bluuebunny/crossref_metadata_2025 huggingface dataset:
The relation between order of acquisition, segmental frequency and function: the case of word-initial consonants in Dutch
Authors: VAN SEVEREN LIEVE , GILLIS JORIS J. M. , MOLEMANS INGE , VAN DEN BERG RENATE , DE MAEYER SVEN , GILLIS STEVEN
Published: August 2012

The impact of input frequency (IF) and functional load (FL) of segments in the ambient language on the acquisition order of word-initial consonants is investigated. Several definitions of IF/FL are compared and implemented. The impact of IF/FL and their components are computed using a longitudinal corpus of interactions between thirty Dutch-speaking children (age range: 0 ; 6–2 ; 0) and their primary caretaker(s). The corpus study reveals significant correlations between IF/FL and acquisition order. The highest predictive values are found for the token frequency of segments, and for FL computed on minimally different word types in child-directed speech. Although IF and FL significantly correlate, they do have a different impact on the order of acquisition of word-initial consonants. When the impact of IF is partialed out, FL still has a significant correlation with acquisition order. The reverse is not true, suggesting that the acquisition of word-initial consonants is mainly influenced by their discriminating function.
Simulation Research on Gravity-Geomagnetism Combined Aided Underwater Navigation
Authors: Zheng Hui , Wang Hubiao , Wu Lin , Chai Hua , Wang Yong
Published: July 2012

Gravity Aided Navigation (GravAN) and Geomagnetism Aided Navigation (GeomAN) are two methods for correcting Inertial Navigation System (INS) errors of Autonomous Underwater Vehicles (AUVs) without compromising the AUV mission. One requirement for applying these methods is the relatively large field feature variations along the navigation trajectory. But in some regions with small gravity or geomagnetic variation, it is very difficult to achieve a reliable result solely by GravAN or GeomAN. If these two methods were combined, gravity and geomagnetism information could be complementary and the aided navigation ability could potentially be improved, especially in those regions when neither method is valid. Based on that concept, a Gravity and Geomagnetism Combined Aided Navigation (GGCAN) method is consequently proposed in this paper as a possible solution. The Gravity Anomaly Grid (GAG2) and Earth Geomagnetic Anomaly Grid (EMAG2) are utilized as the background databases, and then a Multiple Model Adaptive Estimation (MMAE) is adopted to obtain an optimal estimated navigation position. Furthermore, an Optimal Weight Allocation Principle (OWAP) is introduced to the combined GravAN and GeomAN methods, together with a weighted average. In simulation, two special regions in the Western Pacific Ocean were chosen to test the proposed method. The results show that GGCAN can improve the position success rate and reduce the error, compared to GravAN or GeomAN. Results indicate that the GGCAN method proposed in this study is able to improve the accuracy and reliability of an aided navigation system.
God is Not Dead or Violent: The Catholic Church, Just War, and the “Resurgence” of Religion
Authors: Chu Lan T.
Published: July 2012

While scholars have recognized a resurgence of religion, their focus mainly has been on religion's more violent aspects, overlooking its peaceful capacities and effects. This oversight is due in part to the lack of theoretical rigor when it comes to the study of politics and religion. Using the Catholic Church's opposition to the United States’ 2003 war in Iraq, this article highlights the political significance of religion's moral, symbolic voice, which is as important as the hard power that has traditionally dominated international relations. The post-Vatican II Catholic Church's modern articulation of human dignity and interpretation of just war theory challenges both scholars and policymakers to utilize the peaceful, diplomatic methods that international relations theory and practitioners have made available. Religion's role in politics, therefore, can be one that is supportive of modern political societies and it need not be violent.
Eye Movements and Practice Effects in the Attentional Dwell Time Paradigm
Authors: Petersen Anders , Kyllingsbæk Søren
Published: August 2012

In the attentional dwell time paradigm by Duncan, Ward, and Shapiro (1994) , two backward masked targets are presented at different spatial locations and separated by a varying time interval. Results show that report of the second target is severely impaired when the time interval is less than 500 ms which has been taken as a direct measure of attentional dwell time in human vision. However, we show that eye movements may have confounded the estimate of the dwell time and that the measure may not be robust as previously suggested. The latter is supported by evidence suggesting that intensive training strongly attenuates the dwell time because of habituation to the masks. Thus, this article points to eye movements and masking as two potential methodological pitfalls that should be considered when using the attentional dwell time paradigm to investigate the temporal dynamics of attention.
Global calcite cycling constrained by sediment preservation controls
Authors: Dunne John P. , Hales Burke , Toggweiler J. R.
Published: July 2012

