bluuebunny/crossref_metadata_2025 huggingface dataset:
Old Wine in New Bottles ***or Canadian Conference with a difference
Authors: Barber Marianne
Published: July 2008

Every once in a while a conference should have a “wow” factor. This year, thanks to an overseas bursary from BIALL and encouragement from our Head of Information Services, I was lucky enough to attend such an event. Despite the threat of SARs and a management restructuring at work, I found myself in Niagara-on-the-Lake at the end of May at the 2003 conference of the Canadian Association of Law Librarians (Association Canadienne des Biblioteques de Droit.)
Mobilität und Balance
Authors: Schmitt Katrin , Kressig Reto W.
Published: July 2008

Die Autonomie und Lebensqualität älterer Menschen ist eng mit ihrer Mobilität verbunden. Eine Einschränkung dieser Mobilität kann weit reichende Folgen bis hin zur Notwendigkeit einer Institutionalisierung nach sich ziehen. Auch dient der Gang bzw. die Ganggeschwindigkeit zur Definition des Frailty-Syndromes. Neben einer sorgfältigen Anamnese und körperlichen Untersuchung kann die Mobilität mittels einfacher Screeningverfahren getestet werden. Hierdurch können neben prädiktiven Aussagen hinsichtlich des Sturzrisikos eines Patienten auch Hinweise auf geeignete Interventionen gewonnen werden. Bei Patienten mit rezidivierenden Sturzereignissen sollte ein spezialisiertes Assessment mittels Ganganalyse erfolgen. Dies ermöglicht neben einer detaillierten Evaluierung des Sturzrisikos auch Hinweise auf die Exekutivfunktionen des Probanden zu erhalten. Neben einer Verbesserung der Propriozeption durch geeignetes Schuhwerk dient auch regelmäßiges körperliches Training der Sturzprävention. Besonders für Tai Chi konnte diese sturzpräventive Eigenschaft gezeigt werden.
Gradiometry for polarized seismic waves
Authors: Langston Charles A. , Liang Chuntao
Published: July 2008

Wave gradiometry for a generic point source wave model in cylindrical coordinates is developed to utilize the horizontal components of seismic wavefields. Attributes of P‐SV and SH waves such as horizontal slowness and its change, the change in geometrical spreading, the change in radiation pattern, azimuth of propagation, and wave polarization can be determined by measuring the horizontal strains and rotations of the wavefield along with three components of displacement. Gradiometer cells composed of an array of three‐component seismographs can be used to provide estimates of the wave gradients. Alternatively, a single three‐component seismograph collocated with an areal strainmeter (for P‐SV waves) or a rotation sensor (for SH waves) can be used to estimate wave polarization and the slowness/amplitude behavior of one aspect of the wavefield. Wave gradients are computed for the 1 April 2007 Solomon Island earthquake using data from the ANZA Seismic Network in southern California and show excellent consistency among stations of the network. Azimuth and slowness of various long‐period teleseismic waves are recovered using gradiometry analysis. The consistency of strains computed from the broadband array suggests that they may be used to calibrate Plate Boundary Observatory tensor strainmeters in the region.
Synthesis of vector‐wave envelopes in 3‐D random media characterized by a nonisotropic Gaussian ACF based on the Markov approximation
Authors: Sato Haruo
Published: July 2008

The earthquake source duration is short; however, the apparent duration time of observed seismogram increases with travel distance. The amplitude excitation is observed even on the transverse component for P waves, on the longitudinal component for S waves. These phenomena are well explained by scattering due to random velocity inhomogeneities around the global seismic ray. We directly synthesize vector‐wave envelopes in 3‐D random elastic media statistically characterized by a nonisotropic Gaussian autocorrelation function (ACF). The method uses the Markov approximation in the case that the wavelength is shorter than the correlation distance and the ray direction is parallel to one of the principal axes of the ACF. A spherical outgoing vector wavelet radiated from a point source in the random elastic media is used as a basic model for high‐frequency seismogram envelopes from micro‐earthquakes in the inhomogeneous lithosphere. The stochastic master equation for the two‐frequency mutual coherence function (TFMCF) of the potential field is analytically solved. The Fourier transform of TFMCF gives mean square (MS) envelopes of band‐pass filtered vector‐wave traces. If the ACF is axially symmetric around the ray direction, MS envelopes of vector components are analytically solved. The aspect ratio of the correlation distance in the longitudinal direction to that in the transverse direction is the key parameter for the envelope broadening and the excitation in the orthogonal component. Envelope broadening becomes longer and the transverse (longitudinal) component amplitude increases for a P wavelet (for an S wavelet) when the correlation distance in the transverse plane becomes smaller. When the vertical correlation distance is shorter than the horizontal one as seen in the real Earth, the envelope broadening is larger for horizontal raypaths compared with vertical raypaths.
Efficient interpolation of high‐frequency domain data by phase smoothing
Authors: Yang Jie , Taylor Mary C. , Zhang Yu , Sarkar Tapan K.
Published: July 2008

