bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrate competition in a coral symbiosis varies with temperature among Symbiodinium clades
Authors: Baker David M , Andras Jason P , Jordán-Garza Adán Guillermo , Fogel Marilyn L
Published: February 2013

Many reef-building corals form symbioses with dinoflagellates from the diverse genus Symbiodinium. There is increasing evidence of functional significance to Symbiodinium diversity, which affects the coral holobiont’s response to changing environmental conditions. For example, corals hosting Symbiodinium from the clade D taxon exhibit greater resistance to heat-induced coral bleaching than conspecifics hosting the more common clade C. Yet, the relatively low prevalence of clade D suggests that this trait is not advantageous in non-stressful environments. Thus, clade D may only be able to out-compete other Symbiodinium types within the host habitat when conditions are chronically stressful. Previous studies have observed enhanced photosynthesis and fitness by clade C holobionts at non-stressful temperatures, relative to clade D. Yet, carbon-centered metrics cannot account for enhanced growth rates and patterns of symbiont succession to other genetic types when nitrogen often limits reef productivity. To investigate the metabolic costs of hosting thermally tolerant symbionts, we examined the assimilation and translocation of inorganic 15N and 13C in the coral Acropora tenuis experimentally infected with either clade C (sub-type C1) or D Symbiodinium at 28 and 30 °C. We show that at 28 °C, C1 holobionts acquired 22% more 15N than clade D. However, at 30 °C, C1 symbionts acquired equivalent nitrogen and 16% less carbon than D. We hypothesize that C1 competitively excludes clade D in hospite via enhanced nitrogen acquisition and thus dominates coral populations despite warming oceans.
The contribution of N2O3 to the cytotoxicity of the nitric oxide donor DETA/NO: an emerging role for S-nitrosylation
Authors: Ali Ahlam A. , Coulter Jonathan A. , Ogle Claire H. , Migaud Marie M. , Hirst David G. , Robson Tracy , McCarthy Helen O.
Published: February 2013

The relationship between the biological activity of NO and its chemistry is complex. The objectives of this study were to investigate the influence of oxygen tension on the cytotoxicity of the NO• donor DETA/NO and to determine the effects of oxygen tension on the key RNS (reactive nitrogen species) responsible for any subsequent toxicity. The findings presented in this study indicate that the DETA/NO-mediated cytotoxic effects were enhanced under hypoxic conditions. Further investigations revealed that neither ONOO− (peroxynitrite) nor nitroxyl was generated. Fluorimetric analysis in the presence of scavengers suggest for the first time that another RNS, dinitrogen trioxide may be responsible for the cytotoxicity with DETA/NO. Results showed destabilization of HIF (hypoxia inducible factor)-1α and depletion of GSH levels following the treatment with DETA/NO under hypoxia, which renders cells more susceptible to DETA/NO cytotoxicity, and could account for another mechanism of DETA/NO cytotoxicity under hypoxia. In addition, there was significant accumulation of nuclear p53, which showed that p53 itself might be a target for S-nitrosylation following the treatment with DETA/NO. Both the intrinsic apoptotic pathway and the Fas extrinsic apoptotic pathway were also activated. Finally, GAPDH (glyceraldehyde-3-phosphate dehydrogenase) is another important S-nitrosylated protein that may possibly play a key role in DETA/NO-mediated apoptosis and cytotoxicity. Therefore this study elucidates further mechanisms of DETA/NO mediated cytotoxicity with respect to S-nitrosylation that is emerging as a key player in the signalling and detection of DETA/NO-modified proteins in the tumour microenvironment.
Haem oxygenase-1 induction reverses the actions of interleukin-1β on hypoxia-inducible transcription factors and human chondrocyte metabolism in hypoxia
Authors: Clérigues Victoria , Murphy Christopher L. , Guillén Maria Isabel , Alcaraz Maria José
Published: February 2013

HO-1 (haem oxygenase-1) catalyses the degradation of haem and possesses anti-inflammatory and cytoprotective properties. The role of inflammatory mediators in the pathogenesis of OA (osteoarthritis) is becoming increasingly appreciated. In the present study, we investigated the effects of HO-1 induction in OA and healthy HACs (human articular chondrocytes) in response to inflammatory cytokine IL-1 β (interleukin-1β) under hypoxic conditions. Hypoxia was investigated as it is a more physiological condition of the avascular cartilage. Hypoxic signalling is mediated by HIFs (hypoxia-inducible factors), of which there are two main isoforms, HIF-1α and HIF-2α. Normal and OA chondrocytes were stimulated with IL-1β. This cytokine suppresses HO-1 expression and exerts both catabolic and anti-anabolic effects, while increasing HIF-1α and suppressing HIF-2α protein levels in OA chondrocytes in hypoxia. Induction of HO-1 by CoPP (cobalt protoporphyrin IX) reversed these IL-1β actions. The hypoxia-induced anabolic pathway involving HIF-2α, SOX9 [SRY (sex determining region Y)-box 9] and COL2A1 (collagen type II α1) was suppressed by IL-1β, but importantly, levels were restored by HO-1 induction, which down-regulated TNFα (tumour necrosis factor α), MMP (matrix metalloproteinase) activity and MMP-13 protein levels. Depletion of HO-1 using siRNA (small interfering RNA) abolished the CoPP effects, further demonstrating that these were due to HO-1. The results of the present study reveal the different mechanisms by which HO-1 exerts protective effects on chondrocytes in physiological levels of hypoxia.
Issues in Bilingualism and Heritage Language Maintenance: Perspectives of Minority-Language Mothers of Children With Autism Spectrum Disorders
Authors: Yu Betty
Published: February 2013

Purpose

The author investigated the language practices of 10 bilingual, Chinese/English-speaking, immigrant mothers with their children with autism spectrum disorders. The aim was to understand (a) the nature of the language practices, (b) their constraints, and (c) their impact.

