bluuebunny/crossref_metadata_2025 huggingface dataset:
Incentives, health promotion and equality
Authors: Voigt Kristin
Published: September 2010

The use of incentives to encourage individuals to adopt ‘healthier’ behaviours is an increasingly popular instrument in health policy. Much of the literature has been critical of ‘negative’ incentives, often due to concerns about equality; ‘positive’ incentives, however, have largely been welcomed as an instrument for the improvement of population health and possibly the reduction of health inequalities. The aim of this paper is to provide a more systematic assessment of the use of incentives from the perspective of equality. The paper begins with an overview of existing and proposed incentive schemes. I then suggest that the distinction between ‘positive’ and ‘negative’ incentives – or ‘carrots’ and ‘sticks’ – is of limited use in distinguishing those incentive schemes that raise concerns of equality from those that do not. The paper assesses incentive schemes with respect to two important considerations of equality: equality of access and equality of outcomes. While our assessment of incentive schemes will, ultimately, depend on various empirical facts, the paper aims to advance the debate by identifying some of the empirical questions we need to ask. The paper concludes by considering a number of trade-offs and caveats relevant to the assessment of incentive schemes.
Interplanetary shock characteristics and associated geosynchronous magnetic field variations estimated from sudden impulses observed on the ground
Authors: Wang C. , Li H. , Richardson J. D. , Kan J. R.
Published: September 2010

Interplanetary (IP) shocks disturb the magnetosphere‐ionosphere system resulting in geosynchronous magnetic field changes and sudden impulses observed by ground‐based magnetometers. We extend the implications of a previous statistical study and show that sudden impulses (SIs) can be used to estimate some parameters at the L1 point and geosynchronous orbit, including the change of the square root of solar wind dynamic pressure across the shock and the associated geosynchronous magnetic field changes near the subsolar region. It should be pointed out that the relationship between magnetospheric field change and SIs amplitude and the solar wind dynamic pressure is not a single valued one, but a statistical relationship is useful in cases when interplanetary data are not available. Empirical formulae deduced from observations can be used to estimate certain IP shock characteristics and geosynchronous magnetic field changes from sudden impulse data observed on the ground, with the prediction efficiency as high as 90% and 86%, respectively. These estimates are useful for studying historic, pre‐space era data or if the L1 and geosynchronous data are not available at some future time.
Morphological constraints to wave‐driven circulation in coastal reef‐lagoon systems: A numerical study
Authors: Lowe Ryan J. , Hart Colin , Pattiaratchi Charitha B.
Published: September 2010

The response of the wave‐driven circulation within coastally bounded reef‐lagoon systems to varying lagoon and channel morphology was investigated using a two‐dimensional coupled wave‐circulation numerical model. Numerical experiments were conducted using a series of coastal reefs that incorporated a wide range of different lagoon depths and channel widths. With the morphology of both the reef (forereef and reef flat) and incident wave forcing held constant, the wave‐driven circulation was found to increase substantially as dimensionless reef morphology parameters characterizing the relative lagoon depth and channel width were each independently increased. Analysis of the wave setup fields revealed that this increased flow was due to an enhancement of the cross‐reef water level gradient, resulting from a sharp reduction in the lagoon setup as the frictional resistance on the lagoon‐channel return flow was diminished. This follows similar trends observed in existing field and laboratory studies of wave‐driven reef flows. Analysis of flushing time scales computed for each reef‐lagoon geometry predicted the existence of optimal dimensionless lagoon depths and channel widths for a reef system, to establish maximal coastal flushing. Overall, the circulation and flushing of coastal reef‐lagoon systems was found to be largely controlled by the particular morphology of the lagoon and channel region rather than solely by the morphology of the forereef and reef flat that has been the primary focus of analytical models developed to predict wave setup and circulation on reefs.
Seasonal variation of the quasi 5 day planetary wave: Causes and consequences for polar mesospheric cloud variability in 2007
Authors: Nielsen K. , Siskind D. E. , Eckermann S. D. , Hoppel K. W. , Coy L. , McCormack J. P. , Benze S. , Randall C. E. , Hervig M. E.
Published: September 2010

We have investigated the 5 day wave in both temperature and water vapor in the stratosphere and mesosphere as seen in the Navy Operational Global Atmospheric Prediction System–Advanced Level Physics High Altitude (NOGAPS‐ALPHA) analysis fields for summer 2007. We have compared these fields and the derived saturation ratios with polar mesospheric cloud (PMC) measurements from the AIM satellite. We find that the 5 day wave is variable in both time and space, with significant amplitudes in the temperature wave in August (up to ∼6 K). By contrast, the 5 day wave–induced water vapor anomalies remain at a near‐constant level throughout the season. During August, the 5 day wave in the NOGAPS‐ALPHA saturation ratio and in the occurrence of clouds in the AIM data shows a clear anticorrelation with bright PMCs forming in the trough of the temperature wave. The analysis shows that the August enhancement in the 5 day wave amplitude acts to extend the PMC season past the time when zonal mean temperatures are saturated with respect to ice. The increased wave amplitude in August is attributed to in situ wave generation and amplification due to baroclinic instability of mean winds at around 0.1–0.01 hPa. The late‐season extension of cloud occurrence due to the 5 day wave may explain previous ground‐based reports of bright noctilucent cloud displays in August.
An evaluation of the Worldwide Lightning Location Network (WWLLN) using the National Lightning Detection Network (NLDN) as ground truth
Authors: Abarca Sergio F. , Corbosiero Kristen L. , Galarneau Thomas J.
Published: September 2010

