bluuebunny/crossref_metadata_2025 huggingface dataset:
PHYSICO-CHEMICAL, STRUCTURAL AND ELECTRICAL STUDIES OF Cu–Zn FERRITES SYNTHESIZED BY NOVEL CHEMICAL ROUTE
Authors: LOHAR K. S. , PATANGE S. M. , MANE D. R. , SHIRSATH SAGAR E. , SHINDE N. D. , KULKARNI NILESH
Published: April 2011

The physico-chemical, structural and electrical properties of zinc substituted copper ferrites having the general formula Cu 1-x Zn x Fe 2 O 4(x=0.0 to x=0.8) have been studied as a function of zinc ion concentration. The sample was prepared by co-precipitation method from corresponding metal sulphates. X-ray diffraction patterns were used to confirm the structure of synthesized samples. The calculated and theoretical values of average lattice constant, tetrahedral bond, tetrahedral edge and unshared octahedral edge were found to increase, while the shared octahedral edge and octahedral bond decrease as the Zn ion concentration increases. The dielectric constant (ε′) and dielectric loss tangent ( tan δ) were measured at a constant frequency 1 kHz as a function of temperature. The dielectric constant and loss tangent were found to increase with rise in temperature. The conduction mechanism in these ferrites is discussed on the basis of electron exchange between Fe 2+ and Fe 3+ ions. The temperature dependent dc resistivity was carried out in the temperature range 300 to 800 K. The plots of log ρ versus 103/ T are linear showing two regions, corresponding to ferrimagnetic and paramagnetic regions.
POLARONIC EFFECTS IN WURTZITE GaN/AlxGa1-xN QUANTUM WELLS
Authors: ZHAO FENG-QI , ZHANG MIN
Published: April 2011

The properties of polarons in a wurtzite GaN / Al x Ga 1-x N quantum well (QW) are investigated by adopting an effective-mass approximation and a modified Lee–Low–Pines variational method. The ground-state energy, the transition energy and the phonon contributions due to various optical-phonon modes to the ground-state energy as functions of the well width are given. The effects of the confined (CF) optical phonon mode, interface (IF)-optical phonon modes, half-space (HS) phonon modes, the anisotropy of the electron effective band mass and the phonon frequency are respectively considered (or included) in the calculation. The results have been compared with those of the zinc-blende structure. The numerical result indicates that both the ground-state energies of polaron and the transition energy decrease with increasing well width. For QWs with larger well width (> 10 nm), the total contribution to polaronic energy mainly comes from the confined mode, and for QWs with narrower well width (< 2 nm), the total contribution to polaronic energy mainly comes from the IF-optical phonon and HS phonon modes. And the phonon contribution in GaN/Al x Ga 1-x N QW is much larger than that in GaAs/Al x Ga 1-x As QW. The two IF-optical phonon modes with lower frequency, the transverse optical-like CF and HS modes are extremely small so that they can be neglected in the further discussion.
Effects of Maternal Exposure to Cow's Milk High or Low in Isoflavones on Carcinogen-Induced Mammary Tumorigenesis among Rat Offspring
Authors: Nielsen Tina Skau , Purup Stig , Wärri Anni , Godschalk Roger W. , Hilakivi-Clarke Leena
Published: April 2011

We investigated whether maternal exposure during pregnancy to cow's milk containing endogenous estrogens and insulin-like growth factor 1 (IGF-1) and either high or low levels of isoflavones from dietary legumes (HIM and LIM, respectively) affected carcinogen-induced mammary carcinogenesis in female rat offspring. Pregnant Sprague-Dawley rats were given HIM, LIM, or tap water (control) from gestational day (GD) 11 until birth; hereafter all rats received tap water. Mammary tumorigenesis was induced by administrating 7,12-dimethylbenz[a]anthracene (DMBA) on postnatal day 50. No differences in maternal serum estradiol (P = 0.19) and IGF-1 levels (P = 0.15) at GD 19 or birth weight among the milk and water groups were seen, but estradiol, and IGF-1 levels and birth weight were numerically higher in the LIM group than in the HIM group. Puberty onset occurred earlier in the LIM offspring than in controls (P = 0.03). Although the high isoflavone content seemed to prevent the effect on circulating estradiol and IGF-1 levels and advanced puberty onset seen in the LIM group, HIM increased DMBA–DNA adducts in the mammary gland and tended to increase mammary tumorigenesis. In contrast, offspring exposed to LIM in utero, did not exhibit increased breast cancer risk, despite having higher estradiol and IGF-1 environment and consequently earlier puberty onset. These results indicate that the phytochemical content in the cow's milk, consumed by a pregnant dam, determines how milk affects the offspring. Cancer Prev Res; 4(5); 694–701. ©2011 AACR.
Association between Prescription of Conventional or Atypical Antipsychotic Drugs and Mortality in Older Persons with Alzheimer’s Disease
Authors: Musicco Massimo , Palmer Katie , Russo Antonio , Caltagirone Carlo , Adorni Fulvio , Pettenati Carla , Bisanti Luigi
Published: April 2011

