bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation in Augmentative and Alternative Communication: An Update for Speech-Language Pathology Training
Authors: Ratcliff Ann , Koul Rajinder , Lloyd Lyle L.
Published: January 2008

Purpose

To report on data from the current survey about academic and clinical education in augmentative and alternative communication (AAC), as well as to compare these findings with earlier surveys in an attempt to identify any changes being made as programs in the United States implement the new certification standards of the American Speech-Language-Hearing Association in the area of speech-language pathology.

Method

A survey was sent to all speech-language pathology training programs in the United States via e-mail directed to program directors or faculty teaching in AAC.

Results

A total of 168 surveys were returned, for a return rate of 57.93%. Seventy-three percent of the respondents had a separate course in AAC, and 80% indicated AAC content was infused in other courses.

Conclusions

Academic preparation in AAC, while varying across academic programs, has in general increased over the past decade. Data also suggested a continuing critical need for more academic and clinical preparation in this area.
Sustained Selective Attention Skills of Preschool Children With Specific Language Impairment: Evidence for Separate Attentional Capacities
Authors: Spaulding Tammie J. , Plante Elena , Vance Rebecca
Published: January 2008

Purpose

The present study was designed to investigate the performance of preschool children with specific language impairment (SLI) and their typically developing (TD) peers on sustained selective attention tasks.

Method

This study included 23 children diagnosed with SLI and 23 TD children matched for age, gender, and maternal education level. The children’s sustained selective attention skills were assessed with different types of stimuli (visual, nonverbal-auditory, linguistic) under 2 attentional load conditions (high, low) using computerized tasks. A mixed design was used to compare children across groups and performance across tasks.

Results

The SLI participants exhibited poorer performance than their peers on the sustained selective attention tasks presented in the auditory modality (linguistic and nonverbal-auditory) under the high attentional load conditions. Performance was comparable with their peers under the low attentional load conditions. The SLI group exhibited similar performance to their peers on the visual tasks regardless of attentional load.

Conclusion

These results support the notion of attention difficulties in preschool children with SLI and suggest separate attentional capacities for different stimulus modalities.
Substitution Errors in the Production of Word-Initial and Word-Final Consonant Clusters
Authors: Kirk Cecilia
Published: January 2008

Purpose

This study provides a comprehensive examination of substitutions that occur at Greenlee’s 3rd stage of cluster development (M. Greenlee, 1974). At this stage of cluster acquisition, children are able to produce the correct number of consonants but with 1 or more of these consonants being substituted for another.

Method

Participants were 11 typically developing children ages 1;5–2;7 (years;months) who were from monolingual English-speaking homes. Consonant clusters in both word-initial and word-final position were elicited using a picture identification task.

Results

Although previous studies have suggested that most cluster substitutions can be predicted from the errors children make on the corresponding singletons, our findings indicate that almost one third of substitutions in clusters are not predictable in this way. Furthermore, the majority of unpredictable substitutions produced by the children in this study resulted in clusters in which both consonants in the cluster shared the same place and/or manner of articulation. Thus, almost 70% of unpredictable substitutions appear to be motivated by assimilation within the cluster.

Conclusion

Ease of articulation provides the most convincing explanation for within-cluster assimilation.
Language and Independence in Adolescents With and Without a History of Specific Language Impairment (SLI)
Authors: Conti-Ramsden Gina , Durkin Kevin
Published: January 2008

Purpose

Achieving behavioral independence is a key task of adolescent development. This 1 article of a companion set of 2 (the 2nd addressing the topic of parental perspectives) presents an investigation of the impact of language ability on independence.

Method

Longitudinal and follow-up data from 120 adolescents with a history of specific language impairment (SLI), as well as concurrent data on a comparison group of 118 typically developing (TD) young people, are reported. Parental and self-report measures were used to examine independent functioning related to everyday living at the end of compulsory education (16 years of age).

Results

Adolescents with SLI are less independent than their TD peers, and level of independence is associated with poor early language and poor later literacy skills.

Conclusion

Language and literacy play a larger role in adolescent independent functioning than nonverbal abilities in both TD adolescents and adolescents with SLI.
Parental Perspectives During the Transition to Adulthood of Adolescents With a History of Specific Language Impairment (SLI)
Authors: Conti-Ramsden Gina , Botting Nicola , Durkin Kevin
Published: January 2008

Purpose

This is the 2nd article of a companion set (the 1st article being on language and independence). It presents research examining parental perspectives on aspects of impairment in their offspring involving families rearing children with specific language impairment (SLI).

Method

The same sample as that of the 1st study participated in this investigation: a total of 238 parents and their offspring (120 offspring with a history of SLI and 118 typically developing [TD] offspring). Parents were interviewed using the Transition Daily Rewards and Worries questionnaire (L. M. Glidden & B. M. Jobe, 2007; J. Menard, S. Schoolcraft, L. M. Glidden, & C. Lazarus, 2002). Measures of the adolescents’ receptive and expressive language, reading, nonverbal IQ, and socioemotional functioning were obtained.

Results

Parents of adolescents with a history of SLI had more negative expectations in the areas of future/adult life, socialization, and community resources. An exception was family relations, which was a source of reward for both sets of parents.

