bluuebunny/crossref_metadata_2025 huggingface dataset:
SFHs Across the Merging Disks of Arp 244 – from FUV to MIR
Authors: Zhang Hong-Xin , Gao Yu , Kong Xu
Published: April 2010

Including MIPS 24 μm dust emission in the multi-band stellar population analysis, we roughly constrain the star formation histories (SFHs) of MIPS 24 μm selected star-forming regions across the merging disks of the Antennae galaxies. While the overlap regions hold the highest ratios of young over intermediate populations, the western-loop regions have the highest ratios of intermediate to old populations. We find two sequential star formation (SF) paths in the overlap regions, which we interpret as the imprint of the interpenetrating process of the two merging disks following their second close encounter.
Förderung von körperlicher Aktivität im betrieblichen Kontext
Authors: Fleig Lena , Lippke Sonia , Wiedemann Amelie U. , Ziegelmann Jochen P. , Reuter Tabea , Gravert Christian
Published: April 2010

Zusammenfassung. Theoriebasierte Interventionen zur Förderung von körperlicher Aktivität können auf Stadien der Verhaltensänderung maßgeschneidert werden. Die Grundlage hierfür liefern Stadienmodelle. Diese nehmen an, dass für den erfolgreichen Übergang von einem Stadium zum nächsten unterschiedliche sozial-kognitive Variablen bedeutsam sind. Ziel der Studie war es, stadienspezifische Effekte von stadienpassenden Interventionen auf körperliche Aktivität und sozial-kognitive Prädiktoren im betrieblichen Kontext zu untersuchen. 839 Mitarbeiter eines Großunternehmens wurden randomisiert einer stadienpassenden Intervention und einer stadien-unspezifischen Standardmaßnahme zugewiesen. Vor der Intervention sowie vier Wochen später wurden Zielsetzung, Planung und körperliche Aktivität erfasst. Die Datenanalyse erfolgte mittels Varianzanalyse mit Messwiederholung. Die stadienpassenden Interventionen erhöhten die stadienspezifischen Variablen effektiver als die Standardmaßnahme. Stadienpassende Interventionen scheinen effektiver zu sein als stadien-unspezifische Standardmaßnahmen. Neben Verhaltensmaßen sollten auch Veränderungen in sozial-kognitiven Variablen zur Evaluation von Interventionen herangezogen werden.
Vorsatzbildung und volitionale Unterstützung bei Gefäßpatienten
Authors: Pochstein Florian , Wegner Manfred
Published: April 2010

Zusammenfassung. Die Teilhabe von Menschen mit einer peripheren arteriellen Verschlusskrankheit (pAVK) am Alltag ist aufgrund der krankheitsbedingten Beschwerden stark eingeschränkt. Sport- und Bewegungstherapie kann helfen, wenn das Gefäßsporttraining regelmäßig und dauerhaft durchgeführt wird. Diese beiden Voraussetzungen werden aber von einem Großteil der Patienten trotz hoher Intention nicht erfüllt. Um diese Intentions-Verhaltens-Lücke zu überwinden, wurde eine volitional ausgerichtete Intervention bei 90 Patienten in einem experimentellen Design hinsichtlich ihrer Wirksamkeit überprüft. In einer experimentellen Studie mit drei Messzeitpunkten wurden die Patienten der Experimentalgruppe in der Bildung von Ausführungs- und Bewältigungsplänen durch eine kurze psychologische Intervention unterstützt. Die Erhöhung der Handlungskontrolle wurde durch wöchentliche Erinnerungen an die aufgestellten Pläne über sechs Wochen angestrebt. Varianzanalytische Überprüfungen bestätigen die Hypothese, dass motivierte pAVK-Patienten von dieser Intervention profitieren. Sowohl die volitionale Kompetenz als auch die tatsächlich durchgeführte körperliche Aktivität unterscheiden sich signifikant von den Werten der Kontrollgruppe.
Number Line Compression and the Illusory Perception of Random Numbers
Authors: Viarouge Arnaud , Hubbard Edward M. , Dehaene Stanislas , Sackur Jérôme
Published: April 2010

Developmental studies indicate that children initially possess a compressed intuition of numerical distances, in which larger numbers are less discriminable than small ones. Education then “linearizes” this responding until by about age eight, children become able to map symbolic numerals onto a linear spatial scale. However, this illusion of compression of symbolic numerals may still exist in a dormant form in human adults and may be observed in appropriate experimental contexts. To investigate this issue, we asked adult participants to rate whether a random sequence of numbers contained too many small numbers or too many large ones. Participants exhibited a large bias, judging as random a geometric series that actually oversampled small numbers, consistent with a compression of large numbers. This illusion resisted training on a number-space mapping task, even though performance was linear on this task. While the illusion was moderately reduced by explicit exposure to linear sequences, responding was still significantly compressed. Thus, the illusion of compression is robust in this task, but linear and compressed responding can be exhibited in the same participants depending on the experimental context.
Source parameters and time‐dependent slip distributions of slow slip events on the Cascadia subduction zone from 1998 to 2008
Authors: Schmidt D. A. , Gao H.
Published: April 2010

