bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Frequency Length Mode PVDF Behavior over Temperature
Authors: Thompson Mitch , Toda Minoru , Ciccarone Melina 
Published: February 2009

AbstractIn an extension of earlier work, the temperature dependent parameters of PVDF operating in the length mode have been measured at frequencies useful in air ultrasound (20kHz to 100kHz) over a -45°C to +65°C temperature range. The length mode resonance of PVDF strips of different lengths was excited by mechanically clamping samples at the mid point during dielectric impedance testing conducted in a desiccated thermal chamber. Material properties were extracted from the impedance magnitude and phase angle data at temperature, and the various sample lengths allowed a range of resonant frequencies to be studied. Overall results generally confirm the visco-elastic behavior of PVDF. Testing was conducted on samples with both thin sputtered metal electrodes (∼60nm) and thicker elastomeric silver ink electrodes (∼8μm) to assess the performance difference. Silver ink is preferred in production as sputtered metal has current density an other limitations, but it causes a serious loss in performance at high frequencies.
Aromatic Polyurea for High Temperature High Energy Density Capacitors
Authors: Wang Yong , Zhou Xin , Lin Minren , Lu Sheng-Guo David , Lin Jun-Hong , Zhang Qiming 
Published: February 2009

AbstractWe investigate aromatic polyureas which can be fabricated in the form of thin films through CVD. It was found that the polymer possesses a flat dielectric response (k∼ 4.2 and loss <1%)) to more than 200°C. The frequency-independent dielectric properties in the investigated frequency range(1kHz∼1MHz), low conductance, low dissipation factor (∼0.005), high breakdown strength (>800MV/m), high energy density (>12J/cm3) and high efficiency suggest this polymer can be a good candidate material for high temperature energy storage capacitors. Breakdown strength was analyzed with Weibull model over a broad temperature range (25°C ∼180°C). Experimental results indicate that aromatic polyurea is more like a nonpolar linear dielectric material because of its highly cross-linked structures. The experiment results further show that this polymer maintains its high performance even at high temperatures.
A New Type of Display Device Based on Remote Swelling and Collapse of a pH Responsive Microgel
Authors: Cook Joseph Peter , Riley Jason 
Published: February 2009

AbstractMicrogel particles of poly(2-vinylpyridine) cross linked with 0.5 wt% divinylbenzene were synthesised. Due to differences in the scattering of light, a dispersion of the particles appears opaque milky white above pH 4.5 and transparent below pH 4.5. The pH of a 0.15 wt% dispersion was modified using a poly(aniline) film as a source/sink of protons and a Ag/AgCl electrode as a source/sink of chloride counterions. The absorption of the sample at 400 nm was typically reduced from c.a. 3.5 to c.a. 0.5 in less than 20 minutes and increased to c.a. 3.2 in less than 20 minutes. This system could form the basis for a new type of display device, but it is insufficiently fast or consistent in its current form.
The Melt Electrospinning of Polycaprolactone (PCL) Ultrafine Fibers
Authors: Subramanian Chitrabala , Ugbolue Samuel C. , Warner Steven B. , Patra Prabir K. 
Published: February 2009

AbstractElectrospinning is a technique of producing nanofibers from polymer solution/melt solely under the influence of electrostatic forces. In this research, we investigated the formation of nanofibers by melt electrospinning polycaprolactone (PCL). The effect of process parameters such as molecular weight, applied voltage, and electrode separation on the fiber diameter was investigated. Controlling the process parameters could help increase the proportion of ultrafine fibers in the melt electrospun nonwoven mat. The velocity of the straight jets was in the range of 0.2-1 m/s. The melt electrospun fibers were characterized with respect to fiber diameter, distribution, mechanical properties and birefringence. Melt electrospun polycaprolactone fibers had a diameter distribution of the order of 5 -20 μm. The birefringence of the melt electrospun fibers increased with decrease in fiber diameter.
Commercial MEMS Case Studies: The Impact of Materials, Processes and Designs
Authors: Martin Jack 
Published: February 2009

AbstractMinimizing risk is an important factor in new product planning because high volume breakthrough products require tens of millions of dollars to develop and bring to market. Sometimes risk can be minimized by following the IC model: build new devices on an existing process – just change the mask set. This approach obviously has limits. Adoption of new materials and processes greatly expands the horizon for “disruptive” products. This paper uses a case study approach to examine how changes in masks, materials and unit processes were used, and will continue to be used, to produce MEMS products for high volume applications.
BioMEMS Technologies for Regenerative Medicine
Authors: Borenstein Jeffrey T. 
Published: February 2009

