bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Study of Structural Properties of YBa2Cu3O7 Thin Films on SrTiO3 Single Crystal and Bicrystal Substrates by X- ray Diffraction
Authors: Navacerrada M.A. , Mehta A. , Sahibudeen H.S. , Acrivos J.V. 
Published: June 2019

AbstractWe present a comparative study in terms of structural properties deduced from X - ray diffraction diagrams between YBa2Cu3O7 (YBCO) thin films fabricated on SrTiO3 (STO) single crystal substrates and bicrystallines substrates with a symmetrical tilt angle of 24 degrees. Periodic Lattice Distortions (PLD) have been observed around different Bragg peaks in YBCO thin films deposited on STO bicrystals while only diffraction peaks have been measured in the diagrams corresponding to the YBCO thin films deposited on STO single crystal substrates. Only in regions situated a 3.5 mm at both sides of the grain boundary the PDL have been investigated. Scans along different (h, k, l) directions allow us to conclude that the qPLD vector associated to the distortion is along the (h,-k,0) direction. However, we found that the amplitude of the components of the qPLD vector depend on the Bragg peak chosen. We believe such a result indicates that we have not a PDL with a simple qPLD vector. In this line, other (h, k, l) directions must be investigated to deduce the exact origin of the qPLD vector. Nevertheless, independently on the qPLD vector associated to the PLD, we believe that such a distortion in the lattice is a consequence of the stress field induced by the grain boundary in the YBCO thin film deposited on the bricrystal.
Low-damage patterning of pentacene using a SiNx/PVA-photoresistmulti-layermask
Authors: Hirai Nobukazu , Yoneya Nobuhide , Kawashima Noriyuki , Noda Makoto , Nomoto Kazumasa , Wada Masaru , Kasahara Jiro 
Published: June 2019

AbstractWe have developed a photolithographic technique of patterning a pentacene layer with low damage using a SiNx/poly(vinyl alcohol) (PVA) photoresist multi-layer mask. We used a hexavalent chromium-free PVAphotoresist. By inserting a SiNx buffer layer between the pentacene layer and the PVAphotoresist layer, we could suppress an increase in off current caused by interaction between pentacene and the photosensitive functional group in the PVA photoresist. In the patterning process, we found that carriers generated by O2-plasma doped into the pentacene layer and the off current of the pentacene thin-film transistor (TFT) increased.We also found that successive annealing caused de-doping of the pentacene layer and reduced off current of the pentacene TFT.We investigated the density of doped carriers using a simplemodel of a planer pentacene diode aswell as a pentaceneTFT.
Novel 3-D MEMS Approach to Digitally Printing Organic Semiconductors
Authors: Schoeppler Martin W. 
Published: June 2019

AbstractInk jet printheads are now widely used in manufacturing processes that require precise dispensing of materials. In response to requirements for dispensing novel electronic fluids, we are developing next generation jetting technology based on our silicon MEMS technology with a three-dimensional silicon technology and a piezo-based pumping chamber integrated into the chip structure. Examples of opportunities and applications in electronics packaging for MEMSbased ink jet technology will be presented.
High-Speed Photography of Human Trabecular Bone during Compression
Authors: Thurner Philipp J. , Erikson Blake , Schriock Zachary , Langan John , Scott Jeff , Zhao Maria , Fantner Georg E. , Turner Patricia , Kindt Johannes H. , Schitter Georg , Hansma Paul K. 
Published: June 2019

AbstractThe mechanical properties of healthy and diseased bone tissue are extensively studied in mechanical tests. Most of this research is motivated by the immense costs of health care and social impacts due to osteoporosis in post-menopausal women and the aged. Osteoporosis results in bone loss and change of trabecular architecture, causing a decrease in bone strength. To address the problem of assessing local failure behavior of bone, we combined mechanical compression testing of trabecular bone samples with high-speed photography. In this exploratory study, we investigated healthy, osteoarthritic, and osteoporotic human vertebral trabecular bone compressed at high strain rates simulating conditions experienced in individuals during falls. Apparent strains were found to translate to a broad range of local strains. Moreover, strained trabeculae were seen to whiten with increasing strain. We hypothesize that the effect seen is due to microcrack formation in these areas, similar to stress whitening seen in synthetic polymers. From the results of a motion energy filter applied to the recorded movies, we saw that the whitened areas are, presumably, also of high deformation. We believe that this method will allow further insights into bone failure mechanisms, and help toward a better understanding of the processes involved in bone failure.
Mechanisms Governing the Inelastic Deformation of Cortical Bone
Authors: Mercer C. , Wang R. , Evans A. G. 
Published: June 2019

