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We report an error analysis method for primary analytical methods in the absence of calibration standards. Quantitative [sup.13]C NMR analysis of ethylene/1-octene (E/O) copolymers is given as an example. Because the method is based on a self-calibration scheme established by counting, it is a measure of accuracy rather than precision. We demonstrate it is self-consistent and neither underestimate nor excessively overestimate the experimental errors. We also show the method identified previously unknown systematic biases in a NMR instrument. The method can eliminate unnecessary data averaging to save valuable NMR resources. The accuracy estimate proposed is not unique to [sup.13]C NMR spectroscopy of E/O but should be applicable to all other measurement systems where the accuracy of a subset of the measured responses can be established. 10.1021/ac901565u

Ball and rolling element bearings are perhaps the most widely used components in industrial machinery. They are used to support load and allow relative motion inherent in the mechanism to take place. Subsurface originated spalling has been recognized as one of the main modes of failure for rolling contact fatigue (RCF) of bearings. In the past few decades a significant number of investigators have attempted to determine the physical mechanisms involved in rolling contact fatigue of bearings and proposed models to predict their fatigue lives. In this paper, some of the most widely used RCF models are reviewed and discussed, and their limitations are addressed. The paper also presents the modeling approaches recently proposed by the authors to develop life models and better understanding of the RCF. [DOI: 10.1115/1.3209132] Keywords: rolling contact fatigue, bearing life, empirical models, material microstructure

Lubrication and friction at workpiece-tool interface play an important role in product quality control of sheet metal forming process. Surface microstructures of sheets have a great influence on the development of lubrication films. In order to investigate the effects of the rolling direction of aluminum alloy sheet and lubricant on the friction behavior in sheet metal forming, strip drawing test was used. The sample used was electric discharge texturing (EDT) surface. Lubricants, both with and without additives, were used. The strip drawing tests were performed at angles between the sliding and rolling directions of 0-90 deg. Variations in the sheet surface topography were analyzed by comparing the sheet surface microstructures and its 3D surface parameters before and after the strip drawing test. Results of the strip drawing tests indicate that the kind and amount of lubricant have great influences on friction at the interface, and the lubricant with additives benefits improving the friction behavior between the sheet and the tool. The EDT surface of the aluminum alloy sheet has an anisotropic frictional property during deep drawing process due to different angles between the sliding and rolling directions. When the sliding direction is parallel to the rolling direction, the coefficient of friction has the highest value. When the angle between the sliding and rolling directions increases, the coefficient of friction decreases. The surface microstructure of the sheets after the strip drawing test at different angles between the sliding and rolling directions has been modified, and its 3D surface parameters decrease significantly to a different degree. [DOI: 10.1115/1.3201843] Keywords: surface microstructure, friction, rolling direction, strip drawing test, 3D surface parameters

We demonstrate and discuss the performance of fully integrated and flexible micro thermoelectric generators ([micro]TEGs). The devices are fabricated with a low-cost microfabrication process based on electrochemical deposition of a thermoelectric material into a polymer mold. Overall system optimization is demonstrated by means of NiCu and p- and n-type [Bi.sub.2][Te.sub.3]-based [micro]TEGs. Influences of design, material, fabrication, and performance parameters on device performance are explained by means of measurements and model calculations. The fabricated devices generate up to 2.6 x [10.sup.-3] [micro]W x [cm.sup.-2] x [K.sup.-2] for devices with NiCu thermocouples and up to 0.29 [micro]W x [cm.sup.-2] x [K.sup.-2] for [Bi.sub.2][Te.sub.3]-based generators in planar state. Mechanical testing on NiCu [micro]TEGs demonstrated functionality of the generator when bent to curvatures down to 7.5 mm. This allows for enhanced thermal contact to nonplanar surfaces. [2008-0084] Index Terms--[Bi.sub.2][Te.sub.3], electrochemical deposition (ECD), power MEMS, SU-8, thermoelectric generator, 3-D microstructure.

Two versions of microdischarge-based pressure sensors, which operate by measuring the change, with pressure, in the spatial current distribution of pulsed dc microdischarges, are reported. The inherently high temperatures of the ions and electrons in the microdischarges make these devices amenable to high-temperature operation. The first sensor type uses 3-D arrays of horizontal bulk metal electrodes embedded in quartz substrates with electrode diameters of 1-2 mm and 50-100-[micro]m interelectrode spacing. These devices were operated in nitrogen over a range of 10-2000 torr, at temperatures as high as 1000[degrees]C. The maximum measured sensitivity was 5420 ppm/torr at the low end of the dynamic range and 500 ppm/torr at the high end, while the temperature coefficient of sensitivity ranged from -925 to -550 ppm/K. Sensors of the second type use planar electrodes and have active areas as small as 0.13 [mm.sup.2]. These devices, when tested in a chemical sensing system flowing helium as a carrier gas, had a maximum sensitivity of 9800 ppm/torr, a dynamic range of 25-200 torr, and a temperature coefficient of sensitivity of approximately -1412 ppm/K. [2008-0262] Index Terms--Plasma applications, plasma confinement, plasma measurements, plasma properties, pressure effects, sensitivity.

We present a theoretical and experimental investigation into the effect of the motion of a printed circuit board (PCB) on the response of microelectromechanical systems (MEMS) devices to shock loading. For the theoretical part, a 2-DOF model is used, where the first degree of freedom accounts for the PCB. The second degree of freedom represents the motion of the MEMS microstructure. Low-g acceleration pulses are applied to the MEMS-PCB assembly base to simulate shock pulses generated from a drop-table test. Simulation data are presented to show the effects of the natural frequency of the PCB, the natural frequency of the microstructure, and the shock pulse duration. Universal 3-D spectra representing the effect of these parameters are presented. It is found that neglecting the PCB effect on the design of MEMS devices under shock loads can lead to undesirable motion of their microstructures. The effects of electrostatic force and squeeze film damping are investigated. It is found that the amplification of motion due to the PCB can cause early pull-in instability for MEMS devices implementing electrostatic forces. The effect of higher order modes of a microbeam is studied through a continuous beam model coupled with a lumped model of the PCB. The limitations of the 2-DOF model are discussed. An experimental investigation is conducted to verify the theoretical results using a capacitive accelerometer. Experimental data for the response of the accelerometer while it is mounted on two representative PCBs due to different low-g shock conditions are shown. [2008-0026] Index Terms--Electrostatic force, mechanical shock, micro-electromechanical systems (MEMS), microstructure, printed circuit board (PCB), reliability, squeeze film damping (SQFD).

