bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Experimental System for the Extended Application of Cyclic Hydrostatic Pressure to Cell Culture
Authors: Maul Timothy M. , Hamilton Douglas W. , Nieponice Alejandro , Soletti Lorenzo , Vorp David A.
Published: January 2007

Mechanical forces have been shown to be important stimuli for the determination and maintenance of cellular phenotype and function. Many cells are constantly exposed in vivo to cyclic pressure, shear stress, and/or strain. Therefore, the ability to study the effects of these stimuli in vitro is important for understanding how they contribute to both normal and pathologic states. While there exist commercial as well as custom-built devices for the extended application of cyclic strain and shear stress, very few cyclic pressure systems have been reported to apply stimulation longer than 48h. However, pertinent responses of cells to mechanical stimulation may occur later than this. To address this limitation, we have designed a new cyclic hydrostatic pressure system based upon the following design variables: minimal size, stability of pressure and humidity, maximal accessibility, and versatility. Computational fluid dynamics (CFD) was utilized to predict the pressure and potential shear stress within the chamber during the first half of a 1.0Hz duty cycle. To biologically validate our system, we tested the response of bone marrow progenitor cells (BMPCs) from Sprague Dawley rats to a cyclic pressure stimulation of 120∕80mm Hg, 1.0Hz for 7days. Cellular morphology was measured using Scion Image, and cellular proliferation was measured by counting nuclei in ten fields of view. CFD results showed a constant pressure across the length of the chamber and no shear stress developed at the base of the chamber where the cells are cultured. BMPCs from Sprague Dawley rats demonstrated a significant change in morphology versus controls by reducing their size and adopting a more rounded morphology. Furthermore, these cells increased their proliferation under cyclic hydrostatic pressure. We have demonstrated that our system imparts a single mechanical stimulus of cyclic hydrostatic pressure and is capable of at least 7days of continuous operation without affecting cellular viability. Furthermore, we have shown for the first time that BMPCs respond to cyclic hydrostatic pressure by alterations in morphology and increased proliferation.
A Theoretical Framework to Analyze Bend Testing of Soft Tissue
Authors: Nicosia Mark A.
Published: January 2007

It has been hypothesized that repetitive flexural stresses contribute to the fatigue-induced failure of bioprosthetic heart valves. Although experimental apparatuses capable of measuring the bending properties of biomaterials have been described, a theoretical framework to analyze the resulting data is lacking. Given the large displacements present in these bending experiments and the nonlinear constitutive behavior of most biomaterials, such a formulation must be based on finite elasticity theory. We present such a theory in this work, which is capable of fitting bending moment versus radius of curvature experimental data to an arbitrary strain energy function. A simple finite element model was constructed to study the validity of the proposed method. To demonstrate the application of the proposed approach, bend testing data from the literature for gluteraldehyde-fixed bovine pericardium were fit to a nonlinear strain energy function, which showed good agreement to the data. This method may be used to integrate bending behavior in constitutive models for soft tissue.
Altered Multiaxial Mechanical Properties of the Porcine Anterior Lens Capsule Cultured in High Glucose
Authors: Pedrigi R. M. , Staff E. , David G. , Glenn S. , Humphrey J. D.
Published: January 2007

Hyperglycemia can alter the mechanical properties of tissues through the formation of advanced glycation endproducts in matrix proteins that have long half-lives. We used a custom experimental system and subdomain finite element method to quantify alterations in the regional multiaxial mechanical properties of porcine lens capsules that were cultured for 8 or 14 weeks in high glucose versus control media. Findings revealed that high glucose significantly stiffened the capsules in both the circumferential and the meridional directions, but it did not affect the known regional variations in anisotropy. Such information could be important in the design of both improved clinical procedures and intraocular implants for diabetic patients.
Coherent Thermal Emission From Modified Periodic Multilayer Structures
Authors: Lee B. J. , Zhang Z. M.
Published: January 2007

Enhancement of thermal emission and control of its direction are important for applications in optoelectronics and energy conversion. A number of structures have been proposed as coherent emission sources, which exhibit a large emissivity peak within a narrow wavelength band and at a well-defined direction. A commonly used structure is the grating, in which the excited surface polaritons or surface waves are coupled with propagating waves in air, resulting in coherent emission for p polarization only. One-dimensional photonic crystals can also support surface waves and may be modified to construct coherent emission sources. The present study investigates coherent emission from a multilayer structure consisting of a SiC film coated atop a dielectric photonic crystal (PC). By exciting surface waves at the interface between SiC and the PC, coherent emission is predicted for both p and s polarizations. In addition to the excitation of surface waves, the emission from the proposed multilayer structure can be greatly enhanced by the cavity resonance mode and the Brewster mode.
Change in Radiative Optical Properties of Ta2O5 Thin Films due to High-Temperature Heat Treatment
Authors: Chandrasekharan Ramesh , Prakash Shaurya , Shannon Mark A. , Masel R. I.
Published: January 2007

