bluuebunny/crossref_metadata_2025 huggingface dataset:
Noncontact atomic force microscopy imaging of ferroelectric domains with functionalized tips
Authors: Nicklaus Mischa , Pignolet Alain , Harnagea Catalin , Ruediger Andreas
Published: April 2011

We report on an imaging method for ferroelectric domains by noncontact atomic force microscopy with dipole-molecule decorated tips. The Coulombic tip-sample interaction is revealing the domains monitored as an additional topography contribution. As proof of concept, we present agreement between numerical simulations and experiments on antiparallel out-of-plane domains on LiNbO3. This contact-free imaging technique promises substantially increased lifetime of read-heads for high-density ferroelectric data storages, and high resolution and improved image quality in scanning probe microscopy on systems with surface charge density variations.
Near band-edge electron diffusion in electrospun Nb-doped anatase TiO2 nanofibers probed by electrochemical impedance spectroscopy
Authors: Archana P. S. , Jose R. , Yusoff M. M. , Ramakrishna S.
Published: April 2011

Charge transport through Nb-doped anatase TiO2 nanofibers (diameter ∼100 nm) developed by electrospinning is studied under the framework of hopping transport using electrochemical impedance spectroscopy measurements. It is observed that the Fermi level of TiO2 rise close to its conduction band and result in a band-edge type diffusion mechanism even at low bias voltages when 2 at % Nb atoms replaces the Ti atoms in the anatase lattice. The Nb-doped anatase electrospun nanofibers showed high chemical capacitance, high effective diffusion coefficient, and lower transport resistance compared to the undoped samples and conventional nanoparticles (25 nm).
Measurement of oxygen diffusion in nanometer scale HfO2 gate dielectric films
Authors: Zafar Sufi , Jagannathan Hemanth , Edge Lisa F. , Gupta Devendra
Published: April 2011

Diffusion of oxygen ions in thin (≲40 Å) HfO2 gate dielectric films is measured using transient gate currents. The diffusion coefficient is estimated to be ∼1×10−14 cm2/s at room temperature, and is observed to be thermally activated with an activation energy of ∼0.52 eV for nanometer scale HfO2 films. The diffusion results are shown to be consistent with those for positively charged oxygen vacancies in bulk samples of similar oxides, and first principle calculation results for oxygen vacancy diffusion in thin HfO2 films. Thus, we demonstrate a method for measuring oxygen diffusion in thin HfO2 films where diffusion measurements by the conventional techniques have been elusive.
Selective excitation of homogeneous spectral lines
Authors: Khitrin A. K.
Published: April 2011

It is possible, by selective excitation of homogeneously broadened lines, to produce response signals, which are orders of magnitude narrower than the original lines. The new type of echo, which allows detecting such signals, and the formalism, useful for understanding the phenomenon, as well as the experimental examples from NMR spectroscopy are presented. Long-lived partial NMR echo in solids can be excited by a simple two-pulse Hahn sequence.
Thermodynamic properties of methane/water interface predicted by molecular dynamics simulations
Authors: Sakamaki Ryuji , Sum Amadeu K. , Narumi Tetsu , Ohmura Ryo , Yasuoka Kenji
Published: April 2011

Molecular dynamics simulations have been performed to examine the thermodynamic properties of methane/water interface using two different water models, the TIP4P/2005 and SPC/E, and two sets of combining rules. The density profiles, interfacial tensions, surface excesses, surface pressures, and coexisting densities are calculated over a wide range of pressure conditions. The TIP4P/2005 water model was used, with an optimized combining rule between water and methane fit to the solubility, to provide good predictions of interfacial properties. The use of the infinite dilution approximation to calculate the surface excesses from the interfacial tensions is examined comparing the surface pressures obtained by different approaches. It is shown that both the change of methane solubilities in pressure and position of maximum methane density profile at the interface are independent of pressure up to about 2 MPa. We have also calculated the adsorption enthalpies and entropies to describe the temperature dependency of the adsorption.
Note: Ferrule-top atomic force microscope. II. Imaging in tapping mode and at low temperature
Authors: Chavan D. , Andres D. , Iannuzzi D.
Published: April 2011

In a recent paper [D.Chavan et al., Rev. Sci. Instrum. 81, 123702 (2010)] we have demonstrated that ferrule-top cantilevers, obtained by carving the end of a ferruled fiber, can be used for contact mode atomic force microscopy in ambient conditions. Here we show that those probes can provide tapping mode images at both room and cryogenic temperatures (12 K).
Resonance hybridization in nanoantenna arrays based on asymmetric split-ring resonators
Authors: Lahiri Basudev , McMeekin Scott G. , De La Rue Richard M. , Johnson Nigel P.
Published: April 2011

Asymmetric split ring resonators (A-SRRs) are composed of two separate metallic arcs of asymmetric lengths that share the same center-of-curvature. The two arcs interact to produce a very steep slope in the reflection spectrum. We utilize the plasmon resonance hybridization model to understand and describe the working of an A-SRR and produce experimental and simulation results to show that the A-SRR resonances are a “modified linear superposition” of the individual plasmon resonances coming from each of the arcs.
Effect of quenched size polydispersity on the fluid-solid transition in charged colloidal suspensions
Authors: Colombo Jader , Dijkstra Marjolein
Published: April 2011