Hydroxyapatite is an important constituent of natural bone, and possesses excellent biocompatibility and bioactivity, but its brittle nature limits its use for bone tissue engineering. Nanohydroxyapatite (nanoHAP) has been used in synthesis of biomimetic composites for more than a decade, yet the mechanics of nanoHAP particles is not fully understood. The present work attempts to advance the current understanding of mechanics of hydroxyapatite at nanoscale, by carrying out systematic nanoindentation experiments on nanoHAP and surface modified nanoHAP [prepared by in situ mineralization in presence of polyacrylic acid (PAAc)]. Quantitative nanomodulus maps of both modified and unmodified HAP nanoparticles indicate that various surface features of HAP nanoparticles can be probed. Dips in values of elastic moduli across the nanoparticle surfaces in modified nanohydroxyapatite are indicative of composite responses from both polymer and mineral phases (PAAc-HAP) on the surface. Nanoindentation experiments were performed at 100, 1,000, 3,000, 5,000, and 8,000 [micro]N loads, respectively, to obtain the indentation response from both shallow and deep penetration depths. Nanoindentation results at shallow penetration depths are influenced by nanoscale surface roughness of irregular-shaped HAP nanoparticles and nonuniform distribution of PAAc in the microstructure. Significant nonbonded interactions between HAP and PAAc, the mechanical properties of individual constituents (HAP and PAAc) lead to superior nanomechanical properties of surface-modified nanoHAP as compared to unmodified HAP. The overall inelastic nanomechanical response (including damage leading to reduced overall elastic modulus) is strongly influenced by the nature of the interfaces between the nanoparticles, especially when indent size is much larger than the particle size. DOI: 10.1061/(ASCE)EM.1943-7889.0000002 CE Database subject headings: Bioengineering; Particle size; Composite materials; Microstructure; Material properties; Interfaces; Biological properties.

This paper examines the structuration and destructuration characteristics of cement-treated Singapore marine clay and their relation to the observed microstructural behavior. The pozzolanic reaction is found to be very significant up to curing periods of 1 year, and thus the unconfined compressive strength increases notably leading to the formation of more structured treated clay. Due to the effect of structuration (existing of cementation bond), the yield stress increases resulting in an expansion of the yield surface and failure envelope under compression and shearing. The microstructural observation of treated clay structure at various stress levels from one-dimensional consolidation shows that destructuration (breaking of cementation bond) is progressive; the largest intercluster voids being the first affected. As the consolidation proceeds, both inter and intracluster voids are affected. Consolidated undrained triaxial results reveal that complete destructuration only takes place on the shear plane at which the clay-cement cluster crushes. CE Database subject headings: Microstructure; Fabrics; Cements; Clays; Singapore.

The creep strength of welded joints in high Cr steels decreases due to the formation of Type IV creep damage in heat-affected zones (HAZs) during long-term use at high temperatures. This paper aims to elucidate the processes and mechanisms of Type IV creep damage using Mod.9Cr-1Mo (ASME Grade 91) steel weldments. Long-term creep tests for base metal, simulated fine-grained HAZ, and welded joints were conducted at 550[degrees]C, 600[degrees]C, and 650[degrees]C. Furthermore, creep tests of thick welded joint specimens were interrupted at 0.1, 0.2, 0.5, 0.7, 0.8, and 0.9 of rupture life and damage distributions were measured quantitatively. It was found that creep voids were initiated at an early stage of life inside the specimen thickness and coalesced to form cracks at a later stage of life. Creep damage was observed mostly at 25% below the surface of the plate. Experimental creep damage distributions were compared with computed versions using finite element method and damage mechanics analysis. Both multi-axial stress state and strain concentration in fine-grained HAZ appear to influence the formation and distribution of creep voids. [DOI: 10.1115/1.3028021] Keywords: Mod.9Cr-1Mo steel welded joint, Type IV creep damage, FEM, damage mechanics

In spite of impressive progress in developing general constitutive laws for soft tissues, there exists still no comprehensive model valid for any general deformation scheme. The present study focuses on the uniaxial response of the skin as a model .for other multifibrous soft tissues. While the skin's nonlinear viscoelastic constitutive response has been extensively studied and modeled, the phenomena associated with mechanical preconditioning have so fur not been dealt with. Yet preconditioning is an inherent response feature in the skin, both in vitro and in vivo. It is hypothesized that by considering the structure of the elastic and collagen fibers and their individual rheological properties, it is possible to develop a reliable general constitutive law for the skin's uniaxial response. A stochastic hybrid constitutive model was developed based on the collagen and elastic fiber morphologies and their rheological properties. The multiple protocol uniaxial data of Eshel and Lanir ('Effects of Strain Level and Proteoglycan Depletion on Preconditioning and Viscoelastic' Responses of Rat Dorsal Skin,' 2001, Ann. Biomed. Eng., 29, pp. 164-172) served to estimate the model's parameters and to validate its reliability. Parametric investigation was then used to test model parsimony (minimal form) and to elucidate the roles of response mechanism and the relative contribution of each constituent. The model predictions show a very. close fit to the data and good predictive capability. The results are consistent with the quasilinear viscoelastic response of both elastic and collagen fibers and are likewise consistent with the notion (supported by published experimental observations) that preconditioning in collagen is probably due to an increase in the fiber reference length and is due to strain softening (Mullins effect) in elastic fibers. The predictions also agree with the observed predominance of elastic fibers at low strains and suggest that as strain increases, collagen becomes predominant, but the effect of elastic fibers is still significant. The parsimony analysis of the 22 model parameters (18 are nonlinear in the model) points to the predominant role of viscoelasticity and preconditioning in both fibers, followed in order of importance by collagen waviness and elastic fiber nonlinearity. A reliable and comprehensive uniaxial constitutive law for the rat skin was developed based on the tissue microstructure and on its constituents' rheological properties. [DOI: 10.1115/1.3049479] Keywords: skin, uniaxial rheological properties, fiber morphology, viscoelasticity, preconditioning

The next generation of medical devices and engineered tissues will require development of scaffolds that mimic the structural and functional properties of the extracellular matrix (ECM) component of tissues. Unfortunately, little is known regarding how ECM microstructure participates in the transmission of mechanical load information from a global (tissue or construct) level to a level local to the resident cells ultimately initiating relevant mechanotransduction pathways. In this study, the transmission of mechanical strains at various functional levels was determined for three-dimensional (3D) collagen ECMs that differed in fibril microstructure. Microstructural properties of collagen ECMs (e.g., fibril density, fibril length, and fibril diameter) were systematically varied by altering in vitro polymerization conditions. Multiscale images of the 3D ECM macro- and microstructure were acquired during uniaxial tensile loading. These images provided the basis for quantification and correlation of strains at global and local levels. Results showed that collagen fibril microstructure was a critical determinant of the 3D global and local strain behaviors. Specifically, an increase in collagen fibril density reduced transverse strains in both width and thickness directions at both global and local levels. Similarly, collagen ECMs characterized by increased fibril length and decreased fibril diameter exhibited increased strain in width and thickness directions in response to loading. While extensional strains measured globally were equivalent to applied strains, extensional strains measured locally consistently underpredicted applied strain levels. These studies demonstrate that regulation of collagen fibril microstructure provides a means to control the 3D strain response and strain transfer properties of collagen-based ECMs. [DOI: 10.1115/1.3005331] Keywords: extracellular matrix, collagen, mechanotransduction, collagen fibril microstructure, strain transmission

We present and compare two different methods for numerically solving boundary value problems of gradient elasticity. The first method is based on a finite-element discretization using the displacement formulation, where elements that guarantee continuity of strains (i.e., [C.sup.1] interpolation) are needed. Two such elements are presented and shown to converge: a triangle with straight edges and an isoparametric quadrilateral. The second method is based on a finite-element discretization of Mindlin's elasticity with microstructure, of which gradient elasticity is a special case. Two isoparametric elements are presented, a triangle and a quadrilateral, interpolating the displacement and microdeformation fields. It is shown that, using an appropriate selection of material parameters, they can provide approximate solutions to boundary value problems of gradient elasticity. Benchmark problems are solved using both methods, to assess their relative merits and shortcomings in terms of accuracy, simplicity and computational efficiency. [C.sup.1] interpolation is shown to give generally superior results, although the approximate solutions obtained by elasticity with microstructure are also shown to be of very good quality. CE Database subject headings: Finite element method; Elastic analysis; Microstructures; Numerical models.

