bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the light-induced electron-transfer-coupled spin transition in a cyanide-bridged [Co2Fe2] complex by X-ray diffraction and absorption measurements
Authors: Sekine Yoshihiro , Nihei Masayuki , Kumai Reiji , Nakao Hironori , Murakami Youichi , Oshio Hiroki
Published: June 2014

The light-induced electron-transfer-coupled spin transition in a cyanide-bridged [Co2Fe2] tetranuclear complex has been investigated by single-crystal X-ray diffraction and absorption measurements.
An analytical approach for the energy spectrum and optical properties of gated bilayer graphene
Authors: Chang Cheng-Peng
Published: June 2014

An analytical approach is developed to access the exact energy spectrum, wave functions, dipole matrix element (Mfi) and absorption spectra (A(ω)) of gated Bernal bilayer graphene.
K3MoPO7: the first molybdenum phosphate with edge-sharing MoO6octahedra and PO4tetrahedra
Authors: Luo Siyang , Kang Lei , Lin Zheshuai , Chen Chuangtian
Published: June 2014

The unique edge-sharing MoO6and PO4polyhedra were first discovered in a novel molybdenum phosphate K3MoPO7.
A combined stochastic search and density functional theory study on the neutral and charged silicon-based clusters MSi6 (M = La, Ce, Yb and Lu)
Authors: Wang Huai-Qian , Li Hui-Fang
Published: June 2014

Structures and simulated photoelectron spectra of MSi6− (M = La, Ce, Yb and Lu).
Chemistry education research trends: 2004–2013
Authors: Teo Tang Wee , Goh Mei Ting , Yeo Leck Wee
Published: June 2014

This paper presents findings from a content analysis of 650 empirical chemistry education research papers published in two top-tiered chemistry education journals Chemistry Education Research and Practice and Journal of Chemical Education, and four top-tiered science education journals International Journal of Science Education, Journal of Research in Science Teaching, Research in Science Teaching and Science Education from 2004–2013. We found that empirical chemistry education research (CER) papers accounted for 7.7 percent of the publications in the four science education journals. The most highly published area of research was in conceptions and conceptual change and most studies adopted mixed methods. The majority of the studies were conducted in higher education contexts and in the United States. Researchers who publish prolifically in the field included Vicente Talanquer, Derek Cheung, Michael Sanger, Keith Taber, Melanie Cooper and Marcy Towns. Current research trends and gaps are illuminated and possible future work in CER is discussed in the paper.
Mixtures of latex particles and the surfactant of opposite charge used as interface stabilizers – influence of particle contact angle, zeta potential, flocculation and shear energy
Authors: Deleurence Rémi , Parneix Caroline , Monteux Cécile
Published: June 2014

Using mixtures of latex and surfactant of opposite charges we decouple the effect of the charge and contact angle of the particles on the interface stabilization. We find that the key-parameters are the flocculation state of the particles and the shear energy used to produce the foams.
A simple material model to generate epidermal and dermal layers in vitro for skin regeneration
Authors: Tsao Ching-Ting , Leung Matthew , Yu-Fong Chang Julia , Zhang Miqin
Published: June 2014

A porous composite scaffold permeated with a chitosan–poly(ethylene glycol) gel, which mimics the bi-layered micro-environment of skin, promotes keratinocyte proliferation and maturation.
Exploiting the use of information to improve coverage performance of robotic sensor networks
Authors: Gusrialdi Azwirman , Yu Changbin
Published: June 2014

A robotic sensor network is advantageous in performing a coverage task compared to the static sensor network because of its ability to self‐deploy and self‐reconfigure. However, since the sensor has a limited sensing range, when mobile sensors are initially deployed, sensors located far away from the region of interest may not be able to self‐deploy themselves, that is, participate in the coverage task. This results in a degradation of coverage performance by the robotic network. This paper proposes a novel algorithm in order to improve the coverage performance by the whole mobile sensor network by guaranteeing the participation of all sensors in the coverage task. The algorithm is a combination of the standard gradient‐based coverage algorithm and a leader‐following algorithm and is designed to maximise the joint detection probabilities of the events in the region of interest. As a strategy, first a set of leader sensors are selected based on the information which each sensor has gathered. The rest of the sensors will follow their leaders until they have sufficient information on the region of interest and then switch to the standard coverage algorithm. The proposed algorithm can be performed in a distributed manner. The results are validated through several numerical simulations.
Efficient method for spaceborne synthetic aperture radar (SAR) geolocation and application to geometrical SAR image registration
Authors: Li Jin‐wei , Li Zhen‐fang , Hou Ying‐Long , Bao Zheng
Published: June 2014

An efficient method for spaceborne synthetic aperture radar (SAR) geolocation is devised in this study. In this method, the pixels in the SAR image are divided into two types by a two‐dimensional (2D) grid, that is, grid pixels and non‐grid pixels. The approach of finding the position of a non‐grid pixel is to add the position of the adjacent grid pixel and the position increment between the two pixels together, where the position increment is computed by means of three groups of increment formulae derived according to the principle of first‐order Taylor approximation. It is noticed that this method is efficient and helpful in improving the efficiency of the geometrical SAR image registration for avoiding the polynomial fitting and interpolation. In the geometrical registration, the 2D shifts of a non‐grid pixel can be expressed as the sum of shifts of the adjacent grid pixel and shift increments between the two pixels. Here the position and 2D shifts of the grid pixel are obtained through the numerical methods for a complete lack of closed‐form solutions. Finally, the experiments with TerraSAR‐X images are conducted to evaluate the effectiveness of the proposed method.
Kinetics of ion-ion mutual neutralization: Halide anions with polyatomic cations
Authors: Shuman Nicholas S. , Wiens Justin P. , Miller Thomas M. , Viggiano Albert A.
Published: June 2014

