bluuebunny/crossref_metadata_2025 huggingface dataset:
Rainfall‐runoff model calibration using informal likelihood measures within a Markov chain Monte Carlo sampling scheme
Authors: McMillan Hilary , Clark Martyn
Published: April 2009

This paper considers the calibration of a distributed rainfall‐runoff model in a catchment where heterogeneous geology leads to a difficult and high‐dimensional calibration problem and where the response surface has multiple optima and strong parameter interactions. These characteristics render the problem unsuitable for solution by uniform Monte Carlo sampling and require a more targeted sampling strategy. MCMC methods, using the SCEM‐UA algorithm, are trialed using both formal and informal likelihood measures. Each method is assessed in its success at predicting the catchment flow response and capturing the total uncertainty associated with this prediction. The comparison is made at both the catchment outlet and at internal catchment locations with distinct geological characteristics. Informal likelihoods are found to provide a more complete exploration of the behavioral regions of the response space and hence more accurate estimation of total uncertainty. Last, we demonstrate how information gained from the investigation of the response space, in conjunction with qualitative knowledge of system behavior, can be used to constrain the Markov chain trajectory.
Fast thermospheric wind jet at the Earth's dip equator
Authors: Liu Huixin , Watanabe Shigeto , Kondo Tsutomu
Published: April 2009

The thermospheric zonal wind forms a fast wind jet at the Earth's dip equator instead of the geographic equator. This remarkable feature is revealed in two sets of independent observations made two decades apart. One is from the CHAMP satellite during the year of 2002 and the other is from the DE‐2 satellite during Aug. 1981–Feb. 1983. Both observations show that this wind jet is eastward at night with speed reaching 150 ms−1, and westward around noon with speed over 75 ms−1. These fast wind jets are observed during local times of fully developed equatorial ionization anomaly (EIA). On the other hand, a channel of slow wind is found on the dip equator during the period of 05–08 MLT, which corresponds to local times before the EIA develops. These features strongly suggest the ion drag being the principle cause for shifting the wind jet from the geographic equator to the dip equator.
Development of prophylactic and therapeutic vaccines using the ISCOMATRIX adjuvant
Authors: Maraskovsky Eugene , Schnurr Max , Wilson Nick S , Robson Neil C , Boyle Jeff , Drane Debbie
Published: April 2009

Adjuvants are components that when added to subunit antigen (Ag) vaccines boost their immunogenicity and thus immune efficacy. However, there are few adjuvants that are approved for clinical use resulting in a critical need for the development of safe and effective adjuvants for use in both prophylactic and therapeutic vaccines. The paucity of appropriate adjuvants is more chronic for the development of therapeutic vaccines for cancer and chronic infectious disease, which need to induce cytotoxic T‐cell responses via cross‐presentation of the vaccine Ag by dendritic cells. The ISCOMATRIX adjuvant represents a unique adjuvant system that facilitates Ag delivery and presentation as well as immunomodulation to provide enhanced and accelerated immune responses. The immune responses generated are of broad specificity to the vaccine Ag, and include robust antibody responses of multiple subclasses as well as both CD4+ and CD8+ T‐cell responses. Here we discuss our understanding of the mechanisms of action by which ISCOMATRIX adjuvant may facilitate these integrated immune responses and touch on insights gained through its clinical experience.
SOCS1 negatively regulates the production of Foxp3+ CD4+ T cells in the thymus
Authors: Zhan Yifan , Davey Gayle M , Graham Kate L , Kiu Hiu , Dudek Nadine L , Kay Thomas WH , Lew Andrew M
Published: April 2009

SOCS1 profoundly influences the development and peripheral homeostasis of CD8+ T cells but has less impact on CD4+ T cells. Despite the moderate influence of SOCS1 in the development of the total CD4 T‐cell lineage, we show here that SOCS1 deficiency resulted in a 10‐fold increase in Foxp3+ CD4+ T cells in the thymus. Increased numbers of Foxp3+ thymocytes occurred in mice with T‐cell‐specific ablation of SOCS1, suggesting that the effect is T‐cell intrinsic. This increase in Foxp3+ CD4+cells in SOCS1‐deficient mice also occurred in the absence of IFN‐γ or/and IL‐7 signaling. Increase in CD25+CD4+ T cells in the absence of SOCS1 could be partly due to enhanced survival by CD25+CD4+cells, to a lesser degree CD25−CD4+ T cells, from SOCS1‐deficient mice with or without T‐cell growth factors.
The future of annotation/biocuration
Authors: Bairoch Amos
Published: April 2009

Talk given at 3rd International Biocuration Conference. Berlin 2009
GenColors: Annotation and comparative genomics made easy
Authors: Felder Marius , Romualdi Alessandro , Gloeckner Gernot , Platzer Matthias , Suehnel Juergen
Published: April 2009

