bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of a radial fractional transport model with tokamak experiments
Authors: Kullberg A. , Morales G. J. , Maggs J. E.
Published: March 2014

A radial fractional transport model [Kullberg et al., Phys. Rev. E 87, 052115 (2013)], that correctly incorporates the geometric effects of the domain near the origin and removes the singular behavior at the outer boundary, is compared to results of off-axis heating experiments performed in the Rijnhuizen Tokamak Project (RTP), ASDEX Upgrade, JET, and DIII-D tokamak devices. This comparative study provides an initial assessment of the presence of fractional transport phenomena in magnetic confinement experiments. It is found that the nonlocal radial model is robust in describing the steady-state temperature profiles from RTP, but for the propagation of heat waves in ASDEX Upgrade, JET, and DIII-D the model is not clearly superior to predictions based on Fick's law. However, this comparative study does indicate that the order of the fractional derivative, α, is likely a function of radial position in the devices surveyed.
Surface plasmon induced enhancement with magneto-optical layer
Authors: Huang Hao-Ting , Ger Tzong-Rong , Xu You-Ren , Huang Chen-Yu , Liao Kuei-Tien , Lai Jun-Yang , Chen Jiann-Yeu , Chen Cheng-Huan , Wei Zung-Hang
Published: March 2014

In this study, we examined surface plasmon resonance (SPR) induced magneto-optical (MO) Kerr signals, and obtained a complete SPR curve in multilayered metallic structures comprising 6-nm-thick Au, t-nm-thick Permalloy (Py), and 26-nm-thick Au layers (with various thicknesses of Py). As the thickness of the Py layer increased, the SPR weakened. The MO signals were exhibited to various magnitudes of amplification while measuring the hysteresis loop at different segments of the SPR curve, which were the product of the MO Kerr effect. The MO signals between the reflectance maximum and reflectance minimum of the SPR were enhanced significantly in the samples with a 2 to 20-nm-thick Py layer. After measuring and analyzing the MO signals from multiple specimens with various thicknesses of Py, the optimal thickness of the Py layer was 10 nm, at which the strongest signal amplification was obtained.
Phase separation dynamics of simple liquids in non-uniform electric fields
Authors: Galanis Jennifer , Tsori Yoav
Published: March 2014

Spatially non-uniform electric fields can phase separate initially homogeneous mixtures of liquids. Here, we investigate the dynamics of phase separation using a modified Cahn-Hilliard equation and find three kinetically distinct regimes in the phase diagram: (1) discontinuous and (2) continuous interface formation kinetics and (3) a metastable state. By considering all possible solutions of the free energy density, we are able to map the time behavior in the vicinity of the interface as a series of equilibrium interfaces “moving” in the parameter space of the equilibrium phase diagram. The kinetic phase diagram, consequently, contains an “emergence line” that delineates the experimental conditions where a non-equilibrium interface can be forbidden from forming close to a charged surface. When the interface can form on the charged surface, an abrupt transition occurs that produces electrical signatures which distinguish the discontinuous from the continuous transition region. The third kinetic regime describes non-spontaneous phase separation and potential metastable states, and is bounded by the “electrostatic spinodal” line. The equivalent kinetic regimes exist in closed systems and can be found by considering an effective concentration in an open system.
High pressure elastic properties of minerals from ab initio simulations: The case of pyrope, grossular and andradite silicate garnets
Authors: Erba A. , Mahmoud A. , Belmonte D. , Dovesi R.
Published: March 2014

A computational strategy is devised for the accurate ab initio simulation of elastic properties of crystalline materials under pressure. The proposed scheme, based on the evaluation of the analytical stress tensor and on the automated computation of pressure-dependent elastic stiffness constants, is implemented in the CRYSTAL solid state quantum-chemical program. Elastic constants and related properties (bulk, shear and Young moduli, directional seismic wave velocities, elastic anisotropy index, Poisson's ratio, etc.) can be computed for crystals of any space group of symmetry. We apply such a technique to the study of high-pressure elastic properties of three silicate garnet end-members (namely, pyrope, grossular, and andradite) which are of great geophysical interest, being among the most important rock-forming minerals. The reliability of this theoretical approach is proved by comparing with available experimental measurements. The description of high-pressure properties provided by several equations of state is also critically discussed.
Ions in solution: Density corrected density functional theory (DC-DFT)
Authors: Kim Min-Cheol , Sim Eunji , Burke Kieron
Published: March 2014

Standard density functional approximations often give questionable results for odd-electron radical complexes, with the error typically attributed to self-interaction. In density corrected density functional theory (DC-DFT), certain classes of density functional theory calculations are significantly improved by using densities more accurate than the self-consistent densities. We discuss how to identify such cases, and how DC-DFT applies more generally. To illustrate, we calculate potential energy surfaces of HO·Cl− and HO·H2O complexes using various common approximate functionals, with and without this density correction. Commonly used approximations yield wrongly shaped surfaces and/or incorrect minima when calculated self consistently, while yielding almost identical shapes and minima when density corrected. This improvement is retained even in the presence of implicit solvent.
Surface tension and disjoining pressure of free-standing smectic films above the bulk smectic-A-isotropic transition temperature
Authors: Zakharov A. V. , Śliwa Izabela
Published: March 2014

