bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Reliability Evaluation Using Enhanced HDMR
Authors: Rao B. N. , Chowdhury Rajib
Published: July 2009

This paper presents a new computational tool for predicting failure probability of randomly parametered structural/mechanical systems based on high dimensional model representation (HDMR) generated from low order function components. HDMR is a general set of quantitative model assessment and analysis tools for capturing the high-dimensional relationships between sets of input and output model variables. When first-order HDMR approximation of the original high dimensional implicit limit state/performance function is not adequate to provide desired accuracy to the predicted failure probability, this paper presents an enhanced HDMR (eHDMR) method to represent the higher order terms of HDMR expansion by expressions similar to the lower order ones with monomial multipliers. The accuracy of the HDMR expansion can be significantly improved using preconditioning with a minimal number of additional input-output samples without directly invoking the determination of second- and higher order HDMR terms. This study aims to assess how accurately and efficiently eHDMR approximation technique can capture complex model output uncertainty. As a part of this effort, the efficacy of HDMR approximation, which is recently applied to reliability analysis, is also demonstrated. Once the approximate form of implicit response function is defined using HDMR/eHDMR, the failure probability can be obtained by statistical simulation.
Application of Mixed Equivalent Solid and Explicit Hole Models to Analysis of Thick Perforated Plates
Authors: Josserand E. , Billon F.
Published: July 2009

Confronted with the problem of how to conduct a complete fatigue analysis of the Tube Plate (TP) of Tubular and Shell Heat Exchangers and particularly of the Steam Generators equipping nuclear power plants of the Pressurized Water Reactor type (PWR), analysts have developed a method to analyse stress in perforated flat and thick Tube Plates with square penetration (crate) patterns, and in particular to analyse several specific zones such as the Interface Zones and various Effects, such as the Secondary (or Shell) Thermal Gradient Effect (STG Effect), the Thermal Gradient in the No-Tube Lane Effect (TGL Effect) and their interactions. The benefit of the approach is that it enables to analyze mechanical and thermal stress calculated using a full 3D Finite Element model incorporating an equivalent solid and the different Interface Zones, and allowing simulating the specific Thermo-Mechanical Effects. The Interface Zones (IZs) are those between the perforated and non-perforated area, the STG Effect is due to the strong gradient near the Secondary (or Shell) Side surface, the TGL Effect is produced by a temperature gradient across the No-Tube Lane. The method used for the fatigue analysis is based on a “Partitioning Stress Method” by means of which the stress induced by the various load types — mechanical loads, global thermal loads, local thermal effects (STG and TGL Effects), and local geometrical effects (IZs) — are first treated separately and then recombined with their appropriate Stress Multiplier Functions.
Effects of Surface Finish and Loading Conditions on the Low Cycle Fatigue Behavior of Austenitic Stainless Steel in PWR Environment: Comparison of LCF Test Results With NUREG/CR-6909 Life Estimations
Authors: Le Duff Jean Alain , Lefranc¸ois Andre´ , Vernot Jean Philippe
Published: July 2009

During mid 2006, ANL issued a NUREG/CR-6909 [2] report that is now applicable in The US for evaluations of PWR environmental effects in the fatigue analysis of new reactor components. In order to assess the conservativeness of the application of this NUREG report, low cycle fatigue (LCF) tests were performed by AREVA NP on austenitic stainless steel specimens in a PWR environment. The selected material exhibits in an air environment a fatigue behavior consistent with the ANL reference “air” mean curve. Tests were performed for two various loading conditions: for fully reverse triangular signal (for comparison purpose with tests performed by other laboratories with same loading conditions) and complex signal, simulating strain variation for actual typical PWR thermal transients. Two surface finish conditions were tested: polished and ground. The paper presents on one side the comparison of environmental penalty factors (Fen = Nair,RT/Nwater) as observed experimentally with the ANL formulation (considering the strain integral method for complex loading), and, on the other hand, the actual fatigue life of the specimen with the fatigue life predicted through the NUREG/CR-6909 application. Low Cycle Fatigue test results obtained on austenitic stainless steel specimens in PWR environment with triangle waveforms at constant low strain rates gives Fen penalty factors close to those estimated using the ANL formulation (NUREG report 6909). On the contrary, it was observed that constant amplitude LCF test results obtained under complex signal reproducing an actual sequence of a cold and hot thermal shock exhibits significantly lower environmental effects when compared to the Fen penalty factor estimated on the basis of the ANL formulations. It appears that the application of the NUREG/CR-6909 [2] in conjunction with the Fen model proposed by ANL for austenitic stainless steel provides excessive margins whereas the current ASME approach seems sufficient to cover significant environmental effect for components.
Fatigue Crack Growth Simulation Using S-Version FEM
Authors: Kikuchi Masanori , Wada Yoshitaka , Takahashi Masafumi , Li Yulong
Published: July 2009

Fatigue crack growth under mixed mode loading conditions is simulated using S-FEM. By using S-FEM technique, only local mesh should be remeshed and it becomes easy to simulate crack growth. By combining with re-meshing technique, local mesh is re-meshed automatically, and curved crack path is modeled easily. Plural fatigue crack problem is solved by this technique. For two through crack problems, crack coalescence condition is proposed by JSME standard. By simulating this problem by S-FEM, it is shown that thid criterion depends on initial crack size. Then more than 160 cases are simulated by changing several parameters. Results are summarized by normalized form, and new criterion is proposed.
Repair Welding of Long-Term Used Ethylene Pyrolysis Radiant Tubes
Authors: Shiga Keisuke , Hara Yasuhiro , Yamamoto Eiichi
Published: July 2009

