bluuebunny/crossref_metadata_2025 huggingface dataset:
SEMI-NONPARAMETRIC ESTIMATES OF CURRENCY SUBSTITUTION BETWEEN THE CANADIAN DOLLAR AND THE U.S. DOLLAR
Authors: Serletis Apostolos , Feng Guohua
Published: December 2009

In this paper we investigate the issue of whether a floating currency is the right exchange rate regime for Canada or whether Canada should consider a currency union with the United States. In the context of the framework recently proposed by James L. Swofford, we use a semi-nonparametric flexible functional form—the asymptotically ideal model (AIM), introduced by William A. Barnett and A. Jonas—and pay explicit attention to the theoretical regularity conditions of neoclassical microeconomic theory, following the suggestions of William A. Barnett and William A. Barnett and Meenakshi Pasupathy. Our results indicate that U.S. dollar deposits are complements to domestic (Canadian) monetary assets, suggesting that Canada should continue the current exchange rate regime, allowing the exchange rate to float freely with no intervention in the foreign exchange market by the Bank of Canada.
NOMINAL RIGIDITIES, RESIDENTIAL INVESTMENT, AND ADJUSTMENT COSTS
Authors: Carlstrom Charles T. , Fuerst Timothy S.
Published: December 2009

Evidence suggests that durable goods and residential housing are more flexibly priced than nondurables and services. Using a standard sticky price general equilibrium model, Barsky, House, and Kimball [American Economic Review 97(3) (2007), 984–998] demonstrate that if durable goods are flexibly priced and nondurables are sticky, then a monetary contraction leads to an expansion in production in the durable sector. This is wildly at odds with the empirical evidence. This paper demonstrates that if three features are added to the model (sticky nominal wages, housing construction adjustment costs, and habit persistence in consumption), it delivers sectoral implications that are broadly consistent with the data.
GORENSTEIN PROJECTIVE, INJECTIVE AND FLAT MODULES
Authors: LIU ZHONGKUI , YANG XIAOYAN
Published: December 2009

In basic homological algebra, projective, injective and flat modules play an important and fundamental role. In this paper, we discuss some properties of Gorenstein projective, injective and flat modules and study some connections between Gorenstein injective and Gorenstein flat modules. We also investigate some connections between Gorenstein projective, injective and flat modules under change of rings.
INVERSE SPECTRAL PROBLEMS FOR SINGULAR RANK-ONE PERTURBATIONS OF A HILL OPERATOR
Authors: YOSHITOMI KAZUSHI
Published: December 2009

We investigate an inverse spectral problem for the singular rank-one perturbations of a Hill operator. We give a necessary and sufficient condition for a real sequence to be the spectrum of a singular rank-one perturbation of the Hill operator.
GROUP ALGEBRAS WHOSE GROUP OF UNITS IS POWERFUL
Authors: BOVDI VICTOR
Published: December 2009

A p-group is called powerful if every commutator is a product of pth powers when p is odd and a product of fourth powers when p=2. In the group algebra of a group G of p-power order over a finite field of characteristic p, the group of normalized units is always a p-group. We prove that it is never powerful except, of course, when G is abelian.
SAMPLING AND BIRKHOFF REGULAR PROBLEMS
Authors: ANNABY M. H. , BUTERIN S. A. , FREILING G.
Published: December 2009

We establish new sampling representations for linear integral transforms associated with arbitrary general Birkhoff regular boundary value problems. The new approach is developed in connection with the analytical properties of Green’s function, and does not require the root functions to be a basis or complete. Unlike most of the known sampling expansions associated with eigenvalue problems, the results obtained are, generally speaking, of Hermite interpolation type.
RANDERS METRICS OF SCALAR FLAG CURVATURE
Authors: CHENG XINYUE , SHEN ZHONGMIN
Published: December 2009

We study an important class of Finsler metrics, namely, Randers metrics. We classify Randers metrics of scalar flag curvature whose S-curvatures are isotropic. This class of Randers metrics contains all projectively flat Randers metrics with isotropic S-curvature and Randers metrics of constant flag curvature.
Overview of the North American beef cattle industry and the incidence of bovine respiratory disease (BRD)
Authors: Miles Delbert G.
Published: December 2009

The North American beef cattle industry has endured many changes throughout the years but is encountering some of the most dramatic challenges in history during the first decade of the 21st century. The US beef cattle inventory increased from 1990 to a high of 103.5 million in 1996 and since has declined to a low of 94.5 million on 1 January 2009. Even though economic signals have encouraged the cow herd to increase over the last 5 years, a significant decrease occurred during 2008. It is difficult to determine the precise cost of bovine respiratory disease (BRD) to the industry but it is reported to be greater than US$500 million per year. Data from our practice indicate that losses from BRD over the last 18 years have been characterized by 5-year cycles of decreases and increases. Perhaps it is time for the industry to look for ways to reduce death loss by methods that focus on the animal's response to the pathogens instead of continuing to focus on the pathogens.
North American cattle marketing and bovine respiratory disease (BRD)
Authors: Smith Robert A.
Published: December 2009

