bluuebunny/crossref_metadata_2025 huggingface dataset:
Keeping party programmes on track: the transmission of the policy agendas of executive speeches to legislative outputs in the United Kingdom
Authors: Bevan Shaun , John Peter , Jennings Will
Published: April 2011

In the United Kingdom, the transmission between policy promises and statutes is assumed to be both rapid and efficient because of the tradition of party discipline, relative stability of government, absence of coalitions, and the limited powers of legislative revision in the second chamber. Even in the United Kingdom, the transmission is not perfect since legislative priorities and outputs are susceptible to changes in public opinion or media coverage, unanticipated events in the external world, backbench rebellions, changes in the political parties, and the practical constraints of administering policies or programmes. This paper investigates the strength of the connection between executive priorities and legislative outputs measured by the Speech from the Throne and Acts of Parliament from 1911 to 2008. These are categorized according to the policy content coding system of the UK Policy Agendas Project (www.policyagendas.org.uk). Time series cross-sectional analyses show that there is transmission of the policy agenda from the speech to acts. However, the relationship differs by party, strengthening over time for Conservative governments and declining over time for Labour and other governments.
Improvement in Bragg crystal bender design for a polychromator
Authors: Mairs T. R. , Borrel J. , Mathon O.
Published: April 2011

A new design for a polychromator Bragg bender at ID24 Dispersive EXAFS beamline (ESRF) shows improvements in stability, in the shape of the bent crystal and in the efficiency of adjustments to find the best focal spot.
Topography, the geoid, and compensation mechanisms for the southern Rocky Mountains
Authors: Coblentz D. , Chase C. G. , Karlstrom K. E. , van Wijk J.
Published: March 2011

The southern Rockies of Colorado are anomalously high (elevations greater than 2800 m), topographically rough (implying active uplift), and underlain by significant low‐velocity anomalies in the upper mantle that suggest an intimate relationship between mantle geodynamic processes and the surface topography. The region is in isostatic equilibrium (i.e., near‐zero free‐air gravity anomaly); however, the poor correlation between the high topography and crustal thickness makes the application of simple compensation models (e.g., pure Heiskanen or Pratt‐Hayford) problematic. Knowledge of how the current topography of the Rockies is isostatically compensated could provide constraints on the relative role of sublithospheric buoyancy versus lithospheric support. Here we evaluate the geoid and its relationship to the topography (using the geoid‐to‐elevation ratio (GTR) in the spatial domain and the admittance in the frequency domain) to constrain the mechanism of compensation. We separate the upper mantle geoid anomalies from those with deeper sources through the use of spherical harmonic filtering of the EGM2008 geoid. We exploit the fact that at wavelengths greater than the flexural wavelength where features are isostatically compensated, the geoid/topography ratio can be used to estimate the depth of compensation and the elastic thickness of the lithosphere. The results presented below indicate that the main tectonic provinces of the western United States have moderate geoid/topography ratios between 3.5 and 5.5 m/km (∼3.9 for the southern Rockies, ∼4.25 for the Colorado Plateau, and ∼5.2 for the Northern Basin and Range) suggesting shallow levels of isostatic compensation. In terms of the elastic thickness of the lithosphere, our results indicate an elastic thickness of less than 20 km. These value support the notion that a major portion of the buoyancy that has driven uplift resides at depths less than 100 km and that upper mantle processes such as small‐scale convection may play a significant role in the buoyant uplift of the southern Rockies (as well as other actively uplifting areas of the western United States). Further support for this hypothesis is provided by high coherence for the geoid‐topography relationship for nearly all wavelengths between 50 and 1000 km.
Use of single‐component wind speed in Rankine‐Hugoniot analysis of interplanetary shocks
Authors: Vorotnikov Vasiliy S. , Smith Charles W. , Farrugia Charles J. , Meredith Calum J. , Hu Qiang , Szabo Adam , Skoug Ruth M. , Cohen Christina M. S. , Davis Andrew J. , Yumoto Kiyohumi
Published: March 2011

We have extended and deployed a routine designed to run independently on the Web providing real‐time analysis of interplanetary shock observations from L1. The program accesses real‐time magnetic field, solar wind speed, and proton density data from the Advanced Composition Explorer (ACE) spacecraft, searches for interplanetary shocks, analyzes shocks according to the Rankine‐Hugoniot (R‐H) jump conditions, and provides shock solutions on the Web for space weather applications. Because the ACE real‐time data stream contains the wind speed but not the three‐component wind velocity, we describe modifications to the R‐H analysis that use the scalar wind speed and show successful results for analyses of strong interplanetary shocks at 1 AU. We compare the three‐component and one‐component solutions and find the greatest disagreement between the two rests in estimations of the shock speed rather than the shock propagation direction. Uncertainties in magnetic quantities such as magnetic compression and shock normal angle relative to the upstream magnetic field show large uncertainties in both analyses when performed using an automated routine whereas analyses of the shock normal alone do not. The automated data point selection scheme, together with the natural variability of the magnetic field, is inferred to be a problem in a few instances for this and other reasons. For a broad range of interplanetary shocks that arrive 30 to 60 min after passing L1, this method will provide 15 to 45 min of advanced warning prior to the shock's collision with the Earth's magnetopause. The shock, in turn, provides advance warning of the approaching driver gas.
The oncometabolite 2‐hydroxyglutarate inhibits histone lysine demethylases
Authors: Chowdhury Rasheduzzaman , Yeoh Kar Kheng , Tian Ya‐Min , Hillringhaus Lars , Bagg Eleanor A , Rose Nathan R , Leung Ivanhoe K H , Li Xuan S , Woon Esther C Y , Yang Ming , McDonough Michael A , King Oliver N , Clifton Ian J , Klose Robert J , Claridge Timothy D W , Ratcliffe Peter J , Schofield Christopher J , Kawamura Akane
Published: April 2011

