bluuebunny/crossref_metadata_2025 huggingface dataset:
Southern Ocean seasonal temperature and Subtropical Front movement on the South Tasman Rise in the late Quaternary
Authors: Sikes E. L. , Howard W. R. , Samson C. R. , Mahan T. S. , Robertson L. G. , Volkman J. K.
Published: April 2009

The Subtropical Front (STF) marking the northern boundary of the Southern Ocean has a steep gradient in sea surface temperature (SST) of approximately 4°C over 0.5° of latitude. Presently, in the region south of Tasmania, the STF lies nominally at 47°S in the summer and 45°S in the winter. We present here SST reconstructions in a latitudinal transect of cores across the South Tasman Rise, southeast of Australia, during the late Quaternary. SST reconstructions are based on two paleotemperature proxies, alkenones and faunal assemblages, which are used to assess past changes in SST in spring and summer. The north‐south alignment in core locations allows reconstruction of movement of the STF over the last 100 ka. Surface water temperatures during the last glaciation in this region were ∼4°C colder than today. Additional temperature changes greater in magnitude than 4°C seen in individual cores can be attributed to changes in the water mass overlying the core site caused by the movement of the front across that location. During the penultimate interglacial, SST was ∼2°C warmer and the STF was largely positioned south of 47°S. Movement of the STF to the north occurred during cool climate periods such as the last marine isotope stages 3 and 4. In the last glaciation, the front was at its farthest north position, becoming pinned against the Tasmanian landmass. It moved south by 4° latitude to 47°S in summer during the deglaciation but remained north of 45°S in spring throughout the early deglaciation. After 11 ka B.P. inferred invigoration of the East Australia Current appears to have pushed the STF seasonally south of the East Tasman Plateau, until after 6 ka B.P. when it achieved its present configuration.
Large Coastal Landslides and Tsunami Hazard in the Caribbean
Authors: Teeuw Richard , Rust Derek , Solana Carmen , Dewdney Chris , Robertson Richard
Published: April 2009

With nine volcanic peaks in a 750‐square‐kilometer area, Dominica, in the Lesser Antilles volcanic arc (Figure 1), has one of the highest concentrations of potentially active volcanoes in the world [Lindsay et al., 2005]. Dominica is very hilly, and there have been numerous landslides, particularly on the island's wetter eastern and northern coasts.

Lindsay et al. [2005] consider the likelihood of gravitational collapses on the flanks of Dominica's volcanoes to be “low but not negligible.” However, many factors make Dominica particularly prone to large landslides (>1 million tons): (1) extensive zones of weakened rock, due to hydrothermal alteration and/or intense tropical weathering; (2) oversteepened slopes associated with tectonic uplift and erosion of volcanic edifice foot slopes; (3) large amounts of rainfall on the volcanic uplands, especially during the hurricane season (June–October), with annual averages of up to approximately 6000 millimeters; and (4) occasional severe seismic activity, e.g., a magnitude 7.3 earthquake on 29 November 2007, with its epicenter between Dominica and Martinique, and another of magnitude 6.2 on 21 November 2004, with its epicenter between Dominica and Guadeloupe.
Early 21st‐Century Drought in Mexico
Authors: Stahle David W. , Cook Edward R. , Díaz Jose Villanueva , Fye Falko K. , Burnette Dorian J. , Griffin Daniel , Soto Rodolfo Acuña , Seager Richard , Heim Richard R.
Published: April 2009

Prolonged drought conditions have persisted over western North America since at least 1999, affecting snowpack, stream discharge, reservoir levels, and wildfire activity [Mote et al., 2005; Westerling et al., 2006; MacDonald et al., 2008]. Instrumental precipitation, temperature, and Palmer Drought Severity Indices (PDSI) indicate that severe and sustained drought began in 1994 in Mexico, where it has continued with only limited relief for the past 15 years. This late twentieth‐and early 21st‐century Mexican drought (referred to below as the [early 21st‐century drought]) has equaled some aspects of the 1950s drought, which is the most severe drought evident in the instrumental climate record for Mexico (1900–2008). Large‐scale changes in ocean‐atmospheric circulation have contributed to the lower than normal precipitation that has led to the current drought [Seager, 2007], but global warming and the sharp regional warming across Mexico, which appears to have been aggravated by land cover changes [Englehart and Douglas, 2005], may have added an anthropogenic component to the early 21st‐century drought.
Shallow Submarine Hydrothermal Systems in the Aeolian Volcanic Arc, Italy
Authors: Monecke Thomas , Petersen Sven , Lackschewitz Klas , Hügler Michael , Hannington Mark D. , Gemmell J. Bruce
Published: April 2009

The majority of known high‐temperature hydrothermal vents occur at mid‐ocean ridges and back‐arc spreading centers, typically at water depths from 2000 to 4000 meters. Compared with 30 years of hydrothermal research along spreading centers in the deep parts of the ocean, exploration of the approximately 700 submarine arc volcanoes is relatively recent [de Ronde et al., 2003]. At these submarine arc volcanoes, active hydrothermal vents are located at unexpectedly shallow water depth (95% at <1600‐meter depth), which has important consequences for the style of venting, the nature of associated mineral deposits, and the local biological communities.