Ethylene pyrolysis furnace radiant tubes have been used at the highest temperature in petrochemical plants. Although the tubes suffer several damages, carburization is the most important one which causes of the tube replacement. Carburization reduces the weldability and causes cracking at repair welding. This paper describes the degradation phenomena and the weldability of long-term used centrifugal casting tubes at the ethylene pyrolysis furnace.
Effects of Negative Biaxial Loadings and Notch on Failure Assessment Diagrams
Authors: Ragupathy K. , Ramesh K. , Hall Doug
Published: July 2009

The Failure Assessment Diagram (FAD) is a simplified and robust flaw assessment methodology which simultaneously connects two dominant failure criteria: Linear Elastic Fracture mechanics (LEFM) on one end and Plastic collapse on other end. This interaction is the realm of Elastic Plastic Fracture Mechanics (EPFM.) It is popularly known as the R6 approach which graphically characterizes the impact of plasticity on crack driving force. In the recent years, there has been continuous interest in using Failure Assessment Diagrams (FAD) to assess the failure of cracked structures subjected to biaxial loadings. Biaxiality is defined as the ratio of stress applied parallel and normal to the crack. Some aircraft components operate under negative biaxial ratios up to −0.5. In this paper, a detailed study on FAD was conducted using FEA computed J-integral methods to investigate the effect of biaxial loading using different FAD approaches for geometries with notches. Geometries with a crack that emanates at a fillet region were simulated with various biaxial loading ratios from −0.5 to +0.5 using 2014-T6 material. FAD curves were numerically generated for cracks at notched regions subjected to various biaxial loadings using J-integral values from finite element analyses and validated its practical application. Comparison studies were made between uniaxial and biaxial loading cases with FAD curves created using standard approaches for four different crack sizes. Under small scale yielding, this study clearly shows that FAD curves are not influenced by negative biaxial loading at low load (up to 40% of yield strength). It was clearly confirmed that the majority of previously developed analytical FAD curves do not effectively account for notch and plasticity effects due to negative biaxilaity. Based on this study, tension normal to the crack and compression parallel to the crack is the worst combination and it has a very pronounced effect on FAD curve shapes. The standard analytical FAD curves are non-conservative compared to the approach recommended here, particularly under the worst case condition. The proposed method is expected to predict lower failure loads relative to currently accepted analytical methods.
Tensile Testing and Material Property Development of High Density Polyethylene Pipe Materials
Authors: Adams Timothy M. , Hall Siegrid , Scavuzzo Rudolph J. , Munson Douglas , Andrasik Jeffrey W. , Findlan Shane
Published: July 2009

Degradation of service water systems is a major issue facing nuclear power plant owners, and many plants will require repair or replacement of existing carbon steel piping components. High Density Polyethylene pipe has been used in non-safety service water systems for over nine years and found to perform well, but it is not currently permitted in the ASME Section III Boiler and Pressure Vessel Code, Division 1 for use in nuclear safety-related systems. To assist in the implementation of High Density Polyethylene pipe in the ASME Boiler and Pressure Vessel Code, Section III, Division 1 for Safety Class 3 applications, EPRI initiated a High Density Polyethylene pipe and pipe material testing program. This test program includes tensile testing and fatigue testing of High Density Polyethylene piping and piping components and the development of slow crack growth data. To determine the material and engineering properties needed, extensive tensile testing of specimens cut from High Density Polyethylene pipe was conducted. The initial tensile test program was conducted on PE 3408 with cell classification 345464C and a second, not yet finalized, phase was added to test PE 4710 with cell classification 445474C. The data developed during the testing were used to establish ultimate strain, elastic moduli, yield stress and yield strain values for both new and aged materials. Because extruded HDPE properties vary in the hoop and axial directions and the properties are highly affected by temperature, specimens were cut in both the hoop and axial directions and were tested at temperatures ranging from 50° F to 180° F. This paper provides a description and overview of the PE 3408 cell class 345464C test program. In addition, an overview and summary of the test results for the PE 3408 cell class 345464C are provided.
Applications of Biologically Inspired Membranes
Authors: Freeman Eric , Weiland Lisa Mauck
Published: July 2009

The focus of this paper is projection of the performance of nastic actuators under conditions of variable stimulus with particular emphasis on pharmaceutical applications. The nastic actuator concept considered here employs controlled transport of charge and fluid across a selectively permeable membrane to achieve bulk deformation, similar to nastic movements in the plant kingdom. These membranes may utilize biological ion pumps, ion channels, and/or ion exchangers to transport fluid and ions and thereby expand/contract a phase separated inclusion. Studies to date have focused pH gradients or the spontaneous introduction of ATP chemical energy as the triggers for actuator response. In this effort the physics of the nastic actuator response under variable stimulus is considered. In addition, the possibility of controlled bursting of the nastic inclusions for vaccine delivery is explored.
Recent Advances in Impedance-Based Wireless Sensor Nodes
Authors: Farinholt Kevin M. , Taylor Stuart G. , Overly Timothy G. , Park Gyuhae , Farrar Charles R.
Published: July 2009

