bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accurate modeling of molecular crystal through
dispersion-corrected density functional theory (DFT-D)
method
Authors: Schatschneider Bohdan , Liang Jian-jie 
Published: April 2011

ABSTRACTCrystal structure, pressure response, and polymorph transformation were
investigated for crystalline indole through dispersion-corrected density
functional theory (DFT-D) method. An accurate, nonempirical method (as in
the latest implementations of CASTEP) is used to correct for the general DFT
scheme to include van der Waals interactions important in molecular
crystals. Ambient structural details, including space group symmetry,
density, and fine structural details, such as bicyclic angles, have been
reproduced to within experimental accuracy. Pressure response of the
structure was obtained to isostatic pressure up to 25 GPa, in increments of
1 GPa. Evolution of space group symmetry and the bicyclic angle were mapped
as a function of pressure. A previously unknown phase transformation has
been identified around 14 GPa of isostatic pressure. Total energies of the
phases before and after phase transformation are nearly identical, with a
phase transformation barrier of 0.9 eV. The study opens up the door to
reliable DFT investigations of chemical reactions of crystalline aromatic
systems under high pressure (e.g. formation of amorphous sp3
hybridized phases).
ENERGY STORAGE, RELEASE, AND DISSIPATION IN THE GECKO ADHESION
SYSTEM
Authors: Puthoff Jonathan B. , Prowse Michael , Wilkinson Matt J. , Autumn Kellar 
Published: April 2011

ABSTRACTDifferent types of biological adhesion can be categorized according to the
length scales, structures, and materials involved. The setal adhesion system
of the gekkonid lizards occupies a hierarchy of scales from the toes (~ 1
cm) to the terminal spatular pads on the setal branches (~ 100 nm). This
unique combination of scale and foot-hair morphology allow the animal
robust, controllable, and near-universal adhesion via van der Waals
attraction, but it is also apparent that the mechanical behavior of the
β-keratin plays an important role in an animal’s climbing ability.
Experimental results show a four-fold increase in the viscoelastic loss
tangent of β-keratin, alongside a substantial increase in adhesion of setal
arrays, over a range of relative humidity from 10 to 80%. A model of
single-spatular deformation predicts that the elastic energy stored in the
setal branches, energy which is not completely recovered on detachment, is
strongly influenced by these properties changes. The enhanced dissipation
characteristics of the system explain the effects of environmental humidity
on the clinging ability of geckos.
Characterization of Erythrocytes in the Sickle Cell Trait
Authors: Maciaszek Jamie L. , Lykotrafitis George 
Published: April 2011

ABSTRACTAtomic force microscopy (AFM) allows for high-resolution topography studies of biological cells, measurement of their mechanical properties, and quantification of protein-protein interactions in physiological conditions. In this work, AFM was employed to investigate morphological, material, and chemomechanical properties of red blood cells from human subjects with sickle cell trait. We measured the stiffness of the cells and demonstrated that the Young’s modulus of pathological erythrocytes was three times greater than in normal cells. A single molecule AFM method was employed to report that erythrocytes from human subjects with the sickle cell trait express a greater number of the laminin receptors BCAM/Lu (p < 0.05) than erythrocytes from normal human subjects. Observed differences indicate the effect of sickle hemoglobin in the erythrocyte and possible changes in the organization of the cell cytoskeleton and membrane proteins associated with the sickle cell trait.
Hierarchical computational approaches of the effects of interstitial and vacancy loops on plastic deformation
Authors: Tsuru Tomohito , Aoyagi Yoshiteru , Kaji Yoshiyuki 
Published: April 2011

