bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction Pathway Analysis of Homogeneous Dislocation Nucleation in a Perfect Molybdenum Crystal
Authors: Saeed Hasan A. , Izumi Satoshi , Hara Shotaro , Sakai Shinsuke
Published: April 2011

Reaction pathway analysis was carried out for homogeneous dislocation nucleation in perfect crystal Mo. The reaction sampling method employed was based on the Nudged Elastic Band algorithm and other extended schemes. Results obtained were compared with corresponding results for Cu and Si. The stress range for activation energies less than 5 eV is found to be considerably higher for Mo than those for Cu as well as Si. Stresses in excess of 12 GPa make homogeneous dislocation nucleation in Mo an unrealistic transition. The results also show the dislocation cores under this stress range to be diffused, with shear displacement of particles being considerably less than the Burgers vector. Depending on the applied stress, displacement of extra slip-plane atoms can be considerable in Mo. This is in contrast to Cu, in which dislocation nucleation is essentially a two-plane phenomenon.
Enhanced Electron Field Emission from Carbon Nanotube Matrices
Authors: Pandey Archana , Prasad Abhishek , Yap Yoke Khin , Engelhard Mark , Wang Chongmin
Published: April 2011

Field emission from as-grown carbon nanotube (CNTs) films often suffered from high threshold electric field, and low emission site density due to screening effects. These problems can be resolved by patterned growth of CNTs on lithographically prepared catalyst films. However, these approaches are expensive and not applicable for future emitting devices with large display areas. Here we show that as-grown CNTs films can have low emission threshold field and high emission density without using any lithography processes. We have reduced screening effects and work function of as-grown CNTs films and created the novel CNT matrices by addition of vapor- and/or liquid- phase deposition. Furthermore, these CNT matrices can continuous emit electrons for 40 hours without significant degradation. The fabrication of our CNT matrices is described as follows. First, CNT films were grown by plasma-enhanced chemical vapor deposition. These vertically-aligned multiwalled carbon nanotubes (VA-MWCNTs) are having typical length and diameter of 4 microns and 40 nm, respectively. Spacing between these CNTs is ~80 nm in average, leading to poor emission properties due to the screening effect. These as-grown samples were then subjected to the deposition of strontium titanate (SrTiO3) by pulsed-laser deposition to reduce both the work function and screening effect of CNTs. The emission properties of these coated samples can be further improved by fully filled the spaces between VA-MWCNTs by poly-methyl metha acrylate (PMMA). The field emission threshold electric field was decreased from 4.22 V/μm for as-grown VA-MWCNTs to 1.7 V/μm for SrTiO3 coated VA-MWCNTs. The addition filling with PMMA and mechanical polishing can further reduce the threshold to 0.78V/μm for the so called PMMA-STO-CNT matrices. Long term emission stability and emission site density were also enhanced.
Characterization of Curvature in CNT Turf Structures from Two-Dimensional Images
Authors: Kelley Garrett M. , Field David P.
Published: April 2011

Carbon nanotube turfs are collections of nanotubes in a turf or mat assembly with potential application as thermal switches, flat panel displays, hard drives, sensors, etc. The nano-topology of the turf necessarily relates to the turf properties; electrical, thermal, optical, etc. A simple method to quantitatively characterize the density, tortuosity and path connectedness of the turfs using secondary electron imaging was previously developed. The present work aims at developing the groundwork for a more realistic measure of tortuosity by using a deterministic approach to obtain the radii of semi-circular tubes as observed in projected images.
Grating Coupled Waveguide Biosensor Based on Porous
Silicon
Authors: Wei Xing , Weiss Sharon M.
Published: April 2011

Porous silicon waveguides with integrated porous silicon grating couplers
are demonstrated as small molecule biosensors. Two fabrication methods are
presented for the grating couplers: standard electron beam lithography with
reactive ion etching and a new technique based on direct imprinting of
porous substrates. Although the gratings fabricated using standard
lithographic techniques have steeper sidewalls and enable a larger available
sensing surface area inside the waveguide, the imprinted gratings have the
advantage of rapid and low-cost fabrication. Both the lithographically and
imprinted sensors are shown to have waveguide losses on the order of 10
dB/cm, and both are demonstrated for detection of 16mer nucleic acids.
Assessment of the Phase Equilibria among γ-Fe/ Fe2Nb/ Ni3Nb Phases in Fe-Ni-Nb Ternary System at Elevated Temperatures
Authors: Hasebe Y. , Hashimoto K. , Matsuo T. , Takeyama M.
Published: April 2011

Phase equilibria among γ-Fe, ε-Fe2Nb Laves and δ-Ni3Nb phases in Fe-Ni-Nb ternary system at 1473 K and 1373 K were experimentally examined, and also assessed by calculation in order to calculate the phase equilibria among these phases at 973 K. A ternary compound with hP24 structure with its limited composition range of Fe-21.5Nb- (56.8-59.8) Ni exists between Fe2Nb and Ni3Nb phase regions at both temperatures. Including the hP24 phase, the calculated isotherms at both temperatures are in good agreement with experimental ones. By using the optimized interaction parameters among the three elements in each phase, the isothermal section calculated at 973 K revealed a γ-Fe+ Fe2Nb + Ni3Nb three-phase coexisting region extended to Fe-rich composition of 80 at. % Fe. This suggests a possibility to develop austenitic heatresistant steels strengthened by both intermetallics phases.
Novel Concept of Creep Strengthening Mechanism using Grain Boundary Fe2Nb Laves Phase in Austenitic Heat Resistant Steel
Authors: Tarigan Imanuel , Kurata Keiichi , Takata Naoki , Matsuo Takashi , Takeyama Masao
Published: April 2011

