bluuebunny/crossref_metadata_2025 huggingface dataset:
Wer benötigt präventive Hilfen – wen erreichen wir?
Authors: Pauschardt Jan , Eimecke Sylvia Dorothee , Mattejat Fritz
Published: April 2011

Zusammenfassung. Die hohe Prävalenz introversiver Störungen (Angst und Depression) bei Kindern erfordert die Implementierung effektiver Präventionsprogramme. Über die Forschung zur Wirksamkeit einzelner Programme hinaus bedarf es insbesondere auch Studien zur Optimierung von Verbreitung, Durchführung und Implementierung solcher Maßnahmen. Das Ziel dieser Untersuchung war der Vergleich zweier Strategien zur Rekrutierung von Teilnehmern für ein kognitiv-verhaltenstherapeutisch ausgerichtetes Programm, das sich an 8–12-jährige Kinder mit subklinischen Angst- und depressiven Symptomen richtete. Die erste Strategie beinhaltete verschiedene lokale Werbemaßnahmen für das Kursangebot, auf die sich die Eltern selbstständig anmelden konnten; die zweite Rekrutierungsmaßnahme erfolgte im Rahmen einer epidemiologischen Erhebung an 11 Regelschulen. Hier wurde den Eltern, deren Kinder erhöhte introversive Symptome aufwiesen, das Präventionsangebot unterbreitet. Während sich der erste Zugang projektbezogen als effektiv erwies, waren die Ergebnisse der Rekrutierung über die Schulen ausgesprochen schwach. Die beiden Stichproben werden hinsichtlich Teilnahmequoten, Verlauf der Rekrutierung, Lebensqualität, psychischer Belastung sowie soziodemographischer Variablen explorativ verglichen. Der Bedarf an systematischen Rekrutierungsstudien wird betont.
Kinder krebskranker Eltern: Entwicklungspsychologische Aspekte, kindliche Belastungen und psycho-soziale Unterstützungsmöglichkeiten
Authors: Möller Birgit , Krattenmacher Thomas , Romer Georg
Published: April 2011

Zusammenfassung. Psychosoziale Interventionen für Krebspatienten und Einbezug der Partner gehören mittlerweile zum Behandlungsstandard integrativer Versorgung. Allerdings werden die Patienten immer noch selten in ihrer Elternrolle wahrgenommen und familienzentrierte Angebote bei der Behandlung von körperlich kranken Patienten ungenügend berücksichtigt. Aktuelle Studien zeigen, dass Kinder krebskranker Eltern ein erhöhtes Risiko für psychopathologische Symptome aufweisen. Das Ziel des Artikels ist es, anhand qualitativer und quantitativer empirischer Studien einen Überblick über kindliche Belastungen und familiäre Verarbeitungsformen der elterlichen Krebserkrankung zu geben sowie eine entwicklungspsychologische Sichtweise zu vermitteln. Das Hamburger COSIP-Beratungskonzept für Familien mit einem ernsthaft körperlich erkrankten Elternteil wird vorgestellt.
Fragebogenerfassung von körperlicher Aktivität
Authors: Kahlert Daniela , Brand Ralf
Published: April 2011

Zusammenfassung. In der vorliegenden Studie wurde untersucht, ob in Fragebogenuntersuchungen die Vorgabe unterschiedlicher Antwortskalen zur Beschreibung der Häufigkeit eigener sportlicher Aktivität einen Einfluss auf diese Aktivitätsangabe, vor allem aber auf die nachfolgende Messung von gesundheits- und sportbezogenen Kognitionen hat. Hierzu wurden die Daten von 118 Personen aus einem randomisierten Gruppenvergleich gegenübergestellt. Der Hälfte der Probanden wurde zur Beschreibung ihrer sportlichen Aktivität eine Hochfrequenz-Skala mit den Antwortkategorien „nie”, „selten”, „1-mal pro Monat”, „1-mal pro Woche” und „mehrmals wöchentlich” vorgelegt. Die andere Hälfte bearbeitete eine Mittelfrequenz-Skala mit den Antwortkategorien „nie”, „selten”, „alle paar Monate”, „1-mal pro Monat” und „1-mal pro Woche und öfter”. Als abhängige Variablen wurde anschließend, bei allen Probanden gleich, erstens die subjektive Bedeutsamkeit sportlicher Aktivität und zweitens die gesundheitsbezogene Lebensqualität (WHOQOL-bref) erfasst. Die Ergebnisse zeigen den erwarteten antwortverzerrenden Einfluss der zur Erfassung von sportlicher Aktivität gewählten Antwortskala: Personen die die Hochfrequenz-Skala vorgelegt bekamen, gaben häufiger an öfter sportlich aktiv zu sein (Cramer’s V = .30). Korrespondierend dazu wurde auch die subjektive Bedeutsamkeit sportlicher Aktivität höher (d = .37) und die gesundheitsbezogene Lebensqualität positiver (d = .36) eingeschätzt. Diese Messartefakte könnten wahrscheinlich durch die Erfassung sportlicher Aktivität mit Fragen des Typs „Ich bin ...mal pro Woche/Monat für ...Minuten sportlich (körperlich) aktiv” kontrolliert werden.
Dynamic performance analysis of permanent magnet contactor with a flux-weakening control strategy
Authors: Wang Xianbing , Lin Heyun , Fang Shuhua , Jin Ping , Wang Junhua , Ho S. L.
Published: April 2011