In this paper, a novel phase‐smoothing method is proposed to efficiently interpolate the fine resolution frequency data from sparse samples in the high‐frequency range. This is achieved by taking the effect of the complex exponential term e−jkr in the electromagnetic field into account, which causes the oscillation in the system response especially in the high‐frequency domain. By phase‐smoothing, even though the magnitude of the field quantity is unchanged, both real and imaginary parts of the frequency response become smoother. The interpolation is performed separately for both real and imaginary parts so that the sample rate required for accurate reconstruction is significantly reduced. The interpolation is carried out by the matrix pencil method, the coefficients of which are calculated by using the total least squares implementation to improve accuracy. Several numerical examples are presented to illustrate the applicability of this unique phase‐smoothing method in ultra‐high‐frequency bands.
Changes in seal capacity of fractured claystone caprocks induced by dissolved and gaseous CO2 seepage
Authors: Andreani M. , Gouze P. , Luquot L. , Jouanna P.
Published: July 2008

Claystone caprocks are often the ultimate seal for CO2 underground storage when residual CO2 gas reaches the reservoir top due to buoyancy. Permeability changes of a fractured claystone due to seepage of CO2‐enriched brine and water vapor‐saturated CO2 gas are investigated. Results show that brine flow induces a large porosity increase (up to 50%) in the vicinity of the fracture due to dissolution of calcite and quartz, while permeability remains unchanged. Conversely, cyclic flows of CO2‐brine and CO2‐gas increase the fracture aperture abruptly after each gas flow period, producing a progressive decrease of the caprock seal capacity. Aperture increase is controlled by decohesion of the clay framework within a micrometer‐scale‐thick layer induced by CO2‐gas acidification. Results show that hydraulic aperture increases linearly with duration of the preceding CO2‐brine flow period, emphasizing the kinetic control of the quartz grains dissolution during the brine flow periods.
The Effects of Divided Attention on Speech Motor, Verbal Fluency, and Manual Task Performance
Authors: Dromey Christopher , Shim Erin
Published: July 2008

Purpose

The goal of this study was to evaluate aspects of the
functional distance hypothesis,
which predicts that tasks regulated by brain networks in closer anatomic proximity will interfere more with each other than tasks controlled by spatially distant regions. Speech, verbal fluency, and manual motor tasks were examined to ascertain whether right-handed activity would interfere more with speech and language performance because of the presumed greater demands on the left hemisphere.

Method

Twenty young adults completed a speech task (repeating a sentence), a verbal fluency task (listing words beginning with the same letter), and right- and left-handed motor tasks (placing pegs and washers in a pegboard) in isolation and concurrently.

Results

Speech kinematic data showed that during concurrent performance of manual tasks, lip displacement and peak velocity decreased, whereas sound pressure level increased. Spatiotemporal variability increased when the nondominant hand was used for a motor task. Manual motor scores significantly decreased when concurrently performed with the verbal fluency task but not with sentence repetition.

Conclusion

These findings suggest that the control of concurrent tasks may be more complex than is predicted by the functional distance hypothesis.
Developmental Changes in the Effects of Utterance Length and Complexity on Speech Movement Variability
Authors: Sadagopan Neeraja , Smith Anne
Published: July 2008

Purpose

The authors examined the effects of utterance length and linguistic complexity on speech movement consistency for 210 participants between the ages of 5 and 22 years. Variability and durational analyses were conducted to (a) determine a more complete picture of the developmental course of earlier observations of the effects of linguistic constructs on speech motor variability and (b) describe trends for duration of the same sequence of words in different sentential contexts across development.

Method

Lower-lip movement was recorded during the production of “buy Bobby a puppy” spoken in isolation as well as embedded as a phrase in 2 longer, more complex sentences.

Results

Compared with young adults, children demonstrated higher variability in producing repeated movement sequences for the target word sequence across all conditions. Also, for all age groups except young adults, increased processing demands resulted in significantly increased movement trajectory variability. Duration analyses suggest that around age 9 years, children begin to use adult-like pre-speech processes to plan the timing of sentence internal phrases, and maturation of these planning processes continues through late adolescence.

Conclusion

These results provide further evidence for language–motor interactions and for a protracted course of speech motor development that continues well into adolescence.
Multichannel Compression: Effects of Reduced Spectral Contrast on Vowel Identification
Authors: Bor Stephanie , Souza Pamela , Wright Richard
Published: July 2008

Purpose

To clarify if large numbers of wide dynamic range compression channels provide advantages for vowel identification and to measure its acoustic effects.

Methods

Eight vowels produced by 12 talkers in the /hVd/ context were compressed using 1, 2, 4, 8, and 16 channels. Formant contrast indices (mean formant peak minus mean formant trough; maximum formant peak minus minimum formant trough) were developed to quantify spectral changes. Twenty listeners with mild to moderately severe sensorineural hearing loss identified the compressed vowels in an 8-alternative forced-choice procedure.

Results

Formant contrast measures revealed significant spectral flattening for 6 of the 8 vowels as channel number increased. A significant decrease in vowel identification performance was also observed as spectral contrast decreased.