A finite strain micromorphic pressure-sensitive plasticity model is formulated starting with thermodynamically conjugate stresses and plastic deformation rates in the reduced dissipation inequality, written in the intermediate configuration. Isotropic linear elasticity and nonassociative Drucker--Prager plasticity with cohesion hardening/softening are assumed for the constitutive equations. The reduced dissipation inequality dictates three levels of plastic evolution: (1) evolution of [F.sup.p], the plastic part of the deformation gradient; (2) evolution of [[chi].sup.p], the plastic part of the microdeformation tensor; and (3) evolution of [bar.[nabla]][[chi].sup.p], the covariant derivative of [[chi].sup.p]. A semi-implicit time integration of the stress and plastic evolution equations is outlined after assuming small elastic deformations and Cartesian coordinates for the current configuration. CE Database subject headings: Plasticity; Strain; Pressure; Thermodynamics; Microstructure.

Negative-zero-positive index refraction was demonstrated numerically on the basis of full-wave analysis of a microstructured omega-type array and experimentally via angle resolved transmission measurement of a prism-type prototype. The experimental results are interpreted in terms of characteristic impedance and refractive index retrieved by a Fresnel inversion technique. The possibility to balance the dispersion characteristics with a negative-zero-positive index is demonstrated over X- and K u-bands. Index Terms--Composite right/left-handed metamaterial, negative index materials, negative refraction, retrieval technique.

The oceanic early-life history of Anguilla marmorata was examined in the southwestern Indian Ocean in Mayotte, Mauritius, and Reunion islands through otolith microstructural analysis. The study of the hatching dates, the first feeding check diameter (FFD), the leptocephalus (LD) and metamorphosis (MD) durations, the age at recruitment (AR), and the leptocephalus otolith growth rate (OGR) of glass eels revealed great variations in early-life traits and relationships between them. An agglomerative nesting analysis discriminated three early-life histories, differently represented according to the locality: (i) fast migrants with short LD, short MD, young AR, large FFD, and high OGR dominated in Reunion and Mayotte; (ii) midspeed migrants with intermediate LD, MD, AR, FFD, and OGR dominated in Mauritius; (iii) slow migrants with long LD, long MD, old AR, small FFD, and low OGR were recorded only in Mauritius. All possible strategies were not observed and therefore not successful at the sampling time. However, several were simultaneously expressed, which suggests larval migration plasticity at the population level. This evidence is crucial information regarding both the species dispersal capabilities and the evolution from short-migratory tropical species towards long-migratory temperate ones in the genus Anguilla. L'histoire de vie larvaire d'Anguilla mannorata a ete examinee dans le sud-ouest de 1'Ocean Indien a Mayotte, Maurice et La Reunion, par analyse de la microstructure des otolithes des civelles. Les traits de vie tels les dates d'eclosion, la marque de premiere prise de nourriture (FFD), les durees de vie leptocephale (LD) et de metamorphose (MD), l'age un recrutement (AR) et les taux de croissance de 1'otolithe (OGR), se sont montres variables et diversement correles. Trois types d'histoires de vie larvaire, discrimines par analyse de groupement agglomeratif hierarchique, ont ete observes a l'echelle geographique : (i) migrateurs rapides a LD et MD courtes, AR jeunes, et FFD et OGR importants, dominants a La Reunion et a Mayotte; (ii) migrateurs intermediaires a LD, MD, AR, FFD et OGR intermediaires, dominants a Maurice; (iii) migrateurs lents a LD et MD longues, AR avances, et FFD et OGR faibles, observes seulement a Maurice. Toutes les strategies possibles n'ont pas ete observees et ont donc ete inefficaces pendent la periode etudiee. L'expression simultanee de plusieurs strategies laisse supposer, a 1'echelle de la population, une plasticite de la migration larvaire chez A. mannorata. L'information est cruciale an regard des capacites de dispersion et du scenario d'evolution du genre Anguilla qui suppose une emergence des especes temperees aux migrations larvaires longues a partir des especes tropicales aux migrations larvaires courtes., Introduction The duration of a fish larval stage, and therefore, its metamorphosis timing, might be key factors determining distances of dispersal and species distribution range (Arai et al. 2001x; Hoareau [...]

Waste tire rubber constitute a serious worldwide problem due to the lack of landfills and the health hazards associated with these landfills. In addition to the environmental motivation for providing a means of recycling large quantities of waste tire rubbers, the use of tire rubber particles provides a new type of concrete that has unique mechanical and fracture criteria. This paper presents the results of recent experimental investigations on rubber concrete. Chipped and crumbed tire rubber particles were used to replace coarse and fine aggregate with different volume replacement levels. The mechanical and fracture properties of rubber concrete were examined. Quasi-brittle fracture mechanics models are used to determine the effect of incorporating tire rubber particles on the fracture performance of rubber concrete. Finally, some microstructural features of rubber concrete are also reported. It is concluded that the choice of the optimal replacement ratio of the tire rubber particles can yield concretes with desirable strength and fracture toughness criteria for different applications. CE Database subject headings: Cracking; Concrete aggregates; Rubber; Tires; Microstructure.

We investigated the influence of Zr[O.sub.2] on the microstructure and electromagnetic properties of MnZn ferrites by characterizing fracture surface micrographs, magnetic properties, and dc resistivity. Powders of [Mn.sub.o.68][Zn.sub.o.25][Fe.sub.2.07][O.sub.4] composition were prepared by the conventional ceramic technique. Toroidal cores were sintered at 1350 [degrees]C for 4 h in [N.sub.2]/[O.sub.2] atmosphere with 4% oxygen. The results show that the lattice constant and average grain size increase with Zr[O.sub.2] concentration, but excessive Zr[O.sub.2] concentration will result in exaggerated grain growth and porosity increase. The dc resistivity, activation energy, saturation magnetic flux density, and initial magnetic permeability increase monotonically when the Zr[O.sub.2] concentration is not more than 0.04 wt% and then decrease with further increase of Zr[O.sub.2] concentration. On the other hand, the porosity, drift mobility, resonance frequency, and core loss decrease initially and then increase with the increase of Zr[O.sub.2] concentration. Index Terms--Electromagnetic properties, microstructure, MnZn ferrites, Zr[O.sub.2] addition.