GenColors is a web-based software/database system initially aimed at an improved and accelerated annotation of prokaryotic genomes making extensive use of genome comparison (Romualdi et al., Bioinformatics 2005; Romualdi et al., Methods Mol. Biol. 2007). It offers a seamless integration of data from ongoing sequencing projects and annotated genomic sequences obtained from GenBank. With GenColors dedicated genome browsers containing a group of related genomes can be easily set up and maintained. The tool has been efficiently used for sequenceing and annotating the Borrelia garinii genome and is currently applied to a number of other ongoing genome projects on Legionella, Pseudomonas and E. coli genomes. Examples for freely accessible GenColors-based dedicated genome browsers are the Spirochetes Genome Browser SGB ("sgb.fli-leibniz.de":http://sgb.fli-leibniz.de), the Photogenome Browser CGB ("cgb.fli-leibniz.de":http://cgb.fli-leibniz.de) and the Enterobacter Genome Browser ENGENE ("engene.fli-leibniz.de":http://engene.fli-leibniz.de). The system has now been adapted to handle also eukaryotic genomes. A first application of this feature is the annotation and analysis of two fungal species (unpublished). Another GenColors-based tool is the Jena Prokaryotic Genome Viewer - JPGV ("jpgv.fli-leibniz.de":http://jpgv.fli-leibniz.de). Contrary to the dedicated browsers it offers information on almost all finished bacterial genomes. Currently, it includes 1140 genomic elements of 293 species.
Community curation on WikiPathways: How we assist knowledge collection
Authors: Evelo Chris
Published: April 2009

Biologists typically use knowledge represented as pathways to better understand the results of genomics experiments. Through integration of data from different omics techniques with what we already know, statistical evaluation and subsequent data visualization the results often start to make sense. An important problem is that we often do not have the relevant pathways, or they may be incomplete or not suitable for usage by analytical tools. Wikipathways is meant to be an answer to the problems described above. It uses mediawiki technology and dedicated open source java code to allow biologists to edit pathway content on the web. We assist this process through the development of helpful software like a Diff tool, Go and KEGG converters, portal mechanism, webservice and pathway extension through automated suggestions.
Does Language Influence the Accuracy of Judgments of Stuttering in Children?
Authors: Einarsdóttir Jóhanna , Ingham Roger J.
Published: April 2009

Purpose

To determine whether stuttering judgment accuracy is influenced by familiarity with the stuttering speaker’s language.

Method

Audiovisual 7-min speech samples from nine 3- to 5-year-olds were used. Icelandic children who stutter (CWS), preselected for different levels of stuttering, were subdivided into 5-s intervals. Ten experienced Icelandic speech-language pathologists (ICE-SLPs) and 10 experienced U.S. speech-language pathologists (US-SLPs), the latter being unfamiliar with the Icelandic language, independently judged each 5-s interval (
n
= 756) as
stuttered
or
nonstuttered
on 2 separate occasions.

Results

As in previous studies, intervals judged to contain stuttering showed wide variability within the ICE-SLP and US-SLP groups. However, both SLP groups (a) displayed satisfactory mean intrajudge agreement, (b) met an independent stuttering judgment accuracy criterion test using English-speaking CWS samples, and (c) met an agreement criterion on approximately 90% of their stuttering and nonstuttering judgments on the Icelandic-speaking CWS samples.

Conclusion

Experienced SLPs were shown to be highly accurate in recognizing stuttering and nonstuttering exemplars from young CWS speaking in an unfamiliar language. The findings suggest that judgments of occurrences of stuttering in CWS are not generally language dependent, although some exceptions were noted.
Perceptual Consequences of Changes in Vocoded Speech Parameters in Various Reverberation Conditions
Authors: Drgas Szymon , Blaszak Magdalena A.
Published: April 2009

Purpose

To study the perceptual consequences of changes in parameters of vocoded speech in various reverberation conditions.

Method

The 3 controlled variables were number of vocoder bands, instantaneous frequency change rate, and reverberation conditions. The effects were quantified in terms of (a) nonsense words' recognition scores for young normal-hearing listeners, (b) ease of listening based on the time of response (response delay), and (c) the subjective measure of difficulty (10-degree scale).

Results

It has been shown that the fine structure of a signal is a relevant cue in speech perception in reverberation conditions. The results obtained for different number of bands, frequency-modulation cutoff frequencies, and reverberation conditions have shown that all these parameters are important for speech perception in reverberation.

Conclusions

Only slow variations in the instantaneous frequency (<50 Hz) seem to play a critical role in speech intelligibility in anechoic conditions. In reverberant enclosures, however, fast fluctuations of instantaneous frequency are also significant.
Objective Measures of Listening Effort: Effects of Background Noise and Noise Reduction
Authors: Sarampalis Anastasios , Kalluri Sridhar , Edwards Brent , Hafter Ervin
Published: April 2009

Purpose

This work is aimed at addressing a seeming contradiction related to the use of noise-reduction (NR) algorithms in hearing aids. The problem is that although some listeners claim a subjective improvement from NR, it has not been shown to improve speech intelligibility, often even making it worse.

Method

To address this, the hypothesis tested here is that the positive effects of NR might be to reduce cognitive effort directed toward speech reception, making it available for other tasks. Normal-hearing individuals participated in 2 dual-task experiments, in which 1 task was to report sentences or words in noise set to various signal-to-noise ratios. Secondary tasks involved either holding words in short-term memory or responding in a complex visual reaction-time task.

Results

At low values of signal-to-noise ratio, although NR had no positive effect on speech reception thresholds, it led to better performance on the word-memory task and quicker responses in visual reaction times.