Method

The author employed in-depth phenomenological interviews with thematic and narrative analyses to yield themes.

Results

Interviewees reported that they adopted language practices perceived to be advantageous to intervention access and wellness. They valued Chinese language but did not pursue its use if it was believed to hinder the children’s overall development of English acquisition. All of the mothers believed that bilingualism made learning more challenging. Many believed that it caused confusion or exacerbated disabilities. These deficit views of bilingualism were commonly reinforced by professionals. All of the mothers were motivated to help their children learn English but had no assistance to do so. Practices were sustainable only when they were aligned with families' preferred communication patterns.

Conclusions

There is an urgent need for practitioners to be better informed about issues related to intergenerational language practices in minority-language families. Language use between parents and children is a complex matter that is unique to each family. Parents need to be supported to make language use decisions that are self-enhancing and congruent with their families' needs.
The Association Between Expressive Grammar Intervention and Social and Emergent Literacy Outcomes for Preschoolers With SLI
Authors: Washington Karla N.
Published: February 2013

Purpose

To determine whether (a) expressive grammar intervention facilitated social and emergent literacy outcomes better than no intervention and (b) expressive grammar gains and/or initial expressive grammar level predicted social and emergent literacy outcomes.

Method

This investigation was a follow-up to a recently published study exploring the impact of grammatical language intervention on expressive grammar outcomes for preschoolers with specific language impairment (SLI). Twenty-two 3- to 5-year-old preschoolers received ten 20-minute intervention sessions addressing primary deficits in grammatical morphology. Participants' social and emergent literacy skills were not targeted. Twelve children awaiting intervention, chosen from the same selection pool as intervention participants, served as controls. Blind assessments of social and emergent literacy outcomes were completed at preintervention, immediately postintervention, and 3 months postintervention.

Results

Only intervention participants experienced significant gains in social and emergent literacy outcomes and maintained these gains for 3 months postintervention. Expressive grammar gains was the only single significant predictor of these outcomes.

Conclusions

Expressive grammar intervention was associated with broad impacts on social and emergent literacy outcomes that were maintained beyond the intervention period. Gains in expressive grammar predicted these outcomes. Social and emergent literacy skills were positively affected for preschoolers with SLI during a grammatical language intervention program.
An Evidence-Based Systematic Review on Cognitive Interventions for Individuals With Dementia
Authors: Hopper Tammy , Bourgeois Michelle , Pimentel Jane , Qualls Constance Dean , Hickey Ellen , Frymark Tobi , Schooling Tracy
Published: February 2013

Purpose

To evaluate the current state of research evidence related to cognitive interventions for individuals with Alzheimer’s disease or related dementias.

Method

A systematic search of the literature was conducted across 27 electronic databases based on a set of a priori questions, inclusion/exclusion criteria, and search parameters. Studies were appraised for methodological quality and categorized according to intervention technique and outcome (e.g., cognitive-communication impairment or activity limitation/participation restriction). Results were summarized and, when possible, analyzed quantitatively using indicators of treatment effect size.

Results

Forty-three studies met criteria for inclusion in the review. The most commonly used cognitive intervention techniques used were errorless learning, spaced-retrieval training, vanishing cues, or verbal instruction/cueing. Most treatment outcomes were measured at the cognitive-communication impairment level of functioning and were generally positive. However, results should be interpreted cautiously because of methodological limitations across studies.

Conclusions

Research evidence to support the use of cognitive interventions for individuals with dementia is accumulating. Researchers are beginning to evaluate treatment efficacy, yet the focus tends to be on discovery, specifically, refining intervention variables that will facilitate optimal outcomes. Implications for clinical practice and avenues for future research are discussed.
Early Maternal Language Use During Book Sharing in Families From Low-Income Environments
Authors: Abraham Linzy M. , Crais Elizabeth , Vernon-Feagans Lynne ,   and the Family Life Project Phase 1 Key Investigators
Published: February 2013

Purpose

The authors examined the language used by mothers from low-income and rural environments with their infants at ages 6 and 15 months to identify predictors of maternal language use at the 15-month time point.

Method

Maternal language use by 82 mothers with their children was documented during book-sharing interactions within the home in a prospective longitudinal study. The authors analyzed transcripts for maternal language strategies and maternal language productivity.

Results

Analyses indicated variability across mothers in their language use and revealed some stability within mothers, as maternal language use at the 6-month time point significantly predicted later maternal language. Mothers who used more language strategies at the 6-month time point were likely to use more of these language strategies at the 15-month time point, even after accounting for maternal education, family income, maternal language productivity, and children’s communicative attempts.

