bluuebunny/crossref_metadata_2025 huggingface dataset:
Hausaufgaben in der Paartherapie
Authors: Bodenmann Guy , Götz Christina
Published: March 2012

Zusammenfassung.Hausaufgaben spielen in der Paartherapie, unabhängig von deren theoretischer Ausrichtung, eine bedeutende Rolle. Dabei variieren je nach therapeutischem Ansatz die Form, der Inhalt, die Häufigkeit und der Zeitpunkt im therapeutischen Prozess, wann Hausaufgaben aufgegeben werden. Bezüglich Funktion der Hausaufgabe gibt es deutlich weniger Differenzen und die meisten Richtungen der Paartherapie anerkennen den Nutzen von Hausaufgaben zur Gewinnung neuer Einsichten oder zur Vertiefung und Festigung von neuen Verhaltensweisen, Kognitionen oder Emotionen. Gerade in der Verhaltenstherapie mit Paaren spielen Hausaufgaben eine zentrale Rolle. Sie sind häufig inhaltlich und formal strukturiert und werden im Gegensatz zu anderen Ansätzen als verpflichtender Beitrag des Paares zum Gelingen der Therapie angesehen. Dieser Artikel versucht einen Überblick über den Einsatz und die Bedeutung von Hausaufgaben in der Paartherapie sowie über verschiedene Formen und Handhabungsmöglichkeiten zu geben. Schwierigkeiten mit Hausaufgaben im Rahmen der Paartherapie werden ebenfalls thematisiert.
Structure, temporal evolution, and heat flux estimates from the Lucky Strike deep‐sea hydrothermal field derived from seafloor image mosaics
Authors: Barreyre Thibaut , Escartín Javier , Garcia Rafael , Cannat Mathilde , Mittelstaedt Eric , Prados Ricard
Published: March 2012

Here we demonstrate with a study of the Lucky Strike hydrothermal field that image mosaicing over large seafloor areas is feasible with new image processing techniques, and that repeated surveys allow temporal studies of active processes. Lucky Strike mosaics, generated from >56,000 images acquired in 1996, 2006, 2008 and 2009, reveal the distribution and types of diffuse outflow throughout the field, and their association with high‐temperature vents. In detail, the zones of outflow are largely controlled by faults, and we suggest that the spatial clustering of active zones likely reflects the geometry of the underlying plumbing system. Imagery also provides constraints on temporal variability at two time‐scales. First, based upon changes in individual outflow features identified in mosaics acquired in different years, we document a general decline of diffuse outflow throughout the vent field over time‐scales up to 13 years. Second, the image mosaics reveal broad patches of seafloor that we interpret as fossil outflow zones, owing to their association with extinct chimneys and hydrothermal deposits. These areas encompass the entire region of present‐day hydrothermal activity, suggesting that the plumbing system has persisted over long periods of time, loosely constrained to hundreds to thousands of years. The coupling of mosaic interpretation and available field measurements allow us to independently estimate the heat flux of the Lucky Strike system at ∼200 to 1000 MW, with 75% to >90% of this flux taken up by diffuse hydrothermal outflow. Based on these heat flux estimates, we propose that the temporal decline of the system at short and long time scales may be explained by the progressive cooling of the AMC, without replenishment. The results at Lucky Strike demonstrate that repeated image surveys can be routinely performed to characterize and study the temporal variability of a broad range of vent sites hosting active processes (e.g., cold seeps, hydrothermal fields, gas outflows, etc.), allowing a better understanding of fluid flow dynamics from the sub‐seafloor, and a quantification of fluxes.
Co‐seismic deformation of deep slabs based on summed CMT data
Authors: Bailey Iain W. , Alpert Lisa A. , Becker Thorsten W. , Miller Meghan S.
Published: March 2012

We assess the co‐seismic deformation inferred from earthquake moment tensor solutions for subducting slabs at depths greater than 50 km globally. We rotate each moment tensor into a local slab reference frame, then sum tensors within 50 km depth bins to approximate long term deformation characteristics. This builds upon previous analyses by using the up‐to‐date global Centroid Moment Tensor catalog, incorporating a more complete slab geometry, and focusing on the 3‐D aspects of slab deformation. Results show a general consistency with Isacks and Molnar (1969), who found that most slabs can be divided into intermediate‐extensional, intermediate‐extensional‐deep‐compressional, and intermediate to deep‐compressional categories. Exceptions to these three categories can be related to slab bending in the top 100 km, plate convergence that is oblique to the trench normal direction, and regions of higher focal mechanism heterogeneity. The regions of higher focal mechanism heterogeneity appear where there are along‐strike changes in slab geometry and/or evidence of double‐seismic zones. We find that the sense of deformation in the intermediate strain axis direction is opposite to that of the down‐dip direction, in agreement with Kuge and Kawakatsu (1993). By quantitative comparison to numerical models of global mantle flow, we show that these observations are consistent with deformation of viscous slabs responding to their own negative buoyancy and an upper to lower mantle viscosity increase.
Whistler mode bursts in the Venus ionosphere due to lightning: Statistical properties using Venus Express magnetometer observations
Authors: Daniels J. T. M. , Russell C. T. , Strangeway R. J. , Wei H. Y. , Zhang T. L.
Published: March 2012