As part of an ongoing multinational research effort to study shallow submarine volcanic arcs, two hydrothermal systems in the submerged part of the Aeolian arc have been investigated in detail during research cruises by R/V Poseidon (July 2006) and R/V Meteor (August 2007). Comprehensive seafloor video surveys were conducted using a remotely operated vehicle, and drilling to a depth of 5 meters was carried out using a lander‐type submersible drill. This research has resulted in the first detailed, three‐dimensional documentation of shallow submarine hydrothermal systems on arc volcanoes.
Do We Need Better Predictions to Adapt to a Changing Climate?
Authors: Dessai Suraje , Hulme Mike , Lempert Robert , Pielke Roger
Published: April 2009

Many scientists have called for a substantial new investment in climate modeling to increase the accuracy, precision, and reliability of climate predictions. Such investments are often justified by asserting that failure to improve predictions will prevent society from adapting successfully to changing climate. This Forum questions these claims, suggests limits to predictability, and argues that society can (and indeed must) make effective adaptation decisions in the absence of accurate and precise climate predictions.
Functional GacS in Pseudomonas DSS73 prevents digestion by Caenorhabditis elegans and protects the nematode from killer flagellates
Authors: Bjørnlund Lisa , Rønn Regin , Péchy-Tarr Maria , Maurhofer Monika , Keel Christoph , Nybroe Ole
Published: April 2009

The success of biocontrol bacteria in soil depends in part on their ability to escape predation. We explored the interactions between Pseudomonas strain DSS73 and two predators, the nematode Caenorhabditis elegans and the flagellate Cercomonas sp. Growth of the nematode in liquid culture was arrested when it was feeding on DSS73 or a DSS73 mutant (DSS73-15C2) unable to produce the biosurfactant amphisin, whereas a regulatory gacS mutant (DSS73-12H8) that produces no exoproducts supported fast growth of the nematode. The flagellate Cercomonas sp. was able to grow on all three strains. The biosurfactant-deficient DSS73 mutant caused severe dilation of the nematode gut. In three-species systems (DSS73, Cercomonas and C. elegans), the nematodes fed on the flagellates, which in turn grazed the bacteria and the number of C. elegans increased. The flagellates Cercomonas sp. usually kill C. elegans. However, DSS73 protected the nematodes from flagellate killing. Soil microcosms inoculated with six rhizobacteria and grazed by nematodes were colonized more efficiently by DSS73 than similar systems grazed by flagellates or without grazers. In conclusion, our results suggest that C. elegans and DSS73 mutually increase the survival of one another in complex multispecies systems and that this interaction depends on the GacS regulator.
Microarray analysis of phosphate regulation in the marine cyanobacterium Synechococcus sp. WH8102
Authors: Tetu Sasha G , Brahamsha Bianca , Johnson Daniel A , Tai Vera , Phillippy Katherine , Palenik Brian , Paulsen Ian T
Published: April 2009

Primary productivity of open ocean environments, such as those inhabited by marine picocyanobacteria, is often limited by low inorganic phosphate (P). To observe how these organisms cope with P starvation, we constructed a full genome microarray for Synechococcus sp. WH8102 and compared differences in gene expression under P-replete and P-limited growth conditions, including both early P stress, during extracellular alkaline phosphatase induction, and late P stress. A total of 36 genes showed significant upregulation (>log2 fold) whereas 23 genes were highly downregulated at the early time point; however, these changes in expression were maintained during late P stress for only 5 of the upregulated genes. Knockout mutants were constructed for genes SYNW0947 and SYNW0948, comprising a two-component regulator hypothesized to have a key function in regulating P metabolism. A high degree of overlap in the sets of genes affected by P stress conditions and in the knockout mutants supports this hypothesis; however, there is some indication that other regulators may be involved in this response in Synechococcus sp. WH8102. Consistent with what has been observed in many other cyanobacteria, the Pho regulon of this strain is comprised largely of genes for alkaline phosphatases, P transport or P metabolism. Interestingly, however, the exact composition and arrangement of the Pho regulon appears highly variable in marine cyanobacteria.
Bias in assessments of marine microbial biodiversity in fosmid libraries as evaluated by pyrosequencing
Authors: Temperton Ben , Field Dawn , Oliver Anna , Tiwari Bela , Mühling Martin , Joint Ian , Gilbert Jack A
Published: April 2009

On the basis of 16S rRNA gene sequencing, the SAR11 clade of marine bacteria has an almost universal distribution, being detected as abundant sequences in all marine provinces. Yet, SAR11 sequences are rarely detected in fosmid libraries, suggesting that the widespread abundance may be an artefact of PCR cloning and that SAR11 has a relatively low abundance. Here the relative abundance of SAR11 is explored in both a fosmid library and a metagenomic sequence data set from the same biological community taken from fjord surface water from Bergen, Norway. Pyrosequenced data and 16S clone data confirmed an 11–15% relative abundance of SAR11 within the community. In contrast, not a single SAR11 fosmid was identified in a pooled shotgun sequence data set of 100 fosmid clones. This underrepresentation was evidenced by comparative abundances of SAR11 sequences assessed by taxonomic annotation and fragment recruitment. Analysis revealed a similar underrepresentation of low-GC Flavobacteriaceae. We speculate that a contributing factor towards the fosmid bias may be DNA fragmentation during preparation because of the low GC content of SAR11 sequences and other underrepresented taxa. This study suggests that, although fosmid libraries can be extremely useful, caution must be taken when directly inferring community composition from metagenomic fosmid libraries.
RCT of a High‐protein Diet on Hunger Motivation and Weight‐loss in Obese Children: An Extension and Replication
Authors: Duckworth Lauren C. , Gately Paul J. , Radley Duncan , Cooke Carlton B. , King Roderick F.G.J. , Hill Andrew J.
Published: April 2009