Conclusions

Mothers' language use with their children was highly predictive of later maternal language use, as early as age 6 months. Children’s communication also influenced concurrent maternal language productivity. Thus, programs to enhance maternal language use would need to begin in infancy, promoting varied and increased maternal language use and also encouraging children’s communication.
Importance of many-body correlations in glass transition: An example from polydisperse hard spheres
Authors: Leocmach Mathieu , Russo John , Tanaka Hajime
Published: February 2013

Most of the liquid-state theories, including glass-transition theories, are constructed on the basis of two-body density correlations. However, we have recently shown that many-body correlations, in particular, bond orientational correlations, play a key role in both the glass transition and the crystallization transition. Here we show, with numerical simulations of supercooled polydisperse hard spheres systems, that the length-scale associated with any two-point spatial correlation function does not increase toward the glass transition. A growing length-scale is instead revealed by considering many-body correlation functions, such as correlators of orientational order, which follows the length-scale of the dynamic heterogeneities. Despite the growing of crystal-like bond orientational order, we reveal that the stability against crystallization with increasing polydispersity is due to an increasing population of icosahedral arrangements of particles. Our results suggest that, for this type of systems, many-body correlations are a manifestation of the link between the vitrification and the crystallization phenomena. Whether a system is vitrified or crystallized can be controlled by the degree of frustration against crystallization, polydispersity in this case.
Translational diffusion of probe molecules under high pressure: A study by fluorescence recovery after photobleaching technique
Authors: Bonetti Marco , Roger Michel
Published: February 2013

We present fluorescence recovery measurements after photobleaching performed under high pressure in liquids that fill square-section fused silica micro-capillaries. These micro-capillaries withstand pressure up to 2500 bar for a wall thickness of about 140 μm and fit easily on the microscope stage. This technique allows the translational diffusion coefficient of fluorescent molecules in liquids to be measured as a function of pressure. When the liquid sample is far from its glass transition the translational diffusive coefficient is in agreement with the Stokes-Einstein equation. As the glass transition is approached by further increasing the pressure, decoupling of the measured diffusion coefficient from the Stokes-Einstein relation is observed. These are the first measurements that combine the fluorescence recovery technique and high hydrostatic pressures. This experimental setup can also be used either with diamond or sapphire anvil cells in order to span a larger pressure range.
Explicitly correlated atomic orbital basis second order Møller–Plesset theory
Authors: Hollman David S. , Wilke Jeremiah J. , Schaefer Henry F.
Published: February 2013

The scope of problems treatable by ab initio wavefunction methods has expanded greatly through the application of local approximations. In particular, atomic orbital (AO) based wavefunction methods have emerged as powerful techniques for exploiting sparsity and have been applied to biomolecules as large as 1707 atoms [S. A. Maurer, D. S. Lambrecht, D. Flaig, and C. Ochsenfeld, J. Chem. Phys. 136, 144107 (2012)]10.1063/1.3693908. Correlated wavefunction methods, however, converge notoriously slowly to the basis set limit and, excepting the use of large basis sets, will suffer from a severe basis set incompleteness error (BSIE). The use of larger basis sets is prohibitively expensive for AO basis methods since, for example, second-order Møller-Plesset perturbation theory (MP2) scales linearly with the number of atoms, but still scales as \documentclass[12pt]{minimal}\begin{document}$\mathcal {O}(N^5)$\end{document}O(N5) in the number of functions per atom. Explicitly correlated F12 methods have been shown to drastically reduce BSIE for even modestly sized basis sets. In this work, we therefore explore an atomic orbital based formulation of explicitly correlated MP2-F12 theory. We present working equations for the new method, which produce results identical to the widely used molecular orbital (MO) version of MP2-F12 without resorting to a delocalized MO basis. We conclude with a discussion of several possible approaches to a priori screening of contraction terms in our method and the prospects for a linear scaling implementation of AO-MP2-F12. The discussion includes concrete examples involving noble gas dimers and linear alkane chains.
High-power microwave filters and frequency selective surfaces exploiting electromagnetic wave tunneling through ϵ-negative layers
Authors: Liu Chien-Hao , Behdad Nader
Published: February 2013

In this paper, we experimentally investigate the phenomenon of electromagnetic wave tunneling through ϵ-negative (ENG) metamaterial layers surrounded by double-positive layers. Initial experiments are conducted by using a rectangular waveguide, which operates below its cutoff frequency to emulate an ENG layer. This ENG layer is then sandwiched by two dielectric substrates with relatively high dielectric constants and it is shown that the entire setup acts as a classical microwave filter with a second-order bandpass response. The power handling capability of this filter is examined experimentally using a high-power magnetron source with a frequency of 9.382 GHz, a pulse duration of 1 μs, and a peak power of 25 kW. Based on the results of this experiment, two methods for improving the power handling capability of these multi-layer structures are proposed. In particular, it is demonstrated that emulating the ENG layers with thin perforated metallic sheets with sub-wavelength holes significantly enhances their peak power handling capability. A prototype of such a device is designed, fabricated, and experimentally characterized and it is demonstrated that it can handle extremely high peak power levels. The results presented in this work are expected to be useful in designing microwave filters and frequency selective surfaces that can handle extremely high peak power levels.
A fingerprint of surface-tension anisotropy in the free-energy cost of nucleation
Authors: Prestipino Santi , Laio Alessandro , Tosatti Erio
Published: February 2013