This paper presents recent developments in an extremely compact, wireless impedance sensor node for use in structural health monitoring (SHM). The sensor node uses a low-cost integrated circuit that can measure and record the electric impedance of a piezoelectric active-sensor. The sensor node also integrates several components, including a microcontroller for local computing, telemetry for wireless data transmission, multiplexers for managing up to seven piezoelectric transducers per node, energy storage mediums, and several triggering options including a wireless triggering circuit into one package to truly realize a comprehensive, self-contained wireless active-sensor node for SHM applications. It is estimated that this sensor node requires less than 75 mW of total power to operate measurement, computation and data transmission. In addition, the sensor node can also be used for the active-sensor self-diagnostic process that can monitor the operational condition of piezoelectric transducers used in SHM applications. The performance of this miniaturized and portable device is compared to our previous results and its broader capabilities are demonstrated.
Optimal Control of Time-Delayed Linear Systems With the Method of Continuous Time Approximation
Authors: Sun Jian-Qiao , Song Bo
Published: July 2009

This paper presents optimal control studies of delayed dynamical systems with the help of a method of continuous time approximation (CTA). The CTA method proposes a continuous time approximation of the delayed portion of the response leading to a high and finite dimensional state space formulation of the time-delayed system. Optimal controls of the system such as LQR and output feedback controls are readily designed with the existing design tools. In the paper, we present an output feedback control by means of the mapping approach studied previously. In order to accomplish the objective of control design, we also examine various discretization schemes of the CTA method in frequency domain.
Thin Film Nitinol Microstent for Aneurysm Occlusion
Authors: Chun Youngjae , Levi Daniel S. , Mohanchandra K. P. , Carman Gregory P.
Published: July 2009

This film nitinol produced by sputter deposition was used in the design of microstents intended to treat small vessel aneurysms. Thin film microstents were fabricated by “hot-target” DC sputter deposition. Both stress-strain curves and DSC curves were generated for the film used to fabricate stents. The films used for stents had an Af temperatures of approximately 36 degrees allowing for body activated response from a micro-catheter. The ten micron film was only slightly radio-opaque; thus, a Td marker was attached to the stents to guide fluoroscopic delivery. Thin film microstents were tested in a flow loop with and without nitinol support skeletons to given additional radial support. Stents could be compressed into and easily delivery in < 3 Fr catheters. Theoretical frictional and wall drag forces on a thin film nitinol small vessel vascular stent were calculated and the radial force exerted by thin film stents was evaluated theoretically and experimentally. In-vivo studies in swine confirmed that thin film nitinol microstents could be deployed accurately and consistently in the swine cranial vasculature.
Comparing Linear and Essentially Nonlinear Vibration-Based Energy Harvesting
Authors: Quinn D. Dane , Triplett Angela L. , Bergman Lawrence A. , Vakakis Alexander F.
Published: July 2009

Self-contained long-lasting energy sources are rapidly increasing in importance as portable electronics and inaccessible devices such as wireless sensors are finding wider and more varied applications. However, in many circumstances replacing power supplies, such as conventional batteries, becomes impractical and the development of a self-renewing source of energy is paramount to the continued development of such devices. The ability to convert ambient mechanical energy to usable electrical energy fills these requirements and one aspect of current research seeks to increase the efficiency and performance of these energy harvesting systems. However, to achieve acceptable performance conventional vibration-based energy harvesting devices based on linear elements must be specifically tuned to match environmental conditions such as the frequency and amplitude of the external vibration. As the environmental conditions vary under ambient conditions the performance of these linear devices is dramatically decreased. The strategy to efficiently harvest energy from low-level, intermittent ambient vibration, proposed herein, relies on the unique properties of a particular class of strongly nonlinear vibrating systems that are referred to as “essentially” nonlinear.
An Experimental Study of Change Detection in Uncertain Chain-Like Systems
Authors: Hernandez-Garcia Miguel R. , Masri Sami F. , Ghanem Roger
Published: July 2009

In this study, a decentralized time-domain identification technique for chain-like MDOF systems is used in conjunction with a probabilistic framework to obtain a stochastic representation of estimated changes in stiffness-like and damping-like structural coefficients in a laboratory three-story building structure that had been tested at the Los Alamos National Laboratory.
Estimation and Control of a Bio-Inspired Morphing Aircraft
Authors: Hurst Allen C. , Wickenheiser Adam , Garcia Ephrahim
Published: July 2009

An unmanned aerial vehicle has been developed with the ability to reconfigure its structure through morphing, to provide increased performance that will allow the aircraft to perform a bio-inspired perching maneuver similar to those performed by birds. Investigations into the accuracy and computational requirements of methods of estimation and control are needed to determine how various methods can be used for safe, reliable control of the aircraft. This paper discusses various estimation and control methods that could be used to allow the morphing aircraft to perform a desired maneuver. Simulations present some control examples of the aircraft following a set of trajectories, both for the nonlinear aircraft model and its linearized dynamics.
Damage Detection in Satellite Bolted Joints
Authors: Doyle Derek , Zagrai Andrei , Arritt Brandon , Cakan Hakan
Published: July 2009