The Venus Express mission has completed over four years in polar orbit about Venus with periapsis altitudes as low as 180 km. On each orbit around periapsis the fluxgate magnetometer samples the magnetic field at 128 Hz. The data reveal short‐lived bursts with peak‐to‐peak amplitudes up to 1.5 nT in the frequency range 42 to 60 Hz. These signals are whistler mode waves with burst durations of about 100 ms and Poynting vectors similar to terrestrial whistler mode signals generated by atmospheric lightning when detected in the ionosphere. We have examined the occurrence of these bursts as a function of background magnetic field strength, altitude, latitude and local time. The burst rates are highest for magnetic fields of 15–30 nT, at altitudes near 215 km, and at local times near the terminators. The characteristics of these signals are consistent with generation in the dynamic Venus atmosphere, entry into the ionosphere, propagation along the ionospheric magnetic field, and ultimately damping in the ionospheric plasma.
Using hilltop curvature to derive the spatial distribution of erosion rates
Authors: Hurst Martin D. , Mudd Simon M. , Walcott Rachel , Attal Mikael , Yoo Kyungsoo
Published: March 2012

Erosion rates dictate the morphology of landscapes, and therefore quantifying them is a critical part of many geomorphic studies. Methods to directly measure erosion rates are expensive and time consuming, whereas topographic analysis facilitates prediction of erosion rates rapidly and over large spatial extents. If hillslope sediment flux is nonlinearly dependent on slope then the curvature of hilltops will be linearly proportional to erosion rates. In this contribution we develop new techniques to extract hilltop networks and sample their adjacent hillslopes in order to test the utility of hilltop curvature for estimating erosion rates using high‐resolution (1 m) digital elevation data. Published and new cosmogenic radionuclide analyses in the Feather River basin, California, suggest that erosion rates vary by over an order of magnitude (10 to 250 mm kyr−1). Hilltop curvature increases with erosion rates, allowing calibration of the hillslope sediment transport coefficient, which controls the relationship between gradient and sediment flux. Having constraints on sediment transport efficiency allows estimation of erosion rates throughout the landscape by mapping the spatial distribution of hilltop curvature. Additionally, we show that hilltop curvature continues to increase with rising erosion rates after gradient‐limited hillslopes have emerged. Hence hilltop curvature can potentially reflect higher erosion rates than can be predicted by hillslope gradient, providing soil production on hilltops can keep pace with erosion. Finally, hilltop curvature can be used to estimate erosion rates in landscapes undergoing a transient adjustment to changing boundary conditions if the response timescale of hillslopes is short relative to channels.
A sub‐grid scale closure for nonlinear hillslope sediment transport models
Authors: Ganti Vamsi , Passalacqua Paola , Foufoula‐Georgiou Efi
Published: March 2012

Hillslope sediment transport models express the sediment flux at a point as a function of some topographic attributes of the system, such as slope, curvature, soil thickness, etc., at that point only (referred here as “local” transport models) or at an appropriately defined vicinity of that point (referred here as “nonlocal” transport models). Typically, topographic attributes are computed from digital elevation data (DEMs) and thus their estimates depend on the DEM resolution (1 m, 10 m, 90 m, etc.) rendering any sediment flux computation scale‐dependent. Often calibration compensates for this scale‐dependence resulting in effective parameterizations with limited physical meaning. In this paper, we demonstrate the scale‐dependence of local nonlinear hillslope sediment flux models and derive a subgrid scale closure via upscaling. We parameterize the subgrid scale closure in terms of the low resolution, resolved topographic attributes of the landscape, thus allowing the reliable computation of a scale‐independent sediment flux from low resolution digital elevation data. We also show that the accuracy of the derived subgrid scale closure model depends on the dimensionless erosion rate and the dimensionless relief of any given basin. Finally, we present theoretical arguments and demonstrate that the recently proposed nonlocal sediment flux models are scale‐independent. These concepts are demonstrated via an application on a small basin (MR1) of the central Oregon Coast Range using high‐resolution lidar topographic data.
Wide Area RTK: A satellite navigation system based on precise real‐time ionospheric modelling
Authors: Juan J. M. , Sanz J. , Hernández‐Pajares M. , Samson J. , Tossaint M. , Aragón‐Àngel A. , Salazar D.
Published: March 2012

The Wide Area Real Time Kinematic (WARTK) is an augmentation system concept for multi‐frequency users based on precise real‐time ionospheric modeling. It is able to provide a high accuracy and integrity GNSS positioning service over continental areas using the infrastructure of a network of permanent ground monitor stations, such as the European Geostationary Navigation Overlay Service (EGNOS) network of Ranging and Integrity Monitoring Stations (RIMS) in Europe. In this way, it allows an additional benefit to be obtained from these reference stations, that is, the network has the potential to support two independent systems: a satellite‐based augmentation system, such as EGNOS, and a high‐precision positioning service, based on WARTK. Indeed, thanks to the accuracy of the ionospheric corrections provided, WARTK users have available in real‐time an extra constraint per satellite between the carrier phase ambiguities, which helps solve them quickly. Once such ambiguities have been solved, the GNSS user obtains navigation accurate to within 20 cm at the 95th percentile (about 10 cm RMS). Moreover, this precise positioning is achieved in a few minutes (with two frequency signals) or in a single epoch, after initial convergence of the tropospheric delay (with three frequency signals), even up to hundreds of kilometers away from the nearest reference station. While previous WARTK research has been devoted to implementing the concept and assessing its feasibility, considering in particular the accuracy achievable, the work reported in this paper focused on consolidating the results by analyzing a large and representative data set, and on deeper analysis of the integrity issue. It was carried out in the context of the Multi‐constellation Regional System (MRS) project, within the European Space Agency GNSS Evolution Programme, with the aim of designing a high accuracy service for GPS and/or Galileo. Three months of actual data, from more than 25 permanent GPS stations in Europe, have been processed (some of them as a roving user), for high‐, mid‐ and low‐solar cycle conditions (in 2002, 2004 and 2006 respectively). In addition, several ionospheric storms occurred during the selected periods, withDstvalues reaching up to −150 nT. Results based on these data show that user domain integrity was maintained for baselines of up to 400 km. At the 95th percentile, the daily horizontal and vertical position errors were 20 and 30 cm, respectively, and the corresponding protection levels were about 1 and 2 m. The convergence time was around 5 minutes with actual GPS constellation data. The benefits of using a multi‐constellation system were also studied, with simulated GPS and three‐frequency Galileo data, showing that it is possible to reduce the convergence time to a few seconds.
Program focuses on climate of the Mediterranean region
Authors: Lionello Piero , Gacic Miroslav , Gomis Damià , Garcia‐Herrera Ricardo , Giorgi Filippo , Planton Serge , Trigo R. , Theocharis A. , Tsimplis Michael N. , Ulbrich Uwe , Xoplaki E.
Published: March 2012