We focus on the Gibbs free energy ΔG for nucleating a droplet of the stable phase (e.g., solid) inside the metastable parent phase (e.g., liquid), close to the first-order transition temperature. This quantity is central to the theory of homogeneous nucleation, since it superintends the nucleation rate. We recently introduced a field theory describing the dependence of ΔG on the droplet volume V, taking into account besides the microscopic fuzziness of the droplet-parent interface, also small fluctuations around the spherical shape whose effect, assuming isotropy, was found to be a characteristic logarithmic term. Here we extend this theory, introducing the effect of anisotropy in the surface tension, and show that in the limit of strong anisotropy ΔG(V) once more develops a term logarithmic on V, now with a prefactor of opposite sign with respect to the isotropic case. Based on this result, we argue that the geometrical shape that large solid nuclei mostly prefer could be inferred from the prefactor of the logarithmic term in the droplet free energy, as determined from the optimization of its near-coexistence profile.
High-temperature inert gas plasma magnetohydrodynamic energy conversion by using linear-shaped Faraday-type channel
Authors: Murakami Tomoyuki , Zhuang Yunqin , Okuno Yoshihiro
Published: February 2013

We describe high-density magnetohydrodynamic (MHD) energy conversion in a high-temperature seed-free argon plasma, for which a compact linear-shaped Faraday-type MHD electrical power generator is used. Short-time-duration single-pulse shock-tunnel-based experiments demonstrate the MHD energy conversion with varying total inflow temperature up to 9000 K and applied magnetic-flux density up to 4.0 T. The high-temperature plasma is transformed from the thermal-equilibrium state at the entrance to the weak-nonequilibrium state in the supersonic MHD channel. The discharge structure is reasonably homogeneous without suffering from serious streamer development. The power generation performance is monotonically improved by increasing total inflow temperature and strength of magnetic field. The enthalpy extraction efficiency of 13.1% and overall power density of 0.16 GW/m3 are attained. The local power density at the middle of the channel reaches 0.24 GW/m3.
Linear stability of electron flow produced by field emission
Authors: Rokhlenko A. , Lebowitz J. L.
Published: February 2013

A linear stability analysis of the planar one dimensional space charge limited flow is performed when the current is determined by a current-field relation, e.g., the Fowler-Nordheim or any other emission model. The initial velocity is assumed the same for all emitted electrons. The flow is shown to be stable with decaying oscillations depending on the nature of the emission law, including in some situations non-oscillating slowly decaying modes. When the emission variations are due only to changes of the initial flow velocity, the time of decay can be much longer than the electron transit time for a given flow setup.
Raman and photoluminescence spectroscopy of Si nanocrystals: Evidence of a form factor
Authors: Faraci Giuseppe , Mannino Giovanni , Pennisi Agata R. , Ruggeri Rosa , Sberna Paolo , Privitera Vittorio
Published: February 2013

We investigated the quantum confinement in Si nanocrystals embedded in a SiO2 matrix. The size was accurately controlled in the range 3–8 nm by annealing at high temperature Si/SiO2 multilayers fabricated by chemical vapour deposition. Raman shift and line width were compared with existing theoretical models for each cluster size. We found evidence of uni-dimensional confinement in 3 nm crystals, whereas for 4.5 nm crystals the confinement appears three-dimensional. This conclusion is supported by the luminescence spectra shifting towards higher wavelengths for the smaller size, in opposite direction for larger sizes.
Aspects of linear Landau damping in discretized systems
Authors: Bratanov Vasil , Jenko Frank , Hatch David , Brunner Stephan
Published: February 2013

Basic linear eigenmode spectra for electrostatic Langmuir waves and drift-kinetic slab ion temperature gradient modes are examined in a series of scenarios. Collisions are modeled via a Lenard-Bernstein collision operator which fundamentally alters the linear spectrum even for infinitesimal collisionality [Ng et al., Phys. Rev. Lett. 83, 1974 (1999)]. A comparison between different discretization schemes reveals that a Hermite representation is superior for accurately resolving the spectra compared to a finite differences scheme using an equidistant velocity grid. Additionally, it is shown analytically that any even power of velocity space hyperdiffusion also produces a Case-Van Kampen spectrum which, in the limit of zero hyperdiffusivity, matches the collisionless Landau solutions.
Effects of 3He impurities on the superfluid response of the 4He monolayer on a C20 molecule
Authors: Shin Hyeondeok , Kwon Yongkyung
Published: February 2013

The path-integral Monte Carlo calculations have been performed to investigate the effects of 3He impurities on structural and superfluid properties of the 4He monolayer on a single C20 molecule. According to our previous study, the helium monolayer exhibits different quantum states for different numbers of 4He adatoms and is completed to form a commensurate solid where nanoscale supersolidity can be realized through the activation of mobile vacancy states. We first observe that different structures for different numbers of helium atoms are mostly preserved with the replacement of a few 4He atoms with the same number of 3He atoms, whether the helium layer is a fluid or a solid. However, the substitution of 3He impurities is found to have different effects on the superfluid response of the helium layer, depending on its quantum state. For a partially-filled fluid layer the superfluid fraction decreases monotonically with the increasing 3He concentration, which can be understood in terms of the suppression of exchange couplings among 4He atoms due to the presence of 3He impurities. On the other hand, the substitution of a few 3He impurity atoms may increase the superfluid fraction of a near-complete monolayer that is in a crystalline solid state. The enhancement of superfluidity in a solid layer is interpreted to be due to interstitial and vacancy defects promoted by larger quantum fluctuations of lighter 3He atoms. This provides strong evidence that the 4He monolayer on C20 shows the vacancy-based supersolidity near its completion.
Influence of the supersaturation on Si diffusion and growth of Si nanoparticles in silicon-rich silica
Authors: Roussel M. , Talbot E. , Pareige P. , Gourbilleau F.
Published: February 2013