The binary mutual neutralization (MN) of a series of 17 cations (${\rm O}_2 ^ +$O2+, NO+, ${\rm NO}_2 ^ +$ NO 2+, CO+, ${\rm CO}_2 ^ +$ CO 2+, Cl+, ${\rm Cl}_2 ^ +$ Cl 2+, ${\rm SO}_2 ^ +$ SO 2+, ${\rm CF}_3 ^ +$ CF 3+, ${\rm C}_2 {\rm F}_5 ^ +$C2F5+, ${\rm NH}_3 ^ +$ NH 3+, ${\rm H}_3 ^ +$H3+, ${\rm D}_3 ^ +$D3+, H2O+, H3O+, ArH+, ArD+) with 3 halide anions (Cl−, Br−, I−) has been investigated in a flowing afterglow-Langmuir probe apparatus using the variable electron and neutral density attachment mass spectrometry technique. The MN rate constants of atom-atom reactions are dominated by the chemical nature of the system (i.e., the specific locations of curve crossings). As the number of atoms in the system increases, the MN rate constants become dominated instead by the physical nature of the system (e.g., the relative velocity of the reactants). For systems involving 4 or more atoms, the 300 K MN rate constants are well described by 2.7 × 10−7 μ−0.5, where the reduced mass is in Da and the resulting rate constants in cm3 s−1. An upper limit to the MN rate constants appears well described by the complex potential model described by Hickman assuming a cross-section to neutralization of 11 000 Å2 at 300 K, equivalent to 3.5 × 10−7 μ−0.5.
Identifying the Hamiltonian structure in linear response theory
Authors: List Nanna Holmgaard , Coriani Sonia , Christiansen Ove , Kongsted Jacob
Published: June 2014

We present a unifying framework for linear response eigenvalue equations that encompasses both variational Hartree-Fock and Kohn-Sham density functional theory as well as non-variational coupled-cluster theory. The joint description is rooted in the so-called Hamiltonian structure of the response kernel matrices, whose properties permit an immediate identification of the well-known paired eigenvalue spectrum describing a molecule in the isolated state. Recognizing the Hamiltonian structure underlying the equations further enables a generalization to the case of a polarizable-embedded molecule treated in variational and, in particular, in non-variational theories.
Photoisomerization among ring-open merocyanines. I. Reaction dynamics and wave-packet oscillations induced by tunable femtosecond pulses
Authors: Ruetzel Stefan , Diekmann Meike , Nuernberger Patrick , Walter Christof , Engels Bernd , Brixner Tobias
Published: June 2014

Upon ultraviolet excitation, photochromic spiropyran compounds can be converted by a ring-opening reaction into merocyanine molecules, which in turn can form several isomers differing by cis and trans configurations in the methine bridge. Whereas the spiropyran–merocyanine conversion reaction of the nitro-substituted indolinobenzopyran 6-nitro-1′,3′,3′-trimethylspiro[2H-1-benzopyran-2,2′-indoline] (6-nitro BIPS) has been studied extensively in theory and experiments, little is known about photoisomerization among the merocyanine isomers. In this article, we employ femtosecond transient absorption spectroscopy with variable excitation wavelengths to investigate the excited-state dynamics of the merocyanine in acetonitrile at room temperature, where exclusively the trans-trans-cis (TTC) and trans-trans-trans (TTT) isomers contribute. No photochemical ring-closure pathways exist for the two isomers. Instead, we found that (18±4)% of excited TTC isomers undergo an ultrafast excited-state cis→trans photoisomerization to TTT within 200 fs, while the excited-state lifetime of TTC molecules that do not isomerize is 35 ps. No photoisomerization was detected for the TTT isomer, which relaxes to the ground state with a lifetime of roughly 160 ps. Moreover, signal oscillations at 170 cm−1 and 360 cm−1 were observed, which can be ascribed to excited-state wave-packet dynamics occurring in the course of the TTC→TTT isomerization. The results of high-level time-dependent density functional theory in conjunction with polarizable continuum models are presented in the subsequent article [C. Walter, S. Ruetzel, M. Diekmann, P. Nuernberger, T. Brixner, and B. Engels, J. Chem. Phys. 140, 224311 (2014)].
Measurement procedure for absolute broadband infrared up-conversion photoluminescent quantum yields: Correcting for absorption/re-emission
Authors: MacDougall Sean K. W. , Ivaturi Aruna , Marques-Hueso Jose , Richards Bryce S.
Published: June 2014

