bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant Impacts on Competition Between Tidal Marsh Microbes
Authors: Sutton-Grier Ariana , Bullock Allyson , Keller Jason , Gilmour Cindy , Megonigal Pat
Published: August 2009

Background/Question/Methods

Wetlands can store a lot of carbon in soils, but wetland microbial respiration also releases a great deal of carbon dioxide (CO~2~) and methane (CH~4~). These gases combined are responsible for ~80% of the radiative climate forcing. Understanding the controls on microbial respiration and the importance of different metabolic pathways has important climate change implications. Plants affect microbial respiration in wetlands by impacting the available soil carbon pool and the redoximorphic conditions of the soil environment. These plant impacts in turn affect microbial competition. In this study we were particularly interested in determining the role of soil carbon quality versus environmental factors in influencing the relative contributions of denitrification, iron reduction, sulfate reduction, and methanogenesis to overall microbial respiration in a freshwater tidal wetland (Jug Bay) and a brackish marsh (Jack Bay) on the Chesapeake Bay, USA. We collected soils from each site, homogenized them, and buried samples at their original location or at the opposite location. A year and a half later samples were collected (October, 2008) and analyzed for the amount of respiration contributed by different metabolic pathways.

Results/Conclusions

Overall microbial respiration rates were higher in the soil with the higher carbon content (Jack Bay average soil organic matter = 54%; Jug Bay = 18%). However, when normalized to soil carbon content, respiration rates were actually higher for the soil with lower carbon content at both locations (Jack Bay soils total carbon respired = 4.4 umols per g soil C per day; Jug Bay soils = 7.4 umols per g soil C per day). These results suggest that carbon quality, more than quantity or environmental factors such as sulfate availability, drives microbial respiration rates. We conclude that plant carbon inputs to soils have a lasting legacy on microbial competition in wetlands.
Integration of microbial communities into large-scale ecosystem models
Authors: Allison Steven
Published: August 2009

Background/Question/Methods

Micro-organisms, including Bacteria, Archaea, and Fungi, control major processes throughout the Earth system. Recent advances in microbial ecology and microbiology have revealed an astounding level of genetic and metabolic diversity in microbial communities. However, a framework for interpreting the meaning of this diversity has lagged behind the initial discoveries. Microbial communities have yet to be included explicitly in any major biogeochemical models in terrestrial ecosystems, and have only recently broken into ocean models. Although simplification of microbial communities is essential in complex systems, omission of community parameters may seriously compromise model predictions of biogeochemical processes. Two key questions arise from this tradeoff: 1) When and where must microbial community parameters be included in biogeochemical models? 2) If microbial communities are important, how should they be simplified, aggregated, and parameterized in models? To address these questions, a literature survey was conducted to determine if microbial communities are sensitive to four environmental disturbances that are associated with global change.

*Results/Conclusions*

For all environmental perturbations, community composition changed significantly following disturbance. However, the implications for ecosystem function were unclear in most of the published studies. Therefore, I developed a simple model framework to illustrate the situations in which microbial community changes would affect rates of biogeochemical processes. These scenarios could be quite common, but powerful predictive models cannot be developed without much more information on the functions and disturbance responses of microbial taxa. Small-scale models that explicitly incorporate microbial communities also suggest that process rates strongly depend on microbial interactions and disturbance responses. The challenge is to scale up these models to make predictions at the ecosystem and global scales based on measurable parameters. Meeting this challenge will require a coordinated effort to develop a series of nested models at scales ranging from the micron to the globe in order to optimize the tradeoff between model realism and feasibility.
The NADPH oxidase Nox4 restricts the replicative lifespan of human endothelial cells
Authors: Lener Barbara , Kozieł Rafał , Pircher Haymo , Hütter Eveline , Greussing Ruth , Herndler-Brandstetter Dietmar , Hermann Martin , Unterluggauer Hermann , Jansen-Dürr Pidder
Published: August 2009

The free radical theory of aging proposes that ROS (reactive oxygen species) are major driving forces of aging, and are also critically involved in cellular senescence. Besides the mitochondrial respiratory chain, alternative sources of ROS have been described that might contribute to cellular senescence. Noxs (NADPH oxidases) are well-known sources of superoxide, which contribute to the antimicrobial capabilities of macrophages, a process involving the prototypical member of the family referred to as Nox2. However, in recent years non-phagocytic homologues of Nox2 have been identified that are involved in processes other than the host defence. Superoxide anions produced by these enzymes are believed to play a major role in signalling by MAPKs (mitogen-activated protein kinases) and stress-activated kinases, but could also contribute to cellular senescence, which is known to involve oxygen radicals. In HUVECs (human umbilical vein endothelial cells), Nox4 is predominantly expressed, but its role in replicative senescence of HUVECs remains to be elucidated. Using shRNA (small-hairpin RNA)-mediated knockdown of Nox4, implicating lentiviral vectors, we addressed the question of whether lifelong depletion of Nox4 in HUVECs would influence the senescent phenotype. We found a significant extension of the replicative lifespan of HUVECs upon knockdown of Nox4. Surprisingly, mean telomere length was significantly reduced in Nox4-depleted cells. Nox4 depletion had no discernable influence on the activity of MAPKs and stress-activated kinases, but reduced the degree of oxidative DNA damage. These results suggest that Nox4 activity increases oxidative damage in HUVECs, leading to loss of replicative potential, which is at least partly independent of telomere attrition.
In silico analysis of neuregulin 1 evolution in vertebrates
Authors: Chou Chih-Fong , Ozaki Miwako
Published: August 2009