We have carried out a numerical study of both the structural and thermodynamic properties of free-standing smectic films for the case of enhanced pair interaction in the bounding layers. Calculations, based upon the extended McMillan's mean-field theory with anisotropic forces, show that the layer-thinning transitions are characterized by abrupt drops to lower values, both for a disjoining pressure and a fluctuation-induced long-range interaction between the smectic film surfaces, and then continues to increase with a larger positive slope. Reasonable agreement between the theoretically predicted and the experimentally obtained data on the surface tension of the partially fluorinated 5-n-alkyl-2-(4-n-(perfluoroalkyl-metheleneoxy)phenyl) film has been obtained.
Effect of Ti-Al cathode composition on plasma generation and plasma transport in direct current vacuum arc
Authors: Zhirkov I. , Eriksson A. O. , Petruhins A. , Dahlqvist M. , Ingason A. S. , Rosen J.
Published: March 2014

DC arc plasma from Ti, Al, and Ti1-xAlx (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes was characterized with respect to plasma chemistry and charge-state-resolved ion energy. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the deposited films and the cathode surfaces were used for exploring the correlation between cathode-, plasma-, and film composition. Experimental work was performed at a base pressure of 10−6 Torr, to exclude plasma-gas interaction. The plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the cathode composition, while deposited films were in accordance with the cathode stoichiometry. This may be explained by presence of neutrals in the plasma/vapour phase. The average ion charge states (Ti = 2.2, Al = 1.65) were consistent with reference data for elemental cathodes, and approximately independent on the cathode composition. On the contrary, the width of the ion energy distributions (IEDs) were drastically reduced when comparing the elemental Ti and Al cathodes with Ti0.5Al0.5, going from ∼150 and ∼175 eV to ∼100 and ∼75 eV for Ti and Al ions, respectively. This may be explained by a reduction in electron temperature, commonly associated with the high energy tail of the IED. The average Ti and Al ion energies ranged between ∼50 and ∼61 eV, and ∼30 and ∼50 eV, respectively, for different cathode compositions. The attained energy trends were explained by the velocity rule for compound cathodes, which states that the most likely velocities of ions of different mass are equal. Hence, compared to elemental cathodes, the faster Al ions will be decelerated, and the slower Ti ions will be accelerated when originating from compound cathodes. The intensity of the macroparticle generation and thickness of the deposited films were also found to be dependent on the cathode composition. The presented results may be of importance for choice of cathodes for thin film depositions involving compound cathodes.
Quantitative analysis of electron energy loss spectra and modelling of optical properties of multilayer systems for extreme ultraviolet radiation regime
Authors: Gusenleitner S. , Handick E. , Hauschild D. , Reinert F.
Published: March 2014

Ruthenium capped multilayer coatings for use in the extreme ultraviolet (EUV) radiation regime have manifold applications in science and industry. Although the Ru cap shall protect the reflecting multilayers, the surface of the heterostructures suffers from contamination issues and surface degradation. In order to get a better understanding of the effects of these impurities on the optical parameters, reflection electron energy loss spectroscopy (REELS) measurements of contaminated and H cleaned Ru multilayer coatings were taken at various primary electron beam energies. Experiments conducted at low primary beam energies between 100 eV and 1000 eV are very surface sensitive due to the short inelastic mean free path of the electrons in this energy range. Therefore, influences of the surface condition on the above mentioned characteristics can be appraised. In this paper, it can be shown that carbon and oxide impurities on the mirror surface decrease the transmission of the Ru cap by about 0.75% and the overall reflectance of the device is impaired as the main share of the non-transmitted EUV light is absorbed in the contamination layer.
In situ controlled modification of the helium density in single helium-filled nanobubbles
Authors: David M.-L. , Alix K. , Pailloux F. , Mauchamp V. , Couillard M. , Botton G. A. , Pizzagalli L.
Published: March 2014

We demonstrate that the helium density and corresponding pressure can be modified in single nano-scale bubbles embedded in semiconductors by using the electron beam of a scanning transmission electron microscope as a multifunctional probe: the measurement probe for imaging and chemical analysis and the irradiation source to modify concomitantly the pressure in a controllable way by fine tuning of the electron beam parameters. The control of the detrapping rate is achieved by varying the experimental conditions. The underlying physical mechanisms are discussed; our experimental observations suggest that the helium detrapping from bubbles could be interpreted in terms of direct ballistic collisions, leading to the ejection of the helium atoms from the bubble.
Increasing the upper-limit intensity and temperature range for thermal self-focusing of a laser beam by using plasma density ramp-up
Authors: Bokaei B. , Niknam A. R.
Published: March 2014

This work is devoted to improving relativistic and ponderomotive thermal self-focusing of the intense laser beam in an underdense plasma. It is shown that the ponderomotive nonlinearity induces a saturation mechanism for thermal self-focusing. Therefore, in addition to the well-known lower-limit critical intensity, there is an upper-limit intensity for thermal self-focusing above which the laser beam starts to experience ponderomotive defocusing. It is indicated that the upper-limit intensity value is dependent on plasma and laser parameters such as the plasma electron temperature, plasma density, and laser spot size. Furthermore, the effect of the upward plasma density ramp profile on the thermal self-focusing is studied. Results show that by using the plasma density ramp-up, the upper-limit intensity increases and the self-focusing temperature range expands.
Possibility of giant enhancement of low-frequency non-resonant Rayleigh scattering by atomic systems within dense plasmas
Authors: Basu Joyee , Ray Debasis
Published: March 2014