Mutations in isocitrate dehydrogenases (IDHs) have a gain‐of‐function effect leading to R(−)‐2‐hydroxyglutarate (R‐2HG) accumulation. By using biochemical, structural and cellular assays, we show that either or both R‐ and S‐2HG inhibit 2‐oxoglutarate (2OG)‐dependent oxygenases with varying potencies. Half‐maximal inhibitory concentration (IC50) values for the R‐form of 2HG varied from approximately 25 μM for the histone Nε‐lysine demethylase JMJD2A to more than 5 mM for the hypoxia‐inducible factor (HIF) prolyl hydroxylase. The results indicate that candidate oncogenic pathways in IDH‐associated malignancy should include those that are regulated by other 2OG oxygenases than HIF hydroxylases, in particular those involving the regulation of histone methylation.
A highly organocatalytic stereoselective double Michael reaction: efficient construction of optically enriched spirocyclic oxindoles
Authors: Wang Liang-Liang , Peng Lin , Bai Jian-Fei , Jia Li-Na , Luo Xi-Ya , Huang Qing-Chun , Xu Xiao-Ying , Wang Li-Xin
Published: April 2011

An array of spirocyclic oxindoles have been constructed via a double Michael reaction in high yields and excellent enantioselectivities.
Apraxia of Speech in Children and Adolescents: Applications of Neuroscience to Differential Diagnosis and Intervention
Authors: Burns Martha S.
Published: April 2011

This paper presents an overview of clinical and neuroscience research that is relevant to distinguishing characteristics of childhood apraxia of speech (CAS) from perceptual/phonological disorders (PPD) in children with speech sound disorders. An initial attempt at developing a clinical checklist of as few as seven speech production characteristics, based on a literature review, may be useful for distinguishing CAS from PPD. Data on 11 children seen for intensive speech language intervention in 2008 are presented. The paper also provides longitudinal data on four children seen over two decades that presented with CAS vs. PPD. Clinical implications of a treatment outcome study, the CAS checklist, and longitudinal case studies are discussed.
Microfluidic enrichment of small proteins from complex biological mixture on nanoporous silica chip
Authors: Hu Ye , Gopal Ashwini , Lin Kevin , Peng Yang , Tasciotti Ennio , Zhang Xiaojing (John) , Ferrari Mauro
Published: April 2011

The growing field of miniaturized diagnostics is hindered by a lack of pre-analysis treatments that are capable of processing small sample volumes for the detection of low concentration analytes in a high-throughput manner. This letter presents a novel, highly efficient method for the extraction of low-molecular weight (LMW) proteins from biological fluids, represented by a mixture of standard proteins, using integrated microfluidic systems. We bound a polydimethylsiloxane layer patterned with a microfluidic channel onto a well-defined nanoporous silica substrate. Using rapid, pressure-driven fractionation steps, this system utilizes the size-exclusion properties of the silica nanopores to remove high molecular weight proteins while simultaneously isolating and enriching LMW proteins present in the biological sample. The introduction of the microfluidic component offers important advantages such as high reproducibility, a simple user interface, controlled environment, the ability to process small sample volumes, and precise quantification. This solution streamlines high-throughput proteomics research on many fronts and may find broad acceptance and application in clinical diagnostics and point of care detection.
Stem cells in microfluidics
Authors: Wu Huei-Wen , Lin Chun-Che , Lee Gwo-Bin
Published: April 2011

Microfluidic techniques have been recently developed for cell-based assays. In microfluidic systems, the objective is for these microenvironments to mimic in vivo surroundings. With advantageous characteristics such as optical transparency and the capability for automating protocols, different types of cells can be cultured, screened, and monitored in real time to systematically investigate their morphology and functions under well-controlled microenvironments in response to various stimuli. Recently, the study of stem cells using microfluidic platforms has attracted considerable interest. Even though stem cells have been studied extensively using bench-top systems, an understanding of their behavior in in vivo-like microenvironments which stimulate cell proliferation and differentiation is still lacking. In this paper, recent cell studies using microfluidic systems are first introduced. The various miniature systems for cell culture, sorting and isolation, and stimulation are then systematically reviewed. The main focus of this review is on papers published in recent years studying stem cells by using microfluidic technology. This review aims to provide experts in microfluidics an overview of various microfluidic systems for stem cell research.
A microfluidic membrane device to mimic critical components of the vascular microenvironment
Authors: Srigunapalan Suthan , Lam Cameron , Wheeler Aaron R. , Simmons Craig A.
Published: April 2011