SiOX/SiO2 multilayers have been prepared using magnetron sputtering and annealed in order to induce the growth of Si nanoparticles in Si-rich sublayers. This sample has undergone several successive annealing treatments and has been analyzed using a laser-assisted tomographic atom probe. This allows the phase separation between Si and SiO2 and the growth process to be studied at the atomic scale as a function of annealing temperature. Si diffusion coefficient is estimated from the accurate measurement of matrix composition and Si particle size. We demonstrate that the diffusion coefficient in SiOX is supersaturation dependent, leading to a decrease in silicon particle growth kinetics during annealing. In addition, we use our measurements to predict the critical thickness for efficient SiO2 diffusion barriers.
Effect of antiferromagnetic thickness on thermal stability of static and dynamic magnetization of NiFe/FeMn multilayers
Authors: Phuoc Nguyen N. , Chen H. Y. , Ong C. K.
Published: February 2013

The influence of antiferromagnetic (AF) thickness on static and dynamic magnetic properties and their thermal stability in NiFe/FeMn multilayered thin films was investigated systematically. It was found that dynamic magnetic anisotropy rises at the AF thickness lower than that of static magnetic anisotropy and exchange bias. This behavior is suggested to be due to the contribution of rotatable anisotropy arising from time-dependent rotatable part of the AF spins. It is also due to the contribution of rotatable anisotropy and exchange bias that makes the thermal stability of static and dynamic anisotropies varied with AF thickness. The temperature dependences of ferromagnetic resonance frequency, Gilbert damping factor and frequency linewidth dependent on AF thickness are also discussed in conjunction with the variations of the dynamic anisotropy and exchange bias field to provide a comprehensive picture of the physical origin of their thermal stability.
Effect of hydrogen incorporation on the negative bias illumination stress instability in amorphous In-Ga-Zn-O thin-film-transistors
Authors: Noh Hyeon-Kyun , Park Ji-Sang , Chang K. J.
Published: February 2013

In amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors, negative shifts of the threshold voltage commonly occur under negative bias illumination stress (NBIS), and its origin is attributed to hole traps such as O-vacancy (VO) defects. We perform density functional calculations to investigate the effect of hydrogenation on the NBIS instability. We find that hydrogen passivates the electrical activity of VO in form of HO, in which H occupies the vacancy site. The activation energy for dissociating HO into VO and an interstitial H (Hi) is about 1.27 eV, much higher than the migration barrier of about 0.51 eV for Hi diffusion. Kinetic Monte Carlo simulations show that HO defects are quite stable upon post thermal annealing up to 200 °C. Thus, we propose that H incorporation into a-IGZO not only effectively reduces the density of VO defects but also mitigates the NBIS instability in devices fabricated at low temperatures.
Photoluminescence of radial heterostructured GaAs/AlGaAs/GaAs nanowires
Authors: Caface R. A. , Guimarães F. E. G. , Arakaki H. , de Souza C. A. , Pusep Yu. A.
Published: February 2013

Photoluminescence (PL) of high-density GaAs nanowires (NWs) encapsulated by a double AlGaAs/GaAs shell is studied. Two lines are found and assigned to the radiative recombinations of photoexcited electrons confined in the center of the GaAs core and at the heteroboundary between the outer GaAs shell and the inner AlGaAs one with the holes in the core and the holes confined at the heteroboundary between the core and the inner AlGaAs shell. The simple model, based on representation of the valence band structure using two levels, well accounts for the observed temperature dependence of the integrated photoluminescence intensities. The proposed double shell structure with tunneling transparent inner shell sets conditions for easy control of the emission energy of the heterostructured nanowires.
Visible single-photon emission from a nitrogen impurity center in AlAs
Authors: Jo M. , Mano T. , Kuroda T. , Sakuma Y. , Sakoda K.
Published: February 2013

We report visible single-photon emission from a nitrogen impurity center in AlAs grown on GaAs(001). Sharp emission lines are observed at 2.1–2.2 eV, below the X-conduction bandedge of AlAs from N δ-doped AlAs. The quadratic increase in the photoluminescence intensity with the N concentration reveals that the nitrogen impurity centers consist of NN pairs. Polarization analysis reveals that the peak at 2.191 eV consists of different pair configurations, while the peak at 2.165 eV contains only a single pair configuration along the 〈110〉 direction. Photon correlation measurement gives the second-order correlation function g(2)(0) = 0.33, demonstrating single-photon statistics in emissions from an NN pair.
Fabrication of nanopores in 1 nm thick carbon nanomembranes with slow highly charged ions
Authors: Ritter Robert , Wilhelm Richard A. , Stöger-Pollach Michael , Heller René , Mücklich Arndt , Werner Udo , Vieker Henning , Beyer André , Facsko Stefan , Gölzhäuser Armin , Aumayr Friedrich
Published: February 2013