ABSTRACTHierarchical modeling based on atomistic and continuum simulations were established to describe the fundamental characteristics of plastic deformation in irradiated materials. Typical irradiation defects of a self-interstitial atom (SIA) loop and vacancy loop are considered. At first atomic models, including a SIA loop and a vacancy as well as a straight dislocation loop in single crystals were constructed. Constant strain is applied to each model and the equilibrium configuration under deformation is calculated by a molecular statics simulation. Maximum shear stresses in various radii of irradiated defects are stored in a database for the continuum mechanics analysis. Then local interaction events between glide dislocation and irradiation defects were introduced through crystal plasticity finite element analysis. In this model the effect of radiation hardening was considered by referring to the experiment. We found that softening after the first yield event is caused by annihilation of irradiation defects resulting from unfaulting of the radiation defects.
Characterizing the Role of Deformation during Electrochemical Etching of Metallic Films
Authors: Kumar Anil , Hsu Keng , Jacobs Kyle , Ferreira Placid , Fang Nicholas X. 
Published: April 2011

ABSTRACTElectrochemical dissolution of ionic species into a solid is an area of great interest in several fields including nanoscale patterning and energy storage. Such dissolution is strongly influenced by several factors e.g., work function difference, dislocation density, grain size, and number of grain boundaries. These parameters are strongly influenced by mechanical deformation of the ionic conductor. Here we characterize such a system of silver (Ag) and silver sulfide (Ag2S), where incorporation of Ag into the solid ionic conductor, Ag2S, is dramatically influenced by mechanical deformation. We show more than three-fold dissolution rate enhancement when the polycrystalline conductor is compressed to one-third of its original size. We attribute this enhancement to increased dislocation density which is supported by the high current densities observed during dissolution. Additionally, reduced electronic currents suggest most of this contribution comes from increased reaction at the metal-conductor interface. Our studies have important applications in areas involving ionic transport including direct metal patterning and energy storage technology.
Electrical and Structural Diagnostics of Barium Strontium Titanate (BST) Thin Films
Authors: Ketkar Supriya , Ram Manoj Kumar , Kumar Ashok , Weller Thomas , Hoff Andrew 
Published: April 2011

ABSTRACTThe properties of radio frequency, rf magnetron sputtered Barium Strontium Titanate (Ba1-xSrxTiO3), BST, thin films were investigated and compared with BST thin films deposited by sol-gel method with the aim of determining relationships between the oxide deposition parameters, the film structure, and the electric field dependence. This work presents noncontact electrical characterization of BST films using Corona Kelvin metrology (C-KM) which has been employed earlier only in the silicon industry. The films were structurally characterized using thickness profilometer, X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques. The use of sol-gel technique to fabricate small area metal-insulator-metal (MIM) structures is found to be beneficial from the point of saving fabrication time and production costs.
Influence of Nanoindenter Tip Radius on the Estimation of the Elastic Modulus
Authors: Gadelrab Karim R. , Chiesa Matteo 
Published: April 2011

ABSTRACTNanoindentation results are very sensitive to tip rounding and neglecting the value of the tip radius produces erroneous estimation of the material elastic properties. In this study we investigate the effect of tip radius on the estimation of the Elastic modulus by means of finite element analysis of Berkovich and conical tips with different tip radii. Our numerical results were already supported by an experimental study on fused silica with Berkovich tips with different tip radii. The use of classical Oliver Pharr equation overestimated the Elastic modulus. A new analytical model that modifies the Oliver Pharr equation to consider the value of the tip radius is employed to derive the Elastic modulus from load displacement curves yielding improved results compared to the classical Oliver Pharr equation.
Bottom-up Modeling of the Elastic Properties of Organosilicate Glasses and their Relation to Composition and Network Defects
Authors: Knaup Jan M. , Li Han , Vlassak Joost J. , Kaxiras Efthimios 
Published: April 2011

ABSTRACTOrganosilicate glasses (OSG), also known as SiCOH or carbon-doped oxide are used as low-k inter-metal dielectrics for integrated circuits. The material must fulfill two conflicting requirements: It has to have low density to reduce the dielectric constant and be mechanically stable enough to withstand mechanical stress during subsequent production steps. Experimental advances in improving their mechanical and electrical properties have not yet been theoretically examined at the ab initio level, due to the relatively large model sizes necessary for amorphous materials. We employ the density-functional based tight-binding (DFTB) method to achieve an accurate description of OSG properties at different compositions. We analyze the influence of composition and topological defects on the density and bulk modulus of non-porous OSG. We find that the dependence of density and stiffness on chemical composition is of different nature. This difference is traced to a transition between different mechanisms of elastic deformation in silica glass and in silicon hydrocarbide, which is also the reason for different sensitivity to topological defects in the two materials.
Inception of plasticity in the presence of vacancies in FCC single crystals: indenter size effect
Authors: Salehinia I. , Perez V. , Weber M. , Bahr D.F. 
Published: April 2011