This study aimed to evaluate the weight loss and hunger motivation effects of an energy‐restricted high‐protein (HP) diet in overweight and obese children. In total, 95 overweight and obese children attended an 8‐week (maximum) program of physical activity, reduced‐energy intake, and behavior change education. Children were randomly assigned to one of two isoenergetic diets (standard (SP): 15% protein; HP: 25% protein), based on individually estimated energy requirements. Anthropometry and body composition were assessed at the start and end of the program and appetite and mood ratings completed on the first 3 consecutive weekdays of each week children attended camp. The HP diet had no greater effect on weight loss, body composition, or changes in appetite or mood when compared to the SP diet. Overall, campers lost 5.2 ± 3.0 kg in body weight and reduced their BMI standard deviation score (sds) by 0.25. Ratings of desire to eat increased significantly over the duration of the intervention, irrespective of diet. This is the third time we have reported an increase in hunger motivation in weight‐loss campers and replicates our previous failure to block this with a higher protein diet. Further work is warranted into the management of hunger motivation as a result of negative energy balance.
Autophagy in disease: a double-edged sword with therapeutic potential
Authors: Martinet Wim , Agostinis Patrizia , Vanhoecke Barbara , Dewaele Michael , de Meyer Guido R. Y.
Published: April 2009

Autophagy is a catabolic trafficking pathway for bulk destruction and turnover of long-lived proteins and organelles via regulated lysosomal degradation. In eukaryotic cells, autophagy occurs constitutively at low levels to perform housekeeping functions, such as the destruction of dysfunctional organelles. Up-regulation occurs in the presence of external stressors (e.g. starvation, hormonal imbalance and oxidative stress) and internal needs (e.g. removal of protein aggregates), suggesting that the process is an important survival mechanism. However, the occurrence of autophagic structures in dying cells of different organisms has led to the hypothesis that autophagy may also have a causative role in stress-induced cell death. The identification within the last decade of a full set of genes essential for autophagy in yeast, the discovery of human orthologues and the definition of signalling pathways regulating autophagy have accelerated our molecular understanding and interest in this fundamental process. A growing body of evidence indicates that autophagy is associated with heart disease, cancer and a number of neurodegenerative disorders, such as Alzheimer's, Parkinson's and Huntington's diseases. Furthermore, it has been demonstrated that autophagy plays a role in embryogenesis, aging and immunity. Recently, it has been shown that autophagy can be intensified by specific drugs. The pharmacological modulation of the autophagic pathway represents a major challenge for clinicians to treat human disease.
Field detection in MgO magnetic tunnel junctions with superparamagnetic free layer and magnetic flux concentrators
Authors: Almeida J. M. , Freitas P. P.
Published: April 2009

Magnetic tunnel junctions (MTJs) were deposited with CoFeB free layer thickness ranging from 1.3 to 3 nm. The samples were processed with areas of 10, 100, and 1000 μm2, presented RA products of ∼10 kΩ μm2, and tunneling magnetoresistance ratio values varying from ∼10% (t=1.3 nm) to ∼210% (t=3 nm). All the samples with t<1.5 nm presented linear responses (coercivity of <1 Oe) for all the studied areas; this behavior was associated with the CoFeB free layer transition from ferromagnetic to superparamagnetic. Noise measurements made in samples with superparamagnetic free layer showed negligible magnetic noise in the sensitive region. The sensitivity loss caused by the reduced free layer thickness was partially recovered using magnetic flux concentrators (MFCs). The MFC had a maximum gain of ∼3, a limited value to ensure a uniform gain for the MTJs with larger area (up to 1000 μm2). The MFC’s influence on the sensor’s noise behavior appears to increase with the sensor area, for both white noise background and frequency dependent noise.
Imaging the rotationally state-selected NO(A,n) product from the predissociation of the A state of the NO–Ar van der Waals cluster
Authors: Roeterdink Wim G. , Strecker Kevin E. , Hayden Carl C. , Janssen Maurice H. M. , Chandler David W.
Published: April 2009

The origin of the resonant structures in the spectrum of the predissociative part of the A state in the NO–Ar van der Waals cluster has been investigated. We have employed direct excitation to the predissociative part of the NO–Ar A state followed by rotational state selective ionization of the NO fragment. Velocity map imaging of the NO ion yields the recoil energy of the rotational state-selected fragment. A substantial contribution of rotational hotbands to the resonant structures is observed. Our data indicate that a centrifugal barrier as the origin of these resonances can be ruled out. We hypothesize that after the NO–Ar cluster is excited to the A state sufficient mixing within the rotating cluster takes place as it changes geometry from being T shaped in the NO(X)–Ar state to linear in the NO(A)–Ar state. This mixing allows the low energy and high angular momentum (J≈4.5) tumbling motion of the initially populated hotbands in the ground state NO(X)–Ar complex to be converted into NO(A,n=2) spinning rotation in the A state of the complex. The electronically excited spinning complex falls apart adiabatically producing rotationally excited NO(A,n=2) at the energetic threshold. This interpretation indicates that the resonances can be attributed to some type of vibrational Feshbach resonance. The appearance energy for the formation of NO(A,n=0)+Ar is found to be 44294.3±1.4cm−1.
Critical behavior of the specific heat of manganites La1−xAgxMnO3 (x=0.1,0.15,0.2) near the Curie point
Authors: Gamzatov A. G. , Khizriev K. Sh. , Batdalov A. B. , Abdulvagidov Sh. B. , Aliev A. M. , Melnikov O. V. , Gorbenko O. Yu.
Published: April 2009