A performance assessment of the Worldwide Lightning Location Network (WWLLN) is presented using the National Lightning Detection Network (NLDN) as ground truth, over unprecedented time and spatial scales. The study spans 3 years, from 5 April 2006 to 31 March 2009, throughout the contiguous United States. The capabilities of the network are shown to improve greatly from the first to the third year of the study, with an overall detection efficiency of cloud‐to‐ground flashes increasing from 3.88% in 2006−2007 to 10.30% in 2008−2009. The WWLLN cloud‐to‐ground detection efficiency is found to be strongly dependent on peak current and polarity, attaining values larger than 10% (35%) for currents stronger than ±35 kA (−130 kA) and values less than 2% for currents between 0 and −10 kA. The location accuracy is found to have a northward and westward bias, with average location errors of 4.03 km in the north‐south and 4.98 km in the east‐west directions, respectively. The WWLLN is shown to have strong limitations in capturing the diurnal cycle, missing both the timing of the maximum and minimum lightning activity (around 1600 and 0900 LT, respectively), and the amplitude of the cycle as well. It is found that in 3 h intervals, the number of flashes in the WWLLN has some proportionality to the number of flashes in the NLDN, suggesting that the WWLLN has strong potential for meteorological applications.
Ozone and temperature response of a chemistry climate model to the solar cycle and sea surface temperature
Authors: Yamashita Yousuke , Sakamoto Kei , Akiyoshi Hideharu , Takahashi Masaaki , Nagashima Tatsuya , Zhou L. B.
Published: September 2010

The results from a three‐dimensional chemistry climate model (CCM) of the Center for Climate System Research/National Institute for Environmental Studies (CCSR/NIES) were analyzed for 1980–2000 to detect variations due to the 11 year solar cycle. Multiple regression analysis, including the constant, linear trend, solar, quasi‐biennial oscillation, volcanic, and sea surface temperature (SST) terms, was applied for ozone and temperature of the CCM for the REF1 scenario of CCM Validation. Using observed SST as a lower boundary condition, the results suggest that the contribution of solar cycle forcing in the CCSR/NIES CCM is about 1% in ozone volume mixing ratio and 0.2 K in temperature per 100 units of 10.7 cm solar microwave flux in the tropical lower stratosphere for the period 1980–2000. A change in ozone transport may be the main factor for the solar signal of ozone concentration in the lower stratosphere. Another sensitivity experiment excluding solar cycle forcing shows a small solar response in the lower stratosphere, suggesting that the interannual variability of the SST could contribute to the solar term in the lower stratosphere through troposphere‐stratosphere processes and/or have an effect as an artifact of interference due to the insufficient period for analysis.
Updated global map of Martian valley networks and implications for climate and hydrologic processes
Authors: Hynek Brian M. , Beach Michael , Hoke Monica R. T.
Published: September 2010

Martian valley networks have long been viewed as some of the best evidence of prolonged surface water on Mars. Analysis from Viking data showed that valleys were primarily contained on the ancient crust, drainage networks were immature, and large undissected regions occurred in between individual systems. These observations led many to propose that they formed primarily by groundwater processes, and limited or no climate change from the present state was required. Using more recent and higher‐resolution data sets, including visible, infrared, and topographic data, we have manually remapped valleys on a global scale. More than eight times as many valleys have been identified on the surface, and calculated drainage densities are, on average, higher by a factor of 2. Further, regions previously thought to be undissected have significant incision by fluvial processes. Most of these systems seem to have formed around the Noachian‐Hesperian boundary (∼3.8–3.6 Ga). Minor valley formation continued through the Hesperian and into the Early Amazonian epoch, approximately 2.8 Ga ago. The new data reveal characteristics of sustained precipitation and surface runoff including inner braided channels, terraces, multiple periods of formation, complex network morphology, and correlation with other fluviosedimentary features and chloride salts on Mars. Groundwater processes or a transient steam atmosphere generated by impacts played, at most, a minor role. These new results imply that Mars had a long‐lived period or periods of clement conditions toward the end of the Noachian epoch that supported a hydrologic cycle and potentially a biosphere.
Simulating weathering of basalt on Mars and Earth by thermal cycling
Authors: Viles Heather , Ehlmann Bethany , Wilson Colin F. , Cebula Tomasz , Page Mark , Bourke Mary
Published: September 2010

Physical weathering induced by heating and cooling may cause rock breakdown on Mars and Earth. We report results from parallel weathering simulations on basalt blocks exposed to diurnal cycles representing Mars‐like (two simulation runs from −55 to +20 oC and −75 to +10 oC, 1–100% relative humidity, 4–8 mbar pressure, CO2 atmosphere) and hot arid Earth (23–72o C, 30–100% relative humidity) conditions. Under Earth conditions, thermally pre‐stressed blocks showed measurable strength declines, whilst salt pre‐treated blocks showed strength gains. Under Mars‐like conditions, pre‐stressed blocks recorded greater or similar strength declines and salt pre‐treated blocks showed more muted strength declines than under Earth conditions. The results imply that on Earth and Mars diurnal cycling of temperature alone can cause deterioration of basalt with a pre‐existing stress history. The type of stress history is important, with salt pre‐treatment affecting the response of thermally pre‐stressed blocks under both Earth and Mars conditions.
A lightning discharge producing a beam of relativistic electrons into space
Authors: Cohen M. B. , Inan U. S. , Said R. K. , Briggs M. S. , Fishman G. J. , Connaughton V. , Cummer S. A.
Published: September 2010