AbstractTo understand the inelastic response of bone, a two-part investigation has been conducted. In the first, a flexural test protocol has been designed and implemented that monitors the axial and transverse strains on both the tensile and compressive surfaces of cortical bone. The results are used to assess the relative contributions of dilatation and shear to the inelastic deformation. Unload/reload tests have characterized the hysteresis and provided insight about the mechanisms causing the strain. These tests reveal strain healing attributed to sacrificial bonds. The second part devises a model for the stress/strain response, based on a recent assessment of the nano-scale organization of the collagen fibrils and mineral platelets. The model rationalizes the inelastic deformation in tension, as well as the permanent strain and hysteresis.
On the Origin of Stiffening in Biopolymers
Authors: Giessen Erik Van der , Koeman Teun , Dillen Teun Van , Onck Patrick 
Published: June 2019

AbstractStrain stiffening of protein networks is explored by means of a finite strain analysis of a two-dimensional network model of cross-linked semiflexible filaments. The results show that stiffening is caused by non-affine network rearrangements that govern a transition from a bending dominated response at small strains to a stretching dominated response at large strains. Thermally-induced filament undulations only have a minor effect; they merely postpone the transition.
A new technique for imaging Mineralized Fibrils on Bovine Trabecular Bone Fracture Surfaces by Atomic Force Microscopy
Authors: Kindt Johannes H. , Fantner Georg E. , Thurner Philipp J. , Schitter Georg , Hansma Paul K. 
Published: June 2019

AbstractHigh resolution atomic force microscopy (AFM) images of bovine trabecular bone fracture surfaces reveal individual fibrils coated with extrafibrillar mineral particles. The mineral particles are distinctly different in different regions. In some regions the particles have average dimensions of (70 ± 35) nm along the fibrils and about half that across the fibrils. In other regions they are smaller and rounder, of order (53 ± 14) nm both along and across the fibrils. In other regions they are smaller and rounder, of order (25 ± 15) nm both along and across the fibrils, with more rounded top surfaces.Significantly, we rarely observed bare collagen fibrils. If the observed particles can be verified to be native extrafibrillar mineral, this could imply that the fractures which created the observed areas propagated within the mineralized extrafibrillar matrix.
Collagen Content and Organization Relate to Bone Nanomechanical Properties
Authors: Donnelly Eve , Williams Rebecca M. , Baker Shefford P. , Meulen Marjolein C. H. van der 
Published: June 2019

AbstractCancellous bone plays an important load-bearing role in the skeleton, yet relatively little is known about the microstructure-mechanical property relationships of the tissue at the sub-10 [.proportional]m level. Cancellous tissue is characterized by a layered microstructure with variable proportions of collagen and mineral. The lamellar material is substantially stiffer than the interlamellar material at the nanomechanical level. However, the microstructural origin of the observed differences in mechanical properties of these structures has not been investigated. In this study, second harmonic generation microscopy was used to examine collagen in human vertebral cancellous bone. At the same location in the tissue, nanoindentation was used to assess the indentation modulus of lamellar and interlamellar bone. The stiff lamellae corresponded to areas of highly ordered, collagen-rich material, while the compliant interlamellar regions corresponded to areas of unoriented or collagen-poor material. The lamellar bone was approximately 30% stiffer and contained approximately 50% more oriented collagen than the interlamellar bone. These observed differences in the mechanical properties and collagen content and organization of lamellar and interlamellar tissue are consistent with previous scanning electron microscopy studies showing greater mineral and collagen content and organization in lamellar bone. Given the well-known coupling between collagen and mineral in bone tissue, the mineral distribution may mirror that of the aligned collagen. However, similar measurements of local variations in mineral content are needed to confirm this hypothesis and may provide additional insights into the tissue nanomechanical behavior.
A Two-Dimensional Free Energy Model for Single Crystalline Ferroelectrics
Authors: Kim Sang-Joo , Seelecke Stefan , Ball Brian L. , Smith Ralph C. , Lee Chang-Hoan 
Published: June 2019