The risk of bovine respiratory disease (BRD) has a significant effect on the value of cattle in the marketplace. Calves sold in larger groups have $6.37/45.45 kg more value than those sold as singles or in small groups. Morbidity is higher in unweaned commingled calves than those marketed in groups more than 45 days following weaning. Calves with an aggressive disposition have significantly less value than docile calves, due largely to depressed performance and less carcass value. The value of cattle in the marketplace can be improved by offering larger, uniform lots of cattle that have been weaned at least 45 days. Cattle that suffer BRD in the feedlot have from $23.23 to $151.18 less value than those remaining healthy.
Impact of bovine respiratory disease (BRD) from the perspective of the Canadian beef producer
Authors: Jim Kee
Published: December 2009

The costs of bovine respiratory disease (BRD) to the beef producer can be estimated by identifying and summing the direct and indirect costs associated with the disease. The major direct costs are attributable to the cost of the feeder, production costs and carcass disposal. The indirect costs are mainly associated with infrastructure and labour.
Antimicrobials and BRD
Authors: Apley Mike
Published: December 2009

Pharmacodynamics is limited with respect to its ability to provide precise predictions to guide therapy because of complications related to the bound versus unbound state of the agent, tissue versus plasma concentrations, drug degradation over time, variations among microorganisms, and factors associated with the specific environment at the infection site. Antimicrobial susceptibility testing is likewise imprecise when applied to an individual animal; however, it is valuable on an animal population basis.
Future of BRD research: an animal health industry perspective
Authors: Wilkinson Ann
Published: December 2009

Industry has made large investments into bovine respiratory disease (BRD) research historically, and will continue to do so, despite the apparent lack of progress, an uncertain regulatory environment, and increased competition for internal resources. Factors such as the growing demand for protein, and the ongoing consolidation and ‘technification’ of the beef sector globally suggest that the industry will continue to demand interventions that prevent disease, are more efficacious, can be easily administered, and positively affect meat quality. New products must also meet the regulatory requirements of safety and efficacy and anticipate the future needs of the numerous stakeholders in the global food chain. Two obstacles in meeting this challenge are the declining interest in food animal medicine, and BRD specifically, and the reluctance to accept new technology at the consumer level.
BRD research needs in the next 10–20 years
Authors: McVey D. Scott
Published: December 2009

Despite numerous advances in bovine infectious disease research, bovine respiratory disease (BRD) remains a significant disease threat and a cause of tremendous loss. Renewed efforts and innovative strategies are required to build on the successes of the past to achieve the successes of tomorrow. Continued and improved support of BRD research will prove to be a worthwhile investment. To achieve better coordination and more efficient use of resources, the following supportive actions should be considered. There should be coordination of integrative teams through an over-arching agency (United States Department of Agriculture (USDA)) to provide peer review and priority review for available public research funds. This would include use of development grants (as seed and matching funding) available to public/private partnerships. Testing and validation of new procedures in production settings (providing more than cost analyses) should be strengthened. Publication of studies should be promoted and old links between clinicians, diagnosticians and basic researchers should be re-established. Sets of ‘best practices’ should be published. Programs to support both basic and applied research through graduate fellowships, residencies, workshops and start-up funding for young research scientists should be strengthened. Sustained funding to train the next generation of research investigators should be addressed as a critical need.
Detection of multidecadal oceanic variability by ocean data assimilation in the context of a “perfect” coupled model
Authors: Zhang S. , Rosati A. , Harrison M. J.
Published: December 2009

The impact of oceanic observing systems, external radiative forcings due to greenhouse gas and natural aerosol (GHGNA), and oceanic initial conditions on long time variability of oceanic heat content and salinity is assessed by the assimilation of oceanic “observations” in the context of a “perfect” Intergovernmental Panel on Climate Change Fourth Assessment Report model. According to times and locations at which observations are available, the 20th century expendable bathythermograph (XBT) temperature and 21st century Argo temperature and salinity observations are drawn from a model simulation (set as the “truth”) with historical GHGNA radiative forcings. These model observations are assimilated into another coupled model simulation based on temporally varying or fixed year GHGNA values and different oceanic initial conditions. The degree to which the assimilation recovers the truth variability of oceanic heat content and salinity is an assessment of the impact of each factor on the detection of the oceanic “climate.” Results show that both the 20th century XBT and 21st century Argo observations adequately capture the basin‐scale variability of heat content. The Argo salinity observations appear to be necessary to reproduce the North Atlantic thermohaline structure and variability. The addition of historical radiative forcings does not make a significant contribution to the detection skill. The initial conditions spun up by historical GHGNA produce better detection skill than the initial conditions spun up by preindustrial fixed year GHGNA due to reduced assimilation shocks. While the 20th century XBT temperature observations alone capture some basic features of salinity variations of the tropical ocean due to the strong T‐S relationship from tropical air‐sea interactions, the Argo salinity observations are important for global state estimation, particularly in high latitudes where haline effects on ocean density are greater.
Characteristics of quasi‐periodic scintillations observed at low latitude
Authors: Patel Kalpana , Singh Ashutosh K. , Singh A. K. , Singh R. P.
Published: December 2009