The creep behavior of a new type of austenitic heat-resistant steel Fe-20Cr-30Ni-2Nb (at.%), strengthened by intermetallic Fe2Nb Laves phase, has been examined. Particular attention has been given to the role of grain boundary Laves phase in the strengthening mechanism during long-term creep. The creep resistance increases with increasing area fraction (ρ) of grain boundary Laves phase according to equation ε/ε = (1−ρ), where ε0 is the creep rate at ρ = 0. In addition, the creep rupture life is also extended with increasing ρ without ductility loss, which can yield up to 77% of elongation even at ρ = 89%. Microstructure analysis revealed local deformation and well-developed subgrains formation near the grain boundary free from precipitates, while dislocation pile-ups were observed near the grain boundary Laves phase. Thus, the grain boundary Laves phase is effective in suppressing the local deformation by preventing dislocation motion, and thereby increases the long-term creep rupture strength. This novel creep strengthening mechanism was proposed as “grain boundary precipitation strengthening mechanism” (GBPS).
Evaluation of adhesive strength between vanadium alloys and yttrium oxide by laser shock spallation method
Authors: Satou M. , Akamatsu H. , Nagasaka T. , Hasegawa A.
Published: April 2011

Adhesive strength between V-4Cr-4Ti type alloys and an yttrium oxide layer formed by a plasma spray technique was evaluated by a laser shock spallation method, which uses a pulse laser to generate a shock wave to create tensile stress inside the specimen. There was no significant dependence of the adhesive strength on the alloying elements examined, such as yttrium, silicon and aluminum. Detailed observation of the exfoliation behavior was carried out to identify the weakest interface of the coating layer. Several modes of exfoliation behavior were categorized after cross-sectional observation. There was some uncertainty of the adhesive strength of the layer evaluated by the laser shock method, due to the thickness of the coating layer. The typical adhesive strength between the alloy and yttrium oxide layer was evaluated to be approximately 400 MPa.
Failure mode transition in natural mineralized
composites
Authors: Rabiei Reza , Bekah Sacheen , Barthelat Francois
Published: April 2011

Mineralized biological materials such as nacre and bone achieve remarkable
combinations of stiffness and toughness through staggered arrangements of
stiff components bonded by softer materials. These natural composites are
therefore substantial source of inspiration for emerging synthetic
materials. In order to gain new insights into structureperformance
relationships of these staggered structures, nacres from four species were
compared in terms of fracture toughness and damage propagation pattern.
Fracture tests revealed that all nacres display rising crack resistance
curves, but to different extents. Using in-situ optical and atomic force
microscopy, two distinct patterns of damage propagation were identified in
columnar and sheet nacre respectively. These two different patterns were
further confirmed by means of large scale numerical models of staggered
structures. Similar mechanisms possibly operate at the smallest scales of
the microstructure of bone.
Simulation of the Mechanical Behavior of White Matter Using a
Micromechanics Finite Element Method
Authors: Pan Yi , Pelegri Assimina A. , Shreiber David I.
Published: April 2011

The atypical mechanical behavior of white matter and its influence on the
mechanical properties of brain tissue necessitate adoption of a mutli-scale
model of white matter for accurate computational analysis. Herein, we
present a micromechanical analysis coupled with finite elements into a
biomechanical interacting model of white matter. A representation of the
white matter of central nervous system is identified and its microstructure
is generated. The geometric descriptions of the axon and the surrounding
matrix are obtained from neurofilament immunohistochemistry images.
Consecutively, linear elastic material constitutive models are applied to
describe the behavior of axons and their surrounding matrix subjected to
small deformations. This model facilitates determination of the tissue’s
stress and strain fields, and enables an understanding of the effects of
axon undulation on local fields. The fundamental nature of the model enables
future scale-up for structural tissue analysis and predictions of axon
damage at the microscale.
Mg-Ti: A Possible Biodegradable, Biocompatible, Mechanically Matched Material for Temporary Implants
Authors: Hoffmann Ilona , Cheng Yang-Tse , Puleo David A. , Song Guangling , Waldo Richard A.
Published: April 2011

In recent years there has been a renewed interest in magnesium alloys for applications as temporary biomedical implants because magnesium is both biocompatible and biodegradable. However, the rapid corrosion rate of magnesium in physiological environments has prevented its successful use for temporary implants. Since alloying is one of the routes to slow down corrosion, we report in this publication our investigation of Mg-Ti alloys fabricated by high-energy ball milling as possible materials for biocompatible and biodegradable implants. Titanium was chosen mainly because of its proven biocompatibility and corrosion resistance. Corrosion tests carried out by immersing the Mg-Ti alloys in Hank’s Solution at 37°C showed significantly improved corrosion resistance of the alloy in comparison to pure magnesium. Thus, Mg-Ti alloys are promising new biodegradable and biocompatible materials for temporary implants.
Simulations of Stretching Single Stranded DNA
Authors: Singh Abhishek , Yingling Yaroslava G.
Published: April 2011