Conclusions

Increasing the number of wide dynamic range compression channels may not be beneficial for all speech signals, and individual vowel identification performance can vary greatly for listeners with similar hearing loss.
Babbling, Chewing, and Sucking: Oromandibular Coordination at 9 Months
Authors: Steeve Roger W. , Moore Christopher A. , Green Jordan R. , Reilly Kevin J. , Ruark McMurtrey Jacki
Published: July 2008

Purpose

The ontogeny of mandibular control is important for understanding the general neurophysiologic development for speech and alimentary behaviors. Prior investigations suggest that mandibular control is organized distinctively across speech and nonspeech tasks in 15-month-olds and adults and that, with development, these extant forms of motor control primarily undergo refinement and rescaling. The present investigation was designed to evaluate whether these coordinative infrastructures for alimentary behaviors and speech are evident during the earliest period of their co-occurrence.

Method

Electromyographic (EMG) signals were obtained from the mandibular muscle groups of 15 typically developing 9-month-old children during sucking, chewing, and speech.

Results

Unlike prior investigations of 12- and 15-month-olds and adults, 9-month-olds' analyses of peak correlations among agonist and antagonist comparisons of mandibular EMG data revealed weak coupling during sucking, chewing, and babble; associated lag values for antagonist muscle groups indicated greater synchrony during alimentary behaviors and less synchrony during babble. Unlike the speech data of 15-month-olds, 9-month-olds exhibited consistent results across speech subtasks.

Conclusion

These findings were consistent with previous results in which mandibular coordination across behaviors was more variable for younger age groups, whereas the essential organization of each behavior closely reflected that seen in older infants and adults.
Stuttering and Natural Speech Processing of Semantic and Syntactic Constraints on Verbs
Authors: Weber-Fox Christine , Hampton Amanda
Published: July 2008

Purpose

Previous findings from event-related brain potentials (ERPs) indicate that adults who stutter (AWS) exhibit processing differences for visually presented linguistic information. This study explores how neural activations for AWS may differ for a linguistic task that does not require preparation for overt articulation or engage the articulatory loop for silent speech.

Method

Syntactic and semantic processing constraints were examined in AWS and adults who are normally fluent (AWNF) by assessment of their behavioral performance and ERPs in a natural speech listening task.

Results

AWS performed similarly to AWNF in identifying verb-agreement violations and semantic anomalies, but ERPs elicited by syntactic and semantic constraints indicated atypical neural functions for AWS. ERPs of the AWNF displayed an expected N400 for reduced semantic expectations and a typical P600 for verb-agreement violations. In contrast, both N400s and P600s for the semantic and verb-agreement conditions were observed in the ERPs of the AWS.

Conclusions

The findings suggest that AWS may engage semantic–syntactic mechanisms more generally for semantic and syntactic processing. These findings converge with earlier studies using visual stimuli to indicate that whereas linguistic abilities are normal in AWS, underlying brain activity mediating some aspects of language processing may function differently.
Phonatory Effects of Airway Dehydration: Preliminary Evidence for Impaired Compensation to Oral Breathing in Individuals With a History of Vocal Fatigue
Authors: Sivasankar Mahalakshmi , Erickson Elizabeth , Schneider Sara , Hawes Ashleigh
Published: July 2008

Purpose

Airway drying is detrimental to phonation and is posited to exacerbate vocal fatigue. However, limited research has demonstrated the adverse phonatory effects of dehydration in speakers reporting vocal fatigue. We compared the negative phonatory consequences of short-term oral breathing at low, moderate, and high humidity in individuals reporting a history of vocal fatigue and control participants.

Method

Females reporting a history of vocal fatigue (N= 8) and matched controls (N= 8) participated in a repeated-measures design over 3 different days.

Results

Oral breathing at low and moderate humidity increased phonation threshold pressure (PTP) to a greater extent in individuals reporting a history of vocal fatigue as compared to controls. Conversely, PTP did not increase in either participant group after oral breathing in a humid environment. Perceived phonatory effort (PPE) ratings were poorly correlated with PTP.

Conclusions

The emergence of between-group differences in PTP at low and moderate but not high ambient humidity demonstrates that drying challenges might be detrimental to voice production in individuals with a history of vocal fatigue. Based on the phonatory effects of dehydration, we suggest that individuals reporting vocal fatigue may demonstrate impaired compensation to airway drying induced by short-term oral breathing.
Scalar-energy spectra in simulations of Sc⪢1 mixing by turbulent jets using the nonlinear large-eddy simulation method
Authors: Burton Gregory C.
Published: July 2008

The nonlinear large-eddy simulation (nLES) method is applied to the first numerical study of passive-scalar mixing by a turbulent shear flow at a high Schmidt number (Sc⪢1). The work is intended to address inconsistencies between previous studies concerning the formation of power-law scaling in the scalar-energy spectra at viscous-convective scales. Results are reported for LES of a round turbulent jet at Sc=1024 and ReD=2000. The nLES method is first shown to recover the large-scale jet structure, including the self-similarity of far-field scalar moments. Scalar timeseries and spatial data produce the first power spectra from a LES shear-flow study that exhibits k−1 scaling at viscous-convective scales, consistent with the analysis of Batchelor [J. Fluid Mech. 5, 113 (1959)] and recent direct numerical studies of simpler Sc⪢1 flows.
Numerical fringe pattern demodulation strategies in interferometry
Authors: Bethge Jens , Steinmeyer Günter
Published: July 2008