ABSTRACTAtomistic simulations of nanoindentation tests were used to study the indenter radius size effect in the presence of vacancies in a (111) single crystal of nickel. For radii from 2 nm to 8 nm, the maximum shear stresses under the indenter at the onset of plastic deformation in crystals with vacancies were compared to those which cause yield in perfect crystals by placing a single vacancy in a position near the maximum shear stress underneath the indenter tip. The effect of the presence of vacancies is lowered by decreasing the indenter radius. Results obtained for several random distributions of vacancies, in the range 3.3e-4 to 0.0033, show that placing a single vacancy near a specific location produces similar results as using larger numbers of vacancies while simplifying the complexity of the simulation. Finally, visualizations of atomic configurations of a single crystal with vacancy concentration of 3.3e-4 for radii of 4 nm and 6nm show that the heterogeneous nucleation is a size dependent phenomenon.
Nondeterministic Multiscale Modeling of Biomimetic Crack Self-Healing in Nanocrystalline Solids under Mechanical Loading
Authors: Karpov Eduard G. , Grankin Mykhailo 
Published: April 2011

ABSTRACTA nondeterministic multiple scale approach based on numerical solution of the Monte-Carlo master equation coupled with a standard finite-element formulation of material mechanics is presented. The approach is illustrated in application to the long-term evolutionary processes of self-diffusion, precipitation and crack/void healing in nanocrystalline fcc and bcc solids. Effect of static and dynamic loading patterns on the crack healing rates are investigated. The approach is widely applicable to the modeling and characterization of advanced functional materials with evolutionary internal structure, as well as emerging behavior in materials systems.
Micro/Nano Structure and Morphology of Multi-Phase Polymer/Oxide Composites Prepared by Powder Melt Processing
Authors: Giancola Giorgiana , Lehman Richard 
Published: April 2011

ABSTRACTPowder polymer processing techniques were evaluated as a means to generate homogeneous immiscible polymer blends without the high residence times at elevated temperature and high shear rates required by extrusion. Using emulsion polymerized and cryogenically jet pulverized PMMA and HDPE powder precursors, blends were prepared with morphologies comparable to extruded blends. Advanced EDS imaging methods combined with SiO2 marker spheres enhanced electron imaging and analysis of all blend phases. These processing methods will be useful in producing polymer blends from fragile polymers, such as those used in biomedical applications, that cannot tolerate the temperature or shear rates of conventional melt processing.
Effect of Ag Content on Electrical Conductivity and Tensile Properties of Cu-Ti-Ag Alloys
Authors: Jung Taek-Kyun , Joh Dong-Woo , Lee Hyo-Soo , Kwon Hyuk-Chon 
Published: April 2011

ABSTRACTEffects of Ag content on microstructure, mechanical properties, and electrical conductivity in long time aged Cu-Ti-Ag alloys were investigated. In short time ageing condition, both electrical conductivity and mechanical properties were enhanced by Ag addition. On the other hand, in long time ageing condition, Ag addition showed a faster deterioration of mechanical properties than Ag free CuTi alloys.
Electroless Synthesis of 1.4 nm Pd and Pt Nanoparticles on
Self-Assembled Rosette Nanotubes
Authors: Chhabra Rahul , Fenniri Hicham 
Published: April 2011