NRG1 (neuregulin 1) belongs to the NRG family of EGF (epidermal growth factor)-like signalling molecules involved in cell–cell communication during development and disease. It plays important roles in the developing tissues of the nerves, heart and mammary glands. Particularly in neurobiology, NRG1 signalling is associated with synaptic transmission, myelination of Schwann cells and the human disease of schizophrenia. Many different isoforms of NRG1 make the molecule highly sophisticated in biological activities and a great diversity of in vivo functions. The nervous system is a common trait in all bilateria (higher animals), but based on the BLAST information from the currently available databases it appears that NRG1 orthologues can only be identified in vertebrates. The gene was analysed in silico for type I–IV CDSs (coding sequences) from ten vertebrate genomes. The gene loci, structures of coding-intronic sequences, ClustalW program analyses, phylogenetic trees and conserved motifs in ecto- and cyto-plasmic domains were analysed and compared. Here, we conclude that non-mammalian vertebrates mainly carry type I (may have evolved a spacer different from mammalian isoforms), II and III NRG1s. The type IV NRG1 N-terminal CDSs can be identified from most of the mammalian genomes studied; however, the corresponding rodent sequences lack the start codon. The evolutionary conservation of a CDS59-CDS24-CDS103 domain, intracellular phosphorylation sites and bipartite nuclear localization signals is of physiological significance.
Charge transfer at polymer-electrode interfaces: The effect of energetic disorder and thermal injection on band bending and open-circuit voltage
Authors: Blakesley James C. , Greenham Neil C.
Published: August 2009

We investigate the band bending that occurs at the interface between a disordered organic semiconductor and a metal electrode. Ultraviolet photoemission spectroscopy measurements of thin organic layers on conducting substrates have revealed band bending within a few nanometers of the interface. It has been proposed that this is caused by the transfer of carriers from the substrate into empty states in the organic film. Here we numerically model this process by simulating a film with a given density of states in thermal equilibrium with a metallic substrate. Comparing the model with various published experiments, we demonstrate that the observed band bending can be explained equally well by either energetic relaxation of charge carriers on a timescale longer than photoemission (polaronic relaxation) or by a Gaussian density of states representing energetic disorder. In the former case, our results suggest that the thermal injection of carriers to higher-energy states has led observers to overestimate the relaxation energy by as much as several hundred meV. We also show that band-bending effects due to disorder are expected to significantly reduce the open-circuit voltage in organic photovoltaic devices, and we quantify the relationship between the amount of voltage loss and the degree of disorder.
Influence of N interstitials on the electronic properties of GaAsN alloys
Authors: Jin Y. , Jock R. M. , Cheng H. , He Y. , Mintarov A. M. , Wang Y. , Kurdak C. , Merz J. L. , Goldman R. S.
Published: August 2009

We have used rapid thermal annealing to investigate the influence of N interstitials on the electronic properties of GaAsN alloys. Nuclear reaction analysis reveals an annealing-induced decrease in the interstitial N concentration, while the total N composition remains constant. Corresponding signatures for the reduced interstitial N concentration are apparent in Raman spectra. Following annealing, both the room-T carrier concentration, n, and the mobility increase. At higher measurement-Ts, a thermally activated increase in n suggests the presence of a trap near GaAsN conduction band edge with activation energy 85±15 meV. The annealing-induced increase in n suggests the association of the trap with interstitial N.
Titanium nanotubes grown by titanium anodization
Authors: Alivov Yahya , Fan Z. Y. , Johnstone D.
Published: August 2009

In this work we investigated the structural and electrical properties of titanium dioxide (TiO2) nanotubes (NTs) grown by electrochemical anodization of Ti metal sheets in NH4F+H2O+glycerol electrolyte at different anodization voltages (Va) and electrolyte composition. Our results revealed that TiO2 NTs can be grown in a wide range of anodization voltages from 10 to 240 V. The maximum NH4F acid concentration, at which NTs can be formed, decreases with the anodization voltage, which is 0.7% for Va<60 V, and decreases to 0.1% at Va=240 V. Addition of water to the electrolyte results in an increase in NT growth rate and modification of NT film morphology. Glancing angle x-ray diffraction experiments show that as-grown amorphous TiO2 transforms to anatase phase after annealing at 400 °C and further transforms to rutile phase at annealing temperatures above 500 °C. Samples grown in 30–120 V voltage range have higher crystal quality as seen from anatase (101) peak intensity and reduced linewidth. The electrical resistivity of the NTs varies with Va concentration and increases by eight orders of magnitude when Va increases from 10 to 240 V. The resistivity is also greatly dependent on H2O concentration increasing with its concentration up to nine orders of magnitude. Temperature dependent I-V and photoinduced current transient spectroscopy were employed to analyze electrical properties and defect structure on NT samples.
Integration of planar and bulk heterojunctions in polymer/nanocrystal hybrid photovoltaic cells
Authors: Tan Zhanao , Zhu Ting , Thein Myo , Gao Shuai , Cheng An , Zhang Fan , Zhang Chunfeng , Su Huaipeng , Wang Jingkang , Henderson Ron , Hahm Jong-in , Yang Yongping , Xu Jian
Published: August 2009