Located between subtropical and mid‐latitude climates, the Mediterranean region acts as a transition area and is very sensitive to global climate change: As global temperatures have risen, the Mediterranean region has warmed, particularly in the west and in the summer, where surface temperatures in some locations increased at a rate greater than 0.4°C per decade during the second half of the twentieth century. Model simulations give a collective picture of substantial drying and warming of the Mediterranean region in the future, especially summer, with average precipitation expected to decrease by 25–30% and temperatures expected to rise by 4°–5°C by the end of this century, approximately. These changes will likely be accompanied by increased intensity in heat waves and dry spells along with important changes in Mediterranean water masses, which will become warmer and saltier. This future climate change can pose very serious problems to ecosystems and human societies.
Earthquake‐triggered avalanche altered glacier flow
Authors: Balcerak Ernie
Published: March 2012

Landslides are common in areas with mountain glaciers and could affect the movement of glaciers. Shugar et al. used satellite radar imagery and numerical modeling to investigate the effects of earthquake‐triggered avalanches on the Black Rapids Glacier in central Alaska. Three avalanches were triggered there by the 2002 magnitude 7.9 Denali earthquake. The researchers compared prelandslide and postlandslide ice velocities. They found that after the avalanches, ice velocity initially increased by up to 14% in the area above the debris‐covered area and by 44% in the debris‐covered area. The lower margin of the debris sheet sped up by more than 100%. After several years the ice velocities gradually decreased to their prelandslide values, and the debris‐covered part of the glacier moved with a uniform velocity. The authors' numerical model supports their interpretation that the changes in velocity were caused by the landslides. (Journal of Geophysical Research‐Earth Surface, doi:10.1029/2011JF002011, 2012)
Measuring ocean circulation in the North Atlantic
Authors: Balcerak Ernie
Published: March 2012

The Atlantic Meridional Overturning Circulation (AMOC), which carries warm water from the tropics to northern latitudes and brings dense, cold water back southward, is a major conveyer of heat and an important element of the climate system. Some scientists have worried that AMOC may slow down as Earth's climate warms, but more measurements of the current state of ocean circulation are needed to fully understand AMOC dynamics. Using yearly hydrographic measurements in the North Atlantic at 59.5°N latitude and satellite altimetry data from 2002 through 2008, Sarafanov et al. assessed the mean state of the summer circulation in between Cape Farewell in Greenland and the Greenland‐Scotland ridge and quantified transports in the upper ocean, middepth, and deep currents. The measurements contribute to the understanding of ocean circulation dynamics in the northern North Atlantic and provide a benchmark for numerical models. (Journal of Geophysical Research‐Oceans, doi:10.1029/2011JC007572, 2012)
Fluid flow in subducting slabs
Authors: Balcerak Ernie
Published: March 2012

When subducting oceanic plates descend into the Earth's mantle, they bring a significant amount of water with them that is subsequently released at depths.Faccenda et al. used a thermomechanical model of a subducting dehydrating oceanic plate to study fluid flow in the dehydrating slab. They show that as a slab bends and unbends as it descends, stresses drive fluids toward a layer of lower pressure in the center of the plate. Together with the dehydrating oceanic crust, this fluid‐rich layer forms a double hydrated zone, which the authors believe corresponds to 20‐ to 30‐kilometer‐thick regions called double seismic zones that have been observed in seismological studies.
A stochastic parameterization of non‐orographic gravity waves: Formalism and impact on the equatorial stratosphere
Authors: Lott F. , Guez L. , Maury P.
Published: March 2012

A formalism is proposed to represent a broadband spectrum of Gravity Waves (GWs) via the superposition of a large ensemble of statistically independent monochromatic ones. To produce this large ensemble at a reasonable numerical cost, we use the fact that the life cycles of the waves needed to be parameterized in General Circulation Models (GCMs) have time scales that largely exceed the time step of the model. We can therefore launch few waves with characteristics chosen randomly at each time step, and make them having an effect on a longer time scale by applying an AR1 relation between the gravity waves drag at a given time and that at the next time step. The stochastic GW parameterization is applied to a GCM in the tropics, and its additional drag causes a realistic Quasi‐Biennial Oscillation (QBO). The more realistic wind structure also results in a better representation of the large scale equatorial waves, like the Rossby Gravity Waves (RGWs) with periods around 4–5 day.
Hydrogenase: the next antibiotic target?
Authors: Nie Wei , Tang Hao , Fang Zheng , Chen Jiquan , Chen Haili , Xiu Qingyu
Published: March 2012