AbstractThe one-dimensional free energy model for ferroelectric materials developed in [1-3] is general-ized to two dimensions. The proposed two-dimensional energy potential consists of four energy wells corresponding to four variants of the material, four saddle points representing the barriers for 900 switching processes, and a local energy maximum across which 1800-switching processes take place. The free energy potential is combined with the evolution equations based on the theory of thermally activated processes. The prediction of the model is compared with the recent measurements on a Ba- TiO3 single crystalline ferroelectric in [4]. The responses of the model at various loading frequencies are calculated and the kinetics of 900 and 1800 switching processes are discussed.
Modeling the Behavior of Heterogeneous Materials with Non Linear Couplings using “Translated Fields”
Authors: Berbenni S. , Favier V. , Berveiller M. 
Published: June 2019

AbstractThe determination of the behavior of heterogeneous materials with complex physical and mechanical couplings constitutes a challenge in the design of new materials and the modeling of their effective properties. In real inhomogeneous materials, the simultaneous presence of elastic mechanisms and non linear inelastic ones (viscoplastic, magnetic, ferroelectric, shape memory effect etc.) leads to a complex non linear coupling between the mechanical fields which is tricky to represent in a simple and efficient way. Hence, for many situations the effective global behavior does not follow the same structure than the local constitutive one. Regarding space-time couplings for instance, a heterogeneous material composed of phases described by Maxwell elements can not be considered as a Maxwellian solid at the macro scale.In this paper, we introduce a new micro-macro approach based on translated fields in its generalized form to be applied to different coupled phenomena. The local total strain (rate) is composed additively of an elastic strain (rate) and an inelastic one which is no more limited to be “stress free” as considered originally by Kröner. An extended (non conventional) self-consistent model is then proposed starting from the integral equation for a translated strain (rate) field and using the projection operators algebra introduced by Kunin. The chosen translated field is the compatible inelastic strain (rate) of the fictitious inelastic heterogeneous medium submitted to a uniform unknown boundary condition. The self-consistency condition amounts to define analytically these boundary conditions so that a relative simple and compact strain (rate) concentration equation is obtained.In order to illustrate the method, the case of a non linear elastic-viscoplastic coupling is developed and applied to different classes of composites and polycrystals.
Finite Element Formulation of a Piezoelectric Continuum and Performance Studies of Laminar PZT-Patch-Modules
Authors: Gall Monika , Thielicke Bärbel , Poizat Christophe , Klinkel Sven 
Published: June 2019

AbstractEfficient application of piezoelectric sensors and actuators requires extensive investigations of their loading limits, failure-behavior and life-span under service conditions. Here the performance of laminar PZT-patch-modules is studied, applying a combined approach of experimental and numerical tests. Four-point bending tests are used to evaluate the sensor performance. Linear electro-mechanical coupling is implemented in an 8-node brick user element of the research finite element code FEAP to develop a flexible FE-tool for piezoelectric problems. Comparative FE-analyses of the bending test are carried out in order to assess the capability of the implemented FEAP user element versus the commercially available FE-code ABAQUS. FE-results show good agreement with the experimental tests, different element types yield slight deviations which are discussed.
Effect of Crosslinking on the Elastic Properties of the Cytoskeleton: A 3D Discrete Modeling Approach
Authors: Dalmas Florent , Mohrdieck Camilla 
Published: June 2019