The performance of two different numerical frequency demodulation strategies for evaluating sampled fringe patterns in interferometric applications and optics is discussed. Namely, these techniques involve traditional Fourier filtering techniques and a strategy based on the Gabor wavelets. While the latter is found to be more precise, it is generally difficult to implement wavelet-based frequency demodulation with equal performance as methods based on the fast Fourier transform. Here, we demonstrate a specialized fast wavelet algorithm that outperforms Fourier-based strategies for array sizes up to a few thousand data points and is yet more precise. The performance is investigated in numerical examples, indicating that the required choice of a global filter bandwidth is one of the main problems of the Fourier filtering strategy. Wavelet frequency demodulation, in contrast, always appears to perform slightly better, does not require judicious choice of filtering, and can often be made equally fast without loss of precision. Finally, applying this new algorithm to an ideal sinusoidal signal without noise, the precision of the numerical frequency demodulation is increased by nearly two orders of magnitude.
Collisionality dependence of the quasilinear particle flux due to microinstabilities
Authors: Fülöp T. , Pusztai I. , Helander P.
Published: July 2008

The collisionality dependence of the quasilinear particle flux due to the ion temperature gradient (ITG) and trapped electron mode (TEM) instabilities is studied by including electron collisions modeled by a pitch-angle scattering collision operator in the gyrokinetic equation. The inward transport due to ITG modes is caused mainly by magnetic curvature and thermodiffusion and can be reversed as electron collisions are introduced, if the plasma is far from marginal stability. However, if the plasma is close to marginal stability, collisions may even enhance the inward transport. The sign and the magnitude of the transport are sensitive to the form of the collision operator, to the magnetic drift normalized to the real frequency of the mode, and to the density and temperature scale lengths. These analytical results are in agreement with previously published gyrokinetic simulations. Unlike the ITG-driven flux, the TEM-driven flux is expected to be outwards for conditions far from marginal stability and inwards otherwise.
Absolute calibration of photostimulable image plate detectors used as (0.5–20MeV) high-energy proton detectors
Authors: Mančić A. , Fuchs J. , Antici P. , Gaillard S. A. , Audebert P.
Published: July 2008

In this paper, the absolute calibration of photostimulable image plates (IPs) used as proton detectors is presented. The calibration is performed in a wide range of proton energies (0.5–20MeV) by exposing simultaneously the IP and calibrated detectors (radiochromic films and solid state detector CR39) to a source of broadband laser-accelerated protons, which are spectrally resolved. The final result is a calibration curve that enables retrieving the proton number from the IP signal.
Resonance-mode effect on microcantilever mass-sensing performance in air
Authors: Xia Xiaoyuan , Li Xinxin
Published: July 2008

This research investigates the air drag damping effect of the micromachined cantilevers in different resonance modes on the quality factor, which are operated in ambient air. Based on a simplified dish-string model for air drag force acting on the resonant cantilever, the air drag damping properties of the cantilevers vibrating in different modes are analyzed with theoretic vibration mechanics, which is complemented and further confirmed with finite-element simulation. Four kinds of integrated cantilevers, which resonate in the first flexural mode, the second flexural mode, the first torsional mode, and the second torsional mode, respectively, are designed and fabricated by using micromachining techniques. Finally, biomolecular sensing experiments are carried out to verify the theoretical results obtained before. From both the modeling and experimental results, it can be seen that damping characteristics of the torsional cantilever resonators are generally better than that of the flexural ones, and quality factor of the cantilever resonator in a higher-frequency mode is always superior to that in a lower-frequency one. Among the four kinds of microcantilever resonators operated in our experiments, the one operated in the second flexural modes exhibits the highest Q factor and the best biomass sensing performance.
An alternative method for the measurement of the mechanical impulse of a vertically directed blast
Authors: Turner Geoffrey R.
Published: July 2008

An alternative method for the measurement of the total mechanical impulse of a vertically directed blast due to an explosive charge is presented. The method differs from apparatus that employ a vertically displaced mass (similar in principle to the ballistic pendulum) in that a relatively compact spring-damper system is employed to constrain the movement of the mass. The mechanical impulse is determined by integrating, with respect to time, the net force applied to the spring-damper system. The details of an explosive impulse measuring instrument rated to 12kNs are presented.
Laser ablation source for formation and deposition of size-selected metal clusters
Authors: Vučković S. , Svanqvist M. , Popok V. N.
Published: July 2008

This work describes construction of a source and optimisation of its parameters for production of cluster ion beams using material ablation by the second harmonic of a Nd:YAG laser (532nm). The influence of different source parameters such as carrier gas pressure, laser power, delay time between gas, and laser pulses as well as nozzle configuration on the cluster formation are studied. For the current experiments the laser ablation cluster source was optimized for production of Con+ cluster ions. Clusters with n up to 150 atoms are registered by a time-of-flight mass spectrometer. Deposition of size-selected Co50+ clusters with kinetic energies in the interval of 250–4850eV/cluster on highly ordered pyrolytic graphite is studied. At the highest impact energies the clusters are implanted. Craters and well-like structures can be seen by scanning tunneling microscopy at impact spots. A decrease in cluster kinetic energy leads to formation of bumplike structures which probably represent damaged graphite areas with incorporated Co atoms. Further decrease in the cluster impact energy to the level of 450–250eV/cluster creates condition for so-called cluster pinning when the cluster constituents are intact but the energy transferred to the graphite is still enough to produce radiation defects to which the cluster is bound.
Thermoelectrics in an array of molecular junctions
Authors: Müller K.-H.
Published: July 2008