The internal photoluminescent quantum yield (iPLQY) – defined as the ratio of emitted photons to those absorbed – is an important parameter in the evaluation and application of luminescent materials. The iPLQY is rarely reported due to the complexities in the calibration of such a measurement. Herein, an experimental method is proposed to correct for re-emission, which leads to an underestimation of the absorption under broadband excitation. Although traditionally the iPLQY is measured using monochromatic sources for linear materials, this advancement is necessary for nonlinear materials with wavelength dependent iPLQY, such as the application of up-conversion to solar energy harvesting. The method requires an additional measurement of the emission line shape that overlaps with the excitation and absorption spectra. Through scaling of the emission spectrum, at the long wavelength edge where an overlap of excitation does not occur, it is possible to better estimate the value of iPLQY. The method has been evaluated for a range of nonlinear material concentrations and under various irradiances to analyze the necessity and boundary conditions that favor the proposed method. Use of this refined method is important for a reliable measurement of iPLQY under a broad illumination source such as the Sun.
Near-field microwave magnetic nanoscopy of superconducting radio frequency cavity materials
Authors: Tai Tamin , Ghamsari Behnood G. , Bieler Thomas R. , Tan Teng , Xi X. X. , Anlage Steven M.
Published: June 2014

A localized measurement of the RF critical field on superconducting radio frequency (SRF) cavity materials is a key step to identify specific defects that produce quenches of SRF cavities. Two measurements are performed to demonstrate these capabilities with a near-field scanning probe microwave microscope. The first is a third harmonic nonlinear measurement on a high Residual-Resistance-Ratio bulk Nb sample showing strong localized nonlinear response, with surface RF magnetic field Bsurface∼102 mT. The second is a raster scanned harmonic response image on a MgB2 thin film demonstrating a uniform nonlinear response over large areas.
Direct growth of graphene on Si(111)
Authors: Thanh Trung Pham , Campos-Delgado Jessica , Joucken Frédéric , Colomer Jean-François , Hackens Benoît , Raskin Jean-Pierre , Santos Cristiane N. , Robert Sporken
Published: June 2014

Due to the need of integrated circuit in the current silicon technology, the formation of graphene on Si wafer is highly desirable, but is still a challenge for the scientific community. In this context, we report the direct growth of graphene on Si(111) wafer under appropriate conditions using an electron beam evaporator. The structural quality of the material is investigated in detail by reflection high energy electron diffraction, Auger electron spectroscopy, X-ray photoemission spectroscopy, Raman spectroscopy, high resolution scanning electron microscopy, atomic force microscopy, and scanning tunneling microscopy. Our experimental results confirm that the quality of graphene is strongly dependent on the growth time during carbon atoms deposition.
Spin transport properties of partially edge-hydrogenated MoS2 nanoribbon heterostructure
Authors: Peng Li , Yao Kailun , Zhu Sicong , Ni Yun , Zu Fengxia , Wang Shuling , Guo Bin , Tian Yong
Published: June 2014

We report ab initio calculations of electronic transport properties of heterostructure based on MoS2 nanoribbons. The heterostructure consists of edge hydrogen-passivated and non-passivated zigzag MoS2 nanoribbons (ZMoS2NR-H/ZMoS2NR). Our calculations show that the heterostructure has half-metallic behavior which is independent of the nanoribbon width. The opening of spin channels of the heterostructure depends on the matching of particular electronic orbitals in the Mo-dominated edges of ZMoS2NR-H and ZMoS2NR. Perfect spin filter effect appears at small bias voltages, and large negative differential resistance and rectifying effects are also observed in the heterostructure.
Point spread function of the optical needle super-oscillatory lens
Authors: Roy Tapashree , Rogers Edward T. F. , Yuan Guanghui , Zheludev Nikolay I.
Published: June 2014

Super-oscillatory optical lenses are known to achieve sub-wavelength focusing. In this paper, we analyse the imaging capabilities of a super-oscillatory lens by studying its point spread function. We experimentally demonstrate that a super-oscillatory lens can generate a point spread function 24% smaller than that dictated by the diffraction limit and has an effective numerical aperture of 1.31 in air. The object-image linear displacement property of these lenses is also investigated.
Radiation induced effects on mechanical properties of nanoporous gold foams
Authors: Caro M. , Mook W. M. , Fu E. G. , Wang Y. Q. , Sheehan C. , Martinez E. , Baldwin J. K. , Caro A.
Published: June 2014

It has recently been shown that due to a high surface-to-volume ratio, nanoporous materials display radiation tolerance. The abundance of surfaces, which are perfect sinks for defects, and the relation between ligament size, defect diffusion, and time combine to define a window of radiation resistance [Fu et al., Appl. Phys. Lett. 101, 191607 (2012)]. Outside this window, the dominant defect created by irradiation in Au nanofoams are stacking fault tetrahedra (SFT). Molecular dynamics computer simulations of nanopillars, taken as the elemental constituent of foams, predict that SFTs act as dislocation sources inducing softening, in contrast to the usual behavior in bulk materials, where defects are obstacles to dislocation motion, producing hardening. In this work we test that prediction and answer the question whether irradiation actually hardens or softens a nanofam. Ne ion irradiations of gold nanofoams were performed at room temperature for a total dose up to 4 dpa, and their mechanical behavior was measured by nanoindentation. We find that hardness increases after irradiation, a result that we analyze in terms of the role of SFTs on the deformation mode of foams.
Reversal modes in small rings: Signature on the susceptibility
Authors: Castillo-Sepúlveda S. , Vargas N. M. , Escobar R. A. , Baltazar S. E. , Allende S. , Altbir D.
Published: June 2014