Strong electric fields associated with lightning generate brief (∼1 ms) but intense Terrestrial Gamma‐ray Flashes (TGFs), detected by spacecrafts. A few events are thought to be the signature of a relativistic electron beam escaping the atmosphere, which is distinguishable from a TGF since the lightning discharge is along the geomagnetic field line from the spacecraft, rather than below. We refer to this event herein as a ‘Terrestrial Energetic‐electron Flash’ (TEF), and present the first TEF with associated discharge. The TEF was detected by the Gamma‐ray Burst Monitor aboard the Fermi satellite, and is correlated with a lightning discharge detected by three Stanford University AWESOME ELF/VLF receivers, a Duke University ULF receiver, and by the GLD360 lightning geolocation network. The discharge, nearly simultaneous with the generated electrons, was of intense peak current and of positive polarity, and with a modest total charge transfer, similar to TGF‐associated discharges.
Asymmetry of solar polar fields and the southward shift of HCS observed by Ulysses
Authors: Virtanen I. I. , Mursula K.
Published: September 2010

We study the hemispheric asymmetry of high‐latitude unipolar fields and the latitudinal shift of the heliospheric current sheet (HCS) using Ulysses magnetic field observations during the perihelion passes in 1994–1995, 2001–2002, and 2007. Using the cumulative flux density and the best fit lines to its high‐latitude observations in the two hemispheres, we find that the absolute value of the high‐latitude radial field of the Southern Hemisphere is larger than in the north during both minimum time scans in 1994–1995 and 2007. The hemispheric difference is about 0.2 nT during both scans, suggesting that the northern field area is some 5%–10% (5%–15%) larger than the southern area and that the HCS is shifted southward by about −2° during both scans. The results resolve the discrepancy between earlier results in 1994–1995 and clarify similar observations in 2007 in the ecliptic. They also verify the southward shift of the HCS during the exceptional solar cycle 23. We also study the detailed structure of the equatorial region and find that generally the Ulysses observations compare favorably with simultaneous heliospheric magnetic field predictions given by Wilcox Solar Observatory synoptic maps. Using a simple HCS model, we find that even in case of southward shifted HCS, the highest peak of the cumulative flux density could be located above the equator. Thus, Ulysses observations around the heliographic equator cannot alone give an unambiguous information of the HCS shift, which emphasizes the importance of studying the high‐latitude sections of Ulysses orbit.
Scaling of mixing parameters in stationary, homogeneous, and stratified turbulence
Authors: Hirabayashi S. , Sato T.
Published: September 2010

The dependency of mixing efficiency on length scales was investigated numerically for stationary, homogeneous, and stratified turbulence. Direct numerical simulations of homogeneous, sheared, and stratified turbulence were carried out under the condition of the energy equilibrium with various combinations of energy dissipation rates, stratifications, and energy‐containing scales. The Reynolds number based on the Taylor microscale was between 28 and 39. It was found from the results of the numerical simulations that mixing parameters have significant dependency on the size of computational domain, which had not been discussed in the previous studies. By scaling the mixing parameters, the flux Richardson number was expressed by a function of the overturn Froude number, which is also expressed as a function of the ratio of the integral scale to the Ozmidov scale. The present model showed relevant agreements with those predicted by experimental results. From the proposed model, it is inferred that the flux Richardson number becomes its maximum of 0.2 when the thickness of the turbulence patch is sufficiently larger than the Ozmidov scale.
Carbon dioxide exchange in a semidesert grassland through drought‐induced vegetation change
Authors: Scott Russell L. , Hamerlynck Erik P. , Jenerette G. Darrel , Moran M. Susan , Barron‐Gafford Greg A.
Published: September 2010

Global warming may intensify the hydrological cycle and lead to increased drought severity and duration, which could alter plant community structure and subsequent ecosystem water and carbon dioxide cycling. We report on the net ecosystem exchange of carbon dioxide (NEE) of a semidesert grassland through a severe drought which drove succession from native bunchgrasses to forbs and to eventual dominance by an exotic bunchgrass. We monitored NEE and energy fluxes using eddy covariance coupled with meteorological and soil moisture variables for 6 years at a grassland site in southeastern Arizona, USA. Seasonal NEE typically showed a springtime carbon uptake after winter‐spring periods of average rainfall followed by much stronger sink activity during the summer rainy season. The two severe drought years (2004 and 2005) resulted in a net release of carbon dioxide (25 g C m−2) and widespread mortality of native perennial bunchgrasses. Above average summer rains in 2006 alleviated drought conditions, resulting in a large flush of broad‐leaved forbs and negative total NEE (−55 g C m−2 year−1). Starting in 2007 and continuing through 2009, the ecosystem became increasingly dominated by the exotic grass, Eragrostis lehmanniana, and was a net carbon sink (−47 to −98 g C m−2 year−1) but with distinct annual patterns in NEE. Rainfall mediated by soils was the key driver to water and carbon fluxes. Seasonal respiration and photosynthesis were strongly dependent on precipitation, but photosynthesis was more sensitive to rainfall variation. Respiration normalized by evapotranspiration showed no interannual variation, while normalized gross ecosystem production (i.e., water use efficiency) was low during drought years and then increased as the rains returned and the E. lehmanniana invasion progressed. Thus, when dry summer conditions returned in 2009, the potential for ecosystem carbon accumulation was increased and the ecosystem remained a net sink unlike similar dry years when native grasses dominated ecosystem structure.
Origin and fate of atmospheric moisture over continents
Authors: van der Ent Rudi J. , Savenije Hubert H. G. , Schaefli Bettina , Steele‐Dunne Susan C.
Published: September 2010