AbstractThe emergence of BioMEMS fabrication technologies such as soft lithography, micromolding and assembly of 3D structures, and biodegradable microfluidics, are already making significant contributions to the field of regenerative medicine. Over the past decade, BioMEMS have evolved from early silicon laboratory devices to polymer-based structures and even biodegradable constructs suitable for a range ofex vivoandin vivoapplications. These systems are still in the early stages of development, but the long-term potential of the technology promises to enable breakthroughs in health care challenges ranging from the systemic toxicity of drugs to the organ shortage.Ex vivosystems for organ assist applications are emerging for the liver, kidney and lung, and the precision and scalability of BioMEMS fabrication techniques offer the promise of dramatic improvements in device performance and patient outcomes.Ultimately, the greatest benefit from BioMEMS technologies will be realized in applications for implantable devices and systems. Principal advantages include the extreme levels of achievable miniaturization, integration of multiple functions such as delivery, sensing and closed loop control, and the ability of precision microscale and nanoscale features to reproduce the cellular microenvironment to sustain long-term functionality of engineered tissues. Drug delivery systems based on BioMEMS technologies are enabling local, programmable control over drug concentrations and pharmacokinetics for a broad spectrum of conditions and target organs. BioMEMS fabrication methods are also being applied to the development of engineered tissues for applications such as wound healing, microvascular networks and bioartificial organs. Here we review recent progress in BioMEMS-based drug delivery systems, engineered tissue constructs and organ assist devices for a range ofex vivoandin vivoapplications in regenerative medicine.
Fabrication and Hot Switching Behavior of Electroplated Gallium Spheres for MEMS
Authors: Kim Yoonkap , Bahr David 
Published: February 2009

AbstractLiquid metal microscale switches, often using mercury, are sometimes used in place of solid-solid contact switches because of the ability to minimize damage from switching and the ability to make good contacts for electrical and thermal conductivity. However, mercury has potential health and safety problems, and is difficult to use at high frequency (kHz) operation due to poor adhesion between the liquid-solid contacts. One alternative to the mechanical and chemical problems of a liquid mercury switch is using soft metals, such as gallium or tin, as a solid metal sphere for switches that can melt at moderate temperatures. Ga micro-spheres for switching operations were deposited on a substrate consisting of photolithographically patterned W films on SiO2 and Si substrates by electroplating, and the applicability for use in a microscale switch was investigated by characterizing the macro structure, hardness, and electrical performance during switching. The resistivity of the electroplated Ga droplets was similar to the theoretical value for pure Ga, and suggests that the electrodeposited Ga will be suitable for a solid MEMS switch. The hardness of the Ga sphere was 5.7 MPa. This suggests a maximum of ∼40 micron-Newton can be applied to each 50 micron-meter radius Ga contact in the current configuration for switching applications. When the Ga spheres were investigated for electrical performance during hot switching, the resistance increased over six switching cycles, but the original lower resistivity was recovered after a 393 K thermal reflow process.
Transport of Charged Species Across Solid-State Nanopores
Authors: Fung Daisy , Akdemir Eyup , Vitarelli Michael , Sosnov Eugene , Prakash Shaurya 
Published: February 2009

AbstractNanofluidic devices are finding growing interest for a variety of applications. An initial report is presented here on a wide range of parameters influencing transport of ionic species as they translocate across solid-state nanopores. AC electrical bias at low ionic concentration with overlapping electric double layers provides an enhancement of ionic flux over pure DC bias. Furthermore, results also indicate that concentration and pH gradients can be maintained across solid-state nanopores for extended periods of time that can last for several hours in the absence of driving forces such as electric fields.
Growth of Epitaxial Potassium Niobate Film on (100)SrRuO3/(100)SrTiO3 by Hydrothermal Method and their Electromechanical Properties
Authors: Ishikawa Mutsuo , Yasui Shintaro , Utsugi Satoshi , Fujisawa Takashi , Yamada Tomoaki , Morita Takeshi , Kurosawa Minoru , Funakubo Hiroshi 
Published: February 2009