We present in this communication a hybrid polymer/nanocrystal photovoltaic device architecture wherein a net poly(3-hexylthiophene) (P3HT) light-absorbing film is inserted underneath the blended layer of P3HT and PbSe nanocrystal quantum dots in the active region. Such a design features the vertical integration of planar and bulk heterojunctions, which allows for the employment of a thinner bulk heterojunction for more efficient carrier collection without an excessive reduction of the overall light absorption by the photovoltaic cell. The measured device performance represents a significant improvement over previously reported hybrid cells containing bulk heterojunctions of P3HT and Pb(S,Se) nanocrystal quantum dots.
Quantum-state selection, alignment, and orientation of large molecules using static electric and laser fields
Authors: Filsinger Frank , Küpper Jochen , Meijer Gerard , Holmegaard Lotte , Nielsen Jens H. , Nevo Iftach , Hansen Jonas L. , Stapelfeldt Henrik
Published: August 2009

Supersonic beams of polar molecules are deflected using inhomogeneous electric fields. The quantum-state selectivity of the deflection is used to spatially separate molecules according to their quantum state. A detailed analysis of the deflection and the obtained quantum-state selection is presented. The rotational temperatures of the molecular beams are determined from the spatial beam profiles and are all approximately 1 K. Unprecedented degrees of laser-induced alignment (⟨cos2 θ2D⟩=0.972) and orientation of iodobenzene molecules are demonstrated when the state-selected samples are used. Such state-selected and oriented molecules provide unique possibilities for many novel experiments in chemistry and physics.
Negative magnetoresistance in boron-doped nanocrystalline diamond films
Authors: Willems B. L. , Zhang G. , Vanacken J. , Moshchalkov V. V. , Janssens S. D. , Williams O. A. , Haenen K. , Wagner P.
Published: August 2009

We report on the observation of a negative magnetoresistance (NMR) regime in boron-doped nanocrystalline diamond films at low temperatures. A comparative analysis of our experimental results and those reported for systems composed of superconducting granules embedded in an insulating matrix (also referred as granular films) suggest the presence of superconducting regions inside the insulating films as causing the NMR. By considering the latter scenario, the experimental observations are explained by modeling the systems as consisting of a distribution of superconducting granules whose global properties are tuned by the intergrain distance.
Wavelet-based coherent vorticity sheet and current sheet extraction from three-dimensional homogeneous magnetohydrodynamic turbulence
Authors: Yoshimatsu Katsunori , Kondo Yuji , Schneider Kai , Okamoto Naoya , Hagiwara Hiroyuki , Farge Marie
Published: August 2009

A method for extracting coherent vorticity sheets and current sheets out of three-dimensional homogeneous magnetohydrodynamic (MHD) turbulence is proposed, which is based on the orthogonal wavelet decomposition of the vorticity and current density fields. Thresholding the wavelet coefficients allows both fields to be split into coherent and incoherent parts. The fields to be analyzed are obtained by direct numerical simulation (DNS) of forced incompressible MHD turbulence without mean magnetic field, using a classical Fourier spectral method at a resolution of 5123. Coherent vorticity sheets and current sheets are extracted from the DNS data at a given time instant. It is found that the coherent vorticity and current density preserve both the vorticity sheets and the current sheets present in the total fields while retaining only a few percent of the degrees of freedom. The incoherent vorticity and current density are shown to be structureless and of mainly dissipative nature. The spectral distributions of kinetic and magnetic energies of the coherent fields only differ in the dissipative range, while the corresponding incoherent fields exhibit near-equipartition of energy. The probability distribution functions of total and coherent fields for both vorticity and current density coincide almost perfectly, while the incoherent fields have strongly reduced variances. Studying the energy flux confirms that the nonlinear dynamics is fully captured by the coherent fields only.
Analysis of mass deposit in nickel pulse electrodeposition using an electric circuit model equivalent to electrocrystallization and electric double layer
Authors: Saitou M.
Published: August 2009

We have investigated a deposited mass ratio represented by the ratio between the actual deposited mass and the deposited mass expected from Faraday’s law in nickel pulse electrodeposition. The deposited mass ratio decays exponentially with the pulse current frequency and approaches asymptotically to a constant value at a high frequency. An analytical solution for an electric circuit model equivalent to electrocrystallization and electric double layer well describes a change in the deposited mass ratio affected by the pulse current frequency, temperature, and additive compound. This study shows that the effect of temperature and the additive on the deposited mass ratio is characterized by a cut-off frequency defined by the analytical solution.
Interaction between hydrogen molecules and metallofullerenes
Authors: Yoon Mina , Yang Shenyuan , Zhang Zhenyu
Published: August 2009