To overcome current limitations of satellite operation timelines, Operationally Responsive Space (ORS) satellites are being developed for rapid configuration and assembly. Time spent on flight qualification tests aimed at assembly verification and launch vehicle integration must be reduced to less than a week. Structural health monitoring (SHM) is seen as a possible avenue for real-time assessment of satellite integrity and qualification before launch. Embedded ultrasonics and magneto-mechanical impedance (MMI) were considered as potential candidates for diagnostics of critical system elements. Piezoelectric wafer active sensors in conjunction with an acousto-elastic SHM were used for assessment of aerospace structures with bolted joints. In the presented analysis, the acousto-elastic behavior of the joint was used as an indicator of structural integrity. Experimental results show changes in the nonlinear response of joints as a result of differing bolt torque. Localization potential of the acousto-elastic technique was demonstrated in a complex structure analogous to a typical satellite panel. The MMI method has shown utility in assessing condition of bolted joints in thin plates and a satellite structure. Experimental data reveal changes in magnitude and position of impedance peaks induced by the difference in structural loads applied to the joint. It is suggested that both the acousto-elastic and MMI methods have indicated possibilities for detecting and characterizing damage in satellite bolted joints.
Bifurcations and Chaos of Composite Laminated Piezoelectric Rectangular Plate With One-to-Three Internal Resonance
Authors: Yao Zhi-Gang , Zhang Wei
Published: July 2009

The bifurcations and chaotic motions of a simply supported symmetric cross-ply composite laminated piezoelectric rectangular plate are analyzed for the first time, which are forced by the transverse and in-plane excitations. It is assumed that different layers of symmetric cross-ply composite laminated piezoelectric rectangular plate are perfectly bonded to each other and with piezoelectric actuator layers embedded in the plate. Based on the Reddy’s third-order shear deformation plate theory, the nonlinear governing equations of motion for the composite laminated piezoelectric rectangular plate are derived by using the Hamilton’s principle. The excitation loaded by piezoelectric layers is considered. The Galerkin’s approach is employed to discretize partial differential governing equations to a two-degree-of-freedom nonlinear system under combined the parametric and external excitations. The method of multiple scales is utilized to obtain the four-dimensional averaged equation. Numerical method is used to find the periodic and chaotic motions of the composite laminated piezoelectric rectangular plate. The numerical results show the existence of the periodic and chaotic motions in the averaged equation. It is found that the chaotic responses are especially sensitive to the forcing and the parametric excitations. The influence of the transverse, in-plane and piezoelectric excitations on the bifurcations and chaotic behaviors of the composite laminated piezoelectric rectangular plate is investigated numerically.
Bio-Inspired Sensor Skins for Structural Health Monitoring
Authors: Tata Uday , Huang Haiying , Deb Shanchali , Chiao J. C. , Carter Ronald
Published: July 2009

This paper presents the simulation and experimental work that proved the feasibility of using a patch antenna for strain measurement. A patch antenna, usually serves as a data-transmitting device, can also function as a transducer that directly encodes the experienced strain into its resonant frequency. Printed on a flexible substrate, the antenna sensor is small in size, has a low profile, and can be conformal to any attached surface. Future work on interrogating the antenna sensor using a wireless noncontact method is also discussed. Without needing electric wiring for power supply and data transmitting, the antenna sensor has a great potential for the realization of engineered sensor skins that imitate the sensor of pain for structural health monitoring purpose.
On the Applicability of F2MC Variable Impedance Materials for Prosthetic Devices
Authors: Philen Michael
Published: July 2009

The applicability of variable modulus fluidic flexible matrix composites (F2MC) is investigated for development of prosthetic devices. The F2MC material is an innovative combination of high performance composite tubes containing high bulk modulus fluids. The new material system can potentially achieve several orders of magnitude change in stiffness through valve control. The F2MC material system is investigated in this research through analytical studies for active impedance control for load transfer reduction in a transtibial prosthetic sockets and impedance joint control for an ankle-foot orthoses (AFO). Preliminary analysis results indicate that the variable modulus system can reduce the load transfer between the limb and transtibial socket and can provide impedance tailoring for improving foot-slap in an AFO.
System Identification and Pseudo-Earthquake Excitation of a Real-Scaled 5 Story Steel Frame Structure
Authors: Park Eunchurn , Lee Sang-Hyun , Lee Sung-Kyung , Chung Hee-San , Min Kyung-Won
Published: July 2009

The accurate identification of the dynamic response characteristics of a building structure excited by input signals such as real earthquake or wind load is essential not only for the evaluation of the safety and serviceability of the building structure, but for the verification of an analytical model used in the seismic or wind design. In the field of system identification (SI) which constructs system matrices describing the accurate input/output relationship, it is critical that input should have enough energy to excite fundamental structural modes and a good quality of output containing structural information should be measured. In this study forced vibration testing which is important for correlating the mathematical model of a structure with the real one and for evaluating the performance of the real structure was implemented. There exist various techniques available for evaluating the seismic performance using dynamic and static measurements. In this paper, full scale forced vibration tests simulating earthquake response are implemented by using a hybrid mass damper. The finite element (FE) model of the structure was analytically constructed using ANSYS and the model was updated using the results experimentally measured by the forced vibration test. Pseudo-earthquake excitation tests showed that HMD induced floor responses coincided with the earthquake induced ones which was numerically calculated based on the updated FE model.
Guided Lamb Wave Interrogation of a Curved Composite Plate [0/90] Using the Hilbert-Huang Transform Approach
Authors: Yoo Byungseok , Pines Darryll , Purekar Ashish S.
Published: July 2009