Background/Aims: To evaluate whether dementia patients prescribed antipsychotic drugs have a higher mortality compared to unexposed patients, and to investigate whether there are differences in mortality associated with exposure to conventional versus atypical antipsychotic drugs. Methods: Retrospective population cohort study with information gathered from the Italian Health Information System. All 4,369 residents of Milan (Italy) aged 60 years or older who were newly prescribed an antidementia drug (donepezil, rivastigmine or galantamine) from January 2002 to June 2008 were included. All new users of antipsychotic drugs in this cohort were categorized according to conventional (n = 156) or atypical (n = 806) drug exposure. The mortality risks of users of conventional or atypical antipsychotics compared to nonusers were evaluated with survival analysis, considering exposure to antipsychotic drugs as a time-dependent variable. Results: Mortality was increased two- and fivefold in users of atypical and conventional antipsychotics, respectively, with respect to nonusers. Conclusions: Dementia patients prescribed antipsychotic drugs had a higher risk of death. This risk was highest for those prescribed conventional antipsychotics. At least part of the excess mortality may be due to the underlying neuropsychiatric symptoms that prompted the use of antipsychotics rather than a direct medication effect.
An Ocean Observing and Prediction Experiment in Prince William Sound, Alaska
Authors: Schoch G. Carl , Chao Yi , Colas Francois , Farrara John , McCammon Molly , Olsson Peter , Singhal Gaurav
Published: April 2011

The observing and forecasting conditions of coastal oceans in Alaska is technically challenging because of the mountainous terrain, the notoriously stormy seas, and a complex hydrological system of freshwater from rivers and glaciers. The Alaska Ocean Observing System and their partners developed a demonstration project over a 5-yr period in Prince William Sound. This location was chosen because of historical efforts to monitor ocean circulation following the Exxon Valdez oil spill of 1989. The primary goal is to develop a quasi-operational system that delivers weather and ocean information in near–real time to diverse user communities. This observing system now consists of a spatial array of atmospheric and oceanic sensors and a new generation of computer models to numerically simulate and forecast weather, waves, and ocean circulation. The project culminated in a 2009 field experiment that evaluated the performance of the model forecasts. Three ships, 44 surface drifters, an underwater glider, and an autonomous underwater vehicle, as well as two shore-based surface current radar systems, augmented the routine atmospheric and oceanographic measurements from weather stations and oceanographic buoys. Observations from terrestrial and moored weather stations were compared with atmospheric circulation forecasts, and wave gauges provided data that were used to evaluate the forecasts of significant wave heights and periods. The radar current mappers and drifter buoys validated the surface ocean circulation forecasts. Improved observations and forecasts of coastal oceans will benefit oil spill responders, commercial shippers that convey large amounts of freight to and from Alaska, and U.S. Coast Guard search-and-rescue operations.
Simple two-step fabrication method of Bi2Te3 nanowires
Authors: Kang Joohoon , Noh Jin-Seo , Lee Wooyoung
Published: April 2011

Bismuth telluride (Bi2Te3) is an attractive material for both thermoelectric and topological insulator applications. Its performance is expected to be greatly improved when the material takes nanowire structures. However, it is very difficult to grow high-quality Bi2Te3 nanowires. In this study, a simple and reliable method for the growth of Bi2Te3 nanowires is reported, which uses post-sputtering and annealing in combination with the conventional method involving on-film formation of nanowires. Transmission electron microscopy study shows that Bi2Te3 nanowires grown by our technique are highly single-crystalline and oriented along [110] direction.
Electromagnetic modeling of waveguide amplifier based on Nd3+ Si-rich SiO2 layers by means of the ADE-FDTD method
Authors: Dufour Christian , Cardin Julien , Debieu Olivier , Fafin Alexandre , Gourbilleau Fabrice
Published: April 2011

By means of ADE-FDTD method, this paper investigates the electromagnetic modelling of a rib-loaded waveguide composed of a Nd3+ doped Silicon Rich Silicon Oxide active layer sandwiched between a SiO2 bottom cladding and a SiO2 rib. The Auxilliary Differential Equations are the rate equations which govern the levels populations. The Finite Difference Time Domain (FDTD) scheme is used to solve the space and time dependent Maxwell equations which describe the electromagnetic field in a copropagating scheme of both pumping (λ
pump
= 488 nm) and signal (λ
signal
= 1064 nm) waves. Such systems are characterized by extremely different specific times such as the period of electromagnetic field ~ 10-15 s and the lifetimes of the electronic levels between ~ 10-10s and ~ 10-4 s. The time scaling method is used in addition to specific initial conditions in order to decrease the computational time. We show maps of the Poynting vector along the propagation direction as a function of the silicon nanograin (Si-ng) concentrations. A threshold value of 1024 Si-ng m-3 is extracted below which the pump wave can propagate so that a signal amplication is possible.
Detection of Vibrio parahaemolyticus in mediterranean mussels (Mytilus galloprovincialis) in Slovenia
Authors: Henigman Urška , Biasizzo Majda , Vadnjal Stanka , Kirbiš Andrej , Toplak Ivan , Barlič-Maganja Darja
Published: April 2011

The aim of this study was to determine the prevalence ofVibrio parahaemolyticusin shellfish samples harvested along the Slovenian coast. Shellfish samples of Mediterranean mussels (Mytilus galloprovincialis) were collected along the Slovenian coast at four locations (Seča, Piran, Strunjan and Debeli Rtič) between 2006 and 2008. Samples were examined and analysed for the presence ofV. parahaemolyticusby conventional and molecular methods. The presence ofVibrioin the samples was examined by conventional methods on plate grown bacterial cells before and after enrichment in alkaline saline peptone water (ASPW). PCR methods were used for the detection ofV. parahaemolyticus-specifictoxRandtlhgenes and of the virulence-associatedtdhandtrhgenes. Out of 168 samples examined, 24 were positive fortoxRandtlhgenes by PCR from enrichment broth. Five out of 62 (8.1%), 4 out of 32 (12.5%) and 15 out of 74 (20.2%) samples were positive in 2006, 2007 and 2008, respectively. Colonies ofV. parahaemolyticuswere isolated from only one sample positive forV. parahaemolyticusby PCR.
Carbon Fiber Reinforced Rigidizable Space Structures
Authors: Sarles Stephen Andrew , Bullions Todd , Mefford Thompson , Riffle Judy , Leo Don
Published: April 2011