We study the effect of quenched size polydispersity on the phase behavior of charged colloidal suspensions using free-energy calculations in Monte Carlo simulations. The colloids are assumed to interact with a hard-core repulsive Yukawa (screened-Coulomb) interaction with constant surface potential, so that the particles are polydisperse both in size and charge. In addition, we take the size distribution to be fixed in both the fluid and crystal phase (no size fractionation is allowed). We study the fluid–solid transition for various screening lengths and surface potentials, finding that upon increasing the size polydispersity the freezing transition shifts toward higher packing fractions and the density discontinuity between the two coexisting phases diminishes. Our results provide support for a terminal polydispersity above which the freezing transition disappears.
Mode transitions in an oscillating liquid sheet
Authors: Lozano A. , Calvo E. , García J. A. , Barreras F.
Published: April 2011

Longitudinal oscillations in air-blasted or air-assisted liquid sheets have been the subject of a large number of papers in the last 30 years. Frequency and sometimes amplitude are the main parameters used to characterize these oscillations. Attending to them, and also in dependence on the surface topology (e.g., the presence of perforations or ligaments), several oscillation modes have been described. In most works, two or at most three regimes are considered. Following these previous descriptions, this experimental work has found that some submodes can also be discerned. Based on visual observations, frequency measurements, and spray angle calculations, for some liquid and air flow rates up to six modes have been observed with defined transitions among them. The different modes are analyzed and characterized, and their presence is related to the flow conditions.
Electronic structure of hole centers in CuO2 planes of cuprates
Authors: Moskvin A. S. , Panov Yu. D.
Published: April 2011

A theoretical analysis and a large amount of experimental data indicate that the structure of the valence hole states in doped cuprates is more complicated than assumed in the simple Zhang-Rice singlet model. In fact, we are dealing with a competition between a hybrid Cu3d–O2pb1g∝dx2−y2-state and purely oxygen nonbonding states with a2g- and eux,y∝px,y-symmetries. Thus, as a cluster analog of a Cu3+ ion, the ground state of a non-Zhang-Rice CuO45− hole center of this sort should be described by complicated A1g1−B2g1,3−Eu1,3 multiplet with a set of charge, orbital, and spin order parameters, some of which are well known (e.g., spin moment or “ferromagnetic” Ising orbital momentum localized on oxygen ions) while others are unconventional or hidden (e.g., “antiferromagnetic” ordering of Ising orbital momenta localized on four oxygen atoms or a combined spin-orbital-quadrupole ordering). The non-Zhang-Rice CuO45− centers are actually singlet-triplet pseudo-Jahn-Teller centers with strong vibron coupling to the lattice. The complicated structure of the ground-state multiplet of the hole centers shows up in many of the unusual properties of doped cuprates, in particular, their pseudo-gap phase.
An ultrathin twist-structure polarization transformer based on fish-scale metallic wires
Authors: Han Jin , Li Hongqiang , Fan Yuancheng , Wei Zeyong , Wu Chao , Cao Yang , Yu Xing , Li Fang , Wang Zhanshan
Published: April 2011

This study theoretically and experimentally investigates the transmission properties of a metamaterial slab comprised of two layers of metallic fish-scale structure arrays and a sandwiched dielectric layer. Calculations show that the asymmetric transmission can be tuned by varying the slab thickness, due to near-field interlayer coupling. The spatial evolution of the electric field indicates that the twist structure functions as a perfect polarization transformer at certain frequencies. Measured transmission spectra are in good agreement with calculated results when material dissipation is considered.
Giant dynamical Stark shift in germanium quantum wells
Authors: Köster Niko S. , Kolata Kolja , Woscholski Ronja , Lange Christoph , Isella Giovanni , Chrastina Daniel , von Känel Hans , Chatterjee Sangam
Published: April 2011

We report a strong dynamical (ac) Stark shift of the direct gap transitions in Ge quantum wells at both cryogenic and room temperature. A blueshift of 67 meV is observed, exceeding values reported for III-V materials by about an order of magnitude. The fast intervalley scattering in the Ge material system leads to short dephasing times which in return causes larger shifts.
Near 1 V open circuit voltage InAs/GaAs quantum dot solar cells
Authors: Bailey Christopher G. , Forbes David V. , Raffaelle Ryne P. , Hubbard Seth M.
Published: April 2011

Ten-layer InAs/GaAs quantum dot (QD) solar cells exhibiting enhanced short circuit current (Jsc) and open circuit voltage (Voc) comparable to a control GaAs p-i-n solar cell are reported. 1 sun Jsc is enhanced by 3.5% compared to that of the GaAs control, while the Voc is maintained at 994 mV. Results were achieved using optimized InAs QD coverage and a modified strain balancing technique, resulting in a high QD density (3.6×1010 cm−2), uniform QD size (4×16 nm2), and low residual strain (103 ppm). This enhanced Voc is a promising result for the future of InAs QD-enhanced GaAs solar cells.
Pressure and shear horizontal guided waves excitation: Nonuniform, time-periodic source distribution of finite extent on the boundaries
Authors: Valier-Brasier Tony , Potel Catherine , Bruneau Michel
Published: April 2011