Vascular function, homeostasis, and pathological development are regulated by the endothelial cells that line blood vessels. Endothelial function is influenced by the integrated effects of multiple factors, including hemodynamic conditions, soluble and insoluble biochemical signals, and interactions with other cell types. Here, we present a membrane microfluidic device that recapitulates key components of the vascular microenvironment, including hemodynamic shear stress, circulating cytokines, extracellular matrix proteins, and multiple interacting cells. The utility of the device was demonstrated by measuring monocyte adhesion to and transmigration through a porcine aortic endothelial cell monolayer. Endothelial cells grown in the membrane microchannels and subjected to 20 dynes/cm2 shear stress remained viable, attached, and confluent for several days. Consistent with the data from macroscale systems, 25 ng/ml tumor necrosis factor (TNF)-α significantly increased RAW264.7 monocyte adhesion. Preconditioning endothelial cells for 24 h under static or 20 dynes/cm2 shear stress conditions did not influence TNF-α-induced monocyte attachment. In contrast, simultaneous application of TNF-α and 20 dynes/cm2 shear stress caused increased monocyte adhesion compared with endothelial cells treated with TNF-α under static conditions. THP-1 monocytic cells migrated across an activated endothelium, with increased diapedesis in response to monocyte chemoattractant protein (MCP)-1 in the lower channel of the device. This microfluidic platform can be used to study complex cell-matrix and cell-cell interactions in environments that mimic those in native and tissue engineered blood vessels, and offers the potential for parallelization and increased throughput over conventional macroscale systems.
Evolution of microscopic and mesoscopic synchronized patterns in complex networks
Authors: Gómez-Gardeñes Jesús , Moreno Yamir , Arenas Alex
Published: April 2011

Previous studies about synchronization of Kuramoto oscillators in complex networks have shown how local patterns of synchronization emerge differently in homogeneous and heterogeneous topologies. The main difference between the paths to synchronization in both topologies is rooted in the growth of the largest connected component of synchronized nodes when increasing the coupling between the oscillators. Nevertheless, a recent study focusing on this same phenomenon has claimed the contrary, stating that the statistical distribution of synchronized clusters for both types of networks is similar. Here we provide extensive numerical evidences that confirm the original claims, namely, that the microscopic and mesoscopic dynamics of the synchronized patterns indeed follow different routes.
The interaction between multiplex community networks
Authors: Hao Junjun , Cai Shuiming , He Qinbin , Liu Zengrong
Published: April 2011

Multiplex community networks, consisting of several different types of simplex networks and interconnected among them, are ubiquitous in the real world. In this paper, we carry out a quantitative discussion on the interaction among these diverse simplex networks. First, we define two measures, mutual-path-strength and proximity-node-density, based on twoplex community networks and then propose an impact-strength-index (ISI) to describe the influence of a simplex network on the other one. Finally, we apply the measure ISI to make an explanation for the challenge system of social relations from the viewpoint of network theory. Numerical simulations show that the measure ISI can describe the interaction between multiplex community networks perfectly.
Electromagnetic characteristics of manganese oxide-coated Fe3O4 nanoparticles at 2-18 GHz
Authors: Yang R.B. , Liang W.F. , Lin C.K.
Published: April 2011

The dielectric and magnetic properties of manganese oxide-coated Fe3O4 nanoparticles (NPs) were measured by the transmission/reflection method in 2-18 GHz. MnOx-coated Fe3O4 NPs were prepared by sol-gel method followed by heat-treating at 300, 400, and 500 °C, respectively. The heat-treated powders were then used as magnetic fillers and added to an epoxy resin to prepare MnOx-coated Fe3O4 composites for the complex permittivity (ɛ′-jɛ″) and permeability (μ′-jμ″) measurements. After the sol-gel process, the coating of manganese oxide (mixture of major Mn2O3 and minor Mn3O4) reduced the value of ɛ′. The lower the heat-treating temperature, the larger the decrease in ɛ′. The relative decrease in ɛ′, compared with uncoated Fe3O4 nanoparticles, is 28.7, 23.5, and 20.0% for coated MnOx heat-treated at 300, 400, and 500 °C, respectively, while the relative decrease in ɛ″ is 74.1, 68.8, and 65.2%, respectively. In the present study, MnOx-coated Fe3O4 exhibited a significant decrease in dielectric loss tangent of ∼100% compared to that of uncoated NPs and can be of practical use for microwave components.
Static and dynamic magnetic properties of epitaxial Co2FeAl Heusler alloy thin films
Authors: Ortiz G. , Gabor M. S. , Petrisor, Jr. T. , Boust F. , Issac F. , Tiusan C. , Hehn M. , Bobo J. F.
Published: April 2011

Structural and magnetic properties of epitaxial Co2FeAl Heusler alloy thin films were investigated. Films were deposited on single crystal MgO (001XS) substrates at room temperature, followed by an annealing process at 600 °C. MgO and Cr buffer layers were introduced in order to enhance crystalline quality, and improve magnetic properties. Structural analyses indicate that samples have grown in the B2 ordered epitaxial structure. VSM measures show that the MgO buffered sample displays a magnetization saturation of 1010 ± 30 emu/cm3, and Cr buffered sample displays a magnetization saturation of 1032 ± 40 emu/cm3. Damping factor was studied by strip-line ferromagnetic resonance measures. We observed a maximum value for the MgO buffered sample of about 8.5 × 10−3, and a minimum value of 3.8 × 10−3 for the Cr buffered one.
Transport of particles and microorganisms in microfluidic channels using rectified ac electro-osmotic flow
Authors: Wu Wen-I , Selvaganapathy P. Ravi , Ching Chan Y.
Published: April 2011