We assess the global balance of calcite export through the water column and burial in sediments as it varies regionally. We first drive a comprehensive 1‐D model for sediment calcite preservation with globally gridded field observations and satellite‐based syntheses. We then reformulate this model into a simpler five‐parameter box model, and combine it with algorithms for surface calcite export and water column dissolution for a single expression for the vertical calcite balance. The resulting metamodel is optimized to fit the observed distributions of calcite burial flux. We quantify the degree to which calcite export, saturation state, organic carbon respiration, and lithogenic sedimentation modulate the burial of calcite. We find that 46% of burial and 88% of dissolution occurs in sediments overlain by undersaturated bottom water with sediment calcite burial strongly modulated by surface export. Relative to organic carbon export, we find surface calcite export skewed geographically toward relatively warm, oligotrophic areas dominated by small, prokaryotic phytoplankton. We assess century‐scale projected impacts of warming and acidification on calcite export, finding high sensitive to inferred saturation state controls. With respect to long‐term glacial cycling, our analysis supports the hypothesis that strong glacial abyssal stratification drives the lysocline toward much closer correspondence with the saturation horizon. Our analysis suggests that, over the transition from interglacial to glacial ocean, a resulting ∼0.029 PgC a−1decrease in deep Atlantic, Indian and Southern Ocean calcite burial leads to slow increase in ocean alkalinity until Pacific mid‐depth calcite burial increases to compensate.
Absolute plate motions in a reference frame defined by moving hot spots in the Pacific, Atlantic, and Indian oceans
Authors: Doubrovine Pavel V. , Steinberger Bernhard , Torsvik Trond H.
Published: August 2012

We defined a new global moving hot spot reference frame (GMHRF), using a comprehensive set of radiometric dates from arguably the best‐studied hot spot tracks, refined plate circuit reconstructions, a new plate polygon model, and an iterative approach for estimating hot spot motions from numerical models of whole mantle convection and advection of plume conduits in the mantle flow that ensures their consistency with surface plate motions. Our results show that with the appropriate choice of a chain of relative motion linking the Pacific plate to the plates of the Indo‐Atlantic hemisphere, the observed geometries and ages of the Pacific and Indo‐Atlantic hot spot tracks were accurately reproduced by a combination of absolute plate motion and hot spot drift back to the Late Cretaceous (∼80 Ma). Similarly good fits were observed for Indo‐Atlantic tracks for earlier time (to ∼130 Ma). In contrast, attempts to define a fixed hot spot frame resulted in unacceptable misfits for the Late Cretaceous to Paleogene (80–50 Ma), highlighting the significance of relative motion between the Pacific and Indo‐Atlantic hot spots during this period. A comparison of absolute reconstructions using the GMHRF and the most recent global paleomagnetic frame reveals substantial amounts of true polar wander at rates varying between ∼0.1°/Ma and 1°/Ma. Two intriguing, nearly equal and antipodal rotations of the Earth relative to its spin axis are suggested for the 90–60 Ma and 60–40 Ma intervals (∼9° at a 0.3–0.5°/Ma rate); these predictions have yet to be tested by geodynamic models.
Officials mark Landsat fortieth anniversary with look toward the future
Authors: Showstack Randy
Published: July 2012

With the first Landsat satellite having launched 40 years ago and the Landsat Data Continuity Mission (LDCM) on track to launch from Vandenberg Air Force Base, Calif., on 11 February 2013, officials from several U.S. federal science agencies took stock of some of the accomplishments of Landsat (the world's longest running Earth‐observing satellite program), announced new tools for scientists working with Landsat data, and discussed some of the challenges facing the program during a 23 July briefing at the Newseum in Washington, D. C.
Improving Antarctic infrastructure
Authors: Showstack Randy
Published: July 2012

Noting that U.S. activities in Antarctica “are very well managed but suffer from an aging infrastructure, lack of a capital budget, and the effects of operating in an extremely unforgiving environment,” a 23 July report from the U.S. Antarctic Program Blue Ribbon Panel recommends a number of measures to improve the infrastructure, logistics, and other concerns. The panel's recommendations include continued use of the McMurdo, South Pole, and Palmer stations as the primary U.S. science and logistics hubs in Antarctica—because there are no reasonable alternatives, according to the panel—while upgrading or replacing some facilities, restoring the U.S. polar ocean feet, implementing state of‐the‐art logistics and transportation support, and establishing a long‐term facilities capital plan and budget for the U.S. Antarctic Program. “The essence of our findings is that the lack of capital budgeting has placed operations at McMurdo, and to a somewhat lesser extent at Palmer Station, in unnecessary jeopardy—at least in terms of prolonged inefficiency due to deteriorating or otherwise inadequate physical assets,” the panel wrote in the cover letter accompanying the report entitled, More and Better Science in Antarctica Through Increased Logistical Effectiveness. “The Antarctica Blue Ribbon Panel encourages us to take a hard look at how we support Antarctic science and to make the structural changes, however difficult in the current fiscal environment, that will allow us to do more science in the future,” said U.S. National Science Foundation (NSF) Director Subra Suresh.
Seismic refraction analysis: The path forward
Authors: Haines Seth S. , Zelt Colin , Doll William
Published: July 2012

Seismic Refraction Methods: Unleashing the Potential and Understanding the Limitations; Tucson, Arizona, 29 March 2012 A workshop focused on seismic refraction methods took place on 29 May 2012, associated with the 2012 Symposium on the Application of Geophysics to Engineering and Environmental Problems. This workshop was convened to assess the current state of the science and discuss paths forward, with a primary focus on near‐surface problems but with an eye on all applications. The agenda included talks on these topics from a number of experts interspersed with discussion and a dedicated discussion period to finish the day. Discussion proved lively at times, and workshop participants delved into many topics central to seismic refraction work.
Abyssal plains heat exchange could explain global deficit
Authors: Schultz Colin
Published: July 2012