There is a class of waveguides problems in which energy is provided by a source distribution of finite extent on the surface of the guide and for which usually the behavior of the acoustic field created is not analytically correlated with the source strength. The present paper aims at providing an analytical model describing the field which can be obtained from such nonuniformly distributed, time-periodic source creating either pressure waves in fluid-filled waveguides or Shear Horizontal waves in isotropic solid plates. This model involves convolution products between appropriate Green’s functions and the source stress. A relevant example is finally displayed.
Electron field emission enhanced by geometric and quantum effects from nanostructured AlGaN/GaN quantum wells
Authors: Zhao Wei , Wang Ru-Zhi , Song Xue-Mei , Wang Hao , Wang Bo , Yan Hui , Chu Paul K.
Published: April 2011

Electron field emitters that provide intense and stable currents are important to vacuum microelectronic devices. In this work, we demonstrate high-performance electron field emission (FE) from nanostructured AlGaN/GaN quantum wells by coupling the quantum and geometric effects. Pulsed laser deposition is utilized to fabricate the FE cathode. The field emitter exhibits a low threshold field of only 1.1 V/μm and yields a stable emission current of 5 mA/cm2 at 1.8 V/μm, making it suitable for FE-based applications.
Surface ferromagnetism in hydrogenated-ZnO film
Authors: Li T. , Ong C. S. , Herng T. S. , Yi J. B. , Bao N. N. , Xue J. M. , Feng Y. P. , Ding J.
Published: April 2011

Nonmagnetic ZnO films were found to exhibit room temperature ferromagnetism after hydrogen annealing at elevated temperatures (100–500 °C), accompanied by (OH) bonds detection. The areal saturation magnetization Ms (∼1.1×10−5 emu cm−2) was insensitive to film thickness, suggesting surface magnetism. The attribution to OH bonds on surface was further supported when the ferromagnetism disappeared after a short immersion for 1 s in acid solution while ferromagnetism was relatively stable in basic environment. The alternative H2- and Ar-annealing can switch ferromagnetic “on” and “off” state, as the annealing under Ar atmosphere can reduce OH bond quantity significantly. First-principles calculations have further confirmed that OH-terminated ZnO surface belonging to the p31m two-dimensional space group has the lowest formation energy of −2.97 eV and a magnetic moment of 0.30 μB per OH due to unpaired magnetic moment of electrons occupying O 2p orbital. Insufficient surface OH concentration may result in antiferromagnetism and/or paramagnetism.
Observation of spin-orbital compensation in Sm1−xGdxNi2
Authors: Maji Bibekananda , Suresh K. G. , Nigam A. K.
Published: April 2011

A systematic study of Sm1−xGdxNi2 series shows signatures of perfect spin-orbital compensation at x=0.03 and 0.035. Magnetization measurements show that both these compounds magnetically order at about 25 K. Below this temperature, the magnetization data shows a compensation point. For x=0.04 and 0.05, large conduction electron polarization prevents the occurrence of exact compensation. The features seen in this case are found to be quite identical to those of the classical spin-orbit compensated ferromagnet, namely (Sm,Gd)Al2.
Low-voltage, high-efficiency nondoped phosphorescent organic light-emitting devices with double-quantum-well structure
Authors: Liu Shumei , Li Bin , Zhang Liming , Yue Shumei
Published: April 2011

Low-voltage and high-efficiency nondoped phosphorescent organic light-emitting devices are fabricated by introducing a simple triplet double-quantum-well structure with an Ir(III) complex as potential well layer (PWL) and emitting layer (EML). The effects of various potential barrier layer (PBL) on device performances are discussed. Remarkably, the device with 1,3,5-tris(N-phenyl-benzimidazol-2-yl)benzene (TPBi) as PBL shows a low turn-on voltage of 2.30 V, a maximum power efficiency of 30.5 lm/W at 2.65 V and 24.5 lm/W with 1000 cd/m2 at 3.75 V. We attribute these to the efficient carrier/exciton confinement function of TPBi and the improvement of carrier injection/balance in PWL/EML by self-balancing effect.
ZnO nanowire-based all-optical switch with Reset-Set flip-flop function
Authors: Mu L. X. , Shi W. S. , Zhang T. P. , Zhang H. Y. , Wang Y. , She G. W. , Gao Y. H. , Wang P. F. , Chang J. C. , Lee S. T.
Published: April 2011

An all-optical switch with Reset-Set (RS) flip-flop function has been developed by attaching a derivative of spiropyran on the surface of zinc oxide (ZnO) Nanowire. Using UV/visible irradiation and the fluorescence of spiropyran-modified ZnO nanowire as inputs—set/reset and output, RS flip-flop function can be performed on a single ZnO nanowire or a nanowire array. The configuration of the current all-optical switch represents a potential for developing small-sized all-optical devices, which could be further exploited at higher level of integration.
Using patterned H-resist for controlled three-dimensional growth of nanostructures
Authors: Goh K. E. J. , Chen S. , Xu H. , Ballard J. , Randall J. N. , Von Ehr J. R.
Published: April 2011

We present a study addressing the effectiveness of a monolayer of hydrogen as the lithographic resist for controlled three-dimensional (3D) growth of nanostructures on the Si(100) surface. Nanoscale regions on the H-terminated Si(100) were defined by H-desorption lithography via the biased tip of a scanning tunneling microscope (STM) to create well-defined regions of surface “dangling bonds,” and the growth of 3D nanostructures within these regions was achieved using a simultaneous disilane deposition and STM H-desorption technique. We demonstrate that 3D growth is strongly confined within STM depassivated regions while unpatterned H:Si(100) regions are robust against adsorption of the precursor molecules.
Effect of DC bias on electrical conductivity of nanocrystalline α-CuSCN
Authors: Prakash T. , Ramasamy S. , Murty B. S.
Published: April 2011