The struggle to control infectious diseases has become increasingly difficult due to resistance to current antibiotics and the co-existence of multiplying and non-multiplying bacteria, which makes it an urgent task to discover new antibiotic targets and to develop new antibiotics. Hydrogenases are found in micro-organisms belonging to the archaea and bacteria domains, which can catalyse the reversible oxidation of hydrogen gas (H2↔2H++2e) and play pleiotropic roles in microbial survival. Studies have shown that H2 is a potent antioxidant and can selectively neutralize OH• (hydroxyl radicals). OH•, however, has been implicated as one of the mechanisms whereby bactericidal antibiotics and professional phagocytes kill bacteria. Thus we have enough reason to speculate that hydrogenases and H2 are conducive to increasing the virulence and antibiotic resistance of bacteria, and hydrogenase inhibitors would help control bacterial infection.
Shifts in plasmon resonance due to charging of a nanodisk array in argon plasma
Authors: Ian Lapsley Michael , Shahravan Anaram , Hao Qingzhen , Krishna Juluri Bala , Giardinelli Stephen , Lu Mengqian , Zhao Yanhui , Chiang I-Kao , Matsoukas Themis , Jun Huang Tony
Published: March 2012

A method for generating charge-induced plasmonic shifts, using argon plasma to charge nanoparticle arrays, is presented. Particles develop a negative charge, due to enhanced collisions with high-temperature electrons, in low-temperature plasmas. The negative charge generated causes a blue shift in the localized surface plasmon resonance. The dynamics of the shift were recorded and discussed. This effect could be used as a real-time method for studying the dynamics for charging in plasma.
Ferromagnetic InMnSb multi-phase films study by aberration-corrected (scanning) transmission electron microscopy
Authors: Lari Leonardo , Lea Stephen , Feeser Caitlin , Wessels Bruce W. , Lazarov Vlado K.
Published: March 2012

In this work we report a structural and compositional study of ferromagnetic In0.78Mn0.22Sb films correlated to the magnetic properties as determined by superconducting quantum interference device magnetometer. The epilayers grown by metalorganic vapor phase epitaxy on GaAs(001) substrates showed two active magnetic components with Curie temperatures of approximately 300 K and in excess of 570 K. Secondary phases driven by the high manganese concentration (10 at. %) were identified by high-resolution (scanning) transmission electron microscopy imaging and energy dispersive X-ray spectroscopy. Most of the Mn was found to be incorporated in metallic manganese nanoprecipitates surrounded by an InMnSb matrix with Mn at 1 at. % concentration. The origin of the two Curie temperatures of the film is associated with the presence of three magnetic components: hexagonal MnSb nanoprecipitates, non-stoichiometric MnAsSb, and the InMnSb matrix.
Development of a highly efficient brushless dc motor utilizing both radial and axial air gaps
Authors: Kang K. J. , Jang G. H. , Sung S. J. , Chang J. H.
Published: March 2012

This research proposes an effective structure for a brushless dc motor utilizing both radial and axial air gaps. The proposed motor generates torque in both the radial and axial air gaps, while the conventional motor generates torque only in the radial air gap. The proposed motor was optimized to minimize the electromagnetic loss of the motor to increase the effective air gap length and fill-factor of the coil while decreasing the saturation of the core at the same time. The electromagnetic loss was reduced by 35% in comparison with a conventional motor.
Liver cancer immunoassay with magnetic nanoparticles and MgO-based magnetic tunnel junction sensors
Authors: Lei Z. Q. , Li L. , Li G. J. , Leung C. W. , Shi J. , Wong C. M. , Lo K. C. , Chan W. K. , Mak C. S. K. , Chan S. B. , Chan N. M. M. , Leung C. H. , Lai P. T. , Pong P. W. T.
Published: March 2012

We have demonstrated the detection of alpha-fetoprotein (AFP) labeled with magnetic nanoparticles (MNPs) using MgO-based magnetic tunnel junction (MTJ) sensors. AFP is an important hepatic tumor biomarker and the detection of AFP has significant applications for clinical diagnostics and immunoassay for early-stage liver cancer indications. In this work, MgO-based MTJ sensors and 20-nm iron-oxide magnetic nanoparticles (MNPs) were used for detecting AFP antigens by a sandwich-assay configuration. The MTJ sensors with a sensing area of 4 × 2 μm2 possess tunneling magnetoresistance (TMR) of 122% and sensitivity of 0.95%/Oe at room temperature. The target AFP antigens of three concentrations were successfully detected, and the experimental data indicate that the resistance variations of the MTJ sensor increased with the AFP concentration ratios proportionally. These results demonstrate that MgO-based MTJ sensors together with MNPs are a promising biosensing platform for liver cancer immunoassay.
A permalloy zigzag structure based magnetic bio-sensor
Authors: Ger Tzong-Rong , Xu You-Ren , Huang Hao-Ting , Wei Zung-Hang
Published: March 2012