We describe the use of slow highly charged ions as a simple tool for the fabrication of nanopores with well-defined diameters typically between 10 and 20 nm in freestanding, 1 nm thick carbon nanomembranes (CNMs). When CNMs are exposed to a flux of highly charged ions, for example Xe40+, each individual ion creates a circular nanopore, the size of which depends on the kinetic and potential energy of the impinging ion. The controlled fabrication of nanopores with a uniform size opens a path for the application of CNM based filters in nanobiotechnology.
Green-tea modified multiwalled carbon nanotubes for efficient poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate)/n-silicon hybrid solar cell
Authors: Khatri Ishwor , Tang Zeguo , Liu Qiming , Ishikawa Ryo , Ueno Keiji , Shirai Hajime
Published: February 2013

Poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate) (PEDOT:PSS)/n-Si hybrid solar cells were studied with and without embedding green-tea modify multiwalled carbon nanotubes (MWCNTs) at interface. Devices fabricated with embedding green-tea modified MWCNTs show much better performance than that of a device without MWCNTs with short circuit current density (Jsc), open circuit voltage (Voc), fill factor, and power conversion efficiency (η) as 30.31 mA/cm2, 0.54 V, 0.66, and 10.93%, respectively. Here, we believe that green-tea disperse MWCNTs bundles to individual and its incorporation improved built-in potential (Vb) of the device for better hole transport, easy exciton splitting, and suppression of charge recombination, thereby improving photovoltaic response.
Low-loss tunable metamaterials using superconducting circuits with Josephson junctions
Authors: Jung P. , Butz S. , Shitov S. V. , Ustinov A. V.
Published: February 2013

We report on experiments with superconducting metamaterials containing Josephson junctions. In these structures, split-ring resonators used in conventional metamaterials are replaced by superconducting loops that are interrupted by Josephson junctions, so called rf-SQUIDs. Like the split-ring resonators, these elements can be seen as LC-resonators that couple to the magnetic field. The advantage of superconducting thin-film metamaterials is that, due to the tunable intrinsic inductance of the Josephson junction, the resonance frequency of the rf-SQUID can be changed by applying an external dc magnetic field. We present experimental results that demonstrate the tunability of the resonance frequency of these devices.
Periodic spatial variation of the electron-phonon interaction in epitaxial graphene on Ru(0001)
Authors: Castellanos-Gomez Andres , Rubio-Bollinger Gabino , Barja Sara , Garnica Manuela , Vázquez de Parga Amadeo L. , Miranda Rodolfo , Agraït Nicolás
Published: February 2013

We have performed low temperature scanning tunnelling spectroscopy measurements on graphene epitaxially grown on Ru(0001). An inelastic feature, related to the excitation of a vibrational breathing mode of the graphene lattice, was found at 360 meV. The change in the differential electrical conductance produced by this inelastic feature, which is associated with the electron-phonon interaction strength, varies spatially from one position to other of the graphene supercell. This inhomogeneity in the electronic properties of graphene on Ru(0001) results from local variations of the carbon–ruthenium interaction due to the lattice mismatch between the graphene and the Ru(0001) lattices.
Reworking the Spaces of Indigeneity: The Bolivian Ayllu and Lowland Autonomy Movements Compared
Authors: Perreault Tom , Green Barbara
Published: February 2013

This paper examines the political uses of indigenous identity and how understandings of indigeneity are changing in contemporary Bolivia. In particular we address two interrelated questions: first, in what ways are understandings of indigeneity and the ‘indigenous’ changing in Bolivia, and to what effect? And, second, how does indigeneity inform conceptualizations of territory and the nation? We examine two ethnoterritorial projects and the organizations that represent them, in two different regions of Bolivia: the ayllu movement, as represented by the National Council of Ayllus and Markas of Qullasuyu and the Andean Oral History Workshop, and the lowland autonomy movement, as represented by the Camba Nation and the pro-Santa Cruz Committee. We argue that both the ayllu movement and the lowland autonomy movement are ethnoterritorial projects which mobilize essentialized understandings of indigenous identity in order to legitimate historical claims to territorial and political rights.
Enhancing the chelation capacity of rice to maximise iron and zinc concentrations under elevated atmospheric carbon dioxide
Authors: Johnson Alexander A. T.
Published: February 2013

Roughly half of the Earth’s seven billion people rely on rice as their primary source of food. The milled grain of rice, often referred to as polished or white rice, serves as a rich source of energy but is low in protein and several essential micronutrients such as iron and zinc. As a result, billions of people in rice-based countries suffer the debilitating effects of protein-energy and micronutrient malnutrition with symptoms including iron-deficiency anaemia, growth retardation and blindness. By 2050, the Earth’s atmospheric carbon dioxide concentration ([CO2]) is expected to reach 550 μmol mol–1, representing a 70% increase from today’s concentration of 392 μmol mol–1. The impacts of elevated [CO2] on plant growth will likely include agronomically useful traits such as increased biomass, yield and water-use efficiency. However, increased plant productivity is likely to be accompanied by decreased protein and micronutrient mineral concentrations of cereal grain. This review focuses on the effects of carbon dioxide-enrichment on rice physiology and nutritional composition and proposes increased activity of the Strategy II iron uptake pathway as a promising method to maintain or increase iron and zinc concentrations in rice grain, and perhaps cereal grain in general, under elevated [CO2].
Spectral assessments of wheat plants grown in pots and containers under saline conditions
Authors: Hackl Harald , Mistele Bodo , Hu Yuncai , Schmidhalter Urs
Published: February 2013