The grain boundary space charge depletion layer in nanocrystalline alpha phase CuSCN is investigated by studying electrical properties using impedance spectroscopic analysis in frequency domain. The measurements were performed at room temperature in wide frequency range 1 Hz to 1 MHz under various DC bias applied voltages ranges from 0 V to -2.1 V. The effect of bias on grain and grain boundary contribution electrical conductivity has been investigated by equivalent circuit model using non-linear least squares (NLLS) fitting of the impedance data. Three order of magnitude variation of grain boundary conductivity was observed for varying 0 V to -2.1 V. Variations in the σac clearly elucidate the DC bias is playing crucial role on grain boundary double Schottky barriers of nanocrystalline α-CuSCN.
The Speed of Recognition of Personally Familiar Faces
Authors: Ramon Meike , Caharel Stephanie , Rossion Bruno
Published: April 2011

Despite the generally accepted notion that humans are very good and fast at recognising familiar individuals from their faces, the actual speed with which this fundamental brain function can be achieved remains largely unknown. Here, two groups of participants were required to respond by finger-lift when presented with either a photograph of a personally familiar face (classmate), or an unfamiliar one. This speeded manual go/no-go categorisation task revealed that personally familiar faces could be categorised as early as 380 ms after presentation, about 80 ms faster than unfamiliar faces. When response times were averaged across all 8 stimulus presentations, we found that minimum RTs for both familiar and unfamiliar face decisions were substantially lower (310 ms and 370 ms). Analyses confirmed that stimulus repetition enhanced the speed with which faces were categorised, irrespective of familiarity, and that repetition did not affect the observed benefit in RTS for familiar over unfamiliar faces. These data, representing the elapsed time from stimulus onset to motor output, put constraints on the time course of familiar face recognition in the human brain, which can be tracked more precisely by high temporal resolution electrophysiological measures.
Flexible Resource Allocation for the Detection of Changing Visual Features
Authors: Burmester Alex , Wallis Guy
Published: April 2011

Failure to detect change under circumstances where visual input is interrupted or attention is distracted is indicative of the capacity limits of visual short-term memory. The current study attempts to probe the nature of these limits. In experiment 1, the appearance of single Gabor patches was altered across colour, size, or speed, and set size was manipulated by means of a visual cue. In experiment 2, performance for detecting single and multiple changes to Gabor patches was compared under the constraint that the inherent detectability of each individual change was the same. Experiment 1 yielded a particular set size (4) and a particular level of change magnitude at which performance was equivalent across change type. On the basis of these parameter values, experiment 2 revealed that the detectability of two features changing within one object was the same as the detectability of a single feature changing across two objects, and that this level of detectability could be predicted by a simple model of probability summation. Together, these results suggest that performance is determined by the magnitude of featural changes independently of the way they are distributed across objects. We suggest they are adequately explained by a flexible-resource-allocation model rather than a slot-allocation model.
An Oxidized Abasic Lesion as an Intramolecular Source of DNA Adducts
Authors: Guan Lirui , Greenberg Marc M.
Published: April 2011

5′-(2-Phosphoryl-1,4-dioxobutane) (DOB) is a lesion produced in DNA via a variety of damaging agents. The DOB lesion spontaneously generates cis- and trans-but-2-en-1,4-dial (1) via β-elimination. Cis- and trans-but-2-en-1,4-dial forms exocyclic adducts with nucleosides. We used chemically synthesized DNA containing tritiated DOB incorporated at defined sites to examine the reactivity of cis- and trans-but-2-en-1,4-dial. Although the local DNA sequence does not appear to influence the distribution of nucleoside adducts, we find that DOB generates relatively high yields of cis- and trans-but-2-en-1,4-dial nucleoside adducts that likely are promutagenic.
Fluoroazaindolines by an Uncommon Radical ipso-Substitution of a C-F Bond
Authors: Laot Yann , Petit Laurent , Tran Ngoc Diem My , Zard Samir Z.
Published: April 2011

Trifluoroazaindoline derivatives are prepared using the first synthetically useful radical ipso-substitution of a fluorine atom. The initial procedure has been improved to allow the gram scale synthesis of these building blocks, which can be regioselectively substituted by nucleophiles under mild conditions to rapidly access a library of new molecules. Oxidation to the corresponding fluoroazaindole core has also been accomplished.
Profluorescent Nitroxides as Sensitive Probes of Oxidative Change and Free Radical Reactions
Authors: Blinco James P. , Fairfull-Smith Kathryn E. , Morrow Benjamin J. , Bottle Steven E.
Published: April 2011