Molecular dynamics simulations were performed to estimate sequence dependent
force required to stretch single stranded DNA (ssDNA) homo oligonucleotides.
Simulations suggest that polyA and polyC oligonucleotides exhibit similar
force profiles and corresponding elongation. Among single stranded DNA
strands polyT is the most flexible and needs the most force to unwind from
an equilibrium folded structure. In contrast, polyG had a very small
recoverable deformation prior to a non-linear stretching. Our results
indicate that mechanical properties of ssDNA chains are directly related to
their sequence.
A Macroscale Biomimetic Composite Duplicating the Deformation
Mechanisms of Nacre
Authors: Zhu Deju , Barthelat Francois
Published: April 2011

This article presents the first man-made material based on the structure of
nacre that successfully duplicates the mechanism of tablet sliding. This
material was made of millimeter size PMMA tablets arranged in columns and
held by fasteners. Strain hardening was provided by tablet waviness,
delaying localization and leading to strains at failure 3-5 times greater
than bulk PMMA. Analytical and finite element models successfully captured
the locking mechanisms, enabling a rigorous design and optimization of
similar composites based on different materials or at different length
scales. This work demonstrates how key features and mechanisms in natural
nacre can be successfully harnessed in engineering materials. Interestingly,
the development of this model material and of its associated models also
unveiled two new mechanisms, the effect of free surfaces and “unzipping”.
Both mechanisms may be relevant to natural materials such as nacre or
bone.
Quantifying Micro-mechanical Properties of Soft Biological
Tissues with Scanning Acoustic Microscopy
Authors: Zhao Xuegen , Wilkinson Steven , Akhtar Riaz , Sherratt Michael J , Watson Rachel E B , Derby Brian
Published: April 2011

In this study we have established a new approach to more accurately map
acoustic wave speed (which is a measure of stiffness) within soft biological
tissues at micrometer length scales using scanning acoustic microscopy. By
using thin (5 μm thick) histological sections of human skin and porcine
cartilage, this method exploits the phase information preserved in the
interference between acoustic waves reflected from the substrate surface as
well as internal reflections from the acoustic lens. A stack of images were
taken with the focus point of acoustic lens positioned at or above the
substrate surface, and processed pixel by pixel using custom software
developed with LABVIEW and IMAQ (National Instruments) to extract phase
information. Scanning parameters, such as acoustic wave frequency and gate
position were optimized to get reasonable phase and lateral resolution. The
contribution from substrate inclination or uneven scanning surface was
removed prior to further processing. The wave attenuation was also obtained
from these images.
Atomic Force Microscopic Study of Morphological Changes for
Treated and Untreated Collagen Fibers of Mongolian Goatskins
Authors: Ankhbayar Enkhbaatar , Itgel Byamba , Batkhuu Byambadembrel , Urnaa Dashnyam , Ganzorig Chimed
Published: April 2011

In this study, the morphological changes of chemically treated (or
preserved) with aqueous solutions of 1) a sodium chloride (NaCl) and 2) a
compound containing sodium silicate, so called “wasserglass”, and untreated
I-type collagen fibers of Mongolian goatskin are investigated by atomic
force microscopy in ambient condition and at room temperature. The
experimental results show that the difference between D period for both
chemically treated and untreated collagen fibers are a relatively stable for
morphological behavior. However, we find that the width of collagen fibers
treated with the NaCl solution is more increasing with approximately 112 nm
than those of samples (untreated and treated with wasserglass solution) for
the range 93.4-94.8 nm. We also observe that a typically structure of the
collagen fibers generally, a dense packing of the untreated and treated by
wasserglass collagen fibers in bundles in a nearly parallel arrangement,
with little changes in orientation can be seen. The collagen fibers treated
by NaCl are a more destructive than untreated and treated by wasserglass for
collagen fibers.
Glucose Oxidase-Functionalized Nanodiamond Films for Biosensor Application
Authors: Villalba Pedro , Ram Manoj K. , Gomez Humberto , Kumar Amrita , Bhethanabotla Venkat , Kumar Ashok
Published: April 2011

The importance of nanodiamond in biological and technological applications has been recognized, and applied in drug delivery, biochip, sensors and biosensors. Nanodiamond (ND) and nitrogen doped nanodiamond (NND) films were deposited on n-type silicon films, and later functionalized with enzyme glucose oxidase (GOX). Functionalized electrode has been characterized using different techniques; i.e.fourier transform spectroscopy (FTIR) -, Raman spectroscopy, atomic force microscopy (AFM) and electrochemical techniques, respectively. Under this work, the ND/GOX and NND/GOX electrodes have demonstrated providing sensitive glucose concentration response. Besides, the cytotoxic effects of the NDs have been studied in vitro. Human Embryonic Kidney 293 (HEK293) cells are cultured in the presence of the films then toxicity has been detected using MTT-based cytotoxicity assays utilizing 3-(4, 5-Dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT). The final results for MTT assays are quantified by spectrophotometry using a plate reader at 570 nm As-prepared nanodiamond has been found to be stable , biocompatible and useful for biosensing applications. A linear response of the enzyme based electrode to glucose concentration is also observed from 1-8 x mM before saturation condition close to 10mM has been observed.
Electrical Conducting Diamond Thin-Films: An Alternative Counter Electrode Material for Dye Sensitized Solar Cells
Authors: Vispute R.D. , Vats Alok , Venkatesan Vinod , Seiser Andrew , Dozier Jaurette , Feldman Jeremy , Robinson Lance
Published: April 2011