Conclusions

Parents of adolescents with SLI have a range of perspectives regarding their offspring; some raise concerns, some are more positive. In addition, there is striking heterogeneity in the experiences of parents in the SLI group. Variables that influence being a concerned parent involve the adolescent’s level of independence, quality of peer relations, his or her prosocial behavior, and the presence of conduct problems.
Acceptance of Noise Growth Patterns in Hearing Aid Users
Authors: Freyaldenhoven Melinda C. , Plyler Patrick N. , Thelin James W. , Muenchen Robert A.
Published: January 2008

Purpose

To examine whether the effects of speech presentation level on acceptance of noise could differentiate full-time, part-time, and nonusers of hearing aids and whether these effects could predict hearing aid use.

Method

Participants were separated into 3 groups on the basis of hearing aid use: (a) full-time use, (b) part-time use, or (c) nonuse. Acceptable noise levels (ANLs) were measured conventionally and at 8 fixed presentation levels. The effects of presentation level on ANL were determined by calculating global ANL (ANL averaged across presentation level) and ANL growth (slope of the ANL function).

Results

Global ANLs were smaller for full-time users than for part-time users and nonusers; however, global ANLs were not different for part-time users and nonusers. ANL growth differentiated full-time users from nonusers only. Conventional ANL predicted hearing aid use with 68% accuracy. Compared with conventional ANL, the accuracy of the prediction for global ANL and ANL growth decreased, and the accuracy of the prediction at presentation levels of 65 to 75 dB HL was maintained.

Conclusions

Global ANL differentiated the hearing aid groups in the same manner as conventional ANL. The effects of presentation level on acceptance of noise did not considerably increase the accuracy of the prediction compared with conventional ANL. Clinical applications are discussed.
High-Frequency Amplification and Sound Quality in Listeners With Normal Through Moderate Hearing Loss
Authors: Ricketts Todd A. , Dittberner Andrew B. , Johnson Earl E.
Published: January 2008

Purpose

One factor that has been shown to greatly affect sound quality is audible bandwidth. Provision of gain for frequencies above 4–6 kHz has not generally been supported for groups of hearing aid wearers. The purpose of this study was to determine if preference for bandwidth extension in hearing aid processed sounds was related to the magnitude of hearing loss in individual listeners.

Method

Ten participants with normal hearing and 20 participants with mild-to-moderate hearing loss completed the study. Signals were processed using hearing aid–style compression algorithms and filtered using two cutoff frequencies, 5.5 and 9 kHz, which were selected to represent bandwidths that are achievable in modern hearing aids. Round-robin paired comparisons based on the criteria of preferred sound quality were made for 2 different monaurally presented brief sound segments, including music and a movie.

Results

Results revealed that preference for either the wider or narrower bandwidth (9- or 5.5-kHz cutoff frequency, respectively) was correlated with the slope of hearing loss from 4 to 12 kHz, with steep threshold slopes associated with preference for narrower bandwidths.

Conclusion

Consistent preference for wider bandwidth is present in some listeners with mild-to-moderate hearing loss.
Telehealth Delivery of the Camperdown Program for Adults Who Stutter: A Phase I Trial
Authors: O’Brian Sue , Packman Ann , Onslow Mark
Published: January 2008

Purpose

This Phase I trial investigated the viability of telehealth delivery of the Camperdown Program with adults who stutter. This program involves speech restructuring.

Method

All treatment was conducted remotely with participant–clinician contact occurring by telephone and e-mail.

Results

Ten adults completed the program. The group showed an 82% reduction in stuttering frequency immediately after treatment and a 74% reduction 6 months after treatment. However, there was significant individual variation in response to the program.

Conclusion

These preliminary data suggest that telehealth Camperdown has the potential to provide efficacious treatment for clients who do not have access to traditional face-to-face treatment.
The Influence of Linguistic Content on the Lombard Effect
Authors: Patel Rupal , Schell Kevin W.
Published: January 2008

Purpose

The
Lombard effect
describes the tendency for speakers to increase pitch, intensity, and duration in the presence of noise. It is unclear whether these modifications are uniformly applied across all words within an utterance or whether information-bearing content words are further enhanced compared with function words. In the present study, the authors investigated the influence of linguistic content on acoustic modifications made to speech in noise.

Method

Sixteen speaker–listener pairs engaged in an interactive cooperative game in quiet, 60 dB of multitalker noise, and 90 dB of multitalker noise. Speaker productions were analyzed to examine differences in fundamental frequency (F
0
), intensity, and duration of target words in sentences across noise conditions.

Results

Proportional increases in F
0,
intensity, and duration were noted for all word types as noise increased from quiet to 60 dB. From quiet to 90 dB, content words that referred to agents, objects, and locations were disproportionately elongated compared with function words. Additionally, agents were further enhanced by increased F
0
.

Conclusions

At moderate noise levels, most word types appear to be uniformly boosted in F
0
, intensity, and duration. As noise increases, linguistic content shapes the extent of the Lombard effect, with F
0
and duration serving as primary cues for marking information-bearing word types.
Neuroplasticity and Rehabilitation Research for Speech, Language, and Swallowing Disorders
Authors: Gonzalez Rothi Leslie J. , Musson Nan , Rosenbek John C. , Sapienza Christine M.
Published: January 2008

Purpose

This article introduces a collection of consensus statements regarding the application of neuroplasticity principles to rehabilitation of dysphagia, dysarthria, apraxia, and aphasia.
Principles of Experience-Dependent Neural Plasticity: Implications for Rehabilitation After Brain Damage
Authors: Kleim Jeffrey A. , Jones Theresa A.
Published: January 2008

Purpose

This paper reviews 10 principles of experience-dependent neural plasticity and considerations in applying them to the damaged brain.

