bluuebunny/crossref_metadata_2025 huggingface dataset:
Conducting Polymer-Based Multifunctional Materials
Authors: Paster Eli , Ruddy Bryan P. , Pillai Priam V. , Hunter Ian W.
Published: April 2011

Conducting polymers are employable as low-voltage actuators, sensors, energy storage and delivery components, structural elements, computational circuitry, memory, and electronic components, making them a versatile choice for creating integrated, multifunctional materials and devices. Here we show one such conducting polymer-based, multifunctional system, derived from the versatility of the conducting polymer polypyrrole. Three functions of polypyrrole (actuation, length sensation, and energy storage) have been individually evaluated and cooperatively combined in the synthesis of a multifunctional, polymeric system that actuates, senses strain deformation, and stores energy. The system operates whereby the strain of a polypyrrole actuator is measured by a polypyrrole length sensor, whilst being powered by an array of polypyrrole supercapacitors. Independently, polypyrrole actuators were evaluated at 250 discrete frequencies ranging from 0.01 to 10 Hz using fixed, ±1 V sinusoidal excitation. Polypyrrole length sensors were evaluated using a thin-film dynamic mechanical analyzer for the same range of frequencies with a 2% sinusoidal input strain. Polypyrrole supercapacitors were evaluated using cyclic voltammetry (−1.0 V to +1.0 V; 12.5 to 100 mV/sec) and galvanostatic charge-discharge cycling (0.5 to 2 mA/mg). As an actuator, polypyrrole samples showed measureable actuation strain between 0.001% and 1.6% for the frequency range tested, with amplitude versus frequency decay behavior similar to a first-order low-pass filter. As a length sensor, polypyrrole samples showed linearelastic behavior up to 3% strain and gauge factors near 4. As a symmetric supercapacitor, polypyrrole had capacitance values higher than 20 kF/kg, energy densities near 20 kJ/kg, and power densities near 2 kW/kg. The evaluation of each component, independently, justified creating a cooperative system composed of these three components operating simultaneously. Polypyrrole supercapacitors provided ample power to excite polypyrrole actuators. Polypyrrole length sensors attached in series to polypyrrole actuators were capable of measuring strain from coupled polypyrrole actuators. Performance metrics and future possibilities regarding conducting polymer-based multifunctional materials are discussed.
Experimental Characterization of Electroplastic Elastomers
Authors: Delaney Mark , Clark Willam W. , Weiland Lisa Mauck , Meyer Tara , Pan Tianqi
Published: April 2011

The following details the preliminary characterization of a new class of stiffness-control active materials currently under development. In these materials described as electroplastic elastomers (EPEs), the Young’s modulus may be controlled via the creation and cleaving of crosslink sites using chemical and/or electrochemical stimulation. Unlike their thermally controlled shape memory polymer counterparts, EPEs do not require a continuous supply of energy to maintain either stiffness state. Ultimately this class of material could demonstrate fast, low power mechanical property control characteristics via the more easily controlled electric stimulus. This paper focuses on development of a rapid characterization method to enable expedited development of this new class of materials.
Modeling of Precipitation Effects on the Thermomechanical Behavior of NiTi SMA
Authors: Chemisky Yves , Lagoudas Dimitri , Piotrowski Boris , Patoor Etienne , Ben-Zineb Tarak
Published: April 2011

The effect of precipitation on Ni-rich NiTi Shape Memory Alloys on the thermomechanical properties is investigated. Particulary, the relation between the chemical evolution of the alloy and phase transformation characteristics are studied in order to evaluate the impact on the global mechanical response. The evolution of chemical composition of the alloy is computed using a diffusion law, according to the precipitates population characteristics. The mechanical response is simulated using a Representative Unit Cell which takes into account the structural effect of the precipitates as well as the effect of the composition change. The results show an important effect on the global mechanical behavior even for a small volume fraction of precipitates.
Impact Detection Using an Array of Piezoelectric Wafer Active Sensors and a Microcontroller Unit
Authors: Light-Marquez Abraham , Zagrai Andrei
Published: April 2011

This report discusses the development of an embeddable impact detection system utilizing an array of piezoelectric wafer active sensors (PWAS) and a microcontroller. Embeddable systems are a critical component to successfully implement a complete and robust structural health monitoring system. System capabilities include impact detection, impact location determination and digitization of the impact waveform. A custom algorithm was developed to locate the site of the impact.. The embedded system has the potential for additional capabilities including advanced signal processing and the integration of wireless functionality. For structural health monitoring applications it is essential to determine the extent of damage done to the structure. In an attempt to determine these parameters a series of impact tests were conducted using a ball drop tower on a square aluminum plate. The response of the plate to the impact event was recorded using a piezoelectric wafer sensor network attached to the surface of the plate. From this testing it was determined that several of the impact parameters are directly correlated with the features recorded by the sensor network.
Practical Implementation of Resistance Feedback Measurement for Position Control of a Flexible Smart Inhaler Nozzle
Authors: Furst Stephen J. , Hangekar Rohan , Seelecke Stefan
Published: April 2011