Carbon is a favorable alternative as counter electrode material for dye sensitized solar cells (DSSC) as compared to Pt. Various carbon materials such as carbon nanotubes (CNT), activated carbon (AC) and carbon nanofibers have been investigated as counter electrodes for DSSC applications, based on their high electrochemical activity, high specific surface area, chemical inertness and high electrical conductivity. Among various phases of carbon, diamond is the most robust and chemical inert material that can be used for electrode application. It has band gap of 5.5 eV, high thermal conductivity. its electrical resistivity can be tuned by doping such as boron. In this work, we investigate boron doped diamond thin film electrode for DSSCs. The conductive diamond thin electrode films were grown using Blue Wave hot wire chemical vapor deposition (HWCVD) system. The electrical resistance in diamond thin films was tuned by controlling grow temperature, filament power, dopant concentration and sp3/sp2 ratio in the film, it thickness, and initial seeding process. Scanning electron microscopy, Raman spectroscopy and electrical resistivity measurement were used to characterize morphology, diamond quality and electrode conductivity, respectively. Diamond film electrodes with optimized surface morphology and electrical characteristics were used for DSSC fabrication. We used nanocrystalline TiO2 paste (P25 Degussa) with average particle size of 25nm as an active layer, the electrolyte comprised of a LiI/I2 electrolyte in acetonitrile (CH3CN), a Ru based metal complex dye [cis-diisothiocyanato-bis(2,2’-bipyridyl-4,4’-dicarboxylato) ruthenium(II) bis(tetrabutylammonium)] OR N719 was used as sensitizer. The photovoltaic performance was determined using J-V characteristics under standard illumination conditions and was compared to a reference DSSC with Pt counter electrode. Results are discussed in the context of diamond electrical and durability and chemical stability of diamond films against most commonly used family of iodine based electrolytes.
CVD-Grown Graphene Solution-gated Field Effect Transistors for pH Sensing
Authors: Giacchetti Benjamin Mailly , Hsu Allen , Wang Han , Kim Ki Kang , Kong Jing , Palacios Tomas
Published: April 2011

This paper presents the fabrication technology and initial characterization of electrolyte-gated field effect transistor (FET) arrays based on CVD grown graphene on copper. We show that the graphene FET (GFET), when immersed in electrolytes, exhibit a transconductance around 5 mS/mm. From preliminary pH sensing experiments, a pH sensitivity of 24 mV/pH has been demonstrated.
Developments of Extra-High Purity Stainless Steels for Nuclear Corrosive Environments
Authors: Nakayama Junpei , Kiuchi Kiyoshi
Published: April 2011

The austenitic stainless steels so-called, the EHP steels with the extra high purity, are developed for improving the reliability of nuclear equipments materials used in the heavily corrosive irradiation environments. By considering the impurities segregation mechanism, the major impurities included in the EHP steels is controlled less than 100ppm by the new melting technology. It is two-step refining process composed of CCIM and EB for effectively removing both non-volatile and volatile harmful elements. The risk to cracking on melting and welding processes is also effectively minimized by enhancing both the eutectic point and the metallic bonding at grain-boundaries. In the EHP steels, it is possible to select the appropriate composition of Ni and Cr for stabilizing austenitic phase and enhancing corrosion resistance. The characteristics of the welding joints are as good as those of the base metal because the same filler metal is sed without the formation of residual delta ferrite. The resistance to IGC and SCC of the EHP steels is markedly improved by minimizing the refining effects, except for type 316 steels with Mo. The welding technique and the chemical composition range are selected for standardizing the EHP.
NanoLAB Triboprobe: Characterizing Dynamic Wear, Friction and Fatigue at the Nanoscale
Authors: Lockwood A J , Wedekind J , Gay R S , Wang J J , Bobji M S , Amavasai B , Howarth M , Möbus G , Inkson B J
Published: April 2011

In-situ transmission electron microscopy (TEM) has developed rapidly over the last decade. In particular, with the inclusion of scanning probes in TEM holders, allows both mechanical and electrical testing to be performed whilst simultaneously imaging the microstructure at high resolution. In-situ TEM nanoindentation and tensile experiments require only an axial displacement perpendicular to the test surface. However, here, through the development of a novel in-situ TEM triboprobe, other surface characterisation experiments are now possible, with the introduction of a fully programmable 3D positioning system.

Programmable lateral displacement control allows scratch tests to be performed at high resolution with simultaneous imaging of the changing microstructure. With the addition of repeated cyclic movements, both nanoscale fatigue and friction experiments can also now be performed. We demonstrate a range of movement profiles for a variety of applications, in particular, lateral sliding wear.

The developed NanoLAB TEM triboprobe also includes a new closed loop vision control system for intuitive control during positioning and alignment. It includes an automated online calibration to ensure that the fine piezotube is controlled accurately throughout any type of test. Both the 3D programmability and the closed loop vision feedback system are demonstrated here.
Atomistic study of the mechanical stability of multi-layered graphene nanobridges
Authors: Nakajima T. , Shintani K.
Published: April 2011

The stability of elongated single- and multi-layered graphene nanoribbons (GNRs) are investigated by molecular-dynamics simulation. In order that GNRs are to be modeled as nanobridges connecting two terminals of electronic devices, the short edges of the GNRs are constrained. The distances between the two constrained edges are gradually increased, and the GNRs are uniaxially strained. The energies and out-of-plane deformations of such uniaxially strained GNRs are examined. The energies of multi-layered GNRs will be lower than those of isolated GNRs because the surface areas of multi-layered GNRs are smaller than the total area of the isolated GNRs. Understanding the relationship between the out-of-plane deformations and strain will lead to the control of the ripple structures of GNRs.
Current Density Dependence of Transient Electroluminescence in
Phosphorescent Organic Light-Emitting Diodes
Authors: Kajii Hirotake , Takahota Noriyoshi , Wang Yadong , Ohmori Yutaka
Published: April 2011