Within first-principles density functional theory, we explore the feasibility of using metallofullerenes as efficient hydrogen storage media. In particular, we systematically investigate the interaction between hydrogen molecules and La encapsulated all-carbon fullerenes, Cn (20≤n≤82), focusing on the role of transferred charges between the metal atoms and fullerenes on the affinity of hydrogen molecules to the metallofullerenes. Our calculations show that three electrons are transferred from La atom to fullerene cages, while the induced charges are mostly screened by the fullerene cages. We find the local enhancement of molecular hydrogen affinity to the fullerenes to be sensitively dependent on the local bonding properties, rather than on the global charging effects.
qPlus atomic force microscopy of the Si(100) surface: Buckled, split-off, and added dimers
Authors: Sweetman A. , Gangopadhyay S. , Danza R. , Berdunov N. , Moriarty P.
Published: August 2009

Dimer configurations at the Si(100) surface have been studied with noncontact atomic force microscopy in the qPlus mode at 77 K, using both large (10 nm peak to peak) and small (0.5 nm peak to peak) oscillation amplitudes. In addition to the p(2×1), p(2×2), and c(4×2) reconstructions of the pristine surface, a variety of defect types including ad-dimers, vacancies, and split-off dimers have been imaged. Our data appear at odds with the currently accepted structural model for split-off dimers. At low oscillation amplitudes the degree of apparent dimer buckling can be “tuned” by varying the frequency shift set point.
Electrical detection of microwave assisted magnetization switching in a Permalloy microstrip
Authors: Fan Xiaolong , Gui Y. S. , Wirthmann A. , Williams G. , Xue Desheng , Hu C.-M.
Published: August 2009

Microwave assisted magnetization switching has been investigated in a nonelliptic Permalloy microstrip, using radio frequency magnetic fields h applied in-plane perpendicular to the long axis of the strip. In low power excitations, Hs decreases almost linearly with increasing h; this can be qualitatively understood by introducing an susceptibility χyy that links the dynamic magnetization inside the microstip to the h field outside the microstip. However, at high frequencies, Hs no longer decrease with increasing h when this latter field exceeds a critical value. We suppose such “saturation” effects could attribute to the nonlinear ferromagnetic resonance caused by high power excitations.
Understanding protein folding cooperativity based on topological consideration
Authors: Wu L. , Li W. F. , Liu F. , Zhang J. , Wang J. , Wang W.
Published: August 2009

The folding cooperativity is an important issue of protein folding dynamics. Since the native topology plays a significant role in determining the folding behavior of proteins, we believe that it also has close relationship with the folding cooperativity. In the present work, we perform simulations on proteins Naf-BBL, QNND-BBL, CI2, and SH3 with the Gō model and compare their different folding behaviors. By analyzing the weak cooperative folding of protein Naf-BBL in detail, we found that the folding of Naf-BBL shows relatively weak thermodynamic coupling between residues, and such weak coupling is found mainly between the nonlocal native contacts. This finding complements our understandings on the source of barrierless folding of Naf-BBL and promotes us to analyze the topological origins of the poor thermodynamic coupling of Naf-BBL. Then, we further extend our analysis to other two-state and multistate proteins. Based on the considerations of the thermodynamic coupling and kinetic coupling, we conclude that the fraction of scattered native contacts, the difference in loop entropy of contacts, and the long range relative contact order are the major topological factors that influence the folding cooperativity. The combination of these three tertiary structural features shows significant correlations with the folding types of proteins. Moreover, we also discuss the topological factors related to downhill folding. Finally, the generic role of tertiary structure in determining the folding cooperativity is summarized.
A nanocell for quartz crystal microbalance and quartz crystal microbalance with dissipation-monitoring sensing
Authors: Ohlsson Gabriel , Langhammer Christoph , Zorić Igor , Kasemo Bengt
Published: August 2009

A novel device for nanometer-confinement of soft matter in one dimension (1D) is presented. This nanocell, with very large (up to 106:1) cell-radius to cell-height ratio, is tailored as an accessory for quartz crystal microbalance (QCM) and QCM with dissipation-monitoring (QCM-D) sensing to study internal and interfacial energy dissipation phenomena in highly confined (in 1D) soft matter and fluid films (patent pending). The cell consists of two macroscopic plates (diameter of 9 mm), a top (the “lid”) and a bottom (the QCM-D sensor), separated by appropriate spacers with heights ranging from below 100 nm up to 10 μm. The surfaces of both the lid and the bottom plate can be mechanically or/and chemically modified, prior to cell assembly, in order to tailor desired interfacial properties for the experiment. The cell is mounted on a standard QCM-D sensor, an AT-cut quartz crystal (the quartz crystal is cut at an angle of 35° from its ZX-plane), forming the bottom plate. We illustrate theoretically and experimentally, as application examples, the use of this device for studies of dynamic mass loading and internal energy dissipation processes in thin films of ethylene glycol respective thin liquid crystal films around the nematic-isotropic phase transition.
Single molecule color controllable light emitting organic field effect transistors for white light emission with high color stability
Authors: Ke Tung-Huei , Gehlhaar Robert , Chen Chih-Hsin , Lin Jiann-T , Wu Chung-Chih , Adachi Chihaya
Published: August 2009