Conclusions

Results from both dual tasks support the hypothesis that NR reduces listening effort and frees up cognitive resources for other tasks. Future hearing aid research should incorporate objective measurements of cognitive benefits.
Defining Spoken Language Benchmarks and Selecting Measures of Expressive Language Development for Young Children With Autism Spectrum Disorders
Authors: Tager-Flusberg Helen , Rogers Sally , Cooper Judith , Landa Rebecca , Lord Catherine , Paul Rhea , Rice Mabel , Stoel-Gammon Carol , Wetherby Amy , Yoder Paul
Published: April 2009

Purpose

The aims of this article are twofold: (a) to offer a set of recommended measures that can be used for evaluating the efficacy of interventions that target spoken language acquisition as part of treatment research studies or for use in applied settings and (b) to propose and define a common terminology for describing levels of spoken language ability in the expressive modality and to set benchmarks for determining a child’s language level in order to establish a framework for comparing outcomes across intervention studies.

Method

The National Institute on Deafness and Other Communication Disorders assembled a group of researchers with interests and experience in the study of language development and disorders in young children with autism spectrum disorders. The group worked for 18 months through a series of conference calls and correspondence, culminating in a meeting held in December 2007 to achieve consensus on these aims.

Results

The authors recommend moving away from using the term
functional speech,
replacing it with a developmental framework. Rather, they recommend multiple sources of information to define language phases, including natural language samples, parent report, and standardized measures. They also provide guidelines and objective criteria for defining children’s spoken language expression in three major phases that correspond to developmental levels between 12 and 48 months of age.
Interaction and response of a smectic-A liquid crystal to a nanometer particle: Phase transition due to the combined effect of the functionalization compound and particle size
Authors: Martínez-Miranda L. J. , Kurihara Lynn K.
Published: April 2009

The interaction of nanometer particles with organic materials is important because of their increased use in many applications and their potential use in biosystems. We found that liquid crystals respond to nanometer particles differently depending on the surface functionalization of the nanoparticles using x rays and developed a phenomenological model to explain the differences that we observed. We found from the analysis of the peaks close to 0.199 Å−1 that the inverse integrated intensity serves as a measure of how well the liquid crystal has reoriented and compared the graph obtained from the phenomenological theory to the graph obtained with the inverse integrated intensity. An analysis of the widths of these peaks (inverse correlation length) shows that the reorientation under the magnetic field can lead to a phase transition of the portion of the liquid crystal that is reorienting.
Structure and phase diagram of an adhesive colloidal dispersion under high pressure: A small angle neutron scattering, diffusing wave spectroscopy, and light scattering study
Authors: Vavrin R. , Kohlbrecher J. , Wilk A. , Ratajczyk M. , Lettinga M. P. , Buitenhuis J. , Meier G.
Published: April 2009

We have applied small angle neutron scattering (SANS), diffusing wave spectroscopy (DWS), and dynamic light scattering (DLS) to investigate the phase diagram of a sterically stabilized colloidal system consisting of octadecyl grafted silica particles dispersed in toluene. This system is known to exhibit gas-liquid phase separation and percolation, depending on temperature T, pressure P, and concentration φ. We have determined by DLS the pressure dependence of the coexistence temperature and the spinodal temperature to be dP/dT=77 bar/K. The gel line or percolation limit was measured by DWS under high pressure using the condition that the system became nonergodic when crossing it and we determined the coexistence line at higher volume fractions from the DWS limit of turbid samples. From SANS measurements we determined the stickiness parameter τB(P,T,φ) of the Baxter model, characterizing a polydisperse adhesive hard sphere, using a global fit routine on all curves in the homogenous regime at various temperatures, pressures, and concentrations. The phase coexistence and percolation line as predicted from τB(P,T,φ) correspond with the determinations by DWS and were used to construct an experimental phase diagram for a polydisperse sticky hard sphere model system. A comparison with theory shows good agreement especially concerning the predictions for the percolation threshold. From the analysis of the forward scattering we find a critical scaling law for the susceptibility corresponding to mean field behavior. This finding is also supported by the critical scaling properties of the collective diffusion.
Matched wideband low-noise amplifiers for radio astronomy
Authors: Weinreb S. , Bardin J. , Mani H. , Jones G.
Published: April 2009

Two packaged low noise amplifiers for the 0.3–4 GHz frequency range are described. The amplifiers can be operated at temperatures of 300–4 K and achieve noise temperatures in the 5 K range (<0.1 dB noise figure) at 15 K physical temperature. One amplifier utilizes commercially available, plastic-packaged SiGe transistors for first and second stages; the second amplifier is identical except it utilizes an experimental chip transistor as the first stage. Both amplifiers use resistive feedback to provide input reflection coefficient S11<−10 dB over a decade bandwidth with gain over 30 dB. The amplifiers can be used as rf amplifiers in very low noise radio astronomy systems or as i.f. amplifiers following superconducting mixers operating in the millimeter and submillimeter frequency range.
Nucleation in A/B/AB blends: Interplay between microphase assembly and macrophase separation
Authors: Wang Jiafang , Müller Marcus , Wang Zhen-Gang
Published: April 2009