Quasi‐periodic scintillations are characterized as primary deep fadeout in field strength, associated with regular ringing patterns before and after it. In this paper, observations of quasi‐periodic scintillations using geostationary satellite (FLEETSAT) transmissions operating at frequency 250 MHz at low‐latitude ground station, Varanasi (geomagnetic latitude 14°55′N, longitude 153°59′E), are reported. The results indicate that the quasi‐periodic scintillations are most likely produced by plasma blobs/bubbles present in the E and F regions of the ionosphere which are helpful in identifying the generation mechanism of the associated irregularities. The various characteristic features of the different types of quasi‐periodic scintillations observed at low latitude are discussed for the first time in detail based on a highly comprehensive analysis of longer data sets using autocorrelation, power spectrum, and scintillation index analysis. The computed horizontal scale size of the quasi‐periodic scintillations producing irregularity varies from 100 to 1300 m which shows that the irregularities are of intermediate‐scale sizes. The spectral index obtained from the slopes of power spectrum varies from −2 to −8. All of these observed results are important for identifying the generation mechanism of ionospheric irregularities associated with quasi‐periodic scintillations. The observed fading patterns, especially the modulation of the diffraction patterns (fading envelopes), can be explained by considering an obstacle called radio lens in the ionosphere elongated in one direction. For the first time, we have successfully simulated the amplitude versus time plots of almost all types of quasi‐periodic scintillation patches and found that our modeled and observed characteristics of quasi‐periodic scintillation patches compare well with each other.
Quaternary deformation along the Wharekauhau fault system, North Island, New Zealand: Implications for an unstable linkage between active strike‐slip and thrust faults
Authors: Schermer Elizabeth R. , Little Timothy A. , Rieser Uwe
Published: December 2009

The southern Wairarapa region of the North Island of New Zealand preserves a variably deformed late Quaternary stratigraphic sequence that provides insight into the temporal variability in the partitioning of contraction onto faults in the upper plate of an obliquely convergent margin. Detailed mapping, stratigraphic data, and new radiocarbon and optically stimulated luminescence ages from Quaternary units reveal the interaction between tectonics and sedimentation from ∼125 ka to <9 ka along the Wharekauhau thrust and related faults (i.e., Wharekauhau fault system) at the southern end of the Wairarapa fault zone, a major oblique‐slip fault in the upper plate of the Hikurangi Margin. The Wharekauhau thrust accommodated a minimum of 280 ± 60 m of horizontal shortening from ∼70 to 20 ka. The inferred shortening rate, 3.5–8.4 mm/yr, may have accounted for 11–30% of margin‐normal plate motion. By ∼20 ka, the thrust was abandoned. Subsequent deformation at shallow levels occurred on a segmented fault system that accommodated <1 mm/yr shortening. Active deformation in the region is partitioned between slip on (1) the more western Wairarapa‐Mukamuka fault system (dominantly dextral slip but also causing local uplift of the coast); (2) a series of discontinuously expressed strike‐slip faults and linking blind oblique‐reverse thrusts near the trace of the inactive Wharekauhau thrust; and (3) a blind thrust fault farther to the east. The spatial and temporal complexity of the Wharekauhau fault system and the importance it has had in accommodating upper plate deformation argue for an unsteady linkage between upper plate faults and between these faults and the plate interface.
Crustal structure in the Pakistan Himalaya from teleseismic receiver functions
Authors: Li Aibing , Mashele Bongani
Published: December 2009

Subsurface structure in the Pakistan Himalaya is poorly known despite its geological importance in understanding the trend and growth of the Himalaya. In this paper, we compute receiver functions from a broadband seismic network in northern Pakistan and construct crustal structure beneath the stations. P to S converted phases at the Moho are clearly observed on stacked receiver functions. We model the conversions from the Moho and shallower interfaces using the trial and error method. Assuming a Vp/Vs ratio of 1.75, the modeled crustal thickness is 52–53 km in the Peshawar Basin, 55–62 km in the Lesser Himalaya, and 65–76 km in the Higher Himalaya. The variation of the Moho depth correlates well with surface topography, indicating an Airy type of isostasy in the Pakistan Himalaya. A large negative phase before the Moho conversion is consistently observed at all three stations to the north of the India‐Asia suture, which is best modeled by a low velocity layer in the lower crust. The slow lower crust is likely caused by partial melt resulted from crust thickening. Volatile in the crust of the Kohistan island arc and the subduction and melting of the Indian upper crust may also contribute to the low velocity layer. Like the weak middle‐lower crust in Tibet, this slow lower crust probably has an important role in the formation and growth of the western Himalaya.
Stratospheric influence on the tropospheric circulation revealed by idealized ensemble forecasts
Authors: Gerber E. P. , Orbe C. , Polvani L. M.
Published: December 2009

The coupling between the stratosphere and troposphere following Stratospheric Sudden Warming (SSW) events is investigated in an idealized atmospheric General Circulation Model, with focus on the influence of stratospheric memory on the troposphere. Ensemble forecasts are performed to confirm the role of the stratosphere in the observed equatorward shift of the tropospheric midlatitude jet following an SSW. It is demonstrated that the tropospheric response to the weakening of the lower stratospheric vortex is robust, but weak in amplitude and thus easily masked by tropospheric variability. The amplitude of the response in the troposphere is crucially sensitive to the depth of the SSW. The persistence of the response in the troposphere is attributed to both the increased predictability of the stratosphere following an SSW, and the dynamical coupling between the tropospheric jet and lower stratosphere. These results suggest value in resolving the stratosphere and assimilating upper atmospheric data in forecast models.
Magnetic remanence of hematite‐bearing murals
Authors: Lanza R. , Zanella E. , Saudino S.
Published: December 2009