When researchers measure the amount of heat flowing conductively from the seafloor to the ocean waters and then compare that value against a theoretical prediction of that heat loss, they observe that the global average measured heat flow is lower than expected. Researchers think that advection, a heat transfer mechanism that is difficult to measure, makes up this difference between predicted and observed heat exchange. They suggest that as seawater circulates through the permeable upper layers of the seafloor crust, driven by a thermal gradient, the water accumulates heat, drawing it into the ocean. Scientists have recently proposed that seafloor sediment plays an important role in controlling the geometry of such intraocean crust circulation. In the abyssal plains, the accumulation of millions of years' worth of low permeability sediment limits direct contact between the ocean and the crust. Where the sediment is thin or absent—for example, at outcrops—water is thought to be able to move between the ocean and the crust. Scientists propose that seawater can travel through the crust for tens of kilometers beneath the sediment, moving laterally from outcrop to outcrop.
Glacier volume‐area relation for high‐order mechanics and transient glacier states
Authors: Adhikari S. , Marshall S. J.
Published: July 2012

Glacier volume is known for less than 0.1% of the world's glaciers, but this information is needed to quantify the impacts of glacier changes on global sea level and regional water resources. Observations indicate a power‐law relation between glacier area and volume, with an exponentγ≈ 1.36. Through numerical simulations of 3D, high‐order glacier mechanics, we demonstrate how different topographic and climatic settings, glacier flow dynamics, and the degree of disequilibrium with climate systematically affect the volume‐area relation. We recommend more accurate scaling relations through characterization of individual glacier shape, slope and size. An ensemble of 280 randomly‐generated valley glaciers spanning a spectrum of plausible glaciological conditions yields a steady‐state exponentγ= 1.46. This declines to 1.38 for glaciers that are 100 years into a sustained retreat, which corresponds exceptionally well with the observed value for present‐day glaciers.
Coupling of evaporative fluxes from drying porous surfaces with air boundary layer: Characteristics of evaporation from discrete pores
Authors: Shahraeeni Ebrahim , Lehmann Peter , Or Dani
Published: July 2012

Prediction of drying rates from porous media remains a challenge due to complex interactions between ambient conditions and porous medium properties. Evaporation from a gradually drying porous surface across air boundary layer exhibits nonlinear behavior due to enhanced diffusive fluxes from increasingly isolated active pores. These nonlinear interactions were quantified by modeling evaporation from surfaces composed of individual pores considering surface water content dynamics and internal transport within the medium. Wind tunnel experiments show that in contrast with nearly constant evaporation rates obtained at low atmospheric demand (typically <5 mm/d), evaporation fluxes under high atmospheric demand (high air velocities) exhibit a continuous decrease with surface drying even in the absence of internal capillary flow limitations. The isolated pore evaporation model captures surface drying dynamics for a range of atmospheric demands associated with air velocity and boundary layer thickness. As a surface dries under low atmospheric demand (low air speed, thick boundary layer), the remaining active pores become gradually isolated with a conforming vapor concentration field becoming increasingly three‐dimensional thereby enhancing evaporative flux per pore. Such enhancement may fully compensate for reduced evaporative surface area leading to observed constant evaporation rate under low demand. For high evaporative demand, limitations to vapor field configuration within thin boundary layer limit flux compensation efficiency and leads to decreasing evaporative flux with surface drying irrespective of internal supply capacity. The model provides new insights into the intrinsic links between surface properties and atmospheric conditions in determining a range of evaporative dynamics for similar surface wetness conditions.
Tone Discrimination as a Window Into Acoustic Perceptual Deficits in Parkinson’s Disease
Authors: Troche Joshua , Troche Michelle S. , Berkowitz Rebecca , Grossman Murray , Reilly Jamie
Published: July 2012

Purpose

Deficits in auditory perception compromise a range of linguistic processes in persons with Parkinson’s disease (PD), including speech perception and sensitivity to affective and linguistic prosody. An unanswered question is whether this deficit exists not only at the level of speech perception, but also at a more pervasive level of auditory perception. It is possible that PD produces a selective impairment in the perception of a salient acoustic feature such as frequency, amplitude, or duration.

Method

Auditory perception in persons with PD was investigated using a tone discrimination task where clients (
N
= 12) and age-matched controls (
N
= 15) made same/different judgments for pairs of pure tones that were factorially varied by acoustic feature (i.e., frequency, amplitude, or duration) crossed with perceptual distance (i.e., close vs. far).

Results

Relative to healthy age-matched controls, persons with PD showed marked impairment in tone discrimination. Persons with PD showed an acoustic feature by perceptual distance interaction that was characterized by deficits in detecting frequency and amplitude differences for perceptually near tones.

Conclusion

These results suggest that persons with PD show a reduced ability to notice change in frequency and amplitude as compared to normal older adults. More generally, these findings implicate a frontal–striatal contribution to auditory perception.
Investigating the Use of Traditional and Spectral Biofeedback Approaches to Intervention for /r/ Misarticulation
Authors: Byun Tara McAllister , Hitchcock Elaine R.
Published: July 2012

Purpose

Misarticulation of /r/ is among the most challenging developmental speech errors to remediate. Case studies suggest that visual biofeedback treatment can establish perceptually accurate /r/ in clients who have not responded to traditional treatments. This investigation studied the response of children with persistent /r/ misarticulation to a course of traditional treatment and a course of biofeedback treatment.