A new flux-weakening control strategy for permanent magnet contactors is proposed. By matching the dynamic attraction force and the antiforce, the terminal velocity and collision energy of the movable iron in the closing process are significantly reduced. The movable iron displacement is estimated by detecting the closing voltage and current with the proposed control. A dynamic mathematical model is also established under four kinds of excitation scenarios. The attraction force and flux linkage are predicted by finite element method and the dynamics of the closing process is simulated using the 4th-order Runge-Kutta algorithm. Experiments are carried out on a 250A prototype with an intelligent control unit to verify the proposed control strategy.
Active tuning of a microstrip hairpin-line microwave bandpass filter on a polycrystalline yttrium iron garnet substrate using small magnetic fields
Authors: Gillette S. M. , Geiler A. L. , Chen Z. , Chen Y. , Arruda T. , Xie C. , Wang L. , Zhu X. , Liu M. , Mukerjee S. , Vittoria C. , Harris V. G.
Published: April 2011

Active magnetic tuning of a microstrip hairpin-line coupled resonator bandpass filter fabricated on a polycrystalline yttrium iron garnet substrate has been demonstrated. The filter exhibits a five-pole Chebyshev response with passband center frequency tunability from 8.3 to 9 GHz under low applied H fields of 50–200 Oe. The instantaneous bandwidth was measured to be approximately 1 GHz. During tuning, passband center frequency insertion loss varies between 1 and 1.4 dB. Good agreement between simulated and measured device performance was demonstrated. Advantages of the proposed filter design include planar geometry, compact size, low insertion loss, and low field tunability. The proposed design approach lends itself to the implementation of a wide range of filter responses, including low pass, high pass, bandpass, and band stop, as well as passband characteristics, including center frequency, fractional bandwidth, passband ripple, out-of-band rejection, etc.
Spin dynamics and magnetic anisotropies at the Fe/GaAs(001) interface
Authors: Kardasz B. , Montoya E. A. , Eyrich C. , Girt E. , Heinrich B.
Published: April 2011

20Au/(d)Fe/GaAs(001) structures were deposited using molecular beam epitaxy, where Fe thickness d = (5...90) atomic layers. Interface anisotropies were investigated using the in-plane angular dependence of ferromagnetic resonance (FMR). Intrinsic and extrinsic contributions to magnetic damping were investigated using FMR linewidth (ΔH) measurements at 9, 24, 36, and 72 GHz (in-plane configuration) and 9, 24, and 36 GHz (perpendicular configuration). The in-plane cubic and uniaxial perpendicular anisotropies were well described by the bulk and interface contributions indicating that the Fe films have a high lattice coherence and high critical Curie temperature Tc. The in-plane uniaxial anisotropy is more complex and will be discussed in detail. The frequency dependence of ΔH(f) was analyzed using the Gilbert damping, two magnon scattering, and long range magnetic inhomogeneity contributions. The thickness dependence of the Gilbert damping parameter α was found to be well described by the bulk and interface terms.
Electronic and structural characterization of LiF tunnel barriers in organic spin-valve structures
Authors: Szulczewski Greg , Brauer Jonathan , Ellingsworth Edward , Kreil Justin , Ambaye Hailemariam , Lauter Valeria
Published: April 2011

The electronic, magnetic, and structural properties of Ni80Fe20 and Co electrodes at LiF and aluminum tris(8-hydroxyquinoline), or Alq3, interfaces were investigated with photoemission spectroscopy and polarized neutron reflectivity measurements. When LiF was deposited onto Ni80Fe20 films and Co was deposited onto thin LiF layers, the work function of both metals decreased. Polarized neutron reflectivity measurements were used to probe the buried interfaces of multilayers resembling a spin-valve structure. The results indicate that LiF is an effective barrier layer to block diffusion of Co into the Alq3 film. X-ray absorption spectra at the fluorine K edge indicate that no chemical reactions occur between Co and LiF. Despite these positive effects derived from the LiF tunnel barriers, there was no magnetoresistance in spin valves when the Alq3 layer was greater than 50 nm.
Perpendicular magnetic anisotropy and spin reorientation transition in L1 FePt films
Authors: Ahn Jae Young , Lee Nyun Jong , Kim Tae Hee , Lee J.-H. , Michel Anny , Eyidi Dominique
Published: April 2011

We investigated the thickness and composition dependence of perpendicular magnetic anisotropy (PMA) in L10 Fe1−xPtx (x = 0.4, 0.5, and 0.55) films. The FePt films with different thicknesses of 35 and 70 Å were grown at the substrate temperature Ts = 300 °C by molecular beam epitaxy coevaporation technique. A (001)-oriented epitaxial L10 FePt film was grown on the thin (001)-oriented fcc Pt layer, while a poorly crystallized FePt film was formed on the (111)-textured Pt layer. Our results showed that, at a fixed thickness of 70 Å, the PMA of FePt alloy films is enhanced as Pt content increases from 40% to 55%.
A modified Preisach hysteresis operator for the modeling of temperature dependent magnetic material behavior
Authors: Sutor Alexander , Rupitsch Stefan J. , Bi Shasha , Lerch Reinhard
Published: April 2011

In this paper, we present a model for temperature dependent hysteretic nonlinearities with nonlocal memories. This model can be applied to describe hysteretic material behavior. Common applications are ferromagnetic or magnetostrictive materials. Our model consists mainly of a Preisach operator with a continuous Preisach weight function. We choose a weight function which shows a strong correlation between the function’s parameters and certain properties of the hysteresis curve. As a new approach, the weight function is written as a function of temperature. The model parameters are customized to a set of symmetric hysteresis curves. We verify our model for magnetic materials with differently shaped hysteresis curves, different temperatures and magnetic field amplitudes.
Thermally activated transitions in a system of two single domain ferromagnetic particles
Authors: Cimpoesu Dorin , Stancu Alexandru , Klik Ivo , Chang Ching-Ray , Spinu Leonard
Published: April 2011