We study the interplay between microphase assembly and macrophase separation in A/B/AB ternary polymer blends by examining the free energy of localized fluctuation structures (micelles or droplets), with emphasis on the thermodynamic relationship between swollen micelles (microemulsion) and the macrophase-separated state, using self-consistent field theory and an extended capillary model. Upon introducing homopolymer B into a micelle-forming binary polymer blend A/AB, micelles can be swollen by B. A small amount of component B (below the A-rich binodal of macrophase coexistence) will not affect the stability of the swollen micelles. A large excess of homopolymer, B, will induce a microemulsion failure and lead to a macrophase separation. Between the binodal and the microemulsion failure concentration, macrophase separation in A/B/AB occurs by a two-step nucleation mechanism via a metastable microemulsion droplet of finite size. Our results illustrate a recently proposed argument that the two-step nucleation via a metastable intermediate is a general phenomenon in systems involving short-range attraction and long-range repulsion.
Effect of orthorhombic distortion on dielectric and piezoelectric properties of CaBi4Ti4O15 ceramics
Authors: Tanwar Amit , Sreenivas K. , Gupta Vinay
Published: April 2009

High temperature bismuth layered piezoelectric and ferroelectric ceramics of CaBi4Ti4O15 (CBT) have been prepared using the solid state route. The formation of single phase material with orthorhombic structure was verified from x-ray diffraction and Raman spectroscopy. The orthorhombic distortion present in the CBT ceramic sintered at 1200 °C was found to be maximum. A sharp phase transition from ferroelectric to paraelectric was observed in the temperature dependent dielectric studies of all CBT ceramics. The Curie’s temperature (Tc=790 °C) was found to be independent of measured frequency. The behavior of ac conductivity as a function of frequency (100 Hz–1 MHz) at low temperatures (<500 °C) follows the power law and is attributed to hopping conduction. The presence of large orthorhombic distortion in the CBT ceramic sintered at 1200 °C results in high dielectric constant, low dielectric loss, and high piezoelectric coefficient (d33). The observed results indicate the important role of orthorhombic distortion in determining the improved property of multicomponent ferroelectric material.
Hydrogen sorption in metal-polymer composites: The role of interfaces
Authors: Checchetto R. , Bazzanella N. , Miotello A. , Carotenuto G. , Nicolais L.
Published: April 2009

We studied the hydrogen storage capacity and sorption kinetics of composite materials made of hydride forming metal particles (LaNi5 or Pd, particle size of ∼1 μm) embedded into hydrogen permeable polymers. Experimental analysis shows that (i) the composite material consisting of LaNi5 particles dispersed into polysiloxane (PS-LaNi5) shows negligible H2 storage capacity while the LaNi5 particles dispersed into polyethylene (PE-LaNi5) are completely hydrogenated and (ii) the Pd particles dispersed both into polysiloxane (PS-Pd) and polyvinylpyrrolidone (PVP-Pd) are completely hydrogenated. The interfacial interactions in the PE-LaNi5 and in the PS-Pd composite materials have weak Van der Waals character while strong interfacial interactions occur in the PS-LaNi5 and in the PVP-Pd composites due to the formation of chemical bonds between polymer side groups and the metal surface atoms. Results indicate that in the metal-polymer composites the hydrogenation of the metallic phase cannot be obtained when the interfacial interactions between metal and polymer impede the surface activation of the metallic phase as in the PS-LaNi5 composite.
Electronic structures of Ba-on-Alq3 interfaces and device characteristics of organic light-emitting diodes based on these interfaces
Authors: Lim Jong Tae , Yeom Geun Young , Lhm Kyuwook , Kang Tai-Hee
Published: April 2009

The device performance of organic light-emitting diodes was significantly improved by inserting a Ba coverage (ΘBa) of 1 nm between tris(8-quinolinolato)aluminum (III) (Alq3) and the cathode. This improvement was attributed to the lowering of the electron-injecting barrier height that was induced by the formation of a new gap state from an interfacial chemical reaction, as well as band bending due to Fermi level pinning. However, the device with ΘBa above 1 nm showed poor device performance. The spectroscopic results indicated that the Alq3 molecules started to decompose by the reaction between Ba and the phenoxide moiety of the molecule.
Thermal evolution of microstructure in ion-irradiated GaN
Authors: Bae In-Tae , Jiang Weilin , Wang Chongmin , Weber William J. , Zhang Yanwen
Published: April 2009

The thermal evolution of the microstructure created by irradiation of a GaN single crystal with 2 MeV Au2+ ions at 150 K is characterized following annealing at 973 K using transmission electron microscopy. In the as-irradiated sample characterized at 300 K, Ga nanocrystals with the diamond structure, which is an unstable configuration for Ga, are directly observed together with nitrogen bubbles in the irradiation-induced amorphous layer. A simple model is proposed to explain Ga nanocrystal formation. Upon thermal annealing, the thickness of the amorphous layer decreases by ∼13.1% and nanobeam electron diffraction analysis indicates no evidence for residual Ga nanocrystals, but instead reveals a mixture of hexagonal and cubic GaN phases in the annealed sample. Nitrogen molecules, captured in the as-irradiated bubbles, appear to disassociate and react with Ga nanocrystals during the thermal annealing to form crystalline GaN. In addition, electron energy loss spectroscopy measurements reveal an volume change of 18.9% for the as-irradiated amorphous layer relative to the virgin single crystal GaN. This relative swelling of the damaged layer reduces to 7.7% after thermal annealing. Partial recrystallization and structural relaxation of the GaN amorphous state are believed responsible for the volume change.
Misfit strain induced magnetoelectric coupling in thin ferroic films
Authors: Glinchuk M. D. , Morozovska A. N. , Eliseev E. A. , Blinc R.
Published: April 2009