ABSTRACTElectroless synthesis and hierarchical organization of 1.4 nm Pd and Pt
nanoparticles (NPs) on self-assembled Rosette Nanotubes (RNTs) is described.
The nucleated NPs are nearly monodisperse and reveal supramolecular
organizations guided by RNT templates. Interestingly, the narrow size
distribution is attributable to unique templating behavior of RNTs. The
resulting metal NP-RNT composites were characterized by Atomic Force
Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission
Electron Microscopy (TEM). X-ray Photoelectron Spectroscopy (XPS) was also
performed to confirm the nature and composition of RNT-templated NPs.
Deformation Mechanisms, Microstructure and Mechanical Properties of Nanoscale Crystalline and Noncrystalline Materials in Different Temperature Ranges
Authors: Milman Yuly V. 
Published: April 2011

ABSTRACTA review of the influence of nanoscale structural elements on the mechanical properties of crystals, quasicrystals, and metallic glasses (MG) is presented. Temperature ranges of cold, warm, and hot deformation are distinguished for crystalline materials, but a nanocrystalline (NC) structure may be formed by severe plastic deformation in the temperature ranges of warm and hot deformation. The plasticity characteristic obtained by indentation can be used for the characterization of low-ductile NC materials. The main features of the plastic deformation mechanisms of NC materials, including results obtained by molecular dynamic simulation, are considered.For MG, the following two problems are discussed: the comparison of the yield stresses for NC and MG and the possibility of strengthening of MG by disperse crystalline nanoscale particles.Quasicrystals with nanosize grains, which are also called nanoquasicrystals (NQC), form a separate class of materials. The mechanical properties of NQC and crystalline materials strengthened by NQC particles are analyzed. Dispersion hardening of metals by NC particles was the first application of nanoscale structures for structural materials. New possibilities of such strengthening are considered.
Fluorescence of Two-dimensional Patterned Photosynthetic Proteins onto Gold surface
Authors: Furukawa Rei A. , Yajima Shunsuke , Nozaki Shinji , Dewa Takehisa , Nango Mamoru 
Published: April 2011

ABSTRACTPhotosynthetic membrane proteins convert solar light into chemical energy in a significantly high efficiency. Up-to-date reports of the photosynthetic bacterium suggest that such effective light conversion is due to the energy transfer between two light-harvesting (LH) protein complexes that are patterned in two dimensions. In this report, LH complex isolated fromRb. sphaeroideswas immobilized onto a patterned gold surface with self-assembled monolayers (SAMs) and lipid bilayers at two main objectives: (1) micron-scale patterning of LH complex, and (2) prevention of quenching for pattern observation.
FET-based biosensor incorporating a conductometric
bioreceptor
Authors: Vercik Andrés 
Published: April 2011

ABSTRACTNovel strategies of transduction may help to improve the biosensor
performance by enhancing its sensitivity or linearity or by allowing a
better integration with the electronics, which in turn favors the
miniaturization of the sensing devices. In this work, a combination of a
conductometric element containing the bioreceptor with a MOSFET is proposed
as a transduction strategy. Simulations of the gate voltage and drain
current versus conductance curves are used to confirm the feasibility of the
proposed strategy. One of the advantages of the presented device is that the
sensing element can be deposited by back-end processes compatible with
current IC technology.
Gold Nanoparticle Enlargement Coupled with Fluorescence Decrease
for Highly Sensitive Detection of Analytes
Authors: Lim Seong Yoon , Kim Jae Hong , Lee Joon Seok , Park Chan Beum 
Published: April 2011

ABSTRACTWe present a versatile and facile route for highly sensitive detection of
analytes through coupling the enlargement of gold nanoparticles (Au NPs)
with fluorescence decrease. The fluorescence intensity of dye molecules
(e.g., fluorescein or rhodamine B) significantly decreased with the
increasing concentration of reducing agents, such as hydrogen peroxide and
hydroquinone. The sensitivity for the detection of reducing agents was much
higher than other detection methods based on the absorbance measurement of
enlarged gold nanoparticles or quantum dot-enzyme hybridization. We could
successfully detect acetylthiocholine with the detection limit of several nM
orders, using an enzymatic reaction by acetylcholinesterase, a key route for
the detection of toxic organophosphate compounds. The fluorescence
decreasing approach described in this work requires only a simple addition
of fluorescence dye to the reaction solution without any chemical
modification. The strategy of fluorescence decrease coupled with
nanoparticle growth will be applied on the fluorescent substrate to develop
detection templates for highly sensitive optical biosensor.
Biomolecular material systems with encapsulated interface
bilayers
Authors: Sarles Stephen A. , Leo Donald J. 
Published: April 2011