Many “smart materials” have the capacity to be used simultaneously as both an actuator and sensor. For example, SMA actuator wires can be heated by Joule heating to induce contraction; at the same time, the resistance across the SMA wire can be measured to give the user some indication of the strain in the wire. This multi-functional capability enables the design of applications requiring extremely light-weight and streamlined embedded sensors and actuators. One such “smart structure” application is the flexible nozzle used in the Smart Inhaler system under development at North Carolina State University. The Smart Inhaler allows a doctor to control the locations within the pulmonary system that are medicated by controlling the location at which medication is injected into an inhaled airflow. This can reduce the amount of healthy tissue that is exposed to potentially toxic medications, such as those used to treat lung cancer. However, the practical challenge of injecting medication into a flow without disturbing the flow requires a highly controllable yet non-obstructive nozzle. This paper presents a scheme that correlates the resistance measurement across an SMA actuator wire to the wire strain and the resulting deformation of the flexible nozzle. The relationship between resistance and nozzle deformation is nonlinear and hysteretic; however, the repeatability of the relationship allows the user to calibrate the feedback measurement. This enables the wire to be used as both position sensor and positioning actuator. The results represent the first experiments that exploit the multi-functional capabilities of SMA wires in the context of a practical embedded sensor and actuator application.
Modeling and Analysis of Interfiber Compaction Effects in FMC Actuators for Bio-Inspired Applications
Authors: Zhang Zhiye , Philen Michael
Published: April 2011

Recently, flexible matrix composite (FMC) actuators were employed in a robotic fish for swimming [1]. The FMC actuators based on flexible matrix composites developed by Philen et al. [2] 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 [3, 4]. 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 [2, 4, 5]. But no work has been performed in capturing the fiber compaction in the composite laminate, which can have significant influence on the closed valve FMC stiffness. Therefore the objective of this research is to expand upon the previously developed models and incorporate compliance between the woven fibers.
Damage Self-Diagnosis in Carbon Fiber-Reinforced Composites Under Fatigue Loading
Authors: Ngabonziza Yves , Boldrini Claudia , Liaw Benjamin , Li Jackie , Delale Feridun
Published: April 2011

An experimental study was conducted to sense interlaminar delamination in carbon-fiber composites utilizing inherent material piezoresistivity. Damage detection was carried out using discrete electrodes mounted on a Double Cantilever Beam (DCB) specimen. The DCB composite specimens were tested for fatigue interlaminar fracture. The traditional two-point probe and four-point probe technique were employed to measure the through-thickness electrical resistance change. Optical marker method was also used to detect interlaminar crack growth. The results show that the two-point probe measurements did not capture effectively the delamination propagation while the four-point probe measurement showed a promising sensing capability in terms of delamination propagation.
Piezoelectric Artificial Kelp for Energy Harvesting
Authors: Pankonien Alexander M. , Ounaies Zoubeida
Published: April 2011

This study focuses on a hydrokinetic energy harvesting system concept using piezoelectric materials. The Piezoelectric Active Kelp (PAK) system will consist of chemically inert piezoelectric polymers or piezoelectric ceramics manufactured into long flexible ribbons. The PAK system will convert the natural mechanical motions seen in kelp forests due to oceanic wave action, into electricity. As the periodic ocean currents, resulting from waves, pass over the PAK system, they cause the structure to oscillate back and forth. The piezoelectric materials will convert this mechanical motion directly into electrical power via the inverse piezoelectric effect. Large numbers of piezo-kelp ribbons would be mounted like forests on the ocean floor, producing a constant stream of smart grid power. PAK forest systems would also provide an artificial marine habitat while meeting the world’s demand for inexpensive and sustainable energy. Contrary to most forms of hydrokinetic energy harvesting system, the PAK system has no fast-moving parts or turbines and will be made of environmentally inert materials. The amount of power harvested by the PAK system depends upon the flow conditions, device configuration and size, and its piezoelectric material properties. Assuming specific flow conditions and fluid-structure interaction, this study will determine the optimal piezoelectric material to use, along with physical dimensions and layup configuration, to maximize the volumetric power density of the PAK system. The power generated by three common piezoelectric energy harvesting configurations: the unimorph, a homogeneous bimorph and a heterogeneous bimorph, will be compared for both a piezopolymer and a piezoceramic. Additionally, an appropriate figure-of-merit is also identified, based on the piezoelectric coefficient product (d31· g31) to compare the power production capabilities across materials.
Polymer Nanocomposites for Energy Storage Applications
Authors: Meddeb Amira B. , Ounaies Zoubeida
Published: April 2011

High dielectric polymer nanocomposites are promising candidates for energy storage applications. The main criteria of focus are high dielectric breakdown strength, high dielectric constant and low dielectric loss. In this study, we investigate the effect of the addition of TiO2 particles to PVDF matrix on the dielectric constant, breakdown and energy density of the system. The dispersion of the particles is qualified by scanning electron microscopy (SEM). The morphology of the composites is characterized by polarized light microscopy, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The dielectric properties are measured by a Novocontrol system with an Alpha analyzer. Finally, the breakdown measurements are carried out by a QuadTech hipot tester.
Pressure Oscillations in Adiabatic Compression
Authors: Stout Roland
Published: April 2011