Method

Eleven children with /r/ misarticulation completed 10 weeks of individual treatment consisting of 4–6 weeks of traditional treatment followed by 4–6 weeks of biofeedback treatment. Progress was measured by tracking correct /r/ productions within treatment and probing /r/ in words at 3 time points.

Results

At the group level, there was no difference in independent judges’ ratings of /r/ sounds produced by the children before and after traditional treatment. However, /r/ sounds produced after biofeedback treatment were significantly more likely to be rated by the judges as perceptually correct. Eight of the 11 children made measurable gains in the accuracy of isolated /r/ produced within treatment, with 4 showing significant generalization to untreated /r/ in words.

Conclusion

This descriptive study shows that treatment incorporating spectral biofeedback can facilitate accurate /r/ production in children with treatment-resistant errors. A follow-up period using traditional intervention methods may be necessary to encourage generalization.
Feedback Frequency in Treatment for Childhood Apraxia of Speech
Authors: Maas Edwin , Butalla Christine E. , Farinella Kimberly A.
Published: July 2012

Purpose

To examine the role of feedback frequency in treatment for childhood apraxia of speech (CAS). Reducing the frequency of feedback enhances motor learning, and recently, such feedback frequency reductions have been recommended for the treatment of CAS. However, no published studies have explicitly compared different feedback frequencies in this population.

Method

Using an alternating treatments single-subject design with multiple baselines across behaviors, retention and transfer of learning were compared following high-frequency feedback and low-frequency feedback in 4 children with CAS. Feedback frequency was manipulated in the context of an integral stimulation treatment. Changes in perceptual accuracy were quantified with effect sizes and were compared across conditions.

Results

Findings were mixed, with 2 children showing an advantage for low-frequency feedback, 1 child showing a small advantage for high-frequency feedback, and 1 child showing no clear improvement in either condition.

Conclusion

These findings suggest that reducing the frequency of feedback may be beneficial for some children with CAS, although this may vary with the child’s age or severity of apraxia. Caution is warranted in extrapolating from the nonspeech motor learning literature to speech treatment for CAS. Finally, this study contributes another replication to the literature on the efficacy of integral stimulation treatment for children with CAS.
South pole bang-time diagnostic on the National Ignition Facility (invited)
Authors: Edgell D. H. , Bradley D. K. , Bond E. J. , Burns S. , Callahan D. A , Celeste J. , Eckart M. J. , Glebov V. Yu. , Hey D. S. , Lacaille G. , Kilkenny J. D. , Kimbrough J. , Mackinnon A. J. , Magoon J. , Parker J. , Sangster T. C. , Shoup M. J. , Stoeckl C. , Thomas T. , MacPhee A.
Published: July 2012

The south pole bang-time diagnostic views National Ignition Facility (NIF) implosions through the lower Hohlraum laser entrance hole to measure the time of peak x-ray emission (peak compression) in indirect-drive implosions. Five chemical-vapor-deposition diamond photoconductive detectors with different filtrations and sensitivities record the time-varying x rays emitted by the target. Wavelength selecting highly oriented pyrolytic graphite crystal mirror monochromators increase the x-ray signal-to-background ratio by filtering for 11-keV emission. Diagnostic timing and the in situ temporal instrument response function are determined from laser impulse shots on the NIF. After signal deconvolution and background removal, the bang time is determined to 45-ps accuracy. The x-ray “yield” (mJ/sr/keV at 11 keV) is determined from the time integral of the corrected peak signal.
Extended Poincaré supersymmetry in three dimensions and supersymmetric anyons
Authors: Chaichian M. , Tureanu A. , Zhang R. B.
Published: August 2012

We classify the unitary representations of the extended Poincaré supergroups in three dimensions. Irreducible unitary representations of any spin can appear, which correspond to supersymmetric anyons. Our results also show that all irreducible unitary representations necessarily have physical momenta. This is in sharp contrast to the ordinary Poincaré group that admits in addition irreducible unitary representations with nonphysical momenta, which are discarded on physical grounds.
Study of liquid jet instability by confocal microscopy
Authors: Yang Lisong , Adamson Leanne J. , Bain Colin D.
Published: August 2012

The instability of a liquid microjet was used to measure the dynamic surface tension of liquids at the surface ages of ≤1 ms using confocal microscopy. The reflected light from a laser beam at normal incidence to the jet surface is linear in the displacement of the surface near the confocal position, leading to a radial resolution of 4 nm and a dynamic range of 4 μm in the surface position, thus permitting the measurement of amplitude of oscillation at the very early stage of jet instability. For larger oscillations outside the linear region of the confocal response, the swell and neck position of the jet can be located separately and the amplitude of oscillation determined with an accuracy of 0.2 μm. The growth rate of periodically perturbed water and ethanol/water mixture jets with a 100-μm diameter nozzle and mean velocity of 5.7 m s−1 has been measured. The dynamic surface tension was determined from the growth rate of the instability with a linear, axisymmetric, constant property model. Synchronisation of the confocal imaging system with the perturbation applied to the jet permitted a detailed study of the temporal evolution of the neck into a ligament and eventually into a satellite drop.
A theoretical approach to electric breakdown behaviour and effective secondary emission coefficient in gas discharge process between two parallel-plane disk electrodes
Authors: Noori H. , Ranjbar A. H.
Published: August 2012

