bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling the fs Demagnetization: Laser-Induced Reversal in an Applied Magnetic Field
Authors: Longa Francesco Dalla , Boesten Dion , Kicken Harm H.J.E. , de Jonge Wim J.M. , Koopmans Bert 
Published: April 2011

ABSTRACTA novel model for ultrafast laser-induced magnetization dynamics is analyzed. Equilibration of the magnetic system is described by including electron-phonon scattering events with a finite spin flip probability. Recently, we demonstrated that such a model predicts a direct relation between the demagnetization time and the Gilbert damping. Here we present numerical simulations based on the same Hamiltonian, but including the presence of an external applied field. Thereby, reversal of the magnetization after heating above the Curie temperature (Tc) can be modeled. We demonstrate that magnetization reversal can be achieved even if the lattice temperature stays below Tc.
Metal-insulator Transition and Magnetic Domains in (Ga,Mn)As Epilayers
Authors: Dourlat Alexandre , Gourdon Catherine , Jeudy Vincent , Bernardot Frédéric , Testelin Christophe , Lacaze Emmanuelle , Thevenard Laura , Mauguin Olivia , Largeau Ludovic , Patriarche Gilles , Lemaître Aristide 
Published: April 2011

ABSTRACTWe investigate the magnetic domain pattern in (Ga,Mn)As epilayers with perpendicular magnetic anisotropy. We show that post-growth annealing, besides improving the magnetic and transport properties, also drastically changes the domain pattern. Strong pinning of domain walls along the <110> directions is suppressed and large-size domains are observed.
Above Room-Temperature Ferromagnetism in GaN Powders by Calcinations with CuO
Authors: Noice Lori , Seipel Bjoern , Erni Rolf , Gupta Amita , Li Chunfei , Moeck peter , Rao Venkat , Browning Nigel 
Published: April 2011

ABSTRACTGallium nitride powders were calcined with copper oxide in either air or N2 and analyzed by means of powder X-ray diffraction (XRD), high-resolution parallel illumination (HRTEM) and scanning probe transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDXS), and electron energy loss spectroscopy (EELS) in order to address the structural and electronic effects of Cu-incorporation into GaN. Gallium oxide and multiple copper oxide phases corresponding to the calcination environment were detected. Significant changes in the lattice parameters and electronic structure of the N2-processed GaN indicate incorporation of both copper and oxygen into the GaN lattice as well as changes in the chemical bonding due to the calcinations process. SQUID magnetometer measurements at 300 K demonstrated ferromagnetism in selected samples.
Nanoscale Indentation of Polymer and Composite Particles by Atomic Force Microscopy
Authors: Armini Silvia , Vakarelski Ivan U. , Whelan Caroline M. , Maex Karen , Higashitani Ko 
Published: April 2011

ABSTRACTAtomic Force Microscopy (AFM) was employed to probe the mechanical properties of surface-charged polymethylmethacrylate (PMMA)-based terpolymer and a composite terpolymer core-silica shell nanosphere in air and water media. Since these materials exhibit enhanced mechanical properties, such as toughness and elasticity, and enhanced chemical stability, they are particularly interesting for potential applications in reducing defectivity during the process of Chemical Mechanical Planarization. The polymer particles were subjected to a thermal treatment aimed at improving their mechanical properties in terms of hardness (H) and elastic modulus (E). By analysis of force-displacement curves and on the basis of Hertz's theory of contact mechanics, Young's moduli were measured for the terpolymer compared with the composite that has expected mechanical property enhancement due to its silica shell. In air, E increases from 4.3 GPa to 6.6 GPa for the treated terpolymer compared with the respective value of 10.3 GPa measured for the composite. In water, E increases from 1.6 GPa to 4.5 GPa for the thermally treated terpolymer that is comparable with the respective value of 3.6 GPa measured for the composite. This observation suggests that as an alternative to the creation of polymer-silica composite nanoparticles for CMP, comparable mechanical properties can be achieved by a simple heat treatment step.
Interaction Forces Between Thermoresponsive Surface and Colloidal Particle in Aqueous Solution Studied Using Atomic Force Microscopy
Authors: Ishida Naoyuki , Kobayashi Mikio 
Published: April 2011