We invert for the time‐dependent slip history of slow slip events on the Cascadia subduction zone using GPS data from 1998 to 2008. The 16 slip transients have sufficient station coverage to solve for the slip distribution on the plate interface. GPS time series are inverted for fault slip using the Extended Network Inversion Filter. Limited station coverage south of Portland (45.5°N latitude) restricts our analysis to events on the northern half of the subduction zone. Slip is resolved at the base of the seismogenic zone and the slip distributions suggest a potential segment boundary near Seattle (47.6°N) that correlates roughly with geologic and tectonic boundaries. Events that initiate to the north and south tend to overlap at about this latitude. We compile statistics on source parameters, such as propagation rate, recurrence interval, and stress drop, which can be used to constrain proposed models of the source mechanics. Over a 10 year period, total strain release from slow slip events is nonuniform along strike with the greatest cumulative slip (27 cm) centered beneath Port Angeles (48.1°N). This slip patch also exhibits the most regular recurrence of Mw ∼6 events relative to other locations along strike. The spatial extent of the slip patch beneath Port Angeles correlates with the along‐strike bend of the Cascadia subduction zone in northwestern Washington, suggesting that plate geometry plays an important role in controlling the along‐strike characteristics of slow slip.
Production of methyl halides by Prochlorococcus and Synechococcus
Authors: Brownell D. K. , Moore R. M. , Cullen J. J.
Published: April 2010

The ocean is the dominant source of atmospheric methyl iodide (CH3I). The mechanisms of CH3I production in the marine environment are poorly understood. A previous laboratory and field study suggested Prochlorococcus marinus, a ubiquitous marine cyanobacterium, is a globally significant biological producer of CH3I. In this study, CH3I concentrations were measured in cultures of P. marinus (high‐light‐adapted MED4 and low‐light‐adapted CCMP 1427) and the marine cyanobacterium Synechococcus. Cell‐normalized production rates from P. marinus cultures (MED4) averaged 1.6 (±0.9) molecules of CH3I cell−1 d−1; these rates were 1000‐fold lower than production rates reported for the previous study, which reported comparable concentrations of CH3I in cultures but cell concentrations about 1000‐fold lower than measured in this study. Extrapolating CH3I production rates from the current study yields a global production rate of 0.6 Mmol yr−1 which accounts for 0.03% of the estimated global CH3I production, suggesting P. marinus is not a globally significant source of CH3I.
Source radiation invariant property of local and near‐regional shear‐wave coda: Application to source scaling for the Mw 5.9 Wells, Nevada sequence
Authors: Mayeda Kevin , Malagnini Luca
Published: April 2010

This study documents another unique property of local and regional shear‐wave coda: that scattering in the Earth's crust averages out source heterogeneities such as focal mechanism and directivity. We consider two recent events which exhibited significant source directivity. The first, an Mw 4.2 Oakland hills, California strike‐slip event on July 20, 2007, resulted in uncharacteristically large amounts of damage in the Montclair and south Berkeley neighborhoods, along strike and north‐west of the hypocenter, but almost no damage to the south‐east. The second event, the Mw 5.9 Wells, Nevada dip‐slip event of February 21, 2008, was well‐recorded by the Earthscope Transportable Array (USArray) and determined to exhibit south‐west directivity. We conclude with an example of corner‐frequency (fc) estimates from the Wells sequence, which showcase the coda's low variance, and find that scaling is non‐self‐similar, suggesting a change in dynamics between the mainshock and aftershocks.
Parallel proton fire hose instability in gyrotropic Hall MHD model
Authors: Wang B.‐J. , Hau L.‐N.
Published: April 2010

The linear theory and nonlinear evolution of parallel or classical fire hose instability previously studied based on hybrid particle simulations are examined within the framework of a gyrotropic Hall magnetohydrodynamic (MHD) model that incorporates the ion inertial effects arising from the Hall current but neglects the electron inertia in the generalized Ohm's law. Both the ion cyclotron and whistler waves become fire hose unstable for β∥ − > 2 + λi2k2/2 with right‐handed circular polarization, where λi and k are the ion inertial length and wave number, respectively, implying that the ion inertia plays a stabilizing role in parallel fire hose instability. Substantial noncoplanar components of the magnetic field and flow velocity may develop as a result of Hall current. The evolution characteristics of magnetic field fluctuations may depend on the Hall parameter h = λi/λr, where λr is the resistive length. For moderately and highly dispersive cases the instability may be purely growing in the early stage with the development of soliton‐like structures with depressed magnetic field on the order of a few ion inertial lengths and become propagating with right‐handed circular polarization in the late phase when the waves have inversely cascaded to large‐amplitude Alfvén waves of longer wavelengths. Oscillatory and damping behavior resembling those found in the kinetic model may be reproduced for single‐mode perturbations of long wavelengths with h ≤ 1. The saturated magnetic field is found to comply with the quasi‐linear theory.
Variability and trends in dry day frequency and dry event length in the southwestern United States
Authors: McCabe Gregory J. , Legates David R. , Lins Harry F.
Published: April 2010

Daily precipitation from 22 National Weather Service first‐order weather stations in the southwestern United States for water years 1951 through 2006 are used to examine variability and trends in the frequency of dry days and dry event length. Dry events with minimum thresholds of 10 and 20 consecutive days of precipitation with less than 2.54 mm are analyzed. For water years and cool seasons (October through March), most sites indicate negative trends in dry event length (i.e., dry event durations are becoming shorter). For the warm season (April through September), most sites also indicate negative trends; however, more sites indicate positive trends in dry event length for the warm season than for water years or cool seasons. The larger number of sites indicating positive trends in dry event length during the warm season is due to a series of dry warm seasons near the end of the 20th century and the beginning of the 21st century. Overall, a large portion of the variability in dry event length is attributable to variability of the El Niño–Southern Oscillation, especially for water years and cool seasons. Our results are consistent with analyses of trends in discharge for sites in the southwestern United States, an increased frequency in El Niño events, and positive trends in precipitation in the southwestern United States.
Cross‐boundary ambidexterity: Balancing exploration and exploitation in the fuel cell industry
Authors: Russo Angeloantonio , Vurro Clodia
Published: April 2010