The authors report on color controllable white light emission from a unipolar organic light emitting transistor. We demonstrate light emission with two distinct peaks: a spectrally narrow blue emission from monomers and a yellow broadband emission created close to the interface of the organic film and SiO2. Due to the functionality of Mg/Au stacked electrodes, we are able to position the recombination zone via gate voltage control. Therefore, we are able to shift the spectral peak position and change the emission intensity independently by the drain voltage. The emission color is tunable from CIE coordinates (0.27, 0.28) to (0.40, 0.41).
On the strain coupling across vertical interfaces of switchable BiFeO3–CoFe2O4 multiferroic nanostructures
Authors: Dix N. , Muralidharan R. , Guyonnet J. , Warot-Fonrose B. , Varela M. , Paruch P. , Sánchez F. , Fontcuberta J.
Published: August 2009

In magnetoelectrically coupled CoFe2O4–BiFeO3 nanostructures vertical and lateral lattice parameters of both phases are determined. We find that the in-plane lattice parameter of CoFe2O4 is fully relaxed whereas it presents compressive strain along the out-of-plane direction. Although the CoFe2O4–BiFeO3 interface is semicoherent, CoFe2O4 out-of-plane lattice strain is not relaxed after selective removal of the matrix and thus it is of nonelastic origin. In spite of the absence of elastic residual strain caused by CoFe2O4–BiFeO3 interfaces, the two phases are mechanically coupled as demonstrated by the electrical switching of the magnetization.
OH ⋅ N 2 and SH⋅N2 radical-molecule van der Waals complex
Authors: Du Shiyu , Francisco Joseph S.
Published: August 2009

OH and SH radicals are important in atmospheric chemistry because of their high reactivity. We examine the Van der Waals radical-molecule complexes formed by OH and SH radicals with molecular nitrogen. The van der Waals radical-molecule complex between OH and CO, which is isoelectronic to OH and N2, is also examined as a calibration of the computational results to literature experimental findings. In this work, we employ high level ab initio methods to investigate the stability and spectroscopic properties of these complexes. Natural bond analysis is also performed in order to study their bonding features.
The effect of SrTiO3 substrate orientation on the surface morphology and ferroelectric properties of pulsed laser deposited NaNbO3 films
Authors: Yamazoe Seiji , Sakurai Hiroyuki , Fukada Masaki , Adachi Hideaki , Wada Takahiro
Published: August 2009

Orientated NaNbO3 (NN) films were grown on SrRuO3/(001)SrTiO3 [SRO/(001)STO], SRO/(110)STO, and SRO/(111)STO substrates by pulsed laser deposition. Scanning electron microscopy images showed that the surface morphologies of the NN/SRO/(001)STO, NN/SRO/(110)STO, and NN/SRO/(111)STO took the form of a stepped structure, a striped pattern, and trigonal pyramidal-like structures, respectively. The dielectric and ferroelectric properties of the films were characterized. The NN/SRO/(110)STO film showed the lowest relative dielectric constant and the largest remanent polarization of 30.8 μC/cm2 among all films. These were interpreted as being due to the orientation direction of the NN film grown on (110)STO being parallel to the polarization direction of NN.
Generation of valley polarized current in bilayer graphene
Authors: Abergel D. S. L. , Chakraborty Tapash
Published: August 2009

We propose a device for the generation of valley polarized electronic current in bilayer graphene. By analyzing the response of this material to intense terahertz frequency light in the presence of a transverse electric field, we demonstrate that dynamical states are induced in the gapped energy region, and if the system parameters are properly tuned, these states exist only in one valley. The valley polarized states can then be used to filter an arbitrary electron current, so generating a valley polarized current.
Short-time power-law blinking statistics of single quantum dots and a test of the diffusion-controlled electron transfer model
Authors: Tang Jau , Lee Der-Hau , Yeh Yi-Cheun , Yuan Chi-Tsu
Published: August 2009

In this work we analyzed the blinking statistics data of single CdSe/ZnS quantum dots at vey short times to test some predictions of the diffusion-controlled electron transfer (DCET) model. Using autocorrelation function (ACF) approach we could extract the exponent of the inverse power-law blinking statistics down to 1 μs. Such an approach also minimizes human subjectivity in choosing a bin time and an on-off threshold. We showed that the observed stretched exponential decay in the ACF and its relationship to the blinking statistics are consistent with the DCET model, and we set an upper bound for the characteristic time constant tc.
Wall shear stress in Görtler vortex boundary layer flow
Authors: Tandiono  , Winoto S. H. , Shah D. A.
Published: August 2009