The room temperature thermoelectric properties of a three-dimensional array of molecular junctions are calculated. The array is composed of n-doped silicon nanoparticles where the surfaces are partially covered with polar molecules and the nanoparticles are bridged by trans-polyacetylene molecules. The role of the polar molecules is to reduce the band bending in the n-doped silicon nanoparticles and to shift the electronic resonances of the bridging molecules to the nanoparticle conduction band edges where the molecular resonances act as electron energy filters. The transmission coefficients of the bridging molecules that appear in the formulas for the Seebeck coefficient, the electrical conductance, and the electronic thermal conductance, are calculated using the nonequilibrium Green’s function technique. A simple tight-binding Hamiltonian is used to describe the bridging molecules, and the self-energy term is calculated using the parabolic conduction band approximation. The dependencies of the thermoelectric properties of the molecular junctions on the silicon doping concentration and on the molecule-nanoparticle coupling are discussed. The maximal achievable thermoelectric figure of merit ZT of the array is estimated as a function of the phononic thermal conductance of the bridging molecules and the doping of the nanoparticles. The power factor of the array is also calculated. For sufficiently small phononic thermal conductances of the bridging molecules, very high ZT values are predicted.
Photovoltaic effect in semiconductor nanocrystals embedded into amorphous silicon p-n junction
Authors: Krivoshlykov Sergei G. , Rupasov Valery I.
Published: July 2008

We report experimental demonstration of photovoltaic effect in nanocomposite amorphous silicon p-i-n junction comprising a thin film of lead selenide (PbSe) nanocrystals deposited on a p-type crystalline silicon wafer and overcoated with n-type layer of hydrogenated amorphous silicon.
Model of a truncated fast rotating flow at infinite Reynolds number
Authors: Bourouiba L.
Published: July 2008

The purpose of this study is to examine the strongly rotating limit of a turbulent flow theoretically and numerically. The goal is to verify the predictions of asymptotic theories. Given the limitations of experimental and dissipative numerical approaches to this problem, we use classical equilibrium statistical mechanics. We apply the statistical mechanics approach to the inviscid truncated model of strongly rotating turbulence (in the small Rossby number range) and derive the theoretical spectra of the decoupled model. We use numerical simulations to complement these derivations and examine the relaxation to equilibrium of the inviscid unforced truncated rotating turbulent system for different sets of initial conditions. We separate our discussion into two time domains: the discussion of the decoupled phase with time below a threshold time t⋆, for which a new set of invariants S are identified, and the coupled phase with a time beyond t⋆, for which the quantities S are no longer invariants. We obtain a numerical evaluation of t⋆ which is coherent with the theoretical asymptotic expansions. We examine if the quantities S play a constraining role on the coupled dynamics beyond t>t⋆. We find that the theoretical statistical predictions in the decoupled phase capture the horizontal dynamics of the flow. In the coupled phase, the invariants S are found to still play a constraining role on the short-timescale horizontal dynamics of the flow. These results are discussed in the larger context of previous rotating turbulence studies.
Generalized Kelvin equation and pseudospinodal in nucleation theory
Authors: Kalikmanov V. I.
Published: July 2008

The classical Kelvin equation, relating the size of the critical cluster to the supersaturation, is inadequate for very small, molecular-sized clusters emerging at deep quenches observed in recent nucleation experiments. Using statistical mechanical considerations, we propose a generalization of the Kelvin equation applicable up to the vicinity of the pseudospinodal, where the nucleation barrier is ∼kBT. The supersaturation at the pseudospinodal is expressed in terms of the second virial coefficient. It is shown that near the pseudospinodal the critical cluster size is close to the coordination number in the liquid phase. Comparisons with computer simulations are presented.
Magnetic field tuning of coplanar waveguide resonators
Authors: Healey J. E. , Lindström T. , Colclough M. S. , Muirhead C. M. , Tzalenchuk A. Ya.
Published: July 2008

We describe measurements on microwave coplanar resonators designed for quantum bit experiments. Resonators have been patterned onto sapphire and silicon substrates, and quality factors in excess of a million have been observed. The resonant frequency shows a high sensitivity to magnetic field applied perpendicular to the plane of the film, with a quadratic dependence for the fundamental, second, and third harmonics. Frequency shift of hundreds of linewidths can be obtained with no change in the quality factor.
Competitive antiferromagnetic and ferromagnetic coupling in a CrSe/Fe/GaAs(111)B structure
Authors: Wang C. , Zhang B. , You B. , Lok S. K. , Chan S. K. , Zhang X. X. , Wong G. K. L. , Sou I. K.
Published: July 2008

A novel transition from the negative exchange bias (NEB) to the positive exchange bias (PEB), due to coexistent and competitive ferromagnetic and antiferromagnetic coupling in a molecular-beam-expitaxy-grown CrSe/Fe/GaAs(111)B structure, is described. The source of the unusual PEB effect was found to originate from the interface at the hetero-junction of Fe/GaAs(111)B while the NEB effect resulted from the CrSe/Fe bilayer structure. Phenomenological models are presented to explain the mechanism of the PEB effect and the varying asymmetry of the magnetic hysteresis of this structure as a function of the measured temperature.
The role of strain in hydrogenation induced cracking in Si∕Si1−xGex∕Si structures
Authors: Shao Lin , Di Zengfeng , Lin Yuan , Jia Q. X. , Wang Y. Q. , Nastasi M. , Thompson Phillip E. , David Theodore N. , Chu Paul K.
Published: July 2008