An investigation of the critical behavior of the specific heat of the manganites La1−xAgxMnO3 ×(x=0.1,0.15,0.2) near the Curie temperature is carried out. The behavior of the universal critical parameters near the phase transition point is established. All of the samples studied correspond to the ferromagnetic Heisenberg 3D universality class of critical behavior, with the critical exponent α=−0.115, −0.106, and −0.106 for La0.9Ag0.1MnO3, La0.85Ag0.15MnO3, and La0.8Ag0.2MnO3, respectively. It is shown that the universality class of the critical behavior of the specific heat of the manganites La1−xAgxMnO3 is independent of the silver concentration.
Catalysis of impurities coalescence by quantized vortices in superfluid helium with nanofilament formation
Authors: Gordon E. B. , Okuda Y.
Published: April 2009

A dramatic effect of quantized vortices in superfluid helium on the rate of coalescence of suspended impurities has been predicted; such a catalytic process should result in the formation of fiber-like structures having primarily nanothickness. That should be valid for any impurity and it may be used as a basis for a universal method of producing nanowires and nanotubes. Experiments on the imbedding of molecular hydrogen into liquid helium have supported these conclusions. They showed that: (i) in normal liquid He the coalescence led to the formation of spherical microparticles carried by turbulent motion of the liquid; (ii) in the superfluid only very long filaments were observed, which behaved as quantized vortices should do. These filaments are fiber-like hydrogen crystals and survive the transition of the liquid helium to the normal state. The promises for using this phenomenon in basic and applied sciences are outlined.
Density profiles around nanoparticles and distant perturbations
Authors: Eisenriegler E.
Published: April 2009

We investigate how density profiles around a spherical nanoparticle in a critical solvent are affected by distant perturbations such as a wall or other particles. Using a new type of “fusion expansion,” we evaluate the isotropic and anisotropic changes in the densities at distances r from the sphere center which are of the order of the sphere radius R, with both R and r much smaller than the correlation length and the distance between the sphere and the perturbations. Our results bridge the gap between the changes in the region 0<r−R⪡R close to the sphere surface that determine the local pressure and force on the spherical particle and in the more distant region R⪡r where the “small sphere expansion” applies. Applications to particles in critical binary liquid mixtures and in solutions of long, flexible nonadsorbing polymers are considered.
A hierarchy of potential energy surfaces constructed from energies and energy derivatives calculated on grids
Authors: Matito Eduard , Toffoli Daniele , Christiansen Ove
Published: April 2009

In this work we develop and test a methodology for the generation of Born–Oppenheimer potential energy surfaces (PES) for use in vibrational structure calculations. The method relies on the widely used restricted-mode-coupling expansion of the fully coupled potential surface where only up to n or less vibrational coordinates are coupled in the potential. Low-order derivatives of the energy are then used to extrapolate the higher mode-coupling potential terms; derivative information is thus used in a convenient way for the evaluation of higher mode couplings avoiding their explicit calculation on multidimensional grids. The formulation, which is a variant of the popular modified Shepard interpolation, is general for any extrapolation of (n+p)-mode-coupling terms from n-mode couplings and can be applied to the energy or any other molecular property surface for which derivative information is available. The method depends only on analytical parameter-free weight functions that satisfy important limiting conditions and control the contribution from each direction of extrapolation. The procedure has been applied on a representative set of 13 molecules, and its accuracy has been tested using only gradients and using both gradients and Hessians. The results provide evidence for the importance of higher mode couplings and illustrate the cost efficiency of the proposed approach.
Magnetic, ferroelectric, and dielectric properties of Bi(Sc0.5Fe0.5)O3–PbTiO3 thin films
Authors: Yan F. , Sterianou I. , Miao S. , Reaney I. M. , Lai M. O. , Lu L.
Published: April 2009

Bi ( Sc 0.5 Fe 0.5 ) O 3 – PbTiO 3 (BSF-PT) thin films with a composition in the vicinity of a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases have been grown on LaNiO3/SiO2/Si substrates at 550 °C and 150 mTorr by pulsed laser deposition. The dielectric properties of the film were enhanced due to high crystallinity, low porosity, and the vicinity of the MPB. A saturated ferroelectric hysteresis loop was obtained with 2Pr=76 μC/cm, and the leakage current was minimized by cooling the samples, postdeposition in O2. Magnetic measurements revealed that BSF-PT thin films were antiferromagnetic confirming their anticipated multiferroic nature.
Quantum rate dynamics for proton transfer reactions in condensed phase: The exact hierarchical equations of motion approach
Authors: Chen Liping , Shi Qiang
Published: April 2009

We apply the recently developed Liouville space hierarchical equations of motion (HEOM) method to calculate the quantum rate dynamics for a model system of proton transfer reaction in condensed phase, which consist of a double well coupled to a harmonic bath with the Debye spectral density. The HEOM method provides a new way to directly calculate nonequilibrium reduced system dynamics, and the calculated reaction rate constants compare well with previous numerical exact results. The HEOM method also allows us to perform long time simulations, which enables systematic studies of the reaction dynamics at low frictions. The applicability of perturbative quantum master equations at various orders is also investigated by comparing with numerical exact HEOM results.
The role of the nϕ=1 column mode in spheromak formation
Authors: Cohen B. I. , Romero-Talamás C. A. , Ryutov D. D. , Hooper E. B. , LoDestro L. L. , McLean H. S. , Stewart T. L. , Wood R. D.
Published: April 2009