In this paper, we demonstrate the possibility of electron density-induced giant growth of non-resonant Rayleigh scattering of electromagnetic radiation (in the low-frequency limit) by atomic systems within dense plasmas. Non-relativistic quantum mechanical calculation is performed under electric dipole approximation, for elastic scattering of radiation by the ground states 1s of plasma-embedded hydrogen-like atomic ions treated within the framework of the ion-sphere model. The results indicate giant enhancement of the non-resonant (photon frequency ω being much smaller than the lowest resonance frequency ω1s−2p) Rayleigh cross-section by an order of magnitude, at (atomic system-specific) high enough plasma electron densities under present consideration. The Z−8-scaling of the non-resonant Rayleigh cross-section in free and isolated H-isoelectronic sequence of ions is shown to be broken in dense plasma environments.
Origin of additional spectral features in modulated reflectance spectra of 2-dimensional semiconductor systems
Authors: Mukherjee Amlan , Ghosh Sandip
Published: March 2014

High resolution photoreflectance (PR) spectroscopy study on a single GaAs/AlGaAs quantum well representing a two-dimensional (2D) system, shows additional distinct spectral features on the high energy side of the first confined heavy-hole and light-hole exciton transitions. The PR experiments involved a special dual detection technique which significantly improved the measurement sensitivity. Photoluminescence excitation spectroscopy data on the sample showed broadened step-like features around these energies. A detailed lineshape analysis, including first principles simulations, was performed to understand the origins of these additional PR spectral features. They are shown to arise primarily from inhomogeneously broadened first excited state transition of the excitons, rather than from a change in the joint density of states at the exciton continuum edge. The analysis suggests that such features are more likely in the case of 2D excitons as compared to 3D excitons in bulk material. Apart from its significance for post-growth characterization, identification of these additional PR features enables direct estimation of the exciton binding energy.
Physical characteristics and cation distribution of NiFe2O4 thin films with high resistivity prepared by reactive co-sputtering
Authors: Klewe C. , Meinert M. , Boehnke A. , Kuepper K. , Arenholz E. , Gupta A. , Schmalhorst J.-M. , Kuschel T. , Reiss G.
Published: March 2014

We fabricated NiFe2O4 thin films on MgAl2O4 (001) substrates by reactive dc magnetron co-sputtering in a pure oxygen atmosphere at different substrate temperatures. The film properties were investigated by various techniques with a focus on their structure, surface topography, magnetic characteristics, and transport properties. Structural analysis revealed a good crystallization with epitaxial growth and low roughness and a similar quality as in films grown by pulsed laser deposition. Electrical conductivity measurements showed high room temperature resistivity (12 Ω m), but low activation energy, indicating an extrinsic transport mechanism. A band gap of about 1.55 eV was found by optical spectroscopy. Detailed x-ray spectroscopy studies confirmed the samples to be ferrimagnetic with fully compensated Fe moments. By comparison with multiplet calculations of the spectra, we found that the cation valencies are to a large extent Ni2+ and Fe3+.
Spatiotemporal flow instabilities of wormlike micellar solutions in rectangular microchannels
Authors: Haward S. J. , Galindo-Rosales F. J. , Ballesta P. , Alves M. A.
Published: March 2014

Flow velocimetry measurements are made on a non-shear-banding wormlike micellar solution within high-aspect-ratio rectilinear microchannels over a wide range of imposed steady flow rates. At the lowest and highest flow rates tested, Newtonian-like velocity profiles are measured. However, at intermediate flow rates the velocity field never stabilizes on the timescale of the experiments (up to several hours). Here, spatiotemporally dependent “jets” of high velocity fluid are observed to fluctuate within regions of essentially stagnant fluid. The reason for this flow instability remains undetermined, but it has significant consequences for many industrial applications and also for microfluidic rheometry of complex fluids.
Self-shielding of a plasma-exposed surface during extreme transient heat loads
Authors: Zielinski J. J. , van der Meiden H. J. , Morgan T. W. , 't Hoen M. H. J. , Schram D. C. , De Temmerman G.
Published: March 2014

The power deposition on a tungsten surface exposed to combined pulsed/continuous high power plasma is studied. A study of the correlation between the plasma parameters and the power deposition on the surface demonstrates the effect of particle recycling in the strongly coupled regime. Upon increasing the input power to the plasma source, the energy density to the target first increases then decreases. We suggest that the sudden outgassing of hydrogen particles from the target and their subsequent ionization causes this. This back-flow of neutrals impedes the power transfer to the target, providing a shielding of the metal surface from the intense plasma flux.
Modelling of monovacancy diffusion in W over wide temperature range
Authors: Bukonte L. , Ahlgren T. , Heinola K.
Published: March 2014