Thin films (0.85μm, 3μm) of Ta2O5 deposited on Si and SiO2 were heated to 900°C. Their reflectance in the infrared was measured using a Fourier transform infrared spectrometer equipped with a multiple angle reflectometer before and after exposure to the high-temperature heat treatment. An interfacial layer (TaSixOy) formed by the diffusion of Si from the substrate into the deposited film was observed using Auger depth profiling, and the effect of this interfacial layer on the reflectance was measured. Using a least squares optimization technique coupled with an optical admittance algorithm, the multiple angle reflectance data were used to calculate the optical constants of the as deposited Ta2O5 film, crystalline Ta2O5, and the interfacial layer in the 1.6 to 10μm range. The interfacial layer formed due to exposure to high temperature was found to be more absorptive than the crystalline Ta2O5.
Energy Transfer to Optical Microcavities With Waveguides
Authors: Guo Zhixiong , Quan Haiyong
Published: January 2007

Micro/nanoscale radiation energy transfer is investigated in optical microcavity and waveguide coupling structures working on whispering-gallery mode optical resonances. The finite element method is employed for solving the Helmholtz equations that govern the energy transfer and time-harmonics electromagnetic (EM) wave propagation. The maximum element size concept is introduced for the numerically sensitive subdomains where local mesh refining is needed because of the presence of intensified EM fields. The results show that the energy storage capability of a resonant microcavity is predominantly determined by the cavity size. The stored energy in the 10μm diameter microcavity considered is several orders of magnitude larger than that in the 2μm diameter microcavity. The gap between a microcavity and its light-delivery waveguide has a substantial effect on the energy coupling from the waveguide to the microcavity and consequently influences significantly energy storage in the microcavity. An optimal gap is found for maximum energy storage and most efficient energy coupling. This optimal gap dimension depends not only on the configurations of the microcavity and waveguide, but also on the resonance wavelength. With increasing gap the quality factor increases exponentially and quickly saturates as the gap approaches to one wavelength involved. The submicron/nanoscale gap is crucial for generating quality resonances as well as for efficient energy transfer and coupling.
Modeling the Radiative Properties of Microscale Random Roughness Surfaces
Authors: Fu Kang , Hsu Pei-feng
Published: January 2007

The radiative properties of engineering surfaces with microscale surface texture or topography (patterned or random roughness and coating or multi-layer) are of fundamental and practical importance. In the rapid thermal processing or arc/flash-assisted heating of silicon wafers, the control of thermal energy deposition through radiation and the surface temperature measurement using optical pyrometry require in-depth knowledge of the surface radiative properties. These properties are temperature, wavelength, doping level, and surface topography dependent. It is important that these properties can be modeled and predicted with high accuracy to meet very stringent temperature control and monitor requirements. This study solves the Maxwell equations that describe the electromagnetic wave reflection from the one-dimensional random roughness surfaces. The surface height conforms to the normal distribution, i.e., a Gaussian probability density function distribution. The numerical algorithm of Maxwell equations’ solution is based on the well-developed finite difference time domain (FDTD) scheme and near-to-far-field transformation. Various computational modeling issues that affect the accuracy of the predicted properties are quantified and discussed. The model produces the bi-directional reflectivity and is in good agreement with the ray tracing and integral equation solutions. The predicted properties of a perfectly electric conductor and silicon surfaces are compared and discussed.
Thermal Radiative Transport Enhancement via Electromagnetic Surface Modes in Microscale Spherical Regions Bounded by Silicon Carbide
Authors: Hammonds James S.
Published: January 2007

A Green function approach is used with the fluctuation-dissipation theorem to develop a qualitative theoretical model of radiation heat transfer across an evacuated microscale spherical geometry bounded by silicon carbide. The appropriate scalar Green function is presented by employing an impedance boundary condition to describe the electromagnetic spherical interface condition and thus capture the surface modes. This work shows that the spherical boundary can result in spectral conditions for surface mode excitation that depend not only on the dielectric function, but on the sphere radius as well. The surface modes are shown to enhance the radiation significantly and are attributed to surface phonon polariton modes excited at the interface, and surface modes excited by the mechanism of total internal reflection.
Reliability Optimization With Mixed Continuous-Discrete Random Variables and Parameters
Authors: Gunawan Subroto , Papalambros Panos Y.
Published: January 2007

Engineering design problems frequently involve a mix of both continuous and discrete random variables and parameters. However, most methods in the literature deal with only the continuous or the discrete type, but not both. In particular, no method has yet addressed problems for which the random components (variables and∕or parameters) are categorically discrete. This paper develops an efficient optimization method for problems involving mixed continuous-discrete random variables and parameters. The method reduces the number of function evaluations performed by systematically filtering the discrete combinations used for estimating reliability based on their importance. This importance is assessed using the spatial distance from the feasible boundary and the probability of the discrete components. The method is demonstrated in examples and is shown to be very efficient with only small errors.
Patterned Bootstrap: A New Method That Gives Efficiency for Some Precision Position Synthesis Problems
Authors: Luo Zhenjun , Dai Jian S.
Published: January 2007