Observations in strongly driven spheromak experiments and simulations using a time-dependent, three-dimensional, nonlinear, resistive magnetohydrodynamic code indicate that in the formation phase an nϕ=1 instability (nϕ is the toroidal Fourier mode) is excited by the current-carrying column injected from the gun region. The growth of the nϕ=1 column mode terminates in a violent event in which there is significant magnetic reconnection and a topology change. The combined action of the nϕ=1 kink instability and the reconnection event amplifies the poloidal flux. By means of experimental diagnostics, detailed diagnostics and visualizations in the simulations, and a phenomenological model of the linear perturbations, we investigate the roles of the nϕ=1 column mode and reconnection in forming the spheromak.
Fundamental and harmonic submillimeter-wave emission from parallel Josephson junction arrays
Authors: Boussaha Faouzi , Salez Morvan , Féret Alexandre , Lecomte Benoit , Chaumont Christine , Chaubet Michel , Dauplay Frédéric , Delorme Yan , Krieg Jean-Michel
Published: April 2009

We report heterodyne measurements of Josephson microwave radiation emitted by a parallel array of small superconductor-insulator-superconductor (SIS) junctions at submillimeter-wave frequencies. The array consists of five Nb/Al–AlOx/Nb junctions nonevenly distributed in a niobium superconducting stripline, and is optimized for rf coupling in the 450–640 GHz range. We observed Fiske-like resonant steps in its I-V curve in the presence of magnetic field. The device was placed in a waveguide mount, and its radiation was quasioptically coupled out of the cryostat, to a SIS-mixer spectrometer in the same frequency range, with a 4–8 GHz band for spectral analysis. We detected a coherent signal in the spectra when the array was biased on the first and third steps, respectively, at the first harmonic frequency of 242 GHz and at the fundamental frequency of 493 GHz, both being the Josephson frequencies associated with their dc voltages. This strongly suggests that this type of parallel arrays optimized for wideband rf coupling, though strongly discretized, hosts dynamic fluxon regimes similar to long Josephson junctions, which could find applications in superconducting digital electronics or integrated heterodyne submillimeter-wave receivers.
On-chip fabrication of an individual α-Fe2O3 nanobridge and application of ultrawide wavelength visible-infrared photodetector/optical switching
Authors: Hsu Li-Chieh , Kuo Yu-Pi , Li Yuan-Yao
Published: April 2009

A single crystalline α-Fe2O3 nanobridge (NB) was laterally grown between two electrodes by one-step thermal oxidation of 100 nm Fe film at 350 °C in air atmosphere to form a NB photodetector. The diameter of the as-grown NB was 8 nm, while the length of the NB was about 240 nm. The photosensitivity of an individual α-Fe2O3 NB photodetector was larger than 80% with the illumination of the visible-infrared light (wavelength: 400–800 nm). The rapid photoresponse time (<20 ms), high on/off ratio (>12), and high gain (G=2.9×107) of an individual α-Fe2O3 NB photodetector can be attributed to the small diameter and high surface-to-volume of the NB.
Ballistic effects up to room temperature in microscopic Hall sensors
Authors: Jouault B. , Desrat W. , Couturaud O. , Contreras S. , Mailly D. , Mosser V. , Zawadzki W.
Published: April 2009

The Hall resistance of small Hall sensors and its nonlinear dependence on magnetic field B were investigated at the temperature of 4.2 K. The sensors were four-terminal crosses fabricated by etching AlGaAs/InGaAs/GaAs δ-doped heterostructures. While large sensors exhibit good linearity of the Hall voltage on magnetic field, in sensors smaller than 5 μm we detected pronounced nonlinearities for magnetic fields between 0 and 2 T. We attribute the latter to ballistic corrections to the classical Hall effect, and we model the Hall and the bend resistances at low temperature using Monte Carlo simulation. We also carried out temperature studies of the Hall sensors. We show that the nonlinearities persist up to room temperature. The effect of nonlinearities on the performance of Hall sensors is discussed.
Microstructural evolution of nonpolar (11-20) GaN grown on (1-102) sapphire using a 3D-2D method
Authors: Johnston C. F. , Kappers M. J. , Humphreys C. J.
Published: April 2009

The microstructure of nonpolar, a-plane (11-20) GaN grown on r-plane (1-102) sapphire, using a three dimensional (3D)-two dimensional (2D) growth transition, has been studied at different stages of metal organic vapor phase epitaxy. The microstructure and morphology of GaN islands formed at the initial stages of growth, as well as the fully coalesced film, were characterized using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The growth of GaN islands (bounded by {10-11} and (000-1) facets) was established under reactor conditions of relatively high pressure and high V/III ratio, whereas the island coalescence was achieved at lower pressure and low V/III ratio, leading to pit-free films with shallow striations along ⟨0001⟩. Cross-sectional TEM studies, in combination with the AFM studies of the uncoalesced films, showed that there was a correlation between the point at which partial dislocation line direction changed and the point at which growth conditions changed from the 3D to 2D mode. Lengthening the 3D growth stage obviously increased the size of the GaN islands and was also found to increase the basal plane stacking fault (BSF) length and decrease the density of partial dislocations in the coalesced films: It is suggested that BSFs in adjacent islands merge when islands are sufficiently large to impinge before the 2D growth step. Their merging necessitates the annihilation of some of the partial dislocations, and this causes the decrease in dislocation density.
Electronic structure of amorphous silicon oxynitride with different compositions
Authors: Sorokin A. N. , Karpushin A. A. , Gritsenko V. A. , Wong H.
Published: April 2009