Numerical simulations based on the stochastic Langevin equation are applied here to a system of two uniaxial single domain ferromagnetic particles with antiferromagnetic dipolar coupling. The hysteresis loops of a strongly coupled systems exhibit fully demagnetized, intermediate metastable configurations which separate the two fully saturated states. At small magnetostatic couplings, on the other hand, and at sufficiently weak damping, the intermediate metastable configuration becomes only partially demagnetized. This state cannot be associated with any single local minimum of the free energy function.
Coercive mechanism and training effect in Fe-Au/Ni-Fe bilayer films
Authors: Yuan Fu-Te , Yao Y. D. , Lee S. F. , Hsu J. H.
Published: April 2011

Exchange bias effect in spin glass/ferromagnetic systems has been studied recently. Here, we report the coercive mechanism and training effect in Fe-Au/Ni-Fe films. Experimental results indicate that the coercivity (Hc) mainly originates from direct coupling between Fe-Au and Ni-Fe layers at temperatures (T) well below the blocking point (Tb). At T near Tb, Hc comes from spin-flop coupling and defects in the Ni-Fe layer. The findings confirm the validity of our spin structure model. Additionally, irreversible rearrangement of Fe-Au spins from the field cooling state was indicated by the training effect of both Fe-Au/Ni-Fe and Fe-Au powder samples. The results are discussed in detail.
Buffer-layer-enhanced magnetic field effect in La0.5Ca0.5MnO3/LaMnO3/SrTiO3:Nb heterojunctions
Authors: Gao W. W. , Sun J. R. , Lu X. Y. , Shang D. S. , Wang J. , Hu F. X. , Shen B. G.
Published: April 2011

The transport behaviors of La0.5Ca0.5MnO3/LaMnO3/SrTiO3:Nb heterojunctions with a LaMnO3 layer thickness of between 0 and 12 nm have been systematically studied. The effect of the magnetic field on the junction without the buffer layer is weak. The influence of the magnetic field on the junction is maximized when the layer thickness is ∼3 nm, demonstrated by a significant field-induced increase in current when the bias voltage is fixed. The corresponding magnetoresistance of the junction is negative, and its maximal value is ∼−32% for a field change of 5 T at 80 K. Based on a quantitative analysis of the current-voltage characteristics, the interfacial barrier can be derived, and it shows a complex variation with an increase in layer thickness, first decreasing and then increasing. This is the apparent reason for the change in buffer-layer-enhanced negative magnetoresistance of the junctions for different layer thicknesses.
Accurate calculation of the nucleation field and hysteresis loops in hard-soft multilayers
Authors: Zhao G. P. , Deng Y. , Zhang H. W. , Cheng Z. H. , Ding J.
Published: April 2011

In this paper, the nucleation field HN, hysteresis loops, and coercivity mechanism for hard/soft multilayers have been investigated within a self-contained micromagnetic model, which change with the strength of the interface exchange coupling Ji as well as the thickness of the hard and soft layers Lh and Ls. Analyses show that the nucleation field goes up as the interface exchange coupling increases. However, Ji has a significant effect on HN only when Ls is about 10% of the domain wall width of the soft phase while the thickness of the hard layer is larger than its domain wall width. The hysteresis loops of the Nd2Fe14B/α-Fe/Nd2Fe14B trilayers for various Ji have been calculated. The calculated pinning field decreases when Ji increases. It is found that, as Ls increases, the coercivity mechanism changes from pinning to nucleation. The change of exchange coupling at the interface influences the soft layer thickness, at which the coercivity starts to deviate from pinning. The critical thickness of the soft phase, at which the behavior of the hysteresis loop changes from the single-phased one to the two-phased one, decreases as Ji decreases, so that the “rigid composite magnet” appears only when Ls is very small for smaller Ji.
Neutron powder diffraction studies and magnetic properties in Nd1−xKxMnO3 (x = 0.15 and 0.20) compounds
Authors: Samantaray B. , Ravi S. , Perumal A. , Dhiman I. , Das A.
Published: April 2011

Nd1−xKxMnO3 (x = 0.15–0.20) compounds were prepared in single phase form and their crystal structure, magnetic structure, and magnetic properties were studied by recording neutron powder diffraction patterns and magnetization measurements down to 22 K. The patterns at low temperatures could be refined by considering magnetic reflections corresponding to ferromagnetic structure. The value of lattice parameters exhibits a sharp fall below FM TC. The temperature variation of magnetization measurements show that both the compounds exhibit paramagnetic to ferromagnetic transition at around 120 K followed by a low temperature spin-glass-like transition at around 45 K. The effective magnetic spin (Seff) toward the double exchange ferromagnetic interaction was determined by analyzing the initial magnetization data in terms of the Brillouin function model. The refined magnetic moments of Mn ion are found to be ferromagnetically aligned along ac plane with a typical value of 2.82(3) μB and 2.68(5) μB per Mn ion for x = 0.15 and x = 0.20 compounds, respectively, at 22 K and their temperature dependence is comparable to the magnetization results.
Damping in magnetization dynamics of single-crystal Fe3O4/GaN thin films
Authors: Zou X. , Wu J. , Wong P. K. J. , Xu Y. B. , Zhang R. , Zhai Y. , Bunce C. , Chantrell R. W.
Published: April 2011