The diffusion of monovacancies in tungsten is studied computationally over a wide temperature range from 1300 K until the melting point of the material. Our modelling is based on Molecular Dynamics technique and Density Functional Theory. The monovacancy migration barriers are calculated using nudged elastic band method for nearest and next-nearest neighbour monovacancy jumps. The diffusion pre-exponential factor for monovacancy diffusion is found to be two to three orders of magnitude higher than commonly used in computational studies, resulting in attempt frequency of the order 1015 Hz. Multiple nearest neighbour jumps of monovacancy are found to play an important role in the contribution to the total diffusion coefficient, especially at temperatures above 2/3 of Tm, resulting in an upward curvature of the Arrhenius diagram. The probabilities for different nearest neighbour jumps for monovacancy in W are calculated at different temperatures.
Field-effect BaTiO3-Si solar cells
Authors: Wang Wentao , Liu Fude , Man Lau Chor , Wang Lei , Yang Guandong , Zheng Dawei , Li Zhigang
Published: March 2014

Conventional solar cells make use of the spatial variation in electronic environment due to junctions for charge separation. We investigated field-effect BaTiO3-Si solar cells that utilize the bound surface charges of BaTiO3 to separate charge carriers in silicon. Rectifying behavior and photovoltaic effect were observed on cells with forward polarization. Theoretical simulation indicated that the induced electric field due to BaTiO3 polarization could extend into the silicon layer, which is consistent with experimental observations. In addition, adjusting relevant parameters may optimize the electric field distribution. The cells are promising in terms of material selection, device design, and fabrication.
Symmetry breaking and geometric confinement in VO2: Results from a three-dimensional infrared nano-imaging
Authors: Liu Mengkun , Wagner Martin , Zhang Jingdi , McLeod Alexander , Kittiwatanakul Salinporn , Fei Zhe , Abreu Elsa , Goldflam Michael , Sternbach Aaron J. , Dai Siyuan , West Kevin G. , Lu Jiwei , Wolf Stuart A. , Averitt Richard D. , Basov D. N.
Published: March 2014

Epitaxial strain can play an important role in controlling the local phase dynamics of transition metal oxides. With scattering-type scanning near-field optical microscopy, we visualize the three dimensional landscape of phase inhomogeneity in strained VO2 films grown on [100]R TiO2 substrates. We demonstrate that three different symmetries are spontaneously broken in the vicinity of the VO2 phase transition: (1) Monoclinic-tetragonal (rutile) crystal symmetry breaking due to the structural phase transition, (2) in-plane (x-y plane) rotational symmetry breaking due to the formation of periodic strain domains, and (3) out-of-plane (z-axis) mirror symmetry breaking at the film cross-section due to substrate-induced epitaxial strain.
Importance of ion bombardment during coverage of Au nanoparticles on their structural features and optical response
Authors: Resta V. , Peláez R. J. , Afonso C. N.
Published: March 2014

This work studies the changes in the optical response and morphological features of 6 ± 1 nm diameter Au nanoparticles (NPs) when covered by a layer of a-Al2O3 by pulsed laser deposition (PLD). The laser fluence used for ablating the Al2O3 target is varied in order to modify the kinetic energy (KE) of the species bombarding the NPs during their coverage. When the ion KE < 200 eV, the structural features and optical properties of the NPs are close to those of uncovered ones. Otherwise, a shift to the blue and a strong damping of the surface plasmon resonance is observed as fluence is increased. There are two processes responsible for these changes, both related to aluminum ions arriving to the substrate during the coverage process, i.e., sputtering of the metal and implantation of aluminum species in the metal. Both processes have been simulated using standard models for ion bombardment, the calculated effective implanted depths allow explaining the observed changes in the optical response, and the use of a size-dependent sputtering coefficient for the Au NPs predicts the experimental sputtering fractions. In spite of the work is based on PLD, the concepts investigated and conclusions can straightforwardly be extrapolated to other physical vapor deposition techniques or processes involving ion bombardment of metal NPs by ions having KE > 200 eV.
Superconducting tantalum nitride-based normal metal-insulator-superconductor tunnel junctions
Authors: Chaudhuri S. , Maasilta I. J.
Published: March 2014

We report the development of superconducting tantalum nitride (TaNx) normal metal-insulator-superconductor (NIS) tunnel junctions. For the insulating barrier, we used both AlOx and TaOx (Cu-AlOx-Al-TaNx and Cu-TaOx-TaNx), with both devices exhibiting temperature dependent current-voltage characteristics which follow the simple one-particle tunneling model. The superconducting gap follows a BCS type temperature dependence, rendering these devices suitable for sensitive thermometry and bolometry from the superconducting transition temperature TC of the TaNx film at ∼5 K down to ∼0.5 K. Numerical simulations were also performed to predict how junction parameters should be tuned to achieve electronic cooling at temperatures above 1 K.
1.7 Gbit/in.2 gray-scale continuous-phase-change femtosecond image storage
Authors: Wang Q. , Maddock J. , Rogers E. T. F. , Roy T. , Craig C. , Macdonald K. F. , Hewak D. W. , Zheludev N. I.
Published: March 2014