This paper discusses a study of the Hilbert-Huang transform approach as a structural health monitoring tool for a curved composite panel with a [90/0/0/90]sym lay-up sequence. The Hilbert amplitude, phase, and frequency coupled with empirical mode decomposition (EMD) process are defined as the Hilbert-Huang transform (HHT) and used to evaluate structural damage in the curved composite panel as the level of damage increases. Piezoelectric (PZT) sheets are used as an actuator and receivers, akin to the pitch-catch method to excite the guided Lamb waves and to obtain the vibratory response of the curved composite panel. In this paper, a new damage metric using the Hilbert-Huang transformed energy and amplitude in conjunction with the Hilbert-Huang transformed phase are proposed and investigated as a new structural damage index. Results show that these damage metrics are capable of tracking progressive damage growth in the form of loss of torque load.
Damage Measure in Complex 1D Waveguides
Authors: Apetre Nicole , Ruzzene Massimo
Published: July 2009

This paper introduces a wave propagation-based damage index (DI) which relies on the estimation of phase gradients of propagating waves for accurate damage localization and on the prediction of mode conversion coefficients for damage quantification. The undamaged, or unperturbed, reference response is derived directly from the damaged component, through the application of filtering procedures in the wavenumber/frequency domain. These procedures separate incident waves from reflections caused by structural discontinuities encountered along the wave path. The DI formulation is illustrated through a numerical model of a beam with a small notch, modeled as a localized thickness reduction. The beam’s wave propagation response is simulated through the combined application of perturbation techniques and the Spectral Finite Element Method (SFEM). The resulting numerical tool allows efficient computation of the wave propagation response and the analysis of the effects of localized damages of various extent and location. The dynamic behavior of damaged beams is described through a general higher order model which couples bending and axial behavior, thus allowing the prediction of mode conversion phenomena. Numerical examples are presented to illustrate the model capabilities.
The Effects of Shape Reconfiguration on Morphing Aircraft in Perching Maneuvers
Authors: Wickenheiser Adam M. , Garcia Ephrahim
Published: July 2009

This paper focuses on a novel morphing aircraft capability called perching: the ability of an aircraft to make a planted landing using primarily aerodynamic forces in lieu of high thrust. Specifically, the modeling of the perching aircraft’s aerodynamics and the problem of computing and optimizing a perching trajectory using this model are presented. The aerodynamic model discussed herein is designed using empirical and analytical methods in both separated and attached flow regimes, including nonlinear and time-varying effects such as flow separation and dynamic stall. This vehicle model is used to optimize the landing trajectory with respect to its spatial boundaries; these include the maximum undershoot — or dip below the landing point — and the required starting distance from the landing site. Optimal solutions of varying thrust-to-weight ratio and center of gravity location are compared. Additionally, perching trajectories that compare stalled versus un-stalled and morphing versus fixed-configuration aircraft are presented in order to demonstrate the effects of relaxed constraints on flight envelope and shape reconfiguration, respectively. The available control for disturbance rejection is distinguished between morphing and fixed-configuration aircraft. These results show that vehicle morphing increases the controllability of the aircraft throughout the maneuver as well as decreases the spatial requirements of the optimal perching trajectory.
Patterning of alkanethiolate self-assembled monolayers by downstream microwave nitrogen plasma: Negative and positive resist behavior
Authors: Weng Chih-Chiang , Liao Jiunn-Der , Wu Yi-Te , Tsai Shih-Chun , Chen Chia-Hao , Zharnikov Michael
Published: July 2009

Taking octadecanethiolate self-assembled monolayers (SAMs) adsorbed on Au(111) as a test system, the authors demonstrated patterning of an aliphatic monomolecular resist by downstream microwave nitrogen plasma in proximity printing geometry with a mesh mask simply placed onto the SAM surface. The behavior of the SAM resist was found to be dependent on the plasma treatment time, which is related to the dominance of different plasma-induced processes at different treatment stages. At a short treatment, the most prominent process is the activation of the SAM-ambient interface, resulting in subsequent adsorption of airborne species onto the plasma-exposed areas upon the exposure of the SAM pattern to ambient. At a long treatment, the dominant process is the chain decomposition with the subsequent desorption of the released fragments and carbonization of the residual film. Due to the above behavior, aliphatic SAMs can serve as either negative or positive monomolecular resists at either a short or long plasma treatment, as soon as the fabricated pattern is transferred to the underlying substrate.
Micropatterning of polymeric semiconductor by selective lift-off method using epoxy mold
Authors: Wang Zhe , Yu Xinhong , Xing Rubo , Han Yanchun , Takahara Atsushi
Published: July 2009

A simple and efficient method for patterning polymeric semiconductors for applications in the field of organic electronics is proposed. The entire polymer layer, except for the desired pattern, is selectively lifted off from a flat poly(dimethylsiloxane) (PDMS) stamp surface by an epoxy mold with a relief pattern. This is advantageous because the elastic deformation of the PDMS stamp around protrusions of a patterned stamp under pressure can assist the plastic deformation of a polymer film along the pattern edges, yielding large area and high quality patterns, and the PDMS surface has low surface energy, which allows the easy removal of the polymer film.
Strong Coupling Between Single-Electron Tunneling and Nanomechanical Motion
Authors: Steele G. A. , Hüttel A. K. , Witkamp B. , Poot M. , Meerwaldt H. B. , Kouwenhoven L. P. , van der Zant H. S. J.
Published: July 2009

Tuning Carbon Nanotube Resonances

Nanoscale resonators can be used in sensing and for processing mechanical signals. Single-walled carbon nanotubes have potential design advantages as resonators in that their oscillatory motion could be coupled to electron transport (see the Perspective by

Hone and Deshpande

).