AbstractEpitaxaially-grown KNbO3 thick films over 8 μm in thickness were successfully grown at 220 °C for 6 h on (100)cSrRuO3//SrTiO3 substrates by a hydrothermal method. Epitaxial SrRuO3 layers grown on (100)cSrTiO3 substrates by sputter method were used as bottom electrode layers. Relative dielectric constant and the dielectric loss were 530 and 0.11, respectively. Clear hysteresis loops originated to the ferreoelectricity were observed and a remanent polarization was 25 μC/cm2 at a maximum applied electric field of 540 kV/cm. In addition, the hydrothermal KNbO3 thick film was able to transmitting and receiving of ultrasonic waves over 50MHz.
Three-Dimensional Structure of Helical and Zigzagged Nanowires Using Electron Tomography
Authors: Kim Han Sung , Myung Yoon , Kim Chang Hyun , Bae Seung Yong , Ahn Jae-Pyoung , Park Jeunghee 
Published: February 2009

ABSTRACTElectron tomography and high-resolution transmission electron microscopy were used to characterize the unique three-dimensional structures of helical or zigzagged GaN, ZnGa2O4 and Zn2SnO4 nanowires. The helical GaN nanowires adopt a helical structure that consists of six equivalent <0-111> growth directions with the axial [0001] direction. The ZnGa2O4 nanosprings have four equivalent <011> growth directions with the [001] axial direction. The zigzagged Zn2SnO4 nanowires consisted of linked rhombohedrons structure having the side edges matched to the <011> direction, and the [111] axial direction.
ZnO/Al2O3 Core-shell Nanorod Arrays: Processing, Structural Characterization, and Luminescent Property
Authors: Chen Cheng-Ying , Lin Chin-An , Chen Miin-Jang , Lin Gong-Ru , He Jr-Hau 
Published: February 2009

ABSTRACTWe reported the aqueous chemical method to fabricate the well-aligned ZnO/Al2O3 core-shell nanorod arrays (NRAs). The shell is composed of α-Al2O3 nanocrystals in amorphous Al2O3 layers. The photoluminescence (PL) measurements showed that the enhancement of near-band-edge emission in ZnO NRAs arrays due to the addition of Al2O3 shell was observed. The Al2O3 shell layer resulting in flatband effect near ZnO surface leads to a stronger overlap of the wavefunctions of electrons and holes in the ZnO core, further enhancing the NBE emission.
Raman Spectroscopy of Group IV Nanostructured Semiconductors: Influence of Size and Temperature
Authors: Torres Alfredo , Martínez Oscar , Prieto Carmelo , Jimenez Juan , Rodríguez Andrés , Sangrador Jesús , Rodríguez Tomás 
Published: February 2009

AbstractGroup IV nanostructures have attracted a great deal of attention because of their potential applications in optoelectronics and nanodevices. Raman spectroscopy has been extensively used to characterize nanostructures since it provides non destructive information about their size, by the adequate modeling of the phonon confinement effect. However, the Raman spectrum is also sensitive to other factors, as stress and temperature, which can mix with the size effects borrowing the interpretation of the Raman spectrum. We present herein an analysis of the Raman spectra obtained for Si nanowires; the influence of the excitation conditions and the heat dissipation media are discussed in order to optimize the experimental conditions for reliable spectra acquisition and interpretation.
Size distribution of self assembled Ge nanocrystals determined by photoluminescence
Authors: Rowell Nelson , Lockwood David , Berbezier Isabelle , Szkutnik Pierre David , Ronda Antoine 
Published: February 2009

AbstractGermanium nanocrystals (NCs) were formed by in-situ thermal annealing of an amorphous Ge layer deposited by molecular beam epitaxy on a thin SiO2 layer on Si(001). The Ge NCs were then capped in situ with a thin layer of amorphous Si to prevent oxidation. For the present range of particle sizes (2.5 to 60 nm), the NC photoluminescence (PL) appeared primarily as a wide near-infrared band peaked near 800 meV. The peak energy of the PL band reflects the average NC size and its shape depends on the NC size distribution. Using both the k·p and tight binding theoretical models, we have analyzed the PL spectrum in terms of the NC size distribution required to reproduce the observed asymmetric band shape, which includes, for the smaller diameter NCs, a band gap enlargement due to quantum confinement. The observed size distribution determined from transmission electron microscopy analysis allowed the determination of the nonlinear increase in the PL quantum efficiency with decreasing NC diameter. This implies that, given a good theoretical description of the system, it is possible to evaluate the size distribution of semiconductor NCs from their PL energy dependence.
Sol-gel Synthesis and Characterization of YAG:Ce3+ Phosphors by Various Pre-firing Temperatures
Authors: Hwang Kyu-Seog , Hwangbo Seung , Jeong Ju-Hyun , Lee Young-Hwan , Kim Jin-Tae 
Published: February 2009