We report on a series of experiments designed to test the ability of hematite‐bearing colors to record the direction of the ambient magnetic field. Plasterboards accurately oriented with respect to the Earth's magnetic field were painted with red tempera colors prepared with hematite pigments. Magnetic measurements indicate that the color film retains a remanent magnetization and acquires a well developed magnetic fabric. The remanence direction is close to, yet slightly deviated from the Earth's magnetic field. The deviation is interpreted to result from preferential alignment of the pigment grains parallel to the plasterboard surface and depends on both its orientation with respect to magnetic north and the degree of magnetic anisotropy of the color film, which in turn varies according to the pigment used. Investigation of the magnetic remanence of murals may complement archaeomagnetic information derived from traditional materials such as baked and fired structures.
Phonological Awareness, Vocabulary, and Reading in Deaf Children With Cochlear Implants
Authors: Johnson Carol , Goswami Usha
Published: December 2009

Purpose

To explore the phonological awareness skills of deaf children with cochlear implants (CIs) and relationships with vocabulary and reading development.

Method

Forty-three deaf children with implants who were between 5 and 15 years of age were tested; 21 had been implanted at around 2.5 years of age (Early CI group), and 22 had been implanted at around 5 years of age (Late CI group). Two control groups—a deaf hearing aided group (16 children) and a typically developing group of hearing children (19 children)—were also tested. All children received a battery of phonological processing tasks along with measures of reading, vocabulary, and speechreading. Analyses focus on deaf children within the normal IQ range (
n
= 53).

Results

Age at cochlear implantation had a significant effect on vocabulary and reading outcomes when quotient scores were calculated. Individual differences in age at implant, duration of fit, phonological development, vocabulary development, auditory memory, visual memory, and speech intelligibility were all strongly associated with progress in reading for the deaf implanted children. Patterns differed somewhat depending on whether quotient scores or standard scores were used.

Conclusions

Cochlear implantation is associated with development of the oral language, auditory memory, and phonological awareness skills necessary for developing efficient word recognition skills. There is a benefit of earlier implantation.
Tongue Pressure Modulation During Swallowing: Water Versus Nectar-Thick Liquids
Authors: Steele Catriona M. , Bailey Gemma L. , Molfenter Sonja M.
Published: December 2009

Purpose

Evidence of tongue-palate pressure modulation during swallowing between thin and nectar-thick liquids stimuli has been equivocal. This mirrors a lack of clear evidence in the literature of tongue and hyoid movement modulation between nectar-thick and thin liquid swallows. In the current investigation, the authors sought to confirm whether tongue-palate pressures are modulated between discrete swallows of water and nectar-thick juice.

Method

Tongue-palate pressures were measured at 3 sites (anterior, medial, and posterior palate) using an adhered 3-bulb pressure strip in 20 healthy, young adults during discrete swallows of water and nectar-thick apple juice.

Results

Pressure modulation was not noted with respect to pressure amplitudes (in mm Hg), but was identified both in the pressure patterns observed (the sites and number of bulbs activated) and temporal aspects of pressure duration.

Conclusion

Tongue-palate pressure amplitude modulation does not occur for nectar-thick swallows compared to thin liquid swallows. Modulation does, however, occur with respect to the tongue-palate contact surface area and pressure durations. The authors introduce the concept of pressure slope as a meaningful way to examine tongue-palate pressure application in swallowing.
Autism, AAC, and Proloquo2Go
Authors: Sennott Samuel , Bowker Adam
Published: December 2009

People with ASD often need to access AAC in situations where a tabletop digital device is not practical. Recent advancements have made more powerful, portable, and affordable communication technologies available to these individuals. Proloquo2Go is a new portable augmentative and alternative communication system that runs on an iPhone or iPod touch and can be used to meet the diverse needs of individuals with autism spectrum disorders (ASD) who are ambulatory and have difficulty using speech to meet their full daily communication needs. This article examines Proloquo2Go in light of the best practices in AAC for individuals with ASD such as symbols, visual supports, voice output, and inclusion.
Theory-Driven AAC Practices With Adults Who Use Utterance-Based Systems: The Case of Conversational Rule Violations
Authors: Hoag Linda , Bedrosian Jan , McCoy Kathy
Published: December 2009

The purpose of this paper is to explore the pragmatic issue of when to use pre-constructed utterances by discussing a research project investigating messages that fail to meet either conventional standards of contextual appropriateness or timing. The use of pragmatic theory to systematically examine pre-constructed messages will be discussed, along with the outcomes of using messages that do not seem to follow pragmatic rules. The development of a hierarchy of types of rule violations will be described and the clinical implications of the hierarchy will be explored.
Normal Changes in the Speech of Older Adults: You've still got what it takes; it just takes a little longer!
Authors: Hooper Celia R. , Cralidis Ann
Published: December 2009