A magnetic fluid consisting of Fe3O4 magnetic nanoparticles is embedded inside cells by intracellular uptake. A micro-fabricated magnetic zigzag-shaped surface structure is studied for use as a biosensor. We have developed a MOKE magnetometer based methodology to measure the different hysteresis loop signals between cells with and without being placed on zigzag sensors. Adding the magnetic cells on the structure decreases the coercivity from the magneto-optical Kerr effect (MOKE) signal of zigzag magnetic thin films because of the magnetic properties of superparamagnetic nanoparticles. The magnetoresistance measurement observed is that the switching fields of the zigzag structure with magnetic cells are significantly increased compared to the case without cells in the hard axis of the external field applied.
Energy barrier distribution for dispersed mixed oxide magnetic nanoparticles
Authors: Okuda Mitsuhiro , Eloi Jean-Charles , Sarua Andrei , Ward Jones Sarah E. , Schwarzacher Walther
Published: March 2012

Mixed Fe/Co oxide nanoparticles, diameter 8 nm, were prepared using the protein ferritin as a template and characterized by transmission electron microscopy (TEM) and Raman spectroscopy. We show that the latter effectively distinguishes between magnetite (Fe3O4), maghemite (γ-Fe2O3) and Co ferrite (CoxFe3-xO4). Zero-field-cooled susceptibility measurements show isolated magnetite nanoparticles have a blocking temperature TB = 18 ± 1 K, but that adding 0.5% Co raises TB to 30 K. Data for thermal relaxation from saturation obey a T ln(t/τ0) scaling, enabling us to determine the energy barrier distributions for the dispersed nanoparticles. For Fe oxide only a single peak was found. However, with the addition of only 0.5% Co a second component is observed that decreases rapidly with increasing energy.
Thermo-mechanical sensitivity calibration of nanotorsional magnetometers
Authors: Losby Joseph , Burgess Jacob A. J. , Diao Zhu , Fortin David C. , Hiebert Wayne K. , Freeman Mark R.
Published: March 2012

We report on the fabrication of sensitive nanotorsional resonators, which can be utilized as magnetometers for investigating the magnetization dynamics in small magnetic elements. The thermo-mechanical noise is calibrated with the resonator displacement in order to determine the ultimate mechanical torque sensitivity of the magnetometer.
Magnetic anisotropy in composite CoFe2O4-BiFeO3 ultrathin films grown by pulsed-electron deposition
Authors: Comes Ryan , Khokhlov Mikhail , Liu Hongxue , Lu Jiwei , Wolf Stuart A.
Published: March 2012

Many works have demonstrated perpendicular magnetic anisotropy in CoFe2O4-BiFeO3 (CFO-BFO) composites, which is commonly believed to originate from out-of-plane compressive strain in the CFO pillars due to the lattice mismatch with the BFO matrix. Others have shown that the pillar−matrix interface in similar NiFe2O4-BFO composites is fully relaxed. To study the origin of the magnetic anisotropy, composite films were grown on SrTiO3 with thicknesses ranging from 13 to 150 nm via pulsed electron deposition. In-plane compressive strain in the pillars is found for thinner samples, which induces in-plane magnetoelastic anisotropy. A model for the origin of this previously unreported strain is proposed and the results are contrasted with the thicker composite films found in the literature.
Longitudinal dynamic hysteresis in single-domain particles
Authors: Landi G. T. , Santos A. D.
Published: March 2012

We present results for longitudinal dynamic hysteresis in single domain particles with uniaxial anisotropy. The combined influence of temperature, field-sweeping frequency, and field amplitude is discussed in detail. A novel and efficient numerical method is proposed, based on the direct solution of the infinite hierarchy of differential recurrence relations obtained from averaging over the stochastic realizations of the magnetic Langevin equation.
Critical magnetic fields in the rutheno-cuprates Ru(1−x)NbxSr2Eu1.4Ce0.6Cu2O10
Authors: Botello-Zubiate M. E. , Matutes-Aquino J. A. , Ayala-Valenzuela O. E. , Jaime M.
Published: March 2012

II-type superconducting rutheno-cuprates are both interesting and challenging systems where there is a coexistence of superconductivity and magnetism, so far poorly understood. The magnetic transitions that occur before the superconducting transition in Ru-1212 are simpler and better understood than those found in Ru-1222. In this work, polycrystalline Ru(1−x)NbxSr2Eu1.4Ce0.6Cu2O10 samples (Ru-1222) with x = 0, 0.2, 0.4, and 0.6, were prepared by conventional solid state reaction using stoichiometric amounts of high purity oxide powders: RuO2, Nb2O5, SrCO3, Eu2O3, CeO2, and CuO. The phases were identified by x-ray diffraction. From electrical resistance measurements as a function of the applied magnetic field at different temperatures (4 to 40 K), the Hc2 critical field or a lower limit of this was determined for each composition. At the lower measurement temperatures, from T = 4 K to T = 20 K, it was only possible to set a lower limit for the critical magnetic field, Hc2, of 140 kOe for compositions x = 0 and 0.2, while for compositions x = 0.4 and 0.6 the critical magnetic field, Hc2, were 110 and 84 kOe, respectively at T = 4 K. The dependence of these critical magnetic fields, Hc2, with temperature and composition is discussed.
Isothermal entropy changes in nanocomposite Co:Ni67Cu33
Authors: Michalski S. , Skomski R. , Li X.-Zh. , Le Roy D. , Mukherjee T. , Binek Ch. , Sellmyer D. J.
Published: March 2012