The gas discharge characteristics are seriously influenced by the effective secondary electron-emission coefficient (γeff) originally defined by Townsend. A theoretical approach has been proposed for the determination of variation of this coefficient as a function of the geometrical parameter d/R (the ratio of inter-electrode distance to electrode radius) in the most practical range of 0.08≤d/R≤1.90. Two geometrical factors gi and gp, which are attributed to ion-induced and photon-induced terms, respectively, were introduced to the effective gamma in parallel-plane arrangement. The factors were theoretically derived and hence the effective gamma and the breakdown voltage for a specified geometrical parameter, such as d/R=0.16, were obtained. Then, the effective gamma and the Paschen curves for various geometrical parameters such as d/R=0.32, 0.63, 1.27, and 1.90 were theoretically reproduced. The obtained results showed quite a good agreement with those reported by other researchers and verified that the proposed gi and gp have properly been introduced and derived.
Generation of lower hybrid and whistler waves by an ion velocity ring distribution
Authors: Winske D. , Daughton W.
Published: August 2012

Using fully kinetic simulations in two and three spatial dimensions, we consider the generation and nonlinear evolution of lower hybrid waves produced by a cold ion ring velocity distribution in a low beta plasma. We show that the initial development of the instability is very similar in two and three dimensions and not significantly modified by electromagnetic effects, consistent with linear theory. At saturation, the level of electric field fluctuations is a small fraction of the background thermal energy; the electric field and corresponding density fluctuations consist of long, field-aligned striations. Energy extracted from the ring goes primarily into heating the background ions and the electrons at comparable rates. The initial growth and saturation of the magnetic components of the lower hybrid waves are related to the electric field components, consistent with linear theory. As the growing electric field fluctuations saturate, parallel propagating whistler waves develop by the interaction of two lower hybrid waves. At later times, these whistlers are replaced by longer wavelength, parallel propagating whistlers that grow through the decay of the lower hybrid fluctuations. Wave matching conditions demonstrate these conversion processes of lower hybrid waves to whistler waves. The conversion efficiency (=ratio of the whistler wave energy to the energy in the saturated lower hybrid waves) is computed and found to be significant (∼15%) for the parameters of the three-dimensional simulation (and even larger in the two-dimensional simulation), although when normalized in terms of the initial kinetic energy in the ring ions the overall efficiency is very small (<10−4). The results are compared with relevant linear and nonlinear theory.
Resonance zones and quasi-linear diffusion coefficients for radiation belt energetic electron interaction with oblique chorus waves in the Dungey magnetosphere
Authors: Shi Run , Ni Binbin , Gu Xudong , Zhao Zhengyu , Zhou Chen
Published: August 2012

The resonance regions for resonant interactions of radiation belt electrons with obliquely propagating whistler-mode chorus waves are investigated in detail in the Dungey magnetic fields that are parameterized by the intensity of uniform southward interplanetary magnetic field (IMF) Bz or, equivalently, by the values of D=(M/Bz,0)1/3 (where M is the magnetic moment of the dipole and Bz,0 is the uniform southward IMF normal to the dipole’s equatorial plane). Adoption of background magnetic field model can considerably modify the determination of resonance regions. Compared to the results for the case of D = 50 (very close to the dipole field), the latitudinal coverage of resonance regions for 200 keV electrons interacting with chorus waves tends to become narrower for smaller D-values, regardless of equatorial pitch angle, resonance harmonics, and wave normal angle. In contrast, resonance regions for 1 MeV electrons tend to have very similar spatial lengths along the field line for various Dungey magnetic field models but cover different magnetic field intervals, indicative of a strong dependence on electron energy. For any given magnetic field line, the resonance regions where chorus-electron resonant interactions can take place rely closely on equatorial pitch angle, resonance harmonics, and kinetic energy. The resonance regions tend to cover broader latitudinal ranges for smaller equatorial pitch angles, higher resonance harmonics, and lower electron energies, consistent with the results in Ni and Summers [Phys. Plasmas 17, 042902, 042903 (2010)]. Calculations of quasi-linear bounce-averaged diffusion coefficients for radiation belt electrons due to nightside chorus waves indicate that the resultant scattering rates differ from using different Dungey magnetic field models, demonstrating a strong dependence of wave-induced electron scattering effect on the adoption of magnetic field model. Our results suggest that resonant wave-particle interaction processes should be implemented into a sophisticated, accurate global magnetic field model to pursue comprehensive and complete models of radiation belt electron dynamics.
Algebraic-diagrammatic construction polarization propagator approach to indirect nuclear spin–spin coupling constants
Authors: Rusakova I. L. , Krivdin L. B. , Rusakov Yu. Yu. , Trofimov A. B.
Published: July 2012