This paper presents a heuristic global convergence method, termed as patterned bootstrap (PB), for solving systems of equations. In the PB method, multiple directions starting from a given point are searched. A number of intermediate underdetermined systems are selected and solved sequentially using classic globally convergence methods. Numerical experiments demonstrate that the PB method outperforms Levenberg-Marquardt method on solving a number of challenging synthesis problems in no more than 18 variables. On the other hand, Levenberg-Marquardt method normally outperforms the PB method on solving several systems of equations in 30 variables which are derived from the five precision-position motion generation problem of spatial RRR manipulators. In the paper, tunneling functions are also introduced to exclude degenerated solution sets in several synthesis problems. The research reveals that appropriate numerical methods and synthesis equations can be chosen for obtaining most solutions efficiently and provide a complete solution set of a precision position synthesis problem within a domain of interest.
A Static and Dynamic Model of Geared Transmissions by Combining Substructures and Elastic Foundations—Applications to Thin-Rimmed Gears
Authors: Bettaïeb M. N. , Velex P. , Ajmi M.
Published: January 2007

The present work is aimed at predicting the static and dynamic behavior of geared transmissions comprising flexible components. The proposed model adopts a hybrid approach, combining classical beam elements, elastic foundations for the simulation of tooth contacts, and substructures derived from three-dimensional (3D) finite element grids for thin-rimmed gears and their supporting shafts. The pinion shaft and body are modeled via beam elements which simulate bending, torsion and traction. Tooth contact deflections are described using time-varying elastic foundations (Pasternak foundations) connected by independent contact stiffness. In order to account for thin-rimmed gears, a 3D finite element model of the gear (excluding teeth) is set up and a pseudo-modal reduction technique is used prior to solving the equations of motion. Depending on the gear structure, the results reveal a potentially significant influence of thin rims on both quasi-static and dynamic tooth loading.
Mathematical Model and Characteristic Analysis of Elliptical Gears Manufactured by Circular-Arc Shaper Cutters
Authors: Bair Biing-Wen , Chen Chien-Fa , Chen Shih-Fa , Chou Chung-Yi
Published: January 2007

A circular-arc elliptical gear drive with convex (or concave) tooth profiles, which is used in an oil pump with a larger pumping volume, was simulated by using circular-arc shaper cutters with concave (or convex) tool profiles. Mathematical models of circular-arc elliptical gears, based on the theory of gearing and the gear generation mechanism, were also developed. The generated elliptical gear drive has a convex–concave tooth profile contact. Because of its complex geometry, the profile of circular-arc elliptical gears may exhibit tooth undercutting, and pointed teeth. Pointed teeth usually appear on the major axis of the elliptical pitch curve. A geometric relation was developed and applied to prevent the pointed teeth on the elliptical gears. A larger pressure angle at major axis and circular-arc radius can eliminate tooth undercutting and increase its tooth thickness at the addendum circle for small teeth. Moreover, a computer simulation program was developed to generate the tooth profile of circular-arc elliptical gears without tooth undercutting and pointed teeth.
On the Dynamic Balancing of Multi-DOF Parallel Mechanisms With Multiple Legs
Authors: Wu Yangnian , Gosselin Clément M.
Published: January 2007

This paper addresses the dynamic balancing of multi-degree-of-freedom (multi-DOF) parallel mechanisms with multiple legs using the dynamic equivalence between point masses and arbitrary moving platforms. In this technique, proposed elsewhere, the mass and inertia of the moving platform are dynamically replaced by point masses located at the points of attachment of the legs to the platform and the mechanisms are balanced by considering each of the legs independently. In this paper, two, three, and four point masses are respectively discussed for different cases. Finally, some physical interpretations are given.
Characterization and Variational Modeling of Ionic Polymer Transducers
Authors: Buechler Miles A. , Leo Donald J.
Published: January 2007

Ionomeric polymers are a promising class of intelligent material which exhibit electromechanical coupling similar to that of piezoelectric bimorphs. Ionomeric polymers are much more compliant than piezoelectric ceramics or polymers and have been shown to produce actuation strain on the order of 2% at operating voltages between 1V and 3V (Akle et al., 2004, Proceedings IMECE). Their high compliance is advantageous in low force sensing configurations because ionic polymers have a very little impact on the dynamics of the measured system. Here we present a variational approach to the dynamic modeling of structures which incorporate ionic polymer materials. To demonstrate the method a cantilever beam model is developed using this variational approach. The modeling approach requires a priori knowledge of three empirically determined material properties: elastic modulus, dielectric permittivity, and effective strain coefficient. Previous work by Newbury and Leo has demonstrated that these three parameters are strongly frequency dependent in the range between less than 1Hz to frequencies greater than 1kHz. Combining the frequency-dependent material parameters with the variational method produces a second-order matrix representation of the structure. The frequency dependence of the material parameters is incorporated using a complex-property approach similar to the techniques for modeling viscoelastic materials. A transducer is manufactured and the method of material characterization is applied to determine the mtaerial properties. Additional experiments are performed on this transducer and both the material and structural model are validated. Finally, the model is shown to predict sensing response very well in comparison to experimental results, which supports the use of an energy-based variational approach for modeling ionomeric polymer transducers.
A Generalization of Effective Mass for Selecting Free–Free Target Modes
Authors: Kammer Daniel C. , Cessna Joseph , Kostuch Andrew
Published: January 2007