Method

Neuroscience research using a variety of models of learning, neurological disease, and trauma are reviewed from the perspective of basic neuroscientists but in a manner intended to be useful for the development of more effective clinical rehabilitation interventions.

Results

Neural plasticity is believed to be the basis for both learning in the intact brain and relearning in the damaged brain that occurs through physical rehabilitation. Neuroscience research has made significant advances in understanding experience-dependent neural plasticity, and these findings are beginning to be integrated with research on the degenerative and regenerative effects of brain damage. The qualities and constraints of experience-dependent neural plasticity are likely to be of major relevance to rehabilitation efforts in humans with brain damage. However, some research topics need much more attention in order to enhance the translation of this area of neuroscience to clinical research and practice.

Conclusion

The growing understanding of the nature of brain plasticity raises optimism that this knowledge can be capitalized upon to improve rehabilitation efforts and to optimize functional outcome.
Translational Research in Aphasia: From Neuroscience to Neurorehabilitation
Authors: Raymer Anastasia M. , Beeson Pelagie , Holland Audrey , Kendall Diane , Maher Lynn M. , Martin Nadine , Murray Laura , Rose Miranda , Thompson Cynthia K. , Turkstra Lyn , Altmann Lori , Boyle Mary , Conway Tim , Hula William , Kearns Kevin , Rapp Brenda , Simmons-Mackie Nina , Gonzalez Rothi Leslie J.
Published: January 2008

Purpose

In this article, the authors encapsulate discussions of the Language Work Group that took place as part of the Workshop in Plasticity/NeuroRehabilitation Research at the University of Florida in April 2005.

Method

In this narrative review, they define neuroplasticity and review studies that demonstrate neural changes associated with aphasia recovery and treatment. The authors then summarize basic science evidence from animals, human cognition, and computational neuroscience that is relevant to aphasia treatment research. They then turn to the aphasia treatment literature in which evidence exists to support several of the neuroscience principles.

Conclusion

Despite the extant aphasia treatment literature, many questions remain regarding how neuroscience principles can be manipulated to maximize aphasia recovery and treatment. They propose a framework, incorporating some of these principles, that may serve as a potential roadmap for future investigations of aphasia treatment and recovery. In addition to translational investigations from basic to clinical science, the authors propose several areas in which translation can occur from clinical to basic science to contribute to the fundamental knowledge base of neurorehabilitation. This article is intended to reinvigorate interest in delineating the factors influencing successful recovery from aphasia through basic, translational, and clinical research.
Swallowing and Dysphagia Rehabilitation: Translating Principles of Neural Plasticity Into Clinically Oriented Evidence
Authors: Robbins JoAnne , Butler Susan G. , Daniels Stephanie K. , Diez Gross Roxann , Langmore Susan , Lazarus Cathy L. , Martin-Harris Bonnie , McCabe Daniel , Musson Nan , Rosenbek John
Published: January 2008

Purpose

This review presents the state of swallowing rehabilitation science as it relates to evidence for neural plastic changes in the brain. The case is made for essential collaboration between clinical and basic scientists to expand the positive influences of dysphagia rehabilitation in synergy with growth in technology and knowledge. The intent is to stimulate thought and propose potential research directions.

Method

A working group of experts in swallowing and dysphagia reviews 10 principles of neural plasticity and integrates these advancing neural plastic concepts with swallowing and clinical dysphagia literature for translation into treatment paradigms. In this context,dysphagiarefers to disordered swallowing associated with central and peripheral sensorimotor deficits associated with stroke, neurodegenerative disease, tumors of the head and neck, infection, or trauma.

Results and Conclusions

The optimal treatment parameters emerging from increased understanding of neural plastic principles and concepts will contribute to evidence-based practice. Integrating these principles will improve dysphagia rehabilitation directions, strategies, and outcomes. A strategic plan is discussed, including several experimental paradigms for the translation of these principles and concepts of neural plasticity into the clinical science of rehabilitation for oropharyngeal swallowing disorders, ultimately providing the evidence to substantiate their translation into clinical practice.
Dust-induced instability in a rotating plasma
Authors: Mikhailovskii A. B. , Vladimirov S. V. , Lominadze J. G. , Tsypin V. S. , Churikov A. P. , Erokhin N. N. , Galvão R. M. O.
Published: January 2008

The effect of immobile dust on stability of a magnetized rotating plasma is analyzed. In the presence of dust, a term containing an electric field appears in the one-fluid equation of plasma motion. This electric field leads to an instability of the magnetized rotating plasma called the dust-induced rotational instability (DRI). The DRI is related to the charge imbalance between plasma ions and electrons introduced by the presence of charged dust. In contrast to the well-known magnetorotational instability requiring the decreasing radial profile of the plasma rotation frequency, the DRI can appear for an increasing rotation frequency profile.
Conformations of poly{G}–poly{C} π stacks with high hole mobility
Authors: Voityuk Alexander A.
Published: January 2008