AbstractThis paper presents a new perspective on the ambidexterity debate. Basing our work on the assumption that learning is a multilevel process, we develop and empirically test whether, how, and with what consequences firms can balance explorative and exploitative technology‐learning activities across their organizational boundaries. Hypotheses are tested through a longitudinal panel of data tracking the cross‐boundary learning strategies of 153 companies involved with innovation in the worldwide fuel cell industry over the period 1999–2006. By juxtaposing intra‐ and interorganizational exploration‐exploitation, we find that the pursuit of cross‐boundary ambidexterity is worthwhile. Firms that engage in internal exploitation tend to balance such learning orientation with explorative interorganizational agreements. Consistently, those firms engaged in external exploitation tend to balance it with an internal focus on exploration, at least in the case of exploitative alliances involving familiar partners. Moreover, results confirm that such complementary cross‐boundary strategies improve a firm's innovative performance.
Special Issue on: Designing internal organization for external knowledge sourcing
Authors: Colombo Massimo G. , Rabbiosi Larissa , Reichstein Toke
Published: April 2010

Abstract It is well established that heterogeneity among firms shapes their abilities to introduce process and product innovation. Moreover, few will dispute that such heterogeneity is triggered by differences in internal organizational structures, in the use of management practices, in resources available, and in the interaction with external actors. However, little is known about how firms design their boundaries and internal organizations to enable them to explore and exploit knowledge from external sources of knowledge. In addition, the innovation‐search literature widely treats organizational design as being fixed across these otherwise heterogeneous firms, neglecting the investigation of how particular organizational structures and management practices fit the interaction with specific types of sources, the motivations of these sources, and with modes of external interaction. Accordingly, this special issue intends to bridge research on organizational design and architecture on the one hand, and research on firms' external knowledge search on the other, in the attempt to pave a way for a mutually beneficial dialogue.
Development of a multipurpose vacuum chamber for serial optical and diffraction experiments with free electron laser radiation
Authors: Rajkovic I. , Hallmann J. , Grübel S. , More R. , Quevedo W. , Petri M. , Techert S.
Published: April 2010

In this paper we present a development of a multipurpose vacuum chamber which primal function is to be used in pump/probe experiments with free electron laser (FEL) radiation. The chamber is constructed for serial diffraction and serial spectroscopy allowing a fast exchange of samples during the measurement process. For the fast exchange of samples, liquid jet systems are used. Both applications, utilizing soft x-ray FEL pulses as pump and optical laser pulses as probe and vice versa are documented. Experiments with solid samples as well as the liquid jet samples are presented. When working with liquid jets, a system of automatically refilled liquid traps for capturing liquids has been developed in order to ensure stable vacuum conditions. Differential pumping stages are placed in between the FEL beamline and the experimental chamber so that working pressure in the chamber can be up to four orders of magnitude higher than the pressure in the FEL beamline.
The Hilbert Lagrangian and isometric embedding: Tetrad formulation of Regge–Teitelboim gravity
Authors: Estabrook Frank B.
Published: April 2010

We discuss exterior differential systems (EDSs) for the vacuum gravitational field. These EDSs are derived by varying the Hilbert–Einstein Lagrangian, given most elegantly as a Cartan 4-form calibrating 4-spaces embedded in ten flat dimensions. In particular, we thus formulate with tetrad equations the Regge–Teitelboim (RT) dynamics “à la string;” it arises when variation of the 4-spaces gives the Euler–Lagrange equations of a multicontact field theory. We calculate the Cartan character table of this EDS, showing the field equations to be well posed with no gauge freedom. The Hilbert Lagrangian as usually varied over just the intrinsic curvature structure of a 4-space yields only a subset of this dynamics, viz., solutions satisfying additional conditions constraining them to be Ricci flat. In the static spherically symmetric case, we present a new tetrad embedding in flat six dimensions, which allows reduction of the RT field equations to a quadrature; the Schwarzschild metric is a special case. As has previously been noted, there may be a classical correspondence of the RT theory with the hidden dimensions of brane theory, and perhaps this extended general relativistic dynamics holds in extreme circumstances where it can be interpreted as including a sort of dark or bulk energy even though no term with a cosmological constant is included in the Lagrangian. As a multicontact system, canonical quantization should be straightforward.
Experimental and theoretical study of the absorption properties of thiolated diamondoids
Authors: Landt Lasse , Bostedt Christoph , Wolter David , Möller Thomas , Dahl Jeremy E. P. , Carlson Robert M. K. , Tkachenko Boryslav A. , Fokin Andrey A. , Schreiner Peter R. , Kulesza Alexander , Mitrić Roland , Bonačić-Koutecký Vlasta
Published: April 2010