AbstractCeria doped-yttrium aluminum garnet (Y3Al5O12:Ce3+, YAG:Ce), which is known as an efficient phosphor, have been widely used in optical display and lighting applications. Improved wet chemical method, sol-gel, has been studied, since conventional solid-state reaction requires a high-temperature and prolonged heating to obtain the pure phase. However, there has been little information, such as on pre-firing temperature, concerning high-quality powder formed by the wet chemical process. In this work, YAG:Ce was synthesized with a salted sol-gel process in which a water solution of inorganic salt with citric acid as additive. Transparent starting sol was pre-fired at 200 ˜ 300°C for 2 hrs in air and final annealing to obtain phase-pure YAG:Ce particles was performed at 1100°C for 2 hrs in argon. The effects of pre-firing temperatures on the crystal structure, morphology and luminescence were investigated. Effects of residual organics in the pre-fired gel on the properties of finally annealed phosphors will be fully discussed on the basis of the results of thermal analysis and chemical structure.
Fabrication of Electrically Active Si-based Thin Films by Pulsed Laser Deposition of SiO/C Dual Targets
Authors: Ono Yusaburo , Kato Yushi , Akita Yasuyuki , Hosaka Makoto , Shiraishi Naoki , Yamaguchi Makoto , Sakata Osami , Yoshimoto Mamoru 
Published: February 2009

AbstractWe investigated the fabrication of Si nanocrystals, including thin films, by annealing the SiO/C/SiO thin films in an Ar atmosphere. The SiO/C/SiO trilayered thin films were deposited on α-Al2O3 (0001), Si (111), or ITO-coated borosilicate glass substrates at room temperature by pulsed laser deposition using dual sintered SiO and graphite targets. The SiO/C/SiO thin films subjected to heat treatment at 500°C included nanocrystalline Si. Measurements by synchrotron radiation X-ray diffraction indicated the formation of Si nanocrystals having a size of 5–10 nm. Fourier transform infrared spectra showed that Si–O stretching and vibrational peak intensities of the as-deposited thin film decreased remarkably after annealing. The C layer in the SiO/C/SiO trilayered thin films is considered to play a role in enhancing the chemical reaction that produces Si nanocrystals through reduction of SiO during heat treatment. The annealed SiO/C-based thin films, including Si nanocrystals, exhibited photosensitive conduction behavior in current–voltage measurements.
Ultrathin oxide films: CaO layers on BaO and SrO
Authors: Mohn Chris E , Allan Neil L. , Harding John H. 
Published: February 2009

AbstractPrompted by renewed interest in the crystalline oxides-on-semiconductors interface, periodic density functional theory and atomistic simulation techniques are used to examine the formation of a layer of CaO on a BaO substrate. We examine how CaO islands which form at coverages less than 100% adjust to the substrate in which the cation-anion separation is substantially larger than in CaO itself. All Ca-O bond lengths in the island are shorter than that in bulk CaO. Corner O atoms in the islands are associated with particularly short Ca-O bond lengths, and the shape of the islands is dominated by (100) edges. Once formed, islands with intact edges will remain intact. Interactions between islands at larger coverages are also investigated and we see the formation of characteristic elliptical gaps and loops.
Structural complexity in AA′MM′O6 Perovskites. A Transmission Electron Microscopy Study
Authors: García-Martín Susana , Urones-Garrote Esteban , Knapp Meghan C. , King Graham , Woodward Patrick M. 
Published: February 2009