One of the most important tasks in pretest analysis and modal survey planning is the selection of target modes. The target modes are those mode shapes that are determined to be dynamically important using some definition. While there are many measures of dynamic importance, one of the measures that has been of greatest interest to structural dynamicists, is the contribution of each mode to the dynamic loads at an interface. Dynamically important modes contribute significantly to the interface loads and must be retained in any reduced analytical representation. These modes must be identified during a ground vibration test to validate the corresponding finite element model. Structural dynamicists have used interface load based effective mass measures to efficiently identify target modes for constrained structures. The advantage of these measures of dynamic importance is that they are absolute, in contrast to other measures that only indicate the importance of one mode shape relative to another. However, in many situations, especially in aerospace applications, structures must be tested in a free–free configuration. In the case of free–free elastic modes, the effective mass values are zero, making them useless measures of dynamic importance. This paper presents a new effective mass like measure of absolute dynamic importance that can be applied to free–free structures. The new method is derived based upon the free–free modal equations of motion. The approach is shown to be directly related to ranking mode shapes based on approximate balanced singular values. But, unlike the approximate balanced singular value approach, it is an absolute measure of importance. A numerical example of a general spacecraft system is presented to illustrate the application of the new technique. Dynamically important mode shapes were easily identified for modal acceleration, velocity, and displacement output. The new method provides an efficient technique for selecting target modes for a modal vibration test, or the reduction of a modal based analytical model to the dynamically important mode shapes.
An Active Dynamic Vibration Absorber for a Hand-Held Vibro-Elastography Probe
Authors: Rivaz Hassan , Rohling Robert
Published: January 2007

Vibro-elastography is a new medical imaging method that identifies the mechanical properties of tissue by measuring tissue motion in response to a multi-frequency external vibration source. Previous research on vibro-elastography used ultrasound to measure the tissue motion and system identification techniques to identify the tissue properties. This paper describes a hand-held probe with a combined vibration source and ultrasound transducer to implement the new method as a practical device. The device uses a proportional integral active dynamic vibration absorber with an electromagnetic actuator to counterbalance the reaction forces from contact with the tissue. Experiments show an operational frequency range of 5-20Hz, with at least 15dB vibration absorption in 0.4s for single frequency excitation. Experiments with variable frequency and amplitude excitation also show a high level of vibration absorption.
Mechanisms of structural evolutions associated with the high current pulsed electron beam treatment of a NiTi shape memory alloy
Authors: Zhang K. M. , Zou J. X. , Grosdidier T. , Gey N. , Weber S. , Yang D. Z. , Dong C.
Published: January 2007

The aim of this study was to investigate, for the first time, the surface modifications associated with the use the recently developed high current pulsed electron beam technique for modifying the surface of an intermetallic NiTi alloy. Samples were treated with the same electron beam parameters but different numbers of pulses (i.e., five and ten pulses) and the present article concentrates on a detailed characterization of their texture and microstructure modifications. The observation of surface features such as craters, wavy surfaces with protrusions, chemistry modifications, and the development of specific texture components are discussed as the consequence of the combination of surface melting and evaporation mechanisms. It is also shown that in the subsurface, below the melted layer, the martensitic transformation was triggered due to the effects of the thermal stresses and shock waves propagating in the material.
Phase-change characteristics of chalcogenide Ge1Se1Te2 thin films for use in nonvolatile memories
Authors: Chung Hong-Bay , Shin Kyung , Lee Jae-Min
Published: January 2007

In the present work, the authors show that Ge1Se1Te2 thin films provide a promising alternative for phase-change random access memory (PRAM) applications to overcome the problems of conventional Ge2Sb2Te5 PRAM devices. 100-nm-thick chalcogenide Ge1Se1Te2 thin films were prepared by evaporating a stoichiometric bulk target, and Ge1Se1Te2 thin-film PRAM devices with a 20-μm-sized memory cell have been fabricated. The devices exhibited a successful switching between an amorphous and a crystalline phase by applying a 50ns, 7.3V set pulse and a 30ns, 7.4V reset pulse with a switching dynamic range (the ratio of Rhigh to Rlow) as high as 103. For a static-mode switching operation, two different resistance states in Ge1Se1Te2 thin films have been observed at low voltages, depending on the two different crystalline states of the film. The first phase-transition temperature of Ge1Se1Te2 thin film is found to be 110°C, which is clearly lower than that of Ge2Sb2Te5 films from the temperature-dependent conductivity measurements. From field emission scanning electron microscope and x-ray diffraction analyses, the authors confirmed that phase-change properties of Ge1Se1Te2 materials are closely related to the structure of the amorphous state and crystalline state.
Rotary reactor for atomic layer deposition on large quantities of nanoparticles
Authors: McCormick J. A. , Cloutier B. L. , Weimer A. W. , George S. M.
Published: January 2007