This paper presents a review on the use of tethered nitroxide–fluorophore molecules as probes of oxidative change and free radical generation and reaction. The proximity of the nitroxide free radical to the fluorophore suppresses the normal fluorescence emission process. Nitroxide free radical scavenging, metabolism or redox chemistry return the system to its natural fluorescent state and so these tethered nitroxide–fluorophore molecules are described as being profluorescent. A survey of profluorescent nitroxides found in the literature is provided as well as background on the mechanism of action and applications of these compounds as fluorometric probes within the fields of biological, materials and environmental sciences.
Synthetic and Computational Studies of Acyl Radical Cyclizations with β-Alkoxyacrylates: Formal Synthesis of (±)-Longianone
Authors: Aitken Heather M. , Schiesser Carl H. , Donner Christopher D.
Published: April 2011

An investigation into the cyclization of acyl radicals with mono- and disubstituted β-alkoxyacrylates is described. Ether-tethered acyl radicals, generated directly from the corresponding aldehyde, undergo cyclization to form dioxaspiro heterocyclic systems including 1,7-dioxaspiro[4,4]nonane-4,8-dione and 1,8-dioxaspiro[5,4]decane-5,9-dione. This strategy is applied to a concise formal synthesis of the fungal metabolite longianone. Density functional theory calculations provide insight into the chemistry of the acyl radicals in this study.
Reaction of N-Acyloxy-N-alkoxyamides with Biological Thiol Groups
Authors: Glover Stephen A. , Adams Meredith
Published: April 2011

Mutagenic N-acyloxy-N-alkoxyamides 1 react with thiols by an SN2 process at nitrogen with displacement of carboxylate. They react with glutathione 4 in [D6]DMSO/D2O and methyl and ethyl esters of cysteine hydrochloride, 11 and 12, in [D4]methanol but the intermediate N-alkoxy-N-(alkylthio)amides undergo a rapid substitution reaction at sulfur by a second thiol molecule to give hydroxamic esters and disulfides. Arrhenius activation energies and entropies of activation obtained for a series of different N-benzyloxy-N-(4-substitutedbenzoyloxy)benzamides 13–17 were similar to those found for the SN2 reaction of the same series with N-methylaniline. Entropies of activation were strongly negative in keeping with polar separation and attendant solvation in the transition state, and in keeping with this, bimolecular reaction rate constants at 298 K correlated with Hammett σ constants with a positive ρ-value of 1.1. The structure of model N-methoxy-N-(methylthio)acetamide has been computed at the B3LYP/6–31G(d) level and exhibits properties atypical of other anomeric amides with more electronegative atoms at nitrogen. Relative to N,N-bisoxyl substitution, the combination of a sulfur and an oxygen atom at the amide nitrogen results in a relatively small reduction in amide resonance.
Cognitive and motivational contributors to aptitude
Authors: Shaw Sherry
Published: April 2011

This article reports the findings of a causal-comparative study with spoken language (primarily conference) and signed language (primarily public service) interpreting students carried out at four institutions in the European Union in 2008. The study was built on two previous investigations of essential characteristics, as reported by interpreting students and their professors, to measure these characteristics with standardized performance and motivation tests. It grouped participants as “entry-level” or “advanced” depending upon their prior experience in simultaneous interpreting coursework. The study documented cognitive and motivational scores of spoken language (SP) and signed language (SL) interpreting students at both levels, using a computerized neuropsychological screening test and an achievement motivation instrument. Significant differences between the SP and SL students were found in the areas of visual memory, concentration, and internality (belief that success is due to internal causes), and between the advanced and entry-level students in the areas of concentration and the eagerness to learn new concepts in the absence of external rewards.
Evaluating emotional stability as a predictor of interpreter competence and aptitude for interpreting
Authors: Bontempo Karen , Napier Jemina
Published: April 2011

This paper proposes that variance in interpreter performance is dependent on factors of both general cognitive ability and personality. Whilst there is no doubt of the interplay between individual personality traits and job performance across many occupations, the greatest interest lies in determining which traits play the most important role; and to what extent these variables impact on learning and achievement. The paper reports on a study of 110 accredited signed language interpreters in Australia. Psychological constructs of self-efficacy, goal orientation and negative affectivity were measured, as were interpreter ratings of self-perceived competence as practitioners. The most significant finding revealed the dimension of emotional stability (represented on the negative end of the continuum by traits of anxiety and neuroticism, and measured in this study by the negative affectivity scale) as a predictor of interpreter’s self-perceived competence. Based on these findings, recommendations for admission testing and interpreter education curricula are discussed.
SOCIAL AND ECONOMIC IMPACT OF THE HEADSCARF BAN ON WOMEN IN TURKEY
Authors: Guveli Ayse
Published: April 2011

The headscarf ban in Turkey has provoked heated debate both in and outside the country. A great deal of research considers the broader philosophical, political, historical, and social implications of the ban but to this point, no large-scale study has focused on the social and economic implications for the women themselves. This study addresses this issue, arguing that the intensification of the ban after the 1980s served the exclusionist aims of the elite to protect their privileged positions and to slow social and regional mobility. Using data collected in 2007 from 1,206 women, we show that women have been affected negatively in a variety of ways. Veiled women have a significantly lower level of education and are substantially more likely to be unemployed than unveiled women. Veiled women from cities where the ruling party argues for banning the headscarf in the public domain have lower levels of education and a higher level of unemployment than veiled women in cities where the ruling party is against the ban.
Angelika Amon: Conquering the divide
Authors: Short Ben
Published: April 2011