AbstractWe have prepared five perovskite compounds which have two different A-site cations and examined the ordering of the A-site lattice through powder X-ray diffraction, TEM, HRTEM, HAADF-STEM, STEM-EELS. NaLaTi2O6 and NaLaZr2O6 show no indication of cation ordering by XRD but TEM analysis reveals that the A-site cations are ordered into layers in nanometer domains which have perpendicular orientations of the layers. NaLaMgTeO6 has larger domains which can be detected by XRD. XRD has revealed that both NaLaMgWO6 and KLaMnWO6 have nearly complete long range layered ordering of the A-site cations. TEM microscopy has further shown that a compositional modulation exists in both compounds. NaLaMgWO6 organizes into alternating stripes ˜24Å wide that are compositionally distinct from each other. KLaMnWO6 shows similar behaviour except with a chessboard pattern.
Abnormal Grain Growth Behavior in Nanostructured Al Thin Films on SiO2/Si Substrates
Authors: Luce Flavia Piegas , Fichtner Paulo , Schelp Luiz Fernando , Zawislak Fernando 
Published: February 2009

AbstractWe report on the formation of nanocrystalline Al thin films (180 nm thick) via magnetron sputtering technique using a step-wise deposition concept where columnar growth is inhibited, giving place to the development of a nanocrystalline mosaic grain arrangement with characteristic diameters of ≈ 30 nm and small size dispersion. The thermal evolution of the grain size distributions is investigated by transmission electron microscopy (TEM) in samples annealed in high vacuum for 3600 s. For the temperature range 300 ≤ T ≤ 462 °C the system presents a 3-D regular growth behavior up to sizes ≈ 70 nm. For T = 475 °C a rather sharp transition from normal to abnormal grain growth occurs. The grains extend to the film thickness and present mean lateral dimensions of ≈ 1000 nm. The observed phenomenon is discussed in terms of a synergetic grain boundary mobility effect caused by the characteristics of the initial nanogranular grain boundary morphology.
Liquid Structures of Metallic Glass-forming Binary Zr Alloys
Authors: Mizuno Akitoshi , Akimoto Toshihiko , Watanabe Masahito , Kohara Shinji , Takata Masaki 
Published: February 2009

ABSTRACTWe have analyzed liquid structures of the binary Zr-TM (TM=Pd, Cu, Ni) alloys as a function of composition to investigate relations with their glass-forming abilities. High-energy x-ray (E=113 keV) diffraction experiments were performed and a conical nozzle levitation (CNL) technique was applied to achieve a containerless condition for highly reactive melts with high temperature. Structure information of the liquid alloys has been obtained with the aid of reverse Monte Carlo simulation. A shoulder was found at high-Q side of the second peak for the structure factor for Zr70Pd30 as well as the Zr70Cu30 alloy and the Zr50Cu50 alloys, which can be indication of the formation of ISRO in the liquid alloys. Liquid Zr-Ni alloys shows an apparent difference in the structure factors between the Zr70Ni30 and the Zr50Ni50 alloys, which can be associated with the formation of the chemical short range ordering, whereas the Zr-Pd alloys show a typical random distribution of atoms.
Management of Mucin-Producing Cystic Neoplasms of the Pancreas
Authors: Fritz Stefan , Warshaw Andrew L. , Thayer Sarah P. 
Published: February 2009

Abstract
During the last decade small lesions of the pancreas have been increasingly recognized in clinical practice. Among these lesions, mucin-producing cystic neoplasms represent a recently described and unique entity among pancreatic tumors. In 1996, the World Health Organization distinguished two different types of mucinous cystic tumors: intraductal papillary mucinous neoplasms (IPMNs) of the pancreas, which are characterized by mucin production, cystic dilation of the pancreatic ducts, and intrapapillary growth, and mucinous cystic neoplasms (MCNs), which are defined by ovarian-like stroma and in most cases do not communicate with pancreatic ducts. Further, IPMNs can be subdivided into main-duct type, mixed-type, and branch-duct type tumors. Older data did not distinguish among different subsets of cystic neoplasms of the pancreas, and consequently many databases were inconsistent. Histopathologically, both IPMNs and MCNs demonstrate a wide spectrum of cellular atypia ranging from mild mucinous hyperplasia to invasive adenocarcinoma. Because mucinous cystic neoplasms of the pancreas show significant differences in clinical behavior from patient to patient, knowledge of the clinicopathologic characteristics and natural history of specific subtypes of IPMNs and MCNs has become crucial for physicians working in the field of gastroenterology. The present work offers an overview of current and generally accepted clinical guidelines for the diagnosis and treatment of IPMNs and MCNs.