Challenges are encountered during atomic layer deposition (ALD) on large quantities of nanoparticles. The particles must be agitated or fluidized to perform the ALD surface reactions in reasonable times and to prevent the particles from being agglomerated by the ALD film. The high surface area of nanoparticles also demands efficient reactant usage because large quantities of reactant are required for the surface reactions to reach completion. The residence time of the reactant in a fluidized particle bed reactor may be too short for high efficiency if the ALD surface reactions have low reactive sticking coefficients. To address these challenges, a novel rotary reactor was developed to achieve constant particle agitation during static ALD reactant exposures. In the design of this new reactor, a cylindrical drum with porous metal walls was positioned inside a vacuum chamber. The porous cylindrical drum was rotated by a magnetically coupled rotary feedthrough. By rotating the cylindrical drum to obtain a centrifugal force of less than one gravitational force, the particles were agitated by a continuous “avalanche” of particles. In addition, an inert N2 gas pulse helped to dislodge the particles from the porous walls and provided an efficient method to purge reactants and products from the particle bed. The effectiveness of this rotary reactor was demonstrated by Al2O3 ALD on ZrO2 particles. A number of techniques including transmission electron microscopy, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy confirmed that the Al2O3 ALD film conformally coats the ZrO2 particles. Combining static reactant exposures with a very high surface area sample in the rotary reactor also provides unique opportunities for studying the surface chemistry during ALD.
Quantitative detection of tiny amounts of helium isotopes in a hydrogen isotope atmosphere using a standard-resolution quadrupole mass spectrometer
Authors: Frattolillo A. , De Ninno A. , Rizzo A.
Published: January 2007

This article describes a new method to quantitatively detect extremely small amounts of helium (and eventually other inert gases) in complex gaseous mixtures, even in the presence of very high concentrations of hydrogen isotopes, despite using a conventional (i.e., standard-resolution) quadrupole mass spectrometer. This is accomplished by means of two nonevaporable getter (NEG) pumps, which effectively remove all active components in the original gas mixture with particular regard to hydrogen isotopes. Obviously, noble gases are preserved. The gas sample to be analyzed is initially admitted in a first chamber equipped with a NEG pump operating at high temperature (≈450°C), in order to remove most of the active gases quickly. The residual gas mixture is then allowed to expand through a gate valve into the analysis chamber, where a second NEG pump, operating at room temperature, completes the selective pumping action and removes to high degree hydrogen isotopes and other chemically active gases. The turbomolecular pump, which is used to evacuate the chamber, is excluded during the analysis. The results of extensive tests carried out with a fully automated facility built at ENEA Frascati are reported, demonstrating the effectiveness of this method which allows detection of He4∕D2 peak ratios as small as ≈2.5×10−7. During these tests, a quadrupole mass spectrometer which can operate in both standard- and high-resolution modes has been used. This latter operating mode has been selected, when necessary, in order to provide evidence for the absence of deuterium contributions to mass 4.
Long pulse pumping behavior of a cryopump for the neutral beam injector
Authors: Chakrapani Ch. , Sharma S. K. , Chakraborty A. K. , Singh M. J. , Patel G. B. , Rambabu S. , Prajapati B. , Upadhyay J. , Mattoo S. K.
Published: January 2007

This article presents studies on the long term pumping behavior of a cryopump. It is shown that the pumping speed does not deteriorate on a time scale of 4200s for a gas load of 2.4×105torrl, corresponding to ∼106 ML of hydrogen. It has also been observed that the need for regeneration of the pump is dictated by the safety limits of operation rather than its pumping capability. No sudden boil off of the cryogen takes place during the regeneration phase.
Influence of the deposition parameters on the electronic and structural properties of pulsed laser ablation prepared Si1−xCx thin films
Authors: Neri F. , Barreca F. , Fazio E. , Barletta E. , Mondio G. , Trusso S. , Brendebach B. , Modrow H.
Published: January 2007

Si 1 − x C x thin films have been deposited by pulsed laser ablation of a polycrystalline silicon carbide target in vacuum. The influence of the deposition parameters on the optical and structural properties of the samples was investigated by means of Fourier transform IR, Raman, ex situ ellipsometric, x-ray photoelectron, and x-ray absorption near edge structure spectroscopies. Both deposition temperature and laser fluence were increased up to 1150K and 14J∕cm2, respectively. Increasing the two parameters, a better quality of the thin films was observed due to the existence of a crystalline order on a nanometric scale. Nevertheless, at higher deposition temperatures, a graphitic phase occurred inducing a degradation of the optical properties. Such a phase was not observed increasing the laser fluence. The film formation mechanism has also been qualitatively discussed on the basis of the subplantation model proposed by Lifshitz et al. [Phys. Rev. Lett. 62, 1290 (1989); Phys. Rev. B 41, 1046 (1990)].
Properties of SrBi2Ta0.8Nb1.2O9 thin films deposited by plasma-assisted pulsed-laser deposition
Authors: Yang Pingxiong , Deng Hongmei , Shi Meirong , Tong Ziyang
Published: January 2007

A significant effect of the introduction of O2-plasma discharge during pulsed laser ablative deposition of SrBi2Ta0.8Nb1.2O9 (SBTN) films on improving the crystallite orientation, ferroelectric, and optical properties has been described. Plasma-excitation potential, applied at an auxiliary-ring electrode placed near the substrate, has a profound effect on surface morphology, crystallite orientation, remnant polarization, and optical constants. Compared with no plasma assist, the films have an additional strong (008) and (200) and an approximate 32% multiplication in remnant polarization. The refractive index (n∼2.27) with plasma is greater than the corresponding values (n∼2.16) of no plasma. Clearly, the presence of O2 plasma assists in the growth of SBTN films, which display much improved ferroelectric and optical properties.
Synthesis and characterization of inorganic silicon oxycarbide glass thin films by reactive rf-magnetron sputtering
Authors: Ryan Joseph V. , Pantano C. G.
Published: January 2007