Nanoscale hybrid systems are a new class of molecular aggregates that offer numerous new possibilities in materials design. Diamondoid thiols are promising nanoscale building blocks for such hybrid systems. They allow the incorporation of functional groups and the investigation of their effects on the unique materials’ properties of diamondoids. Here we combine experimental data with ab initio theory to explore the optical properties of diamondoid thiols and their dependence on size and shape. Agreement between theoretically and experimentally obtained absorption spectra allows the identification of the nature of the optical transitions that are responsible for some photophysical and photochemical processes. We show that the optical properties of diamondoid thiols in the deep UV regime depend on the functionalization site but are largely size independent. Our findings provide an explanation for the disappearance of diamondoid UV photoluminescence upon thiolation for smaller diamondoids. However, our theoretical results indicate that for larger diamondoid thiols beyond the critical size of six diamondoid cages the lowest energy transitions are characterized by diamondoidlike states suggesting that UV luminescence may be regained.
Effect of vacancies on oxygen precipitation in germanium-doped Czochralski silicon
Authors: Wu Peng , Chen Jiahe , Ma Xiangyang , Yang Deren
Published: April 2010

The effect of vacancies introduced by rapid thermal annealing (RTA) on the oxygen precipitation in germanium-doped Czochralski (GCZ) silicon has been investigated. GCZ silicon is annealed at 650–1050 °C to facilitate the precipitation of oxygen. It is observed that the oxygen precipitation in silicon is enhanced by both the vacancies introduced during RTA pretreatment and the doping of germanium. Especially, we find that the enhancement effect of vacancies on the precipitation of oxygen is larger than that of germanium atoms. In contrast to non-RTA pretreatments, RTA pretreatments lead to less significant oxygen precipitation in GCZ silicon than in conventional Czochralski (CZ) silicon at temperatures ranging from 850 to 950 °C. The mechanism for the interaction between vacancies and germanium atoms in CZ silicon is elucidated.
Structural morphology and Mn distribution in annealed InP coimplanted with P and Mn
Authors: Bucsa I. G. , Cochrane R. W. , Roorda S.
Published: April 2010

We have studied the structural, chemical, and magnetic properties of InP following coimplantation with high energy P and Mn ions to fluences in excess of 1016 cm−2 and subsequent annealing above 600 °C. Rutherford backscattering spectrometry, x-ray diffraction, secondary ion mass spectrometer, and transmission electron microscopy measurements reveal that rapid thermal annealing causes only a partial epitaxial recrystallization of the layer amorphized by the implantations; the remaining region up to the surface crystallizes incoherently but retains most of the implanted Mn. Magnetic measurements demonstrate that fully three quarters of the Mn has been incorporated into MnP nanoparticles embedded into this polycrystalline InP region. The remaining Mn is most probably incorporated into the InP lattice but gives only a paramagnetic response that can be described by a simple Brillouin function at temperatures down to 5 K.
The geometric property of soliton solutions for the integrable KdV6 equations
Authors: Li Jibin , Zhang Yi
Published: April 2010

The geometric property of soliton solutions of the three completely integrable sixth-order nonlinear equations (KdV6) is studied by using the method of dynamical systems and the work of Wazwaz [Appl. Math. Comput. 204, 963 (2008)]. This paper proved that a solitary wave solution corresponds to a homoclinic orbit of a four-dimensional dynamical system to a equilibrium point. The orbit lies on the intersection curve of two level set passing through the same equilibrium point.
Quantitative analysis for hillocks grown from electroplated Sn film
Authors: Cheng Jing , Chen Samuel , Vianco Paul T. , Li James C. M.
Published: April 2010

Tin (Sn) films of 1 μm thick and 2–3 μm grain size were electroplated over a silicon (Si) wafer. The wafer was first deposited with an adhesion layer of chromium (Cr) followed by a nickel (Ni) using the evaporation technique. A special fixture was used to apply a biaxial compressive stress to the Sn film. After exposing the sample to 160 °C under vacuum for seven days, large hillocks were observed having dimensions of 10–30 μm in diameter and 30–150 μm in length. The hillock density was approximately seven per square mm. A quantitative method was developed using surface mapping and MATLAB™ to estimate the volume of hillocks per unit area of the Sn film and thus, to relate that volume to the local compressive stress. The rate of growth was modeled as a flow of Sn atoms along the Sn/Ni interface under the applied pressure gradient. Reasonable viscosity and self-diffusivity were calculated, which suggested that Sn/Ni interface diffusion was potentially the mechanism for hillock growth.
High-pressure synthesis and luminescent properties of cubic ZnO/MgO nanocomposites
Authors: Baranov A. N. , Kurakevych O. O. , Tafeenko V. A. , Sokolov P. S. , Panin G. N. , Solozhenko V. L.
Published: April 2010

The formation of the nanocrystalline rocksalt ZnO (rs-ZnO) has been in situ studied by x-ray diffraction with synchrotron radiation at high pressure and high temperature. A number of rs-ZnO/MgO nanocomposites with preset grain size were synthesized at 7 GPa and 800 K starting from wurtzite ZnO nanoparticles or nanorods. The use of MgO matrix allowed us to recover metastable rs-ZnO in the nanocrystalline form at ambient pressure. The cathodoluminescence measurements demonstrated the blue shift in the luminescence of rs-ZnO nanocrystals down to 402–408 nm that can be attributed to the enhanced incorporation of point defects with lower activation energy.
Effect of a dc bias field on the dynamic hysteresis of single-domain ferromagnetic particles
Authors: Déjardin P. M. , Kalmykov Yu. P. , Kashevsky B. E. , El Mrabti H. , Poperechny I. S. , Raikher Yu. L. , Titov S. V.
Published: April 2010