Steele
et al.

(p.
1103
, published online 23 July) and

Lassagne
et al.

(p.
1107
, published online 23 July) report that the resonance frequency of a suspended single-walled carbon nanotube can be excited when operated as a single-electron transistor at low temperatures. Electrostatic forces are set up when the carbon nanotubes charge and discharge. The resonance frequency depends on applied voltages, and the coupling is strong enough to drive the mechanical motion into the nonlinear response regime. Differences in the responses of the devices in the two studies reflect in part the different quality factors of the resonators and different cryogenic temperatures.
HIERARCHY OF CRITICAL EXPONENTS ON SIERPINSKI FRACTAL RESISTOR NETWORKS
Authors: MIRZAEE M. , JAFARIZADEH M. A.
Published: July 2009

Using the S3-symmetry of Sierpinski fractal resistor networks we determine the current distribution as well as the multifractals spectrum of moments of current distribution by using the real space renormalization group technique based on ([q/4]+1) independent Schure's invariant polynomials of inwards flowing currents.
TEMPERATURE DEPENDENT MONOVACANCY PARAMETERS VERSUS DIVACANCIES IN ANALYZING DATA OF DEFECTS IN METALS
Authors: ZARDAS G. E. , SYMEONIDES CH. I.
Published: July 2009

The appropriate procedure for analyzing experimental data of defects in metals is discussed. The following two diverse procedures have been proposed earlier: either in terms of single vacancy formation with temperature dependent enthalpy and entropy, or by assuming coexistence of vacancies and divacancies with temperature-independent parameters. Using aspects of thermodynamics of the defect formation processes in solids, we show that the former procedure leads to self-consistent parameters.
A SCHEME FOR TELEPORTING A GENERAL N-QUBIT STATE THROUGH NONMAXIMALLY ENTANGLED QUANTUM CHANNELS
Authors: TIAN XIU-LAO , XI XIAO-QIANG
Published: July 2009

We propose a scheme for teleporting an arbitrary unknown N-qubit state through nonmaximally entangled quantum channels by using the method of general Bell base decomposition, and give the universal decomposition matrix of the N-qubit. Using the decomposition matrix, one can easily obtain the collapsed state at the receiver's site. The inverse matrix of the decomposition matrix is just the transformation matrix that the receiver can manipulate. The decomposition matrix is a function of the parameters of the quantum channel. After defining the submatrix of the quantum channel, we find that the decomposition matrix is a tensor product of the submatrices.
THE RELAXATION TIME OF A BISTABLE SYSTEM WITH TWO DIFFERENT KINDS OF TIME DELAYS
Authors: ZENG CHUN-HUA , SUN YAN-LIN , CHEN GUANG-XUE
Published: July 2009

In this paper, we study the relaxation time of a bistable system driven by correlated noises when there are two different kinds of time delays in the deterministic (τ) and random (θ) forces, respectively. The expression for the relaxation time Tc is derived by the projection operator method, in which the effects of the memory kernels are taken into account. After introducing a dimensionless parameter R (R = D/α, where D is the strength of multiplicative noise and α is the strength of additive noise), and then performing numerical computations, we find the following: (1) for the case of R ≤ 1, the relaxation time Tc increases as τ increases, i.e. τ slows down the fluctuation decay of the dynamical variable for the case of R ≤ 1; (2) however, for the case of R > 1, Tc decreases as τ increases, i.e. τ enhances the fluctuation decay of the dynamical variable for the case of R > 1; (3) Tc decreases as θ increases, i.e. θ enhances the fluctuation decay of the dynamical variable for the three cases of R (R > 1, R=1, and R < 1).
Effects of vitamin E on mitochondrial dysfunction and asthma features in an experimental allergic murine model
Authors: Mabalirajan Ulaganathan , Aich Jyotirmoi , Leishangthem Geeta Devi , Sharma Surendra Kumar , Dinda Amit Kumar , Ghosh Balaram
Published: July 2009