Charge transfer properties of DNA depend strongly on the π stack conformation. In the present paper, we identify conformations of homogeneous poly-{G}–poly-{C} stacks that should exhibit high charge mobility. Two different computational approaches were applied. First, we calculated the electronic coupling squared, V2, between adjacent base pairs for all 1ps snapshots extracted from 15ns molecular dynamics trajectory of the duplex G15. The average value of the coupling squared ⟨V2⟩ is found to be 0.0065eV2. Then we analyze the base-pair and step parameters of the configurations in which V2 is at least an order of magnitude larger than ⟨V2⟩. To obtain more consistent data, ∼65000 configurations of the (G:C)2 stack were built using systematic screening of the step parameters shift, slide, and twist. We show that undertwisted structures (twist<20°) are of special interest, because the π stack conformations with strong electronic couplings are found for a wide range of slide and shift. Although effective hole transfer can also occur in configurations with twist=30° and 35°, large mutual displacements of neighboring base pairs are required for that. Overtwisted conformation (twist⩾38°) seems to be of limited interest in the context of effective hole transfer. The results may be helpful in the search for DNA based elements for nanoelectronics.
Metal-nonmetal transition in dense fluid hydrogen
Authors: Sumi Tomonari , Sekino Hideo
Published: January 2008

The density dependence of the fluid structure and electrical resistivity of dense fluid hydrogen are studied along an isotherm of T=104K using a density-functional theory for an electron-proton binary mixture. A metal-nonmetal (M-NM) transition is estimated to occur around the dimensionless density value of rs=2.19. The electrical resistivity rapidly increases around this value with a decrease in the hydrogen density. Simultaneously, the density dependence of the fluid structure reveals a significant jump near the M-NM transition. The character of the effective interaction potential between protons is qualitatively changed after the M-NM transition. The pressure variation suggests that the M-NM transition is a discontinuous phase transition under coexistence conditions with regard to the phase equilibrium between the metal and the nonmetal phases.
A comparative assessment of the perturbative and renormalized coupled cluster theories with a noniterative treatment of triple excitations for thermochemical kinetics, including a study of basis set and core correlation effects
Authors: Zheng Jingjing , Gour Jeffrey R. , Lutz Jesse J. , Włoch Marta , Piecuch Piotr , Truhlar Donald G.
Published: January 2008

The CCSD, CCSD(T), and CR-CC(2,3) coupled cluster methods, combined with five triple-zeta basis sets, namely, MG3S, aug-cc-pVTZ, aug-cc-pV(T+d)Z, aug-cc-pCVTZ, and aug-cc-pCV(T+d)Z, are tested against the DBH24 database of diverse reaction barrier heights. The calculations confirm that the inclusion of connected triple excitations is essential to achieving high accuracy for thermochemical kinetics. They show that various noniterative ways of incorporating connected triple excitations in coupled cluster theory, including the CCSD(T) approach, the full CR-CC(2,3) method, and approximate variants of CR-CC(2,3) similar to the triples corrections of the CCSD(2) approaches, are all about equally accurate for describing the effects of connected triply excited clusters in studies of activation barriers. The effect of freezing core electrons on the results of the CCSD, CCSD(T), and CR-CC(2,3) calculations for barrier heights is also examined. It is demonstrated that to include core correlation most reliably, a basis set including functions that correlate the core and that can treat core-valence correlation is required. On the other hand, the frozen-core approximation using valence-optimized basis sets that lead to relatively small computational costs of CCSD(T) and CR-CC(2,3) calculations can achieve almost as high accuracy as the analogous fully correlated calculations.
Two-dimensional homonuclear chemical shift correlation established by the cross-relaxation driven spin diffusion in solids
Authors: Xu Jiadi , Struppe Jochem , Ramamoorthy Ayyalusamy
Published: January 2008

A new type of spin diffusion, cross-relaxation driven spin diffusion (CRDSD), is investigated using N15 NMR on a N-acetyl-L-valyl-L-leucine (NAVL) single crystal under stationary condition. A two-dimensional (2D) pulse sequence that correlates the chemical shifts of N15 nuclei, with a radio-frequency spin lock on the N15 channel during the mixing time, is used to observe CRDSD. Experimental results obtained using CRDSD, rf-driven spin diffusion, and proton driven spin diffusion approaches on the NAVL single crystal are compared. Our experimental results suggest that the N15 spin diffusion rate can be enhanced by about 1000 times using CRDSD than by the normal proton driven spin diffusion. Interestingly, the required spin-locking rf field strength for CRDSD is much lower than that used for the rf-driven spin diffusion experiments. The cross-peak patterns observed in 2D N15–N15 correlation spectra using CRDSD and RFDSD are very different as they arise from different spin-spin interactions. A detailed theory describing CRDSD and RFDSD processes is also presented using a thermodynamic model. The speedy spin diffusion process rendered by the CRDSD approach will be useful to assign resonances from a uniformly N15 or C13 labeled proteins and peptides, particularly in aligned samples.
Effect of interstitial additions on magnetostriction in Fe–Ga alloys
Authors: Huang Mianliang , Lograsso Thomas A. , Clark A. E. , Restorff J. B. , Wun-Fogle M.
Published: January 2008

