anterograde transport from the neuron cell body to the axon terminus. In BALB/c and SCID mice, the gE2-del virus caused no death or disease after vaginal, intravascular, or intramuscular inoculation and was 5 orders of magnitude less virulent than wild-type virus when inoculated directly into the brain. No infectious gE2-del virus was recovered from dorsal root ganglia (DRG) after multiple routes of inoculation; however, gE2-del DNA was detected by PCR in lumbosacral DRG at a low copy number in some mice. Importantly, no recurrent vaginal shedding of gE2-del DNA was detected in immunized guinea pigs. Intramuscular immunization outperformed subcutaneous immunization in all parameters evaluated, although individual differences were not significant, and two intramuscular immunizations were more protective than one. Immunized animals had reduced vaginal disease, vaginal titers, DRG infection, recurrent genital lesions, and recurrent vaginal shedding of HSV-2 DNA; however, protection was incomplete. A combined modality immunization using live virus and HSV-2 glycoprotein C and D subunit antigens in guinea pigs did not totally eliminate recurrent lesions or recurrent vaginal shedding of HSV-2 DNA. The gE2-del virus used as an immunotherapeutic vaccine in previously HSV-2-infected guinea pigs greatly reduced the frequency of recurrent genital lesions. Therefore, the gE2-del virus is safe, other than when injected at high titer into the brain, and is efficacious as a prophylactic and immunotherapeutic vaccine.