The transient electroluminescence (EL) of phosphorescent organic
light-emitting diodes (OLEDs) was investigated. The behaviors of the
transient characteristics are analyzed using the triplet-triplet
annihilation model. The device exhibited a gradual decrease in quantum
current efficiency owing to the triplet-triplet annihilation at a high
current density. At a higher current density, the reduced rise and decay
times are due to high-density triplet excitons related to the enhanced
triplet-triplet annihilation and the increase of the nonradiative process.
The modulation speed of the devices is mainly limited by the phosphorescent
recombination lifetime.
Incubation Time Free CVD-TiO2 Film Preparation Using Novel Precursor of Ti-DOT
Authors: Chiba Hirokazu , Tada Ken-ichi , Yamamoto Toshiki , Iwanaga Kohei , Maniwa Atsushi , Yotsuya Tadahiro , Oshima Noriaki , Funakubo Hiroshi
Published: April 2011

Titanium oxide thin films were deposited at 250 – 400 °C on amorphous SiO2 prepared on n-type Si substrates by chemical vapor deposition (CVD) using a novel precursor, ethene-1,2-diylbis(tert-butylaminido)diisopropoxotitanium [Ti[N(tBu)C=CN(tBu)](OiPr)2 , Ti-DOT], with oxygen gas as an oxidant. Deposition characteristics of thin films were compared with those using titanium tetraisopropoxide [Ti(OiPr)4, TTIP]. As a result, the deposition amount of TiO2 thin films using Ti-DOT was larger than that of TTIP because of the shorter incubation time in the case of Ti-DOT. Smaller surface roughness was observed for the films using Ti-DOT. In addition, a good conformability was obtained on amorphous SiO2 hole prepared on n-type Si substrate substrate with aspect ratio of 5.
Correlation between Adhesion Strength and Thin film/Substrate Mechanical Properties using the Nano-Scratch Technique
Authors: Zhou Bo , Randall Nicholas , Prorok Barton
Published: April 2011

Scratch testing, as a mature technique for coating adhesion quantification, has been widely adopted by both industrial and academic fields in recent years. Following the urgent needs of very small materials characterization, nano-scratch testing has gradually replaced the traditional pull-off test for the study of ultra-thin film properties. In this research, the relationship between the adhesion strength and film/substrate mechanical properties was investigated to provide fundamental but crucial knowledge of the scratch mechanism. Scratch tests were performed on different film/substrate combinations using a Nano Scratch Tester with a sphero-conical diamond indenter. A progressive load mode was employed to cause coating failure during scratch on the film surface. The critical values of different failure mechanisms, such as cracking and delamination were accurately determined according to the scratch panorama image, penetration and residual depth data. In addition, the hardness (H) and modulus (E) values of the thin films and substrates were measured with an Ultra Nanoindentation Tester. The scratch critical failure loads were then plotted versus film/substrate H and E ratios. A unique relationship was found between these parameters that could help understand the true mechanism behind scratch adhesion and leverage this methodology to a new theoretical level.
Synthetic control over the structure and symmetry of carbon nanotubes: Towards biomedical applications
Authors: Lowry Michael S. , Rayms-Keller Alfredo , Long Karen J. , Santiago Francisco , Gehman Victor H. , Boulais Kevin A.
Published: April 2011

Carbon nanotubes (CNTs) are appealing materials for biomedical applications due to their unique chemical, electrical and mechanical properties. The emphasis of the present work is on controlling the structure and symmetry of carbon nanotubes by imposing an applied stress at the CNT growth site. CNTs were grown under these conditions using standard chemical vapor deposition (CVD) techniques and were subsequently characterized with a scanning electron microscope; the methodology and implications of this approach are discussed herein.
Nanoscale deformation of MEMS materials
Authors: Lockwood A J , Padmanabhan A , Bunyan R J T , Inkson B J
Published: April 2011

Using a novel in-situ TEM triboprobe holder, nanoscale structures formed from polysilicon MEMS materials have been loaded to characterise the failure mechanisms of reduced scale components. Nanobridges with cross-section dimensions much less than 1μm have been deformed using both single, high displacement indentation and low displacement cyclic fatigue. In both deformation modes, significant residual plastic deformation is measured, occurring and accumulating in the polysilicon. This can be seen as a gradual curvature along the entire crossbeam upon unloading. Where the radius of curvature is very high, fracture of the beams at the centre point was generally also seen. When loading at much lower displacement but under fatigue conditions, localised heating around the moving contact point initiates carbon migration, forming a very strong bond. A high tensile force was needed to severe the contact during unload. Such in-situ techniques demonstrate a range of time dependant failure modes which can be overlooked using post-mortem analysis. In particular, the combined effect of localised frictional heating and contamination on the reliability of components that repeatedly comes into contact with one another.
Pressure-Induced Nano-Crystallization of Y2O3
Authors: Deutsch Stuart , Al-Sharab Jafar F. , Kear Bernard H. , Tse Stephen D.
Published: April 2011

A reversible-phase transformation process to convert coarse-grained polycrystalline cubic-Y2O3 directly into the nanocrystalline state is being developed. The process involves a forward cubic-to-monoclinic phase transition under high pressure and a backward transformation from monoclinic-to-cubic under a lower pressure. The process has been used to reduce the grain size of fully dense cubic-Y2O3 from 300 μm to 0.1 μm. A surface modification effect, comprising a columnar-grained structure, has also been observed. Preliminary work indicates that the surface structure is modified, apparently formed by interaction between the graphite heater and sample.
Mechanical Behavior on Micro-compression Test in Ultra-low Carbon Steel Produced by High Pressure Torsion
Authors: Nagoshi Takashi , Shibata Akinobu , Sone Masato , Todaka Yoshikazu
Published: April 2011