The additions of trace amounts of small interstitial atoms (carbon, boron, and nitrogen) to Fe–Ga (Galfenol) alloys have a small but beneficial effect on the magnetostriction of Fe–Ga alloys especially at high Ga compositions. The saturated magnetostrictions [(3∕2)λ100’s] of both slow cooled and quenched single crystal Fe–Ga–C alloys with Ga contents >18at.% are about 10%–30% higher than those of the comparable binary Fe–Ga alloys. For boron and nitrogen additions, the magnetostrictions of slow cooled alloys with Ga content >18at.% were approximately 20% higher than those of the binary Fe–Ga alloys. We assume that these small atoms enter interstitially into the octahedral site as in pure α-Fe and inhibit chemical ordering, resulting in increased λ100. Thermal analysis of the Fe–Ga binary alloys and Fe–Ga–C ternary alloys indicates that the addition of C into the Fe–Ga system decreases the formation kinetics of D03 and extends the disordered region beyond the maximum for slow cooled binary samples.
The shape dependency of two-dimensional magnetic field dependence of a Josephson junction
Authors: Watanabe Norimichi , Nakayama Akiyoshi , Abe Susumu , Kawai Sho , Nishi Yohei , Masuda Koji
Published: January 2008

Modulation characteristics of a Josephson current are usually measured by applying the external magnetic field parallel to the junction plane from one direction, and uniformity in tunnel barrier is discussed. So far, we have measured two-dimensional magnetic field dependence of a square Josephson junction by independently scanning the magnetic field (Hx,Hy) parallel to the junction plane from two directions. We can get a lot of information about spatial critical current distribution in a Josephson junction by observing the magnetic field dependence of a Josephson junction in two dimensions. This time, we have fabricated the different-shaped Josephson junctions and investigated the shape dependency of two-dimensional magnetic field dependence of a Josephson junction. We observed the Ic-(Hx,Hy) characteristics of triangular, hexagonal, and circular Josephson junctions quite different from the Ic-(Hx,Hy), characteristics of a square Josephson junction. Furthermore, we simulated two-dimensional magnetic field dependence of a Josephson junction by calculating the superconducting current density distribution in each magnetic field. The simulation results agreed well with experimental results.
Magnetic properties and magnetic entropy change in spinels (Cd,M)Cr2S4 with M=Cu or Fe
Authors: Shen Jun , Yan Li-Qin , Zhang Jian , Wang Fang-Wei , Sun Ji-Rong , Hu Feng-Xia , Rong Chuan-Bing , Li Yang-Xian
Published: January 2008

Magnetic properties and magnetic entropy changes in spinels (Cd,M)Cr2S4 with M=Cu or Fe have been studied. The saturation moments per formula unit are about 4.77μB for Cd0.8Cu0.2Cr2S4 and 4.41μB for Cd0.7Fe0.3Cr2S4. Magnetic transition in Cu- and Fe-doped samples are of second order in nature, and their Curie temperatures are TC=86 and 119K, respectively. The maximum values of magnetic entropy change ΔS are found to be 5.1 and 5.4J∕kgK for Cd0.8Cu0.2Cr2S4 and Cd0.7Fe0.3Cr2S4 for a field change from 0to5T, respectively. The significant ΔS suggests a potential of the sulfospinel as a magnetic refrigerant in the corresponding temperature range.
Experimental verification and analytical approach to cogging torque calculation and reduction of permanent magnet generators with multipole rotor for wind power applications
Authors: Choi Jang-Young , Jang Seok-Myeong
Published: January 2008

This paper deals with the experimental verification and analytical approach to cogging torque calculation and reduction of permanent magnet generators (PMGs) with multipole rotor for wind power applications. Using energy methods with Fourier series expansion, cogging torque is analytically determined with air-gap flux density due to permanent magnets (PMs) and two-dimensional permeance function. The analytical results are validated extensively by nonlinear finite element (FE) results for various values of pole arc ratio (αp) of PMs. It shows that there exists optimum αp which minimizes cogging torque. However, we confirm that measured value for cogging torque of the PMG with optimum αp is twice higher than predicted value. The reason for an error between measured and predicted cogging torques is discussed fully in terms of a shape of PMs and is proved experimentally. The influence of stator skew on cogging torque is also presented using analytical, nonlinear FE and experimental methods.
Microstructure and magnetic properties of CoCrPt–SiO2 perpendicular recording media with synthetic nucleation layers
Authors: Srinivasan Kumar , Piramanayagam S. N. , Wong Seng Kai , Kay Yew Seng
Published: January 2008

Thermally stable, highly textured CoCrPt–SiO2 perpendicular magnetic recording media with ∼6nm size exchange decoupled grains and tight grain size distribution were prepared on synthetic nucleation layers. The media structure consisted of 14nm thick CoCrPt–SiO2 recording layer on one Ru intermediate layer. For these films, insertion of a synthetic nucleation layer directly under the recording layer was seen to reduce the grain sizes from 6.7to6.2nm and grain size distribution from 17% to 14%. Significant reduction in the intergranular exchange coupling interactions could be achieved while improving magnetic properties. The crystallographic texture of the recording layer remained strongly (00⋅2) oriented with the dispersion Δθ50 below 3.7°. Isothermal remanence magnetization and thermal stability behavior were studied. A model that describes the role of the synthetic nucleation layer in affecting the grain growth and magnetic properties of the recording layer is presented to understand these observations.
Subkelvin cooling of a gram-sized oscillator
Authors: Mueller F. , Heugel S. , Wang L. J.
Published: January 2008