A new polarization propagator approach to indirect nuclear spin–spin coupling constantans is formulated within the framework of the algebraic-diagrammatic construction (ADC) approximation and implemented at the level of the strict second-order approximation scheme, ADC(2). The ADC approach possesses transparent computational procedure operating with Hermitian matrix quantities defined with respect to physical excitations. It is size-consistent and easily extendable to higher orders via the hierarchy of available ADC approximation schemes. The ADC(2) method is tested in the first applications to HF, N2, CO, H2O, HCN, NH3, CH4, C2H2, PH3, SiH4, CH3F, and C2H4. The calculated indirect nuclear spin–spin coupling constants are in good agreement with the experimental data and results of the second-order polarization propagator approximation method. The computational effort of the ADC(2) scheme scales as n5 with respect to the number of molecular orbitals n, which makes this method promising for applications to larger molecules.
Charge photo-carrier transport from silicon nanocrystals embedded in SiO2-based multilayer structures
Authors: Dridi Rezgui B. , Gourbilleau F. , Maestre D. , Palais O. , Sibai A. , Lemiti M. , Brémond G.
Published: July 2012

Experimental investigation of photoconductivity in Si-rich silicon oxide (SRSO)/SiO2 multilayer (ML) structures prepared by magnetron reactive sputtering is reported. Photocurrent (PC) measurements show that the PC threshold increases with decreasing the thickness of SRSO layer. Photo-conduction processes in our samples are shown to be dominated by carrier transport through quantum-confined silicon nanocrystals embedded in the SiO2 host. In addition, the observed bias-dependence of photocurrent intensity is consistent with a model in which carrier transport occurs by both tunneling and hopping through defect states in the silicon oxide matrix. A photocurrent density Jph of 1–2 mA cm−2 is extracted from our results. Although this photocurrent density along the ML absorber film is relatively low, the results presented in this work are believed to be a valuable contribution toward the implementation of all-Si tandem solar cells.
High-pressure elastic properties of a fluorinated copolymer: Poly(chlorotrifluoroethylene-co-vinylidene fluoride) (Kel-F 800)
Authors: Stevens Lewis L. , Dattelbaum Dana M. , Ahart Muhtar , Hemley Russell J.
Published: July 2012

The acoustic properties and their pressure dependence have been determined to 18.5 GPa for nearly amorphous poly(chlorotrifluoroethylene-co-vinylidene fluoride) (Kel-F 800) using high-pressure Brillouin scattering. At all measured pressures, both longitudinal and transverse acoustic modes were observed allowing for calculation of the pressure-volume isotherm for this predominantly amorphous material. Analysis of the room temperature isotherm using semi-empirical equation of state fitting forms to 5.5 GPa yielded a zero-pressure bulk modulus, Ko, and pressure derivative, Ko′, of 2.8 GPa and 30.6, respectively, which are consistent with the results from dilatometry measurements at very low pressures. Furthermore, the C11 and C12 elastic moduli for the isotropic polymer were determined at each pressure interval and, subsequently, examined to provide the pressure dependence of the bulk, shear, and Young’s moduli. These results are discussed in relation to polymer mechanics at pressures far exceeding those of previous, static compression experiments.
A multi-crystal wavelength dispersive x-ray spectrometer
Authors: Alonso-Mori Roberto , Kern Jan , Sokaras Dimosthenis , Weng Tsu-Chien , Nordlund Dennis , Tran Rosalie , Montanez Paul , Delor James , Yachandra Vittal K. , Yano Junko , Bergmann Uwe
Published: August 2012

A multi-crystal wavelength dispersive hard x-ray spectrometer with high-energy resolution and large solid angle collection is described. The instrument is specifically designed for time-resolved applications of x-ray emission spectroscopy (XES) and x-ray Raman scattering (XRS) at X-ray Free Electron Lasers (XFEL) and synchrotron radiation facilities. It also simplifies resonant inelastic x-ray scattering (RIXS) studies of the whole 2d RIXS plane. The spectrometer is based on the Von Hamos geometry. This dispersive setup enables an XES or XRS spectrum to be measured in a single-shot mode, overcoming the scanning needs of the Rowland circle spectrometers. In conjunction with the XFEL temporal profile and high-flux, it is a powerful tool for studying the dynamics of time-dependent systems. Photo-induced processes and fast catalytic reaction kinetics, ranging from femtoseconds to milliseconds, will be resolvable in a wide array of systems circumventing radiation damage.
Absolute determination of charge-coupled device quantum detection efficiency using Si K-edge x-ray absorption fine structure
Authors: Dunn J. , Steel A. B.
Published: August 2012

We report a method to determine the quantum detection efficiency and the absorbing layers on a front-illuminated charge-coupled device (CCD). The CCD under study, as part of a crystal spectrometer, measures intense continuum x-ray emission from a picosecond laser-produced plasma and spectrally resolves the Si K-edge x-ray absorption fine structure due to the electrode structure of the device. The CCD response across the Si K-edge shows a large discontinuity as well as a number of oscillations that are identified individually and uniquely from Si, SiO2, and Si3N4 layers. From the spectral analysis of the structure and K-edge discontinuity, the active layer thickness and the different absorbing layers thickness can be determined precisely. A precise CCD detection model from 0.2 to 10 keV can be deduced from this highly sensitive technique.
Potassium-intercalated H2Pc films: Alkali-induced electronic and geometrical modifications
Authors: Nilson K. , Åhlund J. , Shariati M.-N. , Schiessling J. , Palmgren P. , Brena B. , Göthelid E. , Hennies F. , Huismans Y. , Evangelista F. , Rudolf P. , Göthelid M. , Mårtensson N. , Puglia C.
Published: July 2012