After finding Moloney and McGarvey's1 modified adiabatic compression apparatus, I decided to insert this experiment into my physical chemistry laboratory at the last minute, replacing a problematic experiment. With insufficient time to build the apparatus, we placed a bottle between two thick textbooks and compressed it with a third textbook forced down from above. We discovered that approximately one in three trials exhibited a damped pressure oscillation after compression, as shown in Fig. 1 below, making it difficult to determine the true peak pressure. We discarded these trials and used only those without oscillation. I subsequently have had time to build a version of Moloney and McGarvin's apparatus. Using this apparatus, my students and I have recently performed numerous adiabatic compression trials with three different gases, with very few instances of oscillation.
Adding a Bit More History to Science Courses
Authors: DeBuvitz William
Published: April 2011

The usual science course is not meant to be a history course and the usual science book is not meant to be a history book. However, most science books do include some historical information. Unfortunately, the history part is usually so brief that it is far from interesting and often so oversimplified that it is totally wrong. Introductory physics books often present the history of physics as a dull, cold, logical progression of discoveries and theories. As a result, the student might think that one day Sir Isaac Newton said to himself, “I think I'll produce a theory of gravitation.” Then he sat down, wrote it all out, published it, received universal acclaim, and then was included in all physics textbooks. This view of science can look pretty dull and unappealing to students.
Ribozyme-Catalyzed Transcription of an Active Ribozyme
Authors: Wochner Aniela , Attwater James , Coulson Alan , Holliger Philipp
Published: April 2011

A functional RNA has been synthesized by an RNA enzyme from mononucleotide building blocks.
Nanometer-Thick Equilibrium Films: The Interface Between Thermodynamics and Atomistics
Authors: Baram Mor , Chatain Dominique , Kaplan Wayne D.
Published: April 2011

Model experiments show that nanometer-thick films at interfaces reduce interface energy and form an equilibrium state.
Ensemble Asteroseismology of Solar-Type Stars with the NASA Kepler Mission
Authors: Chaplin W. J. , Kjeldsen H. , Christensen-Dalsgaard J. , Basu S. , Miglio A. , Appourchaux T. , Bedding T. R. , Elsworth Y. , García R. A. , Gilliland R. L. , Girardi L. , Houdek G. , Karoff C. , Kawaler S. D. , Metcalfe T. S. , Molenda-Żakowicz J. , Monteiro M. J. P. F. G. , Thompson M. J. , Verner G. A. , Ballot J. , Bonanno A. , Brandão I. M. , Broomhall A.-M. , Bruntt H. , Campante T. L. , Corsaro E. , Creevey O. L. , Doğan G. , Esch L. , Gai N. , Gaulme P. , Hale S. J. , Handberg R. , Hekker S. , Huber D. , Jiménez A. , Mathur S. , Mazumdar A. , Mosser B. , New R. , Pinsonneault M. H. , Pricopi D. , Quirion P.-O. , Régulo C. , Salabert D. , Serenelli A. M. , Aguirre V. Silva , Sousa S. G. , Stello D. , Stevens I. R. , Suran M. D. , Uytterhoeven K. , White T. R. , Borucki W. J. , Brown T. M. , Jenkins J. M. , Kinemuchi K. , Van Cleve J. , Klaus T. C.
Published: April 2011

Measurements of 500 Sun-like stars show that their properties differ from those predicted by stellar population models.
Trans-Endocytosis of CD80 and CD86: A Molecular Basis for the Cell-Extrinsic Function of CTLA-4
Authors: Qureshi Omar S. , Zheng Yong , Nakamura Kyoko , Attridge Kesley , Manzotti Claire , Schmidt Emily M. , Baker Jennifer , Jeffery Louisa E. , Kaur Satdip , Briggs Zoe , Hou Tie Z. , Futter Clare E. , Anderson Graham , Walker Lucy S.K. , Sansom David M.
Published: April 2011

An inhibitory T cell receptor acts by stripping activating ligands off dendritic cells.
Plans Afoot to Extend Welcome Mat to More U.S.-Trained Science Grads
Authors: Mervis Jeffrey
Published: April 2011

Last week, a key congressional panel heard proposals to retain the "best and brightest" foreign students without disadvantaging U.S. workers. But the approach of the 2012 elections means the political window of opportunity won't stay open for very long.
Is unhealthy substance use associated with failure to receive cancer screening and flu vaccination? A retrospective cross-sectional study
Authors: Lasser Karen E , Kim Theresa W , Alford Daniel P , Cabral Howard , Saitz Richard , Samet Jeffrey H
Published: April 2011

Objective

To compare cancer screening and flu vaccination among persons with and without unhealthy substance use.

Design

The authors analysed data from 4804 women eligible for mammograms, 4414 eligible for Papanicolou (Pap) smears, 7008 persons eligible for colorectal cancer (CRC) screening and 7017 persons eligible for flu vaccination. All patients were screened for unhealthy substance use. The main outcome was completion of cancer screening and flu vaccination.

Results

Among the 9995 patients eligible for one or more of the preventive services of interest, 10% screened positive for unhealthy substance use. Compared with women without unhealthy substance use, women with unhealthy substance use received mammograms less frequently (75.4% vs 83.8%; p<0.0001), but Pap smears no less frequently (77.9% vs 78.1%). Persons with unhealthy substance use received CRC screening no less frequently (61.7% vs 63.4%), yet received flu vaccination less frequently (44.7% vs 50.4%; p=0.01). In multivariable analyses, women with unhealthy substance use were less likely to receive mammograms (adjusted odds ratio 0.68; 95% CI 0.52 to 0.89), and persons with unhealthy substance use were less likely to receive flu vaccination (adjusted odds ratio 0.81; 95% CI 0.67 to 0.97).