The magnetization reversal mechanisms of small rings have been investigated as a function of the geometry. Stepped and non stepped hysteresis loops were obtained and four different reversal mechanisms were identified. In spite the important information that is possible to get from the hysteresis loops, in some cases it is not possible to identify from them the reversal mechanisms. However, susceptibility curves deliver enough information to determine precisely the reversal mode, making these curves a valuable tool for the study of the magnetization reversal in rings.
Electrical and optical characterization of Au/CaF2/p-Si(111) tunnel-injection diodes
Authors: Illarionov Yu. Yu. , Vexler M. I. , Fedorov V. V. , Suturin S. M. , Sokolov N. S.
Published: June 2014

Metal/CaF2/p-Si(111) capacitors with the improved-quality several-nanometer-thick epitaxial fluorite films are examined, aiming at solidifying a candidacy of this material for barrier layers in silicon devices. Structural and transport properties of a thin crystalline dielectric are characterized by different experimental techniques. The measured current-voltage characteristics accompanied with simulation results demonstrate that the elastic tunneling electron injection takes place in the considered structures. The same result follows from the behavior of hot-electron-injection-related electroluminescence within the selected spectral intervals. The result is important considering a perspective of using the epitaxial fluorides as barrier layers in resonant tunneling diodes.
Electron transport properties of bis[2-(2-hydroxyphenyl)-pyridine]beryllium investigated by impedance spectroscopy
Authors: Wang Yanping , Chen Jiangshan , Huang Jinying , Ma Dongge , Dong Lisong , Chen Hui
Published: June 2014

The electron transport properties of bis[2-(2-hydroxyphenyl)-pyridine] beryllium (Bepp2) are investigated by impedance spectroscopy over a frequency range of 10 Hz to 13 MHz. The Cole-Cole plots demonstrate that the Bepp2-based device can be represented by a single parallel resistance Rp and capacitance Cp network with a series resistance Rs. The current-voltage characteristics and the variation of Rp with applied bias voltage indicate the electron conduction of space-charge-limited current with exponential trap distributions in Bepp2. It can be seen that the electron mobility exhibits strong field-dependence in low electric field region and almost saturate in high electric field region. It is experimentally found that Bepp2 shows dispersion transport and becomes weak as the electric field increases. The activation energy is determined to be 0.043 eV by temperature-dependent conductivity, which is consistent with the result obtained from the temperature-dependent current density characteristics. The electron mobility reaches the orders of 10−6–10−5 cm2 V−1 s−1, depending on the electric field.
Single beam optical vortex tweezers with tunable orbital angular momentum
Authors: Gecevičius Mindaugas , Drevinskas Rokas , Beresna Martynas , Kazansky Peter G.
Published: June 2014

We propose a single beam method for generating optical vortices with tunable optical angular momentum without altering the intensity distribution. With the initial polarization state varying from linear to circular, we gradually control the torque transferred to the trapped non-absorbing and non-birefringent silica beads. The continuous transition from the maximum rotation speed to zero without changing the trapping potential gives a way to study the complex tribological interactions.
Strong strain rate effect on the plasticity of amorphous silica nanowires
Authors: Yue Yonghai , Zheng Kun
Published: June 2014

With electron-beam (e-beam) off, in-situ tensile experiments on amorphous silica nanowires (NWs) were performed inside a transmission electron microscope (TEM). By controlling the loading rates, the strain rate can be adjusted accurately in a wide range. The result shows a strong strain rate effect on the plasticity of amorphous silica NWs. At lower strain rate, the intrinsic brittle materials exhibit a pronounced elongation higher than 100% to failure with obvious necking near ambient temperature. At the strain rate higher than 5.23 × 10−3/s, the elongation of the NW decreased dramatically, and a brittle fracture feature behavior was revealed. This ductile feature of the amorphous silica NWs has been further confirmed with the in-situ experiments under optical microscopy while the effect of e-beam irradiation could be eliminated.
Soliton propagation in micron-sized magnetic ratchet elements
Authors: Lee J. H. , Petit D. , Lavrijsen R. , Fernández-Pacheco A. , Mansell R. , Cowburn R. P.
Published: June 2014

We demonstrate ratchet soliton propagation in individual patterned antiferromagnetically coupled superlattice elements down to 3 μm diameter using magneto-optical Kerr effect measurements. The bulk switching and soliton propagation fields are investigated as a function of the element size. It is found that on the length scale investigated here we do not see significant variation in ratchet behavior depending on the element size. The margin for soliton propagation and additional features related to downscaling are discussed.
Electrical characteristics and thermal stability of HfO2 metal-oxide-semiconductor capacitors fabricated on clean reconstructed GaSb surfaces
Authors: Miyata Noriyuki , Ohtake Akihiro , Ichikawa Masakazu , Mori Takahiro , Yasuda Tetsuji
Published: June 2014

HfO2/GaSb interfaces fabricated by high-vacuum HfO2 deposition on clean reconstructed GaSb surfaces were examined to explore a thermally stable GaSb metal-oxide-semiconductor structure with low interface-state density (Dit). Interface Sb-O bonds were electrically and thermally unstable, and post-metallization annealing at temperatures higher than 200 °C was required to stabilize the HfO2/GaSb interfaces. However, the annealing led to large Dit in the upper-half band gap. We propose that the decomposition products that are associated with elemental Sb atoms act as interface states, since a clear correlation between the Dit and the Sb coverage on the initial GaSb surfaces was observed.
Stability of polarized states for diamond valleytronics
Authors: Hammersberg J. , Majdi S. , Kovi K. K. , Suntornwipat N. , Gabrysch M. , Twitchen D. J. , Isberg J.
Published: June 2014