There has been a long debate on the extent to which precipitation relies on terrestrial evaporation (moisture recycling). In the past, most research focused on moisture recycling within a certain region only. This study makes use of new definitions of moisture recycling to study the complete process of continental moisture feedback. Global maps are presented identifying regions that rely heavily on recycled moisture as well as those that are supplying the moisture. An accounting procedure based on ERA‐Interim reanalysis data is used to calculate moisture recycling ratios. It is computed that, on average, 40% of the terrestrial precipitation originates from land evaporation and that 57% of all terrestrial evaporation returns as precipitation over land. Moisture evaporating from the Eurasian continent is responsible for 80% of China's water resources. In South America, the Río de la Plata basin depends on evaporation from the Amazon forest for 70% of its water resources. The main source of rainfall in the Congo basin is moisture evaporated over East Africa, particularly the Great Lakes region. The Congo basin in its turn is a major source of moisture for rainfall in the Sahel. Furthermore, it is demonstrated that due to the local orography, local moisture recycling is a key process near the Andes and the Tibetan Plateau. Overall, this paper demonstrates the important role of global wind patterns, topography and land cover in continental moisture recycling patterns and the distribution of global water resources.
Medium optimization based on the metabolic‐flux spectrum of recombinant Escherichia coli for high expression of human‐like collagen II
Authors: Guo Jiaqing , Luo Yan'e , Fan Daidi , Yang Bo , Gao Pengfei , Ma Xiaoxuan , Zhu Chenhui
Published: September 2010

Recombinant Escherichia coli BL21 was used to produce human‐like collagen II in fed‐batch cultivation. By performing MFA (metabolic‐flux analysis), the carbon/nitrogen molar ratios in both the batch and feeding media were optimized for high‐level production of human‐like collagen II. Three carbon/nitrogen molar ratios in both the batch and feeding media were used in the present study, and the MFA results showed that the optimal carbon/nitrogen molar ratios for the batch and feeding media were 2.36:1 and 5.12:1 respectively, yielding the highest dry‐cell density (67.2 g/l dry cell weight) and human‐like collagen production (10.8 g/l).
Natural occurrence and physiological role of a truncated eIF4E in the porcine endometrium during implantation
Authors: Wollenhaupt Karin , Reinke Kati , Brüssow Klaus-Peter , Albrecht Dirk , Tiemann Ute , Seyfert Hans-Martin , Tomek Wolfgang
Published: September 2010

The present study is the first report providing evidence for a physiological role of a truncated form of the mRNA cap-binding protein eIF4E1 (eukaryotic initiation factor 4E1). Our initial observation was that eIF4E, which mediates the mRNA cap function by recruiting the eIF4F complex (composed of eIF4E, 4G and 4A), occurs in two forms in porcine endometrial tissue in a strictly temporally restricted fashion. The ubiquitous prototypical 25 kDa form of eIF4E was found in ovariectomized and cyclic animals. A new stable 23 kDa variant, however, is predominant during early pregnancy at the time of implantation. Northern blotting, cDNA sequence analysis, in vitro protease assays and MS showed that the 23 kDa form does not belong to a new class of eIF4E proteins. It represents a proteolytically processed variant of eIF4E1, lacking not more than 21 amino acids at the N-terminus. Steroid replacements indicated that progesterone in combination with 17β-oestradiol induced the formation of the 23 kDa eIF4E. Modified cell-free translation systems mimicking the situation in the endometrium revealed that, besides eIF4E, eIF4G was also truncated, but not eIF4A or PABP [poly(A)-binding protein]. The 23 kDa form of eIF4E reduced the repressive function of 4E-BP1 (eIF4E-binding protein 1) and the truncated eIF4G lacked the PABP-binding site. Thus we suggest that the truncated eIF4E provides an alternative regulation mechanism by an altered dynamic of eIF4E/4E-BP1 binding under conditions where 4E-BP1 is hypophosphorylated. Together with the impaired eIF4G–PABP interaction, the modified translational initiation might particularly regulate protein synthesis during conceptus attachment at the time of implantation.
For Children With Hearing Loss: The Times They Are A-changin’
Authors: Houston K. Todd , Caraway Teresa
Published: September 2010