Dynamic magnetic hysteresis in uniaxial superparamagnetic nanoparticles in superimposed ac and dc magnetic fields of arbitrary amplitude is considered using Brown’s model of coherent rotation of the magnetization. The dependence of the area of the dynamic hysteresis loop on the temperature, frequency, and ac and dc bias fields is analyzed. In particular, the dynamic hysteresis loop of a single-domain ferromagnetic particle is substantially altered by applying a relatively weak dc field. Furthermore, it is shown that at intermediate to low ac field amplitudes, the dc bias field permits tuning of the magnetic power absorption of the particles, while for strong ac field amplitudes the effect becomes entirely analogous to that produced by the exchange biased anisotropy. Simple analytical formulas are provided in the linear response regime for the steady-state magnetization and loop area, exhibiting perfect agreement with the numerical solution of Brown’s Fokker–Planck equation. Comparison with previous results is also given.
Low temperature dielectric characterization of Mg-doped SrTiO3 thin films prepared by sol-gel
Authors: Okhay Olena , Wu Aiying , Vilarinho Paula M. , Tkach Alexander
Published: April 2010

Voltage dependence of dielectric constant ε′ of ferroelectrics and low dielectric loss tan δ of incipient ferroelectrics make them attractive for tuning elements in microwave circuits. In this letter, field dependence of the low-temperature dielectric permittivity and polarization of Mg-doped SrTiO3 films is studied. Incorporation of Mg on both Sr and Ti sites decreases the ε′ and relative tunability nr of sol-gel derived SrTiO3 films, whereas polarization is reduced by Ti site substitution only. tan δ of the studied films is ≤0.012, decreasing at low temperatures down to 0.001 when Ti is substituted by 5% of Mg.
MEMS-based high speed scanning probe microscopy
Authors: Disseldorp E. C. M. , Tabak F. C. , Katan A. J. , Hesselberth M. B. S. , Oosterkamp T. H. , Frenken J. W. M. , van Spengen W. M.
Published: April 2010

The high speed performance of a scanning probe microscope (SPM) is improved if a microelectromechanical systems (MEMS) device is employed for the out-of-plane scanning motion. We have carried out experiments with MEMS high-speed z-scanners (189 kHz fundamental resonance frequency) in both atomic force microscope and scanning tunneling microscope modes. The experiments show that with the current MEMS z-scanner, lateral tip speeds of 5 mm/s can be achieved with full feedback on surfaces with significant roughness. The improvement in scan speed, obtained with MEMS scanners, increases the possibilities for SPM observations of dynamic processes. Even higher speed MEMS scanners with fundamental resonance frequencies in excess of a megahertz are currently under development.
Simple relationship between the virial-route hypernetted-chain and the compressibility-route Percus–Yevick values of the fourth virial coefficient
Authors: Santos Andrés , Manzano Gema
Published: April 2010

As is well known, approximate integral equations for liquids, such as the hypernetted chain (HNC) and Percus–Yevick (PY) theories, are in general thermodynamically inconsistent in the sense that the macroscopic properties obtained from the spatial correlation functions depend on the route followed. In particular, the values of the fourth virial coefficient B4 predicted by the HNC and PY approximations via the virial route differ from those obtained via the compressibility route. Despite this, it is shown in this paper that the value of B4 obtained from the virial route in the HNC theory is exactly three halves the value obtained from the compressibility route in the PY theory, irrespective of the interaction potential (whether isotropic or not), the number of components, and the dimensionality of the system. This simple relationship is confirmed in one-component systems by analytical results for the one-dimensional penetrable-square-well model and the three-dimensional penetrable-sphere model, as well as by numerical results for the one-dimensional Lennard-Jones model, the one-dimensional Gaussian core model, and the three-dimensional square-well model.
Levitation effect in zeolites: Quasielastic neutron scattering and molecular dynamics study of pentane isomers in zeolite NaY
Authors: Borah Bhaskar J. , Jobic H. , Yashonath S.
Published: April 2010

We report the quasielastic neutron scattering (QENS) and molecular dynamics (MD) investigations into diffusion of pentane isomers in zeolite NaY. The molecular cross section perpendicular to the long molecular axis varies for the three isomers while the mass and the isomer-zeolite interaction remains essentially unchanged. Both QENS and MD results show that the branched isomers neopentane and isopentane have higher self-diffusivities as compared with n-pentane at 300 K in NaY zeolite. This result provides direct experimental evidence for the existence of nonmonotonic, anomalous dependence of self-diffusivity on molecular diameter known as the levitation effect. The energetic barrier at the bottleneck derived from MD simulations exists for n-pentane which lies in the linear regime while no such barrier is seen for neopentane which is located clearly in the anomalous regime. Activation energy is in the order Ea(n-pentane)>Ea(isopentane)>Ea(neopentane) consistent with the predictions of the levitation effect. In the liquid phase, it is seen that D(n-pentane)>D(isopentane)>D(neopentane) and Ea(n-pentane)<Ea(isopentane)<Ea(neopentane). Intermediate scattering function for small wavenumbers obtained from MD follows a single exponential decay for neopentane and isopentane. For n-pentane, a single exponential fit provides a poor fit especially at short times. Cage residence time is largest for n-pentane and lowest for neopentane. For neopentane, the width of the self-part of the dynamic structure factor shows a near monotonic decrease with wavenumber. For n-pentane a minimum is seen near k=0.5 Å−1 suggesting a slowing down of motion around the 12-ring window, the bottleneck for diffusion. Finally, the result that the branched isomer has a higher diffusivity as compared with the linear analog is at variation from what is normally seen.
Study of the interlayer coupling and its temperature dependence in spin valves with Ru and Cu spacers
Authors: Alayo W. , Baggio-Saitovitch E.
Published: April 2010