Mechanical behavior of ultra-fine grained (UFG) steel fabricated by high pressure torsion (HPT) was investigated by micro-sized compression test of a micro-sized pillar with uniform dimensions (non-tapered, non-filleted) carefully fabricated by FIB milling. After HPT process, grains were elongated to shear direction and its grain size was decreased down to 300 nm in diameter with increasing strain amount. Compression test confirmed that the uniform elongations of ultra-fine grained materials were lower than 3% and do not depend on the grain size.
Profiling of the Mechanical Properties of Ultralow-k Films Using Nanoindentation Techniques
Authors: Geisler Holm , Mayer Ulrich , Lehr Matthias U. , Hofmann Petra , Engelmann Hans-Juergen
Published: April 2011

Several nanoindentation techniques were applied to the surface, the reverse side and cross-sections of PECVD ultralow-k (ULK) film stacks to characterize their elasto-plastic properties quantitatively. Results showed good agreement of the reduced modulus (Er) values measured from above and on cross-sections, respectively. Er decreased by 10-22% from the upper to the lower surface of the films. This gradient suggests that UV light absorption inside the film leads to slightly reduced curing at the rear side of the films compared to the surface of the ULK layers. Both quasi-static nanoindentation and dynamic mechanical mapping showed this trend. It is demonstrated that quantitative mechanical mapping can be performed with a lateral resolution ≤ 100nm. Slight local variations of Er were detected on ULK/SiCxNy films stacked on top of Cu-low-k interconnect structures.
Nanometer Scale Mechanical Behavior of Grain Boundaries
Authors: Wang Chien-Kai , Chew Huck Beng , Kim Kyung-Suk
Published: April 2011

A nonlinear field projection method has been developed to study nanometer scale mechanical properties of grain boundaries in nanocrystalline FCC metals. The nonlinear field projection is based on the principle of virtual work, for virtual variations of atomic positions in equilibrium through nonlocal interatomic interactions such as EAM potential interaction, to get field-projected subatomic-resolution traction distributions on various grain boundaries. The analyses show that the field projected traction produces periodic concentrated compression sites on the grain boundary, which act as crack trapping or dislocation nucleation sites. The field projection was also used to assess the nanometer scale failure processes of Cu Σ5 grain boundaries doped with Pb. It was revealed that the Pb dopants prevented the emission of dislocations by grain boundary slip and embrittles the grain boundary.
Sharp Silicon Nano-Needles Based on Boron Etch-Stop in TMAH
Solutions
Authors: Yan Sheping , Xu Yang , Yang Junyi , Wang Huiquan , Jin Zhonghe , Wang Yuelin
Published: April 2011

Operations on biological living cells and molecular devices have driven
research towards implementation of high-aspect-ratio nano-needles. However,
current nano-needle fabrication is complicated to control the sizes and
angles. In this work, we develop a simple method to fabricate repeatable and
integrated circuit (IC)-compatible sharp silicon nano-needles based on boron
etch-stop in tetramethyl ammonium hydroxide (TMAH) solutions, and the needle
angles can be accurately controlled. An analytical model is proposed to
efficiently predict the needle sizes and explain the etching evolution of
silicon nano-needles.
Dual Detection Platform with Refractive Index and SERS Sensing
Based on Colloidal Gold Functionalized Porous Silicon
Substrates
Authors: Jiao Yang , Koktysh Dmitry S. , Weiss Sharon M.
Published: April 2011

We demonstrate a dual-mode sensing platform based on porous silicon (PSi)
substrates coated with colloidal gold (Au) nanoparticles (NPs). This Au-PSi
composite structure supports both molecular fingerprinting via surface
enhanced Raman scattering (SERS) and quantification of molecular binding via
reflectance measurements. Reflectance shifts of 7-10 nm in the infrared
region were observed in the case of adsorbing benzenethiol or antioxidant
glutathione molecules on the surface of Au NPs. Subsequent SERS measurements
showed unique identification for both molecules and provided a < 1 μM and
< 1 mM detection resolution for benzenethiol and glutathione,
respectively.
Characterization of immobilized DNA on sulfur-passivated InAs
surfaces
Authors: Cho EunKyung , Wu Pae , Ahmed Minhaz , Brown April , Kuech T. F.
Published: April 2011

The immobilization of DNA on passivated n-type InAs (100) surfaces has been
studied using X-ray and ultraviolet photoelectron spectroscopy. The benefits
of sulfur passivation using ammonium sulfide solution
((NH4)2S) for DNA immobilization were examined. The
XPS/UPS data carried out on non-functionalized and functionalized surfaces
demonstrate that the DNA probes reacted with the sulfur-passivated InAs
surface. The XPS data in combination with fluorescently-tagged DNA indicate
that the sulfur passivation process leads to a higher and more uniform
attachment of DNA over the surface compared to non-sulfur-passivated InAs
surfaces. The XPS data obtained immediately after sulfur passivation clearly
observes In-S bonding, with little or no As-S. In addition, the XPS spectra
of As 3d core-levels immediately after sulfur passivation shows that there
is a negligible amount of As-Ox, but the peak become considerable
after exposure to the aqueous DNA probe solution. The increase in
As-Ox is likely due to the presence of non-sulfur bonded As
atoms present on the surface. The presence of sulfur on the surface does
lead to the high areal density of attached ssDNA. This system forms the
basis of a DNA sensing system. While chemically passivating the surface
against oxidation and facilitating probe attachment, the changes in Fermi
level position were also monitored by UPS. UPS spectra show that the Fermi
level of a clean InAs surface is located ~0.6 eV above the valence band
maximum. The changes in electronic states induced by sulfur passivation and
the pinning of EF are discussed.
Chemically Functionalized Carbon Nanotube Label for
Immunoassay
Authors: Abera Adeyabeba , Choi Jin-Woo
Published: April 2011