In attempts to provide an active solution for the rigidization of flexible space structures, internal resistive heating is applied to a novel thermosetting resin. Carbon-fiber tow coated in U-Nyte Set 201A, which cures at ∼150°C, was heated by passing electric current through the reinforcing material. Using a proportional-integral (PI) controller, precise temperature control of the heating process was established. Samples cured via controlled internal resistive heating were heated to 160°C and underwent material consolidation in less than 7 minutes. A change in material stiffness was measured to be almost two orders of magnitude greater than that of an uncured material.
The Crystalline and Dielectric Properties of 0.38(Bi1−xLax)ScO3-0.62PbTiO3 Ferroelectric Ceramics
Authors: Chen Yi , Lan Dejun , Chen Qiang , Xu Zhuo , Yue Xi , Xiao Dingquan , Zhu Jianguo
Published: April 2011

To investigate the effects of partially substitution of lanthanum for bismuth in the BiScO3-PbTiO3 (BSPT) ceramics, the 0.38(Bi1−xLax)ScO3-0.62PbTiO3 (BLSPTx) ceramics were prepared by using conventional solid state process. It was found that the partial replacement of lanthanum for bismuth do not affects the crystalline structure of the BSPT ceramics. With increasing of the lanthanum content, the grains of BLSPTx ceramics grown much bigger than those of BSPT ceramics when BLSPTx and BSPT ceramics were sintered at the same temperature. The temperature dependence of dielectric permittivity of BLSPTx ceramics shows that the Curie temperature (Tc) shifts toward lower temperature with the increasing of lanthanum content, and the BLSPTx samples for x=0.02 show the highest value of the dielectric constant at Tc.
Development of a Micro fluidic Nanoscale Protein Sensor Device for Improving Vascular Surgical Outcomes
Authors: Prasad Shalini
Published: April 2011

The normal physiologic response of vascular surgery is one of acute and intense inflammation and thrombosis. Research to date on improving outcomes after surgery has focused on drugs known to be active with the adrenergic system more specifically statins. Till date there has been no correlation between inflammation post surgery and the effect of perioperative anti-inflammatory drugs on improving surgical outcomes. The goal of this research is to characterize the role perioperative inflammation and thrombosis plays in determining outcomes after surgery. The goal of this particular application is to identify two specific pro-inflammatory protein markers namely C-reactive protein (CRP) and Myloperoxidase (MPO) associated with thrombosis from a wide range of serum samples. This is achieved by integrating the principles of fabrication associated with micro and nanotechnology to develop a sensor device comprising of nano ordered porous alumina membrane embedded in an elastomer (polydimethylsiloxane, PDMS) micro fluidic base. The nano porous membrane is selectively functionalized by a two level masking technique to the binding of CRP and MPO in selected areas. The binding event results in an electrochemical reaction that in turn produces a change in the surface charge. This in turn produces a measurable change to the electrical voltage. This is measured in an in-situ, non-invasive manner from selectively metalized areas of the nano membrane. Energy density analysis yielded unique electrical identifiers for each of the protein markers. Detection sensitivity of the order of 10 ppm was observed.
Ink-jet printing of ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymers
Authors: Zhang Shihai , Liang Ziqi , Wang Qing , Zhang Q.M.
Published: April 2011

Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymers are well known for their excellent ferroelectric and other related properties and they are being exploited as active components in many microdevices such as ferroelectric memory cells and infrared sensors. Compared with conventional photolithography, ink-jet printing provides a low-cost versatile method to fabricate polymer micro-devices. In this paper, the influences of driving waveform at the jet head, ink concentration, substrate chemistry, and the solvent quality on the printed P(VDF-TrFE) dots were investigated. It was found that well-defined P(VDF-TrFE) micro-dots with diameter of less than 30 mm and thickness of ∼1 μm can be printed by using a mixed solvent system, consisting of a good solvent with relatively low boiling temperature and a poor solvent with high boiling temperature, on perfluorinated hydrophobic gold surface. The printed P(VDF-TrFE) micro-dots possess crystallinity comparable to that of the bulk sample, suggesting that ink-jet printing technology is a promising micro-fabrication technology for manufacturing P(VDF-TrFE)-based micro-sensors and other micro-devices.
Investigation of the Physics of Transduction in Nafion / Ionic Liquid Composite Membranes
Authors: Bennett Matthew , Akle Barbar , Leo Donald
Published: April 2011