The development of wall shear stress in concave surface boundary layer flows in the presence of Görtler vortices was experimentally studied by means of hot-wire measurements. The wavelengths of the vortices were preset by thin vertical perturbation wires so to produce the most amplified wavelengths. Three different vortex wavelengths of 12, 15, and 20 mm were considered, and near-wall velocity measurements were carried out to obtain the “linear” layers of velocity profiles in the boundary layers. The wall shear stress coefficient Cf was estimated from the velocity gradient of the “linear” layer. The streamwise developments of boundary layer displacement and momentum thickness at both upwash and downwash initially follow the Blasius (laminar boundary layer) curve up to a certain streamwise location. Further downstream, they depart from the Blasius curve such that they increase at upwash and decrease at downwash before finally converge to the same value due to the increased mixing as a consequence of transition to turbulence. The spanwise-averaged wall shear stress coefficient C¯f, which initially follows the Blasius curve, increases well above the local turbulent boundary layer value further downstream due to the nonlinear effect of Görtler instability and the secondary instability modes. Three different regions are identified based on the streamwise development of C¯f, namely linear, nonlinear, and transition to turbulence regions. The onset of nonlinear region is defined as the streamwise location where the C¯f begins to depart from the Blasius curve. In the nonlinear region, the spanwise distribution of Cf at the downwash becomes narrower, and there is no inflection point found further downstream.
Ion acoustic solitary waves in magnetized pair-ion electron plasmas
Authors: Mushtaq A. , Saeed R. , Haque Q.
Published: August 2009

Properties of linear and nonlinear ion acoustic (IA) waves, propagating obliquely to an ambient magnetic field in pair-ion plasma containing a fraction of Boltzmannian electrons, are investigated. The Zakharov–Kuznetsov equation is derived for IA wave in the nonlinear regime, which admits the solitary wave solution. It is found that nonlinear profile of the IA solitary wave is significantly affected by the obliqueness, magnetic field, and the electron concentration. It is determined that the obliqueness influence both the amplitude and width of the soliton, whereas the other parameters mainly affect the width of the soliton. The results presented in this paper can be useful for future experimental investigations of pair-ion fullerene plasma.
Strong anisotropy of magnetization and sign reversion of ordinary Hall coefficient in single crystal Ge1−xMnx magnetic semiconductor films
Authors: Deng J. X. , Tian Y. F. , He S. M. , Bai H. L. , Xu T. S. , Yan S. S. , Dai Y. Y. , Chen Y. X. , Liu G. L. , Mei L. M.
Published: August 2009

Epitaxial single-crystal Ge1−xMnx ferromagnetic-semiconductor films were fabricated on Ge(001) substrates by molecular beam epitaxy. All the samples are ferromagnetic and have strong magnetic anisotropy indicated by different magnetization in plane and out of plane. The electrical transport of the films obeys Efros variable range hopping law in the low temperature range. Interestingly, a negative coefficient of the ordinary Hall effect of p-type carriers was found in the variable range hopping at low temperature. Anomalous Hall effect in Ge0.949Mn0.051 film was observed below the Curie temperature, indicating the carrier-mediated intrinsic ferromagnetism.
Probing exciton-phonon interaction in AlN epilayers by photoluminescence
Authors: Sedhain A. , Li J. , Lin J. Y. , Jiang H. X.
Published: August 2009

Deep ultraviolet (DUV) photoluminescence (PL) spectroscopy has been employed to investigate the exciton-phonon interaction in AlN. Longitudinal optical (LO) phonon replicas of free exciton recombination lines were observed in PL emission spectra, revealing the coupling of excitons with LO phonons. We have quantified such interaction by measuring Huang–Rhys factor based on polarization resolved DUV PL measurements. It was observed that the exciton-phonon coupling strength in AlN depends on the polarization configuration and is much larger in the direction with the electrical field (E⃗) of the emitted light perpendicular to the wurtzite c-axis (E⃗⊥c⃗) than in the direction of E⃗∥c⃗. Furthermore, a larger coupling constant was also measured in AlN than in GaN. The large effective hole to electron mass ratio in AlN, especially in the E⃗⊥c⃗ configuration, mainly accounts for the observed results.
Spin-dependent current modulation in organic spintronics
Authors: Wei J. H. , Liu X. J. , Xie S. J. , Yan YiJing
Published: August 2009

We investigate the spin-dependent current modulation in a model organic semiconductor sandwiched by two ferromagnetic electrodes. When the conductance band of the system is activated by an applied bias voltage, the majority-spin electrons are successively blocked within the organic semiconductor and form nonequilibrium polarons. This majority-spin blockage will modulate the minority-spin current due to the effective spin-spin coupling mediated by the electron-phonon interaction. This study suggests that the spin-blockage induced current modulation is a rather robust phenomenon in organic spintronics.
Effects of Ni cladding layers on suppression of Ag agglomeration in Ag-based Ohmic contacts on p-GaN
Authors: Son Jun Ho , Song Yang Hee , Yu Hak Ki , Lee Jong-Lam
Published: August 2009

We investigate effects of Ni cladding layers on suppression of Ag agglomeration in Ag contacts on p-GaN using high-resolution x-ray diffraction. In the annealed Ag contact, Ag (100) grains disappear and agglomerate to form a selectively epitaxial growth of Ag (111). An ultrathin Ni contact layer (10 Å) below Ag film plays a role to epitaxially grow (111) Ag films on GaN, leading to the suppression of Ag agglomeration. A 20-Å-thick Ni overlayer effectively acts as a passivation layer to prevent the surface diffusion of Ag atoms during annealing, leading to high light reflectance and low contact resistivity.
The obstetric experience of women with factor XI deficiency
Authors: CHI CLAUDIA , KULKARNI ASHWINI , LEE CHRISTINE A. , KADIR REZAN A.
Published: August 2009