ABSTRACTIn living eukaryotic cells a crosslinked network of polymer fibers, the cytoskeleton, endows the cells with structural integrity and mechanical stability and flexibility. To understand the mechanisms that are at the base of these functions, it is important to know in what way the microstructure and the mechanical behavior of the cytoskeleton change as a function of the type and the density of crosslinking molecules. To address this issue, we have developed a new modeling approach based on the discretization of polymeric fibers that are modeled as homogeneous straight beams in a constant volume. Crosslinks between adjacent fibers are taken into account by creating additional beams between the fibers if their spacing is smaller than a meaningful upper bound. By varying their geometrical and mechanical properties, the influence of the crosslinks on the shear modulus of the network can be studied systematically. Our simulations predict interesting new scaling behaviors that depend on the degree of crosslinking.
Investigating the Interfacial Interactions Between Organic and Inorganic Phases and Their Influence on the Mechanics of Organic Phase in Natural Bone
Authors: Bhowmik Rahul , Katti Kalpana S , Katti Dinesh R 
Published: June 2019

ABSTRACTBone is a highly ordered nanocomposite system consisting primarily of organic (collagen) and inorganic (hydroxyapatite(HAP)) phases. The nanocrystals of hydroxyapatite (HAP) mineralize at specific locations in bone. The collagen molecule in bone has C and N terminals which are known as C and N telopeptides. We have performed Molecular Dynamics (MD) and Steered MD (SMD) simulations to study the interface between HAP (mineral) and collagen with N-terminal telopeptides. The force field parameters for HAP were taken from our previous study and the force field parameters for collagen with telopeptides were taken from CHARMm force field. We have investigated the detailed conformation of telopeptides interacting with specific surfaces of mineral and the interface between HAP and collagen. The load-deformation behavior of collagen is obtained with SMD simulations. It has been found that the load deformation behavior of collagen is different when in close proximity of and interacting with HAP.
Micromechanical Measurements on Chemomechanical Protein Aggregates
Authors: Schwan Stefan , Fritzsche Markus , Cismak Andreas , Noll Gundula , Prüfer Dirk , Spohn Uwe , Heilmann Andreas 
Published: June 2019

ABSTRACTChemo-mechanical protein aggregates in plants, e.g. the forisomes of legumes, transform the chemical free energy of their reaction with calcium ions into mechanical energy. Light and scanning electron microscopy analyses demonstrated that the spindle-shaped bodies with lengths between 25 and 40 μm consist of fiber bundle units which change their length and diameter during a reversible switching reaction induced by either calcium, barium, strontium ions or by changes of the pH value. For the determination of forces generated during the switching reaction a force measurement in vitro system based on the bending of thin glass fiber was developed. By using this set-up, dynamical forces of forisomes, in the presence of different alkaline ions, in the range up to 180 nN were measured.
Failure Investigation of Polymer Mechanical Micromponents
Authors: Zhao Yi , Zhang Xin 
Published: June 2019

ABSTRACTThis paper reports typical failure modes of polymer microstructures. Polydimethylsiloxane (PDMS) microstructures were fabricated using replication-based methods. The mechanical collapses of these structures were observed using scanning electron microscopy. In this work, we classified the mechanical collapses based on their individual geometries and discussed the mechanism of each failure mode. We also worked on solutions to recover these failed PDMS structures. This work helps to better understand the collapsing mechanism and to facilitate the development of control strategies to enhance the mechanical reliability of polymer microdevices.
Microstructure, Nanostructure and Properties of the Wasp Petiole
Authors: Reed Emily J. , Dunlap Michael R. , Jasinski Jacek , Viney Christopher 
Published: June 2019

ABSTRACTThe wasp petiole (waist) is a self-assembled, multifunctional, hierarchically structured tube, which in some species has a simple, near-cylindrical shape that simplifies mechanical property characterization. We describe studies performed by scanning electron microscopy and transmission electron microscopy that reveal several details about the hierarchical structure of mud dauber wasp petiole, including: the number and thickness of the concentric layers of cuticle comprising the wall; the similarity (and differences) between the wall structure and the structure of multi-layer corrugated cardboard; and the different anisotropies of the dorsal and ventral internal surfaces. We also describe a simple experiment in which a petiole is used as a cantilever to determine its stiffness in bending; the result (1.5 GPa) demonstrates a material efficiency in bending similar to that of GFRP and aluminum.
Poroelastic Indentation Analysis for Hydrated Biological Tissues
Authors: Oyen Michelle L. , Bembey Amanpreet K. , Bushby Andrew J. 
Published: June 2019