Mechanical oscillators have a long tradition in measuring very small forces, particularly of gravitational nature. Oscillators have thermal energy of kBT∕2 in each degree of freedom. Here, we demonstrate the dynamical cooling of a gram-sized oscillator to 300mK in equivalent temperature, a reduction of noise by a factor of 106 compared to the seismic background level. A simple physical model is provided for the cooling process. We also demonstrate the dynamic control of the oscillator’s eigenfrequency, aiming at providing a stationary reference point for position measurements. The method may find applications in precision measurements of weak forces.
Kinetic theory and simulation of collisionless tearing in bifurcated current sheets
Authors: Matsui Tatsuki , Daughton William
Published: January 2008

Observations from the Earth’s geomagnetic tail have established that the current sheet is often bifurcated with two peaks in the current density. These so-called bifurcated current sheets have also been reported in a variety of simulations and often occur in conjunction with significant temperature anisotropy. In this work, a new self-consistent Vlasov equilibrium is developed that permits both the current profile and temperature anisotropy to be independently adjusted. The stability of these layers with respect to the collisionless tearing mode is examined using both standard analytic techniques and a formally exact treatment involving a numerical evaluation of the full orbit integral. The resulting linear growth rate and mode structure are verified with fully kinetic particle-in-cell simulations. These results demonstrate that a bifurcated current profile has a strong stabilizing influence on the tearing mode in comparison to centrally peaked layers with a similar thickness. In contrast, electron temperature anisotropy is strongly destabilizing in the limit Te⊥>Te∥ and strongly stabilizing when Te⊥<Te∥. The simplified analytic theory is reasonably accurate in capturing these dependencies for long-wavelength modes, but the short-wavelength regime generally requires the full numerical treatment to accurately compute the growth rate.
Effect of spacer layer thickness on magnetic interactions in self-assembled single domain iron nanoparticles
Authors: Herndon Nichole B. , Oh Sang Ho , Abiade Jeremiah T. , Pai Devdas , Sankar Jag , Pennycook Stephen J. , Kumar Dhananjay
Published: January 2008

The magnetic characteristics of iron nanoparticles embedded in an alumina thin film matrix have been studied as a function of spacer layer thickness. Alumina as well as iron nanoparticles were deposited in a multilayered geometry using sequential pulsed laser deposition. The role of spacer layer thickness was investigated by making layered thin film composites with three different spacer layer thicknesses (6, 12, and 18nm) with fixed iron particle size of ∼13nm. Intralayer magnetic interactions being the same in each sample, the variation in coercivity and saturation magnetization is attributed to thickness dependent interlayer magnetic interactions of three types: exchange, strong dipolar, and weak dipolar. A thin film composite multilayer structure offers a continuously tunable strength of interparticle dipole-dipole interaction and is thus well suited for studies of the influence of interaction on the magnetic properties of small magnetic particle systems.
Dilute suspension flow with nanoparticle deposition in a representative nasal airway model
Authors: Shi H. , Kleinstreuer C. , Zhang Z.
Published: January 2008

The human nasal cavities with an effective length of only 10cm feature a wide array of basic flow phenomena because of their complex geometrics. Employing a realistic nasal airway model and demonstrating that laminar, quasisteady airflow can be assumed, dilute nanoparticle suspension flow and nanoparticle deposition are simulated and analyzed for 7.5⩽Q⩽20L∕min and 1⩽dp⩽150nm. The understanding and quantitative assessment of mixture flow fields and local nanoparticle wall concentrations in nasal airways with a thin mucus layer are very important for estimating the health risks of inhaled toxic aerosols, determining proper drug-aerosol delivery to target sites such as the olfactory regions and developing algebraic transfer functions for overall nasal dose-response analyses. Employing a commercial software package with user-supplied programs, the validated computer modeling results can be summarized as follows: (i) Most of the air flows through the middle-to-low main passageways. Higher airflow rates result in stronger airflow in the olfactory region and relatively lower flow rates in the meatuses. (ii) Nanoparticle deposition in human nasal airways is significant for tiny nanoparticles, i.e., 1⩽dp⩽2nm, which also represent some vapors. The smaller the nanoparticle size and the lower the flow rate, the higher are the total deposition efficiencies because of stronger diffusion and longer residence times. (iii) Nanoparticles with dp<5nm flow preferentially through the middle-to-low main passageway along with the major portion of the airflow. For relatively large nanoparticles (dp⩾5nm), due to the low diffusivities, fewer particles will deposit onto the wall leaving a much thinner nanoparticle gradient layer near the wall, i.e., such nanoparticles pass through the nasal cavities more uniformly with minor wall deposition. (iv) Secondary flows may enhance nanoparticle transport and deposition, especially in the meatuses by convecting nanoparticles into these particular regions. (v) For the olfactory region, an optimal particle size may exist due to the combined effects of nanoparticle transport and local deposition mechanisms. However, because of the low deposition flux and small surface area, the olfactory channels account for only very small total deposition values. (vi) A compact correlation for predicting nanoparticle deposition in human nasal airways has been developed.
Microconfined equiviscous droplet deformation: Comparison of experimental and numerical results
Authors: Vananroye Anja , Janssen Pieter J. A. , Anderson Patrick D. , Van Puyvelde Peter , Moldenaers Paula
Published: January 2008