ABSTRACTThe interaction forces between poly(N-isopropylacrylamide) (PNIPAAm)-grafted surfaces and colloidal particles in an aqueous solution were investigated using an atomic force microscope (AFM). Measurements were conducted between a smooth silicon wafer on which PNIPAAm was terminally grafted and silica particles hydrophobized with a silanating reagent in an aqueous electrolyte solution under controlled temperature. Below the lower critical solution temperature (LCST) of PNIPAAm, there were large repulsive forces between the surfaces, while attractive forces were observed above LCST. When surface hydrophobicity of the particles increased, the magnitude of attractive force tended to increase. The changes of hydration state of the grafted PNIPAAm chains depending on temperature is considered to greatly alter the interaction force properties. The role of the intermolecular interaction between the PNIPAAm chains and the hydrophobic particles in the interaction forces is discussed.
A Novel Approach for the Preparation of InP Nanocrystals
Authors: Sun Zhaoyong , Zhang Jun , Zhang Ming , Fang Jiye 
Published: April 2011

ABSTRACTIII-V semiconductor nanocrystals are of considerable interest due to their extensive applications in the optoelectronic and biomedical fields. In order to meet the practical use, the convenient and scalable production of III-V narrow-disperse nanocrystals is inspiring. We report an efficient and rapid method of preparing highly monodisperse InP nanocrystals using a wet-chemical redox synthetic approach with a noncoordinating solvent, employing organic reducing agent LiBH(CH2CH3)3 and yellow phosphor. As advantages of this approach, reaction temperature is relatively low (80°C-120°C) and reaction time is less than 2 hours. Our characterization shows that the photoluminescence properties of InP nanocrystals are highly dependent on the particle size.
On the Structural and Optical Properties of ZnO Nanoparticles Formed in Silica by Ion Implantation
Authors: Tagliente Maria Antonella , Massaro Marcello , Mattei Giovanni , Mazzoldi Paolo , Pellegrini Giovanni , Bello Valentina , Carbone Daniela 
Published: April 2011

ABSTRACTZinc Oxide (ZnO) is a II-VI semiconductor material with a wide direct band-gap of 3.37 eV at room temperature (RT). In the past decades, the material has been used for a variety of applications such as gas sensors, surface acoustic wave devices, or transparent contacts. Recently, ZnO has gained a new substantial interest primarily because to its potentialities for optoelectronic and spintronic applications. The renewed interest has been fueled by the availability of high-quality bulk substrates, reports of p-type conduction and theoretical predictions of its ferromagnetic behavior at room temperature when doped with transition metals. In the domain of optoelectronics, its main applications include devices emitting in the blue and UV regions by exploiting its wide band-gap such as light-emitting and laser diodes. With respect to several wide band-gap semiconductor materials, ZnO has the advantage of a larger exciton binding energy (about 60 meV) which paves the way for an intense near-band-edge excitonic emission at room and higher temperatures. On the other hand, a band gap engineering can be also achieved by the incorporation of Cadmium and Magnesium atoms into the ZnO lattice.Many techniques have been used to prepare ZnO in various forms, such as single crystals, powders and films. In the past few years, the great attention toward materials with nanometric size have motivated a number of studies on the synthesis of ZnO nanocrystals. Ion implantation is one of the most effective and versatile technique to obtain nanoparticles. ZnO particles embedded in silica matrix have been successfully prepared by ion implantation followed by thermal oxidation.In this work, we report on a detailed structural and optical characterization of the ZnO-silica nanocomposites by using several complementary techniques; in particular, Glancing Incidence X-ray Diffraction (GIXRD), Rutherford Backscattering Spectrometry (RBS), linear Optical Absorption (OA) in the UV-near IR spectrum and Photo-Luminescence (PL). The ZnO nanoparticles embedded in SiO2matrix were prepared by implanting the substrates with 130 keV Zn+ions at doses of 1, 1.5 and 2´1017 ions/cm2. Subsequently, the implanted samples were annealed for 1h in a furnace at a temperature between 500 and 800°C under flowing O2 gas. X-ray diffraction results indicate the formation of Zn and ZnO nanoparticles in the as-implanted and annealed samples, respectively. Moreover, the ZnO nanocrystals embedded in the SiO2matrix have a (002) preferred orientation. After the oxidation, the optical absorption spectra show an absorption edge at about 374 nm by confirming the presence of the ZnO particles. A relatively strong exciton photoluminescence peak was observed at room temperature under pulsed N2 laser excitation at l=337nm. The results obtained, peculiarly related to the implantation doses and annealing temperature, are discussed.
Patterning of Cell Attachment to Biocompatible Glassy Polymeric Carbon by Silver Ion Implantation
Authors: Zimmerman Robert Lee , Gurhan Ismet , Ila Daryush , Ozdal-Kurt F. , Sen B. H. , Rodrigues M. 
Published: April 2011