ABSTRACTIndentation techniques are employed for the measurement of mechanical properties of a wide range of materials. In particular, techniques focused at small length-scales, such as nanoindentation and AFM indentation, allow for local characterization of material properties in heterogeneous materials including natural tissues and biomimetic materials. Typical elastic analysis for spherical indentation is applicable in the absence of time-dependent deformation, but is inappropriate for materials with time-dependent responses. Recent analyses for the viscoelastic indentation problem, based on elastic-viscoelastic correspondence, have begun to address the issue of time-dependent deformation during an indentation test. The viscoelastic analysis has been shown to fit experimental indentation data well, and has been demonstrated as useful for characterization of viscoelasticity in polymeric materials and in hydrated mineralized tissues. However, a viscoelastic analysis is not necessarily sufficient for multi-phase materials with fluid flow. In the current work, a poroelastic analysis—based on fluid motion through a porous elastic network—is used to examine spherical indentation creep responses of hydrated biological materials. Both analytical and finite element approaches are considered for the poroelastic Hertzian indentation problem. Modeling results are compared with experimental data from nanoindentation of hydrated bone immersed in water and polar solvents (ethanol, methanol, acetone). Baseline (water-immersed) bone responses are characterized using the poroelastic model and numerical results are compared with altered hydration states due to polar solvents.
Biopolymer Polyelectrolyte Complex – Hydroxyapatite Composites for Bone Tissue Engineering
Authors: Verma Devendra , Katti Kalpana S , Mohanty Bedabibhas , Katti Dinesh R 
Published: June 2019

ABSTRACTThe excellent biocompatibility, biofunctionality, and non-antigenic property make chitosan an ideal material for tissue regeneration. In addition to that its hydrophilic surface promotes cell adhesion, proliferation, and differentiation, and evokes a minimal foreign body reaction on implantation. In spite of these favorable properties, the inadequate mechanical strength and loosening of structural integrity under wet conditions, limit its application for bone tissue engineering. To improve the suitability of chitosan for bone tissue engineering, we have biomimetically synthesized composites of chitosan, polygalacturonic acid and hydroxyapatite. Polygalacturonic acid (PgA) is biocompatible, biodegradable and electrostatically complementary to chitosan. The strong interactions between negatively charged carboxylate groups of PgA and positively charged amino groups of chitosan lead to complex formation. This biopolymer complex provides improved mechanical strength and better structural integrity under wet condition. In this study, we have investigated the applicability of chitosan-PgA-hydroxyapatite composites for bone tissue engineering.
Microstructural Behavior and Failure of FCC Crystalline Aggregates
Authors: Rezvanian O. , Zikry M. A. , Rajendran A. M. 
Published: June 2019

AbstractA unified dislocation density-based microstructural representation of f.c.c. crystalline materials, has been developed such that the microstructural behavior can be accurately predicted at different physical scales. This microstructural framework is based on coupling a multiple-slip crystal plasticity formulation to three distinct dislocation densities, which pertain to statistically stored dislocations (SSDs), geometrically necessary dislocations (GNDs), and grain boundary dislocations (GBDs). This interrelated dislocation-density formulation is then used with specialized finite-element modeling techniques to predict the evolving heterogeneous microstructure and the localized phenomena that can contribute to failure initiation as a function of inelastic deformation.
Predicting the Benefits of Adding Ternary Elements to Al-Sc Alloys
Authors: Simonovic Darko , Sluiter Marcel H. F. 
Published: June 2019

AbstractWe seek to explain 1) the effectiveness of substituting Sc with Dy, Er, Y and 2) the loss of properties when Sc is replaced with Yb, Gd and Sm [1]. For a preliminary insight into the stability of structures we utilize the concept of Atomic Environment Type (AET) as pertaining to trialuminides. Electronic density functional total energy calculations at zero temperature are performed to obtain the enthalpy of mixing of quasi-binary Al-Sc-X structures. Estimates of the entropy are used to compute the stability regions of Al3Sc1-αXα L12 phase. We show that Sc is completely miscible with X=Dy, Er, Y and that there is a miscibility gap for X=Yb, Gd and Sm at temperatures near the aging temperature of Al-Sc alloys.