The IrMn/Co/NM/Ni81Fe19 spin valves, with the nonmagnetic (NM) spacers of Ru and Cu, were grown by sputtering and analyzed by magnetization versus magnetic field measurements at several temperatures. The loop of the free layer exhibits a loop shift proportional to the interlayer coupling strength. For fitting the NM layer thickness dependence of this loop shift, the oscillatory interlayer and the magnetostatic Néel mechanisms were considered. These analyses provided quantitative values of both contributions and showed that the oscillatory coupling mechanism dominates in the system with Ru spacer, while the Néel coupling mechanism dominates for the Cu spacer. In both systems, the temperature variations of the coupling are attributed to the spacer and spacer/magnet interfaces.
The critical current density in composite free layer structures for spin transfer torque switching
Authors: You Chun-Yeol
Published: April 2010

The critical current density for spin transfer torque switching with composite free layer structures is investigated using the macrospin Landau–Lifshitz–Gilbert equation. We consider a magnetic tunneling junction with a rigid fixed layer, and a composite free layer consisting of two coupled ferromagnetic layers in which the coupling is parallel or antiparallel. The dependence of critical current density on thickness, coupling sign and strength, spin torque efficiency, and magnetization of the composite free layer is explored. We determine that reduction in the critical current density can be achieved only through careful design of the composite free layer structures. We show the detailed spin dynamics of the composite free layer when the reduction in the critical current density is accomplished.
On photoinduced volume change in amorphous selenium: Quantum chemical calculation and Raman spectroscopy
Authors: Lukács R. , Veres M. , Shimakawa K. , Kugler S.
Published: April 2010

Hartree–Fock ab initio Raman spectra calculations and Raman spectroscopic measurements were carried out on amorphous selenium in order to identify the characteristic vibrational mode due to sigma bonds. Variations in measured peak intensity were observed as a consequence of band gap light illumination. Based on our previous theoretical investigations we originate these intensity variations from photoinduced covalent bond breaking.
Nonlocal heat transport in laser-produced aluminum plasmas
Authors: Yu Q. Z. , Li Y. T. , Weng S. M. , Dong Q. L. , Liu F. , Zhang Z. , Zhao J. , Lu X. , Danson C. , Pepler D. , Jiang X. H. , Liu Y. G. , Huang L. Z. , Liu S. Y. , Ding Y. K. , Wang Z. B. , Gu Y. , He X. T. , Sheng Z. M. , Zhang J.
Published: April 2010

The spatial and temporal evolutions of nonlocal heat transport in laser-produced aluminum plasmas are studied with the improvements of the Thomson scattering experiments and the kinetic Fokker–Planck simulations. The results are compared with the hydrodynamic simulations with the classical Spitzer–Härm theory. When another heater beam is used, the electron temperature decreases slowly and the temperature gradient becomes steep in the conduction zone. The nonlocal heat flux can be sustained at a high value with slow decrease for long time. The Fokker–Planck simulations considering electron-electron collisions can well describe the nonlocal heat transport process in laser-produced plasmas.
Generation of GeV protons from 1 PW laser interaction with near critical density targets
Authors: Bulanov Stepan S. , Bychenkov Valery Yu. , Chvykov Vladimir , Kalinchenko Galina , Litzenberg Dale William , Matsuoka Takeshi , Thomas Alexander G. R. , Willingale Louise , Yanovsky Victor , Krushelnick Karl , Maksimchuk Anatoly
Published: April 2010

The propagation of ultraintense laser pulses through matter is connected with the generation of strong moving magnetic fields in the propagation channel as well as the formation of a thin ion filament along the axis of the channel. Upon exiting the plasma the magnetic field displaces the electrons at the back of the target, generating a quasistatic electric field that accelerates and collimates ions from the filament. Two dimensional particle-in-cell simulations show that a 1 PW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to an energy of 1.3 GeV. Scaling laws and optimal conditions for proton acceleration are established considering the energy depletion of the laser pulse.
Exchange bias effect in Cu1−xFexO (0<x≤0.30) composites
Authors: Yin S. Y. , Yuan S. L. , Tian Z. M. , Wang C. H. , Huo S. X. , Duan H. N. , Zheng X. F. , Liu K. L.
Published: April 2010

A series of Cu1−xFexO (x=0.10, 0.15, 0.20, and 0.30) powder samples were synthesized by a coprecipitation method. The exchange bias field (HEB) accompanying vertical magnetization shift is observed in the system at low temperatures, after the sample is cooled from 300 to 10 K under 10 kOe magnetic field. The exchange bias effect has been investigated for Cu1−xFexO with different doping concentration. Although the magnetic properties increases with the increasing doping concentration, the HEB and vertical magnetization shift vary nonmonotonously. The significant difference is indicated the exchange bias effect can be controlled by tuning the doping concentration for altering coupling interaction at interface layers. Furthermore, the exchange bias field shows a linear dependence on the vertical shift. The exchange coupling at the interface between the ferromagnetic phase and the spin-glass-like phase (or antiferromagnetic) can explain these phenomenon.
Insights on the origin of the Debye process in monoalcohols from dielectric spectroscopy under extreme pressure conditions
Authors: Fragiadakis D. , Roland C. M. , Casalini R.
Published: April 2010