ABSTRACTAlthough Glassy Polymeric Carbon (GPC) is ideally suited for implants in the blood stream, tissue that normally forms around the moving parts of a GPC heart valve. There is concern that the tissue lose adhesion and create the condition for embolisms downstream. We have shown that silver ion implantation or argon ion assisted surface deposition of silver inhibits cell growth on GPC, a desirable improvement of current cardiac implants. In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that near surface implantation of silver in GPC can completely inhibit cell attachment on implanted areas while leaving adjacent areas unaffected. Patterned ion implantation permits precise control of tissue growth on medical applications of GPC.
Design and Synthesis of a Multifunctional Probe for Bio-Imaging and Therapeutics
Authors: Liu Yu-San , Liang Chi Hui , Vernier P. Thomas , Sun Yinghua , Gundersen Martin A. 
Published: April 2011

ABSTRACTWe report the synthesis of CdSe/ZnSe/ZnS (core/shell/shell) quantum dots (QDs) as a fluorescence probe for biological cells, and their functionalization with carbon nanotube (CNT)-retrovirus complexes (labeled with the QDs) to form multi-functional tool with potential applications for cancer therapeutics. A mild method for preparing this QD-CNT-retrovirus complex, which preserves viral function, is reported. Observations and imaging under fluorescence confocal microscope show the expression of enhanced green fluorescent protein (EGFP) gene and QD uptake in viable cells, indicating that this novel probe is able to enter cells, crossing the natural barrier of the cell membranes. Such multi-functional probes have potential as medical diagnostics and for therapeutics for diseases including cancer. The multifunctional probe is of interest for potentially broad applications – with the quantum dots as the visualization aid, carbon nanotubes as an efficient opto-thermo converter for selective extermination of cells with the help of light irradiation at near-IR range, and the retrovirus as a vehicle for genetic therapy.
Microhydraulic Actuation Using Biological Ion Transporters Reconstituted on Artificial BLM
Authors: Sundaresan Vishnu Baba , Leo Donald J 
Published: April 2011

ABSTRACTPlants and animals have the natural ability to exhibit force through controlled pressurization of cellular compartments. The mechanism through which force is generated is powered by biological fuels. The process involves moving ions against an established concentration gradient expending free energy from bio-fuels like Adenosine-tri-phosphate (ATP), kinesin etc., Materials exhibiting deformation using biological processes are called Nastic materials. The functional component in mass transfer across the cell boundary is the ion transporter embedded in cell membranes. The ion transporters which are complex protein molecules, move ions and water molecules for an applied chemical or electrical stimulus. The bio-inspired microhydraulic actuator uses the same functional component in plant cells reconstituted on a planar bilayer lipid membrane (BLM) formed from purified lipids. The protein transporters pump ions and fluid into an enclosed cavity to cause deformation. The controlled fluid transport through AtSUT4(proton-sucrose co-transporter extracted from Arabidopsis thaliana) reconstituted on a 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine (POPE) BLM on porous lead silicate glass plate driven by a proton gradient demonstrated the ability to move fluid across the membrane. This article discusses a prototype microhydraulic actuator that increases in thickness for an applied pH and sucrose concentration gradient.
Observation of Leggett's Mode in Mg1-xAlxB2
Authors: Ponomarev Yaroslav , Kuzmichev Svetoslav , Mikheev Mikhail , Sudakova Marina , Tchesnokov Sergei , Bulychev Boris , Maksimov Evgenii , Krasnosvobodtsev Sergei 
Published: April 2011