Conclusions

Unhealthy substance use is a risk factor for not receiving all appropriate preventive health services.
Delay analysis considering production rate
Authors: Lee Jae-Seob , Diekmann James E.
Published: April 2011

There are various methods offered in construction literature for determining the schedule impact resulting from delays and interruptions. Previous scheduling technique makes the assumption that the relationship between time and the number of units produced is linear. Accordingly, progress is assumed to be equally distributed along the activities’ durations. Often this assumption does not reflect the real situation for the progress of construction activities. Some activities are naturally nonlinear and others exhibit nonlinear progress. To insure reality and reasonableness, delay analysis must allow for nonlinear production rates as well as linear production rates in the delayed activities. Therefore, there is a need for a delay analysis method that incorporates the varying rate of production for the delayed activities. This paper proposes a delay analysis method that can rationally apportion the concurrent delay with consideration of the nonlinear production rates of activities in construction projects. A simple case study has been implemented to demonstrate the accuracy and usefulness of the proposed delay analysis method. This research is useful for both researchers and practitioners for the case including the varying productivity due to delays and interruptions and allows transparent and rational analysis on concurrent delay to facilitate claim analysis.
An analysis of the US decking materials market: perceptual mapping approach
Authors: Ganguly Indroneil , Eastin Ivan , MacLachlan Douglas
Published: April 2011

This paper analyzes the product positioning and market demand of preservative-treated, naturally decay-resistant, and composite decking materials in the United States using an innovative perceptual mapping technique. Market analysis using perceptual mapping is generally used for end-user market scenarios for strategic planning. This paper establishes that the perceptual mapping technique can also be a valuable tool for analyzing the US decking products market, which is predominantly a business-to-business (B2B) market. Using perceptual mapping of the US decking market, this paper proposes a method for incorporating market demand density on a perceptual space, incorporating a kernel regression based nonparametric demand distribution. Representation of products and demand distribution on the same perceptual space in the proposed mapping technique enables simultaneous visualization of product positioning and demand density distribution in the marketplace. The mapping results obtained in this paper will enable business decision makers in the US decking industry to strategically position their offerings based on existing product positioning and market demand distribution. The data used for the study were collected through a national survey of 368 professional deck builders and homebuilders.
Forest developmental trajectories in mountain pine beetle disturbed forests of Rocky Mountain National Park, Colorado
Authors: Diskin Matthew , Rocca Monique E. , Nelson Kellen N. , Aoki Carissa F. , Romme W.H.
Published: April 2011

A mountain pine beetle (Dendroctonus ponderosae Hopkins) epidemic has caused widespread mortality of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) trees across western North America,. We characterized the initial effects of beetle-induced mortality on forest structure and composition in Rocky Mountain National Park, Colorado. In 2008, we surveyed stand structure and tree species composition across lodgepole pine dominated forests in the western portion of the Park. We defined five lodgepole pine forest types to describe variability in pre-epidemic forest conditions. This forested landscape appears to be resilient to the effects of the beetle. Surviving trees, including both canopy trees and saplings, were plentiful in most of the post-epidemic forests, even after accounting for anticipated future mortality. Subalpine fir (Abies lasiocarpa (Hook.) Nutt.), Engelmann spruce (Picea engelmannii Parry ex Engelm.), and aspen (Populus tremuloides Michx.) had modestly higher relative abundances after the epidemic. Lodgepole pine remained the dominant species on approximately 85% of the landscape. The impact of the outbreak on forest structure and composition varied considerably among the five forest types, suggesting that post-epidemic forest developmental trajectories will vary according to pre-outbreak stand characteristics. Active management efforts to regenerate lodgepole pine forests, e.g., tree planting, will likely not be necessary on this landscape.
Survival and growth response of white spruce stock types to site preparation in Alaska
Authors: Youngblood Andrew , Cole Elizabeth , Newton Michael
Published: April 2011

To identify suitable methods for reforestation, we evaluated the interacting effects of past disturbance, stock types, and site preparation treatments on white spruce (Picea glauca (Moench) Voss) seedling survival and growth across a range of sites in Alaska. Replicated experiments were established in five regions. At each site, two complete installations differed in time since disturbance: “new” units were harvested immediately before spring planting and “old” units were harvested at least 3 years before planting. We compared mechanical scarification before planting, broadcast herbicide application during the fall before planting, and no site preparation with 1-year-old container-grown seedlings from two sources, 2-year-old bare-root transplants from two sources, and 3-year-old bare-root transplants. Seedlings were followed for 11 years on most sites. Based on meta-analyses, seedling survival increased 10% with herbicide application and 15% with mechanical scarification compared with no site preparation. Scarification and herbicide application increased seedling height by about 28% and 35%, respectively, and increased seedling volume by about 86% and 195%, respectively, compared with no site preparation. Soil temperature did not differ among site preparation methods after the first 7 years. Results suggest that white spruce stands may be successfully restored through a combination of vegetation control and use of quality planting stock.
VARIOUS FORMS OF BRST SYMMETRY IN ABELIAN 2-FORM GAUGE THEORY
Authors: RAI SUMIT KUMAR , MANDAL BHABANI PRASAD
Published: April 2011