Today, children with hearing loss have more opportunities than ever before to use audition and to achieve age-appropriate spoken language and academic outcomes. Several factors are driving these new outcomes, including universal newborn hearing screening and earlier diagnosis of hearing loss, immediate fitting of advanced hearing technology, and enrollment in appropriate early intervention services. For speech-language pathologists and audiologists, these changes mean altering how these children and their families are served, including the types of diagnostic evaluations that are conducted. Specifically, if speech-language pathologists are to remain vital service providers, they must raise their professional expectations for what these children can ultimately achieve.
Yb
2
+
-doped SrCl2: Electronic structure of impurity states and impurity-trapped excitons
Authors: Sánchez-Sanz Goar , Seijo Luis , Barandiarán Zoila
Published: September 2010

First-principles electronic structure calculations of the excited states of Yb2+-doped SrCl2 crystals up to 65000cm−1 reveal the existence of unexpected excited states with double-well potential energy surfaces and dual electronic structure lying above and very close in energy to the 4f135d manifold, with which they interact strongly through spin-orbit coupling. The double-well energy curves result from avoided crossings between Yb-trapped exciton states (more stable at short Yb–Cl distances) and 4f136s impurity states (more stable at long Yb–Cl distances); the former are found to be preionization states in which the impurity holds the excited electron in close lying empty interstitials located outside the YbCl8 moiety. Spin-orbit coupling between the double-well states and the lower lying 4f135d impurity states spreads the dual electronic structure character to lower energies and, hence, the instability of the divalent oxidation state is also spread. To some extent, the dual electronic structure (impurity-trapped exciton–impurity state) of some excited states expresses and gives support to hypotheses of interaction between Yb2+ and Yb3+ pairs proposed to understand the complex spectroscopy of the material and conciliates these hypotheses with interpretations in terms of the existence of only one type of Yb2+ defect. The results presented confirm the presence of impurity states of the 4f136s configuration among the 4f135d manifolds, as proposed in literature, but their energies are very different from those assumed. The Yb-trapped excitons found in this chloride host can be seen as precursors of the luminescent Yb-trapped excitons characterized experimentally in the isomorphous SrF2 crystals.
Equivariant differential embeddings
Authors: Cross Daniel J. , Gilmore R.
Published: September 2010

Takens [Dynamical Systems and Turbulence, Lecture Notes in Mathematics, edited by D. A. Rand and L. S. Young (Springer-Verlag, New York, 1981), Vol. 898, pp. 366–381] has shown that a dynamical system may be reconstructed from scalar data taken along some trajectory of the system. A reconstruction is considered successful if it produces a system diffeomorphic to the original. However, if the original dynamical system is symmetric, it is natural to search for reconstructions that preserve this symmetry. These generally do not exist. We demonstrate that a differential reconstruction of any nonlinear dynamical system preserves at most a twofold symmetry.
Direct numerical simulation of breakdown to turbulence in a Mach 6 boundary layer over a porous surface
Authors: De Tullio Nicola , Sandham Neil D.
Published: September 2010

Transition to turbulence of a Mach 6 flat plate boundary layer over a porous surface is investigated by direct numerical simulation considering two Reynolds numbers based on the laminar boundary layer displacement thickness, namely, Reδ∗=6000 and Reδ∗=20 000. The transition was initiated by perturbing the laminar boundary layer with small random disturbances and was followed all the way to the turbulent state. The porous geometry was modeled by directly resolving the flow within the pores and the damping of the primary Mack mode of instability was verified. The presence of a porous surface was found to reduce the secondary instability growth rate by reducing the amplitude of the second mode saturation. In particular, the pores suppress the growth of the secondary wave in the near wall region, so that the secondary instability mainly happens near the critical layer. Besides the secondary instabilities Fourier analysis shows additional modes growing at the same rate as the primary instability, consistent with a model for sound waves scattering from the porous surface. The transient growth of u′, ρ′, and T′ fluctuations, in the form of streamwise streaks, appears to favor the fundamental type of secondary instability. Additional calculations revealed that an oblique first mode wave is the most amplified mode in this porous surface configuration. This wave is slightly destabilized by the pores. With the oblique first mode excited, the flow becomes turbulent due to the nonlinear interactions without the need for secondary instabilities.
Enhanced piezoelectric properties of lead zirconate titanate sol-gel derived ceramics using single crystal PbZr0.52Ti0.48O3 cubes
Authors: Lin Yirong , Andrews Clark , Sodano Henry A.
Published: September 2010

Piezoceramic materials have attracted much attention for sensing, actuation, structural health monitoring, and energy harvesting applications in the past two decades due to their excellent coupling between energy in the mechanical and electrical domains. Among all piezoceramic materials, lead zirconate titanate (PZT) has been the most broadly studied and implemented, in industrial applications due to its high piezoelectric coupling coefficients. Piezoceramic materials are most often employed as thin films or monolithic wafers. While there are numerous methods for the synthesis of PZT films, the sol-gel processing technique is the most widely used due to its low densification temperature, the ease at which the film can be applied without costly physical deposition equipment and the capability to fabricate both thin and thick films. However, the piezoelectric properties of PZT sol-gel derived films are substantially lower than those of bulk materials, which limit the application of sol-gel films. In comparison, single crystal PZT materials have higher piezoelectric coupling coefficients than polycrystalline materials due to their uniform dipole alignment. This paper will introduce a novel technique to enhance the piezoelectric properties of PZT sol-gel derived ceramics through the use of single crystal PbZr0.52Ti0.48O3 microcubes as an inclusion in the PZT sol-gel. The PZT single crystal cubes are synthesized through a hydrothermal based method and their geometry and crystal structure is characterized through scanning electron microscopy (SEM) and x-ray diffraction (XRD). A mixture of PZT cubes and sol-gel will then be sintered to crystallize the sol-gel and obtain full density of the ceramic. XRD and SEM analysis of the cross section of the final ceramics will be performed and compared to show the crystal structure and microstructure of the samples. The P-E properties of the samples will be tested using a Sawyer–Tower circuit. Finally, a laser interferometer will be used to directly measure the piezoelectric strain-coupling coefficient of the PZT sol-gel ceramics with and without PZT cube inclusions. The results will show that with the integration of PZT crystal inclusions the d33 coupling coefficient will increase more than 200% compared to that of pure PbZr0.52Ti0.48O3 sol-gel.
Red-emitting fluorescent organic light emitting diodes with low sensitivity to self-quenching
Authors: Forget S. , Chenais S. , Tondelier D. , Geffroy B. , Gozhyk I. , Lebental M. , Ishow E.
Published: September 2010