Objectives. To assess the obstetric outcome in women with factor XI (FXI) deficiency. Design. Retrospective review of medical records. Setting. Tertiary referral university hospital. Population. Women with FXI deficiency. Method. Review of pregnancies over a 10‐year period (1997–2006). Main outcome measures. Pregnancy outcome, mode of delivery, changes in FXI levels during pregnancy, use of prophylaxis during labor and delivery, antepartum hemorrhage, and postpartum hemorrhage (PPH). Results. There were 61 pregnancies among 30 women with FXI deficiency (two severe, FXI level <15–20 IU/dL, and 28 partial, FXI level 20–70 IU/dL) resulting in 49 live births (two sets of twins), eight miscarriages, and six terminations of pregnancy. The modes of delivery included 38 spontaneous vaginal deliveries, three instrumental deliveries, and six cesarean sections (two emergency and four elective). No significant change in FXI levels was observed during pregnancy. Intrapartum prophylaxis with FXI concentrate or tranexamic acid was given in 19 deliveries where the mother had a positive bleeding history. Four women had excessive bleeding related to pregnancy loss and three experienced antepartum bleeding. All these women had a positive bleeding history. There were five (11%) primary and five (11%) secondary PPHs among seven women including four with a positive bleeding history. Conclusion. Women with FXI deficiency, particularly those with a positive bleeding history, are at risk of bleeding complications related to miscarriage or childbirth. The unpredictable nature of their bleeding tendency demands careful planning and close collaborations between obstetricians and hematologists.
The implementation and evaluation of a mandatory multi‐professional obstetric skills training program
Authors: SØRENSEN JETTE LED , LØKKEGAARD ELLEN , JOHANSEN MARIANNE , RINGSTED CHARLOTTE , KREINER SVEND , MCALEER SEAN
Published: August 2009

Objective. To implement and evaluate a simulation‐based training program. Design. Descriptive. Study period: June 2003–June 2006. Setting. Obstetric Department, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark. Population. Two training sessions were provided for all health professionals including doctors, midwives, auxiliary nurses, and 147 out 156 participants (94%) took part in the first training session and 192 out possible 201 (96%) took part in the second session. Methods. An intervention study of the impact of simulation‐based training in management of postpartum bleeding, shoulder dystocia, basic neonatal resuscitation, and severe preeclampsia. Main outcome measures. Before, just after and 9–15 months following the training, data were collected on the confidence and stress levels relating to the carrying out of certain procedures. In addition, a written objective test on basic neonatal resuscitation was administered. Data on any changes in work‐routines experienced by the participants were obtained by open‐ended questions. Registry data from the Danish Medical Birth Registry and from the hospital administration were included in the analysis. Results. Ninety‐two percent of all respondents had a positive attitude toward the training program. They considered management of shoulder dystocia, preeclampsia, and neonatal resuscitation less stresful and less unpleasant to perform after training. Confidence scores for all the trained skills improved significantly. A significant association was found between confidence in neonatal resuscitation and numbers of correct answers in the objective test. More than 90% found the training to have had a positive influence on their work. The need for organizational changes in the department became evident and necessary changes were implemented. Sick leave amongst midwives diminished significantly during the study period. Conclusions. A comprehensive evaluation of a mandatory simulation‐based program, implemented in a obstetric department, demonstrated a positive impact at individual and organizational levels.
Serious doubts about school effectiveness
Authors: Gorard Stephen
Published: August 2009

This paper considers the model of school effectiveness (SE) currently dominant in research, policy and practice in England (although the concerns it raises are international). It shows, principally through consideration of initial and propagated error, that SE results cannot be relied upon. By considering the residual difference between the predicted and obtained score for all pupils in any phase of education, SE calculations leave the results to be disproportionately made up of relative error terms. Adding contextual information confuses, but does not help this situation. Having shown and illustrated the sensitivity of SE to this propagation of initial errors, and therefore why it is unworkable, the paper considers some of the reasons why SE has become dominant, outlines the damage this dominant model causes and begins to shape alternative ways of considering what schools do.

Numbers are like people; torture them enough and they will tell you anything.
Three-dimensional imaging by optical sectioning in the aberration-corrected scanning transmission electron microscope
Authors: Behan G. , Cosgriff E. C. , Kirkland Angus I. , Nellist Peter D.
Published: August 2009

The depth resolution for optical sectioning in the scanning transmission electron microscope is measured using the results of optical sectioning experiments of laterally extended objects. We show that the depth resolution depends on the numerical aperture of the objective lens as expected. We also find, however, that the depth resolution depends on the lateral extent of the object that is being imaged owing to a missing cone of information in the transfer function. We find that deconvolution methods generally have limited usefulness in this case, but that three-dimensional information can still be obtained with the aid of prior information for specific samples such as those consisting of supported nanoparticles. We go on to review how a confocal geometry may improve the depth resolution for extended objects. Finally, we present a review of recent work exploring the effect of dynamical diffraction in zone-axis-aligned crystals on the optical sectioning process.
High-energy-resolution monochromator for aberration-corrected scanning transmission electron microscopy/electron energy-loss spectroscopy
Authors: Krivanek Ondrej L. , Ursin Jonathan P. , Bacon Neil J. , Corbin George J. , Dellby Niklas , Hrncirik Petr , Murfitt Matthew F. , Own Christopher S. , Szilagyi Zoltan S.
Published: August 2009