We demonstrate high-density, multi-level crystallization of a Ge2Sb2Te5 thin film using tightly focused femtosecond laser pulses. The submicron spots with 8 distinct data storage states are written on a 1.08 μm square grid. The significant change in reflectivity of every specific state of crystallized spot allows easy optical reading and identification. As a demonstration, two gray-scale images are written into the storage medium. Our results open up potential applications in ultra-fast two-dimensional parallel cognitive computing and holography.
Fresnel reflection from a cavity with net roundtrip gain
Authors: Mansuripur Tobias S. , Mansuripur Masud
Published: March 2014

A planewave incident on an active etalon with net roundtrip gain may be expected to diverge in field amplitude, yet applying the Fresnel formalism to Maxwell's equations admits a convergent solution. We describe this solution mathematically and provide additional insight by demonstrating the response of such a cavity to an incident beam of light. Cavities with net roundtrip gain have often been overlooked in the literature, and a clear understanding of their behavior yields insight to negative refraction in nonmagnetic media, a duality between loss and gain, amplified total internal reflection, and the negative-index lens.
Melanin as an active layer in biosensors
Authors: Piacenti da Silva Marina , Fernandes Jéssica Colnaghi , de Figueiredo Natália Biziak , Congiu Mirko , Mulato Marcelo , de Oliveira Graeff Carlos Frederico
Published: March 2014

The development of pH sensors is of great interest due to its extensive application in several areas such as industrial processes, biochemistry and particularly medical diagnostics. In this study, the pH sensing properties of an extended gate field effect transistor (EGFET) based on melanin thin films as active layer are investigated and the physical mechanisms related to the device operation are discussed. Thin films were produced from different melanin precursors on indium tin oxide (ITO) and gold substrates and were investigated by Atomic Force Microscopy and Electrochemical Impedance Spectroscopy. Experiments were performed in the pH range from 2 to 12. EGFETs with melanin deposited on ITO and on gold substrates showed sensitivities ranging from 31.3 mV/pH to 48.9 mV/pH, depending on the melanin precursor and the substrate used. The pH detection is associated with specific binding sites in its structure, hydroxyl groups and quinone imine.
Mechanism of the reset process in bipolar-resistance-switching Ta/TaOx/Pt capacitors based on observation of the capacitance and resistance
Authors: Na Sang-Chul , Kim Jae-Jun , Chul Chun Min , Hee Jin Da , Ahn Seung-Eon , Soo Kang Bo
Published: March 2014

The capacitance (C) and the resistance (R) were measured at various states as the reset process progressed in bipolar-resistance-switching Ta/TaOx/Pt thin film capacitors. The reset process was found to undergo three sequential stages where C and R showed different behavior: increasing C and constant R before an abrupt reset transition, the rapid increase of both C and R upon transition, and saturated C thereafter. These behaviors can be explained in terms of the annihilation of the oxygen vacancies followed by rupture of the conducting channels.
Enhanced sensitivity of piezoelectric pressure sensor with microstructured polydimethylsiloxane layer
Authors: Choi Wook , Lee Junwoo , Kyoung Yoo Yong , Kang Sungchul , Kim Jinseok , Hoon Lee Jeong
Published: March 2014

Highly sensitive detection tools that measure pressure and force are essential in palpation as well as real-time pressure monitoring in biomedical applications. So far, measurement has mainly been done by force sensing resistors and field effect transistor (FET) sensors for monitoring biological pressure and force sensing. We report a pressure sensor by the combination of a piezoelectric sensor layer integrated with a microstructured Polydimethylsiloxane (μ-PDMS) layer. We propose an enhanced sensing tool to be used for analyzing gentle touches without the external voltage source that is used in FET sensors, by incorporating a microstructured PDMS layer in a piezoelectric sensor. By measuring the directly induced electrical charge from the microstructure-enhanced piezoelectric signal, we observed a 3-fold increased sensitivity in a signal response. Both fast signal relaxation from force removal and wide dynamic range from 0.23 to 10 kPa illustrate the good feasibility of the thin film piezoelectric sensor for mimicking human skin.
Students’ experiences of school suspension
Authors: Quin Daniel , Hemphill Sheryl A.
Published: March 2014

Issue addressed

School inclusion and academic attainment are key social determinants of health. Students who have been suspended from school are more likely to disengage from school and consequently not receive the health promoting benefits of social inclusion and academic achievement. This study sought to explore the experiences of students who have been previously suspended (i.e. had experienced school exclusion).

Methods

Seventy‐four previously suspended adolescents from five schools in the state of Victoria, Australia, completed a written questionnaire. Students reported their understanding of the process of being suspended; what they did and with whom they spent the day(s) of suspension; and their perceptions of their return to school post‐suspension.

Results

While suspended, a minority of suspended students received adult supervision and most suspended students participated in benign leisure activities. Upon return to school, students reported diminished teacher assistance and found that suspension did not help resolve the underlying issues that lead to the suspension.

Conclusions

Removal of a student displaying problem behaviours from the classroom may provide temporary relief to the school community but suspended students report minimal benefits from suspension. Suspension removes the potential pro‐social normative influences of school and provides an opportunity to establish antisocial peer networks. Suspended students appear to perceive a stigma upon their return to school, further diminishing an already tenuous school relationship.

So what?