The time-resolved magnetization dynamics of epitaxial Fe3O4 thin films grown on GaN(100) was studied using a field pumped time-resolved magneto-optical Kerr (TRMOKE) setup. The dynamic responses of the magnetization in the 3 and 6 nm Fe3O4/GaN films under a 1 kOe magnetic field pulse were measured and compared to a macrospin Landau−Lifshitz−Gilbert (LLG) simulation. The anisotropy constants of the two systems have been estimated and the damping constant has been extracted by applying different bias field along two orthogonal directions. This work provides a first TRMOKE study of thickness and frequency dependence of damping in single crystal Fe3O4/GaN systems.
Vector hysteresis modeling using octal clusters of coupled step functions
Authors: Adly A. A. , Abd-El-Hafiz S. K.
Published: April 2011

Recently, substantial efforts have been focused on the efficiency enhancement of vector Preisach-type model implementation methodologies. This paper presents a computationally efficient approach for implementing a vector Preisach-type hysteresis model through an ensemble of octal clusters of coupled step functions. Within this approach, each cluster can be tuned by proper selection of coupling factors to exhibit vector hysteresis properties, thus minimizing number of clusters needed to construct a vector Preisach-type model.
Size dependence in self-bending mechanism of Ge/Si bilayer nanofilms
Authors: Lee Heung-Soon , Cho Maenghyo , Lee Byeong-Joo
Published: April 2011

The governing mechanism for a self-bending of Ge/Si bilayer epitaxial nanofilms that results in the formation of various nanostructures (nanotube, nanohelix, etc.) has been investigated using a molecular dynamics simulation. The effect of misfit stress between Ge and Si layers, surface stress due to the surface reconstruction and the anisotropy of elastic modulus on the bending behavior and the effect of film thickness on the relative strength of the individual factors are clarified. All experimentally and theoretically reported results that show sometimes a mutual disagreement could be reconciled, which enabled a more elaborate control of nanostructure formation.
Magnetic properties and exchange interactions in TbNi5−xMx (M=Co and Fe) compounds: Ab initio calculations
Authors: Lukoyanov A. V. , Haldar Arabinda , Das A. , Nayak Ajaya K. , Suresh K. G. , Nigam A. K.
Published: April 2011

In order to investigate magnetic structure and the mechanism of the Curie temperature (TC) enhancement in TbNi4Co and TbNi4Fe compounds in comparison with TbNi5, electronic structure calculations were performed within the LSDA + U method (local spin density approximation with Hubbard U-correction). Magnetic moments for Ni, Fe, and Tb ions resulted from the LSDA + U calculations for TbNi5 and TbNi4Fe compounds were found to be in very good agreement with the ones refined from the neutron data. Experimental magnetization measurements demonstrate a substantial increase of TC in TbNi4Co (TC ∼ 60 K) and especially in TbNi4Fe (TC ∼ 280 K) in comparison with TbNi5 (TC ∼ 23 K) that correlates with the growth of the exchange–interaction parameter in the 3d sublattice calculated in the present work.
Magnetic tunneling junction based magnetic field sensors: Role of shape anisotropy versus free layer thickness
Authors: Shah Lubna R. , Bhargava Nupur , Kim Sangcheol , Stearrett Ryan , Kou Xiaoming , Sun Xiaolian , Sun Shouheng , Kolodzey James , Nowak Edmund R. , Xiao John Q.
Published: April 2011

Al2O3- and MgO-based magnetic tunnel junction (MTJ) sensors were designed and fabricated using microfabrication techniques. This study revealed that in the case of Al2O3-based sensors, the shape anisotropy in the free NiFe electrode resulted in a linear and hysteresis-free tunneling magnetoresistance (TMR) curve. These sensors exhibited TMR values between 27% and 30% and sensitivity up to 0.4%/Oe over a magnetic field range of − 40 to 40 Oe. In the case of CoFeB/MgO/CoFeB MTJ sensors, shape anisotropy alone was not sufficient to achieve a linear and hysteresis-free MR response. A superparamagnetic free layer was used to achieve the desired sensor response. MgO-based sensors had about 90% TMR and 1.1%/Oe sensitivity over the same field range as Al2O3-based MTJs.
Suppression of superconductivity by interparticle interactions in Al nanoparticle assembly
Authors: Liu Shih-Bin , Chen Chia-Tang , Wu Chun-Ming , Wang Chin-Wei , Wang Chih-Jen , Karna Sunil K. , Li Wen-Hsien
Published: April 2011

We report on the observations of enhanced superconductivity in a very loosely packed 6.8 nm Al nanoparticle assembly and the suppression of superconductivity by interparticle interactions, through ac magnetic susceptibility and magnetization measurements. TC and HC of the 6.8 nm Al particles are, respectively, 1.9 and 77 times higher than that of bulk Al. M(Ha) curves taken below and above TC can all be described by a Langevin profile, showing the existence of a spontaneous magnetic component in superconducting phase. Superconductivity is found to be gradually suppressed by interparticle interactions.
Structural evolution of Ce1−xGdxFeAsO0.84F0.16 superconductors
Authors: Yang J. L. , Ren W. J. , Li D. , Zhang Z. D.
Published: April 2011