The stability of valley polarized electron states is crucial for the development of valleytronics. A long relaxation time of the valley polarization is required to enable operations to be performed on the polarized states. Here, we investigate the stability of valley polarized states in diamond, expressed as relaxation time. We have found that the stability of the states can be extremely long when we consider the electron-phonon scattering processes allowed by symmetry considerations. We determine electron-phonon coupling constants by Time-of-Flight measurements and Monte Carlo simulations and use these data to map out the relaxation time temperature dependency. The relaxation time for diamond can be microseconds or longer below 100 K and 100 V/cm due to the strong covalent bond, which is highly encouraging for future use in valleytronic applications.
Experimental demonstration of an on-chip polarization splitter in a submicron asymmetric dielectric-coated metal slit
Authors: Chen Jianjun , Sun Chengwei , Li Hongyun , Gong Qihuang
Published: June 2014

A submicron asymmetric dielectric-coated metal slit with a Fabry–Perot (FP) nano-resonator is experimentally fabricated to realize an ultra-small on-chip polarization splitter. In the hybrid plasmonic structure, both of the transverse-electric (TE) and transverse-magnetic (TM) modes can be efficiently generated on the front metal surface. Based on the quite different resonant conditions and the different field confinements of the two orthogonal polarization modes in the FP resonator, the TM and TE modes are generated to propagate in the opposite directions along the metal surface. In this device, there are no coupling waveguide regions, and the excitation and the splitting of the TE and TM modes are integrated into the same asymmetric nano-slit. This considerably shrinks the device dimension to only about 850 nm (about one wavelength). In such a submicron asymmetric slit, the measured extinction ratios for the two opposite directions can reach up to (ηL/ηR)TM ≈ 1:14 and (ηL/ηR)TE ≈ 11:1 at λ = 820 nm. This on-chip submicron polarization splitter is of importance in highly integrated photonic circuits.
Efficient simulation of the impact of interface grading on the transport and optical properties of semiconductor heterostructures
Authors: Lü X. , Schrottke L. , Luna E. , Grahn H. T.
Published: June 2014

An efficient model is proposed to evaluate the impact of interface grading on the properties of semiconductor heterostructures. In the plane-wave approximation, the interface grading is taken into account by simply multiplying the Fourier components of the potential by a Gaussian function, which results only in a very small increase of the computation time. We show that the interface grading may affect the transition energies, the field strength for resonant coupling of subbands, and even the miniband formation in complex systems such as quantum-cascade lasers. This model provides a convenient tool for the incorporation of interface grading into the design of heterostructures.
Two-fluid description of wave-particle interactions in strong Buneman turbulence
Authors: Che H.
Published: June 2014

To understand the nature of anomalous resistivity in magnetic reconnection, we investigate turbulence-induced momentum transport and energy dissipation while a plasma is unstable to the Buneman instability in force-free current sheets. Using 3D particle-in-cell simulations, we find that the macroscopic effects generated by wave-particle interactions in Buneman instability can be approximately described by a set of electron fluid equations. We show that both energy dissipation and momentum transport along electric current in the current layer are locally quasi-static, but globally dynamic and irreversible. Turbulent drag dissipates both the streaming energy of the current sheet and the associated magnetic energy. The net loss of streaming energy is converted into the electron component heat conduction parallel to the magnetic field and increases the electron Boltzmann entropy. The growth of self-sustained Buneman waves satisfies a Bernoulli-like equation that relates the turbulence-induced convective momentum transport and thermal momentum transport. Electron trapping and de-trapping drive local momentum transports, while phase mixing converts convective momentum into thermal momentum. The drag acts like a micro-macro link in the anomalous heating processes. The decrease of magnetic field maintains an inductive electric field that re-accelerates electrons, but most of the magnetic energy is dissipated and converted into the component heat of electrons perpendicular to the magnetic field. This heating process is decoupled from the heating of Buneman instability in the current sheets. Ion heating is weak but ions play an important role in assisting energy exchanges between waves and electrons. Cold ion fluid equations together with our electron fluid equations form a complete set of equations that describes the occurrence, growth, saturation and decay of the Buneman instability.
An evolving autoimmune microenvironment regulates the quality of effector T cell restimulation and function
Authors: Friedman Rachel S. , Lindsay Robin S. , Lilly Jason K. , Nguyen Vinh , Sorensen Caitlin M. , Jacobelli Jordan , Krummel Matthew F.
Published: June 2014

Significance

Autoimmunity is self-perpetuating within the islets at the time of type 1 diabetes diagnosis. However, little is known about how pathogenic effector T cell functions are stimulated within the islets. Here, we show that the infiltration state of the islet affects T cell interactions with antigen-presenting cells and corresponding T cell effector cytokine production within the islets. This work identifies a restimulation event that is modified by the local islet environment as a critical step in the expression of T cell effector functions and autoimmune tissue destruction.
Revisiting and Revising the Tobacco Rebellion
Authors: Soudavar Farmanfarmaian Fatema
Published: June 2014