A new method is demonstrated to transport particles, cells, and other microorganisms using rectified ac electro-osmotic flows in open microchannels. The rectified flow is obtained by synchronous zeta potential modulation with the driving potential in the microchannel. Experiments were conducted to transport both neutral, charged particles, and microorganisms of various sizes. A maximum speed of 50 μm/s was obtained for 8 μm polystyrene beads, without any electrolysis, using a symmetrical square waveform driving electric field of 5 V/mm at 10 Hz and a 360 V gate potential with its polarity synchronized with the driving potential (phase lag=0°).
Mesocopic comparison of complex networks based on periodic orbits
Authors: Stoop R. , Joller J.
Published: April 2011

Complex noiseless dynamical systems can be represented in a compressed manner by unstable periodic orbits. It is unknown, however, how to use this technique to obtain a suitable notion of similarity among them, how to extend such an approach to more general complex networks, and how to apply such a method in the important case of noisy systems. Our approach provides a solution to these questions. For a proof-of-concept, we consider Drosophila’s precopulatory courtship, where our method reveals the existence of a complex grammar (similar to those found in complex physical systems and in language), leading to the conclusion that the observed grammar is very unlikely the product of chance.
Anomalous self-generated electrostatic fields in nanosecond laser-plasma interaction
Authors: Lancia L. , Grech M. , Weber S. , Marquès J.-R. , Romagnani L. , Nakatsutsumi M. , Antici P. , Bellue A. , Bourgeois N. , Feugeas J.-L. , Grismayer T. , Lin T. , Nicolaï Ph. , Nkonga B. , Audebert P. , Kodama R. , Tikhonchuk V. T. , Fuchs J.
Published: April 2011

Electrostatic (E) fields associated with the interaction of a well-controlled, high-power, nanosecond laser pulse with an underdense plasma are diagnosed by proton radiography. Using a current three-dimensional wave propagation code equipped with nonlinear and nonlocal hydrodynamics, we can model the measured E-fields that are driven by the laser ponderomotive force in the region where the laser undergoes filamentation. However, strong fields of up to 110 MV/m measured in the first millimeter of propagation cannot be reproduced in the simulations. This could point to the presence of unexpected strong thermal electron pressure gradients possibly linked to ion acoustic turbulence, thus emphasizing the need for the development of full kinetic collisional simulations in order to properly model laser-plasma interaction in these strongly nonlinear conditions.
Study of the magnetic anisotropy of micron-sized CoFeSiB glass covered amorphous wires
Authors: Fan J. , Chiriac H. , Li X. P.
Published: April 2011

In this study, the magnetic properties of CoFeSiB glass covered amorphous wires (GCAWs) concerning their anisotropy, susceptibility, and coercivity have been investigated. The microscopic hysteresis loops of GCAWs of different lengths ranging from 1 to 40 mm and different metallic diameters ranging from 7 to 30 μm, fabricated by the Taylor–Ulitovsky method, were measured using the induction method. The results showed that the anisotropy of the GCAWs depends on the coupling of magnetostriction and internal stresses, and can be tailored by varying the ratio of the glass coating layer thickness to the metal core radius because the ratio characterizes the stress in the ferromagnetic core. The larger the ratio, the smaller the angle between the easy axis of anisotropy and the circumferential direction. The results further showed that for a GCAW wire originally with helical anisotropy, shortening the length of the wire below a critical value −10 mm will change the anisotropy from helical to circumferential, because the wire end domains form circumferential anisotropy.
Study of the relaxation in diluted spin crossover molecular magnets in the framework of the mechano-elastic model
Authors: Enachescu Cristian , Stoleriu Laurentiu , Stancu Alexandru , Hauser Andreas
Published: April 2011

We model here the behavior of spin transition compounds, considering molecules arranged in a 2D hexagonal lattice and interacting via springs. The role of impurities in the clustering and nucleation phenomena is analyzed, as well as the manner in which the impurities affect the relaxation curves. The switching of the individual molecules is checked using a Monte Carlo procedure. When a molecule changes its state, it also modifies its volume, and the new equilibrium positions of all the molecules are calculated. As in previously reported experiments, it is found here that bigger impurities slow down the relaxation from the metastable high-spin state to the low-spin state, while smaller impurities act in an opposite way. It is shown that if the concentration of the impurities is higher than a certain threshold, then they act as a barrier, trammeling the fast evolution of domains developing from the edges.
Development of 〈100〉 crystallographic texture in magnetostrictive Fe–Ga microwires produced by in-rotating water spinning method
Authors: Lupu N. , Lostun M. , Corodeanu S. , Chiriac H.
Published: April 2011

Fe-22.5 at.% Ga microwires with diameters ranging from 150 to 350 μm were produced by the in-rotating water spinning (INROWASP) method. All microwires were found to be polycrystalline and developed 〈100〉 crystallographic textures along the wire symmetry axis. The microwires are magnetically soft with very little coercivity and reach saturation magnetization values of 1.5 T. The largest magnetostriction value, of 185 ppm, is obtained for microwires with a diameter of 260 μm, in the absence of prestress and stress-annealing treatments. The increase/decrease of the microwires’ diameter above/below 260 μm results in smaller magnetostriction values, with the minimum of 130 ppm being reached for microwires of 150 μm. The unique properties of microwires made by the INROWASP method make them attractive for further production of Fe–Ga long, continuous microwires with a specific crystallographic texture.
Generalized H-theorems for magnetization dynamics driven by a jump-noise process
Authors: Mayergoyz I. , Bertotti G. , Serpico C.
Published: April 2011