Concentration quenching is a major impediment to efficient organic light-emitting devices (OLEDs). We herein report on OLEDs based on a fluorescent amorphous red-emitting starbust triarylamine molecule [4-di(4′-tert-butylbiphenyl-4-yl)amino-4′-dicyanovinylbenzene, named FVIN], exhibiting a very small sensitivity to concentration quenching. OLEDs are fabricated with various doping levels of FVIN into Alq3, and show a remarkably stable external quantum efficiency of 1.5% for doping rates ranging from 5% up to 40%, which strongly relaxes the technological constraints on the doping accuracy. An efficiency of 1% is obtained for a pure undoped active region, along with deep red emission (x=0.6; y=0.35 in the Commission Internationale de l'Energie (CIE) coordinates). A comparison of FVIN with the archetypal 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dye is presented in an identical multilayer OLED structure.
Supersymmetric reciprocal transformation and its applications
Authors: Liu Q. P. , Popowicz Ziemowit , Tian Kai
Published: September 2010

The supersymmetric analog of the reciprocal transformation is introduced. This is used to establish a transformation between one of the supersymmetric Harry Dym equations and the supersymmetric modified Korteweg–de Vries equation. The reciprocal transformation, as a Bäcklund-type transformation between these two equations, is adopted to construct a recursion operator for the supersymmetric Harry Dym equation. By proper factorization of the recursion operator, a bi-Hamiltonian structure is found for the supersymmetric Harry Dym equation. Furthermore, a supersymmetric Kawamoto equation is proposed and is associated with the supersymmetric Sawada–Kotera equation. The recursion operator and odd bi-Hamiltonian structure of the supersymmetric Kawamoto equation are also constructed.
Polar fluctuations in Mn substituted KTaO3 ceramics
Authors: Axelsson Anna-Karin , Pan Yuya , Valant Matjaz , Vilarinho Paula M. , Alford Neil McN.
Published: September 2010

Polar fluctuations were found in KTaO3 when K+ was substituted with Mn2+ on the A-site. The temperature dependence of the real part of the dielectric permittivity of (K1−2xMnx◻x)TaO3 ceramics (x=0–0.05) shows a diffuse maximum between 50–100 K in the frequency range 102–106 Hz, shifting to higher temperature with increasing frequency and Mn content. The results are analyzed using a modified Curie–Weiss law, the Cole–Cole equation and the Arrhenius law. Here it is suggested that the observed relaxor-type dielectric behavior is attributed to the formation of electric dipoles originating from two distinct sources; one from an atomic off-center position when Mn2+ substitutes for K+ and one from the anion deficiencies formed by these aliovalent substitutions.
Nucleation of highly dense nanoscale precipitates based on warm laser shock peening
Authors: Liao Yiliang , Ye Chang , Kim Bong-Joong , Suslov Sergey , Stach Eric A. , Cheng Gary J.
Published: September 2010

Warm laser shock peening (WLSP) is an innovative thermomechanical processing technique, which combines the advantages of laser shock peening (LSP) and dynamic aging (DA). It has been found that a unique microstructure with highly dense nanoscale precipitates surrounded by dense dislocation structures is generated by WLSP. In order to understand the nucleation mechanism of the highly dense precipitates during WLSP, aluminum alloy 6061 (AA6061) has been used by investigating the WLSP process with experiments and analytical modeling. An analytical model has been proposed to estimate the nucleation rate in metallic materials after WLSP. The effects of the processing temperature and high strain rate deformation on the activation energy of nucleation have been considered in this model. This model is based on the assumption that DA during WLSP can be assisted by the dense dislocation structures and warm temperature. The effects of the working temperature and dislocation density on the activation energy of precipitation have been investigated. This model is validated by a series of experiments and characterizations after WLSP. The relationships between the processing conditions, the nucleation density of precipitates and the defect density have been investigated.
Refractive index dispersion, optical transmittance, and Raman scattering of BaTi2O5 glass
Authors: Masuno A. , Inoue H. , Yu J. , Arai Y.
Published: September 2010