A revised tight-binding Hamiltonian parametrization scheme for calculating the electronic structure of both covalent and ion-covalent solids is proposed. Unlike the conventional approaches, the present nonempirical calculation does not rely on any empirical parameter. We use the atomic properties of isolated atoms to construct the matrix elements. Results show that the predicted charge transfer in SiO2 and Si3N4, the bandgap energies of SiO2, Si3N4, and SiOxNy films, as well as the electron and hole barriers at the Si/SiO2, Si/Si3N4, and Si/SiOxNy interfaces are in good agreement with the experimental findings reported in literatures.
Model ab initio study of charge carrier solvation and large polaron formation on conjugated carbon chains
Authors: Mayo M. L. , Gartstein Yu. N.
Published: April 2009

Using long CNH2 conjugated carbon chains with the polyynic structure as prototypical examples of one-dimensional (1D) semiconductors, we discuss self-localization of excess charge carriers into 1D large polarons in the presence of the interaction with a surrounding polar solvent. The solvation mechanism of self-trapping is different from the polaron formation due to coupling with bond-length modulations of the underlying atomic lattice well known in conjugated polymers. Model ab initio computations employing the hybrid B3LYP density functional, in conjunction with the polarizable continuum model, are carried out demonstrating the formation of both electron and hole polarons. Polarons can emerge entirely due to solvation but even larger degrees of charge localization occur when accompanied by atomic displacements.
Compressible magnetic Rayleigh–Taylor instability in stratified plasmas: Comparison of analytical and numerical results in the linear regime
Authors: Liberatore S. , Jaouen S. , Tabakhoff E. , Canaud B.
Published: April 2009

Magnetic Rayleigh–Taylor instability is addressed in compressible hydrostatic media. A full model is presented and compared to numerical results from a linear perturbation code. A perfect agreement between both approaches is obtained in a wide range of parameters. Compressibility effects are examined and substantial deviations from classical Chandrasekhar growth rates are obtained and confirmed by the model and the numerical calculations.
A subwavelength near-infrared negative index material
Authors: Zhang Xuhuai , Davanço Marcelo , Urzhumov Yaroslav , Shvets Gennady , Forrest Stephen R.
Published: April 2009

A single layer of a subwavelength negative index material (NIM) operating at a wavelength of 1 μm is demonstrated. The geometrical parameters of the nanostructure are determined by characterizing its optical transmission spectrum. We show through photonic band calculations that these parameters give rise to a negative index in a corresponding bulk NIM. The fabrication inaccuracies in the dielectric spacer thickness that are likely to be introduced in a prism composed of multiple layers of this structure are shown through full-wave simulations to be within a range that preserves its negative refractive behavior.
Amorphous In–Ga–Zn–O coplanar homojunction thin-film transistor
Authors: Sato Ayumu , Abe Katsumi , Hayashi Ryo , Kumomi Hideya , Nomura Kenji , Kamiya Toshio , Hirano Masahiro , Hosono Hideo
Published: April 2009

A fabrication process of coplanar homojunction thin-film transistors (TFTs) is proposed for amorphous In–Ga–Zn–O (a-IGZO), which employs highly doped contact regions naturally formed by deposition of upper protection layers made of hydrogenated silicon nitride (SiNX:H). The direct deposition of SiNX:H reduced the resistivity of the semiconductive a-IGZO layer down to 6.2×10−3 Ω cm and formed a nearly ideal Ohmic contact with a low parasitic source-to-drain resistance of 34 Ω cm. Simple evaluation of field-effect mobilities (μsat) overestimated their values especially for short-channel TFTs, while the channel resistance method proved that μsat was almost constant at 9.5 cm2 V−1 s−1.
Influence of bias electric field on magnetoelectric interactions in ferromagnetic-piezoelectric layered structures
Authors: Fetisov Y. K. , Fetisov L. Y. , Srinivasan G.
Published: April 2009

The nature of magnetoelectric (ME) interactions has been investigated under a dc electric field E in Ni-lead zirconante titanate bilayer for bending and acoustic modes. Both the ME voltage and the resonance frequencies are sensitively dependent on E and are attributed to variations in the permittivity and piezoelectric coefficient. A 40% increase in the ME voltage and 12% increase in the resonance frequency in comparison to zero bias were observed for bending modes. A similar behavior was observed for ME coupling at acoustic modes. The results are of interest for enhancing the sensitivity of magnetic field sensors based on ME composites.
Litter burning does not equally affect seedling emergence of native and alien species of the Mediterranean-type Chilean matorral
Authors: Gómez-González Susana , Cavieres Lohengrin A.
Published: April 2009