The authors reviewed the changes in speech production as a result of aging, including changes in structure and function as well as changes in motor control for speech. The following speech production processes in normal or typical aging were reviewed: breathing for speech, phonation, resonation, articulation, and fluency. Different theories of the role of motor control were reviewed, including more recent conclusions that cognition influences speech motor behavior throughout the lifespan. There are many speech changes in the communication of an older adult, but most are adaptive and do not affect good conversational speech.
The conformational dynamics of λ-DNA in the anti-Brownian electrokinetic trap: Brownian dynamics and Monte Carlo simulation
Authors: Dambal Ajey , Shaqfeh Eric S. G.
Published: December 2009

In this work, we examine the conformational dynamics of long polymer molecules under confinement, as in the recently developed anti-Brownian electrokinetic (ABEL) trap [A. Cohen and W. Moerner, Proc. Natl. Acad. Sci. USA. 103, 4362 (2006)]. We analyze polymer motion using Brownian dynamics simulations (bead-spring and bead-rod models) and via Monte Carlo methods. We first verify Cohen and Moerner’s (2007) single molecule observations regarding the existence of short time correlations [Phys. Rev. Lett. 98, 116001 (2007)] in the motion of a polymer’s center of mass, which arise due to fluctuating hydrodynamic interactions. Thereafter, following Cohen and Moerner, we use principal component analysis to extract the principal modes governing polymer conformation and find that confinement and backbone bending only affect small polymers and should not play a significant role in the dynamics of long polymers such as λ-DNA. We find excellent agreement between our principal component analysis modes and those measured by Cohen and Moerner [Proc. Natl. Acad. Sci. U.S.A. 104, 12622 (2007)]. Finally, to explore the effect of excluded volume, in particular, the effect of the excluded volume parameter (z), we use image-image correlations to examine its relation to polymer dynamics. Image-image correlation measurements performed on λ-DNA in the ABEL trap did not display a simple exponential-type behavior and motivated the use of stretched exponential functions to determine the characteristic timescale (τ) governing conformational dynamics. We show that τ scales with polymer length as N2 and decreases with increasing z. Furthermore, we can collapse a variety of data when τN−2 is plotted with respect to N∕zm (m=0.14 for freespace and 0.366 for walls).
Nonepitaxially grown nanopatterned Co–Pt alloys with out-of-plane magnetic anisotropy
Authors: Makarov D. , Klimenta F. , Fischer S. , Liscio F. , Schulze S. , Hietschold M. , Maret M. , Albrecht M.
Published: December 2009

A study on the structural and magnetic properties of 5-nm-thick Co–Pt alloy films grown on thermally oxidized SiO2/Si(100) substrates as well as on self-assemblies of spherical SiO2 particles with sizes down to 10 nm is presented. An out-of-plane easy axis of magnetization was stabilized at deposition temperatures as low as 250 °C in a broad composition range between 40 and 70 at. % of Pt. Owing to the low deposition temperatures, no chemical long-range order is found. Thus, the strong out-of-plane magnetic anisotropy is expected to be caused by anisotropic short-range order effects. The magnetic behavior of CoPt alloys with an equiatomic composition grown on arrays of SiO2 particles was found to be similar to those on planar substrates. Structural investigations using high-resolution transmission electron microscopy revealed that a continuous CoPt layer has been formed, covering the particle tops and connecting them. The magnetic CoPt caps exhibit an out-of-plane easy axis for all particle sizes; however, no pronounced difference in coercive field with particle size was observed, which is associated with the specific morphology of the film structure.
Characterization of nanoparticles through medium-energy ion scattering
Authors: Sortica M. A. , Grande P. L. , Machado G. , Miotti L.
Published: December 2009

In this work we review the use of the medium-energy ion scattering (MEIS) technique to characterize nanostructures at the surface of a substrate. We discuss here how the determination of shape and size distribution of the nanoparticles is influenced by the energy loss at the backscattering collision, which leads to an asymmetrical energy-loss line shape. We show that the use of a Gaussian line shape may lead to important misinterpretations of a MEIS spectrum for nanoparticles smaller than 5 nm. The results are compared to measurements of gold nanoparticles adsorbed on a multilayered film of weak polyelectrolyte.
Phase separation and diffusion processes in concentrated He3–He4 solid mixtures
Authors: Grigor’ev V. N. , Degtyarev I. A. , Lisunov A. A. , Maidanov V. A. , Rubanskii V. Yu. , Rubets S. P. , Rudavskii E. Ya. , Rybalko A. S. , Tikhii V. A.
Published: December 2009

The kinetics of phase separation in quantum crystals of concentrated He3–He4 mixtures containing 34.0, 61.3, and 89.9% He3 are investigated experimentally by the method of precision barometry. The variation of the pressure P(T) of the system upon stepwise cooling and heating is registered. The P(T) curves observed in the experiment are compared with a theory based on a diffusion description of the kinetics of isotropic phase separation. This yields the first information about the mass diffusion coefficient in the whole concentration range. It is shown that in concentrated mixtures the mass diffusion coefficient is several orders of magnitude lower than in dilute mixtures, owing to the interaction of impurities and the presence of elastic strains in the crystal. At the same time, because of the high concentration of new-phase nuclei and the small diffusion length, the phase transition process takes place over a comparatively short time.
Preparation of Bi2Sr2ZnCu2Ox superconducting ceramics and investigation of their electrophysical properties
Authors: Aliev V. M. , Aliev S. A. , Ragimov S. S. , Sultanov G. J. , Mamedova A. N.
Published: December 2009