The temperature-dependent magnetic properties of artificial rare-earth, free-magnetic nanostructures are investigated for magnetic cooling. We consider two-phase nanocomposites, where 2 nm nanoclusters of cobalt are embedded in a Ni67Cu33 matrix. Several composite films were produced by cluster deposition. The average Co nanocluster size can be tuned by varying the deposition conditions. Isothermal magnetization curves were measured at various temperatures 150 K < T < 340 K in steps of 10 K. The isothermal entropy changes ΔS were calculated using the Maxwell relation. The entropy changes measured were, –ΔS = 0.15 J/kg·K in a field change of 1 T at 260 K and 0.72 J/kg·K in a field change of 7 T at 270 K.
Inertial focusing dynamics in spiral microchannels
Authors: Martel Joseph M. , Toner Mehmet
Published: March 2012

This report details a comprehensive study of inertial focusing dynamics and particle behavior in low aspect ratio (h/w ∼ 1/1 to 1/8) spiral microchannels. A continuum of particle streak behavior is shown with longitudinal, cross-sectional, and velocity resolution, yielding a large analyzed parameter space. The dataset is then summarized and compared to prior results from both straight microchannels and other low aspect ratio spiral microchannel designs. Breakdown of focusing into a primary and secondary fluorescent streak is observed in the lowest aspect ratio channels at high average downstream velocities. Streak movement away from the theoretically predicted near inner wall equilibrium position towards the center of the channel at high average downstream velocities is also detailed as a precursor to breakdown. State diagrams detail the overall performance of each device including values of the required channel lengths and the range of velocities over which quality focusing can be achieved.
Continuum limit frozen Gaussian approximation for the reduced thermal density matrix of dissipative systems
Authors: Conte Riccardo , Pollak Eli
Published: March 2012

A continuum limit frozen Gaussian approximation is formulated for the reduced thermal density matrix for dissipative systems. The imaginary time dynamics is obtained from a novel generalized Langevin equation for the system coordinates. The method is applied to study the thermal density in a double well potential in the presence of Ohmic-like friction. We find that the approximation describes correctly the delocalization of the density due to quantization of the vibrations in the well. It also accounts for the friction induced reduction of the tunneling density in the barrier region.
Validation of electron temperature gradient turbulence in the Columbia Linear Machine
Authors: Fu X. R. , Horton W. , Xiao Y. , Lin Z. , Sen A. K. , Sokolov V.
Published: March 2012

The electron temperature gradient (ETG) mode, which is a universal mechanism for turbulent electron thermal transport in plasmas, is produced and verified in steady-state, collisionless hydrogen plasma of the Columbia Linear Machine. Electron temperature profiles with strong gradients are produced by DC acceleration in a remote biased mesh and subsequent thermalization. Finite amplitude ∼5%, steady-state oscillations at ∼0.3-0.5MHz (in the plasma frame), with azimuthal wave numbers m∼14-16 and parallel wave number k∥∼0.01cm-1 are measured. The massively parallel gyrokinetic toroidal code is used to study these modes. The results show that in the linear phase, the dispersion relation is consistent with kinetic theory. In the nonlinear stage, very strong nonlinear wave coupling gives rise to an inverse cascade of the energy from the fastest growing high-m modes to low-m nonlinear oscillations, which are consistent with the measured azimuthal mode spectrum. The radial structure of the fluctuation also agrees with the experiment. An inward radial shift of the peak of the potential fluctuation occurs during the nonlinear saturation and fluctuation fingers extend radially out to the edge plasma. Three-wave coupling mechanism is involved in the saturation of ETG modes. The simulations show a power law spectrum of the turbulence which suggests that the renormalization theory is appropriate to interpret the turbulent thermal flux.
Scatter in nonlinear ultrasonic measurements due to crystallographic orientation change induced anisotropy in harmonics generation
Authors: Mukhopadhyay Amretendu , Sarkar Rajdeep , Punnose Sony , Valluri Jitendra , Nandy T. K. , Balasubramaniam Krishnan
Published: March 2012

Present study endeavors to establish the physical basis of an unprecedented trend in scatter, observed in nonlinear ultrasonic (NLU) parameter, associated with varying degree of crystallographic orientation change across crystallites in a polycrystalline material. It is shown that this scatter arises due to anisotropy in harmonics generation as a result of orientation change of slip systems in polycrystals with respect to the wave propagation direction. A near α titanium alloy has been taken as a model alloy to demonstrate this effect of crystallographic orientation change vis-à-vis change in the orientation of slip systems. Scale of crystal orientation change is shown to have a strong correlation with the degree of scatter in NLU measurements. Further, the study establishes the dominating effect of the scale of crystalline orientation change on harmonics generation as compared to variation in other microstructural parameters such as dislocation density, interface structure etc. Frequency distribution analysis of the scatter indicates that the distribution depends on the colony size which exhibits a linear correlation with standard deviation value. The dislocation string vibration model has been extended for harmonics generation in polycrystalline aggregates to explain the trend in the scatter during measurement of NLU parameter in the material.
Band gap tunability of magneto-elastic phononic crystal
Authors: Bou Matar O. , Robillard J. F. , Vasseur J. O. , Hladky-Hennion A.-C. , Deymier P. A. , Pernod P. , Preobrazhensky V.
Published: March 2012