We showed recently that IL-4 causes mitochondrial dysfunction in allergic asthma. IL-4 is also known to induce 12/15-lipoxygenase (12/15-LOX), a potent candidate molecule in asthma. Because vitamin E (Vit-E) reduces IL-4 and inhibits 12/15-LOX in vitro, here we tested the hypothesis that Vit-E may be effective in restoring key mitochondrial dysfunctions, thus alleviating asthma features in an experimental allergic murine model. Ovalbumin (OVA)-sensitized and challenged male BALB/c mice showed the characteristic features of asthma such as airway hyperresponsiveness (AHR), airway inflammation, and airway remodeling. In addition, these mice showed increase in the expression and metabolites of 12/15-LOX, reduction in the activity and expression of the third subunit of mitochondrial cytochrome- c oxidase, and increased cytochrome c in lung cytosol, which indicate that OVA sensitization and challenge causes mitochondrial dysfunction. Vit-E was administered orally to these mice, and 12/15-LOX expression, key mitochondrial functions, ultrastructural changes of mitochondria in bronchial epithelia, and asthmatic parameters were determined. Vit-E treatment reduced AHR, Th2 response including IL-4, IL-5, IL-13, and OVA-specific IgE, eotaxin, transforming growth factor-β1, airway inflammation, expression and metabolites of 12/15-LOX in lung cytosol, lipid peroxidation, and nitric oxide metabolites in the lung, restored the activity and expression of the third subunit of cytochrome- c oxidase in lung mitochondria and bronchial epithelia, respectively, reduced the appearance of cytochrome c in lung cytosol, and also restored mitochondrial ultrastructural changes of bronchial epithelia. In summary, these findings show that Vit-E reduces key mitochondrial dysfunctions and alleviates asthmatic features.
El papel de la microbiota en la alergia
Authors: Kalliomäki Marko
Published: July 2009

La hipótesis de la higiene vincula la epidemia creciente de manifestaciones clínicas de alergia, eccema atópico, rinoconjuntivitis alérgica y asma a una reducida exposición a microbios en una edad temprana como consecuencia de cambios medioambientales en el mundo industrializado. Entre éstos destacan la mejora del saneamiento y las condiciones de vida, las vacunaciones y el tratamiento antimicrobiano, junto con la disminución del tamaño de las familias y el cambio en la ingestión alimentaria. El descubrimiento de tres subgrupos de linfocitos T reguladores ha revolucionado la base inmunológica original de la hipótesis de la higiene, el llamado paradigma T cooperador 1/T cooperador 2. En caso de tolerancia oral defectuosa aparece alergia. Datos experimentales y clínicos recientes indican que tanto el desarrollo como el mantenimiento de tolerancia oral depende de estos linfocitos T reguladores inmunosupresores. Por otra parte, se ha demostrado que la microbiota intestinal es crucial para la expresión y función apropiadas de los linfocitos T reguladores, lo que conecta estrechamente a la microbiota con la alergia. De hecho, numerosos estudios transversales han demostrado una composición diferente de la microbiota intestinal entre niños con eccema atópico y controles sanos. En la mayoría de los estudios de seguimiento prospectivos publicados hasta la fecha también se ha hallado que las alteraciones de la microbiota intestinal preceden a la aparición de alergia. Los cambios en la cantidad de bifidobacterias, clostrídios y Escherichia coli han sido los resultados más corrientes en estos estudios. No obstante, se ha observado una variación considerable en los diseños de diferentes estudios prospectivos, lo que dificulta la interpretación de las probables causas de los resultados variables. En los estudios futuros que aborden esta cuestión no sólo deberán utilizarse técnicas moleculares novedosas de evaluación de la microbiota intestinal, sino tomar también en consideración otros varios aspectos que se comentan en este trabajo.
Microbiota intestinal, obesidad y diabetes
Authors: Bibiloni Rodrigo , Membrez Mathieu , Chou Chieh Jason
Published: July 2009

La creciente epidemia de obesidad ya ha dejado de estar restringida sólo a los países desarrollados. En el 2005, la Organización Mundial de la Salud alertó que en todo el mundo había aproximadamente 400 millones de adultos obesos y que aproximadamente 20 millones de niños presentaban sobrepeso. La obesidad es un problema sanitario complejo y de consecuencias graves, como la diabetes de tipo 2 y las enfermedades cardiovasculares y de otro tipo. Se han señalado factores conductuales, genéticos y medioambientales como contributivos del sobrepeso y la obesidad. Datos recientes indican que la población de microorganismos residentes en el intestino, conocida como microbiota intestinal, puede influir sobre la absorción de nutrientes y el almacenamiento de energía. Se ha demostrado que la composición macrobiótica difiere tanto entre ratones como entre humanos obesos y magros, lo que deja entrever que la modulación de la composición microbiótica intestinal ofrece una nueva vía para el tratamiento de la obesidad y el sobrepeso. En esta revisión se recuerdan los datos científicos disponibles que respaldan estas especulaciones. También se recopilan en esta revisión los resultados recientes obtenidos en estudios destinados a las contribuciones de la microbiota intestinal a la diabetes.
Type 3 Choroidal Neovascularization Associated with Fundus Flavimaculatus
Authors: Quijano Claudia , Querques Giuseppe , Massamba Nathalie , Soubrane Gisèle , Souied Eric H.
Published: July 2009