Amon studies how cells segregate their chromosomes and what happens when they get it wrong.
Isoform-specific targeting of PKA to multivesicular bodies
Authors: Day Michele E. , Gaietta Guido M. , Sastri Mira , Koller Antonius , Mackey Mason R. , Scott John D. , Perkins Guy A. , Ellisman Mark H. , Taylor Susan S.
Published: April 2011

Although RII protein kinase A (PKA) regulatory subunits are constitutively localized to discrete cellular compartments through binding to A-kinase–anchoring proteins (AKAPs), RI subunits are primarily diffuse in the cytoplasm. In this paper, we report a novel AKAP-dependent localization of RIα to distinct organelles, specifically, multivesicular bodies (MVBs). This localization depends on binding to AKAP11, which binds tightly to free RIα or RIα in complex with catalytic subunit (holoenzyme). However, recruitment to MVBs occurs only with the release of PKA catalytic subunit (PKAc). This recruitment is reversed by reassociation with PKAc, and it is disrupted by the presence of AKAP peptides, mutations in the RIα AKAP-binding site, or knockdown of AKAP11. Cyclic adenosine monophosphate binding not only unleashes active PKAc but also leads to the targeting of AKAP11:RIα to MVBs. Therefore, we show that the RIα holoenzyme is part of a signaling complex with AKAP11, in which AKAP11 may direct RIα functionality after disassociation from PKAc. This model defines a new paradigm for PKA signaling.
Measurements of spatiotemporal changes in G-actin concentration reveal its effect on stimulus-induced actin assembly and lamellipodium extension
Authors: Kiuchi Tai , Nagai Tomoaki , Ohashi Kazumasa , Mizuno Kensaku
Published: April 2011

To understand the intracellular role of G-actin concentration in stimulus-induced actin assembly and lamellipodium extension during cell migration, we developed a novel technique for quantifying spatiotemporal changes in G-actin concentration in live cells, consisting of sequential measurements of fluorescent decay after photoactivation (FDAP) of Dronpa-labeled actin. Cytoplasmic G-actin concentrations decreased by ∼40% immediately after cell stimulation and thereafter the cell area extended. The extent of stimulus-induced G-actin loss and cell extension correlated linearly with G-actin concentration in unstimulated cells, even at concentrations much higher than the critical concentration of actin filaments, indicating that cytoplasmic G-actin concentration is a critical parameter for determining the extent of stimulus-induced G-actin assembly and cell extension. Multipoint FDAP analysis revealed that G-actin concentration in lamellipodia was comparable to that in the cell body. We also assessed the cellular concentrations of free G-actin, profilin- and thymosin-β4–bound G-actin, and free barbed and pointed ends of actin filaments by model fitting of jasplakinolide-induced temporal changes in G-actin concentration.
Effects of Pearling, Grinding Conditions, and Roller Mill Flow on the Yield and Composition of Milled Products from Hull‐less Barley
Authors: Izydorczyk M. S. , McMillan T. L. , Kletke J. B. , Dexter J. E.
Published: April 2011

Two hull‐less barley cultivars, one with waxy starch and the other with high‐amylose starch, were roller‐milled unpearled and after 15% pearling. Flows of varying length, with diverse roll settings and roll surfaces were used to determine effects on the yield, composition, and properties of milled products. Similar trends were noted for the two cultivars. When using a short flow comprising four break passages and a sizing passage, power consumption during grinding was reduced by 10% when roll flute orientation was changed from dull‐to‐dull (D/D) to sharp‐to‐sharp (S/S). Flute orientation had minimal effects on the yield and brightness of flour, but SS grinding gave a higher yield of a fiber‐rich fraction (FRF). FRF yield and composition are of particular interest because FRF has potential as a functional food ingredient due to elevated levels of β‐glucans (BG) and arabinoxylans (AX). When using smooth frosted rolls (SM) for the sizing passage, power consumption increased by several times over using fluted sizing rolls with little advantage for either yield or BG content of FRF. FRF starch damage increased when smooth sizing rolls were used, and water swelling, a measure of water hydration capacity, also increased. Setting break and sizing rolls sharp‐to‐sharp significantly lowered the mean particle size of the FRF fraction, accompanied by moderate declines in FRF BG and AX contents. FRF yield decreased ≤50% when milling flow was lengthened to three sizing passages with intermediate impact passages, with only a moderate accompanying increase in FRF fiber content, regardless of roll conditions. Pearling 15% before milling reduced the yield of FRF by ≈30% while moderately reducing flour yield. Flour brightness was improved by pearling. When barley was pearled, FRF contained higher amounts of BG, but lower amounts of AX, phenolics, ash, and protein.
Epidemics of Ray Blight on Pyrethrum are Linked to Seed Contamination and Overwintering Inoculum of Phoma ligulicola var. inoxydabilis
Authors: Pethybridge Sarah J. , Gent David H. , Hay Frank S.
Published: April 2011