In this paper, stochastic magnetization dynamics driven by a jump-noise process is discussed and, under the condition of “detailed balance,” generalized H-theorems for this dynamics are established. These H-theorems reveal the existence of a class of functionals that monotonically decrease in time during stochastic magnetization dynamics.
Large-scale analysis of magnetic particle dynamics taking into account contact force and magnetic interaction with the fast multipole method
Authors: Tatsuishi Takuya , Takahashi Yasuhito , Miwa Masahiko , Wakao Shinji , Fujiwara Koji , Ishihara Yoshiyuki
Published: April 2011

This paper investigates a large-scale analysis of magnetic particles’ behavior in magnetic fields by using a novel method combining the discrete element method and the magnetic interaction calculation with the fast multipole method (FMM). Furthermore, the effective formulae for the derivative of the magnetic field in the FMM procedure, which is necessary to calculate magnetic forces among a large number of magnetic particles, are proposed. Numerical examples of large-scale magnetic-particle chain analysis that demonstrate the effectiveness of the proposed method are presented.
Competing magnetic interactions in the intermetallic compounds Pr5Ge3 and Nd5Ge3
Authors: Nirmala R. , Morozkin A. V. , Nigam A. K. , Lamsal Jagat , Yelon W. B. , Isnard O. , Granovsky S. A. , Bharathi K. Kamala , Quezado S. , Malik S. K.
Published: April 2011

Magnetic properties of polycrystalline Pr5Ge3 and Nd5Ge3 (hexagonal, Mn5Si3-type) compounds have been studied. Magnetization measurements in 0.5 T field indicate that the Pr5Ge3 orders antiferromagnetically at 18 K (TN). However, in an applied field of 10 mT, the zero-field-cooled and field-cooled magnetization bifurcates below ∼65 K. This and the positive paramagnetic Curie temperature, obtained from the Curie–Weiss fit to the paramagnetic susceptibility, suggest the presence of competing ferromagnetic and antiferromagnetic interactions. The magnetization versus field isotherm at 5 K shows an S-shaped curve and a weak tendency to saturation in fields of 9 T with negligible hysteresis. The magnetic moment attains a value of 1.6 μB/Pr3+ at 5 K in 9 T. The magnetic entropy change near the magnetic transition has been calculated by measuring magnetization versus field isotherms close to TN. The entropy change is found to be considerably large. Neutron diffraction study indicates that below ∼43 K the Nd5Ge3 has flat spiral ordering with wave vector K = [0, 0, ±1/5] (the flat spiral axis coincides with cell parameter, a). Neutron diffraction study of Pr5Ge3 suggests that the magnetic structure of Pr5Ge3 could be similar to that in Nd5Ge3.
In situ magnetoresistance measurements of ion-beam-etched Fe-Co thin films
Authors: Ohsawa Yuichi , Yamakawa Kiyoshi , Muraoka Hiroaki
Published: April 2011

The effect of ion-beam (IB) irradiation on magnetic softness in Fe-Co thin films was evaluated by means of in situ magnetoresistance (MR) measurements. A 25 nm Fe70Co30 film was etched by Ar IB, and successive MR measurements were performed in the same IB etching chamber. Since the IB etching and MR measurements were performed alternately in vacuum, it was possible to evaluate the etching effect on magnetic softness of the single sample without any capping layer interaction. We name the thickness below which the magnetic softness of the etched film starts to decrease as the critical thickness (Tcr). The Tcr was found to be affected by IB energy: 150 and 250 V IB, respectively, showed 7.5 and 10 nm smaller Tcr than that of 600 V IB. Structural analysis revealed the 600 V IB introduced a larger deterioration in the film crystallinity than with the 250 V IB.
“In-plane” and “out-of-plane” uniaxial anisotropy of amorphous precursors and nanocrystalline FeCuNbSiB alloys
Authors: Basheed G. A. , Kaul S. N. , Vázquez M.
Published: April 2011

The “in-plane” and “out-of-plane” angular dependence of ferromagnetic resonance data demonstrate that both cubic and uniaxial magnetocrystalline anisotropies are present in FeCuNbSiB nanocrystalline alloys. The intergrain exchange interactions, mediated by the spins of the amorphous ferromagnetic matrix, are unable (able) to average out the local uniaxial magnetocrystalline anisotropy of the Fe3B and Fe2Si nanocrystalline grains and, thereby, lead to the magnetic hardening (softening) in the early stages of nanocrystallization in most of the compositions (remaining ones).
Mathematical model I. Electron and quantum mechanics
Authors: Gadre Nitin Ramchandra
Published: April 2011

The basic particle electron obeys various theories like electrodynamics, quantum mechanics and special relativity. Particle under different experimental conditions behaves differently, allowing us to observe different characteristics which become basis for these theories. In this paper, we have made an attempt to suggest a classical picture by studying the requirements of these three modern theories. The basic presumption is: There must be certain structural characteristics in a particle like electron which make it obey postulates of modern theories. As it is ‘difficult’ to find structure of electron experimentally, we make a mathematical attempt. For a classical approach, we require well defined systems and we have studied a system with two charged particles, proton and electron in a hydrogen atom. An attempt has been made to give a model to describe electron as seen by the proton. We then discuss how the model can satisfy the requirements of the three modern theories in a classical manner. The paper discusses basic aspects of relativity and electrodynamics. However the focus of the paper is on quantum mechanics.
Steady plasma channel formation and particle acceleration in an interaction of an ultraintense laser with near-critical density plasma
Authors: Gu Y. J. , Kong Q. , Li Y. Y. , Ban H. Y. , Zhu Z. , Kawata S.
Published: April 2011