Diamond turning of microstructures on the surface of large cylindrical workpieces has become important with advances made in roll-to-roll manufacturing processes of optical films, drag reduction films, microfluidic devices, and organic electronic components. Micromachined cylindrical workpieces are used as production masters in various printing, embossing, and coating processes. The microstructures machined in this study were 18 [micro]m in height and had a pitch of 35 [micro]m. These dimensions required control of the location of the single crystal diamond cutting tool that was used for machining to submicrometer levels. The significant error sources identified in the machining process were thermal effects and deflections of the structural loop of the diamond turning machine (DTM) that led to registration errors of the cutting tool between consecutive passes. Environmental temperature variation errors (ETVEs) were measured and modeled as a function of long-term ambient temperature fluctuations. Also studied was the mechanical compliance of the structural loop of the DTM. The height adjustable tool stack and aerostatic spindle were identified as the most compliant components. The cutting forces for radius and V-shaped diamond cutting tools at various depths of cut were measured using the known compliance of the aerostatic bearing to predict workpiece deflections. [DOI: 10.1115/1.2951929] Keywords: microstructures, diamond turning machine (DTM), environmental temperature variation error (ETVE), compliance, stiffness, structural loop, cutting force

This paper presents a microfabricated planar patchclamp electrode design and looks at the impact of several physical characteristics on seal formation. The device consists of a patch aperture, 1.5-2.5 [micro]m in diameter and 7-12 [micro]m in depth, with a reverse-side deep-etched 80-[micro]m well. The patch aperture was coated with either thermal oxide or plasma-enhanced chemical vapor deposited (PECVD) Si[O.sub.2]. Some of the thermal oxide devices were converted into protruding nozzle structures, and some were boron-doped. Seal formation was tested with cultured N2a neuroblastoma cells. The PECVD oxide devices produced an average seal resistance of 34 M[OMEGA](n : 24), and the thermal oxide devices produced an average seal resistance of 96 M[OMEGA](n = 59). Seal resistance was found to positively correlate with patch aperture depth. Whole-cell recordings were obtained from 14% of cells tested with the thermal oxide devices, including a single recording where a gigaohm seal was obtained. Index Terms--Atomic force microscopy, biomedical transducers, electrophysiology, microelectrodes, microelectromechanical devices, micromachining, N2a cells, silicon.

Although 3-D out-of-plane structures based on the thermal shrinkage of polyimide-filled V-grooves have already been demonstrated, for large bending angles, this method typically requires several V-grooves and high curing temperatures, which are real-estate consuming and can damage temperature-sensitive components. In this paper, we show that the addition of an inorganic layer (called the boosting layer) beneath the V-grooves can significantly enlarge the bending angle without requiring more V-grooves or higher curing temperatures. For example, a 2-[micro]m-thick Si[O.sub.2] boosting layer can raise the bending angle of a single V-groove joint by a factor of seven. In addition, the boosting layer removes the requirement for a V-groove and permits the use of straight-wall dry-etched grooves, hence allowing a sharper curvature in a smaller area. Index Terms--Bilayer, self-assembly, thermal actuator, 3-D MEMS.

Echinoderm skeletal debris from the Early-Middle Cambrian boundary Micmacca Breccia of Morocco includes the oldest known holomeric columnals. The original calcite of these ossicles is coated and replaced by iron oxides, occasionally overlain by a late coating of silica, and preserves with high fidelity fine details of their three-dimensional microstructure. Irrespective of their external morphology, columnals can be divided into three groups based on the distribution of stereom microfabrics, which we suggest indicates the presence of at least three different holomeric stemmed taxa. One of these columnal types has well-developed galleried stereom perpendicular to its articulation facets, a sure sign that long, penetrative collagen bundles bound columnals together, as in modern stemmed crinoids. This columnal morphology also shows a primitive type of interlocking articulation, which we term parasymplexy and which may have helped to counter torsional stresses. The two other columnals either lacked fibrous connective tissue or had shallow, non-penetrative fibers between columnals.

We review our theoretical studies of the spin dynamics of ultrathin ferromagnetic films adsorbed on metallic substrates. Of interest are the spin waves with wave vector from the center of the Brillouin zone to its boundary. We utilize a realistic electronic structure for the substrate/adsorbate combination through an empirical tight binding description of the electronic structure of the materials involved, and the spin excitations are explored through the Random Phase Approximation. We can examine very large systems with this scheme, such as multilayer films placed on fully semi-infinite substrates. One principal finding is the adiabatic approximation breaks down qualitatively for these systems. We illustrate for Co films on Cu(100) where we also find excellent agreement with experiment. We conclude by discussing recent data for the Fe bilayer on W(110) where, after an excellent account of the measured exchange stiffness, we find the large wave vector spin waves generated by theory to be far too stiff. Index Terms--SPEELS, spin waves, ultrathin ferromagnets.

We present a systematic investigation of the magnetic properties and magnetization reversal processes in arrays of magnetic nanostructures. We observed in magnetic rings that the transitions between different equilibrium states are strongly dependent on magnetostatic interactions. For magnetic nanowires, a transition from coherent rotation to curling mode of reversal as the thickness of the wire is varied for fixed lateral dimensions was observed. We found in anti-dot nanostructures that the magnetic anisotropy can be controlled by engineering the lattice geometry. Index Terms--Magnetic nanostructures, magnetization reversal, magnetostatic interactions.

Volcanic activity results in a wide range of soil types with very unusual characteristics, the most remarkable of which are volcanic ash clays containing the clay minerals allophane and imogolite. In addition to these soils, volcanic activity often produces the special environmental conditions that result in the formation of diatomaceous soils, namely, water rich in dissolved silica. These soils consist of individual particles containing intraparticle voids filled with water, resulting in a very unique porous particle morphology that is quite different than stereotypical sedimentary soils. This paper presents a series of careful laboratory tests on samples of both materials found in Chile. These tests demonstrate that soils weathered from volcanic ash develop yield pressures that are similar to the preconsolidation pressure of sedimentary soils. This type of soil also shows a dramatic change in properties due to drying. In addition, diatomaceous soils and those containing allophane have very low densities, in spite of which they develop remarkably high shear strength. The need for their properties to be properly understood and taken into account in geotechnical design, especially seismic design, is emphasized, since the location of these soils generally coincides with earthquake activity, which, like volcanic activity, arises from tectonic plate interaction. CE Database subject headings: Soil dynamics; Microstructure; Volcanic ash; Seismic effects; Clays.

In this paper, phosphate and fluoride were added into the gypsum, respectively, to simulate phosphate and fluoride in the phosphogypsum. The affect of adding different impurities on setting time, compressive strength, and bulk density were inspected by simulation experiments. The pore structure of hardened gypsum was analyzed by mercury intrusion porosimetry, and the micromorphology of hardened gypsum was observed by scanning electric micrograph in sequence to get the influencing rule of different impurities and its contents on the performance and micromorphology of phosphogypsum. The results indicate that phosphate prolongs the setting time, while the fluoride shortens it. Meanwhile, the strength gets lower because of the coarsening crystal resulting from the phosphate and fluoride. CE Database subject headings: Phosphate; Fluoridation; Simulation; Microstructure; Gypsum.