Central Chile differs from other areas with Mediterranean-type climate by the scarcity of natural wildfires. The Chilean matorral is highly invaded by alien plant species from other Mediterranean zones of the world, where natural, recurrent wildfires have been one of their ecological features at least since the Pliocene. This suggests that anthropogenic fires in Chile might favour alien plant recruitment, increasing the invasive process. We assessed the effect of litter burning on the emergence of alien and native species from the soil seedbank of a matorral of central Chile. Soil samples were taken from three types of microhabitats: (i) closed matorral; (ii) beneath the canopy of shrubs and trees from an open matorral; (iii) grassland. Each sample was split in two subsamples. One subsample was exposed to fire by burning the litter taken from its corresponding microhabitat, and the other subsample was left unburned and used as a control. Fire intensity, determined by the fuel type, affected more markedly the native seedbank survival than the alien one. The low-intensity fire produced by grassland litter did not significantly affect the emergence of native herbs but increased alien species richness. The high-intensity and the very high-intensity fires produced by litter burning from beneath the canopy of the closed and the open matorral, respectively, negatively affected the seedling emergence of both native and alien species, but did so in a more pronounced manner to native species. Therefore, anthropogenic fires in central Chile may promote the invasion of alien plants with favourable traits (i.e. heat-shock resistance of seeds) that are not present in the native flora.
Structural rearrangement of CaMKIIα catalytic domains encodes activation
Authors: Thaler Christopher , Koushik Srinagesh V. , Puhl Henry L. , Blank Paul S. , Vogel Steven S.
Published: April 2009

At its fundamental level, human memory is thought to occur at individual synaptic contact sites and manifest as persistent changes in synaptic efficacy. In digital electronics, the fundamental structure for implementing memory is the flip-flop switch, a circuit that can be triggered to flip between two stable states. Recently, crystals of Ca
2+
/calmodulin-dependent protein kinase IIα (CaMKIIα) catalytic domains, the enzymatic portion of a dodecameric holoenzyme involved in memory, were found to form dimers [Rosenberg OS, Deindl S, Sung RJ, Nairn AC, Kuriyan J (2005) Structure of the autoinhibited kinase domain of CaMKII and SAXS analysis of the holoenzyme.
Cell
123:849–860]. Although the formation of dimers in the intact holoenzyme has not been established, several features of the crystal structure suggest that dimers could act as a synaptic switch. ATP-binding sites were occluded, and the T286 autophosphorylation site responsible for persistent kinase activation was buried. These features would act to stabilize an autoinhibited “paired”-enzyme state. Ca
2+
-calmodulin binding was postulated to trigger the formation of an active state with unpaired catalytic domains. This conformation would allow ATP access and expose T286, autophosphorylation of which would act to maintain the “unpaired” conformation. We used fluorescence anisotropy and FRET imaging of Venus-tagged CaMKIIα to test the hypothesis that neuronal CaMKIIα can flip between two stable conformations in living cells. Our data support the existence of catalytic domain pairs, and glutamate receptor activation in neurons triggered an increase in anisotropy consistent with a structural transition from a paired to unpaired conformation.
Qualitative aspects of developmental language impairment relate to language and literacy outcome in adulthood
Authors: Whitehouse Andrew J. O. , Line E. A. , Watt Helen J. , Bishop Dorothy V. M.
Published: April 2009

Background: Developmental language disorder is a heterogeneous diagnostic category. Little research has compared the long‐term outcomes of children with different subtypes of language impairment.

Aims: To determine whether the pattern of language impairment in childhood related to language and literacy outcomes in adulthood.

Methods & Procedures: Adults who took part in previous studies as children were traced. There were four groups of participants, each with a different childhood diagnosis: specific language impairment (SLI; n = 19, mean age at follow‐up = 24;8), pragmatic language impairment (PLI; n = 7, mean age at follow‐up = 22;3), autism spectrum disorder (ASD; n = 11; mean age at follow‐up = 21;9), and no childhood diagnosis (typical; n = 12; mean age at follow‐up = 21;6). Participants were administered a battery of language and literacy tests.

Outcomes & Results: Adults with a history of SLI had persisting language impairment as well as considerable literacy difficulties. Pragmatic deficits also appeared to develop over time in these individuals. The PLI group had enduring difficulties with language use, but presented with relatively intact language and literacy skills. Although there were some similarities in the language profile of the PLI and ASD groups, the ASD group was found to have more severe pragmatic deficits and parent‐reported linguistic difficulties in conversational speech.

Conclusions & Implications: The pattern of deficits observed in different subtypes of developmental language disorder persists into adulthood. The findings highlight the importance of a wide‐ranging clinical assessment in childhood, which may provide an indication of outcome in adulthood.
Connexin43 Potentiates Osteoblast Responsiveness to Fibroblast Growth Factor 2 via a Protein Kinase C-Delta/Runx2–dependent Mechanism
Authors: Lima Florence , Niger Corinne , Hebert Carla , Stains Joseph P.
Published: April 2009