X-ray spectroscopy studies of potassium intercalated metal-free phthalocyanine multilayers adsorbed on Al(110) have been undertaken. Photoelectron spectroscopy measurements show the presence of several charge states of the molecules upon K intercalation, due to a charge transfer from the alkali. In addition, the comparison of valence band photoemission spectra with the density functional theory calculations of the density of states of the H2Pc− anion indicates a filling of the formerly lowest unoccupied molecular orbital by charge transfer from the alkali. This is further confirmed by x-ray absorption spectroscopy (XAS) studies, which show a decreased density of unoccupied states. XAS measurements in different experimental geometries reveal that the molecules in the pristine film are standing upright on the surface or are only slightly tilted away from the surface normal but upon K intercalation, the molecular orientation is changed in that the tilt angle of the molecules increases.
Multi-channel far-infrared HL-2A interferometer-polarimeter
Authors: Zhou Y. , Deng Z. C. , Li Y. G. , Yi J.
Published: July 2012

An HL-2A interferometer is upgraded to a multi-channel interferometer/polarimeter, which includes four chords for the interferometer and four chords for the polarimeter. The far-infrared lasers (at λ = 432.5 μm and 30 mW power) are used to probe plasmas horizontally in the midplane of HL-2A. A conventional heterodyne technique is used for the interferometer. Two counter-rotating circularly polarized waves are used to measure the Faraday rotation effect. A fast-phase comparator with temporal resolution of 1 μs and phase resolution 0.1° is developed. Further, the distortion of the polarization caused by the beam-splitters and the other optical components is also investigated.
Optimization of smart microgrid considering domestic flexible loads
Authors: Hakimi S. M. , Moghaddas-Tafreshi S. M.
Published: July 2012

The generated power is adjusted on the base of the predicted energy demand for near future, in the existing power systems. In other words, the generated energy follows load profile to meet the energy demand. There is no control over the loads except load shedding which may happen during the fault incidents or peak energy demand. Integration of renewable energy sources into the grid, has introduced further complexity in the above mentioned strategy of following the load curve. Main renewable energies like wind or solar power are not accurately predictable. The uncertain amount of the generated energy necessitate the increase in the generation and storage capacity of the energy by constructing bigger or more number of power plants and energy storage facilities. This will increase cost, pollution, and number of turning off/on of the power plants. Identification and appropriate control of flexible loads can be employed to balance energy generation and demand. In other words contrary to the traditional methods, the proposed method will enable the system to meet the demand not only by changing the generated energy but also by controlling the loads when necessary. Also utilizing flexible loads will significantly reduce energy loss of the storage equipments. Instead of storing energy to be used later, flexible load can consume that energy whenever is needed. In this paper, we consider smart microgrid consist of wind turbines, solar panels, fuel cells, electrolyzers, and smart appliance. In this study, we consider washing machines as flexible loads and we want to manage and control these loads to reduce sizes of generation units, buying and selling energy from distribution grid and total cost of smart microgrid. This study is performed for Ekbatan residential complex Tehran, Iran.
The role of shallow traps in dynamic characterization of organic semiconductor devices
Authors: Knapp Evelyne , Ruhstaller Beat
Published: August 2012

We present an analysis of charge mobility determination methods for the steady as well as the transient state and investigate shallow charge traps with respect to their dynamic behavior. We distinguish between fast and slow trap states in our numerical model corresponding to two characteristic regimes. The two regimes manifest themselves in both impedance spectroscopy and dark injection transient currents (DITC). Further we investigate the charge mobility obtained from dynamic simulations and relate it to the extracted charge mobility from steady-state current-voltage curves. To demonstrate the practical impact of these regimes, we apply our numerical model to the DITC that have commonly been used to determine the charge mobility in organic semiconductor devices. The obtained results from DITC studies strongly depend on the measurement conditions. Therefore we analyze the measurements of reference [Esward et al., J. Appl. Phys. 109, 093707 (2011)] and reproduce the effects of varying pulse off-times on the transient current qualitatively. Thus, our simulations are able to explain the experimental observations with the help of relaxation effects due to shallow traps.
Crystallization of fused silica surfaces by ultra-violet laser irradiation
Authors: Hirata Kazuya , Haraguchi Koshi
Published: August 2012

In recent years, the increased use of high power lasers has created problems in optical elements due to laser damage. The International Organization for Standardization (ISO) describes in a publication ISO 11254 a laser-power resilience (LPR) test which we used to verify that by flattening the glass substrate of an optical element, we could improve the resistance to laser damage. We report on an evaluation of two types of samples of fused silica substrate whose surface roughness differed (Ra = 0.20 nm and Ra = 0.13 nm) using customized on-line laser damage testing. To induce laser damage to samples, we used the fifth harmonic generation from a Nd:YAG pulse laser (wavelength: 213 nm, pulse width: 4 ns, repetition frequency: 20 Hz). Results show that flattening reduced the progression of laser damage in the meta-phase laser damage phase by 1/3 of that without flattening. However, pro-phase laser damage which started at fluence 2.39 J/cm2 was unrelated to surface roughness. To analyze the pro-phase laser damage, we used x-ray diffraction (XRD), Raman spectroscopy, and variable pressure-type scanning electron microscopy (VP-SEM). From XRD data, we observed XRD patterns of cristobalite (111), cristobalite (102), α-quartz (111), and β-quartz (102). Raman spectrum data showed an increase in the three-membered ring vibration (600 cm−1), four-membered ring vibration (490 cm−1), and many-membered ring vibration (450 cm−1, 390 cm−1, and 300 cm−1). We observed patchy crystallized areas on the sample surfaces in the VP-SEM images. Based on these experimental results, we believe that the dominant factors in pro-phase laser damage are their physical properties. Substrate and thin film material must be appropriately selected in producing an optical element with a high level of resilience to laser exposure.
Bulk and surface half-metallicity: Metastable zinc-blende TiSb
Authors: Gao G. Y. , Yao K. L.
Published: July 2012