Ionomeric polymer actuators based on Nafion membranes exhibit large bending motion (1%) under the application of small voltages (1-5 V). Actuation in these materials is believed to arise from the field-induced motion of mobile charges when a voltage is applied. In order for this charge motion to occur, the material must be swollen with a diluent, typically water. However, dehydration of the water limits the lifetime of these actuators in non-aqueous environments. Recently, highly stable ionic liquids have been demonstrated as viable diluents for these actuators. In the current paper, the physics of transduction in these ionic liquid-swollen Nafion membranes are investigated. Small-angle X-ray scattering reveals that the structure and properties of the ionic liquid have a strong influence on the morphology of the composites. Infrared spectroscopy is used to probe the ion associations within the films and shows that the ionic liquids are able to effectively mobilize the counterions of the Nafion membrane. Nuclear magnetic resonance spectroscopy is also used to investigate the composites and reveals that the mobility of the counterions increases as the content of ionic liquid within the membrane is increased. The results of these characterizations are compared to an experimental investigation of transduction in Nafion / ionic liquid composites to form an interpretation of the mechanisms of actuation. This comparison reveals that the counterions of the Nafion membrane are the primary charge carriers and that it is the motion of these mobile charges that gives rise to the actuation behavior of the films.
Organic Field-Effect Transistors, Inverters, and Logic Circuits on Gate Electrets
Authors: Huang Cheng , West James E. , Katz Howard E.
Published: April 2011

By incorporating dielectrics with stored electric fields and organic semiconductors, new organic electronic components such as circuits with controlling voltages “restored” for transistor tuning can be developed. We have successfully used excellent electret materials including charged and surface-treated silicon dioxide (SiO2) and silsesquioxane (SSQ) polymers as the dielectric layer in organic field-effect transistors (OFETs). Charge injection and quasipermanent charge storage induce threshold voltage shifts and current modulation, which results from the built-in electric fields in the conduction channels. Static and dynamic characteristics of organic thin-film transistors (OTFTs) such as charging conditions and voltage/current retention were evaluated. In addition, self-assembled monolayers (SAMs) of dipolar molecules have been utilized in the dielectric layer, with different mechanisms but similar effects compared to charged dielectrics. We also present new OFET unipolar inverters, comprised of only two simple OTFTs with enhancement-mode driver and depletion-mode load to implement full-swing organic logic circuits for process simplification of electronic components in organic electronics.
Electronic Structure of PuCoGa5 and UCoGa5
Authors: Bauer Eric , Durakiewicz T. , Butterfield M. T. , Guziewicz E. , Joyce J. J. , Olson C. G. , Morales L. A. , Sarrao J. L. , Thompson J. D.
Published: April 2011

The electronic structure of the Pu-based superconductor PuCoGa5 and the Pauli paramagnet UCoGa5 is investigated using photoemission spectroscopy. The photoemission data of PuCoGa5 reveal features at the Fermi energy EF and about 1-1.5 eV below EF indicative of itinerant and localized f-electrons, respectively. Angle-resolved spectra of UCoGa5 show two peaks at similar energies that are highly dispersive, providing evidence for itinerant character of the f-electrons in this material. A comparison of the PuCoGa5 and UCoGa5 data to the spectra of α-Pu and δ-Pu serves to place PuCoGa5 within the context of the more general electronic structure problem in elemental Pu.
Polymer Assisted Deposition (PAD) of thin metal films: A new technique to the preparation of metal oxides and reduced metal films
Authors: Shukla Piyush , Lin Yuan , Minogue Edel M , Burrell Anthony K , McCleskey T Mark , Jia Quanxi , Lu Ping
Published: April 2011

Currently, there are a variety of techniques to deposit metal thin films ranging from high vacuum techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), through to solution methods like sol-gel. While the vacuum techniques can be limited by size and cost, sol-gel can be limited be the availability of appropriate precursors. All of these techniques have the further limitation that they cannot be used to coat porous materials conformally.

Polymer assisted deposition (PAD) addresses some of the limitations of sol-gel and costs of high vacuum techniques. PAD utilizes an aqueous polymer to bind a metal or metal complex that serves both to encapsulate the metal to prevent chemical reaction and maintain an even distribution of the metal in solution. Another advantage that PAD has is that the same solution can be used as precursors for the growth of metal oxide or reduced metal films. Herein, we report on the utility of PAD in preparing metal oxide films used to conformally coat porous material and reduced metal films.
Design and application of gradient annealing devices for the parallel thermal processing of Fe/Pt multilayers
Authors: Thienhaus Sigurd , Hiergeist Robert , Savan Alan , Ludwig Alfred
Published: April 2011

This paper discusses the design and use of gradient annealing devices. Generally, it is intended to use such devices for the rapid optimization of thin film materials by simultaneous thermal processing at different temperatures. Furthermore, these devices are efficient for short- time annealing experiments. They are used in order to quickly vary the annealing parameters (temperature, time) from sample to sample. Here, nanoscale Fe/Pt multilayer precursor thin films for the fabrication of hard magnetic Fe-Pt thin films are investigated as a test system. First results prove the usefulness of the gradient annealing devices for high-throughput experiments.
Combinatorial synthesis of (Al,Ti)N thin films via pulsed laser deposition
Authors: Cho Clara Ji-Hyun , Gerhardt Rosario A , G. Kelekanjeri V. Siva Kumar , Koinuma Hideomi
Published: April 2011

Aluminum nitride (AlN), a wide band gap semiconductor (Eg = 6.2eV), has potential applications in microelectronics due to its excellent insulating properties and compatibility with silicon [1,2]. More recently, the use of AlN thin films in high electron mobility transistors, light emitting diodes and UV sources is explored by altering the band gap of the material [3]. The present work describes the combinatorial synthesis of (Al,Ti)N thin films via pulsed laser deposition (PLD) technique to obtain desirable compositional spreads and corresponding variations in the electrical properties. Films of AlN, TiN and (Al,Ti)N were deposited on 6H-SiC (0001) substrates held at a temperature of 680°C. The surface quality of the films examined using an AFM revealed island growth of SiO2 and other growth patterns possibly related to substrate defects.