The major foreign concessions granted in the reign of Nasser al-Din Shah Qajar have received considerable attention, none more so than the Tobacco Rebellion, which is generally viewed as a watershed event in the awakening of political consciousness in Iran. Although mentioned in most of the published material on the precedents of the Constitutional Revolution of 1906, a revised narrative of the tobacco rebellion is overdue. This paper fills the gaps and revises some of the widely held assumptions on the forces that unleashed a nationwide movement that almost brought down the Qajar dynasty. The emphasis is on the incendiary protests in Tabriz and the largely neglected role of Hajj Kazem Malek-al-Tojjar. This article, which is the fifth of a series by the author on the two Malek-al-tojjar-e mamalek-e mahrusa of the Qajar era, questions the authorship of the fatwa (hokm) and re-assesses the motivation for its hasty proclamation and dissemination. In other words, were the “sensation-seekers” the heroes of reform or is there a neglected version to extricate from the truths and half-truths propounded about this watershed event?
Race, Culture, and Religion in the American South
Authors: Harvey Paul
Published: June 2014

The South still commonly appears as the land of the Bible Belt, of evangelical Protestant hegemony. Despite the rapidly increasing immigration from all parts of the world to the region, there is still justification for such a view. To study religion in the South, then, is to examine the influence of a dominant evangelical culture that has shaped the region’s social mores, religious minorities (including Catholicism, Judaism, and non-Christian immigrant religions), cultural forms, charged racial interactions, and political practices. In no other widely dispersed region, save for the Mormon regions of the Rocky Mountain West, does one family of religious belief and expression hold such sway over so many people and throughout such a large area. The biracial nature of evangelicalism in the South, as well, lends it a distinctive history and culture that alternately puzzles, repulses, and fascinates outsiders.

The South may be the Bible Belt, but, like Joseph’s coat, it is a belt of many colors, embroidered with a rich stitching together of words, sounds, and images from the inexhaustible resource of the scriptures. The rigid Bible Belt conservatism associated with the common understanding of religion in the South contrasts dramatically with the sheer creative explosiveness of southern religious cultural expression. Indeed, southern religious influences lay at the heart of much of 20th-century American popular culture. And it contrasts with a rapidly changing contemporary South in which Buddhist retreat centers and Ganesha temples are taking their place alongside Baptist and Methodist churches.
Long-term changes in abundance of Calanus finmarchicus south and north of Iceland in relation to environmental conditions and regional diversity in spring 1990–2013
Authors: Gislason Astthor , Petursdottir Hildur , Gudmundsson Kristinn
Published: June 2014

A 24-year time series of the abundance of Calanus finmarchicus from two standard sections differing in hydrographical conditions (Atlantic Water south of Iceland, Subarctic Water north of Iceland) was examined in relation to hydrography, phytoplankton dynamics, and large-scale climatic forcing (North Atlantic Oscillation, NAO). In the sea area around Iceland, C. finmarchicus is the most abundant mesozooplankter. The long-term variations were evaluated using multivariate statistics, principal component analyses, redundancy analyses (RDA), and principal response curves. Both south and north of Iceland, significant (RDA, p < 0.05, Monte-Carlo permutation tests) fluctuations in abundance and stages structure of C. finmarchicus between years were observed. The variations were, however, not in tune in south and north, indicating that the C. finmarchicus abundance may be influenced by different forcing factors in the two regions. South of Iceland, the analyses failed to find an effect of any of the environmental variables tested, whereas in the north the year-to-year variability was related to freshwater thickness west of Iceland and temperature north of the island (RDA, p < 0.05, Monte-Carlo permutation tests), indicating that advection of animals with currents from the south is important. In neither of the two regions was it possible to detect a unidirectional temporal trend in abundance of C. finmarchicus (RDA, p < 0.05, Monte-Carlo permutation tests). Based on a comparison with time series from nearby areas and the lack of a relationship with NAO, it is hypothesized that the growth and development of C. finmarchicus in Icelandic waters is more affected by local conditions than large-scale climatic forcing.
Relativistic iron Kα line detection in the Suzaku spectra of IC 4329A
Authors: Mantovani G. , Nandra K. , Ponti G.
Published: June 2014

We present an analysis of five Suzaku observations of the bright Seyfert1 galaxy IC 4329A. The broad energy band and high signal-to-noise ratio of the data give new constraints on the iron Kα line profile and its relationship with the Compton hump at higher energies. The Fe K bandpass is dominated by a narrow core (EW = 57$_{-3}^{+3}$ eV) at 6.4 keV consistent with neutral material. Using a physically motivated model, our analysis also reveals the presence of a broad iron Kα line (EW = 124$_{-11}^{+11}$ eV), most likely produced in the inner part of the accretion disc and blurred by general relativistic effects. This component is not immediately evident from the individual spectra, but is clearly present in the stacked residuals of all five observations, and has high statistical significance. This highlights the difficulty in identifying broad iron lines in active galactic nuclei, even in data with very high signal-to-noise ratio, as they are difficult to disentangle from the continuum. The data are consistent with the narrow and broad iron line components tracking the Compton Hump, but do not provide clear evidence that this is the case. An additional narrow Fe xxvi emission line at 6.94 keV is also seen, suggesting the presence of ionized material relatively distant from the central region. There is also a hint of variability, so the precise origin of this line remains unclear.
The vertical structure and kinematics of grand design spirals
Authors: Debattista Victor P.
Published: June 2014