The dynamics of confined droplets in shear flow is investigated using computational and experimental techniques for a viscosity ratio of unity. Numerical calculations, using a boundary integral method (BIM) in which the Green’s functions are modified to include wall effects, are quantitatively compared with the results of confined droplet experiments performed in a counter-rotating parallel plate device. For a viscosity ratio of unity, it is experimentally seen that confinement induces a sigmoidal droplet shape during shear flow. Contrary to other models, this modified BIM model is capable of predicting the correct droplet shape during startup and steady state. The model also predicts an increase in droplet deformation and more orientation toward the flow direction with increasing degree of confinement, which is all experimentally confirmed. For highly confined droplets, oscillatory behavior is seen upon startup of flow, characterized by an overshoot in droplet length followed by droplet retraction. Finally, in the case of a viscosity ratio of unity, a minor effect of confinement on the critical capillary number is observed both numerically and experimentally.
Enhancement of the transverse conductance in DNA nucleotides
Authors: Meunier Vincent , Krstić Predrag S.
Published: January 2008

We theoretically study the electron transport properties of DNA nucleotides placed in the gap between two single-wall carbon nanotubes capped or terminated with H or N. We show that in the case of C-cap and H-termination the current at low electric bias is dominated by nonresonant tunneling, similarly to the cases of gold electrodes. In nitrogen-terminated nanotube electrodes, the nature of current is primarily quasiresonant tunneling and is increased by several orders of magnitude. We discuss the consequence of our result on the possibility of recognition at the level of single molecule.
Carbon diffusion around the edge region of nickel nanoparticles
Authors: Shin Young-Han , Hong Suklyun
Published: January 2008

Adsorption and diffusion of carbon atoms in nickel are studied by density-functional theory calculations to understand the growth mechanism of carbon nanotubes in its initial stage. Combined with the results for surface and subsurface diffusions, the diffusion behaviors around the edges between low-index nickel surfaces reveal that the growth of carbon nanotubes is related to the diffusion barriers across these edge regions of nickel nanoparticles in addition to the growth temperature. We explain these results in terms of the reaction mechanisms which are kinetically or thermodynamically controlled depending on the temperature at which the carbon nanotubes grow.
The effective medium approximation for annealed magnetoelectric polycrystals
Authors: Liu Y. Y. , Xie S. H. , Li J. Y.
Published: January 2008

Magnetoelectric polycrystals usually possess antiferromagnetic domains with oppositive magnetoelectric coefficients, and have to be annealed under the appropriate electric and magnetic fields to make the polycrystals macroscopically magnetoelectric. In this paper, we developed an effective medium approximation to calculate the macroscopic coefficients of magnetoelectric polycrystals annealed through Néel’s temperature, and studied the effects of temperature as well as shape and orientation distribution of grains on the macroscopic magnetoelectric coefficients of polycrystalline Cr2O3. It is observed that the effective magnetoelectric coefficient of polycrystal is higher than single-crystalline a11 but lower than single-crystalline a33, and that calculated from the effective medium approximation is higher than simple volume averaging and agrees with experimental data better. It is also noted that polycrystals with randomly oriented grains are optimal for a11∗, while those with fiber texture are optimal for a33∗. In addition, the lamellar grain is optimal for the effective magnetoelectric coupling, with the magnetoelectric coefficient about 20% higher than those with spherical grains.
High-efficiency stacked white organic light-emitting diodes
Authors: Lee Tae-Woo , Noh Taeyong , Choi Byoung-Ki , Kim Myeong-Suk , Shin Dong Woo , Kido Junji
Published: January 2008

We report efficient tandem white organic light-emitting diodes (WOLEDs) by using bathocuproine:Cs2CO3∕MoO3 as an effective interconnecting layer. We utilized two primary colors of sky blue and orange fluorescent emitters to obtain efficient white electroluminescence. Although single WOLEDs using two adjacent emitting layers showed a maximum current efficiency of 7.96cd∕A with Commission Internationale d’Eclairage (CIE) coordinates of (0.28, 0.34), the tandem WOLED device made by stacking two single color OLEDs in series demonstrated doubled maximum current efficiency of 17.14cd∕A with CIE coordinates of (0.28, 0.41). The stacking of different single color OLEDs in series instead of double stacking of WOLEDs can be useful to achieve highly efficient WOLEDs because it can reduce the number of layers of the devices.
Low-losses, highly tunable Ba0.6Sr0.4TiO3∕MgO composite
Authors: Chung U.-Chan , Elissalde C. , Maglione M. , Estournès C. , Paté M. , Ganne J. P.
Published: January 2008