X-ray diffraction studies indicated that the growth of AlN and TiN films occurred with corresponding habit planes of (0002) and (111) parallel to the substrate surface. Compositional investigations conducted using energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS) showed systematic changes in the Al and Ti composition across the thickness of the compositional spread film. Cross-sectional analysis of (Al,Ti)N films conducted in a high-resolution transmission electron microscope revealed that the films were multi-layered. Several orders of magnitude decrease in the measured resistivity across a 15 mm length (Al,Ti)N film was noted corresponding to a systematic increase in the Ti content. Further optimization of deposition conditions is essential for producing thicker films.
Rules-Driven Materials Design Using an Informatics-Based Approach
Authors: Muellerleile Joan T. , Ferris Kim F. , Jones Dumont M. , Hyatt Roger W.
Published: April 2011

A rules-driven, informatics-based approach to multiply-constrained materials design is outlined, employing the example of polymer coating design for silica fibers. This approach to the inverse mapping problem of structure generation from design constraints and quantitative structure-property relationships (QSPRs) emphasizes design rule generation and analysis. Using this approach addresses several issues in new materials discovery: 1) factoring a larger design problem into tractable components, 2) integrating physical and non-physical requirements (such as cost), 3) identifying information gaps that must be resolved to complete a design, and 4) identifying situations in which a solution consistent with known information is not feasible.
High-Throughput Measurement of Magnetostriction Using MEMS and Composition Spreads
Authors: Woo Noble C. , Ng Bryan G. , van Dover R. B.
Published: April 2011

While measurement of magnetostriction in bulk materials is readily accomplished using a strain gauge, measurement of this quantity for thin films presents a greater challenge, and typically involves measurement of the overall wafer curvature (for a film of uniform composition) as a function of field. In order to evaluate magnetostriction locally in composition-spread samples, we have developed a method using a dense array of pre-fabricated cantilever beams on a silicon substrate prepared using MEMS techniques. Differential strain in the thin film/cantilever system results in curvature which is detected using an optical (laser/position-sensitive-detector) system. A magnetic field is applied using two orthogonal Helmholtz coils, and the resulting deflection-field curves are used to determine the saturation magnetostriction λs as well as dλ/dH. Our composition-spread films are prepared using a three gun on-axis magnetron cosputtering system. The position-dependent composition is inferred using rate calibrations and verified with electron microprobe and Rutherford Backscattering Spectroscopy. Preliminary experiments have validated the technique and the system has been used to measure magnetostriction in the Ni-Fe system. Our approach can also be used to measure properties of giant magnetostrictive materials (e.g. TbFe/Fe multilayers) as a function of layer thicknesses, or thin film shape-memory alloys, including magnetic shape-memory alloys.
Warehousing the Dental Materials Data: A Prototype
Authors: Li Yong
Published: April 2011

This paper presents a preliminary investigation on the effectiveness of the new data management technique of data warehousing in organizing dental materials data in order to provide the efficient information services such as data retrieval and materials selection. A scaled-down version of the data warehouse for dental materials is constructed and an English Query application, which allows the end users to formulate their queries in natural English language, is developed on top of the data warehouse. The data warehouse supports five types of queries from basic practice of data retrieval to more advanced information service of materials selection. The results have demonstrated that the data warehousing technique is of a great potential in storing, processing and managing dental materials data.
Towards Low Cost Disposable High Throughput Screening Devices
Authors: Diaz-Quijada Gerardo Antonio , Peytavi Regis , Nantel André , Roy Emmanuel , Bergeron Michel G. , Dumoulin Michel M. , Veres Teodor
Published: April 2011

Microarrays have become one of the most convenient tools for high throughput screening, supporting major advances in genomics and proteomics. Other important applications can be found in medical diagnostics, detection of biothreats, drug discovery, etc. Integration of microarrays with microfluidic devices can be highly advantageous in terms of portability, shorter analysis time and lower consumption of expensive biological analytes. Since fabrication of microfluidic devices using traditional materials such as glass is rather expensive, there is a high interest in employing polymeric materials as a low cost alternative that is suitable for mass production. A number of commercially available plastic materials were reviewed for this purpose and poly(methylmethacrylate) and Zeonor™ 1060R were identified as promising candidates, for which methods for surface modification and covalent immobilization of DNA oligonucleotide were developed. In addition, we present proof-of-concept plastic-based microarrays with and without integration with microfluidics.
High-Porosity Nanoporous Silica via Nanocasting Template of Hydrogels
Authors: Nakamura Takanori , Kurumada Ken-ichi , Suzuki Atsushi , Umeda Naoki , Kishimoto Naoki
Published: April 2011

High-porosity nanoporous silica was prepared by nanocasting method using N-isopropylacrylamide (NIPAm) cross-linked by N, N’-methelenbisacrylamide (BIS) as the templating agent. The obtained silica was a bulk silica with good transparency indicating that the characteristic length-scale of the obtained silica is in the nanoscopic scale being much smaller than that of the wave length of visible light. Nitrogen adsorption/desorption measurements revealed that the nano porosity increases up to 80% with the weight ratio of NIPAm to silica. The mean pore size (radius) also increased with the weight ratio in the region smaller than 10nm. TEM observation revealed that the nanoscopic network structure was replicated into tube-like nanopores randomly distributed in the silica matrix. The whole nanoscopic morphology of these tube-like nanopores was much like as the predicted for the cross-linked polymer.
biomimetic Hydrogel/apatite Nanocomposite Scaffolds for Bone Regeneration
Authors: Jabbari Esmaiel
Published: April 2011