The composition of synthesized ceramic samples is investigated by x-ray phase analysis, and it is established that they are high-Tc superconducting Bi2Sr2ZnCu2Ox. It is found that the crystal structure is preserved. To investigate how the superconductivity of Bi–Sr–Ca–Cu–O is influenced by the substitution of calcium by zinc, measurements of the temperature dependence of the resistivity, thermal conductivity, and thermopower (Siebeck coefficient) are carried out. It is found that the substituted compound Bi2Sr2ZnCu2Ox retains its superconducting properties (T0=82K). It is shown that substitution of Ca by Zn leads to an increase of the thermal conductivity. While the thermopower of Bi2Sr2CaCu2Ox shows p-type conductivity in the whole range of temperatures investigated, in Bi2Sr2ZnCu2Ox the type of the conductivity is changed to n-type.
Electric properties of erbium cobaltites
Authors: Chiang Yu. N. , Dzyuba M. O. , Khirnyĭ V. F. , Shevchenko O. G. , Kozlovskiĭ A. A.
Published: December 2009

The temperature and electric, including magnetic-field, characteristics of ceramic samples Er1−xSrxCoO3−δ at temperatures ranging from room to liquid-helium temperatures and in magnetic fields to 4kOe applied perpendicular to the direction of the transport current have been investigated. Current-induced nonlinear features of percolation transport which are characteristics for a metal-insulator transition have been observed for weak currents. Regular behavior such as a decrease of the breakdown field with increasing concentration of divalent Sr and ordering effects with decreasing temperature have been observed for the first time. An anomalous increase of the conductivity and a large magnetoresistance effect in narrow Er and Sr concentration ranges, narrower and shifted more in the direction of the metallic phase than in lanthanum manganites, has been observed. The special behavior of the conductivity and the magnetoresistance, including nonlinear effects, are explained from a unified point of view—magnetostructural phase transitions, induced by a corresponding dopant concentration, temperature, or magnetic field, as well as the presence of a spin-dependent contribution, associated with double-exchange of delocalized electrons between heterovalent cobalt ions, to the mechanism of electron correlation.
Cryomechanically obtained nanocrystalline titanium: microstructure and mechanical properties
Authors: Moskalenko V. A. , Smirnov A. R. , Moskalenko A. V.
Published: December 2009

Using a cryomechanical treatment method (an alternative method of intense plastic deformation), nanocrystalline bulk titanium of technical-grade purity with average grain-size up to 35nm has been obtained for the first time. The method is based on the authors’ previous investigations of the role of twinning in the low-temperature plasticity of titanium. Transmission electron microscopy is used to determine the size of the regions of coherent scattering (grains-crystallites); a semiquantitative estimate is made of their dispersity as a function of their mechanothermal treatment regimes. The influence of the average grain size in the nanometer range on the mechanical properties of titanium is studied.
Estimating diffusivity along a reaction coordinate in the high friction limit: Insights on pulse times in laser-induced nucleation
Authors: Knott Brandon C. , Duff Nathan , Doherty Michael F. , Peters Baron
Published: December 2009

In the high friction limit of Kramers’ theory, the diffusion coefficient for motion along the reaction coordinate is a crucial parameter in determining reaction rates from mean first passage times. The Einstein relation between mean squared displacement, time, and diffusivity is inaccurate at short times because of ballistic motion and inaccurate at long times because trajectories drift away from maxima in the potential of mean force. Starting from the Smoluchowski equation for a downward parabolic barrier, we show how drift induced by the potential of mean force can be included in estimating the diffusivity. A modified relation between mean squared displacement, time, and diffusivity now also includes a dependence on the barrier curvature. The new relation provides the diffusivity at the top of the barrier from a linear regression that is analogous to the procedure commonly used with Einstein's relation. The new approach has particular advantages over previous approaches when evaluations of the reaction coordinate are costly or when the reaction coordinate cannot be differentiated to compute restraining forces or velocities. We use the new method to study the dynamics of barrier crossing in a Potts lattice gas model of nucleation from solution. Our analysis shows that some current hypotheses about laser-induced nucleation mechanisms lead to a nonzero threshold laser pulse duration below which a laser pulse will not affect nucleation. We therefore propose experiments that might be used to test these hypotheses.
Enhancement in the photocatalytic nature of nitrogen-doped PVD-grown titanium dioxide thin films
Authors: Tavares C. J. , Marques S. M. , Viseu T. , Teixeira V. , Carneiro J. O. , Alves E. , Barradas N. P. , Munnik F. , Girardeau T. , Rivière J.-P.
Published: December 2009