Aim: To describe a patient with type 3 choroidal neovascularization (CNV) associated with fundus flavimaculatus (FFM), who underwent treatment with intravitreal ranibizumab. Methods: A 78-year-old woman diagnosed with FFM presented at our department complaining of decreased vision and metamorphopsia in her left eye. Upon a complete ophthalmologic examination, including best corrected visual acuity (BCVA), fundus autofluorescence, fluorescein angiography (FA), indocyanine green angiography (ICGA), and spectral domain optical coherence tomography (SD-OCT), the patient was diagnosed with type 3 CNV associated with FFM, and was submitted to intravitreal ranibizumab injections at monthly intervals. Results: Six months after 3 monthly injections of ranibizumab, the patient’s BCVA improved from 20/64 to 20/32. FA and ICGA revealed a type 3 CNV closure, and the SD-OCT scan showed a fibrous scar replacing the type 3 CNV, with resolution of serous retinal detachment. Conclusion: This case represents the first demonstration of type 3 CNV associated with FFM. Based on our findings, intravitreal ranibizumab may be considered as a therapeutic option for this rare association.
Computer-Assisted Analysis of Heterogeneity on B-Mode Imaging Predicts Instability of Asymptomatic Carotid Plaque
Authors: Hashimoto Hiroyuki , Tagaya Masafumi , Niki Hitoshi , Etani Hideki
Published: July 2009

Background: Computerized assessment of plaque echogenicity by B-mode ultrasonography has demonstrated that the gray-scale median (GSM) pixel intensity of the entire plaque predicts future ischemic stroke in patients with symptomatic carotid stenosis, but not those with asymptomatic stenosis. This study investigated whether plaque heterogeneity (i.e., the distribution of pixel intensities) could predict the instability of asymptomatic plaque. Methods: By comparison with carotid endarterectomy specimens and the GSM values of known tissues on B-mode images, the GSM values for blood, lipid, muscle/fibrous tissue, and calcification were determined. Then we estimated the percent area of each tissue component for 297 asymptomatic plaques causing 40–99% carotid artery stenosis in 250 patients, and monitored the incidence of atherothrombotic cerebral infarction due to carotid stenosis during follow-up. Results: Eight infarcts occurred during a follow-up period of 22 ± 15 months. Plaques in the top tertile for the percent area of lipid-like echogenicity (p < 0.05) and in the lowest tertile for calcification (p = 0.06) showed an association with future infarction according to Kaplan-Meier analysis. This association remained significant after adjustment for the severity of carotid stenosis (hazard ratio 4.4 for lipid-like and 0.24 for calcification-like component, both p < 0.05) according to Cox proportional hazards analysis. Conclusions: The distribution of pixel intensities in carotid plaque on B-mode ultrasonography can be employed to predict instability of asymptomatic plaque and possibly to select patients for interventional procedures. A large-scale investigation will be needed to confirm that estimating the percentage of plaque components relative to the total plaque area can predict ischemic stroke.
Association between Year of Birth and Cognitive Functions in Russia and the Czech Republic: Cross-Sectional Results of the HAPIEE Study
Authors: Bobak Martin , Richards Marcus , Malyutina Sofia , Kubinova Ruzena , Peasey Anne , Pikhart Hynek , Shishkin Sergei , Nikitin Yuri , Marmot Michael
Published: July 2009

Objectives: To assess differences in cognitive functions by year of birth in Russia and the Czech Republic. Methods: A cross-sectional study in the general population of Novosibirsk (Russia) and 6 cities of the Czech Republic recruited random samples of men and women (3,874 Russians, 3,626 Czechs) aged 45–69 years in 2002 (i.e. born in 1933–1957). Word recall, verbal fluency (number of animals named in 1 min) and letter search were assessed in a clinic. Results: Except letter search in men, we found similar levels of cognitive functioning in Russians and Czechs in the youngest subjects and a steeper association of functioning with year of birth in Russia than in the Czech Republic. For example, the difference in the mean word recall, associated with 10 years difference in year of birth, was 0.9 (SE 0.06) words in Russian men, compared to 0.4 (0.06) words in Czech men; in women, these figures were 0.8 (0.05) and 0.3 (0.05), respectively. For all outcomes, except letter search in men, the interactions between year of birth and country were statistically highly significant, and the differences in the year of birth effects between countries were largely unexplained by socioeconomic indicators and risk factors. Conclusion: The slope of association between lower cognitive functioning and earlier year of birth is much steeper in Russia than in the Czech Republic. Given that poor cognitive functioning is a risk factor for dementia, long-term follow-up of this cohort and other studies into population rates of cognitive impairment in Russia should be a priority.
Review of Wireless and Wearable Electroencephalogram Systems and Brain-Computer Interfaces – A Mini-Review
Authors: Lin Chin-Teng , Ko Li-Wei , Chang Meng-Hsiu , Duann Jeng-Ren , Chen Jing-Ying , Su Tung-Ping , Jung Tzyy-Ping
Published: July 2009

Biomedical signal monitoring systems have rapidly advanced in recent years, propelled by significant advances in electronic and information technologies. Brain-computer interface (BCI) is one of the important research branches and has become a hot topic in the study of neural engineering, rehabilitation, and brain science. Traditionally, most BCI systems use bulky, wired laboratory-oriented sensing equipments to measure brain activity under well-controlled conditions within a confined space. Using bulky sensing equipments not only is uncomfortable and inconvenient for users, but also impedes their ability to perform routine tasks in daily operational environments. Furthermore, owing to large data volumes, signal processing of BCI systems is often performed off-line using high-end personal computers, hindering the applications of BCI in real-world environments. To be practical for routine use by unconstrained, freely-moving users, BCI systems must be noninvasive, nonintrusive, lightweight and capable of online signal processing. This work reviews recent online BCI systems, focusing especially on wearable, wireless and real-time systems.