We show that the misfit strain due to the film-substrate lattice mismatch strongly increases the value of the quadratic magnetoelectric coupling. The coupling, size effects, and misfit strains cause strong changes in the phase diagrams of ferroic films at zero external magnetic and electric fields. The antiferromagnetic to ferromagnetic or ferrimagnetic phase transitions for compressive or tensile misfit strains open the way for the tailoring of magnetic and electric properties of ferroic films leading to advanced applications.
Autonomous low-power magnetic data collection platform to enable remote high latitude array deployment
Authors: Musko Stephen B. , Clauer C. Robert , Ridley Aaron J. , Arnett Kennneth L.
Published: April 2009

A major driver in the advancement of geophysical sciences is improvement in the quality and resolution of data for use in scientific analysis, discovery, and for assimilation into or validation of empirical and physical models. The need for more and better measurements together with improvements in technical capabilities is driving the ambition to deploy arrays of autonomous geophysical instrument platforms in remote regions. This is particularly true in the southern polar regions where measurements are presently sparse due to the remoteness, lack of infrastructure, and harshness of the environment. The need for the acquisition of continuous long-term data from remote polar locations exists across geophysical disciplines and is a generic infrastructure problem. The infrastructure, however, to support autonomous instrument platforms in polar environments is still in the early stages of development. We report here the development of an autonomous low-power magnetic variation data collection system. Following 2 years of field testing at the south pole station, the system is being reproduced to establish a dense chain of stations on the Antarctic plateau along the 40° magnetic meridian. The system is designed to operate for at least 5 years unattended and to provide data access via satellite communication. The system will store 1 s measurements of the magnetic field variation (<0.2 nT resolution) in three vector components plus a variety of engineering status and environment parameters. We believe that the data collection platform can be utilized by a variety of low-power instruments designed for low-temperature operation. The design, technical characteristics, and operation results are presented here.
Micromagnetic calculation of dynamic susceptibility in ferromagnetic nanorings
Authors: Wang Jianbo , Zhang Bin , Liu Qingfang , Ren Yong , Liu Ronglin
Published: April 2009

Dynamic magnetic susceptibilities of high-aspect-ratio permalloylike nanorings (outer diameter 20 nm, inner diameter 12 nm, length (L) range 12–500 nm) are studied using three-dimensional micromagnetic simulations. The investigated systems show two major resonance modes associated with volume and shape resonance modes, corresponding to low and high resonance frequencies, respectively. When L is below 40 nm, only the shape resonance mode is seen with a frequency predicted using the Kittel’s equation and demagnetization factor calculated for a ring. At sufficiently large L, the frequency of the volume mode converges to that of the Kittel prediction. For other lengths, however, neither the low resonance frequency nor the high resonance frequency agrees with the Kittel’s equation. A weighted average resonance frequency fa(i) that contains two major modes is introduced and shows the same trend as the results predicted by the Kittel’s equation for all lengths. The frequencies of volume and shape resonance modes have also been investigated by changing the exchange stiffness constant (A) and the saturation magnetization (Ms).
Splitting of transmission peak due to the hole symmetry breaking
Authors: Yin Xiao-gang , Huang Cheng-ping , Shen Zhi-qiang , Wang Qian-jin , Zhu Yong-yuan
Published: April 2009

We studied experimentally and theoretically the optical transmission through asymmetrical holes of a metal film, which is constructed by introducing small protuberances to the sides of individual square holes. Due to the symmetry breaking of the hole shape, an interesting transmission feature appears: both the Ag-glass (1, 0) and Ag-glass (1, 1) peaks split distinctly. Detailed studies indicate that the peak splitting is actually associated with the two asymmetrical waveguide surface-plasmon (WSP) modes confined on the surface of opposite hole walls. The finding demonstrates the crucial role of WSP modes and enriches our understanding of the phenomenon.
Tailoring carbon nanotips in the plasma-assisted chemical vapor deposition: Effect of the process parameters
Authors: Wang B. B. , Ostrikov K.
Published: April 2009

Carbon nanotips have been synthesized from a thin carbon film deposited on silicon by bias-enhanced hot filament chemical vapor deposition under different process parameters. The results of scanning electron microscopy indicate that high-quality carbon nanotips can only be obtained under conditions when the ion flux is effectively drawn from the plasma sustained in a CH4+NH3+H2 gas mixture. It is shown that the morphology of the carbon nanotips can be controlled by varying the process parameters such as the applied bias, gas pressure, and the NH3/H2 mass flow ratios. The nanotip formation process is examined through a model that accounts for surface diffusion, in addition to sputtering and deposition processes included in the existing models. This model makes it possible to explain the major difference in the morphologies of the carbon nanotips formed without and with the aid of the plasma as well as to interpret the changes of their aspect ratio caused by the variation in the ion/gas fluxes. Viable ways to optimize the plasma-based process parameters to synthesize high-quality carbon nanotips are suggested. The results are relevant to the development of advanced plasma-/ion-assisted methods of nanoscale synthesis and processing.
Electro-osmotic flow in a sector microchannel
Authors: Chang Chien C. , Wang Chang-Yi
Published: April 2009