Magnesium, the lightest structural metal, is of significance to improve energy efficiency in various applications. Mg / SiC nanocomposites were successfully fabricated by ultrasonic cavitation based dispersion of SiC nanoparticles in Mg melts. As compared to pure magnesium, the mechanical properties including tensile strength and yield strength of the Mg/ SiC nanocomposites were improved significantly, while the good ductility of pure Mg was retained. The grain size of the pure magnesium was refined significantly when SiC nanoparticles were dispersed in the Mg matrix. In the microstructure of Mg/ SiC nanocomposites, while there were still some SiC microclusters, most of the SiC nanoparticles were dispersed very well. Transmission electron microscopy study of the interface between SiC nanoparticles and magnesium matrix indicates that SiC nanoparticles bond well with Mg without forming an intermediate phase. [DOI: 10.1115/1.2823086]

The three-electrode microdischarge characteristics of ac plasma display panels are analyzed with a wide-sustain-discharge gap of 180 [micro]m. In particular, the luminance and consumed-power variations are examined as parameters of the operating frequency. It is found that the luminance per unit pulse decreases, and simultaneously, the consumed power per unit pulse increases with an increase in the operating frequency. For the wide-gap structure, the sustain voltage increases when increasing the operating frequency, thus causing the power consumption per unit pulse to be increased. However, the luminance per unit pulse decreases when increasing the sustain voltage, even though the power consumption per unit pulse increases with the sustain-voltage increase. As a result, it is observed that the self-erasing discharge between the sustain and address electrodes caused by the short pulsewidth under high frequency affects the luminance and consumed power. Due to the self-erasing discharge, the sustain voltage increases, and the discharge shrinkage phenomenon affecting the luminance characteristics occurs under high frequency that is up to 200 kHz with a wide-sustain-discharge gap of 180 [micro]m. Index Terms--Discharge shrinkage, frequency effect, luminance, luminance per unit pulse, luminous efficiency, serf-erasing discharge, wide-sustain gap (180 [micro]m) structure.

This paper develops a microscopic homogenization based continuum damage mechanics (HCDM) model framework for fiber reinforced composites undergoing interfacial debonding. It is an advancement over the 2D HCDM model developed by Raghavan and Ghosh (2005, 'A Continuum Damage Mechanics Model for Unidirectional Composites Undergoing Interfacial Debonding,' Mech. Mater., 37(9), pp. 955-979), which does not yield accurate results for nonproportional loading histories. The present paper overcomes this shortcoming through the introduction of a principal damage coordinate system (PDCS) in the HCDM representation, which evolves with loading history. The material behavior is represented as a continuum constitutive law involving a fourth order orthotropic tensor with stiffness characterized as a macroscopic internal variable. The current work also extends the model of Raghavan and Ghosh to incorporate damage in 3D composites through functional forms of the fourth order damage tensor in terms of macroscopic strain components. The model is calibrated by homogenizing the micromechanical response of the representative volume element (RVE) for a few strain histories. This parametric representation can significantly enhance the computational efficiency of the model by avoiding the cumbersome strain space interpolations. The proposed model is validated by comparing the CDM results with homogenized micromechanical response of single and multiple fiber RVEs subjected to arbitrary loading history. Keywords: continuum damage mechanics, homogenization, interfacial debonding, cohesive zone element, principal damage coordinate system

The numerous nonmyocytes present within the myocardium may establish electrical connections with myocytes through gap junctions, formed naturally or as a result of a cell therapy. The strength of the coupling and its potential impact on action potential characteristics and conduction are not well understood. This study used computer simulation to investigate the load-induced electrophysiological consequences of the coupling of myocytes with fibroblasts, where the fibroblast resting potential, density, distribution, and coupling strength were varied. Conduction velocity (CV), upstroke velocity, and action potential duration (APD) were analyzed for longitudinal and transverse impulse propagation in a two-dimensional microstructure tissue model, developed to represent a monolayer culture of cardiac cells covered by a layer of fibroblasts. The results show that 1) at weak coupling (8 nS), all of the effects saturated; and 4) APD at 90% repolarization was usually prolonged by 0-20 ms (up to 60-80 ms for high fibroblast density and coupling) by the coupling to fibroblasts. The changes in APD depended on the fibroblast resting potential. This complex, coupling-dependent interaction of fibroblast and myocytes also has relevance to the integration of other nonmyocytes in the heart, such as those used in cellular therapies. computer modeling; electrophysiology; nonmyocytes; gap junctions; fibrosis

Co-base superalloys are commonly used for vanes and parts of the combustion chamber in gas turbine engines. The Co-base superalloys are primarily solid solution strengthened and have good resistance to hot corrosion, creep, and thermal fatigue. In particular, Co-base alloy X-40 was used to fabricate the first stage NGV airfoils of T56 series engines; inspections after service have revealed that X-40 airfoils suffered from severe thermal fatigue damages. In this study, a new braze repair scheme is proposed; in which Ni-base alloys are used to repair the X-40 substrate in both narrow and wide gap configurations. Metallographic examination, X-ray mapping, and energy dispersive spectroscopy semiquantitative compositional analyses were carried out to study the microstructures in the braze joint in the as-brazed condition and after thermal exposure at 950[degrees]C. The results obtained so far suggest the formation of Cr-rich borides, eutectic phases, and various carbides in the joint. No TCP phases were found in the brazed joint and base metals adjacent to the joint. The high carbon content in the alloy X-40 may have played an important role in preventing the formation of TCP phases during brazing and subsequent thermal exposure. Keywords: braze repair, wide gap brazing, Co-base superalloy X40, microstructure

A study was conducted to determine the quantity of water bound by hydration, the products formed during hydration, the microstructures, and the mechanical properties as a function of the relative content of reactive magnesium oxide (magnesia, MgO), pulverized fuel ash (pfa), portland cement (PC), and water used to prepare the mixes. It was confirmed that hydration of MgO leads to the formation of brucite and that PC forms its normal hydration products, even when both materials are present together. It was found that calculated changes in porosity and consumption of water during hydration based on the proposed hydration reactions agree well with the measurements. It was also found that the stiffness and strength improve directly proportional to the PC content. It is proposed that the lower strength of mixes with high reactive MgO contents is due to a combination of their high water demand and the difference in morphology between brucite and C-S-H gel. DOI: 10.1061/(ASCE)0899-1561 (2008)20:5(375) CE Database subject headings: Construction materials; Portland cement; Fly ash; Admixtures; Mechanical properties; Compressive strength; Stiffness; Hydration; Microstructure.