A recent approach in disease diagnosis and viral epidemics is aimed at
point-of-care tests that could be administered near the patient rather than
time-consuming processes involving centralized laboratories. Point-of-care
devices provide rapid results in simple and low-cost manner requiring only
small sample volumes. These devices will strongly benefit from advanced
materials and fabrication methods to improve their efficiency and
sensitivity. We report a functionalized carbon nanotube label for an
immunosensor application. Carbon nanotube label was prepared by modifying
the carbon nanotube surface to anchor biomolecules. First, the carboxylic
acid treated multi-walled carbon nanotubes (MWCNTs) were uniformly dispersed
with polyvinylpyrrolidone (PVP) by sonication in aqueous solution. PVP
partially wraps around the carbon nanotubes and exposes the surface of the
nanotubes for further functionalization. The MWCNTs were then conjugated
with human immunoglobulin G (IgG) using EDC/Sulfo-NHS coupling chemistry,
where the antibodies occupied sites not covered by PVP. The dispersion,
surfactant modification, and antibody conjugation of the MWCNTs were also
confirmed using SEM and TEM images. The successful functionalization of the
MWCNTs and reactivity of the covalent attached antibodies were demonstrated
for specific antigen binding on the microelectrode device. The carbon
nanotube-based detection mechanism could be tailored for screening various
analyte specific molecules. Furthermore, the reported technique could easily
be integrated in various microfluidic and lab-on-a-chip devices for the
development of functional electronic sensors providing quantitative,
sensitive, and low-cost detection in pointof- care setup.
Label-Free, Electrical Biomarker Detection Based on Nanowire Biosensors Utilizing Antibody Mimics as Capture Probes
Authors: Chang Hsiao-Kang , Ishikawa Fumiaki , Zhou Chongwu
Published: April 2011

Antibody mimic proteins (AMPs) are poly-peptides that bind to their target analytes with high affinity and specificity, just like conventional antibodies, but are much smaller in size (2-5 nm, less than 10kDa). In this report, we describe the first application of AMP in the field of nanobiosensors. In2O3 nanowire based biosensors have been configured with an AMP (Fibronectin, Fn) to detect nucleocapsid (N) protein, a biomarker for severe acute respiratory syndrome (SARS). Using these devices, N protein was detected at sub-nanomolar concentration in the presence of 44 μM bovine serum albumin as a background. Furthermore, negative control experiment is carried out to confirm the role of AMPs in N protein detection.
Morphological evolution of large-scale vertically aligned ZnO nanowires and their photoluminescence properties by hydrogen plasma treatment
Authors: Zhong Miao , Li Yanbo , Paulsen Alexander , Tokizono Takero , Yamada Ichiro , Delaunay Jean-Jacques
Published: April 2011

In this report, large-scale vertically aligned ZnO nanowires, with diameter around 75 nm and length around 2-5 μm, were synthesized on a-plane sapphire by a single step chemical vapor deposition method. The XRD pattern of the as-prepared sample showed a strong ZnO (0002) peak and a weak ZnO (0004) peak that indicate good orientation and high crystal quality of the ZnO nanowires. The sample was then treated by hydrogen plasma, without exhibiting obvious structural damage to the nanowires. The photoluminescence spectra of as-prepared and H2-plasma-treated samples were then examined. A strong green emission peak (centered at 520 nm) was observed in the PL spectrum of as-prepared sample. In sharp contrast, a significant increase of the near-band edge emission (centered at 380 nm) and a strong decrease of the green emission (centered at 520 nm) were found in the PL spectrum of H2-plasma-treated sample. We propose that an efficient passivation of oxygen vacancies by H atoms will cause a drastic decrease of the green emission. More important, it would lead to a significant reduction of surface depletion layer, leading to a great enlargement of total effect area for UV emission. Meanwhile, the significant enhancement of the intensity of UV emission might also attribute to the combined effects of structure-induced waveguide behavior and UV amplified spontaneous emission. It is expected that the enhanced UV emission of vertically aligned ZnO nanowires can be used to improve the performance of UV light emitting devices.
A Resistless Process for the Production of Patterned, Vertically Aligned ZnO Nanowires.
Authors: Ladanov Mikhail , Elineni Kranthi Kumar , Ram Manoj , Gallant Nathan D. , Kumar Ashok , Matthews Garrett
Published: April 2011