ABSTRACTA detailed investigation of multiband superconductivity and Leggett's collective mode in the Mg1-xAlxB2 system was carried out using tunneling and Andreev spectroscopy
Electrical Devices Obtained From Polymeric Precursors Process
Authors: Carvalho Claudio Luiz , Peruzzi Raphael Otavio , Solano Rudi A. V. 
Published: April 2011

ABSTRACTNowadays, many investments have been made in the area of superconductor materials, with the aim to improve theirs potential technological applications. Applications on the energy transport using cables, to get high resolution images in the medicine use high magnetic fields, high speed signals use superconductor devices all of them are in crescent evidence and they are showing that the future is coming and next for this new kind of materials. Obviously that everything of this is possible due to the increasing of research with new materials, where the synthesis, characterization and applications are of the mainly objective of these researches. The production of cable for the energy transport has been in advanced stage as the bulks production is too. However, the film production that to aim at the electronic devices area are not so developed or its still need expensive investments. Thinking about that, we are developing a research where we may increase the relation of cost/benefits. Thereby, we are applying the polymeric precursors method to obtain films that will be used in the built of electronic devices. Thin films (mono and multilayers, on crystalline or metallic substrates, controlled thickness) of the BSCCO system have been obtained from dip coating deposition process with excellent results in terms of preferential orientation, controlled thickness, large area, what may indicate future applications.Based on these results, we present an electrical circuit and their principal characteristics as superconductor transition (85K), transport current density and structure. DC four probes method, scanning electron microscopy, digital optical microscopy, X-ray diffractometry were some techniques used for the characterization of this superconductor electric device.
Investigation of In-Field Properties of YBCO Film with Artificial Pinning Centers
Authors: Kobayashi Hiroyoshi , Ishida Satoru , Takahashi Kazuhiro , Konishi Masaya , Ibi Akira , Miyata Seiki , Yamada Yutaka , Shiohara Yuh , Kato Takeharu , Hirayama Tsukasa 
Published: April 2011

ABSTRACTWe have investigated the thickness dependence of critical current for YBa2Cu3O7-x (YBCO) film with artificial pinning centers on metallic substrate. Artificial pinning centers were introduced by the pulsed laser deposition (PLD) using YBCO target including YSZ particles. The film over 1 μm in thickness exhibited with high critical current (Ic) of 40.7A in applied magnetic field of 3T parallel to the c-axis at 77K. This value was 5 times as high as the normal YBCO film without artificial pinning centers. The large Ic enabled us to approach to a practical application in the near future. Furthermore, it was clarified that the columnar nano-structure formed in the film, we call “the bamboo structure”, was a dominant pinning center because each Jc-&#952; curve of all thick films formed a universal line by the normalization of Jc. In addition, it was also found that YSZ addition has an optimal concentration for pinning by the study of YSZ concentration in the film.
Pr Doped YBCO Films Produced by Pulsed Laser Deposition
Authors: Harrison B. Craig , Kell Joseph W. , Barnes Paul N. , Haugan Timothy J. , Varanasi Chakrapani V. , Rane Manisha V. , Ramos Frank , Maartense Iman 
Published: April 2011

ABSTRACTPr doped YBa2Cu3O7-d targets with composition Y1-xPrxBa2Cu3O7-d where × = 0.0001, 0.001, 0.01, and 0.1 were prepared from oxide powders and were used to deposit thin films by pulsed laser deposition using conditions previously optimized for pure YBa2Cu3O7-d. The Pr dopant was found to be dispersed throughout the film by secondary ion mass spectrometry and found to have an increased density of nanoparticles on the surface. The pinning force of the doped samples was found to decrease with increasing concentration of Pr; however, at 0.01% concentration the doped film displayed a significant enhancement over pure YBa2Cu3O7-d for nearly the full range of 0 – 9 T.
Density Fluctuation in Coulombic Colloid Dispersion: Self-Assembly of Lipid A-Phosphates
Authors: Paradies Henrich H. , Faunce Chester A. 
Published: April 2011