Trabecular bone fracture is closely related to the trabecular architecture, microdamage accumulation, and bone tissue properties. Micro-finite-element models have been used to investigate the elastic and yield properties of trabecular bone but have only seen limited application in modeling the microstructure dependent fracture of trabecular bone. In this research, dynamic fracture in two-dimensional (2D) micrographs of ovine (sheep) trabecular bone is modeled using the cohesive finite element method. For this purpose, the bone tissue is modeled as an orthotropic material with the cohesive parameters calculated from the experimental fracture properties of the human cortical bone. Crack propagation analyses are carried out in two different 2D orthogonal sections cut from a three-dimensional 8 mm diameter cylindrical trabecular bone sample. The two sections differ in microstructural features such as area fraction (ratio of the 2D space occupied by bone tissue to the total 2D space), mean trabecula thickness, and connectivity. Analyses focus on understanding the effect of the rate of loading as well as on how the rate variation interacts with the microstructural features to cause anisotropy in microdamage accumulation and in the fracture resistance. Results are analyzed in terms of the dependence of fracture energy dissipation on the microstructural features as well as in terms of the changes in damage and stresses associated with the bone architecture variation. Besides the obvious dependence of the fracture behavior on the rate of loading, it is found that the microstructure strongly influences the fracture properties. The orthogonal section with lesser area fraction, low connectivity, and higher mean trabecula thickness is more resistant to fracture than the section with high area fraction, high connectivity, and lower mean trabecula thickness. In addition, it is found that the trabecular architecture leads to inhomogeneous distribution of damage, irrespective of the symmetry in the applied loading with the fracture of the entire bone section rapidly progressing to bone fragmentation once the accumulated damage in any trabeculae reaches a critical limit. [DOI: 10.1115/1.2903434] Keywords: trabecular bone, fracture, cohesive finite element method

A new micromechanism, the spherical bistable micromechanism (SBM), is described. The SBM has several advantageous features, which include two stable positions that require power only in transitioning from one position to the other; robustness against small disturbances; and a compact footprint and an output link with a stable out-of-plane orientation. The SBM may be useful in applications such as 2D optical mirror arrays or in erecting out-of-plane structures. [DOI: 10.1115/1.2885079]

In this work, a new compliant bistable mechanism design is introduced. The combined use of pseudo-rigid-body model (PRBM) and the Elastica buckling theory is presented for the first time to analyze the new design. This mechanism consists of the large deflecting straight beams, buckling beams, and a slider. The kinematic analysis of this new mechanism is studied, using nonlinear Elastica buckling beam theory, the PRBM of a large deflecting cantilever beam, the vector loop closure equations, and numerically solving nonlinear algebraic equations. A design method of the bistable mechanism in microdimensions is investigated by changing the relative stiffness of the flexible beams. The actuation force versus displacement characteristics of several cases is explored and the full simulation results of one of the cases are presented. This paper demonstrates the united application of the PRBM and the buckling Elastica solution for an original compliant mechanism kinematic analysis. New compliant mechanism designs are presented to highlight where such combined kinematic analysis is required. [DOI: 10.1115/1.2839009] Keywords: compliant mechanisms, bistable micromechanisms, pseudo-rigid-body model, large-deflection analysis, Elastica theory, buckling beam theory

This paper presents a novel resonant-microsensor platform for chemical and biological sensing applications in gaseous and liquid environment. The disk-shape microstructure is operated in a rotational in-plane mode with typical resonance frequencies between 300 and 1000 kHz. By shearing the surrounding fluid instead of compressing it, damping is reduced, and high quality factors are achieved. The resonators feature electrothermal excitation elements and a piezoresistive Wheatstone bridge for detection, sensitive only to the in-plane rotational vibration mode. Microresonators with different dimensions have been fabricated and extensively characterized, achieving quality factors of up to 5800 in air. First tests performed in water after parylene coating show a Q factor of approximately 100. Short-term frequency stabilities obtained from Allan-variance measurements with 1-s gate time are as low as 1.2 x [10.sup.-8] in air and 2.3 x [10.sup.-6] in water. An analytical model describing the mechanical behavior of the disk resonators, represented by a simple harmonic oscillator, is derived. In particular, expression for the resonance frequency and quality factor of the disk resonators subject to air/liquid damping are proposed and compared with experimental results. [2006-0113] Index Terms--Mass-sensitive sensor, quality factor, resonant sensor, resonator, viscous damping.

Human remains from peat bogs, called 'bog bodies,' have yielded valuable insights into human history because of their excellent preservation of soft tissue. On the other hand, the acidic environment of the peat leads to an extensive demineralization of skeletal elements, complicating their analysis. We studied the skeleton of the bog body 'Moora' dated to ~650 B.C. Nondestructive evaluation of the bone was made using contact X-rays, peripheral quantitative computed tomography (pQCT) analysis, multislice computed tomography (CT) and high resolution micro computed tomography ([micro]CT) imaging. Two thousand seven hundred years in the acidic environment of the bog led to a loss of 92.7% of bone mineral density. Despite this demineralization and in contrast to other bog bodies, the spatial structure of the bones of 'Moora' is exceptionally well preserved. We found Harris lines and were able to obtain the first three-dimensional data on the trabecular microstructure of the bone of a young woman from the early Iron Age. KEY WORDS bog body; Moora; [micro] CT; pQCT; contact X-ray

This paper describes further developments of a two-moment warm rain bulk microphysics scheme suitable for addressing the indirect impact of atmospheric aerosols on ice-free clouds in large-eddy simulation (LES) models. The emphasis is on the prediction of supersaturation, activation of cloud droplets, and the representation of microphysical transformations during parameterized turbulent mixing. A comprehensive approach is proposed that is capable of simulating droplet activation at the cloud base, in the cloud interior due to increasing updraft strength, and at the lateral edges due to entrainment. Such an approach requires high spatial resolution to capture maximum supersaturation at cloud base as well as to resolve entraining eddies that lead to additional activation above the cloud base. This approach can be used as a benchmark for developing and testing schemes suitable for lower spatial resolutions. A novel approach for predicting the supersaturation field is proposed, with an emphasis on its application in an Eulerian framework. This approach produces consistency among the thermodynamic variables and mitigates the problem of spurious cloud-edge supersaturation noted in the past. A new subgrid scheme is also developed to treat microphysical transformations during turbulent entrainment and mixing. This scheme is designed to be as flexible as possible, allowing for the entire range of mixing scenarios from homogeneous to extremely inhomogeneous. The above developments are applied in 2D simulations of moist convection for an idealized rising thermal, assuming either pristine or polluted aerosol conditions. The mixing scenario has a substantial impact on the cloud microphysical and optical properties. As expected, extremely inhomogeneous mixing results in substantially smaller mean droplet number concentration, larger effective radius, and smaller cloud optical depth compared to the run with homogeneous mixing. The subgrid mixing of cloud condensation nuclei (CCN) and formation of CCN from evaporated droplets during extremely inhomogeneous mixing are relatively less important for this case.