ZnO nanostructures have attracted a great deal of interest because of their biocompatibility and outstanding optical and piezoelectric properties. Their uses are widely varying, including as the active element in sensors, solar cells, and nanogenerators. One of the major complications in device development is how to grow ZnO nanowires in well aligned and patterned films with predefined geometrical shape and aspect ratio. Controlled growth is required to achieve the optimal density of nanowires and to produce a defined geometric structure for incorporation in the device. In this work, we have presented a method by which vertically aligned ZnO nanowires could be grown in defined patterns on surfaces without the use of resists. We used a hydrothermal method to grow ZnO nanowires on a substrate through growth modifiers that was pre-patterned with a seeding solution by means of microcontact printing. This method produced vertically aligned ZnO nanowires of predefined size and shape with pattern resolution high enough for the production of rows of single nanowires. The nanowires were characterized by using scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) techniques.
Novel Er-doped organic complexes for application in 1.5 μm
emitting solution-processed organic light emitting diodes
(OLEDs)
Authors: Coya Carmen , Álvarez Angel Luis , Martín Gil Jesús , Martín María , Martín Ramos Pablo , Zaldo Carlos
Published: April 2011

We describe the fabrication and characterization of solution processed
organic light emitting diodes (OLEDs) based on novel near-infrared emitting
erbium(III) complexes, consisting of three perfluoroalkyl-β-diketone ligands
and 5-NO2-1,10-phenanthroline as chelating N,N-donor molecule.
The function of N,N molecule is to saturate the coordination sphere of the
erbium ion and to harvest excitation light that can be transferred to the
excited states of the erbium ion. The devices have been fabricated by
spin-coating, using 1 %wt methanol precursor solutions. These Er-complexes
form very uniform thin films. The OLED structure is glass/indium–tin
oxide(ITO) / poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate)
(PEDOT:PSS)/Er-complex/Ca/Al. The good electrical response, with low
threshold voltages (a few volts), together with the very uniform thin films
formed, made these complexes promising for IR emitting displays.
Speech and Magnetic Resonance Imaging Results following Autologous Fat Transplantation to the Velopharynx in Patients with Velopharyngeal Insufficiency
Authors: Filip Charles , Matzen Michael , Aagenses Ingegerd , Aukner Ragnhild , Kjøll Lillian , Høgevold Hans Erik , Åbyholm Frank , Tønseth Kim
Published: April 2011

Objective

To measure velopharyngeal closure with magnetic resonance imaging (MRI) and to evaluate speech when treating velopharyngeal insufficiency (VPI) with autologous fat transplantation to the velopharynx.

Patients

Nine patients were recruited. Six patients had undergone cleft palate repair and subsequently developed VPI. Three were noncleft patients of which one had developed VPI after nasopharyngeal cancer treatment; another patient had developed VPI after combined adenotonsillectomy, and a third patient had VPI of unknown etiology.

Main outcome measure

Preoperative and 1-year postoperative MRIs were obtained during vocal rest and during phonation. Data measured were the velopharyngeal distance in the sagittal plane and the velopharyngeal gap area in the axial plane. Preoperative and 1-year postoperative audio recordings were blinded for scoring independently by three senior speech therapists.

Results

When comparing preoperative and 1-year postoperative MRI during phonation we found a significant reduction of the median velopharyngeal distance from 4 to 0 mm ( p = .011), and a significant reduction of the median velopharyngeal gap area from 42 to 34 mm2 ( p = .038). Nasal turbulence improved significantly ( p = .011). Hypernasality/hyponasality and audible nasal emission did not change significantly.

Conclusions

Autologous fat transplantation to the velopharynx resulted in a significant reduction of the velopharyngeal distance and the velopharyngeal gap area during phonation, as measured by MRI. This was in accordance with a significant improvement in nasal turbulence. However, hypernasality and audible nasal emission did not change significantly and could not be correlated to the MRI findings.
Perceived Ejaculate Volume Reduction in Patients With Erectile Dysfunction: Psychobiologic Correlates
Authors: Corona Giovanni , Boddi Valentina , Gacci Mauro , Sforza Alessandra , Forti Gianni , Mannucci Edoardo , Maggi Mario
Published: April 2011

ABSTRACT: The disorders of orgasm/ejaculation encompass a heterogeneous group of dysfunctions including premature ejaculation, delayed ejaculation, and perceived ejaculate volume reduction (PEVR). The aim of this study was to explore specific associations of PEVR in a consecutive series of 3141 patients (mean age, 51.6 ± 13.1 years) seeking consultation for erectile dysfunction (ED). Among these, 71 were excluded because they underwent prostate surgery. Different clinical and biochemical factors were evaluated along with parameters derived from the Structured Interview on Erectile Dysfunction evaluating the contribution of organic, relational, and intrapsychic factors to ED. After adjustment for confounders, PEVR was specifically associated with the use of androgen deprivation therapy as well as with different other medications including α‐blockers, serotonergic reuptake inhibitor antidepressants, and angiotensin‐converting enzyme inhibitors/angiotensin receptor blockers. A higher prevalence of diabetes mellitus and hypogonadism was observed in patients with PEVR compared with the rest of the sample (23.0% vs 14.1% and 9.1% vs 5.3% respectively; both P < .05). In addition, different sexual parameters such as severe ED (hazard ratio [HR] = 1.25 [1.11–1.41]; P < .0001) and patient's (HR = 1.53 [1.38–1.70]; P < .0001) and partner's (HR = 1.21 [1.07–1.36]; P < .005) hypoactive sexual desire (HSD) were also significantly related to PEVR. Furthermore, PEVR was associated with an impairment of both the relational and intrapsychic components of ED. In a multivariate model, adjusting for age, body mass index, smoking habits, and medications, hypogonadism, diabetes mellitus, severe ED, and patient's and partner's HSD were all independently associated with PEVR. Our results indicate that PEVR is important not only for couple reproductive purposes but also appears to have a distinct role in the couple's sexual performance.