The possibility of control and tuning of the band structures of phononic crystals offered by the introduction of an active magnetoelastic material and the application of an external magnetic field is studied. Two means to obtain large elastic properties variations in magnetoelastic material are considered: Giant magnetostriction and spin reorientation transition effects. A plane wave expansion method is used to calculate the band structures. The magnetoelastic coupling is taken into account through the consideration of an equivalent piezomagnetic material model with elastic, piezomagnetic, and magnetic permeability tensors varying as a function of the amplitude and orientation of the applied magnetic field. Results of contactless tunability of the absolute bandgap are presented for a two-dimensional phononic crystal constituted of Terfenol-D square rod embedded in an epoxy matrix.
A single-solenoid pulsed-magnet system for single-crystal scattering studies
Authors: Islam Zahirul , Capatina Dana , Ruff Jacob P. C. , Das Ritesh K. , Trakhtenberg Emil , Nojiri Hiroyuki , Narumi Yasuo , Welp Ulrich , Canfield Paul C.
Published: March 2012

We present a pulsed-magnet system that enables x-ray single-crystal diffraction in addition to powder and spectroscopic studies with the magnetic field applied on or close to the scattering plane. The apparatus consists of a single large-bore solenoid, cooled by liquid nitrogen. A second independent closed-cycle cryostat is used for cooling samples near liquid helium temperatures. Pulsed magnetic fields close to ∼30 T with a zero-to-peak-field rise time of ∼2.9 ms are generated by discharging a 40 kJ capacitor bank into the magnet coil. The unique characteristic of this instrument is the preservation of maximum scattering angle (∼23.6°) on the entrance and exit sides of the magnet bore by virtue of a novel double-funnel insert. This instrument will facilitate x-ray diffraction and spectroscopic studies that are impractical, if not impossible, to perform using split-pair and narrow-opening solenoid magnets. Furthermore, it offers a practical solution for preserving optical access in future higher-field pulsed magnets.
Transmission electron microscopy of the amorphization of copper indium diselenide by in situ ion irradiation
Authors: Hinks J. A. , Edmondson P. D.
Published: March 2012

Copper indium diselenide (CIS), along with its derivatives Cu(In,Ga)(Se,S)2, is a prime candidate for use in the absorber layers of photovoltaic devices. Due to its ability to resist radiation damage, it is particularly well suited for use in extraterrestrial and other irradiating environments. However, the nature of its radiation hardness is not well understood. In this study, transmission electron microscopy (TEM) with in situ ion irradiation was used to monitor the dynamic microstructural effects of radiation damage on CIS. Samples were bombarded with 400 keV xenon ions to create large numbers of atomic displacements within the thickness of the TEM samples and thus explore the conditions under which, if any, CIS could be amorphized. By observing the impact of heavily damaging radiation in situ—rather than merely the end-state possible in ex situ experiments—at the magnifications allowed by TEM, it was possible to gain an understanding of the atomistic processes at work and the underlying mechanism that give rise to the radiation hardness of CIS. At 200 K and below, it was found that copper-poor samples could be amorphized and copper-rich samples could not. This difference in behavior is linked to the crystallographic phases that are present at different compositions. Amorphization was found to progress via a combination of one- and two-hit processes. The radiation hardness of CIS is discussed in terms of crystallographic structures/defects and the consequences these have for the ability of the material to recover from the effects of displacing radiation.
Electronic and optical properties of selected polymers studied by reflection electron energy loss spectroscopy
Authors: Tahir Dahlang , Tougaard Sven
Published: March 2012

We have determined the electronic and optical properties of six polymers: Polymethyl-methacrylate (PMMA), polyethylene (PE), polyvinyl chloride (PVC), polyester (PET), polypyrrole (PPY), and polyamide (PA6) for energy losses from 0 to 70 eV by analysis of reflection electron energy-loss spectroscopy (REELS) spectra. We found that the surface was easily damaged by the incident electron beam, in particular for energies above 500 eV. The damage results in new peaks in the bandgap region and the polymers become metallic. Great care was exerted to determine experimental conditions under which these effects are minimized. The REELS spectra were corrected for multiple inelastically scattered electrons with the QUASES-XS-REELS software to determine the effective inelastic-scattering cross sections. From these cross sections, we found that the band gaps for PMMA, PE, PVC, PET, PPY, and PA6 are 5.0 eV, 7.5 eV, 7.0 eV, 3.0 eV, 3.5 eV, and 5.1 eV, respectively. Quantitative analysis of the experimental cross sections was carried out by using the QUEELS-ɛ(k,ω)-REELS software to determine the dielectric function and optical properties. This is done by comparing the experimental REELS inelastic electron-scattering cross-section with a simulated cross section in which the only input is Im(−1/ɛ). The dielectric function is expressed as a sum of oscillators and the oscillator parameters are determined. Good agreement between the experimental and theoretical cross section is achieved for all polymers. From Im(−1/ɛ), the real and imaginary parts of ɛ (ω), the refractive index, and the extinction coefficient were determined for all polymers in the energy range ћω = 0 to 70 eV. An oscillator is clearly observed for PPY, PET, and PA6 at ∼ 6.7 eV, which corresponds to the π plasmon. This oscillator is not found for PMMA, PE, and PVC. A set of oscillators in the 20–30 eV energy range corresponding to the σ+π plasmon is found for all polymers.
Spectral and topological properties of a family of generalised Thue-Morse sequences
Authors: Baake Michael , Gähler Franz , Grimm Uwe
Published: March 2012

