Perpendicular Configuration Research Articles

Transport and AC loss properties of the repaired multifilamentary REBCO superconducting tapes

For near-future applications of REBa2Cu3O7 (REBCO) coated conductors to electric power cables, transformers and Superconducting Magnetic Energy Storage (SMES), the long taped wires with high performance in the transport properties have been designed and fabricated. Moreover, in order to drastically reduce AC losses in perpendicular field configuration, advanced multifilament YBCO coated conductors (MFYCCs) fabricated with technique of a laser scribing process have been also developed. In the present study, from engineering viewpoints to utilize such advanced conductors, we evaluated the transport and AC loss properties of short MFYCCs with a repaired part or a joint by a diffusion joint technique with the saddle-shaped pickup coil method.

Exchange bias in Pt doped NiMn thick films

Magnetization and electron spin resonance (ESR) measurements were carried out on a 1.2 at. % Pt doped NiMn thin film (8000 Å) in the temperature range of 5–200 K for both parallel (field parallel to the film surface) and perpendicular configurations. M versus H loops were recorded at selected temperatures. Magnetization curves in the parallel configuration differ from those in the perpendicular geometry in many respects, including the anisotropy fields derived from these curves, and the coercivity. In addition, the temperature dependences of the magnetization in a small negative field (−0.5 Oe) and several larger positive fields will also be reported. All of these phenomena can be understood by the coexistence of Mn-rich and Mn-deficient aggregated granular regions coupled antiferromagnetically. Furthermore, the exchange stiffness constant (D), bulk anisotropy constant, and surface anisotropy constant were deduced from ESR measurements. The fitted ESR parameters are in good agreement with the behavior deduced from magnetization.

Magnetoresistance effect in soft magnetic amorphous microwires

Results on the magnetoresistance (MR) effect in Co-based amorphous glass-coated microwires with nearly zero magnetostriction and no granular structure are reported. MR measurements have been performed in parallel and perpendicular configurations, in both low field and high field regimes. The results show that high field resistance variations are caused by the corresponding magnetization processes in both parallel and perpendicular configurations. In case of low parallel field, no resistance variation has been emphasized. A sharp MR response was observed in case of a perpendicularly applied low field and it was attributed to the interdomain wall between the inner core and the outer shell of such microwires. The sharpness of the low field MR peak can be controlled through the microwire dimensions. The results bring new information about the domain structure of amorphous microwires and open up new application opportunities for these materials.

Magnetic and magnetotransport properties of arrays of nanostructured antidots obtained by self-assembling polystyrene nanosphere lithography

A well-ordered nanopatterned structure has been obtained in sputtered magnetic thin films by self-assembling of polystyrene nanospheres. Arrays of holes in Co, Ni, and Ni80Fe20 films having a mean size ranging in the interval of 200–400 nm depending on the experimental condition have been prepared. Sample microstructure has been studied by scanning electron microscopy and atomic force microscopy. Room-temperature hysteresis loops have been measured in the parallel and perpendicular configuration (Hmax=20 kOe). Magnetoresistance (MR) measurements have been performed by means of a standard four-contact technique at several angles between the current and the magnetic field (Hmax=70 kOe) in the temperature interval of 4–200 K. An anisotropic MR effect has been observed in all compositions independent on the hole mean dimension. The role on magnetic and magnetotransport properties of either sample microstructure or composition has been studied in such patterned structures.

Pt / Co ] 4 / NiO thin film perpendicular magnetic anisotropy dependence on Co layer thickness

We have examined the dependence of the magnetism from perpendicular magnetic anisotropy with Co thickness in [Pt/Co] multilayers coupled to a NiO layer. We measure a perpendicular exchange bias field that changes polarity with Co thickness and find that with 2 nm of Co the perpendicular magnetic anisotropy is no longer present. Further evidence of the change in the Co layers preferred orientation is offered by zero field cooled susceptometry, where the low temperature susceptibility is negative for thin Co layers (0.9–1.2 nm) and becomes positive with increasing Co thickness (1.5–2.0 nm). Thin Co layered films also exhibit a compensation point around 100 K. These results indicate that the Co and NiO interface moments are coupled strongly and that there is competition between Pt/Co and Co/Ni at the film layer interfaces that sets the overall anisotropy from perpendicular and parallel configurations.