Motivated by the recent experimental fabrication of half-metallic MnSb and CrSb thin films with metastable zinc-blende structure [Aldous et al. Phys. Rev. B 85, 060403(R) (2012); Deng et al. J. Appl. Phys. 99, 093902 (2006)], we investigate the structural, electronic, and magnetic properties of TiSb in both ground-state NiAs and metastable zinc-blende phases by using the first-principles calculations. It is shown that the ground-state NiAs phase is metallic and nonmagnetic, but the metastable zinc-blende phase exhibits half-metallic ferromagnetism with a magnetic moment of 1.00 μB per formula unit. We also reveal that the half-metallicity in bulk ZB TiSb is lost at the Sb-terminated (001) surface due to the appearance of surface states within the gap of the minority-spin channel, but the Ti-terminated (001) surface retains the bulk half-metallicity, which makes ZB TiSb a promising candidate for the possible epitaxial growth of half-metallic thin films or multilayers on semiconductor substrates for spintronic applications.
Quasi-monoenergetic protons accelerated by laser radiation pressure and shocks in thin gaseous targets
Authors: He Min-Qing , Shao Xi , Liu Chuan-Sheng , Liu Tung-Chang , Su Jao-Jang , Dudnikova Galina , Sagdeev Roald Z. , Sheng Zheng-Ming
Published: August 2012

Recent experiments and simulations have demonstrated effective CO2 laser acceleration of quasi-monoenergetic protons from thick gaseous hydrogen target (of thickness tens of laser wavelengths) via hole boring and shock accelerations. We present here an alternative novel acceleration scheme by combining laser radiation pressure acceleration with shock acceleration of protons in a thin gaseous target of thickness several laser wavelengths. The laser pushes the thin gaseous plasma forward while compressing it with protons trapped in it. We demonstrated the combined acceleration with two-dimensional particle-in-cell simulation and obtained quasi-monoenergetic protons ∼44 MeV in a gas target of thickness twice of the laser wavelength irradiated by circularly polarized CO2 laser with normalized laser amplitude a0=10.
Generation of very fast states by nitridation of the SiO2/SiC interface
Authors: Yoshioka Hironori , Nakamura Takashi , Kimoto Tsunenobu
Published: August 2012

Fast states at SiO2/SiC interfaces annealed in NO at 1150–1350 °C have been investigated. The response frequency of the interface states was measured by the conductance method with a maximum frequency of 100 MHz. The interface state density was evaluated based on the difference between quasi-static and theoretical capacitances (C−ψS method). Very fast states, which are not observed in as-oxidized samples, were generated by NO annealing, while states existing at an as-oxidized interface decreased by approximately 90%. The response frequency of the very fast states was higher than 1 MHz and increased when the energy level approaches the conduction band edge. For example, the response frequency (time) was 100 MHz (5 ns) at EC−ET = 0.4 eV and room temperature. The SiO2/SiC interface annealed in NO at 1250 °C showed the lowest interface state density, and NO annealing at a temperature higher than 1250 °C is not effective because of the increase in the very fast states.
A novel local equilibrium model for shaped tokamak plasmas
Authors: Yu Weihong , Zhou Deng , Xiang Nong
Published: August 2012

A model is proposed for a local up-down symmetric equilibrium in the vicinity of a specified magnetic surface with given elongation and triangularity. Different from the Miller’s model [R. L. Miller et al., Phys. Plasmas 5, 973 (1998)], the derivative of the Shafranov shift in the present model is self-consistently determined. The equilibrium accounts for all the essential features, like the elongation, the triangularity, and the Shafranov shift etc., of a shaped cross section. Hence, it can be used for investigation of radially localized plasma modes, like reversed shear Alfvenic eigenmodes and ballooning mode, etc., and it is also suitable for local equilibrium construction used for flux tube plasma simulations.
Investigations on the Combination of Cationic Ring Opening Polymerization and Single Electron Transfer Living Radical Polymerization to Synthesize 2-Ethyl-2-Oxazoline Block Copolymers
Authors: Young Robert A. , Malins Edward L. , Becer C. Remzi
Published: July 2012

Cationic ring opening polymerization of 2-ethyl-2-oxazoline (EtOx) has been performed using α–bromoisobutyryl bromide (tertiary) and 2-bromopropionyl bromide (secondary) as initiators in acetonitrile. The reaction kinetics have been followed and selected P(EtOx) polymers have been used as macroinitiators for the single electron transfer living radical polymerization (SET-LRP) of methyl acrylate (MA), ethylene glycol methyl ether acrylate and 2-(dimethylamino)ethyl methacrylate. Moreover, the effect of solvent and catalyst concentration have been investigated on the SET-LRP of P(EtOx) initiated MA.