The optical and vibrational properties of BaTi2O5 glass prepared by containerless processing were investigated. The refractive index was 2.15 and the Abbe number was 21.5, as measured by the focal method. The glass was transparent from 340 nm to 7.7 μm. From the Raman scattering spectrum, the maximum phonon energy was found to be 829 cm−1. Using these data, fundamental optical parameters such as the optical basicity, the average oscillator strength, and the optical band gap were estimated. These parameters suggest that BaTi2O5 glass is an attractive material with many potential applications such as lenses, windows, nonlinear optics, and phosphors; moreover, these parameters can guide future development of new titanate glass compositions with superior optical properties.
Torque detected broad band electron spin resonance
Authors: El Hallak Fadi , van Slageren Joris , Dressel Martin
Published: September 2010

We present a novel technique to measure high frequency electron spin resonance spectra in a broad frequency range (30–1440 GHz) with high sensitivity. We use a quasioptical setup with tunable frequency sources to induce magnetic resonance transitions. These transitions are detected by measuring the change in the magnetic torque signal by means of cantilever torque magnetometry. The setup allows tuning of the frequency, magnetic field, polarization, and the angle between the sample and the external magnetic field. We demonstrate the capabilities of this technique by showing preliminary results obtained on a single crystal of an Fe4 molecular nanomagnet.
Iron-resonant valence band photoemission and oxygen near edge x-ray absorption fine structure study on La1−xSrxFe0.75Ni0.25O3−δ
Authors: Erat Selma , Wadati Hiroki , Aksoy Funda , Liu Zhi , Graule Thomas , Gauckler Ludwig J. , Braun Artur
Published: September 2010

Iron resonant valence band photoemission spectra (VB PES) of Sr substituted LaFe0.75Ni0.25O3−δ have been recorded across the Fe 2p-3d absorption threshold to obtain Fe specific spectral information on the 3d projected partial density of states. Comparison with La1−xSrxFeO3 resonant VB PES literature data suggests that substitution of Fe by Ni forms electron holes which have mainly O 2p character. Substitution of La by Sr increases the hole concentration to an extent that the eg structure vanishes. The variation in the eg and t2g structures is paralleled by the changes in the electrical conductivity.
On the relation between rigging inner product and master constraint direct integral decomposition
Authors: Han Muxin , Thiemann Thomas
Published: September 2010

Canonical quantization of constrained systems with first-class constraints via Dirac’s operator constraint method proceeds by the theory of Rigged Hilbert spaces, sometimes also called refined algebraic quantization. This method can work when the constraints form a Lie algebra. When the constraints only close with nontrivial structure functions, the Rigging map can no longer be defined. To overcome this obstacle, the master constraint method has been proposed which replaces the individual constraints by a weighted sum of absolute squares of the constraints. Now the direct integral decomposition (DID) methods, which are closely related to Rigged Hilbert spaces, become available and have been successfully tested in various situations. It is relatively straightforward to relate the rigging inner product to the path integral that one obtains via reduced phase space methods. However, for the master constraint, this is not at all obvious. In this paper we find sufficient conditions under which such a relation can be established. Key to our analysis is the possibility to pass to equivalent, Abelian constraints, at least locally in phase space. Then the master constraint DID for those Abelian constraints can be directly related to the rigging map and therefore has a path integral formulation.
Can a multivalent defect be mimicked by several Shockley–Read–Hall-like defects?
Authors: Decock Koen , Khelifi Samira , Burgelman Marc
Published: September 2010

The origin of defects present in a device is not always clear. Hence, in electronic device simulation, the influence of defects with more than two different charge states (multivalent defects) is often modeled as a set of defects with only two possible charge states [Shockley–Read–Hall (SRH)-like defects] which follow the SRH statistics. This paper investigates under which circumstances this procedure is allowed, and provides means to check the equivalence between the multivalent and SRH-like description in a fast and efficient way. The procedures are verified simulating a thin film solar cell structure.
Four Lie algebras associated with R6 and their applications
Authors: Zhang Yufeng , Tam Honwah
Published: September 2010

The first part in the paper reads that a three-dimensional Lie algebra is first introduced, whose corresponding loop algebra is constructed, for which isospectral problems are established. By employing zero curvature equations, a modified Kaup–Newell (mKN) soliton hierarchy of evolution equations is obtained. The corresponding hereditary operator and Hamiltonian structure are worked out, respectively. Then two types of enlarging semisimple Lie algebras isomorphic to the linear space R6 are followed to construct, one of them is a complex Lie algebra. Their corresponding loop algebras are also given so that two types of new isospectral problems are introduced to generate two kinds of integrable couplings of the above mKN hierarchy. The hereditary operators, Hamiltonian structures of the hierarchies are produced again, respectively. The exact computing formulas of the constant γ appearing in the trace identity and the variational identity are derived under the semisimple algebras. The second part of this paper is devoted to constructing two kinds of Lie algebras by using product of complex vectors, which are also isomorphic to the linear space R6. Then we make use of the corresponding loop algebras to produce two integrable hierarchies along with bi-Hamiltonian structures. From various aspects, we give some ways for constructing Lie algebras which have extensive applications in generating integrable Hamiltonian systems.
Harmonic coordinates in the string and membrane equations
Authors: He Chun-Lei , Huang Shou-Jun
Published: September 2010