Ray blight, caused by Phoma ligulicola var. inoxydabilis, is the most damaging disease of pyrethrum (Tanacetum cinerariifolium) in Australia. Data collected from 72 plots in commercial pyrethrum fields since 2001 to 2009 revealed substantial annual variations in isolation frequency of the pathogen during semidormancy of the crop in autumn and winter. Isolation frequency of the pathogen during this time and subsequent outbreaks of ray blight in spring were similar across the eight production regions where sampling was conducted, and isolation frequency of the pathogen was linearly correlated (r = 0.88; P < 0.0001) with subsequent defoliation severity when plants commenced growth in spring. Isolation frequency and defoliation severity also were correlated with the incidence of seed infested with P. ligulicola var. inoxydabilis (r = 0.71 and 0.44, respectively; P < 0.0001 in both correlations). Highly accurate risk algorithms for the occurrence of severe epidemics of ray blight were constructed using logistic regression. A model based solely on isolation frequency of the pathogen over autumn and winter correctly predicted epidemic development in 92% of fields. Another model utilizing the incidence of infested seed and rain–temperature interactions in early autumn (austral March and April) and late winter (austral June and July) had similar predictive ability (92% accuracy). Path analysis modeling was used to disentangle interrelationships among the explanatory variables used in the second logistic regression model. The analysis indicated that seedborne inoculum of P. ligulicola var. inoxydabilis contributes indirectly to ray blight defoliation severity through directly increasing overwintering frequency of the pathogen. Autumn and fall weather variables were modeled to have indirect effects on defoliation severity through increasing overwintering success of the pathogen but also direct effects on defoliation severity. Collectively, the analyses point to several critical stages in the disease cycle that can be targeted to minimize the probability of regional epidemics of ray blight in this perennial pathosystem.
Greenhouse gases in the Earth system: a palaeoclimate perspective
Authors: Wolff Eric W.
Published: April 2011

While the trends in greenhouse gas concentrations in recent decades are clear, their significance is only revealed when viewed in the context of a longer time period. Fortunately, the air bubbles in polar ice cores provide an unusually direct method of determining the concentrations of stable gases over a period of (so far) 800 000 years. Measurements on different cores with varying characteristics, as well as an overlap of ice-core and atmospheric measurements covering the same time period, show that the ice-core record provides a faithful record of changing atmospheric composition. The mixing ratio of CO
2
is now 30 per cent higher than any value observed in the ice-core record, while methane is more than double any observed value; the rate of change also appears extraordinary compared with natural changes. Before the period when anthropogenic changes have dominated, there are very interesting natural changes in concentration, particularly across glacial/interglacial cycles, and these can be used to understand feedbacks in the Earth system. The phasing of changes in temperature and CO
2
across glacial/interglacial transitions is consistent with the idea that CO
2
acts as an important amplifier of climate changes in the natural system. Even larger changes are inferred to have occurred in periods earlier than the ice cores cover, and these events might be used to constrain assessments of the way the Earth could respond to higher than present concentrations of CO
2
, and to a large release of carbon: however, more certainty about CO
2
concentrations beyond the time period covered by ice cores is needed before such constraints can be fully realized.
HIAPER Pole-to-Pole Observations (HIPPO): fine-grained, global-scale measurements of climatically important atmospheric gases and aerosols
Authors: Wofsy S. C.
Published: April 2011

The HIAPER Pole-to-Pole Observations (HIPPO) programme has completed three of five planned aircraft transects spanning the Pacific from 85° N to 67° S, with vertical profiles every approximately 2.2° of latitude. Measurements include greenhouse gases, long-lived tracers, reactive species, O
2
/N
2
ratio, black carbon (BC), aerosols and CO
2
isotopes. Our goals are to address the problem of determining surface emissions, transport strength and patterns, and removal rates of atmospheric trace gases and aerosols at global scales and to provide strong tests of satellite data and global models. HIPPO data show dense pollution and BC at high altitudes over the Arctic, imprints of large N
2
O sources from tropical lands and convective storms, sources of pollution and biogenic CH
4
in the Arctic, and summertime uptake of CO
2
and sources for O
2
at high southern latitudes. Global chemical signatures of atmospheric transport are imaged, showing remarkably sharp horizontal gradients at air mass boundaries, weak vertical gradients and inverted profiles (maxima aloft) in both hemispheres. These features challenge satellite algorithms, global models and inversion analyses to derive surface fluxes. HIPPO data can play a crucial role in identifying and resolving questions of global sources, sinks and transport of atmospheric gases and aerosols.
Highly contrasting effects of different climate forcing agents on terrestrial ecosystem services
Authors: Huntingford C. , Cox P. M. , Mercado L. M. , Sitch S. , Bellouin N. , Boucher O. , Gedney N.
Published: April 2011

Many atmospheric constituents besides carbon dioxide (CO
2
) contribute to global warming, and it is common to compare their influence on climate in terms of radiative forcing, which measures their impact on the planetary energy budget. A number of recent studies have shown that many radiatively active constituents also have important impacts on the physiological functioning of ecosystems, and thus the ‘ecosystem services’ that humankind relies upon. CO
2
increases have most probably increased river runoff and had generally positive impacts on plant growth where nutrients are non-limiting, whereas increases in near-surface ozone (O
3
) are very detrimental to plant productivity. Atmospheric aerosols increase the fraction of surface diffuse light, which is beneficial for plant growth. To illustrate these differences, we present the impact on net primary productivity and runoff of higher CO
2
, higher near-surface O
3
, and lower sulphate aerosols, and for equivalent changes in radiative forcing. We compare this with the impact of climate change alone, arising, for example, from a physiologically inactive gas such as methane (CH
4
). For equivalent levels of change in radiative forcing, we show that the combined climate and physiological impacts of these individual agents vary markedly and in some cases actually differ in sign. This study highlights the need to develop more informative metrics of the impact of changing atmospheric constituents that go beyond simple radiative forcing.
Impact of episodic vertical fluxes on sea surface pCO
2
Authors: Mahadevan A. , Tagliabue A. , Bopp L. , Lenton A. , Mémery L. , Lévy M.
Published: April 2011