Nitrogen-doped titanium dioxide semiconductor photocatalytic thin films have been deposited by unbalanced reactive magnetron physical vapor deposition on glass substrates for self-cleaning applications. In order to increase the photocatalytic efficiency of the titania coatings, it is important to enhance the catalysts absorption of light from the solar spectra. Bearing this fact in mind, a reduction in the titania semiconductor band-gap has been attempted by using nitrogen doping from a coreactive gas mixture of N2:O2 during the titanium sputtering process. Rutherford backscattering spectroscopy was used in order to assess the composition of the titania thin films, whereas heavy-ion elastic recoil detection analysis granted the evaluation of the doping level of nitrogen. X-ray photoelectron spectroscopy provided valuable information about the cation-anion binding within the semiconductor lattice. The as-deposited thin films were mostly amorphous, however, after a thermal annealing in vacuum at 500 °C the crystalline polymorph anatase and rutile phases have been developed, yielding an enhancement in the crystallinity. Spectroscopic ellipsometry experiments enabled the determination the refractive index of the thin films as a function of the wavelength, while from the optical transmittance it was possible to estimate the semiconductor indirect band-gap of these coatings, which has been proven to decrease as the N-doping increases. The photocatalytic performance of the titania films has been characterized by the degradation rate of an organic reactive dye under UV/visible irradiation. It has been found that for a certain critical limit of 1.19 at. % of nitrogen doping in the titania anatase crystalline lattice enhances the photocatalytic behavior of the thin films and it is in accordance with the observed semiconductor band-gap narrowing to 3.18 eV. By doping the titania lattice with nitrogen, the photocatalytic activity is enhanced under both UV and visible light.
Current-induced thermal stresses in a metal cylinder
Authors: Yang Fuqian
Published: December 2009

Electromechanical coupling has been widely used to actuate and control micromechanical structures and to produce bulk nanostructured materials from micron and submicron particles. The understanding of the mechanical deformation of a mechanical structure carrying an electric current requires the analyses of both electric and current-induced thermomechanical fields. In this work, we analyze the Joule-heating-induced thermoelastic stresses in a metal cylinder which carries an alternating current. Both Joule heating and mechanical stresses are solved analytically for weak skin effect when electric current density varies in radial direction. The thermal stresses created by the Joule heating are found to be a nonlinear function of the angular frequency of the alternating current. The inclusion of the skin effect and radial variation in electric current density in the analyses shows significant quantitative difference in the stress distribution from the thermomechanical deformation of a metal cylinder which carries a direct current.
A benchmark theoretical study of the electronic ground state and of the singlet-triplet split of benzene and linear acenes
Authors: Hajgató B. , Szieberth D. , Geerlings P. , De Proft F. , Deleuze M. S.
Published: December 2009

A benchmark theoretical study of the electronic ground state and of the vertical and adiabatic singlet-triplet (ST) excitation energies of benzene (n=1) and n-acenes (C4n+2H2n+4) ranging from naphthalene (n=2) to heptacene (n=7) is presented, on the ground of single- and multireference calculations based on restricted or unrestricted zero-order wave functions. High-level and large scale treatments of electronic correlation in the ground state are found to be necessary for compensating giant but unphysical symmetry-breaking effects in unrestricted single-reference treatments. The composition of multiconfigurational wave functions, the topologies of natural orbitals in symmetry-unrestricted CASSCF calculations, the T1 diagnostics of coupled cluster theory, and further energy-based criteria demonstrate that all investigated systems exhibit a A1g singlet closed-shell electronic ground state. Singlet-triplet (S0-T1) energy gaps can therefore be very accurately determined by applying the principles of a focal point analysis onto the results of a series of single-point and symmetry-restricted calculations employing correlation consistent cc-pVXZ basis sets (X=D, T, Q, 5) and single-reference methods [HF, MP2, MP3, MP4SDQ, CCSD, CCSD(T)] of improving quality. According to our best estimates, which amount to a dual extrapolation of energy differences to the level of coupled cluster theory including single, double, and perturbative estimates of connected triple excitations [CCSD(T)] in the limit of an asymptotically complete basis set (cc-pV∞Z), the S0-T1 vertical excitation energies of benzene (n=1) and n-acenes (n=2–7) amount to 100.79, 76.28, 56.97, 40.69, 31.51, 22.96, and 18.16 kcal/mol, respectively. Values of 87.02, 62.87, 46.22, 32.23, 24.19, 16.79, and 12.56 kcal/mol are correspondingly obtained at the CCSD(T)/cc-pV∞Z level for the S0-T1 adiabatic excitation energies, upon including B3LYP/cc-PVTZ corrections for zero-point vibrational energies. In line with the absence of Peierls distortions, extrapolations of results indicate a vanishingly small S0-T1 energy gap of 0 to ∼4 kcal/mol (∼0.17 eV) in the limit of an infinitely large polyacene.
Quantum efficiencies and thermo-optical properties of Er3+-, Nd3+-, and Pr3+-single doped lead-indium-phosphate glasses
Authors: Santos E. A. F. , Silva W. F. , de Araújo M. T. , Vermelho M. V. D. , Guedes I. , Loong C.-K. , Boatner L. A. , Jacinto C.
Published: December 2009

The experimental determination of thermal and optical properties, such as the fluorescence quantum efficiency (η) and temperature coefficient of the optical path length change (ds/dT) have been a challenging task. In this work, mode-mismatched thermal lens and spectroscopic measurements were performed using Er3+-, Nd3+-, and Pr3+-doped lead-indium-phosphate glasses to obtain the thermal diffusivity and conductivity, ds/dT, the thermal loading (nonradiative quantum efficiency), and η. The experimental difficulties associated with obtaining η for systems with several emitting levels, such as Er3+-doped materials were overcome. A discussion of the implications of the small η values obtained for Er3+- and Pr3+-doped glass is presented.
Towards an accurate description of the electronic properties of the biphenylthiol/gold interface: The role of exact exchange
Authors: Fabiano E. , Piacenza M. , D’Agostino S. , Della Sala F.
Published: December 2009