ABSTRACTIn this paper we present a novel approach for interface bilayer formation in
which the uptake of an aqueous lipid vesicle solution by two polymeric
hydrogels contained in a substrate causes the gels to swell so as to come
into contact within an internal oil-filled region of the device. An
interface bilayer, similar to those formed using the droplet interface
bilayer (DIB) method, forms upon contact in oil between the lipid-encased
ends of the two gels. Experimental measurements provide initial evidence
that gel swelling enables automatic bilayer formation within a few minutes
after the addition of lipid solution. The approach presented herein works
toward the development of a new portable, easy-to-use screening platform
that features tailored interface bilayers for a wide variety of screening
applications.
Characterization on the Viscoelastic Property of PDMS in the
Frequency Domain
Authors: Du Ping , Lin I-Kuan , Lu Hongbing , lin Xi , Zhang Xin 
Published: April 2011

ABSTRACTA key issue in using Polydimethylsiloxane (PDMS) based micropillars as
cellular force transducers is obtaining an accurate characterization of
mechanical properties. The Young’s modulus of PDMS has been extended from a
constant in the ideal elastic case to a time-dependent function in the
viscoelastic case. However, the frequency domain information is of more
practical interest in interpreting the complex cell contraction behavior. In
this paper, we reevaluated the Young’s relaxation modulus in the time domain
by using more robust fitting algorithms than previous reports, and
investigated the storage and loss moduli in the frequency domain using the
Fourier transform technique. With the use of the frequency domain modulus
and the deflection of micropillars in the Fourier series, the force
calculation can be much simplified by converting a convolution in the time
domain to a multiplication in the frequency domain.
Microphase-separated block copolymer film anchored on ITO substrate with newly designed self-assembled monolayer
Authors: Goda Takenori , Hadano Shingo , Iyoda Tomokazu 
Published: April 2011

ABSTRACTThe surface of Indium-tin-oxide (ITO) substrate was modified with a newly designed silane coupling molecule bearing azobenzene moiety. The silane coupling molecules formed self-assembled monolayer (SAM) on pretreated ITO surface. The SAM growth and coverage were quantified by contact angle measurement and X-ray photoelectron spectroscopy (XPS). The silane coupling molecules improved the adhesion between the ITO surface and an amphiphilic block copolymer (BC) thin film, which consists of poly(ethylene oxide) (PEO) and poly(methacrylate) (PMA) with azobenzene mesogens, because the azobenzene moieties of the SAM anchor the liquid crystalline PMA azobenzene domains of BC.
Preparation of PIT-Free Hydrogen-Terminated Si(111) in
Deoxygenated Ammonium Fluoride
Authors: Wade Christopher P. , Chidsey Christopher E. D. 
Published: April 2011

ABSTRACTWe show by ex-situ STM that pit-free H-Si(111) surfaces can
be prepared by immersion of pre-oxidized Si(111) in deoxygenated 40%
NH4F for 15 minutes. In contrast, H-Si(111) prepared in
air-saturated 40% NH4F for 15 minutes results in small etch pits
randomly covering ca. 1% of the surface. Added dioxygen,
shorter etching times or stirring of the air-saturated etch solution
increase the etch pit density. Dissolved oxygen is responsible for the
initiation of etch pits on the (111) monohydride terraces. The reaction
between dissolved oxygen and the H-Si bond of the (111) terrace is limited
by mass transport of dissolved oxygen to the silicon surface. A proposed
reaction mechanism of dissolved oxygen with H-Si is briefly mentioned, which
explains not only etch pit initiation in ammonium fluoride but also the
oxidation of hydrogenterminated silicon in wet, oxygenated environments. The
results presented here for H-Si(111) lead to a greater understanding of the
wet oxidation and etching processes of this important model surface.