Episodic events like hurricanes, storms and frontal- and eddy-driven upwelling can alter the partial pressure of CO
2
(pCO
2
) at the sea surface by entraining subsurface waters into the surface mixed layer (ML) of the ocean. Since pCO
2
is a function of total dissolved inorganic carbon (DIC), temperature (
T
), salinity and alkalinity, it responds to the combined impacts of physical, chemical and biological changes. Here, we present an analytical framework for assessing the relative magnitude and sign in the short-term perturbation of surface pCO
2
arising from vertical mixing events. Using global, monthly, climatological datasets, we assess the individual, as well as integrated, contribution of various properties to surface pCO
2
in response to episodic mixing. The response depends on the relative vertical gradients of properties beneath the ML. Many areas of the ocean exhibit very little sensitivity to mixing owing to the compensatory effects of DIC and
T
on pCO
2
, whereas others, such as the eastern upwelling margins, have the potential to generate large positive/negative anomalies in surface pCO
2
. The response varies seasonally and spatially and becomes more intense in subtropical and subpolar regions during summer. Regions showing a greater pCO
2
response to vertical mixing are likely to exhibit higher spatial variability in surface pCO
2
on time scales of days.
Broader perspectives for comparing different greenhouse gases
Authors: Manning Martin , Reisinger Andy
Published: April 2011

Over the last 20 years, different greenhouse gases have been compared, in the context of climate change, primarily through the concept of global warming potentials (GWPs). This considers the climate forcing caused by pulse emissions and integrated over a fixed time horizon. Recent studies have shown that uncertainties in GWP values are significantly larger than previously thought and, while past literature in this area has raised alternative means of comparison, there is not yet any clear alternative. We propose that a broader framework for comparing greenhouse gases has become necessary and that this cannot be addressed by using simple fixed exchange rates. From a policy perspective, the framework needs to be clearly aligned with the goal of climate stabilization, and we show that comparisons between gases can be better addressed in this context by the forcing equivalence index (FEI). From a science perspective, a framework for comparing greenhouse gases should also consider the full range of processes that affect atmospheric composition and how these may alter for climate stabilization at different levels. We cover a basis for a broader approach to comparing greenhouse gases by summarizing the uncertainties in GWPs, linking those to uncertainties in the FEIs consistent with stabilization, and then to a framework for addressing uncertainties in the corresponding biogeochemical processes.
Constraining predictions of the carbon cycle using data
Authors: Rayner P. J. , Koffi E. , Scholze M. , Kaminski T. , Dufresne J.-L.
Published: April 2011

We use a carbon-cycle data assimilation system to estimate the terrestrial biospheric CO
2
flux until 2090. The terrestrial sink increases rapidly and the increase is stronger in the presence of climate change. Using a linearized model, we calculate the uncertainty in the flux owing to uncertainty in model parameters. The uncertainty is large and is dominated by the impact of soil moisture on heterotrophic respiration. We show that this uncertainty can be greatly reduced by constraining the model parameters with two decades of atmospheric measurements.
Greenhouse gases in the Earth system: setting the agenda to 2030
Authors: Manning Andrew C. , Nisbet Euan G. , Keeling Ralph F. , Liss Peter S.
Published: April 2011

What do we need to know about greenhouse gases? Over the next 20 years, how should scientists study the role of greenhouse gases in the Earth system and the changes that are taking place? These questions were addressed at a Royal Society scientific Discussion Meeting in London on 22–23 February 2010, with over 300 participants.
The weak link: do muscle properties determine locomotor performance in frogs?
Authors: Roberts Thomas J. , Abbott Emily M. , Azizi Emanuel
Published: April 2011

Muscles power movement, yet the conceptual link between muscle performance and locomotor performance is poorly developed. Frog jumping provides an ideal system to probe the relationship between muscle capacity and locomotor performance, because a jump is a single discrete event and mechanical power output is a critical determinant of jump distance. We tested the hypothesis that interspecific variation in jump performance could be explained by variability in available muscle power. We used force plate ergometry to measure power produced during jumping in Cuban tree frogs (Osteopilus septentrionalis), leopard frogs (Rana pipiens) and cane toads (Bufo marinus). We also measured peak isotonic power output in isolated plantaris muscles for each species. As expected, jump performance varied widely.Osteopilus septentrionalisdeveloped peak power outputs of 1047.0 ± 119.7 W kg−1hindlimb muscle mass, about five times that ofB. marinus(198.5 ± 54.5 W kg−1). Values forR. pipienswere intermediate (543.9 ± 96.2 W kg−1). These differences in jump power were not matched by differences in available muscle power, which were 312.7 ± 28.9, 321.8 ± 48.5 and 262.8 ± 23.2 W kg−1muscle mass forO. septentrionalis,R. pipiensandB. marinus, respectively. The lack of correlation between available muscle power and jump power suggests that non-muscular mechanisms (e.g. elastic energy storage) can obscure the link between muscle mechanical performance and locomotor performance.