Structural parameters have a critical impact on superconductivity in iron-based oxypnictide superconductors. Structural evolution study was performed on Ce1−xGdxFeAsO0.84F0.16 superconductors by the analysis of the x-ray diffraction patterns with Rietveld refinement. Substitution of Gd for Ce generates internal pressure that compresses the crystal lattice. The contraction of the c axis is also indicated by the reduction of Ce/Gd-As and Ce/Gd-O/F distances, while there is a slight increase in the As-Fe-As block size, which is compensated by a large reduction in the Ce/Gd-O/F-Ce/Gd block with Gd substitution. The diagonal Fe-As-Fe angle for Ce0.6Gd0.4FeAsO0.84F0.16, with the highest Tc among Ce1−xGdxFeAsO0.84F0.16 compounds, is 111.13°. It is close to the ideal value of 109.47° for the perfect FeAs tetrahedron, which is situated in the region of Fe-As-Fe bond angles where RFeAsO compounds tend to have the highest Tc.
Influence of spin relaxation length on lateral double superconductor/ferromagnet/superconductor junctions
Authors: Lin L. K. , Huang S. Y. , Lin J. K. , Huang J. H. , Lee S. F.
Published: April 2011

We study the spin dependent transport at the junctions between two superconducting Nb leads connected by two ferromagnetic NiFe bars in parallel, which have various separations. The separation distance l between NiFe bars was varied from 150 to 700 nm to study the spin relaxation effect in Nb. In small l (150 and 250 nm) samples, a spin-valve-like behavior related to the inverse proximity effect was observed, which manifest itself as charge accumulation due to spin imbalance near the interface. However, for samples with large l, the spin-valve behavior vanishes and the anisotropic magnetoresistance effect dominates.
Relativistic generation of vortex and magnetic field
Authors: Mahajan S. M. , Yoshida Z.
Published: April 2011

The implications of the recently demonstrated relativistic mechanism for generating generalized vorticity in purely ideal dynamics [Mahajan and Yoshida, Phys. Rev. Lett. 105, 095005 (2010)] are worked out. The said mechanism has its origin in the space-time distortion caused by the demands of special relativity; these distortions break the topological constraint (conservation of generalized helicity) forbidding the emergence of magnetic field (a generalized vorticity) in an ideal nonrelativistic dynamics. After delineating the steps in the “evolution” of vortex dynamics, as the physical system goes from a nonrelativistic to a relativistically fast and hot plasma, a simple theory is developed to disentangle the two distinct components comprising the generalized vorticity—the magnetic field and the thermal-kinetic vorticity. The “strength” of the new universal mechanism is, then, estimated for a few representative cases; in particular, the level of seed fields, created in the cosmic setting of the early hot universe filled with relativistic particle–antiparticle pairs (up to the end of the electron–positron era), are computed. Possible applications of the mechanism in intense laser produced plasmas are also explored. It is suggested that highly relativistic laser plasma could provide a laboratory for testing the essence of the relativistic drive.
Computation of methodology-independent single-ion solvation properties from molecular simulations. III. Correction terms for the solvation free energies, enthalpies, entropies, heat capacities, volumes, compressibilities, and expansivities of solvated ions
Authors: Reif Maria M. , Hünenberger Philippe H.
Published: April 2011

The raw single-ion solvation free energies computed from atomistic (explicit-solvent) simulations are extremely sensitive to the boundary conditions (finite or periodic system, system or box size) and treatment of electrostatic interactions (Coulombic, lattice-sum, or cutoff-based) used during these simulations. However, as shown by Kastenholz and Hünenberger [J. Chem. Phys. 124, 224501 (2006)]10.1529/biophysj.106.083667, correction terms can be derived for the effects of: (A) an incorrect solvent polarization around the ion and an incomplete or/and inexact interaction of the ion with the polarized solvent due to the use of an approximate (not strictly Coulombic) electrostatic scheme; (B) the finite-size or artificial periodicity of the simulated system; (C) an improper summation scheme to evaluate the potential at the ion site, and the possible presence of a polarized air–liquid interface or of a constraint of vanishing average electrostatic potential in the simulated system; and (D) an inaccurate dielectric permittivity of the employed solvent model. Comparison with standard experimental data also requires the inclusion of appropriate cavity-formation and standard-state correction terms. In the present study, this correction scheme is extended by: (i) providing simple approximate analytical expressions (empirically-fitted) for the correction terms that were evaluated numerically in the above scheme (continuum-electrostatics calculations); (ii) providing correction terms for derivative thermodynamic single-ion solvation properties (and corresponding partial molar variables in solution), namely, the enthalpy, entropy, isobaric heat capacity, volume, isothermal compressibility, and isobaric expansivity (including appropriate standard-state correction terms). The ability of the correction scheme to produce methodology-independent single-ion solvation free energies based on atomistic simulations is tested in the case of Na+ hydration, and the nature and magnitude of the correction terms for derivative thermodynamic properties is assessed numerically.
The role of Ru5+ in increasing TC of Cr-doped SrRuO3 system
Authors: Zhang Shile , Tan Shun , Pi Li , Zhang Changjin , Zhang Yuheng
Published: April 2011

Two series of samples with nominal composition Sr1−xLaxRu1−xCrxO3 (SLRC) and Sr1−xCaxRu1−xCrxO3 (SCRC) (x = 0.04, 0.08, and 0.12) have been prepared and investigated in order to explore the mechanism of the Curie temperature increase in Cr-doped SrRuO3. The magnetic experiment results demonstrate that the Curie temperature (TC) of SLRC decreases with an increase in x, whereas in SCRC, TC slightly increases with Cr doping. This indicates that the enhancement of the ferromagnetism by Cr doping is more significant in the system containing Ru5+. We suggest that the exchange interaction between Ru5+ and Cr3+ plays an important role in enhancing the ferromagnetism in the system.
Ferrohydrodynamic pumping of a ferrofluid or electrohydrodynamic pumping of a polar liquid through a planar duct
Authors: Felderhof B. U.
Published: April 2011