Spark plasma sintering (SPS) is an efficient tool to obtain highly densified ferroelectric-dielectric ceramic composites with clean interfaces and tunable properties. Dielectric MgO and ferroelectric Ba0.6Sr0.4TiO3 (BST) were combined in two-dimensional multilayer and three-dimensional random powders design. Their unmodified BST Curie temperature proves the suppression of interdiffusion while dielectric losses are below 0.5% and the tunability is 40% at room temperature. The composites and pure BST with similar densities (>95%) were obtained, owing reliable comparison of their dielectric properties. Such SPS ceramics can be used as experimental input for simulation and are potential candidates for high frequency applications.
Carbon nanotube surface attenuated infrared absorption
Authors: Setyowati Kristina , Piao Ming Jun , Chen Jian , Liu Haiying
Published: January 2008

The carbon nanotube (CNT) surface quality plays a critical role in defining the molecule-nanotube, macromolecule-nanotube, metal/semiconductor-nanotube, and nanotube-nanotube interfaces, which are at the heart of numerous potential CNT-based applications in electronics, sensors, nanocomposites, thermal management, actuators, energy storage and conversion, and drug delivery. We report that the infrared vibrations of adsorbed molecules/macromolecules that give rise to dipole changes parallel to the highly polarizable CNT surface are diminished significantly in intensity. The CNT surface attenuated infrared absorption provides a mechanism to probe and compare the overall surface qualities of various bulk CNT materials.
Investigation of AlGaN∕AlN∕GaN heterostructures for magnetic sensor application from liquid helium temperature to 300°C
Authors: Bouguen L. , Contreras S. , Jouault B. , Konczewicz L. , Camassel J. , Cordier Y. , Azize M. , Chenot S. , Baron N.
Published: January 2008

We report a comparative investigation of the magnetic response of long channel AlGaN∕AlN∕GaN heterostructures (Hall-field effect transistor devices) grown on three different semi-insulating templates on silicon and sapphire. From Hall effect measurements conducted up to 573K (300°C), we find that some of these specific devices can be used as magnetic sensors in a large temperature range (∼600°C) with a magnetic sensitivity close to 60V∕AT and a small thermal drift. On the best sample, between liquid helium temperature and 300°C, the average value of the thermal drift is only −7ppm∕°C.
Development of 40MHz inductively coupled plasma source and frequency effects on plasma parameters
Authors: Jun Hyun-Su , Chang Hong-Young
Published: January 2008

A large-area inductively coupled plasma (ICP) source capable of securing azimuthal plasma uniformity at a 40.00MHz has been developed. The antenna, referred to as a capacitor distributed resonance antenna, minimizes the azimuthally nonuniform antenna capacitive field with eight distributed vertical capacitors. The antenna was designed to maximize the antenna current using L-C series resonance. Based on plasma diagnostics with a 13.56MHz conventional ICP, comparative analyses were performed in terms of the plasma density, electron temperature, and frequency characteristics of the electron energy probability function (EEPF). In addition, the frequency dependency of the EEPF was found in the collisional (νen>ω), normal skin [vth∕δ⪡(ω2+νen2)1∕2] regime and the physical causes of were examined.
Compositional investigation of liquid crystal alignment on tantalum oxide via ion beam irradiation
Authors: Kim Jong-Yeon , Oh Byeong-Yun , Kim Byoung-Yong , Kim Young-Hwan , Han Jin-Woo , Han Jeong-Min , Seo Dae-Shik
Published: January 2008

The homogeneously aligned liquid crystal display on Ta2O5 via ion beam (IB) irradiation was first embodied with controllability of pretilt angle depending on incident angle of the IB. As a result of x-ray photoelectron spectroscopic analysis, the intensity of Ta–O and O–Ta bondings as a function of incident angle behaved reversely with the pretilt angle and the lowest amplitude was observed at 45°. It revealed that the creation of pretilt angle was attributed to the irradiation of the IB by breaking Ta–O and O–Ta bonding so orientational order was generated by directional IB. Comparable electro-optical characteristics to rubbed polyimide were also achieved.
Transition from direct tunneling to field emission in carbon nanotube intramolecular junctions
Authors: Chiu Po-Wen , Roth Siegmar
Published: January 2008

Transport measurements through metal-semiconductor carbon nanotube intramolecular junctions were carried out at high gate voltages in which regime the influence of Schottky barrier to charge transport is weak. The I-Vds curves exhibit an inflection point in the form of ln(I∕Vds2)−1∕Vds, showing a transition of transport mechanism from direct tunneling to field emission. The findings are interpreted in terms of quantum tunneling through a rectanglelike barrier at the junction, with a barrier width of ∼4nm, in good agreement with that observed on pentagon-heptagon defects at nanotube junctions via scanning tunneling spectroscopy.
Suppression of the orientation effects on bandgap in graphene nanoribbons in the presence of edge disorder
Authors: Querlioz D. , Apertet Y. , Valentin A. , Huet K. , Bournel A. , Galdin-Retailleau S. , Dollfus P.
Published: January 2008

This letter shows that a moderate degree of edge disorder can explain the fact that the experimentally measured bandgaps of graphene nanoribbons (GNRs) do not depend on orientation. We argue that GNRs actually behave similarly to Anderson insulators and the measured bandgaps should thus be interpreted as quasi-mobility edges. Calculations in the tight binding approach reveal that in the presence of edge disorder, quasi-mobility edge and electronic structures become independent of orientation and that quasi-mobility edge follows a quasi-universal law similar to experimental data, although with different parameters.