Melanin-concentrating hormone (MCH) and neuropeptide Y (NPY) are orexigenic peptides found in hypothalamic neurons that project throughout the forebrain and hindbrain. The effects of fourth ventricle (4V) infusions of NPY (5 [micro]g) and MCH (5 [micro]g) on licking for water, 4 mM saccharin, and sucrose (0.1 and 1.0 M) solutions were compared to identify the contributions of each peptide to hindbrain-stimulated feeding. NPY increased mean meal size only for the sucrose solutions, suggesting that caloric feedback or taste quality is pertinent to the orexigenic effect; MCH infusions under identical testing conditions failed to produce increases for any tastant. A second experiment also observed no intake or licking effects after MCH doses up to 15 [micro]g, supporting the conclusion that MCH-induced orexigenic responses require forebrain stimulation. A third experiment compared the 4V NPY results with those obtained after NPY infusions (5 [micro]g) into the third ventricle (3V). In contrast to the effects observed after the 3V NPY injections and previously reported forebrain intracerebroventricular (ICV) NPY infusion studies, 4V NPY failed to increase meal frequency for any taste solution or ingestion rate in the early phases of the sucrose meals. Overall, 4V NPY responses were limited to intrameal behavioral processes, whereas forebrain ICV NPY stimulation elicited both consummatory and appetitive responses. The dissociation between MCH and NPY effects observed for 4V injections is consistent with reports that forebrain ICV injections of MCH and NPY produced nearly dichotomous effects on the pattern of licking microstructure, and, collectively, the results indicate that the two peptides have separate sites of feeding action in the brain. taste; feeding; microstructure; intake

The influence of fiber inclusion on the abrasion resistance of concrete specimens of various mix compositions was measured by means of a rolling-wheel apparatus. Microhardness, mercury intrusion porosimetry, and petrographic examinations were used to investigate the microstructural features of the cement matrix of the exposed surfaces. The results indicate that variations in the water-cement ratio for both plain and fiber-reinforced concrete mixes influence the microhardness and the pore structure of the surface matrix. The petrographic examination revealed that variations in the water-cement ratio for both plain and fiber-reinforced concrete influenced the formation and dimensions of the locally abundant microcracks observed below the parts of the surfaces subjected to abrasion testing. For the systems investigated, this was attributed to the phenomenon of rolling contact fatigue. DOI: 10.1061/(ASCE)0899-1561(2008)20:2(157) CE Database subject headings: Floors; Concrete, reinforced; Fiber reinforced materials; Material tests; Microstructures; Contact pressure; Porosity.

This paper presents the experimental validation of a macroscopic model of unsaturated flow in double-porosity soils, which was developed using the asymptotic homogenization method. The model was implemented into a code which enables micro--macro coupled calculations of macroscopically one-dimensional and microscopically three-dimensional problems. A series of drainage experiments were carried out in a column filled with a double porosity medium. The porous medium is composed of Hostun sand and porous spheres made of sintered clay, periodically distributed in the sand. The characteristic pores sizes of the two media differ by two orders of magnitude. During the experiments the water content evolution inside the column, the capillary pressure, and the flux at the bottom of the column were measured. The numerical simulations results showed a good agreement with the experimental data, confirming the predictive ability of the model. The experimental and numerical evidence of the influence of the microporous inclusions on the flow dynamics (flux retardation, water retention in the microporosity), is clearly shown. DOI: 10.1061/(ASCE)1090-0241(2008)134:2(231) CE Database subject headings: Unsaturated soils; Nonuniform flow; Drainage; Microstructure; Heterogeneity; Scale effect; Gamma rays; Model verification; Porous media.

An attempt has been taken to investigate the microstructure and mass transfer properties of polycaprolactone diol ([M.sub.n] = 2000 g [mol.sup.-1], PCL 2000)-based dense segmented polyurethane (SPU) membrane as a function of hard segment (HS) content. Structure of SPUs were investigated by Fourier transform infrared analysis, wide angle X-ray diffraction, differential scanning calorimetry, dynamic mechanical thermal analysis, and scanning electron microscopy (SEM). On the other hand, mass transfer properties were measured by equilibrium sorption, dynamic sorption, and water vapor permeability measurements. From the experimental results, it was observed that with the increasing HS content in SPU the percentage crystallinity decreases, whereas the glassy state storage modulus increases. α transition temperature of polyurethane copolymers also increases with increasing HS content. SEM micrograph shows the dense surface structure of SPU films. Mass transfer rate of dense polyurethane membranes decreases with increasing HS content. In contrast, hydrophilic segment and soft segment crystal melting could enhance the mass transfer properties. POLYM. ENG. SCI., 48:233-239, 2008. © 2007 Society of Plastics Engineers, INTRODUCTION Segmented polyurethanes (SPUs) are composed of flexible soft segment and rigid hard segment (HS). Soft block is usually polyether or polyester diol, while the hard block or HS is [...]

Ambient inclusion trails (AIT) are enigmatic microtubular structures created by the migration of mineral crystals through a lithified substrate. The decomposition of organic material has been suggested as the driving force for the crystal migration, but has yet to be rigorously tested. AIT may hold potential as a biosignature for investigating early life on Earth if the associated organic material can be shown to be biological. This paper attempts to test the formation mechanism and biogenicity of AIT from the c. 3400 Ma Strelley Pool sandstone of Western Australia using NanoSIMS technology. In doing so, we demonstrate the unique ability of the NanoSIMS to combine sub-micron scale imaging with in situ chemical and isotopic data, thereby enhancing our ability to evaluate the biogenicity criteria for Archaean microstructures. Enrichments of a suite of major elements (C, N, P, S) and trace elements (Co, Fe, Ni, Zn), often associated with biological processes, are found within several AIT in this sandstone. C and N enrichments are most common along AIT margins, and correlate with depletions of Si, O, Ca and Mg, indicating that this material is indeed organic in nature. [[delta].sup.13]C values of this carbonaceous material average -26 [per thousand]. Petrographic observations show that some of the AIT occur in the centre of detrital sandstone grains where they were sealed from later fluid flow and therefore preserve primary Archaean (bio)geochemistry. In contrast, AIT found around the outer edges of sandstone grains may contain more recent organic material introduced by later fluid migration and are an unreliable biosignature. Using the petrographic and geochemical data a multi-stage model for AIT formation and subsequent diagenetic modification is proposed. The possible sources of the primary organic material are discussed and we conclude that the data are consistent with a biological origin for these AIT. An abiogenic origin is more difficult to sustain but cannot yet be completely excluded for AIT in general.

[1] This study presents a model of successive emplacement of three granite plutons in transtensional deformation regime controlled by the preextensional synconvergent history of the lower and middle crust in the central Vosges Mountains (France). The complex compressional orogenic structure recorded a vertical exhumation-related fabric in midcrustal levels which was overprinted by the regional extension. Three successively emplaced granite sheets exploited the inherited vertical anisotropy obliquely oriented with respect to the applied tensile stress. This progressive opening of original steep fabric leads to the sequential generation of free spaces toward the south, and emplacement and deformation of granite sheets. Repeated granite intrusions are responsible for reheating of southern margins of the already partially solidified granites, which became reactivated under lower ambient thermal conditions related to overall ~6 Ma cooling of rapidly exhumed crust. The results of anisotropy of magnetic susceptibility (AMS) fabric modeling suggest a highly partitioned oblique extension divided into pure shear-dominated deformation close to the central and northern margins of intrusions and wrenchdominated shear along the southern margins. The AMS modeling suggests the importance of overprinting of the intrusive fabrics by the transtensional deformation. doi: 10.1029/2006TC002035.