School suspension exposes disadvantaged students to several negative social determinants of health. Students displaying problem behaviours would benefit from interventions that maintain the student's relationship with school. Should suspension be necessary, schools could assist by ensuring that suspended students receive appropriate adult supervision and a formal reintegration to school to promote social inclusion and academic attainment, two recognised key determinants of health.
α-Catenin is an inhibitor of transcription
Authors: Daugherty Rebecca L. , Serebryannyy Leonid , Yemelyanov Alex , Flozak Annette S. , Yu Hui-Jun , Kosak Steven T. , deLanerolle Primal , Gottardi Cara J.
Published: March 2014

Significance

Recent studies have shown that actin-binding and -regulating proteins, originally characterized in the context of cytoskeletal events, can also modify gene expression through directly impacting actin-dependent transcription. This study shows α-catenin (α-cat), an actin-binding protein that is essential for cell–cell adhesion and contact-dependent growth inhibition, can antagonize Wnt/β-catenin–mediated transcription and impact nuclear actin properties, suggesting that these events may be related. These findings establish α-cat as one of a growing list of actin-binding proteins that can modulate transcription, possibly by controlling actin dynamics in the nucleus.
Cell-type–based model explaining coexpression patterns of genes in the brain
Authors: Grange Pascal , Bohland Jason W. , Okaty Benjamin W. , Sugino Ken , Bokil Hemant , Nelson Sacha B. , Ng Lydia , Hawrylycz Michael , Mitra Partha P.
Published: March 2014

Significance

Neuroanatomy is experiencing a renaissance due to the study of gene-expression data covering the entire mouse brain and the entire genome that have been recently released (the Allen Atlas). On the other hand, some cell types extracted from the mouse brain have been characterized by their genetic activity. However, given a cell type, it is not known in which brain regions it can be found. We propose a computational model using the Allen Atlas to solve this problem, thus estimating previously unidentified cell-type–specific maps of the mouse brain. The model can be used to define brain regions through genetic data.
Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence
Authors: Guanter Luis , Zhang Yongguang , Jung Martin , Joiner Joanna , Voigt Maximilian , Berry Joseph A. , Frankenberg Christian , Huete Alfredo R. , Zarco-Tejada Pablo , Lee Jung-Eun , Moran M. Susan , Ponce-Campos Guillermo , Beer Christian , Camps-Valls Gustavo , Buchmann Nina , Gianelle Damiano , Klumpp Katja , Cescatti Alessandro , Baker John M. , Griffis Timothy J.
Published: March 2014

Significance

Global food and biofuel production and their vulnerability in a changing climate are of paramount societal importance. However, current global model predictions of crop photosynthesis are highly uncertain. Here we demonstrate that new space-based observations of chlorophyll fluorescence, an emission intrinsically linked to plant biochemistry, enable an accurate, global, and time-resolved measurement of crop photosynthesis, which is not possible from any other remote vegetation measurement. Our results show that chlorophyll fluorescence data can be used as a unique benchmark to improve our global models, thus providing more reliable projections of agricultural productivity and climate impact on crop yields. The enormous increase of the observational capabilities for fluorescence in the very near future strengthens the relevance of this study.
Integrated strategy reveals the protein interface between cancer targets Bcl-2 and NAF-1
Authors: Tamir Sagi , Rotem-Bamberger Shahar , Katz Chen , Morcos Faruck , Hailey Kendra L. , Zuris John A. , Wang Charles , Conlan Andrea R. , Lipper Colin H. , Paddock Mark L. , Mittler Ron , Onuchic José N. , Jennings Patricia A. , Friedler Assaf , Nechushtai Rachel
Published: March 2014

Significance

Misregulation of cell growth and proliferation leads to the onset of various diseases, including cancer. Two proteins crucial for proper cellular control that were recently shown to affect cellular proliferation are Bcl-2, well-known for its role in programmed cell death, and the newly identified iron-sulfur protein NAF-1, localized near the mitochondrial outer membrane. In this report, we use a strategy utilizing a combination of experimental and computational techniques that provides valuable information to enable us to determine a molecular picture of the NAF-1–Bcl-2 interaction interface that is more complete than that obtained from any one technique alone. This interaction interface provides the basis from which novel drugs can be developed for the treatment of diseases such as cancer.
Medicago truncatula
symbiotic peptide NCR247 contributes to bacteroid differentiation through multiple mechanisms
Authors: Farkas Attila , Maróti Gergely , Dürgő Hajnalka , Györgypál Zoltán , Lima Rui M. , Medzihradszky Katalin F. , Kereszt Attila , Mergaert Peter , Kondorosi Éva
Published: March 2014

Significance

Intracellular endosymbiotic bacteria in diverse symbiotic systems are under the control of host-derived symbiosis-specific peptides. These peptides have mostly unknown activities. In the facultative rhizobium-legume symbiosis, the bacteria differentiate in many legumes to large polyploid noncultivable bacteroids. This terminal differentiation is achieved by concerted actions of hundreds of nodule-specific cysteine-rich (NCR) peptides. Although in vitro antimicrobial activities were demonstrated for a few NCR peptides, their mode of action
in planta
remained unexplored. Our work reveals a complex interaction network of NCR247, which affects bacterial cell division machinery, translation, and protein folding. These findings give an insight how the host can modulate the physiology of the endosymbionts and may serve as a paradigm for other symbiotic systems.
When does relational information influence evaluative conditioning?
Authors: Zanon Riccardo , De Houwer Jan , Gast Anne , Smith Colin Tucker
Published: March 2014