The dielectric spectra of most simple liquids are characterized by two relaxation processes: (i) the α-process, an intense, broad non-Debye relaxation with a non-Arrhenius temperature dependence and (ii) a β process, evident mainly below the glass transition and having nearly Arrhenius temperature behavior. However, the dielectric spectra of monoalcohols show three processes: two that resemble those of normal liquids and a third very intense Debye peak at lower frequencies, which is non-Arrhenius. Interestingly, this third process is not observed with other techniques such as light scattering and mechanical spectroscopy. There is a disagreement in the literature concerning the nature of this third relaxation. We investigated 2-ethyl-1-hexanol under high pressures (up to ∼1.4 GPa) over a broad range of temperatures. The Debye process, which is the slowest, is strongly affected by pressure. At higher pressures the relaxation times and intensities of the two non-Arrhenius relaxations become more nearly equal. In light of these results, we propose a modified interpretation of the relaxation processes and their underlying structures in monoalcohols.
Pick, break, and placement of one-dimensional nanostructures for direct assembly and integration
Authors: Sosnowchik Brian D. , Chang Jiyoung , Lin Liwei
Published: April 2010

A direct, simple, and versatile assembly method for the manipulation of one-dimensional nanostructures and their integration with microscale devices has been demonstrated. Using a probe station with an unbiased tungsten probe, the facile process has been employed to accurately pick, break, and place individual titanium dioxide nanoswords and zinc oxide nanowires under a room-temperature, dry environment. The surface morphology of the nanostructures, probe tips, and adhesion forces were characterized. As such, the technique could enable the rapid assembly of individual nanostructures with complementary metal-oxide-semiconductor-compatible or complex microscale devices.
Right-angle piezoelectric cantilever with improved energy harvesting efficiency
Authors: Xu Jia Wen , Shao Wei Wei , Kong Fan Rang , Feng Zhi Hua
Published: April 2010

This paper reports a piezoelectric device based on a cantilever with an extended auxiliary part that forms a right angle with the basic part. Theoretical analyses and experiments support that, by using such a device, uniform strain distribution in piezoelectric element surfaces can be obtained, and thus the piezoelectric materials can be used more efficiently. A piezoelectric element on a right-angle cantilever can generate a useful power twice that of a traditional cantilever under the same strain limitation.
On anomalous diffusion in a plasma in velocity space
Authors: Trigger S. A. , Ebeling W. , van Heijst G. J. F. , Schram P. P. J. M. , Sokolov I. M.
Published: April 2010

The problem of anomalous diffusion in momentum space is considered for plasmalike systems on the basis of a new collision integral, which is appropriate for consideration of the probability transition function (PTF) with long tails in momentum space. The generalized Fokker–Planck equation for description of diffusion (in momentum space) of particles (ions, grains, etc.) in a stochastic system of light particles (electrons or electrons and ions, respectively) is applied to the evolution of the momentum particle distribution in a plasma. In a plasma the developed approach is also applicable to the diffusion of particles with an arbitrary mass relation due to the small characteristic momentum transfer. The cases of an exponentially decreasing (including a Boltzmann-like) kernel in the PTF in momentum space, as well as more general kernels, which create anomalous diffusion in velocity space due to the long tail in the PTF, are considered. Effective friction and diffusion coefficients for plasmalike systems are found.
Plasmonic nanoparticle enhanced photocurrent in GaN/InGaN/GaN quantum well solar cells
Authors: Pryce Imogen M. , Koleske Daniel D. , Fischer Arthur J. , Atwater Harry A.
Published: April 2010

We demonstrate enhanced external quantum efficiency and current-voltage characteristics due to scattering by 100 nm silver nanoparticles in a single 2.5 nm thick InGaN quantum well photovoltaic device. Nanoparticle arrays were fabricated on the surface of the device using an anodic alumina template masking process. The Ag nanoparticles increase light scattering, light trapping, and carrier collection in the III-N semiconductor layers leading to enhancement of the external quantum efficiency by up to 54%. Additionally, the short-circuit current in cells with 200 nm p-GaN emitter regions is increased by 6% under AM 1.5 illumination. AFORS-Het simulation software results were used to predict cell performance and optimize emitter layer thickness.
A theoretical study of H2 dissociation on (3×3)R30°CO/Ru(0001)
Authors: Groot I. M. N. , Juanes-Marcos J. C. , Olsen R. A. , Kroes G. J.
Published: April 2010