In the environment, organic micropollutants such as pharmaceuticals can be degraded via various biotic and abiotic transformation routes. In surface waters, for example, photodegradation may constitute a relevant natural attenuation process for drug residues that have been discharged from sewage treatment facilities. In the present work, the photochemical fate of the prodrug enalapril (376 Da, [C.sub.20][H.sub.28][N.sub.2][O.sub.5]) and its active metabolite enalaprilat (348 Da, [C.sub.18][H.sub.24][N.sub.2] [O.sub.5]), a hypotensive cardioprotector previously reported to occur in contaminated rivers, was investigated in aqueous media under the influence of irradiation generated by a sunlight simulator. The experiments yielded three detectable photodegradates for enalapril (346 Da, 2 x 207 Da) whereas the photolysis of enalaprilat went hand in hand with the intermittent buildup of one photodegradate (304 Da). Fragmentation patterns of the parent compounds were established on a hybrid quadrupole-linear ion trap-mass spectrometer exploiting its M[S.sup.3] capabilities. Accurate mass measurements recorded on a hybrid quadrupole-time-of-flight instrument in MS/MS mode allowed us to propose elemental compositions for the molecular ions of the degradates (346 Da, [C.sub.19][H.sub.26][N.sub.2][O.sub.4]; 207 Da, [C.sub.12][H.sub.17]N[O.sub.2]; 304 Da, [C.sub.17][H.sub.24] [N.sub.2][O.sub.3]) as well as of their fragment ions. Based on these complementary data sets from the two distinct mass spectrometric instruments, plausible structures were postulated for the four photodegradates. The compounds formed by enalapril corresponded to the loss of formaldehyde out of the proline residue (346 Da), cleavage of the central amide bond (207 Da) followed by migration of the ethylester side chain (207 Da) while decarboxylation of the free carboxylic acid was described for enalaprilat (304 Da). The study emphasized the potential of sunlight for breaking down an environmentally relevant drug and its metabolite.

Welding generates thermal distortion and residual stress, and it is well known that they affect the performance of welded structures by contributing to brittle fracture, fatigue, buckling deformation, and stress-corrosion cracking. Welding distortions and residual stresses can possibly be controlled and reduced by using counter-measures. Not only thermal stress behavior but also the prediction of the microstructural phase during welding heat cycles is very important. High-strength steels or martensitic stainless steels are used in many power plant components, and the effect of phase transformation on the mechanical behavior during welding of these steels becomes much larger than that of mild steels and austenitic stainless steels. Simultaneous simulations of the thermal stress and microstructure during welding are necessary for a precise evaluation. In this paper, an analytical method and several applications using actual components are introduced in order to emphasize the effect of the microstructure on the weld residual stress analysis. [DOI: 10.1115/1.2767344]

Centromeres are defining features of eukaryotic chromosomes, providing sites of attachment for segregation during mitosis and meiosis. The fundamental unit of centromere structure is the centromeric nucleosome, which differs from the conventional nucleosome by the presence of a centromere-specific histone variant (CenH3) in place of canonical H3. We have shown that the CenH3 nucleosome core found in interphase Drosophila cells is a heterotypic tetramer, a 'hemisome' consisting of one molecule each of CenH3, H4, H2A, and H2B, rather than the octamer of canonical histones that is found in bulk nucleosomes. The surprising discovery of hemisomes at centromeres calls for a reevaluation of evidence that has long been interpreted in terms of a more conventional nucleosome. We describe how the hemisome structure of centromeric nucleosomes can account for enigmatic properties of centromeres, including kinetochore accessibility, epigenetic inheritance, rapid turnover of misincorporated CenH3, and transcriptional quiescence of pericentric heterochromatin. Structural differences mediated by loop 1 are proposed to account for the formation of stable tetramers containing CenH3 rather than stable octamers containing H3. Asymmetric CenH3 hemisomes might interrupt the global condensation of octameric H3 arrays and present an asymmetric surface for kinetochore formation. We suggest that this simple mechanism for differentiation between centromeric and packaging nucleosomes evolved from an archaealike ancestor at the dawn of eukaryotic evolution. hemisome | histones | centromere CENP-A

The localized potential gradients created by a microplasma are capable of trapping and concentrating micro- and nanoparticles. In this paper, argon microplasma is generated within a 350-[micro]m discharge gap formed within a microstrip transmission line. Melamine formaldehyde particles (1 [micro]m) are released approximately 2 cm away from the microplasma. The microparticles are then negatively charged by stray electrons, electrostatically drawn toward the potential well of the microplasma, and trapped within the microplasma. The particles are observed to form Coulomb crystals. Time-of-flight experiments show that the particles are trapped in the microplasma by balancing the electrostatic force of the potential well against the molecular drag force. Pulsed plasma data show that the particles retain a net negative charge after the plasma has been extinguished, allowing detection and sorting by electrostatic methods. Index Terms--Dusty plasma, microparticle, microplasma.

This paper presents a deep reactive-ion etching (DRIE)-based post-CMOS micromachining process thai provides robust electrically isolated single-crystal silicon (SCS) microstructures for integrated inertial sensors. Several process issues arise from previously reported three-axis CMOS microelectromechanical system (MEMS) accelerometers, including sidewall contaminations of SCS microstructures in plasma etch and a severe silicon undercut caused by overheating of suspended microstructures. Solutions to these issues have been found and are discussed in detail in this paper. In particular, a lumped-element model is developed to estimate the temperature rise on suspended microstructures in a silicon DRIE process. Based on the thermal modeling and experiments, a thick photoresist layer has been used as a thermal path to avoid the severe silicon undercut. The sidewall contamination problem is also eliminated using the modified CMOS-MEMS process. A three-axis accelerometer with a low-noise, low-power on-chip amplifier has been successfully fabricated using the new process. Footing effect was observed on the backside of the sensor microstructure, but it has little effect on the structural integrity and sensitivity of the sensor. [2007-0012] Index Terms--Complementary metal-oxide-semiconductor microelectromechanical system (CMOS-MEMS), contaminations, deep reactive-ion etching (DRIE), integrated sensors, overheating, single-crystal silicon (SCS) microstructures, undercut.

Tra1 is an essential component of the Saccharomyces cerevisiae SAGA and NuA4 complexes. Using targeted mutagenesis, we identified residues within its C-terminal phosphatidylinositol-3-kinase (PI3K) domain that are required for function. The phenotypes of tra1-[P.sub.3408]A, [S.sub.3463]A, and [SRR.sub.3413-3415]AAA included temperature sensitivity and reduced growth in media containing 6% ethanol or calcofluor white or depleted of phosphate. These alleles resulted in a twofold or greater change in expression of ~7% of yeast genes in rich media and reduced activation of PH05 and ADH2 promoters. Tra1-[SRR.sub.3413] associated with components of both the NuA4 and SAGA complexes and with the Gal4 transcriptional activation domain similar to wild-type protein. Tral-[SRR.sub.3413] was recruited to the PHO5 promoter in vivo but gave rise to decreased relative amounts of acetylated histone H3 and histone H4 at SAGA and NuA4 regulated promoters. Distinct from other components of these complexes, tra1-[SRR.sub.3413] resulted in generation-dependent telomere shortening and synthetic slow growth in combination with deletions of a number of genes with roles in membrane-related processes. While the tra1 alleles have some phenotypic similarities with deletions of SAGA and NuA4 components, their distinct nature may arise from the simultaneous alteration of SAGA and NuA4 functions.