We derive the various forms of BRST symmetry using Batalin–Fradkin–Vilkovisky approach in the case of Abelian 2-form gauge theory. We show that the so-called dual BRST symmetry is not an independent symmetry but the generalization of BRST symmetry obtained from the canonical transformation in the bosonic and ghost sector. We further obtain the new forms of both BRST and dual-BRST symmetry by making a general transformation in the Lagrange multipliers of the bosonic and ghost sector of the theory.
REGIME SWITCHING TERM STRUCTURE MODEL UNDER PARTIAL INFORMATION
Authors: FUTAMI HIDENORI
Published: April 2011

In this study, we attempt to calculate the term structure of the interest rate under partial information using a model in which the mean reversion level of the short rate changes in accordance with a regime shift in the economy. Under partial information, an investor observes the history of only the short rate and not a regime shift; hence, calculating the term structure of the interest rate is reduced to the problem of filtering the current regime from observable short rates. Therefore, we calculate it using the filtering theory that estimates a stochastic process from noisy observations, and investigate the effects of the regime shift under partial information on the market price of risk and the volatility of a bond price compared with those under full information, in which the regime is assumed to be observable. We find that, under partial information, the regime-shift risk converts into the diffusion risk. As a result, we find that both the market price of diffusion risk and the volatility of a bond price under partial information become stochastic, even though these under full information are constant.
MONTE CARLO CALCULATION FOR CATHODOLUMINESCENCE OF AlGaAs/GaAs NANOSTRUCTURE
Authors: AOUATI REDHA , NOUIRI ABDELKADER
Published: April 2011

The cathodoluminescence technique (CL) performed in the Scanning Electron Microscope (SEM) offers opto-electronic characterization of some nanostructures and it is a powerful tool for studying the compositional variation or band structure of three-dimensional microscale or nanoscale structures. The major problem of the CL technique is the difficulty of high spatial resolution of the low-dimensional structure. In the present paper we propose a simple Monte Carlo calculation model to describe the interaction of electron beam with Al x Ga 1-x As - GaAs nanostructure. This model takes into account the confinement phenomenon in the quantum well by an easy method. The influence of different parameters such as the thickness of barriers, Al mole fraction (x), and the diffusion length are studied. The carrier excess generated during the collision of the incident electron with the atoms of the material (random walk) is calculated taking into account the confinement phenomenon within the quantum well. The radiative recombination of electron–hole pairs is collected as a light (CL signal).
STRUCTURAL AND PHOTOLUMINESCENCE PROPERTIES OF Co:ZnO NANOCRYSTALLINE POWDERS
Authors: SAGAR R. VIDYA , BUDDHUDU S.
Published: April 2011

In the present study, results concerning the structural and photoluminescence properties of ZnO:Co nanocrystalline powders synthesized using an oxalate precursor decomposition method are reported. The XRD profiles reveal that all the samples are in hexagonal wurtzite structure. The values of the lattice parameters a and c are found to be decreasing linearly with Co content change. Surface morphological studies have also been carried out using SEM and TEM analyses. The origin of photoluminescence from ZnO and Co:ZnO has been reported.
SYNTHESIS AND CHARACTERIZATION OF HEXAMETHYLENE TETRAMINE (HMTA) CAPPED CdS NANOPARTICLES BY HYDROTHERMAL METHOD
Authors: CHINNU M. KARL , SARAVANAN L. , JAYAVEL R. , RAGHAVAN C. M. , ANAND K. VIJAI , KUMAR R. MOHAN , ALAGESAN T.
Published: April 2011

Cadmium sulfide nanoparticles have been synthesized by hydrothermal method using cadmium acetate, thiosemicarbazide, and sodium hydroxide as precursors with hexamethylene tetramine as the surfactant. From the X-ray diffraction analysis, it is observed that synthesized CdS nanoparticles show cubic phase. The presence of HMTA in CdS was confirmed by FT-IR analysis. The bandgap value of CdS nanostructure has been estimated by DRS–UV-Visible spectral analysis. The formation of flower-like nanoclusters was observed using scanning electron microscopy (SEM). The application of CdS nanoparticles in photocatalytic degradation was also studied.
A REVIEW OF ASSEMBLED POLYACRYLONITRILE-BASED CARBON NANOFIBER PREPARED ELECTROSPINNING PROCESS
Authors: MATARAM A. , ISMAIL A. F. , Abdullah M. S. , Ng B. C. , MATSUURA T.
Published: April 2011

Electrospinning is a very simple and versatile process by which polymer nanofibers with diameters ranging from a few nanometers to several micrometers can be produced using an electrostatically driven jet of polymer solution (or polymer melt). Significant progress has been made in this process throughout the last decade and the resultant nanostructures have been exploited to a wide range of applications. An important feature of the electrospinning process is that electrospinning nanofibers are produced in atmospheric air and at room temperature. This paper reviews the assembled polyacrylonitrile (PAN)-based carbon nanofibers with various processing parameters such as electrical potential, distance between capillary and collector drum, solution flow rate (dope extrusion rate), and concentration of polymer solution. The average fiber diameter would increase with increasing concentration of the polymer solution and the flow rate. Therefore, the screen distance could also increase but the average electrical potential of the fibers diameter decreases. Electrospinning process can be conducted at higher electrical potentials, lower flow rate, nearer screen distance, and higher concentrations of dope.
A STAGE-STRUCTURED PREDATOR–PREY MODEL WITH DENSITY-DEPENDENT MATURATION DELAY
Authors: AGARWAL MANJU , DEVI SAPNA
Published: April 2011