In this note, we first show that the solutions to Cauchy problems for two versions of relativistic string and membrane equations are diffeomorphic. Then we investigate the coordinates transformation presented in D. X. Kong and Q. Zhang [Physica D 238, 902 (2009)] [see (2.20)] which plays an important role in the study on the dynamics of the motion of string in Minkowski space. This kind of transformed coordinates is harmonic coordinates, and the nonlinear relativistic string equations can be straightforwardly simplified into linear wave equations under this transformation.
Potential of bio-DME as a transportation fuel for India
Authors: Himabindu M. , Ravikrishna R. V.
Published: September 2010

This article discusses the potential of bio-dimethyl ether (DME) as a promising fuel for India in the transportation sector where a majority of imported petroleum in the form of diesel is used. Specifically, the suitability of DME in terms of its properties vis-à-vis those of diesel, ability to liquefy DME at low pressures similar to liquefied petroleum gas (LPG), and ease of production from renewable feedstock (biomass), and most importantly, very low emissions including near-zero soot levels are some of the features that make it an attractive option. A detailed review presents the state-of-the-art on various aspects such as estimates of potential bio-DME production, methods of synthesis of bio-DME, important physicochemical properties, fuel-injection system-related concerns (both conventional and common-rail system), fuel spray characteristics which have a direct bearing on the engine performance, and finally, exhaust emissions. Future research directions covering all aspects from production to utilization are summarized
Temperature dependence of electronic transitions and optical properties in multiferroic BiFeO3 nanocrystalline film determined from transmittance spectra
Authors: Li W. W. , Zhu J. J. , Wu J. D. , Gan J. , Hu Z. G. , Zhu M. , Chu J. H.
Published: September 2010

The ultraviolet-infrared transmittance spectra of BiFeO3 nanocrystalline film have been studied in the temperature range 5.3–300 K. A redshift trend of the absorption edge and optical constants with increasing the temperature can be observed. Four interband electronic transitions can be uniquely assigned and strongly depend on the temperature. Moreover, two magnetic transitions located at about 150 and 200 K have been observed and can be interpreted as spin-reorientation transitions. It was found that the optical band gap decreases from 2.69±0.01 to 2.65±0.01 eV with increasing the temperature due to the modification of the electron-phonon interactions.
The effect of underlayer thin films on the surface-enhanced Raman scattering response of Ag nanorod substrates
Authors: Zhou Qin , Liu Yongjun , He Yuping , Zhang Zhengjun , Zhao Yiping
Published: September 2010

The effect of underlayer thin films on the sensitivity of Ag nanorod surface-enhanced Raman scattering (SERS) substrates was studied both theoretically and experimentally. With the same Ag nanorod film, different materials (Ag, Al, Si, and Ti) with different thicknesses (25, 100, and 400 nm) were used as underlayers to alter the reflectivity systematically. The SERS intensity was found to increase linearly with the underlayer reflectivity, which can be explained by a modified Greenler’s model due to the contribution of reflected electric field from the substrate. This finding can be used to design high enhancement SERS substrates.
Topological quantum order: Stability under local perturbations
Authors: Bravyi Sergey , Hastings Matthew B. , Michalakis Spyridon
Published: September 2010

We study zero-temperature stability of topological phases of matter under weak time-independent perturbations. Our results apply to quantum spin Hamiltonians that can be written as a sum of geometrically local commuting projectors on a D-dimensional lattice with certain topological order conditions. Given such a Hamiltonian H0, we prove that there exists a constant threshold ϵ>0 such that for any perturbation V representable as a sum of short-range bounded-norm interactions, the perturbed Hamiltonian H=H0+ϵV has well-defined spectral bands originating from low-lying eigenvalues of H0. These bands are separated from the rest of the spectra and from each other by a constant gap. The band originating from the smallest eigenvalue of H0 has exponentially small width (as a function of the lattice size). Our proof exploits a discrete version of Hamiltonian flow equations, the theory of relatively bounded operators, and the Lieb–Robinson bound.
Magnetic properties of Bi2FeMnO6: A multiferroic material with double-perovskite structure
Authors: Du Y. , Cheng Z. X. , Dou S. X. , Wang X. L. , Zhao H. Y. , Kimura H.
Published: September 2010

Single phase Bi2FeMnO6 was synthesized on Si substrates by an electrospray method. Three peaks were observed in the temperature dependence of magnetization curve, which is attributed to the inhomogeneous distribution of Fe3+ and Mn3+. The observed magnetic peaks at 150 K, 260 K, and 440 K correspond to orderings of the ferrimagnetic Fe–O–Mn, and antiferromagnetic Mn–O–Mn and Fe–O–Fe, respectively. Heat capacity measurements were carried out to confirm these magnetic transitions. The Debye temperature of Bi2FeMnO6 is 339 K, calculated from Debye–Einstein fitting.
The shock-front structure of nanocrystalline aluminum
Authors: Ma Wen , Zhu Wenjun , Jing Fuqian
Published: September 2010

The shock-front structures of nanocrystalline Al are investigated in detail by exploring the relationship between the evolution of stress, particle velocity distributions, and the atomistic structures through molecular dynamics simulations. It is found that in nanocrystalline Al the contribution of grain boundary-mediated plasticity to the shock-front width is significant in comparison with dislocation-mediated plasticity. Due to different deformation mechanisms and time sequences, the shock front can be separated into following three stages: elastic, grain boundary dominated plasticity, and dislocation emission and propagation.