We have studied the influence of preadsorbed CO on the dissociative adsorption of H2 on Ru(0001) with density functional theory calculations. For a coverage of 1/3 ML CO, we investigated different possible reaction paths for hydrogen dissociation using nudged elastic band and adaptive nudged elastic band calculations. One reaction path was studied in detail through an energy decomposition and molecular orbital type of analysis. The minimum barrier for H2 dissociation is found to be 0.29 eV. At the barrier the H–H bond is hardly stretched. Behind this barrier a molecular chemisorption minimum is present. Next, the molecule overcomes a second barrier, with a second local chemisorption minimum behind it. To finally dissociate to chemisorbed atoms, the molecule has to overcome a third barrier. To move along the reaction path from reactants to products, the hydrogen molecule needs to rotate, and to significantly change its center-of-mass position. The procedure of mapping out reaction paths for H2 reacting on low-index surfaces of bare metals (computing two-dimensional elbow plots for fixed impact high-symmetry sites and H2 orientations parallel to the surface) does not work for H2+CO/Ru. The first barrier in the path is recovered, but the features of the subsequent stretch to the dissociative chemisorption minimum are not captured, because the molecule is not allowed to change its center-of-mass position or to rotate. The dissociative chemisorption of H2 on CO/Ru(0001) is endoergic, in contrast to the case of H2 on bare Ru(0001). The zero-point energy corrected energies of molecularly and dissociatively chemisorbed H2 are very close, suggesting that it may be possible to detect molecularly chemisorbed H2 on (3×3)R30°CO/Ru(0001). The presence of CO on the surface increases the barrier height to dissociation compared with bare Ru(0001). Based on an energy decomposition and molecular orbital analysis we attribute the increase in the barrier height mainly to an occupied-occupied interaction between the bonding H2 σg orbital and the (surface-hybridized) CO 1π orbitals, i.e., to site blocking. There is a small repulsive contribution to the barrier from the interaction between the H2 molecule and the Ru part of the CO covered Ru surface, but it is smaller than one might expect based on the calculations of H2 interacting with a clean Ru surface, and on calculations of H2 interacting with the CO overlayer only. Actually, the analysis suggests that the Ru surface as a subsystem is (slightly) more reactive for the reaction path studied with CO preadsorbed on it than without it. Thus, the results indicate that the influence of CO on H2 dissociation on Ru is not only a simple site-blocking effect, the electronic structure of the underlying Ru is changed.
Note: Galvanic isolated voltage source using a single photodiode
Authors: Stoican O. S.
Published: April 2010

A galvanic isolated voltage source able to provide several volts by using a single photodiode is described. A pulse-modulated laser beam is sent to a photodiode. By using a step-up transformer the amplitude of the variable voltage generated by the photodiode is increased. Adding a rectifier cell the variable voltage is converted back into a dc voltage.
X-shaped plasmonic antenna on a quantum cascade laser
Authors: Austin D. , Mullin N. , Luxmoore I. , Sandall I. C. , Cullis A. G. , Bismuto A. , Faist J. , Hobbs J. K. , Wilson L. R.
Published: April 2010

We report an x-shaped plasmonic antenna design patterned onto the gold coated facet of a mid-infrared quantum cascade laser. Using apertureless scanning near-field optical microscopy we measure a single enhanced region in the optical near-field at the center of the x-antenna, with a full-width-at-half-maximum of ∼100 nm for the operating wavelength of ∼8.8 μm. This design provides complete suppression of near-field signal away from the center, with concomitant improvements in imaging contrast expected. Our experimental results are also in good agreement with finite difference time domain simulations, which show a full-width-at-half-maximum of ∼80 nm.
Manufacturing of 50 kA superconducting transformer for ITER correction coil conductor test
Authors: Liu H. J. , Wu Y. , Ren Zh. B. , Wu S. T. , Shi Y. , Peng J. Q. , Chen J. L. , Long F. , Yu M. , Qian L.
Published: April 2010

To meet the specifications of International Thermonuclear Experimental Reactor correction coil (CC) conductor, a 50 kA superconducting transformer has been designed and manufactured to provide the short sample of the CC conductor the current. The transformer consists of two concentric layer-wound superconducting solenoids with the primary inside the secondary coil. In order to test the transformer, the two legs of the secondary coil were directly connected by superconducting cables. A 500 W/4.5 K refrigerator was used to provide the supercritical helium. The maximum current of 56.3 kA in the secondary coil loop was obtained.
Dispersion forces between solvated electrons
Authors: Chuev Gennady N.
Published: April 2010

Using the path integral centroid approach, we investigate dispersion interactions between electrons solvated in metal-ammonia solutions. We have argued that at finite metal concentrations, the behavior of the solvated electrons is controlled by these interactions. The latter result in a peculiar nonmetal-metal transition, which appears as a sharp dielectric enhancement and a mechanical instability of the system. Our results indicate also that the solvated electrons are to be considered as a two-component mixture consisting of localized and delocalized electrons beyond the critical density corresponding to this mechanical instability.
Heterogeneous crystallization of hard spheres on patterned substrates
Authors: Xu Wen-Sheng , Sun Zhao-Yan , An Li-Jia
Published: April 2010

We report a numerical investigation of the crystallization of monodisperse hard spheres on different patterned substrates. We find that the duration of a metastable fluid state, which may last for relatively long time in the homogeneous crystallization, can be deeply reduced or almost eliminated when a substrate is used as the seed of crystallization. In the presence of the square patterned substrate, which has the basic character of the body-centered cubic (bcc) crystal structure, a transient bcc crystal phase was observed, suggesting that the bcc structure could be possible to be stabilized by the square patterned substrates. The process of crystallization becomes complicated when the patterned substrate is incommensurate with the bulk crystal. Furthermore, a purely face-centered cubic or hexagonal close packed crystal phase with stacking faults can be generated by using a certain patterned substrate without other factors such as gravity.