An all-magnetic monochromator/spectrometer system for sub-30 meV energy-resolution electron energy-loss spectroscopy in the scanning transmission electron microscope is described. It will link the energy being selected by the monochromator to the energy being analysed by the spectrometer, without resorting to decelerating the electron beam. This will allow it to attain spectral energy stability comparable to systems using monochromators and spectrometers that are raised to near the high voltage of the instrument. It will also be able to correct the chromatic aberration of the probe-forming column. It should be able to provide variable energy resolution down to approximately 10 meV and spatial resolution less than 1 Å.
Background, status and future of the Transmission Electron Aberration-corrected Microscope project
Authors: Dahmen Ulrich , Erni Rolf , Radmilovic Velimir , Ksielowski Christian , Rossell Marta-Dacil , Denes Peter
Published: August 2009

The strong interaction of electrons with small volumes of matter make them an ideal probe for nanomaterials, but our ability to fully use this signal in electron microscopes remains limited by lens aberrations. To bring this unique advantage to bear on materials research requires a sample space for electron scattering experiments in a tunable electron-optical environment. This is the vision for the Transmission Electron Aberration-corrected Microscope (TEAM) project, which was initiated as a collaborative effort to re-design the electron microscope around aberration-correcting optics. The resulting improvements in spatial, spectral and temporal resolution, the increased space around the sample and the possibility of exotic electron-optical settings will enable new types of experiments. This contribution will give an overview of the TEAM project and its current status, illustrate the performance of the TEAM 0.5 instrument, with highlights from early applications of the machine, and outline future scientific opportunities for aberration-corrected microscopy.
Aberration-corrected scanning transmission electron microscopy: from atomic imaging and analysis to solving energy problems
Authors: Pennycook S. J. , Chisholm M. F. , Lupini A. R. , Varela M. , Borisevich A. Y. , Oxley M. P. , Luo W. D. , van Benthem K. , Oh S.-H. , Sales D. L. , Molina S. I. , García-Barriocanal J. , Leon C. , Santamaría J. , Rashkeev S. N. , Pantelides S. T.
Published: August 2009

The new possibilities of aberration-corrected scanning transmission electron microscopy (STEM) extend far beyond the factor of 2 or more in lateral resolution that was the original motivation. The smaller probe also gives enhanced single atom sensitivity, both for imaging and for spectroscopy, enabling light elements to be detected in a Z-contrast image and giving much improved phase contrast imaging using the bright field detector with pixel-by-pixel correlation with the Z-contrast image. Furthermore, the increased probe-forming aperture brings significant depth sensitivity and the possibility of optical sectioning to extract information in three dimensions. This paper reviews these recent advances with reference to several applications of relevance to energy, the origin of the low-temperature catalytic activity of nanophase Au, the nucleation and growth of semiconducting nanowires, and the origin of the eight orders of magnitude increased ionic conductivity in oxide superlattices. Possible future directions of aberration-corrected STEM for solving energy problems are outlined.
Chromatic correction: a revolution in electron microscopy?
Authors: Zach J.
Published: August 2009

When the development of correctors started in the 1970s, chromatic correction was already the main goal. The first corrector that could improve the resolution of an electron microscope was a chromatic corrector for a scanning electron microscope.

Within the last three decades, the development of transmission electron microscopes (TEMs) was to a large extent driven by the attempt to improve the resolution in the presence of chromatic aberration. The major technical developments were high acceleration voltages, highly excited objective lenses with short focal length and field emission guns.

Meanwhile, chromatic correction has reached the TEM world. Now, the question arises as to whether chromatic correction will make some of the aforementioned developments obsolete for high-resolution TEM, thereby opening up new imaging possibilities, which are nowadays prevented by instrument constraints. We show some examples for a 0.1 nm resolution TEM with unconventional microscope designs: very low voltages, far-field objective lenses and inexpensive electron guns.
Multi-dimensional and multi-signal approaches in scanning transmission electron microscopes
Authors: Colliex C. , Brun N. , Gloter A. , Imhoff D. , Kociak M. , March K. , Mory C. , Stéphan O. , Tencé M. , Walls M.
Published: August 2009

Developments in instrumentation are essential to open new fields of science. This clearly applies to electron microscopy, where recent progress in all hardware components and in digitally assisted data acquisition and processing has radically extended the domains of application. The demonstrated breakthroughs in electron optics, such as the successful design and practical realization and the use of correctors, filters and monochromators, and the permanent progress in detector efficiency have pushed forward the performance limits, in terms of spatial resolution in imaging, as well as for energy resolution in electron energy-loss spectroscopy (EELS) and for sensitivity to the identification of single atoms. As a consequence, the objects of the nanoworld, of natural or artificial origin, can now be explored at the ultimate atomic level. The improved energy resolution in EELS, which now encompasses the near-IR/visible/UV spectral domain, also broadens the range of available information, thus providing a powerful tool for the development of nanometre-level photonics. Furthermore, spherical aberration correctors offer an enlarged gap in the objective lens to accommodate nanolaboratory-type devices, while maintaining angström-level resolution for general characterization of the nano-object under study.