Ferrohydrodynamic pumping of a ferrofluid through a planar duct by means of a running magnetic wave is studied to second order in the amplitude of the exciting current density. The theory for electrohydrodynamic pumping of a polar liquid by means of a running electric wave is shown to be nearly identical. For the given fluid parameters, the net flow rate can be optimized by suitable choice of wavenumber and frequency of the running wave.
Lipid membrane instability driven by capacitive charging
Authors: Schwalbe Jonathan T. , Vlahovska Petia M. , Miksis Michael J.
Published: April 2011

A new mechanism for lipid membrane destabilization and poration by electric fields is proposed. When a dc electric field is applied to an insulating planar membrane separating fluids with different conductivities, a capacitive charging current through the membrane in combination with shearing stresses, created by the electric field acting on its own induced free charge, drives electrohydrodynamic flow that modulates the shape and lipid density fluctuations. The instability is transient and decays as the membrane charges. Accordingly, the dynamics depends on the relative magnitude of the time for charging the membrane capacitor and the electrohydrodynamic flow time.
Circularly polarized photoluminescence from platinum porphyrins in organic hosts: Magnetic field and temperature dependence
Authors: Diaconu C. V. , Batista E. R. , Martin R. L. , Smith D. L. , Crone B. K. , Crooker S. A. , Smith’s D. L.
Published: April 2011

We study the temperature and magnetic field-dependent photoluminescence from the metalorganic molecules octaethyl-porphine platinum (PtOEP) and porphine platinum (PtP) that are doped into organic hosts. We first consider PtOEP in the polymer host poly-dioctylfluorene (PFO), which is characteristic of the phosphorescent dopants and polymers used in organic light-emitting diodes. We observe that the intensity of the PtOEP zero-phonon emission band, which is strongly suppressed at low temperatures to 1.6 K, increases dramatically with applied magnetic field and is accompanied by a marked circular polarization. This “magnetic brightening” effect, similar to that observed in other organic systems such as carbon nanotubes, highlights the interplay between low-energy optically active and optically forbidden excited states of PtOEP, which become mixed in applied magnetic fields. To elucidate these findings, we also investigate (i) dilute PtOEP in n-octane hosts (where emission lines are much sharper), and (ii) dilute PtP in n-octane hosts, for which the emission spectra are simpler and can be directly compared with theory. Detailed electronic structure calculations of PtP were performed, and a model for the magnetic field and temperature dependence of the zero phonon emission lines is developed, which agrees quantitatively with the data for PtP and with the circular polarization of the PtOEP emission.
Extraction of AlGaN/GaN heterostructure Schottky diode barrier heights from forward current-voltage characteristics
Authors: Lv Yuanjie , Lin Zhaojun , Corrigan Timothy D. , Zhao Jianzhi , Cao Zhifang , Meng Lingguo , Luan Chongbiao , Wang Zhanguo , Chen Hong
Published: April 2011

Ni Schottky contacts on AlGaN/GaN heterostructures have been fabricated, and one of the prepared samples has been annealed at 700 °C for half an hour. The barrier heights for the prepared samples were measured by internal photoemission. Based on the measured forward current-voltage (I-V) characteristics and using the two-diode model, the Ni Schottky barrier height at zero bias has been analyzed and calculated by self-consistently solving Schrodinger’s and Poisson’s equations, and the correlation expression between the barrier height at zero electric field and that at zero bias has been derived for Schottky contacts on AlGaN/GaN heterostructures. The calculated Schottky barrier heights corresponding to zero electric field for the prepared Ni Schottky contacts on AlGaN/GaN heterostructures agree well with the photocurrent measured results. Thus, the method for extraction of AlGaN/GaN heterostructure Schottky barrier heights from forward I-V characteristics is developed and determined.
Thrust characteristics of a double-sided high temperature superconducting linear synchronous motor with a high temperature superconducting magnetic suspension system
Authors: Jin Jianxun , Zheng Luhai , Xu Wei , Guo Youguang , Zhu Jianguo
Published: April 2011

An electromagnetic design of a double-sided high temperature superconducting (HTS) linear synchronous motor (HTSLSM) with an HTS bulk magnet secondary is introduced in this paper. A HTS magnetic suspension system is applied to replace the sliding rail to levitate the secondary mover resulting in the HTSLSM moving without sliding friction. The thrust model of the HTSLSM is built using a magnetic circuit method and the thrust characteristics obtained from the model are compared with finite element analysis and practical testing results. The theoretical analysis on the prototype has also been verified by measurements.
Ordering kinetics of block copolymers directed by periodic two-dimensional rectangular fields
Authors: Li Weihua , Xie Nan , Qiu Feng , Yang Yuliang , Shi An-Chang
Published: April 2011

The ordering kinetics of directed assembly of cylinder-forming diblock copolymers is investigated by cell dynamics simulation of the time-dependent Ginzburg–Landau theory. The directing field, mimicking chemically or topologically patterned surfaces, is composed of a rectangular array of potential wells which are attractive to the minority blocks. The period of the templating fields is commensurate with the hexagonal lattice of the block copolymer domains. The ordering kinetics is described by the time evolution of the defect concentration, which reveals that the rectangular field of [1 m] for a given density multiplication has the best directing effect, and the reversed case of [m 1] has the worst. Compared with a hexagonal directing field, the rectangular field provides a better directing efficiency for a fixed high density multiplication. The difference of the directing effect can be understood by analyzing the ordering mechanisms in the two types of directing fields. The study reveals that the rectangular pattern is an alternative candidate to direct block copolymer assembly toward large-scale ordered domains.
Thermal gratings and phase in high-order, transient-grating spectroscopy
Authors: Sahu Kalyanasis , Berg Mark A.
Published: April 2011