The study presents analytical solutions of electro-osmotic flow in a sector microchannel with particular emphasis on the corner effects. The analytical solutions are obtained by the method of eigenfunction expansions in sequel for steady state, starting transient flow and oscillatory flow. It is shown that the smaller the opening angle is, the faster the flow approaches to steady state. For large nondimensional electrokinetic lengths, especially near an obtuse corner, a core of maximum velocity is soon established after the flow is started. The oscillatory flow exhibits phase lags between different modes that depend on their eigenvalues as well as the frequency of the externally applied voltage, hence distinguishing itself significantly from the steady state solution. This fact has an important physical implication about fast mixing of electrolytes in microchannels.
Restricted partition functions of the two-dimensional Ising model on a half-infinite cylinder
Authors: Arguin Louis-Pierre , Saint-Aubin Yvan
Published: April 2009

We study the Ising model on a half-infinite cylinder at the critical temperature. On the boundary circle, we fix four intervals of constant signs. Let θ1, θ2, θ3, and θ4 be the positions where the flips occur, labeled counterclockwise in that order. From each θ starts a contour between clusters of opposite signs. The contour leaving θ1 may end only at θ2 or θ4. Using an argument based on conformal field theory, we give the probability distribution that the contour leaving θ1 ends at θ2. The behavior of this function when θ2−θ1→0 is described by a power law with an exponent (53) that belongs to the Kac table but that corresponds to a nonunitarizable highest-weight representation. We check that this prediction agrees with a Monte Carlo simulation.
Synthesis parameter space of bismuth catalyzed germanium nanowires
Authors: Xiang Ying , Cao Linyou , Arbiol Jordi , Brongersma Mark L. , Fontcuberta i Morral Anna
Published: April 2009

The synthesis parameter space of bismuth catalyzed germanium nanowires by chemical vapor deposition is determined. The process window for high aspect ratio nanowires is found to be extremely narrow. The optimal conditions are found to be 300 °C and 150 Torr gas pressure. For lower temperatures, the solubility of Ge in Bi is too low for the nucleation of Ge nanowires to occur. For higher temperatures, small Bi droplets tend to evaporate leading to an extreme reduction in the nanowire density. The extremely low process temperature makes Bi a good candidate for its growth on low cost and low thermal budget substrates such as plastics.
Influence of the target front-surface curvature on proton acceleration in laser-foil interaction
Authors: Bin J. H. , Lei A. L. , Cao L. H. , Yang X. Q. , Huang L. G. , Yu M. Y. , Yu Wei
Published: April 2009

Energetic proton generation from thin foil targets by ultraintense laser pulse is investigated using two-dimensional particle-in-cell simulation. Foil targets with concave, flat, and convex front surfaces are considered. The maximum energy of the accelerated protons depends on the front-surface curvature, and the highest-energy protons are from the concave foil. The result can be attributed to an enhancement of the generation as well as concentration of the laser-driven hot electrons by the concave surface.
Lower-hybrid drift instability in a thin current sheet with κ velocity distribution
Authors: Huang Feng , Chen Yinhua , Shi Guifen , Hu Zuquan , Peng Haiou , Zheng Jugao , Yu M. Y.
Published: April 2009

The lower-hybrid drift instability (LHDI) in a thin current sheet in the intermediate-wavelength (kyρiρe∼1, where ky, ρe, and ρi are the wave vector and the electron and ion gyroradii, respectively) regime for particles with κ velocity distribution is studied. The latter is more suitable for describing nonthermal distributions with an enhanced high-energy tail and includes the Maxwellian as a limiting case. It is shown that linear electromagnetic LHDI can be excited near the center of the current sheet. The growth rate decreases, but the electromagnetic component of the LHD mode increases with increase in hot particles.
Full-wave simulation of enhanced outcoupling of organic light-emitting devices with an embedded low-index grid
Authors: Slootsky Michael , Forrest Stephen R.
Published: April 2009

Enhancement of light outcoupling into substrate modes by a grid of low-refractive-index material embedded into the organic layer of an organic light-emitting device (OLED) is analyzed using full-wave electromagnetic simulations. The low-index grid (LIG) redirects modes normally trapped within the high-index organic and indium tin oxide layers (waveguide modes) into the substrate where they can be further extracted into free space using methods such as microlens arrays or roughened surfaces. This increases the external quantum and power efficiencies without affecting the electroluminescent spectrum. The dependence on grid geometry, dimensions, and refractive index is explored to optimize the structure. Simulations show that up to 50% more light can be extracted from the high-index region using an ultralow-index (n=1.03) grid than a conventional device, and provided efficient substrate-to-air outcoupling, the external quantum efficiencies of LIG OLEDs can reach >50%.
The rotational spectrum of the FeD radical in its X Δ4 state, measured by far-infrared laser magnetic resonance
Authors: Jackson Michael , Zink Lyndon R. , Towle Jonathan P. , Riley Neil , Brown John M.
Published: April 2009

Transitions between the spin-rotational levels of the FeD radical in the v=0 level of the X Δ4 ground state have been detected by the technique of laser magnetic resonance at far-infrared wavelengths. Pure-rotational transitions have been observed for the three lowest spin components. Lambda-type doubling is resolved on all the observed transitions; nuclear hyperfine structure is not observed. The energy levels of FeD are strongly affected by the breakdown of the Born–Oppenheimer approximation and cannot be modeled accurately by an effective Hamiltonian. The data are therefore fitted to an empirical formula to yield term values and g-factors for the various spin-rotational levels involved.
Surface magnetization in non-doped ZnO nanostructures
Authors: Schoenhalz A. L. , Arantes J. T. , Fazzio A. , Dalpian G. M.
Published: April 2009