Hydrogenation induced cracking in molecular beam epitaxy grown Si∕Si1−xGex∕Si heterostructures is studied. The Si1−xGex layer buried between an ∼200nm thick Si capping layer and the Si substrate is ∼5nm thick. After plasma hydrogenation, long range H migration and H trapping at the Si1−xGex layer are observed. With increasing Ge concentrations, the amount of H trapping increases, cracking along the Si1−xGex layer is smoother, and fewer defects are formed in the Si capping layer. The study suggests maximizing the interfacial strain to achieve the smoothest cracking with minimized radiation damage for ultrathin silicon-on-insulator technology.
Improvement in aligned GaN nanowire growth using submonolayer Ni catalyst films
Authors: Li Qiming , Wang George T.
Published: July 2008

We report a route to ultrahigh-density and highly aligned single-crystalline GaN nanowires on sapphire by employing ultrathin Ni catalyst films with submonolayer thickness. The nanowire density and the degree of alignment were found to be highly sensitive to changes in the Ni catalyst film thickness below 1nm, a regime rarely explored in catalyzed nanowire growth before. For submonolayer Ni films on sapphire, high activation energy for Ni diffusion on sapphire surface is attributed to the formation of high-density and ultrasmall Ni islands with a narrow size distribution, which in turn leads to high-density and highly aligned GaN nanowires.
Adaptive polymer particles
Authors: Kalaitzidou Kyriaki , Crosby Alfred J.
Published: July 2008

Adaptable polymer particles that can change geometry, flow characteristics, and adsorption properties upon the stimulation of an environmental change, such as temperature, are fabricated by utilizing the residual stress developed at the interface of a bilayer. We propose a phase diagram that can be used to predict the shape and size of the adaptive polymer particles as a function of the material modulus, thickness ratio, and the bilayer’s lateral dimensions. The materials used are gold/titanium and polydimethylsiloxane, but the method is applicable to a wide range of material combinations. Initial demonstrations of this responsive control and its impact on properties of the adaptive polymer particles are also presented.
Analytical model of spin-polarized semiconductor lasers
Authors: Gøthgen Christian , Oszwałdowski Rafał , Petrou Athos , Žutić Igor
Published: July 2008

We formulate an analytical model for semiconductor lasers with injection (pump) of spin-polarized electrons, allowing us to systematically investigate different operating regimes. We demonstrate that the maximum threshold reduction by electrically pumped spin-polarized carriers is larger than previously thought possible and, surprisingly, can be enhanced by ultrafast spin relaxation of holes. We reveal how different modes of carrier recombination directly affect the threshold reduction. Neither spin-up nor spin-down electron populations are separately clamped (pinned) near the threshold, where such lasers can act as effective nonlinear filters of circularly polarized light, owing to their spin-dependent gain.
Very low-frequency radio waves drain Earth’s inner radiation belt of satellite-killing electrons
Authors: Day Charles
Published: July 2008

A high-altitude nuclear explosion would swell the radiation belt and imperil the global positioning system and other satellites. VLF transmissions could forestall the damage.
X-ray outburst reveals a supernova before it explodes
Authors: Schwarzschild Bertram
Published: July 2008

Long predicted but never before seen, the x-ray harbinger let observers record the supernova’s early light in unprecedented detail.
Will desperate climates call for desperate geoengineering measures?
Authors: Levi Barbara Goss
Published: July 2008

Earth scientists ponder the wisdom of large-scale efforts to counter global warming.
Geoscience research for our energy future
Authors: Depaolo Donald J. , Orr Franklin M.
Published: July 2008

Understanding the complex interactions between pressurized fluids and porous rock is a key prerequisite to the safe sequestration of carbon dioxide and radioactive waste.
IL-33 exacerbates antigen-induced arthritis by activating mast cells
Authors: Xu Damo , Jiang Hui-Rong , Kewin Peter , Li Yubin , Mu Rong , Fraser Alasdair R. , Pitman Nick , Kurowska-Stolarska Mariola , McKenzie Andrew N. J. , McInnes Iain B. , Liew Foo Y.
Published: July 2008