ABSTRACTDilute electrostatically–Vstabilized aqueous solutions of hexa-acylated (C14)lipid A-diphosphatefromEscherichia coliwere prepared with low polydispersities in shape, size and charge. A high degree of ordering was exhibited for volume fractions between Φ ≅ 1.5 × 10−4and 3.5 × 10−4. The structure factor S(Q) was strongly dependent on the particle number density, the nature of ions, e.g. Ca2+, Mg2+, K+, Na+and H+, the effective colloidal charge (Z*), and the Debye screening length,k. The magnitude and position of the S(Q) peaks vary not only with counterions, e.g. Ca2+or Mg2+, and concentration (nM to μM), but also with the order of their addition to thelipid A-dispersions. Different types of colloidal-crystal structures were obtained for Φ ≅ 3.5 × 10−4. The Ca2+and K+salts exhibited FCC type-lattices with a = 56.3 nm and 55.9 nm, whereas the Na+and Mg2+salts oflipid A-diphosphateformed BCC type-lattices with a = 41.5 nm and 45.5 nm, respectively.
Scaling Properties of two-dimensional Star-branched Polymers grown by Diffusion
Authors: Ramirez-Santiago Guillermo , Mendoza Carlos I. 
Published: April 2011

ABSTRACTWe present an off-lattice numerical algorithm based upon pure diffusion to construct two-dimensional star-branched polymers with one, three, six and twelve branches. We built up structures with a total of up to 30,000 monomer units. For each one of them averages over one hundred independent configurations were taken. From a finite size analysis the scaling properties of the pair correlation function as well as the radius of gyration were obtained. Our findings indicate that the fractal dimension of the structures are: df=1.21 (0.03) for a linear polymer, df==1.21(0.02), for three branches, df==1.23 (0.02) for six branches and df=1.26 (0.03) for twelve branches.
Electric Field Guided Self-Assembly of Molecules
Authors: Lu Wei , Salac David 
Published: April 2011

ABSTRACTAdsorbate molecules usually carry electric dipole moments, and the magnitude can be engineered by adding polar groups. This paper investigates the dynamic domain pattern formation of multilayer dipolar molecules on a substrate under the guidance of external electric fields. The simulations reveal self-alignment, pattern conformation and the reduction of feature size in multilayer systems. A novel approach of transporting molecules on a substrate surface by reconfigurable molecular vehicles and embedded electrodes is proposed.
Switching of Water Flow Through Stimuli-responsive Hydrogels
Authors: Suzuki Atsushi , Kondo Go 
Published: April 2011

ABSTRACTThe friction between the polymer network and the solvent water was measured by a newly designed simple apparatus where the hydrogel was mechanically constrained in a glass microcapillary. The water-flow through the hydrogel could be continuously controlled by more than ten times only by adjusting the temperature in the vicinity of the transition temperature (around the human body temperature). The concentration of polymer network and cross-linker as well as the inhomogeneity of polymer networks introduced at gelation was found to determine the overall flow velocity and the amount of change during the phase transition could be controlled by the temperature change. The principle to control the solvent flow will be discussed on the basis of the material parameters and the experimental conditions.
A Novel Associative Polymer Network based on Cyclodextrin Inclusion with Tunable Rheological Properties
Authors: Fu Lin , Guo Xuhong , Lincoln Stephen , Prud'homme Robert K. 
Published: April 2011

ABSTRACTA novel associative polymer network with tunable rheological properties is developed based on cyclodextrin-hydrophobe inclusion. The network is formed from mixtures of two polyacrylic acid (PAA) backbone polymers, one with pendant cyclodextrin groups and one with pendant hydrophobic alkyl groups. The lifetime of the cyclodextrin-hydrophobe inclusion can be well controlled by the length of alkyl chains inserted into the cyclodextrins; also, the binary nature of cyclodextrin-hydrophobe inclusion prevents hydrophobes from forming non-stoichiometric multiple associations. This system can serve as a model associative polymer network to test associative polymers theories. Dynamic rheological properties of this mixture solution can be tuned by adding free cyclodextrins or sodium dodecylsulfate (SDS) to displace polymer to polymer associations. Dynamic moduli change three orders of magnitude from a gel state to a sol state. This polyelectrolyte system is also pH sensitive, salt sensitive and temperature sensitive. The phase behavior of this mixture solution is experimentally studied by light scattering measurements and rheology. The thermodynamics of the cyclodextrin-hydrophobe interaction is independently studied using isothermal titration calorimetry and surface plasmon resonance study.