Building on the intriguing findings of Peters and Gawronski (2011, Experiment 3), we examined the conditions under which relational information (i.e., information about how two stimuli are related) moderates evaluative conditioning (EC; i.e., the effect of stimulus pairing on liking). In Experiment 1, participants saw stimulus pairs that consisted of a novel nonword (conditioned stimulus; CS) and a known positive or negative word (unconditioned stimulus; US). Before or after the pairings, participants were told that the nonword had the opposite meaning to the word with which it was paired. Subsequent measures of the implicit evaluation of the nonwords revealed that nonwords paired with positive words were liked less than nonwords paired with negative words, but only when the relational information was presented before the CS–US pairings. In a second experiment, participants were first informed that the CS and US of each pair were related in one way (e.g., that they have the same meaning). Afterwards, this information was either confirmed (e.g., that they indeed have the same meaning) or reversed (e.g., that they actually have an opposite meaning). Whereas the first relational information had more impact on implicit evaluations than on explicit evaluations, the reverse was true for the second relational information. Moreover, informing participants that CS and US were equivalent produced the same effects as pairing CS and US without providing explicit relational information, thus suggesting that the mere co-occurrence of CS and US is treated as a cue for equivalence of CS and US. Implications for mental process models of EC are discussed.
Occupy Dame Street as slow-motion general strike? Justifying optimism in the wake of Ireland’s failed multitudinal moment
Authors: Kiersey Nicholas
Published: March 2014

Discussing their hopes for a horizontalist mode of politics, Hardt and Negri envision a grand, kairotic event that will announce the ‘becoming prince’ of the multitude. This article reflects on this idea in light of the strategies and discourses of Ireland's Occupy Dame Street (ODS) activists. Starting with a brief account of the rise and fall of the ODS movement, as it struggled to engage the political imagination of a nation beset by financial crisis, the article explores the extent to which the actions of the movement conformed to ‘multitudinal ideals.’ It suggests that, in a way, and quite unconsciously, dominant factions in the movement came to embrace a kind of ‘event politics’ of their own – a turn which posed a barrier to the movement's success, in a way with which occupy movements elsewhere simply did not have to contend. Taking this story as an opportunity to reflect on the place of the event in Hardt and Negri's work, the article then discusses two alternative approaches to horizontal politics. Turning first to Eugene Holland's concept of the Slow-Motion General Strike, we find a more experimental and piecemeal approach to social transformation. This approach, it is concluded, has the virtue of retaining Hardt and Negri's enthusiastic rejection of hegemonic thinking while avoiding becoming caught up in a debate over the relative merits of passively waiting for a constitutive event over reform or revolution. That said, in Ireland at least, there is a certain danger that a ‘chronological’ approach can cede too much, especially in a time of general neoliberal expropriation of public space. With this urgency in mind, a second position is staked out. While in some ways reasserting the importance of kairotic time, this position borrows from anarchist understandings of public space, and puts a strong focus on tactics. As the article concludes, the actions of ODS-affiliated activists to expose the blatantly undemocratic operations of the country’s National Asset Management Agency by occupying vacant commercial properties in Dublin suggest a continuing relevance for direct-action tactics in Irish public space.
Trans-dimerization of JAM-A regulates Rap2 and is mediated by a domain that is distinct from thecis-dimerization interface
Authors: Monteiro Ana C. , Luissint Anny-Claude , Sumagin Ronen , Lai Caroline , Vielmuth Franziska , Wolf Mattie F. , Laur Oskar , Reiss Kerstin , Spindler Volker , Stehle Thilo , Dermody Terence S. , Nusrat Asma , Parkos Charles A.
Published: March 2014

Junctional adhesion molecule-A (JAM-A) is a tight junction–associated signaling protein that regulates epithelial cell proliferation, migration, and barrier function. JAM-A dimerization on a common cell surface (in cis) has been shown to regulate cell migration, and evidence suggests that JAM-A may form homodimers between cells (in trans). Indeed, transfection experiments revealed accumulation of JAM-A at sites between transfected cells, which was lost in cells expressing cis- or predicted trans-dimerization null mutants. Of importance, microspheres coated with JAM-A containing alanine substitutions to residues 43NNP45 (NNP-JAM-A) within the predicted trans-dimerization site did not aggregate. In contrast, beads coated with cis-null JAM-A demonstrated enhanced clustering similar to that observed with wild-type (WT) JAM-A. In addition, atomic force microscopy revealed decreased association forces in NNP-JAM-A compared with WT and cis-null JAM-A. Assessment of effects of JAM-A dimerization on cell signaling revealed that expression of trans- but not cis-null JAM-A mutants decreased Rap2 activity. Furthermore, confluent cells, which enable trans-dimerization, had enhanced Rap2 activity. Taken together, these results suggest that trans-dimerization of JAM-A occurs at a unique site and with different affinity compared with dimerization in cis. Trans-dimerization of JAM-A may thus act as a barrier-inducing molecular switch that is activated when cells become confluent.
LMTK1 regulates dendritic formation by regulating movement of Rab11A-positive endosomes
Authors: Takano Tetsuya , Urushibara Tomoki , Yoshioka Nozomu , Saito Taro , Fukuda Mitsunori , Tomomura Mineko , Hisanaga Shin-ichi
Published: March 2014