We have investigated the magnetic properties of non-doped ZnO nanostructures by using ab initio total energy calculations. Contrary to many proposals that ferromagnetism in non-doped semiconductors should be induced by intrinsic point defects, we show that ferromagnetism in nanostructured materials should be mediated by extended defects such as surfaces and grain boundaries. This kind of defects creates delocalized, spin-polarized states that should be able to warrant long-range magnetic interactions.
Zinc oxide nanowire networks for macroelectronic devices
Authors: Unalan Husnu Emrah , Zhang Yan , Hiralal Pritesh , Dalal Sharvari , Chu Daping , Eda Goki , Teo K. B. K. , Chhowalla Manish , Milne William I. , Amaratunga Gehan A. J.
Published: April 2009

Highly transparent zinc oxide (ZnO) nanowire networks have been used as the active material in thin film transistors (TFTs) and complementary inverter devices. A systematic study on a range of networks of variable density and TFT channel length was performed. ZnO nanowire networks provide a less lithographically intense alternative to individual nanowire devices, are always semiconducting, and yield significantly higher mobilites than those achieved from currently used amorphous Si and organic TFTs. These results suggest that ZnO nanowire networks could be ideal for inexpensive large area electronics.
Field-free molecular alignment for studies using x-ray pulses from a synchrotron radiation source
Authors: Ho Phay J. , Miller Michelle R. , Santra Robin
Published: April 2009

A short, intense laser pulse may be employed to create a spatially aligned molecular sample that persists after the laser pulse is over. We theoretically investigate whether this impulsive molecular alignment technique may be exploited for experiments using x-ray pulses from a third-generation synchrotron radiation facility. Using a linear rigid rotor model, the alignment dynamics of model molecular systems with systematically increasing size is calculated utilizing both a quantum density matrix formalism and a classical ensemble method. For each system, the alignment dynamics obtained for a 95 ps laser is compared with that obtained for a 10 ps laser pulse. The average degree of alignment after the laser pulse, as calculated quantum mechanically, increases with the size of the molecule. This effect is quantitatively reproduced by the classical calculations. The average degree of impulsive alignment is high enough to induce a pronounced linear dichroism in resonant x-ray absorption using the intense 100 ps x-ray pulses currently available. However, for structural studies based on elastic x-ray scattering, bright x-ray pulses with a duration of 1 ps or shorter will be required in order to make full use of impulsive molecular alignment.
Probing the magnetic state of Fe/FeO/Fe trilayers by multiple isotopic sensor layers
Authors: Couet S. , Diederich Th. , Stankov S. , Schlage K. , Slezak T. , Rüffer R. , Korecki J. , Röhlsberger R.
Published: April 2009

To obtain depth-selected information in magnetic multilayers, we propose a measurement scheme based on nuclear resonant scattering from multiple isotopic sensor layers. It takes advantage of the depth dependence of the photon wavefield intensity in grazing incidence geometry to enhance the signal from a given part of a multilayer. The technique is applied to study the magnetic structure of a Fe/Fe-oxide/Fe trilayer. We are able to fully determine in a direct manner the magnetic state of two ultrathin F57e probe layers embedded in the system. The proposed technique can potentially be extended to various grazing incidence x-ray scattering methods.
Investigation into the lateral junction growth of single asperity contact using static atomistic simulations
Authors: Jeng Yeau-Ren , Peng Shin-Rung
Published: April 2009

According to continuum mechanics theory, the metallic junctions formed between the contact asperities on two opposing surfaces increase in size until gross sliding occurs. Our atomistic simulations reveal that the onset of lateral junction growth is caused by the slips of the asperity atoms. Furthermore, it is shown that the presence of an adsorbed layer on the asperity surface delays the onset of lateral junction growth. The present simulation results are found to be consistent with the experimental results presented in the literature and provide a valuable interpretation of the lateral junction growth phenomenon from a nanoscale perspective.
Migration of species in a prototype diffusion barrier: Cu, O, and H in TiN
Authors: Tsetseris L. , Logothetidis S. , Pantelides S. T.
Published: April 2009

Experimental data on the migration of Cu impurities in TiN and in similar diffusion-barriers used in electronic devices have led to conflicting suggestions about the underlying physical mechanisms. Here we use results of first-principles calculations, which are in agreement with measured activations energies, to elucidate the atomic-scale processes of moderate and rapid diffusion of Cu through the bulk and intergrain voids of TiN films, respectively. We also find that O and H impurities are fast diffusers in TiN. The results offer an assessment for the efficiency of TiN diffusion-barriers with respect to properties, such as nature of impurities, stoichiometry, and crystallinity.
Fabricating scaffolds by microfluidics
Authors: Chung Kuo-yuan , Mishra Narayan Chandra , Wang Chen-chi , Lin Feng-hui , Lin Keng-hui
Published: April 2009