Spectral measurements allow fast nondestructive assessment of plant traits under controlled greenhouse and close-to-field conditions. Field crop stands differ from pot-grown plants, which may affect the ability to assess stress-related traits by nondestructive high-throughput measurements. This study analysed the potential to detect salt stress-related traits of spring wheat (Triticum aestivum L.) cultivars grown in pots or in a close-to-field container platform. In two experiments, selected spectral indices assessed by active and passive spectral sensing were related to the fresh weight of the aboveground biomass, the water content of the aboveground biomass, the leaf water potential and the relative leaf water content of two cultivars with different salt tolerance. The traits were better ascertained by spectral sensing of container-grown plants compared with pot-grown plants. This may be due to a decreased match between the sensors’ footprint and the plant area of the pot-grown plants, which was further characterised by enhanced senescence of lower leaves. The reflectance ratio R760 : R670, the normalised difference vegetation index and the reflectance ratio R780 : R550 spectral indices were the best indices and were significantly related to the fresh weight, the water content of the aboveground biomass and the water potential of the youngest fully developed leaf. Passive sensors delivered similar relationships to active sensors. Across all treatments, both cultivars were successfully differentiated using either destructively or nondestructively assessed parameters. Although spectral sensors provide fast and qualitatively good assessments of the traits of salt-stressed plants, further research is required to describe the potential and limitations of spectral sensing.
Effects of NaCl addition to the growing medium on plant hydraulics and water relations of tomato
Authors: Trifilò Patrizia , Lo Gullo Maria Assunta , Raimondo Fabio , Salleo Sebastiano , Nardini Andrea
Published: February 2013

This work reports on experimental evidence for the role of ion-mediated changes of xylem hydraulic conductivity in the functional response of Solanum lycopersicum L. cv. Naomi to moderate salinity levels. Measurements were performed in fully developed 12-week-old plants grown in half-strength Hoagland solution (control, C-plants) or in the same solution added with 35 mM NaCl (NaCl-plants). NaCl-plants produced a significantly less but heavier leaves and fruits but had similar gas-exchange rates as control plants. Moreover, NaCl-plants showed higher vessel multiple fraction (FVM) than control plants. Xylem sap potassium and sodium concentrations were significantly higher in NaCl-plants than in control plants. When stems were perfused with 10 mM NaCl or KCl, the hydraulic conductance of NaCl plants was nearly 1.5 times higher than in control plants. Accordingly, stem hydraulic conductance measured in planta was higher in NaCl- than in control plants. Our data suggest that tomato plants grown under moderate salinity upregulate xylem sap [Na+] and [K+], as well as sensitivity of xylem hydraulics to sap ionic content, thus, increasing water transport capacity.
Elasticity, structure, and relaxation of extended proteins under force
Authors: Stirnemann Guillaume , Giganti David , Fernandez Julio M. , Berne B. J.
Published: February 2013

Force spectroscopies have emerged as a powerful and unprecedented tool to study and manipulate biomolecules directly at a molecular level. Usually, protein and DNA behavior under force is described within the framework of the worm-like chain (WLC) model for polymer elasticity. Although it has been surprisingly successful for the interpretation of experimental data, especially at high forces, the WLC model lacks structural and dynamical molecular details associated with protein relaxation under force that are key to the understanding of how force affects protein flexibility and reactivity. We use molecular dynamics simulations of ubiquitin to provide a deeper understanding of protein relaxation under force. We find that the WLC model successfully describes the simulations of ubiquitin, especially at higher forces, and we show how protein flexibility and persistence length, probed in the force regime of the experiments, are related to how specific classes of backbone dihedral angles respond to applied force. Although the WLC model is an average, backbone model, we show how the protein side chains affect the persistence length. Finally, we find that the diffusion coefficient of the protein’s end-to-end distance is on the order of 10
8
nm
2
/s, is position and side-chain dependent, but is independent of the length and independent of the applied force, in contrast with other descriptions.
Environmental Correlates of Upstream Migration of Yellow‐Phase American Eels in the Potomac River Drainage
Authors: Welsh Stuart A. , Liller Heather L.
Published: February 2013