Silicon oxycarbide glasses have been of interest because of the potential range of properties they might exhibit through a change in carbon-to-oxygen ratio. They are metastable materials and, as such, their structures and properties are very dependent upon the synthesis method. Silicon oxycarbide bonding has been seen in materials made by melting, oxidation, polycarbosilane or sol/gel pyrolysis, and chemical vapor deposition. In this work, the radio-frequency reactive sputtering of silicon carbide targets was explored for synthesis of amorphous silicon oxycarbide thin films. SiO(2−2x)Cx films, with a continuous range of compositions where 0⩽x⩽1, were deposited by controlling the amount of oxygen present in the plasma with a SiC target. This resulted in a density range from 1.9to2.8g∕cm3 and a range of refractive indexes from 1.35 to 2.85. Analysis of the film compositions, structures, and properties were performed using x-ray photoelectron spectroscopy, infrared spectroscopy, nuclear magnetic resonance, profilometry, electron microscopy, grazing incidence x-ray reflectivity, and UV-visible transmission and reflection. The compositional range obtainable by this rf sputtering method is much wider than that of other synthesis methods. It is shown here that for oxygen-to-carbon ratios between ∼0.10 and 10.0, silicon oxycarbide bonding comprises 55%–95% of the material structure. These sputter-deposited materials were also found to have significantly less free carbon as compared to those produced by other methods. Thus, the unique properties for these novel oxycarbide materials can now be established.
Effect of chemical bonds on the properties of SiN in thin film transistor liquid crystal display
Authors: Xie Zhenyu , Long Chunping , Deng Chao Yong , Rim Seung Moo
Published: January 2007

The hydrogenated amorphous silicon nitride (a-SiNx:H) thin films were produced in a radio-frequency plasma-enhanced chemical vapor deposition system using NH3∕SiH4∕N2 mixture source gases at 330°C. In this study the authors determine the structural properties of a-SiNx:H thin films with Fourier transform infrared measurement and relate these to both the processing parameters and their physical/optical properties. The Si–H and N–H bond densities are affected by the processing parameters. They find that the plasma power density and chamber pressure play minor roles compared to the gas flow rate of SiH4, and the role of the electrode spacing is indistinctive. The Si–H, N–H, and Si–N bond densities are important parameters affecting the physical/optical properties of low deposition rate thin film (the thin films in the proximity of a-SiNx:H∕a-Si interface) and high deposition rate (HDR) thin film (bottom gate insulator thin films). The optical band gap (E04) could be tuned by the N radical density. The N radical density increases with increasing N–H and Si–N bond densities and decreasing Si–H bond density. The Si–N bond density and the Si and N dangling bonds enhance the dielectric constant, but the Si–H and N–H bond densities have different effects. The dielectric constant increases with increasing Si–H bond density for the HDR thin films, because the high plasma power density (>38.5W∕cm2) could break more Si–N bonds. Finally, process parameters are obtained for optimized performance of the thin film transistors.
The use of resonant scattering to identify stone fracture in shock wave lithotripsy
Authors: Owen Neil R. , Bailey Michael R. , Crum Lawrence A. , Sapozhnikov Oleg A. , Trusov Leonid A.
Published: January 2007

There is currently little feedback as to whether kidney stones have fractured during shock wave lithotripsy. Resonant scattering of the lithotripter shock wave was used here to differentiate intact and fractured stone models in water. Scattering, including reflection and radiation due to reverberation from within the stone, was calculated numerically with linear elasticity theory and agreed well with measurements made with a focused receiver. Identification of fracture was possible through frequency analysis, where scatter from fractured stones was characterized by higher energy in distinct bands. High-speed photography concurrent with measurement indicated the effect was not due to cavitation.
Wandering Minds: The Default Network and Stimulus-Independent Thought
Authors: Mason Malia F. , Norton Michael I. , Van Horn John D. , Wegner Daniel M. , Grafton Scott T. , Macrae C. Neil
Published: January 2007

Despite evidence pointing to a ubiquitous tendency of human minds to wander, little is known about the neural operations that support this core component of human cognition. Using both thought sampling and brain imaging, the current investigation demonstrated that mind-wandering is associated with activity in a default network of cortical regions that are active when the brain is “at rest.” In addition, individuals' reports of the tendency of their minds to wander were correlated with activity in this network.
Enabling Europe to Innovate
Authors: Dearing Andrew
Published: January 2007