In this paper, a stage-structured predator–prey model is proposed and analyzed with density-dependent maturation delay. We studied the dynamics of our model analytically and obtained conditions which influence the positivity and boundedness of all populations. Criteria for the existence of a non-trivial equilibrium and conditions for the uniqueness of this equilibrium are given. A linearized analysis on the equilibria, which is algebraically very complicated in the case of non-trivial equilibrium, is carried out. We proved that the system is globally asymptotically stable in the situation when non-trivial equilibrium does not exist. To accomplish our all analytical findings and to investigate the effect of density-dependent maturation delay on the system behavior, we presented a numerical simulation. It is concluded that variations in parameter, which we introduce in the system to observe the effect of density-dependent maturation delay, produces significant quantitative changes in system behavior and also qualitative changes in the behavior of immature predator population.
PERIODICITY AND STABILITY IN RECURRENT CELLULAR NEURAL NETWORKS WITH IMPULSIVE EFFECTS
Authors: GU HAIBO , JIANG HAIJUN , TENG ZHIDONG
Published: April 2011

In this paper, the exponential stability analysis problem is considered for a class of impulsive recurrent cellular neural networks (IRCNNs) with time-varying delays. Without assuming the boundedness on the activation functions, some sufficient conditions are derived for checking the existence and exponential stability of periodic solution for this system by using Mawhin's continuation theorem of coincidence degree theory and constructing suitable Lyapunov functional. It is believed that these results are significant and useful for the design and applications of IRCNNs. Finally, an example with numerical simulation is given to show the effectiveness of the proposed method and results.
CROSS-DIFFUSION INDUCED INSTABILITY IN LVLEV–TANNER MODEL
Authors: GAN WENZHEN , ZHU PENG , BAO JIE
Published: April 2011

A Lvlev–Tanner model with cross-diffusion is considered. We analyze the positive uniform steady state and obtain conditions on the parameter values such that the homogeneous steady state is locally asymptotically stable both in the related ODE system and in the PDE system with self-diffusion. Once also cross-diffusion is considered in the model, the uniform steady state is shown to be unstable under some conditions. Numerical simulations are also presented.
NEW PARAMETER FOR DESCRIBING AND ANALYZING THE OPTICAL-ANISOTROPIC PROPERTIES OF BIOLOGICAL TISSUES
Authors: USHENKO Yu. A. , TELENGA O. I. , PERESUNKO A. P. , NUMAN O. K.
Published: April 2011

To characterize the degree of similarity inherent to parameters of the optically uniaxial birefringent protein-fibril networks of biological tissues, a new parameter — complex degree of mutual anisotropy — has been offered. The technique of polarization measuring the coordinate distributions of the complex degree of mutual anisotropy of biological tissues has been developed. It has been shown that statistical approach to the analysis of complex degree of mutual anisotropy distributions for biological tissues in various morphological and physiological states and for different optical thicknesses appears to be more sensitive and efficient in differentiation of physiological state, as compared to investigations of complex degree of mutual polarization in the corresponding laser images.
MUSCLE RESEARCH WORK WITH BRITTON CHANCE FROMIN VIVOMAGNETIC RESONANCE SPECTROSCOPY TO NEAR-INFRARED SPECTROSCOPY
Authors: HAMAOKA TAKAFUMI , MCCULLY KEVIN K.
Published: April 2011

Britton Chance has pioneered magnetic resonance spectroscopy (MRS) and near-infrared (NIR) spectroscopy (NIRS) as noninvasive methods for measuring muscle metabolism in vivo from the late 1970s. This review honoring Britton Chance will highlight the progress that has been made in developing and utilizing MRS and NIRS technologies for evaluating skeletal muscle O2dynamics and energetics. Adaptation of MRS and NIRS technology has focused on the validity and reliability of the measurements and extending the methods in physiological and clinical research. Britton Chance has conducted MRS and NIRS research on elite athletes and a number of chronic health conditions, including patients with chronic heart failure, peripheral vascular disease, and neuromuscular myopathies. As MRS and NIRS technologies are practical and useful for measuring human muscle metabolism, we will strive to continue Chance's legacy by advancing muscle MRS and NIRS studies.
Inconsistent detection of changes in cerebral blood volume by near infrared spectroscopy in standard clinical tests
Authors: Canova D. , Roatta S. , Bosone D. , Micieli G.
Published: April 2011