Bone is a composite material consisting of aqueous gel and mineral phases. The aqueous gel phase gives bone its form and contributes to its ability to resist tension, while the mineral component resists compression. The combination of a hard inorganic phase and an elastic gel network provides bone with unique mechanical properties as well as a medium for diffusion and release of biologically active agents and it also facilitates communication with the cellular environment. A tissue engineered synthetic biomaterial as a scaffold for bone regeneration should provide temporary structural support to the reconstructed region and a medium for solubilization, diffusion, release of nutrients and growth factors, and their interactions with cells. In this work, the material and biologic properties of a novel synthetic matrix metalloproteinase (MMP) degradable hydrogel/apatite nanocomposite is investigated for its usefulness as a model matrix to mimic the gel and mineral components of the bone matrix and to fabricate aqueous-based scaffolds for bone regeneration. The gel phase is made from poly(lactide-ethylene oxide-fumarate), hereafter designated as PLEOF, terpolymer in which the water content can be adjusted by changing the ratio of the hydrophobic (lactide) to hydrophilic (ethylene oxide) oligomers. The hydrogel and apatite phases are crosslinked using an MMP degradable peptide crosslinker to modulate the matrix degradation kinetics with the migration of bone marrow stromal (BMS) cells. The results demonstrate that MMP degradable scaffolds fabricated from the PLEOF hydrogel and apatite nanoparticles are biocompatible and support cell attachment and migration.
Transport of molecules through carbon nanotube channels in aqueous environment: A molecular dynamics study
Authors: Xue Yongqiang , Chen Maodu
Published: April 2011

We present molecular dynamics simulation of molecules transporting through carbon nanotubes for applications in engineered flow channels, focusing on the dynamics of molecules spontaneously inserted into the nanotube channel in aqueous environment. The molecules studied include a C60 molecule, a finite segment of carbon nanotube with smaller diameter, and single/double- stranded DNA molecules. We show that in the absence of water solvation, the van der Waals interaction between the molecule and the nanotube wall can induce a rapid spontaneous encapsulation of the molecule inside the nanotube channel. The encapsulation process is strongly impeded for nanotube dissolved in water due to the competition between the van der Waals, hydrophobic and hydrogen bonding interactions in the nanotube/water/molecule complex. Water adsorption inside the nanotube channel plays an important role in determining the dynamics of the spontaneous insertion process.
Microstructured Surfaces for Drag Reduction Purposes: Experiments and Simulations on Rectangular 2D Riblets
Authors: Rapp Håkan , Zoric Igor , Kasemo Bengt
Published: April 2011

It is well established that properly structured surface exhibits a lower friction drag, when exposed to a turbulent boundary layer, than a smooth surface under the same flow conditions. The observed drag decrease is usually attributed to an increased thickness of the viscous sublayer. In this work we examine the friction drag reducing mechanism. Two parallel approaches towards achieving this goal are presented. Photolithography was used to manufacture rectangular riblets in the 10∝m range on a standard 4” silicon wafer. A special compact plane channel system was designed and used for measurements of the frictional drag on structured surfaces in the turbulent flow covering a wide Reynolds number range. Navier-Stokes equation, for the examined drag reducing geometry, was solved in the laminar regime with appropriate boundary conditions. The resulting velocity field was used to extract the protrusion heights difference for streamwise and spanwise flows over the structured surface. The latter was then related to the experimentally measured drag reduction slope. We show that in case of a rectangular riblet, with a size of the order of one wall unit, the observed drag reduction can be accounted for within the above model.
Formation of water at a Pt(111) surface: A study using the reactive force field (ReaxFF)
Authors: Buehler Markus J. , Duin Adri C.T. van , Jacob Timo , Jang Yunhee , Merinov Boris , Goddard William A.
Published: April 2011

In this paper, we report preliminary studies of formation of water from molecular oxygen and hydrogen. Using a series of atomistic simulations carried at finite temperature, we describe the dynamics of water formation at a Pt catalyst using a new reactive ReaxFF potential. By performing a series of studies, we obtain statistically meaningful trajectories to extract rate constants of water formation. This allows an estimate for the activation energy during water formation, which is found to be in reasonable agreement with the activation barrier calculated by restraint driven molecular dynamics simulation of water formation at the Pt surface.
Synthesis and Optical Properties of Oriented Cu Nanoparticles
Authors: Siwach Om Parkash , Sen P.
Published: April 2011

Crystallographic orientation of atomic planes makes a metal amenable to specific properties as desired in catalysis and environment sensing. Oriented metal nanoparticles are however less known. Here we present X-ray diffraction, transmission electron microscopy and atomic force microscopy data to provide evidence of copper nanoparticles with preferred orientation, achieved by electro-explosion of copper wires in an aqueous medium. The optical absorption in these particles is devoid of the usual Mie resonance at ∼ 580 nm, while maintaining bulk-like lattice periodicity. Under the highest reorientation (largest orientation index), absorption in the ultraviolet region is characterized by distinct and sharp resonant peaks, which are correlated with occupied valence band density of state (DOS) from copper clusters, making these truly crystalline particles with atom-like electronic properties.
Microstructure and Electrical Characteristics of Plasma Sprayed Thick Film Mn-Co-Ni Oxide Thermistor
Authors: Liang Shanshan , Ravi Bhuvaragasamy , Sampath Sanjay , Gambino Richard J.
Published: April 2011