In this study, we examine the role of the gap junction protein, connexin43 (Cx43), in the transcriptional response of osteocalcin to fibroblast growth factor 2 (FGF2) in MC3T3 osteoblasts. By luciferase reporter assays, we identify that the osteocalcin transcriptional response to FGF2 is markedly increased by overexpression of Cx43, an effect that is mediated by Runx2 via its OSE2 cognate element, but not by a previously identified connexin-responsive Sp1/Sp3-binding element. Furthermore, disruption of Cx43 function with Cx43 siRNAs or overexpression of connexin45 markedly attenuates the response to FGF2. Inhibition of protein kinase C delta (PKCδ) with rottlerin or siRNA-mediated knockdown abrogates the osteocalcin response to FGF2. Additionally, we show that upon treatment with FGF2, PKCδ translocates to the nucleus, PKCδ and Runx2 are phosphorylated and these events are enhanced by Cx43 overexpression, suggesting that the degree of activation is enhanced by increased Cx43 levels. Indeed, chromatin immunoprecipitations of the osteocalcin proximal promoter with antibodies against Runx2 demonstrate that the recruitment of Runx2 to the osteocalcin promoter in response to FGF2 treatment is dramatically enhanced by Cx43 overexpression. Thus, Cx43 plays a critical role in regulating the ability of osteoblasts to respond to FGF2 by impacting PKCδ and Runx2 function.
Cdc14 Inhibition by the Spindle Assembly Checkpoint Prevents Unscheduled Centrosome Separation in Budding Yeast
Authors: Chiroli Elena , Rancati Giulia , Catusi Ilaria , Lucchini Giovanna , Piatti Simonetta
Published: April 2009

The spindle assembly checkpoint (SAC) is an evolutionarily conserved surveillance mechanism that delays anaphase onset and mitotic exit in response to the lack of kinetochore attachment. The target of the SAC is the E3 ubiquitin ligase anaphase-promoting complex (APC) bound to its Cdc20 activator. The Cdc20/APC complex is in turn required for sister chromatid separation and mitotic exit through ubiquitin-mediated proteolysis of securin, thus relieving inhibition of separase that unties sister chromatids. Separase is also involved in the Cdc-fourteen early anaphase release (FEAR) pathway of nucleolar release and activation of the Cdc14 phosphatase, which regulates several microtubule-linked processes at the metaphase/anaphase transition and also drives mitotic exit. Here, we report that the SAC prevents separation of microtubule-organizing centers (spindle pole bodies [SPBs]) when spindle assembly is defective. Under these circumstances, failure of SAC activation causes unscheduled SPB separation, which requires Cdc20/APC, the FEAR pathway, cytoplasmic dynein, and the actin cytoskeleton. We propose that, besides inhibiting sister chromatid separation, the SAC preserves the accurate transmission of chromosomes also by preventing SPBs to migrate far apart until the conditions to assemble a bipolar spindle are satisfied.
Reactive Oxygen Species Regulate a Slingshot-Cofilin Activation Pathway
Authors: Kim Jun-Sub , Huang Timothy Y. , Bokoch Gary M.
Published: April 2009

Cellular stimuli generate reactive oxygen species (ROS) via the local action of NADPH oxidases (Nox) to modulate cytoskeletal organization and cell migration through unknown mechanisms. Cofilin is a major regulator of cellular actin dynamics whose activity is controlled by phosphorylation/dephosphorylation at Ser3. Here we show that Slingshot-1L (SSH-1L), a selective cofilin regulatory phosphatase, is involved in H2O2-induced cofilin dephosphorylation and activation. SSH-1L is activated by its release from a regulatory complex with 14-3-3ζ protein through the redox-mediated oxidation of 14-3-3ζ by H2O2. The ROS-dependent activation of the SSH-1L-cofilin pathway stimulates the SSH-1L–dependent formation of cofilin-actin rods in cofilin-GFP–expressing HeLa cells. Similarly, the formation of endogenous ROS stimulated by angiotensin II (AngII) also activates the SSH-1L-cofilin pathway via oxidation of 14-3-3ζ to increase AngII-induced membrane ruffling and cell motility. These results suggest that the formation of ROS by NADPH oxidases engages a SSH-1L-cofilin pathway to regulate cytoskeletal organization and cell migration.
Prescriptions of Chinese Herbal Medicines for Insomnia in Taiwan during 2002
Authors: Chen Fang-Pey , Jong Maw-Shiou , Chen Yu-Chun , Kung Yen-Ying , Chen Tzeng-Ji , Chen Fun-Jou , Hwang Shinn-Jang
Published: April 2009

Chinese herbal medicine (CHM) has been commonly used for treating insomnia in Asian countries for centuries. The aim of this study was to conduct a large‐scale pharmaco‐epidemiologic study and evaluate the frequency and patterns of CHM use in treating insomnia. We obtained the traditional Chinese medicine (TCM) outpatient claims from the National Health Insurance in Taiwan for the year 2002. Patients with insomnia were identified from the diagnostic code of International Classification of Disease among claimed visiting files. Corresponding prescription files were analyzed, and an association rule was applied to evaluate the co‐prescription of CHM. Results showed that there were 16 134 subjects who visited TCM clinics for insomnia in Taiwan during 2002 and received a total of 29 801 CHM prescriptions. Subjects between 40 and 49 years of age comprised the largest number of those treated (25.3%). In addition, female subjects used CHMs for insomnia more frequently than male subjects (female : male = 1.94 : 1). There was an average of 4.8 items prescribed in the form of either an individual Chinese herb or formula in a single CHM prescription for insomnia. Shou‐wu‐teng (Polygonum multiflorum) was the most commonly prescribed single Chinese herb, while Suan‐zao‐ren‐tang was the most commonly prescribed Chinese herbal formula. According to the association rule, the most commonly prescribed CHM drug combination was Suan‐zao‐ren‐tang plus Long‐dan‐xie‐gan‐tang, while the most commonly prescribed triple drug combination was Suan‐zao‐ren‐tang, Albizia julibrissin, and P. multiflorum. Nevertheless, further clinical trials are needed to evaluate the efficacy and safety of these CHMs for treating insomnia.