The attractive possibility of near infrared spectroscopy (NIRS) to noninvasively assess cerebral blood volume and oxygenation is challenged by the possible interference from extracranial tissues. However, to what extent this may affect cerebral NIRS monitoring during standard clinical tests is ignored. To address this issue, 29 healthy subjects underwent a randomized sequence of three maneuvers that differently affect intra- and extracranial circulation: Valsalva maneuver (VM), hyperventilation (HV), and head-up tilt (HUT). Putative intracranial (“i”) and extracranial (“e”) NIRS signals were collected from the forehead and from the cheek, respectively, and acquired together with cutaneous plethysmography at the forehead (PPG), cerebral blood velocity from the middle cerebral artery, and arterial blood pressure. Extracranial contribution to cerebral NIRS monitoring was investigated by comparing Beer-Lambert (BL) and spatially resolved spectroscopy (SRS) blood volume indicators [the total hemoglobin concentration (tHb) and the total hemoglobin index, (THI)] and by correlating their changes with changes in extracranial circulation. While THIe and tHbe generally provided concordant indications, tHbi and THIi exhibited opposite-sign changes in a high percentage of cases (VM: 46%; HV: 31%; HUT: 40%). Moreover, tHbi was correlated with THIi only during HV ( P < 0.05), not during VM and HUT, while it correlated with PPG in all three maneuvers ( P < 0.01). These results evidence that extracranial circulation may markedly affect BL parameters in a high percentage of cases, even during standard clinical tests. Surface plethysmography at the forehead is suggested as complementary monitoring helpful in the interpretation of cerebral NIRS parameters.
Model-based characterization of ventilatory stability using spontaneous breathing
Authors: Nemati Shamim , Edwards Bradley A. , Sands Scott A. , Berger Philip J. , Wellman Andrew , Verghese George C. , Malhotra Atul , Butler James P.
Published: April 2011

Cyclic ventilatory instabilities are widely attributed to an increase in the sensitivity or loop gain of the chemoreflex feedback loop controlling ventilation. A major limitation in the conventional characterization of this feedback loop is the need for labor-intensive methodologies. To overcome this limitation, we developed a method based on trivariate autoregressive modeling using ventilation, end-tidal Pco2and Po2; this method provides for estimation of the overall “loop gain” of the respiratory control system and its components, chemoreflex gain and plant gain. Our method was applied to recordings of spontaneous breathing in 15 anesthetized, tracheostomized, newborn lambs before and after administration of domperidone (a dopamine D2-receptor antagonist that increases carotid body sensitivity). We quantified the known increase in hypoxic ventilatory sensitivity in response to domperidone; controller gain for O2increased from 0.06 (0.03, 0.09) l·min−1·mmHg−1to 0.09 (0.08, 0.13) l·min−1·mmHg−1; median (interquartile-range). We also report that domperidone increased the loop gain of the control system more than twofold [0.14 (0.12, 0.22) to 0.40 (0.15, 0.57)]. We observed no significant changes in CO2controller gain, or plant gains for O2and CO2. Furthermore, our estimate of the cycle duration of periodic breathing compared favorably with that observed experimentally [measured: 7.5 (7.2, 9.1) vs. predicted: 7.9 (7.0, 9.2) breaths]. Our results demonstrate that model-based analysis of spontaneous breathing can 1) characterize the dynamics of the respiratory control system, and 2) provide a simple tool for elucidating an individual's propensity for ventilatory instability, in turn allowing potential therapies to be directed at the underlying mechanisms.
Itk: The Rheostat of the T Cell Response
Authors: Grasis Juris A. , Tsoukas Constantine D.
Published: April 2011

The nonreceptor tyrosine kinase Itk plays a key role in TCR-initiated signaling that directly and significantly affects the regulation of PLCγ1 and the consequent mobilization of Ca2+. Itk also participates in the regulation of cytoskeletal reorganization as well as cellular adhesion, which is necessary for a productive T cell response. The functional cellular outcome of these molecular regulations by Itk renders it an important mediator of T cell development and differentiation. This paper encompasses the structure of Itk, the signaling parameters leading to Itk activation, and Itk effects on molecular pathways resulting in functional cellular outcomes. The incorporation of these factors persuades one to believe that Itk serves as a modulator, or rheostat, critically fine-tuning the T cell response.
Characterization of KRAS Rearrangements in Metastatic Prostate Cancer
Authors: Wang Xiao-Song , Shankar Sunita , Dhanasekaran Saravana M. , Ateeq Bushra , Sasaki Atsuo T. , Jing Xiaojun , Robinson Daniel , Cao Qi , Prensner John R. , Yocum Anastasia K. , Wang Rui , Fries Daniel F. , Han Bo , Asangani Irfan A. , Cao Xuhong , Li Yong , Omenn Gilbert S. , Pflueger Dorothee , Gopalan Anuradha , Reuter Victor E. , Kahoud Emily Rose , Cantley Lewis C. , Rubin Mark A. , Palanisamy Nallasivam , Varambally Sooryanarayana , Chinnaiyan Arul M.
Published: April 2011

Using an integrative genomics approach called amplification breakpoint ranking and assembly analysis, we nominated KRAS as a gene fusion with the ubiquitin-conjugating enzyme UBE2L3 in the DU145 cell line, originally derived from prostate cancer metastasis to the brain. Interestingly, analysis of tissues revealed that 2 of 62 metastatic prostate cancers harbored aberrations at the KRAS locus. In DU145 cells, UBE2L3-KRAS produces a fusion protein, a specific knockdown of which attenuates cell invasion and xenograft growth. Ectopic expression of the UBE2L3-KRAS fusion protein exhibits transforming activity in NIH 3T3 fibroblasts and RWPE prostate epithelial cells in vitro and in vivo. In NIH 3T3 cells, UBE2L3-KRAS attenuates MEK/ERK signaling, commonly engaged by oncogenic mutant KRAS, and instead signals via AKT and p38 mitogen-activated protein kinase (MAPK) pathways. This is the first report of a gene fusion involving the Ras family, suggesting that this aberration may drive metastatic progression in a rare subset of prostate cancers.