Mn-Co-Ni-O spinel, owing to its large temperature dependant resistivity, is an attractive ternary system for negative temperature coefficient (NTC) thermistor applications, particularly in oxygen rich environments. This research explores the potential of plasma spray as a method for the fabrication of thick film Mn-Co-Ni-O thermistors. Nanostructured Mn-Co-Ni-O spinel powders were synthesized by gel combustion method and were air-plasma-sprayed on to alumina substrates. The as-sprayed deposit formed a rocksalt structure rather than a cubic spinel structure. Annealing in air at 600°C for 3 hours resulted in transformation to the spinel structure while higher temperature annealing resulted in phase separation of rocksalt phase at 1250°C and recombination into spinel monophase at 1350°C. Temperature dependent measurement of resistivity showed -4 to -1% temperature coefficient of resistivity (TCR) from room temperature to 250oC with high reproducibility, making the low temperature annealed coating suitable in thermistor applications.
A Kinetic Study of Mediator-Template Assembly of Gold Nanoparticles
Authors: Zhong I-IM Stephanie , Ip Wui , Pak Alice , Luo Jin , Zhong Chuan-Jian
Published: April 2011

This paper describes a kinetic study of the mediator-template assembly of gold nanoparticles in solutions based on the spectrophotometric measurement of the surface plasmon resonance optical property. Gold nanoparticles of ∼5 nm diameter encapsulated with tetraoctylammonium bromide shells were studied as a model system. The core-shell nanoparticles were assembled into 3D spherical assemblies via a mediator-template assembly route in which a thioether-based multidentate ligand functions as a mediator and the tetraoctylammonium shell molecules function as a templating agent. In this report, the results were compared with those obtained for the assembly of gold nanoparticles in several different systems with features similar to the mediator-template assembly. The findings further provided further insights into understanding the kinetic factors governing the assembly of nanoparticles, and have important implications to the design and control of the nanostructures for sensory and catalytic applications.
Selective Detection of Cholesterol Using Carbon Nanotube Based Biochip
Authors: Roy Somenath , Vedala Harindra , Choi Won Bong
Published: April 2011

A novel type of working electrode based on MWCNT is fabricated on silicon substrate for detection of total cholesterol. Multiwall carbon nanotubes (MWNT), which are vertically grown on a silicon platform, promote heterogeneous electron transfer between the enzyme and the working electrode. Immobilization of cholesterol oxidase (Pseudomonas fluorescens.) on the electrode is done by entrapment of the enzyme in a bio-friendly, water soluble polymer, polyvinyl alcohol (PVA), which also increases the hydrophilicity of the carbon nanotube (CNT) surface (with experimental evidence) and thereby facilitating the intimate attachment of the protein molecules. Cyclic voltammograms exhibit efficient detection of cholesterol in the range of 100-300 mg/dl, which covers the entire range of possible cholesterol concentration in human blood. The influence of interferents, like glucose, ascorbic acid and uric acid, present in the physiological fluids, is also examined. Owing to its compatibility with standard silicon microfabrication technology, the signal processing circuitry can also be integrated onto the same silicon substrate yielding a compact miniaturized biochip.
Properties of gas sensor using CNTs thin film prepared by PLD/CVD method
Authors: Ueda Tsuyoshi , Norimatsu Hideyuki , Bhuiyan M.M.H. , Ikegami Tomoaki , Ebihara Kenji
Published: April 2011

Carbon nanotube (CNT) is a promising material which has potential for applications to various nanotechnology devices owing to its unique features like high electrical conductivity, mechanical strength and large specific surface area. Recently, gas sensors using CNTs or carbon nano-fiber, which have extremely high sensitivity at a room temperature with fast response, have been reported. Being exposed to oxidizing gas like NO, NO2 or O3, the conductance of the single-walled carbon nanotubes (SWNTs) changes due to charge transfer between the SWNT surface and gas molecules adsorbed. Therefore CNTs will be applicable to O2 and O3 gas sensors in various fields.

CNTs thin film sensor was prepared and its performance was investigated. CNTs thin film was prepared on a SiN substrate using PLD/CVD method. To prepare a sensor device an Al2O3 substrate with Pt interdigital electrodes (sensor substrate) was used. In this method, Fe catalytic thin film was deposited by pulsed laser deposition (PLD) method using KrF excimer laser of wavelength 248 nm, repetition rate 10 Hz, energy fluence 3 J/cm2. During PLD process the substrate temperature and the ambient gas pressure were kept at room temperature of 25 °C and 3.5×10−5 Torr, respectively. The thickness and roughness of the films were modified by changing a number of ablation laser pulses from 300 to 3,000. A small number of laser pulses deposited Fe nano-particles of less than 10 nm in diameter on the substrate. We used 1000 pulses for a catalytic Fe film preparation as small-sized catalyst is necessary to grow SWNTs. CNTs were grown from Fe thin film on Si or sensor substrates by thermal CVD method. Ethylene gas was used as carbon source. The substrate was set in the quartz reaction tube heated to 1000 °C in an electric furnace. CNTs were grown for 20 ∼ 40 minutes. In our previous studies, it was found that SWNTs can grow under this process. The prepared CNTs were characterized using SEM, TEM and Raman spectroscopy. From SEM observation, randomly oriented CNTs were found on both the Si substrate and the sensor substrate. A diameter of CNTs was found 20 ∼ 50 nm which tended to be proportional to the size of catalyst particle.