We use an N-body simulation to study the 3D density distribution of spirals and the resulting stellar vertical velocities. Relative to the disc's rotation, the phase of the spiral's peak density away from the mid-plane trails that at the mid-plane. In addition, at fixed radius the density distribution is azimuthally skewed, having a shallower slope on the trailing side inside corotation and switching to shallower on the leading side beyond corotation. The spirals induce non-zero average vertical velocities, 〈Vz〉, as large as 〈Vz〉 ∼ 10–20 km s−1, consistent with recent observations in the Milky Way. The vertical motions are compressive (towards the mid-plane) as stars enter the spiral, and expanding (away from the mid-plane) as they leave it. Since stars enter the spiral on the leading side outside corotation and on the trailing side within corotation, the relative phase of the expanding and compressive motions switches sides at corotation. Moreover, because stars always enter the spiral on the shallow density gradient side and exit on the steeper side, the expanding motions are larger than the compressing motions.
Rosette modes of oscillations of rotating stars caused by close degeneracies. II. Nonaxisymmetric modes
Authors: Saio Hideyuki , Takata Masao
Published: June 2014

Our previous analysis of axisymmetric rosette modes of oscillations in rigidly rotating stars is extended to nonaxisymmetric modes. The rosette modes, which have peculiar eigenfunctions, are formed by interaction among g modes having close frequencies with the particular rules regarding radial orders and spherical degrees. Such interaction is caused by the second-order effect of the Coriolis force. For nonaxisymmetric cases, the first-order rotation effect, which is proportional to the azimuthal order and the rotation frequency, tends to work against the formation of rosette modes. It is, however, found that the poisoning effect is not so serious in many cases that nonaxisymmetric rosette modes are present. The difference between prograde and retrograde modes is discussed.
A Fungal Conserved Gene from the Basidiomycete Hebeloma cylindrosporum Is Essential for Efficient Ectomycorrhiza Formation
Authors: Doré Jeanne , Marmeisse Roland , Combier Jean-Philippe , Gay Gilles
Published: June 2014

We used Agrobacterium-mediated insertional mutagenesis to identify genes in the ectomycorrhizal fungus Hebeloma cylindrosporum that are essential for efficient mycorrhiza formation. One of the mutants presented a dramatically reduced ability to form ectomycorrhizas when grown in the presence of Pinus pinaster. It failed to form mycorrhizas in the presence of glucose at 0.5 g liter–1, a condition favorable for mycorrhiza formation by the wild-type strain. However, it formed few mycorrhizas when glucose was replaced by fructose or when glucose concentration was increased to 1 g liter–1. Scanning electron microscopy examination of these mycorrhizas revealed that this mutant was unable to differentiate true fungal sheath and Hartig net. Molecular analyses showed that the single-copy disrupting T-DNA was integrated 6,884 bp downstream from the start codon, of an open reading frame potentially encoding a 3,096-amino-acid-long protein. This gene, which we named HcMycE1, has orthologs in numerous fungi as well as different other eukaryotic microorganisms. RNAi inactivation of HcMycE1 in the wild-type strain also led to a mycorrhizal defect, demonstrating that the nonmycorrhizal phenotype of the mutant was due to mutagenic T-DNA integration in HcMycE1. In the wild-type strain colonizing P. pinaster roots, HcMycE1 was transiently upregulated before symbiotic structure differentiation. Together with the inability of the mutant to differentiate these structures, this suggests that HcMycE1 plays a crucial role upstream of the fungal sheath and Hartig net differentiation. This study provides the first characterization of a fungal mutant altered in mycorrhizal ability.
Appropriateness of Emergency Department Use in Pediatric Inflammatory Bowel Disease
Authors: Hoffenberg Edward J. , Park K.T. , Dykes Dana M. , Fridge Jacqueline , Kappelman Michael D. , Leibowitz Ian H. , Tsou V. Marc , Colletti Richard B.
Published: June 2014

Objectives:

We sought to characterize emergency department (ED) encounters for pediatric inflammatory bowel disease (IBD) to identify areas for prevention.

Methods:

Retrospective chart review of 5 consecutive ED encounters at 7 centers was performed.

Results:

Of 35 unique encounters by 32 patients, 3 main factors contributed to ED utilization: disease severity or course, day or time of care, and physician instruction. Of the ED encounters, approximately one‐fifth were judged medically unnecessary, and one‐half avoidable in a more optimal health care system.

Conclusions:

ED visits by pediatric patients with IBD may be reduced in a more optimal health care system.
Growth and Nutrition in Children With Trichothiodystrophy
Authors: Atkinson Emily C. , Thiara Diana , Tamura Deborah , DiGiovanna John J. , Kraemer Kenneth H. , Hadigan Colleen
Published: June 2014

Objectives:

Trichothiodystrophy (TTD) is a rare autosomal recessive disorder of DNA repair and transcription. Patients have multisystem abnormalities, including alterations in growth and development. This report characterizes the growth and nutritional status of a cohort of children with TTD.

Methods:

Twenty‐five patients with TTD were evaluated through a natural history study of patients with DNA repair diseases at the National Institutes of Health. Mean length of follow‐up was 2.7 years. Retrospective and prospective data on nutritional status and height/weight were collected.

Results:

In general, patients with TTD had considerable abnormalities in growth, with a mean height‐for‐age z score of −2.75 and a mean weight‐for‐age z score of −2.60 at baseline clinical evaluation. The median weight‐for‐length at baseline was, however, 50th percentile and indicators of adequate nutrition such as serum albumin, hemoglobin, and vitamins D and B12 were largely within normal limits. Changes in growth parameters as children aged were characterized by further separation from standard growth curves (change height‐for‐age z score/year [−0.18 ± 0.42] and weight‐for‐age z score/year [−0.36 ± 0.51]). Patients who died during follow‐up (n = 5) had significantly lower standardized height (P = 0.03) and weight (P = 0.006), weight‐for‐length (<0.0001), and higher heart rates (P = 0.02) compared with the remainder of the cohort.