As activities that relate to innovation become increasingly global and open and so draw the private and public sectors into complex networks of partnerships, these activities also tend to concentrate where the ecosystem is most supportive. European public policy, which in recent years has emphasized the importance of research and development (R&D) in achieving competitive knowledge-based societies, is shifting toward approaches that address the broader qualities required of favorable ecosystems for innovation in a global economy, thereby incorporating the roles of market demand, public procurement, and regulation, as well as science, education, and industrial R&D, as part of determining effective innovation policies.
High-Throughput Identification of Catalytic Redox-Active Cysteine Residues
Authors: Fomenko Dmitri E. , Xing Weibing , Adair Blakely M. , Thomas David J. , Gladyshev Vadim N.
Published: January 2007

Cysteine (Cys) residues often play critical roles in proteins; however, identification of their specific functions has been limited to case-by-case experimental approaches. We developed a procedure for high-throughput identification of catalytic redox-active Cys in proteins by searching for sporadic selenocysteine-Cys pairs in sequence databases. This method is independent of protein family, structure, and taxon. We used it to selectively detect the majority of known proteins with redox-active Cys and to make additional predictions, one of which was verified. Rapid accumulation of sequence information from genomic and metagenomic projects should allow detection of many additional oxidoreductase families as well as identification of redox-active Cys in these proteins.
Response to Comment on "The Geometry of Musical Chords"
Authors: Tymoczko Dmitri
Published: January 2007

The basic sonorities of traditional Western tonality divide the octave nearly evenly and are found near the center of the orbifolds

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and

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. Many common musical patterns exploit this fact, which permits efficient voice leading between structurally similar chords. In actual music, these patterns sometimes appear incompletely or are accompanied by additional notes. Using orbifolds in musical analysis therefore requires interpretive skill.
Nonequilibrium Mechanics of Active Cytoskeletal Networks
Authors: Mizuno Daisuke , Tardin Catherine , Schmidt C. F. , MacKintosh F. C.
Published: January 2007

Cells both actively generate and sensitively react to forces through their mechanical framework, the cytoskeleton, which is a nonequilibrium composite material including polymers and motor proteins. We measured the dynamics and mechanical properties of a simple three-component model system consisting of myosin II, actin filaments, and cross-linkers. In this system, stresses arising from motor activity controlled the cytoskeletal network mechanics, increasing stiffness by a factor of nearly 100 and qualitatively changing the viscoelastic response of the network in an adenosine triphosphate–dependent manner. We present a quantitative theoretical model connecting the large-scale properties of this active gel to molecular force generation.
Control of
Drosophila
Gastrulation by Apical Localization of Adherens Junctions and RhoGEF2
Authors: Kölsch Verena , Seher Thomas , Fernandez-Ballester Gregorio J. , Serrano Luis , Leptin Maria
Published: January 2007

A hallmark of epithelial invagination is the constriction of cells on their apical sides. During
Drosophila
gastrulation, apical constrictions under the control of the transcription factor Twist lead to the invagination of the mesoderm. Twist-controlled G protein signaling is involved in mediating the invagination but is not sufficient to account for the full activity of Twist. We identified a Twist target, the transmembrane protein T48, which acts in conjunction with G protein signaling to orchestrate shape changes. Together with G protein signaling, T48 recruits adherens junctions and the cytoskeletal regulator RhoGEF2 to the sites of apical constriction, ensuring rapid and intense changes in cell shape.
Water Solubility in Aluminous Orthopyroxene and the Origin of Earth's Asthenosphere
Authors: Mierdel Katrin , Keppler Hans , Smyth Joseph R. , Langenhorst Falko
Published: January 2007

Plate tectonics is based on the concept of rigid lithosphere plates sliding on a mechanically weak asthenosphere. Many models assume that the weakness of the asthenosphere is related to the presence of small amounts of hydrous melts. However, the mechanism that may cause melting in the asthenosphere is not well understood. We show that the asthenosphere coincides with a zone where the water solubility in mantle minerals has a pronounced minimum. The minimum is due to a sharp decrease of water solubility in aluminous orthopyroxene with depth, whereas the water solubility in olivine continuously increases with pressure. Melting in the asthenosphere may therefore be related not to volatile enrichment but to a minimum in water solubility, which causes excess water to form a hydrous silicate melt.
Language Learning Through Selection
Authors: Lidz Jeffrey , Pearl Lisa
Published: January 2007

The Infinite Gift
. How Children Learn and Unlearn the Languages of the World.
By Charles D. Yang
. Scribner (Simon and Schuster), New York, 2006. 285 pp. $25, C$34.50. ISBN 9780743237567.

Writing for nonspecialists, the author discusses the processes by which children learn to talk and to understand speech.
Farmland Biodiversity and the Footprint of Agriculture
Authors: Butler S. J. , Vickery J. A. , Norris K.
Published: January 2007

Sustainable development requires the reconciliation of demands for biodiversity conservation and increased agricultural production. Assessing the impact of novel farming practices on biodiversity and ecosystem services is fundamental to this process. Using farmland birds as a model system, we present a generic risk assessment framework that accurately predicts each species' current conservation status and population growth rate associated with past changes in agriculture. We demonstrate its value by assessing the potential impact on biodiversity of two controversial land uses, genetically modified herbicide-tolerant crops and agri-environment schemes. This framework can be used to guide policy and land management decisions and to assess progress toward sustainability targets.
Electric Field-Induced Modification of Magnetism in Thin-Film Ferromagnets
Authors: Weisheit Martin , Fähler Sebastian , Marty Alain , Souche Yves , Poinsignon Christiane , Givord Dominique
Published: January 2007