Significance: This is the first description of an oncogenic gene fusion of KRAS, one of the most studied proto-oncogenes. KRAS rearrangement may represent the driving mutation in a rare subset of metastatic prostate cancers, emphasizing the importance of RAS-RAF-MAPK signaling in this disease. Cancer Discovery; 1(1); 35–43. © 2011 AACR.

Read the Commentary on this article by Edgren et al., p. 12

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Adult Patients with Well-Controlled Phenylketonuria Tolerate Incidental Additional Intake of Phenylalanine
Authors: van Rijn Margreet , Hoeksma Marieke , Sauer Pieter J.J. , Modderman Pim , Reijngoud Dirk-Jan , van Spronsen Francjan J.
Published: April 2011

Background/Aims: In patients with phenylketonuria (PKU), target ranges of blood phenylalanine (Phe) concentrations have been tightened in order to improve long-term outcomes. We investigated day-to-day and week-to-week variations in blood Phe concentration and the effect of an additional Phe load. Methods: We performed a longitudinal study in 6 adult PKU patients. The study was divided in five 7-day periods: 1 period without any intervention (period I) and 4 periods with a Phe load on day 3 equivalent to 100% (periods II and III) and to 200% (periods IV and V) of each patient’s individual daily Phe intake. Phe loading was given as encapsulated L-Phe. Blood spots to measure blood Phe concentration were taken each morning before breakfast in all periods. Results: Day-to-day and week-to-week blood Phe concentrations varied considerably with and without intervention in Phe intake. Equal loads of Phe did not result in comparable effects in blood Phe concentrations in all patients. In periods II–IV, mean blood Phe concentrations of days 1–3 (pre-load) were not significantly different from days 4–7 (post-load). The 200% load resulted in a significantly larger variation. Conclusion: These results showed that patients with well-controlled PKU can incidentally tolerate 100% – and in some cases 200% – of their normal daily Phe intake.
Folate and Homocysteine in the Cerebrospinal Fluid of Patients with Alzheimer’s Disease or Dementia: A Case Control Study
Authors: Smach Mohamed Ali , Jacob Nelly , Golmard Jean-Louis , Charfeddine Bassem , Lammouchi Turkia , Ben Othman Leila , Dridi Hedi , Bennamou Soufien , Limem Khalifa
Published: April 2011

Background: Amyloid deposition in the brain is an early event in Alzheimer’s disease (AD), but a dysfunction of the blood-brain barrier or a disturbance in the metabolism of folate and homocysteine (Hcy) may affect the development of dementia. We investigated if the concentrations of folate and Hcy would be modified in cerebrospinal fluid (CSF) of clinically diagnosed AD patients. Methods: We included 70 AD patients, 33 patients with another type of dementia (nAD) and 30 age-matched control subjects. Plasma Hcy was assayed as well as Hcy, folate, Aβ1-42 and T-tau in CSF. We used ANOVAs for comparison between groups, and then pairwise comparisons by Wilcoxon tests with Bonferroni-corrected p values. Correlations were tested with the Spearman’s rank test. Results: Levels of Aβ1-42, T-tau and folates in CSF were significantly different between groups, but not Hcy. In addition, the average folate in CSF was lower in AD patients compared with controls (18.7 ± 2.4 vs. 20.3 ± 1.7 nmol/l, Bonferroni-corrected p value < 0.02). There was no correlation between Aβ1-42 or T-tau and folate or Hcy in CSF, regardless of the group. In the AD group, there was a significant inverse correlation between Hcy and folate in CSF (ρ = –0.63, p < 0.0001), whereas in the nAD group, a significant correlation was found for Hcy between plasma and CSF (ρ = 0.59, p < 0.0005). Conclusion: The concentration of folate in CSF was found to be decreased in AD patients. These findings support the hypothesis of a possible role of folate in the onset or worsening of AD.
Imaging the Endothelial Glycocalyx In Vitro by Rapid Freezing/Freeze Substitution Transmission Electron Microscopy
Authors: Ebong Eno E. , Macaluso Frank P. , Spray David C. , Tarbell John M.
Published: April 2011

Objective—

Recent publications questioned the validity of endothelial cell (EC) culture studies of glycocalyx (GCX) function because of findings that GCX in vitro may be substantially thinner than GCX in vivo. The assessment of thickness differences is complicated by GCX collapse during dehydration for traditional electron microscopy. We measured in vitro GCX thickness using rapid freezing/freeze substitution (RF/FS) transmission electron microscopy (TEM), taking advantage of the high spatial resolution provided by TEM and the capability to stably preserve the GCX in its hydrated configuration by RF/FS.

Methods and Results—

Bovine aortic EC (BAEC) and rat fat pad EC were subjected to conventional or RF/FS-TEM. Conventionally preserved BAEC GCX was ≈0.040 μm in thickness. RF/FS-TEM revealed impressively thick BAEC GCX of ≈11 μm and rat fat pad EC GCX of ≈5 μm. RF/FS-TEM also discerned GCX structure and thickness variations due to heparinase III enzyme treatment and extracellular protein removal, respectively. Immunoconfocal studies confirmed that the in vitro GCX is several micrometers thick and is composed of extensive and well-integrated heparan sulfate, hyaluronic acid, and protein layers.

Conclusion—

New observations by RF/FS-TEM reveal substantial GCX layers on cultured EC, supporting their continued use for fundamental studies of GCX and its function in the vasculature.