Conclusions:

Children with TTD have markedly diminished weight‐for‐age and height‐for‐age relative to reference populations. The cause for this stunted growth remains unclear but does not appear to be related to poor nutrient absorption or malnutrition.
Team swimming in ant spermatozoa
Authors: Pearcy Morgan , Delescaille Noémie , Lybaert Pascale , Aron Serge
Published: June 2014

In species where females mate promiscuously, competition between ejaculates from different males to fertilize the ova is an important selective force shaping many aspects of male reproductive traits, such as sperm number, sperm length and sperm–sperm interactions. In eusocial Hymenoptera (bees, wasps and ants), males die shortly after mating and their reproductive success is ultimately limited by the amount of sperm stored in the queen's spermatheca. Multiple mating by queens is expected to impose intense selective pressure on males to optimize the transfer of sperm to the storage organ. Here, we report a remarkable case of cooperation between spermatozoa in the desert antCataglyphis savignyi. Males ejaculate bundles of 50–100 spermatozoa. Sperm bundles swim on average 51% faster than solitary sperm cells. Team swimming is expected to increase the amount of sperm stored in the queen spermatheca and, ultimately, enhance male posthumous fitness.
The role of mechanical forces in the planar-to-bulk transition in growing
Escherichia coli
microcolonies
Authors: Grant Matthew A. A. , Wacław Bartłomiej , Allen Rosalind J. , Cicuta Pietro
Published: June 2014

Mechanical forces are obviously important in the assembly of three-dimensional multicellular structures, but their detailed role is often unclear. We have used growing microcolonies of the bacterium
Escherichia coli
to investigate the role of mechanical forces in the transition from two-dimensional growth (on the interface between a hard surface and a soft agarose pad) to three-dimensional growth (invasion of the agarose). We measure the position within the colony where the invasion transition happens, the cell density within the colony and the colony size at the transition as functions of the concentration of the agarose. We use a phenomenological theory, combined with individual-based computer simulations, to show how mechanical forces acting between the bacterial cells, and between the bacteria and the surrounding matrix, lead to the complex phenomena observed in our experiments—in particular the observation that agarose concentration non-trivially affects the colony size at transition. Matching these approaches leads to a prediction for how the friction between the bacteria and the agarose should vary with agarose concentration. Our experimental conditions mimic numerous clinical and environmental scenarios in which bacteria invade soft matrices, as well as shedding more general light on the transition between two- and three-dimensional growth in multicellular assemblies.
A biomimetic accelerometer inspired by the cricket's clavate hair
Authors: Droogendijk H. , de Boer M. J. , Sanders R. G. P. , Krijnen G. J. M.
Published: June 2014

Crickets use so-called clavate hairs to sense (gravitational) acceleration to obtain information on their orientation. Inspired by this clavate hair system, a one-axis biomimetic accelerometer has been developed and fabricated using surface micromachining and SU-8 lithography. An analytical model is presented for the design of the accelerometer, and guidelines are derived to reduce responsivity due to flow-induced contributions to the accelerometer's output. Measurements show that this microelectromechanical systems (MEMS) hair-based accelerometer has a resonance frequency of 320 Hz, a detection threshold of 0.10 ms
−2
and a dynamic range of more than 35 dB. The accelerometer exhibits a clear directional response to external accelerations and a low responsivity to airflow. Further, the accelerometer's physical limits with respect to noise levels are addressed and the possibility for short-term adaptation of the sensor to the environment is discussed.
Comparative genomics of the mimicry switch inPapilio dardanus
Authors: Timmermans Martijn J. T. N. , Baxter Simon W. , Clark Rebecca , Heckel David G. , Vogel Heiko , Collins Steve , Papanicolaou Alexie , Fukova Iva , Joron Mathieu , Thompson Martin J. , Jiggins Chris D. , ffrench-Constant Richard H. , Vogler Alfried P.
Published: June 2014

The African Mocker Swallowtail,Papilio dardanus, is a textbook example in evolutionary genetics. Classical breeding experiments have shown that wing pattern variation in this polymorphic Batesian mimic is determined by the polyallelicHlocus that controls a set of distinct mimetic phenotypes. Using bacterial artificial chromosome (BAC) sequencing, recombination analyses and comparative genomics, we show thatHco-segregates with an interval of less than 500 kb that is collinear with two other Lepidoptera genomes and contains 24 genes, including the transcription factor genesengrailed(en) andinvected(inv).His located in a region of conserved gene order, which argues against any role for genomic translocations in the evolution of a hypothesized multi-gene mimicry locus. Natural populations ofP. dardanusshow significant associations of specific morphs with single nucleotide polymorphisms (SNPs), centred onen. In addition, SNP variation in theHregion reveals evidence of non-neutral molecular evolution in theengene alone. We find evidence for a duplication potentially driving physical constraints on recombination in thelambornimorph. Absence of perfect linkage disequilibrium between different genes in the other morphs suggests thatHis limited to nucleotide positions in the regulatory and coding regions ofen. Our results therefore support the hypothesis that a single gene underlies wing pattern variation inP. dardanus.