The Sensitivity of CNT gas sensor was evaluated by measuring the electrical characteristic of the sensor. The sensor was exposed to NO gas of different concentration in a chamber. Resistance of the sensor was measured by two-terminal method, while the sensor was heated from room temperature to a high temperature on a block heater. The Sensitivity of CNT gas sensors, response time and reproducibility was measured. Initial resistance of the film was about 450 and it decreases with temperature increase. This shows that a prepared CNTs sensor film has semiconductor characteristics. Measured maximum sensitivity of CNTs gas sensor was 6.9 % at sensor temperature 290 deg. Detail studies and the latest data will be presented at the symposium.
Preparation of Titanium Oxide and Metal Titanates as Powders, Thin Films, and Microspheres by Novel Inorganic Sol-Gel Process
Authors: Deptuła A. , Goretta Kenneth C , Olczak Tadeusz , Lada Wieslawa , Chmielewski Andrzej G. , Jakubaszek U. , Sartowska Bozena , Alvani Carlo , Casadio Sergio , Contini Vittoria
Published: April 2011

Titanium oxide and titanates based on Ba, Sr and Ca were prepared from commercial solutions of TiCl4 and HNO3. The main preparation steps for the sols consisted of elimination of chloride anions by distillation with nitric acid and addition of metal hydroxides for the titanates. Resulting sols were gelled and used to (1) prepare irregularly shaped powders by evaporation; (2) produce by a dipping technique thin films on glass, Ag, or Ti substrates; and (3) produce spherical powders (diameters <100 μm) by solvent extraction. Results of thermal and X-ray-diffraction analyses indicated that the temperatures required to form the various compounds were lower than those necessary to form the compounds by conventional solid-state reactions and comparable to those required with use of organometallic based sol-gel methods. Temperatures of formation could be further reduced by addition of ascorbic acid to the sols.
Ultrafast Pd/AAO Nanowell Hydrogen Sensor
Authors: Lu Jianjiang , Yu Shufang , Wang H.Hau
Published: April 2011

Anodized aluminum oxide (AAO) membranes consist of highly uniform and aligned nanopores with pore diameters ranging between 10 and 200 nm. Based on these nanoporous materials, we developed a new AAO nanowell structure that was synthesized through short-term anodization of aluminum foil. The nanowell structure was made of shallow wells that were oriented in a hexagonally closed packed configuration with well diameter around 50 nm and depth less than 100 nm. The chemical composition was amorphous alumina on aluminum substrate. Thin palladium film was then fabricated on the surface of the as-synthesized AAO nanowell to prepare a Pd/AAO nanowell structure. These devices demonstrated unexpectedly high hydrogen sensitivity. The response time ranged from a few hundred milliseconds to a few seconds with hydrogen concentration between 1 and 0.05%. They also showed modest responses at hydrogen concentration as low as 5 ppm.
Characterization of Lead Zirconate Titanate Powders Prepared by a Hydrothermal Method
Authors: Che Lingjuan , Ding Yongping , Cheng Jinrong , Chen Chao , Meng Zhongyan
Published: April 2011

Lead Zirconate Titanate (PZT) powders have been synthesized by a hydrothermal method at the processing temperatures of 120-220 °C for 1.5-50 hours, based on the reaction of Pb(CH3COOH)2·3H2O, ZrOCl2·8H2O, Ti(C4H9O)4 and KOH. Hydrothermally treated PZT powders were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transformation infrared (FTIR) techniques respectively. The influences of hydrothermal synthesize conditions on the crystalline structure and the morphology of PZT particles were investigated. Crystallized PZT powders could be synthesized at the KOH concentration of >2.5 mol/l.
High Carrier Lifetime Bulk-Grown 4H-SiC Substrates for Power Applications
Authors: Malta David , Jenny J.R. , Tsvetkov V.F. , Das M. , Müller St. G. , Hobgood H. McD. , Carter C.H. , Kumar R.J. , Borrego J.M. , Gutmann R.J.
Published: April 2011

A thermal anneal process has been developed that significantly enhances minority carrier lifetime (MCL) in bulk-grown substrates. Microwave photoconductivity decay (MPCD) measurements on bulk grown substrates subjected to this process have exhibited decay times in excess of 35 μs. Electron Beam Induced Current (EBIC) measurements indicated a minority carrier diffusion length (MCDL) of 65 μm resulting in a calculated MCL of 15 μs, well within the range of that measured by MPCD. Deep level transient spectroscopic (DLTS) analysis of samples subjected to this anneal process indicated that a significant reduction of deep level defects, particularly Z1/2, may account for the significantly enhanced lifetimes. The enhanced lifetime is coincident with a transformation of the original as-grown crystal into a strained or disordered lattice configuration as a result of the high temperature anneal process. PiN diodes were fabricated employing 350 μm thick bulk-grown substrates as the intrinsic drift region and thin p- and n-type epitaxial layers on either face of the substrate to act as the anode and cathode, respectively. Conductivity modulation was achieved in these diodes with a 10x effective carrier concentration increase over the background doping as extracted from the differential on-resistance. Significant stacking fault generation observed during forward operation served as additional evidence of conductivity modulation and underscores the importance of reducing dislocation densities in substrates in order to produce a viable bulk-grown drift layer.