A well-defined near-steady plasma channel is successfully formed in an interaction of an intense short-pulse laser with a near-critical underdense plasma. The laser is well self-focused in the plasma channel. Our 2.5-dimensional particle-in-cell simulations also demonstrate a violent electron acceleration with a effective gradient of several tens of GeV/cm by a strong longitudinal charge-separated field. At the same time, a strong ion acceleration appears at the rear plasma boundary. The results present a regime for the plasma channel formation and the particle acceleration by ultrashort laser-plasma interaction.
Magnetic properties of exchange-coupled PtFe/Fe films with spacer layers
Authors: Cui W. B. , Liu W. , Yang F. , Li D. , Delikanli S. , Guo S. , Gong W. J. , Zhang Z. D.
Published: April 2011

The exchange coupling between PtFe and Fe in PtFe/Fe films with Cr2O3 or Cr2O3/Cu spacer layers is indirect and long range. Microstructures of as-deposited and annealed thin films are studied. Coercivity over 10 kOe is obtained in PtFe/Cr2O3(5 Å)/Fe(25 Å) films but decrease with thicker Cr2O3 spacer layer. Comparably, coercivity can be maintained at about 10 kOe if spacer layer is changed into Cr2O3(x Å)/Cu(5 Å) (5 Å ≤ x ≤ 25 Å). For a fixed total thickness of the spacer layers, the coercivity generally decreases with gradual replacement of Cr2O3 by Cu, indicating the different effects of spacer layers on mediating the exchange coupling between PtFe and Fe. Using Cr2O3 or Cr2O3/Cu as a spacer layer is a promising way for realizing exchange-coupled PtFe/Fe composite films.
Low switching current in a modified exchange-biased spin valve via antiferromagnetic spin transfer torque
Authors: Guo Jie , Jalil Mansoor B. A. , Ghee Seng
Published: April 2011

We analyze the current-induced spin transfer torque and magnetization reversal properties in an exchanged-biased spin valve (EBSV) structure FM2/NM/FM1/AFM, taking into consideration the exchange interaction between the ferromagnetic (FM) and the antiferromagnetic (AFM) layers. The passage of the spin current above a certain threshold value causes the magnetization to switch in some parts of the AFM layer. This in turn leads to a change in the magnitude and direction of the exchange-bias field, which can subsequently assist or hinder the magnetization switching of the adjacent FM layer and results in so-called inverse current-induced magnetization switching for a weakly-biased EBSV structure. The requisite critical current density to switch the AFM layer is theoretically found to be lower than that for the FM layer, which provides us a potential method to substantially reduce the critical current density for the spin transfer switching in EBSV-based devices.
Effect of track asymmetry and curvature on shingle writing scheme
Authors: Liu Feng , Li Shaoping , Bai Daniel , Mendez Hector , Pan Tao , Han Dehua , Mao Sining
Published: April 2011

Written transition curvature in perpendicular magnetic recording is generally understood to result in increased transition jitter noise and degraded signal to noise ratio or byte error rate (BER) performance. For the shingle writing scheme, asymmetry or curvature in written tracks is considered inherent due to the erasure and track edge writing characteristics. It is proposed that such a track asymmetry is more prominent at high track density/smaller track pitch recording conditions. In this report we present spin stand experimental results to study the effect of the possible track asymmetry or curvature by shingle writing and reading back in different skews. By comparing shingle writing BER bathtub profiles in different writing skew conditions 0°, +/−2°, +/−4°, +/−6°, the effect of varying shingle track asymmetry and curvature is analyzed via subsequent skewed reading process. The shingle writing BER bathtub profiles as well as the read back amplitude cross track profile are generally symmetric upon one sided erasure at different track pitches. We found that the 0° skew writing and reading process provides both the maximum BER and amplitude.
Ferromagnetic microstructured thin films with high complex permeability for microwave applications
Authors: Vernieres J. , Bobo J. F. , Prost D. , Issac F. , Boust F.
Published: April 2011

Ferromagnetic microstructured films of Ni80Fe20 with in-plane uniaxial anisotropy were prepared by RF magnetron sputtering and patterned into rectangles with the larger dimension parallel to the easy axis. Static properties have been measured using a magneto-optic-Kerr-effect test bench, and dynamic properties were also obtained in the microwave frequency range. Because of ferromagnetic resonance, high complex permeability is obtained, and this corresponds to losses that create local heating. So, at an appropriate frequency, a microwave incident magnetic field interacts with the film and generates heating. This heating is recorded using an infrared camera to provide magnetic field pattern images. This setup yields qualitative results and allows for magnetic field detection on a large dimension scale.
Tunable magnetic flux sensor using a metallic Rashba ring with half-metal electrodes
Authors: Chen J. , Jalil M. B. A. , Tan S. G.
Published: April 2011

We propose a magnetic field sensor consisting of a square ring made of metal with a strong Rashba spin–orbital coupling (RSOC) and contacted to half-metal electrodes. Due to the Aharonov–Casher effect, the presence of the RSOC imparts a spin-dependent geometric phase to conduction electrons in the ring. The combination of the magnetic flux emanating from the magnetic sample placed below the ring, and the Aharonov–Casher effect due to RSOC results in spin interference, which modulates the spin transport in the ring nanostructure. By using the tight-binding nonequilibrium Green’s function formalism to model the transport across the nanoring detector, we theoretically show that with proper optimization, the Rashba ring can function as a sensitive and tunable magnetic probe to detect magnetic flux.
Coupling strength with off-axial external field in magnetic tunnel junction cells
Authors: Chao C. T. , Kuo C. Y. , Chen C. C. , Horng Lance , Chang Y. J. , Wu Te-Ho , Isogami S. , Tsunoda M. , Takahashi M. , Wu J. C.
Published: April 2011