Assessing the relationships between upstream migration and environmental variables is important to understanding the ecology of yellow‐phase American Eels Anguilla rostrata. During an American Eel migration study within the lower Shenandoah River (Potomac River drainage), we counted and measured American Eels at the Millville Dam eel ladder for three periods: 14 May–23 July 2004, 7–30 September 2004, and 1 June–31 July 2005. Using generalized estimating equations, we modeled each time series of daily American Eel counts by fitting time‐varying environmental covariates of lunar illumination (LI), river discharge (RD), and water temperature (WT), including 1‐d and 2‐d lags of each covariate. Information‐theoretic approaches were used for model selection and inference. A total of 4,847 American Eels (19–74 cm total length) used the ladder during the three periods, including 2,622 individuals during a 2‐d span following a hurricane‐induced peak in river discharge. Additive‐effects models of RD + WT, a 2‐d lag of LI + RD, and LI + RD were supported for the three periods, respectively. Parameter estimates were positive for river discharge for each time period, negative for lunar illumination for two periods and positive for water temperature during one period. Additive‐effects models supported synergistic influences of environmental variables on the upstream migration of yellow‐phase American Eels, although river discharge was consistently supported as an influential correlate of upstream migration.
Impact of the International Nosocomial Infection Control Consortium (INICC) Multidimensional Hand Hygiene Approach over 13 Years in 51 Cities of 19 Limited-Resource Countries from Latin America, Asia, the Middle East, and Europe
Authors: Rosenthal Victor D. , Pawar Mandakini , Leblebicioglu Hakan , Navoa-Ng Josephine Anne , Villamil-Gómez Wilmer , Armas-Ruiz Alberto , Cuéllar Luis E. , Medeiros Eduardo A. , Mitrev Zan , Gikas Achilleas , Yang Yun , Ahmed Altaf , Kanj Souha S. , Dueñas Lourdes , Gurskis Vaidotas , Mapp Trudell , Guanche-Garcell Humberto , Fernández-Hidalgo Rosalía , Kübler Andrzej
Published: February 2013

Objective.

To assess the feasibility and effectiveness of the International Nosocomial Infection Control Consortium (INICC) multi-dimensional hand hygiene approach in 19 limited-resource countries and to analyze predictors of poor hand hygiene compliance.

Design.

An observational, prospective, cohort, interventional, before-and-after study from April 1999 through December 2011. The study was divided into 2 periods: a 3-month baseline period and a 7-year follow-up period.

Setting.

Ninety-nine intensive care unit (ICU) members of the INICC in Argentina, Brazil, China, Colombia, Costa Rica, Cuba, El Salvador, Greece, India, Lebanon, Lithuania, Macedonia, Mexico, Pakistan, Panama, Peru, Philippines, Poland, and Turkey.

Participants.

Healthcare workers at 99 ICU members of the INICC.

Methods.

A multidimensional hand hygiene approach was used, including (1) administrative support, (2) supplies availability, (3) education and training, (4) reminders in the workplace, (5) process surveillance, and (6) performance feedback. Observations were made for hand hygiene compliance in each ICU, during randomly selected 30-minute periods.

Results.

A total of 149,727 opportunities for hand hygiene were observed. Overall hand hygiene compliance increased from 48.3% to 71.4% (P < .01). Univariate analysis indicated that several variables were significantly associated with poor hand hygiene compliance, including males versus females (63% vs 70%; P<.001), physicians versus nurses (62% vs 72%; P<.001), and adult versus neonatal ICUs (67% vs 81%; P<.001), among others.

Conclusions.

Adherence to hand hygiene increased by 48% with the INICC approach. Specific programs directed to improve hand hygiene for variables found to be predictors of poor hand hygiene compliance should be implemented.
Chern-Simons classes and the Ricci flow on 3-manifolds
Authors: Godbout Christopher
Published: February 2013

In 1974, S.-S. Chern and J. Simons published a paper where they defined a new type of characteristic class, one that depends not just on the topology of a manifold but also on the geometry. The goal of this paper is to investigate what kinds of geometric information is contained in these classes by studying their behavior under the Ricci flow. In particular, it is shown that the Chern-Simons class corresponding to the first Pontryagin class is invariant under the Ricci flow on the warped products

S
2

×
f

S
1

S^2\times _f S^1

and

S
1

×
f

S
2

S^1 \times _f S^2

but that this class is not invariant under the Ricci flow on a generalized Berger sphere.
Fourier transform of anisotropic Hardy spaces
Authors: Bownik Marcin , Wang Li-An
Published: February 2013

We show that if

f
f

is in an anisotropic Hardy space

H
A
p

H_A^p

,

0
>
p
≤
1

0 > p \leq 1

, with respect to a dilation matrix

A
A

, then its Fourier transform

f
^

\hat {f}

satisfies the pointwise estimate
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartAbsoluteValue ModifyingAbove f With caret left-parenthesis xi right-parenthesis EndAbsoluteValue less-than-or-equal-to upper C StartAbsoluteValue EndAbsoluteValue f StartAbsoluteValue EndAbsoluteValue Subscript upper H Sub Subscript upper A Sub Superscript p Subscript Baseline rho Subscript asterisk Baseline left-parenthesis xi right-parenthesis Superscript StartFraction 1 Over p EndFraction minus 1 Baseline period">

|

f
^

(
ξ
)

|

≤
C

|

|

f

|

|

H
A
p

ρ
∗

(
ξ

)

1
p

−
1

.

|\hat f(\xi )| \le C ||f||_{H^p_A} \rho _*(\xi )^{\frac {1}{p}-1}.

\]
Here,

ρ
∗

\rho _*

is a quasi-norm associated with the transposed matrix

A
∗

A^*

. This leads to necessary conditions for functions

m
m

to be multipliers on

H
A
p

H_A^p

, as well as further pointwise characterizations on

f
^

\hat {f}

and a generalization of the Hardy-Littlewood inequality on the integrability of

f
^

\hat {f}

. This last result is strengthened through the use of rearrangement functions.