Neurons extend two types of neurites—axons and dendrites—that differ in structure and function. Although it is well understood that the cytoskeleton plays a pivotal role in neurite differentiation and extension, the mechanisms by which membrane components are supplied to growing axons or dendrites is largely unknown. We previously reported that the membrane supply to axons is regulated by lemur kinase 1 (LMTK1) through Rab11A-positive endosomes. Here we investigate the role of LMTK1 in dendrite formation. Down-regulation of LMTK1 increases dendrite growth and branching of cerebral cortical neurons in vitro and in vivo. LMTK1 knockout significantly enhances the prevalence, velocity, and run length of anterograde movement of Rab11A-positive endosomes to levels similar to those expressing constitutively active Rab11A-Q70L. Rab11A-positive endosome dynamics also increases in the cell body and growth cone of LMTK1-deficient neurons. Moreover, a nonphosphorylatable LMTK1 mutant (Ser34Ala, a Cdk5 phosphorylation site) dramatically promotes dendrite growth. Thus LMTK1 negatively controls dendritic formation by regulating Rab11A-positive endosomal trafficking in a Cdk5-dependent manner, indicating the Cdk5-LMTK1-Rab11A pathway as a regulatory mechanism of dendrite development as well as axon outgrowth.
Is Diet Quality Improving? Distributional Changes in the United States, 1989–2008
Authors: Beatty Timothy K. M. , Lin Biing-Hwan , Smith Travis A.
Published: March 2014

This article measures changes in the distribution of dietary quality among adults in the United States over the period 1989–2008. Diet quality is a direct input to health, is often used as a proxy for well‐being, and is an outcome variable for a wide variety of economic interventions. For the population as a whole, we find significant improvements across all levels of diet quality. Further, we find improvements for both low‐income and higher‐income individuals alike. Counterfactual distributions of dietary quality are constructed to investigate the extent to which observed improvements can be attributed to changes in the nutritional content of foods and to changes in population characteristics. We find that 63% of the improvement for all adults can be attributed to changes in food formulation and demographics. Changes in food formulation account for a substantially larger percentage of the dietary improvement within the lower‐income population (19.6%) vs. the higher‐income population (6.4%).
Short- and long-term effects of litter size manipulation in a small wild-derived rodent
Authors: Lehto Hürlimann Mikko , Stier Antoine , Scholly Olivier , Criscuolo François , Bize Pierre
Published: March 2014

Iteroparous organisms maximize their overall fitness by optimizing their reproductive effort over multiple reproductive events. Hence, changes in reproductive effort are expected to have both short- and long-term consequences on parents and their offspring. In laboratory rodents, manipulation of reproductive efforts during lactation has however revealed few short-term reproductive adjustments, suggesting that female laboratory rodents express maximal rather than optimal levels of reproductive investment as observed in semelparous organisms. Using a litter size manipulation (LSM) experiment in a small wild-derived rodent (the common vole;Microtus arvalis), we show that females altered their reproductive efforts in response to LSM, with females having higher metabolic rates and showing alternative body mass dynamics when rearing an enlarged rather than reduced litter. Those differences in female reproductive effort were nonetheless insufficient to fully match their pups’ energy demand, pups being lighter at weaning in enlarged litters. Interestingly, female reproductive effort changes had long-term consequences, with females that had previously reared an enlarged litter being lighter at the birth of their subsequent litter and producing lower quality pups. We discuss the significance of using wild-derived animals in studies of reproductive effort optimization.
Alternative radical pairs for cryptochrome-based magnetoreception
Authors: Lee Alpha A. , Lau Jason C. S. , Hogben Hannah J. , Biskup Till , Kattnig Daniel R. , Hore P. J.
Published: March 2014

There is growing evidence that the remarkable ability of animals, in particular birds, to sense the direction of the Earth's magnetic field relies on magnetically sensitive photochemical reactions of the protein cryptochrome. It is generally assumed that the magnetic field acts on the radical pair [FAD

•−

TrpH

•

+
] formed by the transfer of an electron from a group of three tryptophan residues to the photo-excited flavin adenine dinucleotide cofactor within the protein. Here, we examine the suitability of an [FAD

•−

Z

•

] radical pair as a compass magnetoreceptor, where Z

•

is a radical in which the electron spin has no hyperfine interactions with magnetic nuclei, such as hydrogen and nitrogen. Quantum spin dynamics simulations of the reactivity of [FAD

•−

Z

•

] show that it is two orders of magnitude more sensitive to the direction of the geomagnetic field than is [FAD

•−

TrpH

•

+
] under the same conditions (50 µT magnetic field, 1 µs radical lifetime). The favourable magnetic properties of [FAD

•−

Z

•

] arise from the asymmetric distribution of hyperfine interactions among the two radicals and the near-optimal magnetic properties of the flavin radical. We close by discussing the identity of Z

•

and possible routes for its formation as part of a spin-correlated radical pair with an FAD radical in cryptochrome.