The classic middle-thirds Cantor set leads to a singular continuous measure via a distribution function that is known as the Devil's staircase. The support of the Cantor measure is a set of zero Lebesgue measure. Here, we discuss a class of singular continuous measures that emerge in mathematical diffraction theory and lead to somewhat similar distribution functions, yet with significant differences. Various properties of these measures are derived. In particular, these measures have supports of full Lebesgue measure and possess strictly increasing distribution functions. In this sense, they mark the opposite end of what is possible for singular continuous measures. For each member of the family, the underlying dynamical system possesses a topological factor with maximal pure point spectrum, and a close relation to a solenoid, which is the Kronecker factor of the system. The inflation action on the continuous hull is sufficiently explicit to permit the calculation of the corresponding dynamical zeta functions. This is achieved as a corollary of analysing the Anderson-Putnam complex for the determination of the cohomological invariants of the corresponding tiling spaces.
Comment on “Print your atomic force microscope” [Rev. Sci. Instrum. 78, 075105 (2007)]
Authors: Szoszkiewicz R.
Published: March 2012

The paper of Kühner et al. [Rev. Sci. Instrum. 78, 075105 (2007)10.1063/1.2751099], presents a sound realization of a very nice idea. Namely, to design and prepare (via rapid prototyping) a custom head for atomic force microscope (AFM). Custom AFM heads are essential for various applications, which include the AFM force spectroscopy modes and convenient AFM coupling with other techniques. Our comment concerns the deflection data for a thermally driven AFM cantilever obtained by Kühner et al. using their AFM setup (Figure 3 therein). The results of Kühner et al. imply that a thermally excited AFM cantilever vibrates with aberrantly large amplitudes. Namely, the deflection noise amplitudes for the MLCT-D cantilever are 60–100 times larger than what is typically observed in our lab and by others. As we argue, the author's mistake is likely attributed to an improper usage of the AFM bandwidth. We explain the necessary correction and discuss the issue of bandwidth for the AFM force spectroscopy measurements.
Particle-in-cell simulation of a double stage Hall thruster
Authors: Yu Daren , Song Maojiang , Liu H. , Ding Y. J. , Li Hong
Published: March 2012

The purpose of inventing a double stage Hall thruster is to control the propellant ionization and ion acceleration independently. In order to better understand the physics involved in such a thruster, an improved particle-in-cell method is used in this paper to simulate the discharge process. It is shown that the numerical features in the ionization stage accord well with the experimental results. It is also indicated that the ionization process and the acceleration process cannot be separated completely, as a relatively important ionization still occurs in the acceleration stage. Furthermore, an optimal threshold of ionization voltage in the ionization stage is existed to obtain the most favorable distributions of plasma parameters in the whole discharge channel.
Magnetohydrodynamic flow of a binary electrolyte in a concentric annulus
Authors: Qin M. , Bau H. H.
Published: March 2012

We study theoretically magnetohydrodynamic (MHD) motion of a binary electrolyte in a concentric annulus subjected to a uniform, axial magnetic field. The annulus’ cylindrical surfaces serve as electrodes. When a potential difference is imposed across the cylindrical electrodes, radial electric current flows in the solution and interacts with the axial magnetic field to induce a Lorentz body force that drives azimuthal fluid flow. When the annulus is infinitely long, a purely azimuthal flow (analogous to the classical Dean flow) is possible. We determine the velocity profile, ion concentration fields, and current density as functions of the electrodes’ potential difference and study the linear stability of the azimuthal flow. Of particular interest is the effect of the ions’ concentration fields on the centrifugal Dean instability. When the current is directed outwardly, electrochemical effects destabilize the flow, and the MHD flow loses stability at a Dean number much lower than its analogous, pressure driven flow. The supercritical flow consists of convective cells in the transverse plane. In contrast, when the current is directed inwardly, electrochemical effects stabilize the flow and the azimuthal flow is linearly stable for all Dean numbers. When the annulus is capped, purely azimuthal flow is no longer possible, and the flow in the annulus is always three-dimensional. In this case, the secondary flow is mostly driven by pressure gradients induced by the no-slip floor and ceiling. The intensity of the transverse convection depends then only weakly on the current's direction.
Simulations of shearing of capillary bridges
Authors: Wiklund H. S. , Uesaka T.
Published: March 2012

Capillary bridges are considered as the major source of interaction forces acting in wet particulate systems. We study the dynamic shear resistance by using a lattice Boltzmann numerical scheme for a binary fluid. The shear resistance force showed very little dependence on surface tension and contact angle. Instead, the shear resistance is a dynamic phenomenon and a major contributing factor is the distortion of the flow field caused by the presence of interfaces. This distortion of the flow field is geometry-dependent: in smaller diameter bridges the proportion of this distorted flow field becomes larger and it makes a major contribution to the shear resistance force. In other words multiple bridges have an enhancement effect on shear resistance.
Thermal effects on energetics and dynamics in water cluster anions (H2O)n−
Authors: Young Ryan M. , Yandell Margaret A. , King Sarah B. , Neumark Daniel M.
Published: March 2012

The electron binding energies and relaxation dynamics of water cluster anions (H2O)n− (11 ≤ n ≤ 80) formed in co-expansions with neon were investigated using one-photon and time-resolved photoelectron imaging. Unlike previous experiments with argon, water cluster anions exhibit only one isomer class, the tightly bound isomer I with approximately the same binding energy as clusters formed in argon. This result, along with a decrease in the internal conversion lifetime of excited (H2O)n− (25 ≤ n ≤ 40), indicates that clusters are vibrationally warmer when formed in neon. Over the ranges studied, the vertical detachment energies and lifetimes appear to converge to previously reported values.