IL-33, a cytokine of the IL-1 family, is closely associated with type II T cell responses. Here, we report an unexpected proinflammatory role of IL-33 in inflammatory arthritis. IL-33 was expressed in synovial fibroblasts from patients with rheumatoid arthritis (RA). Expression was markedly elevatedin vitroby inflammatory cytokines. Mice lacking ST2, the IL-33 receptor α-chain, developed attenuated collagen-induced arthritis (CIA) and reducedex vivocollagen-specific induction of proinflammatory cytokines (IL-17, TNFα, and IFNγ), and antibody production. Conversely, treatment of wild-type (WT) but not ST2−/−mice with IL-33 exacerbated CIA and elevated production of both proinflammatory cytokines and anti-collagen antibodies. Mast cells expressed high levels of ST2 and responded directly to IL-33 to produce a spectrum of inflammatory cytokines and chemokinesin vitro. In vivo, IL-33 treatment exacerbated CIA in ST2−/−mice engrafted with mast cells from WT but not from ST2−/−mice. Disease exacerbation was accompanied by elevated expression levels of proinflammatory cytokines. Our results demonstrate that IL-33 is a critical proinflammatory cytokine for inflammatory joint disease that integrates fibroblast activation with downstream immune activation mainly via an IL-33-driven, mast-cell-dependent pathway. Thus, this IL-1 superfamily member represents a therapeutic target for RA.
Eutrophication of lakes cannot be controlled by reducing nitrogen input: Results of a 37-year whole-ecosystem experiment
Authors: Schindler David W. , Hecky R. E. , Findlay D. L. , Stainton M. P. , Parker B. R. , Paterson M. J. , Beaty K. G. , Lyng M. , Kasian S. E. M.
Published: July 2008

Lake 227, a small lake in the Precambrian Shield at the Experimental Lakes Area (ELA), has been fertilized for 37 years with constant annual inputs of phosphorus and decreasing inputs of nitrogen to test the theory that controlling nitrogen inputs can control eutrophication. For the final 16 years (1990–2005), the lake was fertilized with phosphorus alone. Reducing nitrogen inputs increasingly favored nitrogen-fixing cyanobacteria as a response by the phytoplankton community to extreme seasonal nitrogen limitation. Nitrogen fixation was sufficient to allow biomass to continue to be produced in proportion to phosphorus, and the lake remained highly eutrophic, despite showing indications of extreme nitrogen limitation seasonally. To reduce eutrophication, the focus of management must be on decreasing inputs of phosphorus.
A methodological approach to the development of RFID supply chain projects
Authors: Bottani Eleonora , Hardgrave Bill , Volpi Andrea
Published: July 2008

The interest in, and adoption of, radio frequency identification (RFID) in the supply chain continues to grow. In the past few years, major initiatives from companies such as Wal-Mart, Metro, and Marks & Spencer have provided much-needed insight into the potential uses of RFID, thus providing the impetus for other companies to investigate RFID. Consequently, reports of ‘pilot’ projects by many different companies are on the increase. However, the development of an RFID project is a complex task, requiring the involvement of many different parties with a variety of skill sets. Successfully managing such complex projects requires a clear definition of steps and activities. Unfortunately, this issue is only partially embraced in literature. Thus the purpose of this paper is to provide a methodology to help companies in developing and managing an RFID project. The framework provided in this paper is grounded on available literature and from the authors’ personal experiences in managing several projects through their RFID laboratories.
Characterization of edge turbulence in relation to edge magnetic field configuration in Ohmic L-mode plasmas in the Mega Amp Spherical Tokamak
Authors: Hnat B. , Dudson B.D. , Dendy R.O. , Counsell G.F. , Kirk A.
Published: July 2008

Ion saturation current (I
sat) measurements of edge plasma turbulence are analysed for six MAST L-mode plasmas that differ primarily in their edge magnetic field configurations. The analysis techniques are designed to capture the strong nonlinearities of the datasets. First, absolute moments of the data are examined to obtain accurate values of scaling exponents. This confirms dual scaling behaviour in all samples, with the temporal scale τ ≈ 40–60 µs separating the two regimes. Strong universality is then identified in the functional form of the probability density function (PDF) for I
sat fluctuations, which is well approximated by the Fréchet distribution on temporal scales τ ⩽ 40 µs. For temporal scales τ > 40 µs, the PDFs appear to converge to the Gumbel distribution, which has been previously identified as a universal feature of many other complex phenomena. The optimal fitting parameters k = 1.15 for Fréchet and a = 1.35 for Gumbel provide a simple quantitative characterization of the full spectrum of fluctuations. It is concluded that, to good approximation, the properties of the edge turbulence are independent of the edge magnetic field configuration.
Nuclear Cathepsin F Regulates Activation Markers in Rat Hepatic Stellate Cells
Authors: Maubach Gunter , Lim Michelle Chin Chia , Zhuo Lang
Published: July 2008

Activation of hepatic stellate cells during liver fibrosis is a major event facilitating an increase in extracellular matrix deposition. The up-regulation of smooth muscle α-actin and collagen type I is indicative of the activation process. The involvement of cysteine cathepsins, a class of lysosomal cysteine proteases, has not been studied in conjunction with the activation process of hepatic stellate cells. Here we report a nuclear cysteine protease activity partially attributed to cathepsin F, which co-localizes with nuclear speckles. This activity can be regulated by treatment with retinol/palmitic acid, known to reduce the hepatic stellate cell activation. The treatment for 48 h leads to a decrease in activity, which is coupled to an increase in cystatin B and C transcripts. Cystatin B knockdown experiments during the same treatment confirm the regulation of the nuclear activity by cystatin B. We demonstrate further that the inhibition of the nuclear activity by E-64d, a cysteine protease inhibitor, results in a differential regulation of smooth muscle α-actin and collagen type I transcripts. On the other hand, cathepsin F small interfering RNA transfection leads to a decrease in nuclear activity and a transcriptional down-regulation of both activation markers. These findings indicate a possible link between nuclear cathepsin F activity and the transcriptional regulation of hepatic stellate cell activation markers.
Use of simulated data as a tool for testing the performance of diversity indices in response to an organic enrichment event
Authors: Barry Jon , Rees Hubert L.
Published: July 2008