Thermal gratings are a well known feature in one-dimensional (i.e., single excitation) transient-grating spectroscopy. This paper presents theory and experiments for thermal gratings in multiple dimensions (i.e., with many excitations). The theory of thermal gratings is extended to an arbitrary number of dimensions using an incoherent Hilbert-space formalism. Interference between Hilbert-space pathways makes it impossible for a thermal grating to propagate across multiple time intervals. The only surviving signal is a hybrid—a population grating between excitations and a thermal grating between the final excitation and the probe. This theory is tested on auramine O in methanol (1D) and in an ionic liquid (3-butyl-1-methylimidazolium hexafluorophosphate) (1D and 2D). In methanol, the ground-state recovery and thermal-grating signals are well separated in time; in the ionic liquid, they are not. Using the results of the theory, accurate subtraction of the thermal-grating signal is possible, extending the useful time range of the experiments. Both the comparison to the theory and the subtraction of the thermal-grating signal are dependent on accurate measurements of the time-dependent phase in these systems. Models are proposed to account for the time-dependent phase. Beer's law is generalized to multidimensional grating spectroscopy. This law provides conventions for consistently comparing the absolute phases and magnitudes between grating and nongrating experiments and between experiments of differing dimensionality.
The effect of pressure on the phase transition behavior of tridecane, pentadecane, and heptadecane: A Fourier transform infrared spectroscopy study
Authors: Yamashita Motoi , Hirao Atsushi , Kato Minoru
Published: April 2011

The effect of pressure on the phase transition behavior of tridecane (C13), pentadecane (C15), and heptadecane (C17) has been investigated up to 489, 220, and 387 MPa, respectively, using Fourier transform infrared spectroscopy at 25 °C. The transition between the high pressure ordered (HPO) and high pressure rotator (HPR) phases has been observed in the pressure ranges of 270–220, 106–95, and 152–181 MPa for C13, C15, and C17, respectively, and the transition between the HPR and liquid phases was observed in the pressure ranges of 171–112, 73–47, and 43–70 MPa for C13, C15, and C17, respectively. The P1+P3 band of the methylene rocking mode exhibits factor group splitting caused by intermolecular vibrational coupling. This was observed in both the HPO and HPR phases, while the P1+P3 band did not split in the liquid phase. The separation of the peaks in the P1+P3 band changed discontinuously at the HPO–HPR and HPR–liquid phase transitions, even though the separation is known to change continuously in the transition from the liquid to the high temperature rotator (HTR) phase. In the HPR phase, the ratio of the intensities of the higher and lower frequency components in the P1+P3 doublet is roughly unity independent of pressure, while it is known to be much less than unity in the HTR phase. The separation of the P1+P3 doublet in the HPR phase is found to be larger for longer alkanes. From the intensity ratio, a large proportion of alkane molecules is believed to participate in intermolecular vibrational coupling and possess herringbone-type short-range positional order in the HPR phase. Conversely, in the HTR phase only small proportion of alkane molecules participate in intermolecular vibrational coupling. From the pressure dependence of the separation of the doublet, intermolecular vibrational coupling and herringbone-type short-range positional order is considered to change discontinuously at the HPR–liquid phase transition, while they are reported to change continuously at the HTR–liquid phase transition. The HPR–liquid phase transition is governed by the effect of molecular packing while the HTR–liquid phase transition is predominantly governed by the difference in entropy between the herringbone-type and parallel-type packing.
Shape-dependent absorption characteristics of three-layered metamaterial absorbers at near-infrared
Authors: Wang Jing , Chen Yiting , Hao Jiaming , Yan Min , Qiu Min
Published: April 2011

We experimentally demonstrate the absorption properties of designed metamaterial absorbers in the near-infrared wavelength regime. For the rectangular-shaped case, we demonstrate its polarization dependent absorbance at various incident angles. For each polarization, the absorbance is insensitive to the incident angle (up to 60°) and a maximum absorbance of 0.95 is obtained. Of particular interest we experimentally observe an absorption peak corresponding to a high-order resonance at 60° with an absorbance of 0.68 excited by the TM polarization. For the square-shaped case, we show its polarization-independent absorption property. A maximum absorbance around 0.65 is achieved at normal incidence and it remains high for incidence angles up to 50°.
Stability analysis for stochastic Volterra–Levin equations with Poisson jumps: Fixed point approach
Authors: Guo Lifang , Zhu Quanxin
Published: April 2011

This paper is devoted to investigate a class of stochastic Volterra–Levin equations with Poisson jumps. To the best of the authors’ knowledge, till now, the stability problem for this class of new systems has not yet been solved since Poisson jumps are considered. The main objective of this paper is to fill the gap. By using the fixed point theory, we first study the existence and uniqueness of the solution as well as the pth moment exponential stability for the considered system. Then based on the well known Borel–Cantelli lemma, we prove that the solution is almost surely pth moment exponentially stable. Our results improve and generalize those given in the previous literature. Finally, two simple examples are provided to illustrate the effectiveness of the obtained results.
Application of a scattered-light radiometric power meter
Authors: Caron James N. , DiComo Gregory P. , Ting Antonio C. , Fischer Richard P.
Published: April 2011