In this paper, we demonstrate for the first time the technique to using microfluidics to fabricate tissue engineering scaffolds with uniform pore sizes. We investigate both the bubble generation of the microfluidic device and the application of foam as a tissue engineering scaffold. Our microfluidic device consists of two concentric tapered channels, which are made by micropipettes. Nitrogen gas and aqueous alginate solution with Pluronic® F127 surfactant are pumped through the inner and the outer channels, respectively. We observe rich dynamic patterns of bubbles encapsulated in the liquid droplets. The size of the bubble depends linearly on the gas pressure and inversely on the liquid flow rate. In addition, monodisperse bubbles self-assemble into crystalline structures. The liquid crystalline foams are further processed into open-cell solid foams. The novel foam gel was used as a scaffold to culture chondrocytes.
Nanoparticulate AlO(OH)n filled polyvinylidenefluoride-co-hexafluoropropylene based microporous membranes for lithium ion batteries
Authors: Aravindan Vanchiappan , Vickraman Palanisamy
Published: April 2009

This paper presents the nanosized AlO(OH)n incorporated microporous membranes by phase inversion technique, for the first time, using polyvinylidenefluoride-co-hexafluoropropylene as a host matrix. The transport properties of the membranes were studied and analyzed by various techniques, namely, alternating current impedance spectroscopy, Fourier transform infrared spectroscopy, Raman spectra, differential scanning calorimetry, tensile strength, X-ray diffraction, and scanning electron microscope. Further, Brunauer–Emmett–Teller surface area measurements, percentage of crystallinity, electrolyte uptake, porosity, activation energy, and MacMullin number were also calculated for these microporous membranes.
Intramolecular energy transfer between the triplet of ancillary ligand and the metal to ligand charge transfer state existed in heterocyclometalated iridium (III) complexes
Authors: Han Liangliang , Yang Dongfang , Li Wenlian , Chu Bei , Chen Yiren , Su Zisheng , Zhang Dongyu , Yan Fei , Wu Shuanghong , Wang Junbo , Hu Zhizhi , Zhang Zhiqiang
Published: April 2009

Higher efficiency red organic light emitting devices (OLEDs) were obtained by employing Ir (III) complexes with 1-phenylbutane-1, 3-dione (ba) as the second ligand than that with acetylacetone (acac) as the second ligand, which were attributed to the intramolecular energy transfer existed in these complexes. The reason were attributed to the intramolecular energy transfer existed in these complexes and were approved by their photoluminescence characteristics at 77 K, as well the phosphorescence decay lifetime. Because of the lower triplet energy level of ba (Tba,19 230 cm−1) whose energy was suitable to transfer to the triplet of the metal to ligand charge transfer (MLCT) (M3LCT,16 260 cm−1) state compared to Tacac (25 500 cm−1), more efficient OLEDs were obtained (7.0 cd/A) using Ir[2-(4′-methanoxy-styryl)-benzothiazole]2ba (ba-2) than Ir[2-(4′-methanoxy-styryl)-benzothiazole]2acac acac-2 (6.1 cd/A).
Anomalous energy dissipation of electron current pulses propagating through an inhomogeneous collisionless plasma medium
Authors: Yadav Sharad Kumar , Das Amita , Kaw Predhiman , Sengupta Sudip
Published: April 2009

The evolution of fast rising electron current pulses propagating through an inhomogeneous plasma has been studied through electron magnetohydrodynamic fluid simulations. A novel process of anomalous energy dissipation and stopping of the electron pulse in the presence of plasma density inhomogeneity is demonstrated. The electron current essentially dissipates its energy through the process of electromagnetic shock formation in the presence of density inhomogeneity. A direct relevance of this rapid energy dissipation process to the fast ignition concept of laser fusion is shown.
Greatly enhanced azimuthal permeability of a ferrite core with a wire coil metamaterial
Authors: Li Z. W. , Huang R. F. , Kong L. B.
Published: April 2009

Metamaterial has been developed using a structure of Cu-wire coil wound on a ferrite core. The metamaterial has greatly enhanced azimuthal permeability, as compared to the mere core material, and its resonance frequency can be controlled through varying the number of turns of the coil. These special properties, which are significantly different from general magnetic material, can be understood by an equivalent lumped parameter model.
The stochastic separatrix and the reaction coordinate for complex systems
Authors: Antoniou Dimitri , Schwartz Steven D.
Published: April 2009

We present a new approach to the identification of degrees of freedom which comprise a reaction coordinate in a complex system. The method begins with the generation of an ensemble of reactive trajectories. Each trajectory is analyzed for its equicommittor position or transition state; then the transition state ensemble is identified as the stochastic separatrix. Numerical analysis of the points along the separatrix for variability of coordinate location correctly identifies the components of the reaction coordinate in a test system of a double well coupled to a promoting vibration and a bath of linearly coupled oscillators.
Galvanotactic and phototactic control of Tetrahymena pyriformis as a microfluidic workhorse
Authors: Kim Dal Hyung , Casale David , Kőhidai László , Kim Min Jun
Published: April 2009

A eukaryotic ciliate, Tetrahymena pyriformis, has been controlled using galvanotaxis and phototaxis in a low Reynolds number fluidic environment. A cell-tracking algorithm demonstrates the controllability of Tetrahymena pyriformis under two types of external stimuli. Electrical stimulation, in the form of a direct current electric field through the containing fluid, causes a change in swimming direction toward the cathode. Photostimulation, by high intensity broadband light, results in a rotational motion of the cells. The motivation of this work is to progress further with biological microfluidic actuators and sensors for use in engineered systems.