Barry, J., and Rees, H. L. 2008. Use of simulated data as a tool for testing the performance of diversity indices in response to an organic enrichment event. – ICES Journal of Marine Science, 65: 1456–1461. We demonstrate how data on macrobenthic species numbers and abundance after an organic enrichment event can be simulated using the empirical Pearson–Rosenberg model in combination with further plausible ecological assumptions. The simulations were programmed in the statistical package R, using an ecological framework that included classification of species into opportunistic, tolerant, and sensitive types, together with probabilities for the occurrence of these types at any particular point in the event history. The simulations also included assumptions about the dominance of species types. The exercise was successful in that realistic, simulated datasets could be produced quickly and, because of the stochastic nature of parts of the simulation process, repeat simulations allowed variation of selected diversity indices calculated on the series to be assessed. The approach could provide a useful tool to evaluate both existing and new indicators.
Biological indicators of disturbance at a dredged-material disposal site in Liverpool Bay, UK: an assessment using time-series data
Authors: Whomersley Paul , Ware Suzanne , Rees Hubert L. , Mason Claire , Bolam Thi , Huxham Mark , Bates Helen
Published: July 2008

Whomersley, P., Ware, S., Rees, H. L., Mason, C., Bolam, T., Huxham, M., and Bates, H. 2008. Biological indicators of disturbance at a dredged-material disposal site in Liverpool Bay, UK: an assessment using time-series data. – ICES Journal of Marine Science, 65: 1414–1420. The development of reliable indicators of disturbance in the marine environment is essential because of increasing anthropogenic pressures and the need for more effective regulation. Our objective was to evaluate 13 nationally and internationally recommended metrics, using a large dataset derived from annual (1996–2003) macro-invertebrate infaunal surveys of a Liverpool Bay dredged-material disposal site. The primary and derived univariate metrics, along with multivariate derivations, were assessed and scored against six selection criteria. Metrics that did not correlate with the pressure indicator (the annual quantity of material disposed of) were discounted from further analysis. Of the 13 metrics evaluated, only measures of species number and Margalef’s species richness index were significantly correlated. Although assemblage types were significantly different between stations, common time patterns were observed, indicating that underlying larger scale, low-frequency events may have influenced assemblage development at all locations.
Substantial biases in ultra-short read data sets from high-throughput DNA sequencing
Authors: Dohm Juliane C. , Lottaz Claudio , Borodina Tatiana , Himmelbauer Heinz
Published: July 2008

Novel sequencing technologies permit the rapid production of large sequence data sets. These technologies are likely to revolutionize genetics and biomedical research, but a thorough characterization of the ultra-short read output is necessary. We generated and analyzed two Illumina 1G ultra-short read data sets, i.e. 2.8 million 27mer reads from a Beta vulgaris genomic clone and 12.3 million 36mers from the Helicobacter acinonychis genome. We found that error rates range from 0.3% at the beginning of reads to 3.8% at the end of reads. Wrong base calls are frequently preceded by base G. Base substitution error frequencies vary by 10- to 11-fold, with A > C transversion being among the most frequent and C > G transversions among the least frequent substitution errors. Insertions and deletions of single bases occur at very low rates. When simulating re-sequencing we found a 20-fold sequencing coverage to be sufficient to compensate errors by correct reads. The read coverage of the sequenced regions is biased; the highest read density was found in intervals with elevated GC content. High Solexa quality scores are over-optimistic and low scores underestimate the data quality. Our results show different types of biases and ways to detect them. Such biases have implications on the use and interpretation of Solexa data, for de novo sequencing, re-sequencing, the identification of single nucleotide polymorphisms and DNA methylation sites, as well as for transcriptome analysis.
SARANA: language, compiler and run-time system support for spatially aware and resource-aware mobile computing
Authors: Hari Pradip , Ko Kevin , Koukoumidis Emmanouil , Kremer Ulrich , Martonosi Margaret , Ottoni Desiree , Peh Li-Shiuan , Zhang Pei
Published: July 2008

Increasingly, spatial awareness plays a central role in many distributed and mobile computing applications. Spatially aware applications rely on information about the geographical position of compute devices and their supported services in order to support novel functionality. While many spatial application drivers already exist in mobile and distributed computing, very little systems research has explored how best to program these applications, to express their spatial and temporal constraints, and to allow efficient implementations on highly dynamic real-world platforms. This paper proposes the SARANA system architecture, which includes language and run-time system support for spatially aware and resource-aware applications. SARANA allows users to express spatial regions of interest, as well as trade-offs between quality of result (QoR), latency and cost. The goal is to produce applications that use resources efficiently and that can be run on diverse resource-constrained platforms ranging from laptops to personal digital assistants and to smart phones. SARANA's run-time system manages QoR and cost trade-offs dynamically by tracking resource availability and locations, brokering usage/pricing agreements and migrating programs to nodes accordingly. A resource cost model permeates the SARANA system layers, permitting users to express their resource needs and QoR expectations in units that make sense to them. Although we are still early in the system development, initial versions have been demonstrated on a nine-node system prototype.