We investigate the role of the exact exchange in describing the biphenylthiol/gold interface. The study is performed by simulating the electronic properties of mercaptobiphenylthiol and aminobiphenylthiol molecules adsorbed on a Au23 cluster, using local, semilocal and hybrid functionals and an effective exact exchange method, namely, the localized Hartree–Fock (LHF). We find that the local/semilocal functionals strongly underestimate the charge transfer and the bond dipole at the interface due to the self-interaction-error (SIE), which alters the correct level alignment. On the other hand the LHF method is SIE free and predicts a larger charge transfer and bond dipole. We also found that LHF results can be reproduced using hybrid functionals and that conventional local/semilocal correlation functionals are unable to improve over the exchange-only description.
Improvement of energy efficiency via spectrum optimization of excitation sequence for multichannel simultaneously triggered airborne sonar system
Authors: Meng Qing-Hao , Yao Zhen-Jing , Peng Han-Yang
Published: December 2009

Both the energy efficiency and correlation characteristics are important in airborne sonar systems to realize multichannel ultrasonic transducers working together. High energy efficiency can increase echo energy and measurement range, and sharp autocorrelation and flat cross correlation can help eliminate cross-talk among multichannel transducers. This paper addresses energy efficiency optimization under the premise that cross-talk between different sonar transducers can be avoided. The nondominated sorting genetic algorithm-II is applied to optimize both the spectrum and correlation characteristics of the excitation sequence. The central idea of the spectrum optimization is to distribute most of the energy of the excitation sequence within the frequency band of the sonar transducer; thus, less energy is filtered out by the transducers. Real experiments show that a sonar system consisting of eight-channel Polaroid 600 series electrostatic transducers excited with 2 ms optimized pulse-position-modulation sequences can work together without cross-talk and can measure distances up to 650 cm with maximal 1% relative error.
Magnetization reorientation in antiferromagnetically coupled Co films and (Co/Pd) multilayers
Authors: Sbiaa Rachid , Piramanayagam S. N. , Law Randall
Published: December 2009

Magnetization reversal of antiferromagnetically coupled (AFC) Co thin film and (Co/Pd) multilayers has been investigated. For 5 Å thick Co layer, a high exchange coupling field (Hex) of 7.8 kOe at room temperature and 8.5 kOe at 5 K was measured from the shift in the hysteresis loop. This high value of Hex was accompanied by a magnetization reorientation from in-plane to out-of-plane of the thin Co. When Co thickness increases, the magnetization reorientation was not possible. This unusual high Hex can be used to stabilize AFC structures when the patterning to nanoscale size is needed.
Compact silicon double and triple dots realized with only two gates
Authors: Pierre M. , Wacquez R. , Roche B. , Jehl X. , Sanquer M. , Vinet M. , Prati E. , Belli M. , Fanciulli M.
Published: December 2009

We report electronic transport on silicon double and triple dots created with the optimized number of two gates. Using silicon nitride spacers two dots in series are created below two top gates overlapping a silicon nanowire. Coupling between dots is controlled by gate voltages. A third dot is created either by combined action of gate voltages or local doping depending on the spacers length. The main characteristics of the triple dot stability diagram are quantitatively fitted.
New shooting algorithms for transition path sampling: Centering moves and varied-perturbation sizes for improved sampling
Authors: Rowley Christopher N. , Woo Tom K.
Published: December 2009

Transition path sampling has been established as a powerful tool for studying the dynamics of rare events. The trajectory generation moves of this Monte Carlo procedure, shooting moves and shifting modes, were developed primarily for rate constant calculations, although this method has been more extensively used to study the dynamics of reactive processes. We have devised and implemented three alternative trajectory generation moves for use with transition path sampling. The centering-shooting move incorporates a shifting move into a shooting move, which centers the transition period in the middle of the trajectory, eliminating the need for shifting moves and generating an ensemble where the transition event consistently occurs near the middle of the trajectory. We have also developed varied-perturbation size shooting moves, wherein smaller perturbations are made if the shooting point is far from the transition event. The trajectories generated using these moves decorrelate significantly faster than with conventional, constant sized perturbations. This results in an increase in the statistical efficiency by a factor of 2.5–5 when compared to the conventional shooting algorithm. On the other hand, the new algorithm breaks detailed balance and introduces a small bias in the transition time distribution. We have developed a modification of this varied-perturbation size shooting algorithm that preserves detailed balance, albeit at the cost of decreased sampling efficiency. Both varied-perturbation size shooting algorithms are found to have improved sampling efficiency when compared to the original constant perturbation size shooting algorithm.
Independent tuning of quantum dots in a photonic crystal cavity
Authors: Kim Hyochul , Thon Susanna M. , Petroff Pierre M. , Bouwmeester Dirk
Published: December 2009

One of the main obstacles to coupling two quantum dots (QDs) to a single nanocavity mode in a cavity quantum electrodynamics system is the ability to independently tune the QD frequencies. We demonstrate that in a GaAs photonic crystal membrane structure with two embedded QD layers, the QD emission frequencies of one QD layer can be tuned independently of the other by applying a voltage across only one of the QD layers.