The power measurement of high-power continuous-wave laser beams typically calls for the use of water-cooled thermopile power meters. Large thermopile meters have slow response times that can prove insufficient to conduct certain tests, such as determining the influence of atmospheric turbulence on transmitted beam power. To achieve faster response times, we calibrated a digital camera to measure the power level as the optical beam is projected onto a white surface. This scattered-light radiometric power meter saves the expense of purchasing a large area power meter and the required water cooling. In addition, the system can report the power distribution, changes in the position, and the spot size of the beam. This paper presents the theory of the scattered-light radiometric power meter and demonstrates its use during a field test at a 2.2 km optical range.
A system and methodologies for absolute quantum efficiency measurements from the vacuum ultraviolet through the near infrared
Authors: Jacquot Blake C. , Monacos Steve P. , Hoenk Michael E. , Greer Frank , Jones Todd J. , Nikzad Shouleh
Published: April 2011

In this paper we present our system design and methodology for making absolute quantum efficiency (QE) measurements through the vacuum ultraviolet (VUV) and verify the system with delta-doped silicon CCDs. Delta-doped detectors provide an excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for measuring QE through the VUV are more strenuous than measurements in the near UV and necessitate, among other things, the use of a vacuum monochromator, good dewar chamber vacuum to prevent on-chip condensation, and more stringent handling requirements.
A spectroscopic proton-exchange membrane fuel cell test setup allowing fluorescence x-ray absorption spectroscopy measurements during state-of-the-art cell tests
Authors: Petrova Olga , Kulp Christian , van den Berg Maurits W. E. , Klementiev Konstantin V. , Otto Bruno , Otto Horst , Lopez Marco , Bron Michael , Grünert Wolfgang
Published: April 2011

A test setup for membrane-electrode-assemblies (MEAs) of proton exchange membrane fuel cells which allows in situ fluorescence x-ray absorption spectroscopy studies of one electrode with safe exclusion of contributions from the counter electrode is described. Interference by the counter electrode is excluded by a geometry including a small angle of incidence (< 6°) between primary beam and electrode layer. The cell has been constructed by introducing just minor modifications to an electrochemical state-of-the-art MEA test setup, which ensures realistic electrochemical test conditions. This is at the expense of significant intensity losses in the path of the incident beam, which calls for the brilliance of third-generation synchrotrons to provide meaningful data. In measurements on Pt/C and Pt–Co/C cathodes combined with Pt–C anodes (H2/O2 feed), good data quality was demonstrated both for the majority element Pt as well as for Co despite of a low areal Co density in the order of 0.02 mg/cm2.
Dynamic kinetic energy potential for orbital-free density functional theory
Authors: Neuhauser Daniel , Pistinner Shlomo , Coomar Arunima , Zhang Xu , Lu Gang
Published: April 2011

A dynamic kinetic energy potential (DKEP) is developed for time-dependent orbital-free (TDOF) density function theory applications. This potential is constructed to affect only the dynamical (ω ≠ 0) response of an orbital-free electronic system. It aims at making the orbital-free simulation respond in the same way as that of a noninteracting homogenous electron gas (HEG), as required by a correct kinetic energy, therefore enabling extension of the success of orbital-free density functional theory in the static case (e.g., for embedding and description of processes in bulk materials) to dynamic processes. The potential is constructed by expansions of terms, each of which necessitates only simple time evolution (concurrent with the TDOF evolution) and a spatial convolution at each time-step. With 14 such terms a good fit is obtained to the response of the HEG at a large range of frequencies, wavevectors, and densities. The method is demonstrated for simple jellium spheres, approximating Na9+ and Na65+ clusters. It is applicable both to small and large (even ultralarge) excitations and the results converge (i.e., do not blow up) as a function of time. An extension to iterative frequency-resolved extraction is briefly outlined, as well as possibly numerically simpler expansions. The approach could also be extended to fit, instead of the HEG susceptibility, either an experimental susceptibility or a theoretically derived one for a non-HEG system. The DKEP potential should be a powerful tool for embedding a dynamical system described by a more accurate method (such as time-dependent density functional theory, TDDFT) in a large background described by TDOF with a DKEP potential. The type of expansions used and envisioned should be useful for other approaches, such as memory functionals in TDDFT. Finally, an appendix details the formal connection between TDOF and TDDFT.
Dynamics of two topologically entangled chains
Authors: Ferrari F. , Paturej J. , Pia̧tek M. , Vilgis T. A.
Published: April 2011

Starting from a given topological invariant, we argue that it is possible to construct a topological field theory with a finite number of Feynman diagrams and an amplitude of gauge invariant objects that is a function of that invariant. This is, for example, the case of the Gauss linking number and of the abelian BF models which have been already successfully applied in the statistical mechanics of polymers. In this work it is shown that a suitable generalization of the BF model can be applied also to polymer dynamics, where the polymer trajectories are not static, but change their shape during time.
Femtosecond inverse Faraday effect in magnetic ionic liquid [bmim]FeCl4
Authors: Jin Zuanming , Ma Hong , Li Dong , Ma Guohong , Wang Meng , Zhao Chongjun
Published: April 2011

The nonthermally photoinduced magnetization in a magnetic ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate ([bmim]FeCl4) is investigated via the inverse Faraday effect on the subpicosecond time scale at room temperature. The pump beam induced the ellipticity changes of probe beam are revealed to arise from the contributions of both the inverse Faraday effect and the optical Kerr effect. The formation of about 1.8 THz coherent superposition between magnetic sublevels of the Fe3+-ion’s ground-state multiplet is observed with a circular pump polarization, which is assigned to the allowed impulsively stimulated Raman scattering in the magnetic ion liquid.