A series of hysteresis loops with off-axial external magnetic fields have been measured to identify magnetization reversal properties as well as coupling effects in magnetic tunnel junctions (MTJs). MTJ films, consisting of a synthetic artificial antiferromagnetic pinned layer of CoFeB/Ru/CoFe/IrMn, were patterned into an elliptical cell array with sizes of 200 × 300 nm and 500 × 750 nm. The hysteresis loops were measured using a vibrating sample magnetometer with various directions of the external magnetic field; the angle θ between the external magnetic field (H→E) and the biasing field of the pinned layer (H→B) was varied from 0° to 90°. The two significant coupling effects, ascribed to exchange bias between CoFe/IrMn and Ruderman–Kittel–Kasuya–Yosida–like coupling in CoFeB/Ru/CoFe, can be observed in these hysteresis loops. The angular dependence of the hysteresis loops is employed to characterize the variation of these coupling effects in extended and patterned MTJ films.
Magnetic and electrical properties of Mn–Zn ferrites synthesized by combustion method without subsequent heat treatments
Authors: Syue Ming-Ru , Wei Fu-Jin , Chou Chan-Shin , Fu Chao-Ming
Published: April 2011

Nanocrystalline ferrites MnxZn1−xFe2O4 (x = 0.0–1.0) were prepared by the combustion method without sequential heat treatment. As-synthesized MnxZn1−xFe2O4 ferrites, characterized by x-ray diffraction (XRD), have demonstrated a highly pure phase of spinel structure. From the analysis of XRD data with Scherrer’s formula, the average crystallite size is about 27–37 nm and the lattice parameters range from 8.457 to 8.515 Å. The saturated magnetization of the Mn–Zn ferrite samples, measured by vibrating sample magnetometer, is varied with the content of manganese. The high frequency electromagnetic properties were investigated by impedance spectra methods and the conduction mechanism was also discussed. The results imply that this combustion method without further thermal treatment is relatively efficient and economical as compared to conventional methods for industrial synthesis of ferrites in high frequency electromagnetic devices applications.
Magnetic and microwave properties of ferrimagnetic Zr-substituted Ba2Zn2Fe12O22 (Zn-Y) single crystals
Authors: Jalli Jeevan , Hong Yang-Ki , Bae Seok , Lee Jae-Jin , Abo Gavin S. , Park Ji-Hoon , Choi Byoung-Chul , Mewes Tim , Kim Seong-Gon , Gee Sung-Hoon , Nam In-Tak , Tanaka Terumitsu
Published: April 2011

Single crystals of Zr-substituted Zn-Y (Zr–ZnY; Ba2Zn2ZrxFe12−xO22) were grown from the flux system of BaCO3 and B2O3 by a high temperature slow cooling flux method. X-ray diffraction pattern confirmed the crystal structure with Zn–Y composition. The single crystals were characterized for magnetic and microwave properties. The measured anisotropy field (HA) and the in-plane magnetization (σs) are 13 kOe and 52.0 emu/g, respectively. Ferrimagnetic resonance measurements show 18 Oe of linewidth (ΔH) at 9 GHz. The combination of low ΔH with a high HA in Zr–ZnY hexaferrite is suitable for microwave devices, which can operate with low external biasing field.
Giant magnetostriction in antiperovskite Mn3CuN
Authors: Shibayama T. , Takenaka K.
Published: April 2011

Giant magnetostriction of up to 2000 ppm was discovered in the tetragonally distorted ferromagnetic phase of antiperovskite Mn3CuN. This magnetostriction was associated with the rearrangement of thermoelastic martensite variants by the magnetic field, similar to that of Ni2MnGa Heusler alloy. The nitrogen-deficient Mn3CuN0.8 contracts, whereas the stoichiometric Mn3CuN expands, along the field direction. This implies a rotation of the easy axis from the longer a axis in Mn3CuN to the shorter c axis in Mn3CuN0.8. The drastic reduction of the operating magnetic field for magnetostriction in Mn3CuN0.8 suggests a possible supermagnetostriction around the compositional region of direction change in the easy axis.
Nonextensive electron and ion dust charging currents
Authors: Amour Rabia , Tribeche Mouloud
Published: April 2011

The correct nonextensive electron and ion charging currents are presented for the first time based on the orbit motion limited approach. For −1<q<1, where q measures the amount of plasma nonextensivity, the nonextensive electron charging current is expressed in terms of the hypergeometric function. The variable dust charge is expressed in terms of the Lambert function and we take advantage of this transcendental function to investigate succinctly the effects of nonextensive charge carriers. The obtained formulas bring a possibility to build theories on nonlinear collective process in variable charge nonextensive dusty plasmas.
The pure rotational spectrum of HPS ($\tilde{\rm X}^1 {\rm A}^{\prime}$X̃1A′): Chemical bonding in second-row elements
Authors: Halfen D. T. , Clouthier D. J. , Ziurys L. M. , Lattanzi V. , McCarthy M. C. , Thaddeus P. , Thorwirth S.
Published: April 2011