A large electric field at the surface of a ferromagnetic metal is expected to appreciably change its electron density. In particular, the metal's intrinsic magnetic properties, which are commonly regarded as fixed material constants, will be affected. This requires, however, that the surface has a strong influence on the material's properties, as is the case with ultrathin films. We demonstrated that the magnetocrystalline anisotropy of ordered iron-platinum (FePt) and iron-palladium (FePd) intermetallic compounds can be reversibly modified by an applied electric field when immersed in an electrolyte. A voltage change of –0.6 volts on 2-nanometer-thick films altered the coercivity by –4.5 and +1% in FePt and FePd, respectively. The modification of the magnetic parameters was attributed to a change in the number of unpaired
d
electrons in response to the applied electric field. Our device structure is general and should be applicable for characterization of other thin-film magnetic systems.
Recombinant Protein-Based Assays for Detection of Antibodies to Severe Acute Respiratory Syndrome Coronavirus Spike and Nucleocapsid Proteins
Authors: Haynes Lia M. , Miao Congrong , Harcourt Jennifer L. , Montgomery Joel M. , Le Mai Quynh , Dryga Sergey A. , Kamrud Kurt I. , Rivers Bryan , Babcock Gregory J. , Oliver Jennifer Betts , Comer James A. , Reynolds Mary , Uyeki Timothy M. , Bausch Daniel , Ksiazek Thomas , Thomas William , Alterson Harold , Smith Jonathan , Ambrosino Donna M. , Anderson Larry J.
Published: January 2007

Recombinant severe acute respiratory syndrome (SARS) nucleocapsid and spike protein-based immunoglobulin G immunoassays were developed and evaluated. Our assays demonstrated high sensitivity and specificity to the SARS coronavirus in sera collected from patients as late as 2 years postonset of symptoms. These assays will be useful not only for routine SARS coronavirus diagnostics but also for epidemiological and antibody kinetic studies.
Evaluation of a Novel Enzyme-Linked Immunosorbent Assay To Detect Immunoglobulin G Antibody to Enolase for Serodiagnosis of Invasive Candidiasis
Authors: Laín Ana , Moragues María D. , Ruiz Juan Carlos García , Mendoza Joaquín , Camacho Ana , del Palacio Amalia , Pontón José
Published: January 2007

The performance of a new test to detect antibodies to
Candida albicans
recombinant enolase was investigated in 47 immunocompromised and 51 immunocompetent patients. The sensitivity, specificity, and positive and negative predictive values of the test for the diagnosis of invasive candidiasis were 81.0, 83.9, 79.1, and 85.5%, respectively.
Characterization ofPlasmodium vivaxHeat Shock Protein 70 and Evaluation of Its Value for Serodiagnosis of Tertian Malaria
Authors: Na Byoung-Kuk , Park Jae-Won , Lee Hyeong-Woo , Lin Klin , Kim Seon-Hee , Bae Young-An , Sohn Woon-Mok , Kim Tong-Soo , Kong Yoon
Published: January 2007

We have characterizedPlasmodium vivaxheat shock protein 70 (PvHSP70) and evaluated serodiagnostic applicability of recombinant PvHSP70 (rPvHSP70). In enzyme-linked immunosorbent assays and immunoblot analyses, rPvHSP70 showed high sensitivity (88.8%; 203/228 cases).P. falciparum-infected sera revealed positive reactions (78.8%). The predominant immunoglobulin G (IgG) subclasses were segregated with IgG1 and IgG3.
Novel Acetone Metabolism in a Propane-Utilizing Bacterium,Gordoniasp. Strain TY-5
Authors: Kotani Tetsuya , Yurimoto Hiroya , Kato Nobuo , Sakai Yasuyoshi
Published: January 2007

In the propane-utilizing bacteriumGordoniasp. strain TY-5, propane was shown to be oxidized to 2-propanol and then further oxidized to acetone. In this study, the subsequent metabolism of acetone was studied. Acetone-induced proteins were found in extracts of cells induced by acetone, and a gene cluster designatedacmABwas cloned on the basis of the N-terminal amino acid sequences of acetone-induced proteins. TheacmAandacmBgenes encode a Baeyer-Villiger monooxygenase (BVMO) and esterase, respectively. The BVMO encoded byacmAwas purified from acetone-induced cells ofGordoniasp. strain TY-5 and characterized. The BVMO exhibited NADPH-dependent oxidation activity for linear ketones (C3to C10) and cyclic ketones (C4to C8).Escherichia coliexpressing theacmAgene oxidized acetone to methyl acetate, andE. coliexpressing theacmBgene hydrolyzed methyl acetate. Northern blot analyses revealed that polycistronic transcription of theacmABgene cluster was induced by propane, 2-propanol, and acetone. These results indicate that theacmABgene products play an important role in the metabolism of acetone derived from propane oxidation and clarify the propane metabolism pathway of strain TY-5 (propane → 2-propanol → acetone → methyl acetate → acetic acid + methanol). This paper provides the first evidence for BVMO-dependent acetone metabolism.