The pure rotational spectrum of HPS, as well as its 34S and D isotopologues, has been recorded at microwave, millimeter, and submillimeter wavelengths, the first observation of this molecule in the gas phase. The data were obtained using a combination of millimeter direct absorption, Fourier transform microwave (FTMW), and microwave–microwave double-resonance techniques, which cover the total frequency range from 15 to 419 GHz. Quantum chemical calculations at the B3LYP and CCSD(T) levels were also performed to aid in spectral identification. HPS was created in the direct absorption experiment from a mixture of elemental phosphorus, H2S, and Ar carrier gas; DPS was produced by adding D2. In the FTMW study, these species were generated in a pulsed discharge nozzle from PH3 and H2S or D2S, diluted in neon. The spectra recorded for HPS and its isotopologues exhibit clear asymmetric top patterns indicating bent structures; phosphorus hyperfine splittings were also observed in HPS, but not DPS. Analysis of the data yielded rotation, centrifugal distortion, and phosphorus nuclear spin-rotation parameters for the individual species. The rm(1) structure for HPS, calculated from the rotational constants, is r(H–P) = 1.438(1) Å, r(P–S) = 1.9320(1) Å, and θ(H–P–S) = 101.85(9)°. Empirically correcting for zero-point vibrational effects yields the geometry re(H–P) = 1.4321(2) Å, re(P–S) = 1.9287(1) Å, and θe(H–P–S) = 101.78(1)°, in close agreement with the rm(1) structure. A small inertial defect was found for HPS indicating a relatively rigid molecule. Based on these data, the bonding in this species is best represented as H–P=S, similar to the first-row analog HNO, as well as HNS and HPO. Therefore, substitution of phosphorus and sulfur for nitrogen and oxygen does not result in a dramatic structural change.
The magnetization reversal and low field compensation in a Fe3O4/Mn3O4/Fe3O4 trilayer
Authors: Lin S. C. , Kuo K. M. , Chern G.
Published: April 2011

Fe3O4(25 nm)/Mn3O4(50 nm)/Fe3O4(25 nm) trilayered structures are fabricated by molecular beam epitaxy and detailed magnetization characterizations are studied. The remanence magnetization versus temperature (Mr–T) shows a magnetic compensation point at ∼22 K, but this is unexpected for the present configuration. The compensation state is thus attributed to a domain wall structure formed in Fe3O4 along the perpendicular direction due to the strong anisotropic energy of the tetragonal Mn3O4 relative to cubic Fe3O4. Magnetic hysteresis measurements at various temperatures support this domain wall configuration and also map out an H–T diagram which includes a low-field compensation and a high-field spin flop phase.
Measuring the hierarchy of feedforward networks
Authors: Corominas-Murtra Bernat , Rodríguez-Caso Carlos , Goñi Joaquín , Solé Ricard
Published: April 2011

In this paper we explore the concept of hierarchy as a quantifiable descriptor of ordered structures, departing from the definition of three conditions to be satisfied for a hierarchical structure: order, predictability, and pyramidal structure. According to these principles, we define a hierarchical index taking concepts from graph and information theory. This estimator allows to quantify the hierarchical character of any system susceptible to be abstracted in a feedforward causal graph, i.e., a directed acyclic graph defined in a single connected structure. Our hierarchical index is a balance between this predictability and pyramidal condition by the definition of two entropies: one attending the onward flow and the other for the backward reversion. We show how this index allows to identify hierarchical, antihierarchical, and nonhierarchical structures. Our formalism reveals that departing from the defined conditions for a hierarchical structure, feedforward trees and the inverted tree graphs emerge as the only causal structures of maximal hierarchical and antihierarchical systems respectively. Conversely, null values of the hierarchical index are attributed to a number of different configuration networks; from linear chains, due to their lack of pyramid structure, to full-connected feedforward graphs where the diversity of onward pathways is canceled by the uncertainty (lack of predictability) when going backward. Some illustrative examples are provided for the distinction among these three types of hierarchical causal graphs.
Phase locking of vortex based spin transfer oscillators to a microwave current
Authors: Dussaux A. , Khvalkovskiy A. V. , Grollier J. , Cros V. , Fukushima A. , Konoto M. , Kubota H. , Yakushiji K. , Yuasa S. , Ando K. , Fert A.
Published: April 2011

Phase locking experiments on vortex based spin transfer oscillators with an external microwave current are realized. We present clear evidence of synchronization, i.e., phase locking, frequency pulling, as well as fractional synchronization in this system with a minimum peak linewidth of only 3 kHz in the locked state. Large locking ranges are achieved (up to 1/3 of the oscillator frequency) allowing us to demonstrate the simultaneous phase locking of two independent oscillators connected in series with the external source.
Photothermal-reaction-assisted two-photon lithography of silver nanocrystals capped with thermally cleavable ligands
Authors: Kim Won Jin , Vidal Xavier , Baev Alexander , Jee Hong Sub , Swihart Mark T. , Prasad Paras N.
Published: April 2011

We report an alternative approach to produce micropatterns of metallic nanoparticles using photothermal-reaction-assisted two-photon direct laser writing. The patterns are achieved using a facile surface treatment of silver nanoparticles (Ag NPs) functionalized with thermally cleavable ligands; N-(tert-butoxycarbonyl)-L-cysteine methyl ester. The ligand cleavage initiated by pulsed laser-induced thermal reaction results in a significant change in dispersiblility of the nanocrystals, thereby enabling a solvent-selective development process after photopatterning. We demonstrated that Ag NP patterns with submicron linewidths can be achieved using near infrared pulsed laser illumination.