Computational characterisation of the charge-transfer and T-shaped molecular complexes of N-methyl imidazoline-2-thione and N-methyl imidazolidine-2-thione with the dihalogens Br2 and I2

The computational characterisation of the molecular complexes of N-methyl imidazoline-2-thione (methimazole) and the related saturated analogue N-methyl imidazolidine-2-thione with Br2 and I2 is carried out using quantum mechanical electronic structure methods. Two kinds of molecular connectivity have been examined. The first displays a collinear S–X–X geometry (X = Br, I) and leads to charge-transfer (CT) type adducts, possible in two stereoisomeric conformations depending on the direction of the X2-axis, either planar or perpendicular to the NCS plane. The second kind corresponds to T-shaped hypervalent complexes in which sulphur is connected to both the X atoms forming the linear X–S–X arrangement. The structural changes, the spectroscopic findings, the natural bond orbital analysis and the examination of the molecular orbital second-order perturbation energies give interesting information about the nature of the halogen bonding interaction between the electron-donor organic species and the electron-acceptor dihalogen molecule. Similar trends are followed by the energy and relative stability results including basis set superposition error corrections, which show the larger stabilisation of the planar CT conformers of both dihalogens vs. the perpendicular configurations. They also indicate the higher stability of the T-shaped bromine complexes relative to the CT species, opposite to the energy order of the corresponding diiodine adducts. A critical comparison is carried out with literature results on similar systems.

Investigation of the photoisomerisation process in four p-benzoxazoyl-substituted stilbenes

Fluorescence properties and trans-cis photoisomerisation of the benzoxazole derivatives 2-[4-(E)-(styryl)phenyl]benzoxazole (I), 2-{4-[(E)-2-(4-methoxyphenyl)vinyl]phenyl}benzoxazole (II), {4-[(E)-2-(4-benzoxazol-2-yl-phenyl)vinyl]phenyl}dimethylamine (III) and {4-[(E)-2-(4-benzoxazol-2-yl-phenyl)vinyl]phenyl}diphenylamine (IV) have been investigated in solvents of different polarities. It was found that these compounds exhibit efficient fluorescence with quantum yields and lifetimes strongly dependent on solvent polarity, although only compounds III and IV possess a significant charge transfer character in solvents of medium and high polarities. In addition, the photoisomerisation quantum efficiency depends strongly on the substitution of the phenyl ring in the electron donor moiety. A strong dependence of the quantum efficiency of the photoisomerisation on solvent was established. That quantity depends linearly on the non-radiative quantum yield of the deactivation of the excited singlet state for all investigated compounds. These results are consistent with a singlet state mechanism of the photoprocess. For compounds III and IV, with strong electron donors (N,N-dimethylaniline and triphenylamine), the molecule in the excited state trans configuration is more stabilized by solvent polarity than in the perpendicular form which causes more efficient isomerisation in nonpolar solvents. For compounds I and II the energy of the perpendicular configuration decreases more rapidly than that of the trans configuration when solvent polarity increases. In this case the energy barrier decreases with increasing solvent polarity. This makes the photoisomerisation process easier in polar solvents.

Structural Rearrangements in Self-Assembled Surfactant Layers at Surfaces

The transition from compact to extended configuration in ionic surfactant layers under the influence of salt, surfactant surface density, and temperature is studied using the classical density functional theory (cDFT). The increase in ionic strength of an aqueous salt solution or in the surfactant surface density leads to the transition from the hemicylindrical to the perpendicular monolayer configuration of the molecules. Although producing the same structural rearrangement in the surfactant layer, the origin of the effect of salt and surface density is different. While the addition of salt increases the out-of-plane attractive interactions with the solvent, the increase in density results in the increase in the in-plane repulsion in the surfactant layer. The temperature effects are subtler and are mainly manifested in the reduction of the solution structuring at elevated temperatures.

Electrodeposition of Ni/Co and Ni Magnetic Nanowires Using Allumina Template

Nickel and nickel-cobalt alloy nanowires were fabricated through template-assisted electrochemical deposition method and sandwiched between two caps of electrodeposited pure gold. Free standing porous alumina templates were prepared and used for the synthesis of the ordered nanowires. The morphology and composition of as-deposited nanowires were determined by scanning electron microscope. Nanowires were characterized by a diameter of 70 nm, as the alumina template pores diameter, and by a length in the range of 2-3 μm. Backscattered electron signal showed the presence of Au and Ni or Ni-Co sandwich, highlighting a well defined and void free interface between the gold caps and the Ni or Ni-Co layer. Particular optimization has been considered for the subsequent magnetoresistance characterization of nanowires. Angular dependence of magnetoresistance has been measured as a function of temperature from in-plane to perpendicular magnetic field configuration. Anisotropic magnetoresistive measurements suggested a magnetization process by magnetization rotation from nanowire axis towards in-plane orientation.

Magnetic measurements of Fe–Ni–Nb–B and Fe–Co–Mo–Cu–B in the vicinity of the Curie temperature

The study of the transition between ferromagnetic and paramagnetic states has been investigated on selected metallic glass systems based on Fe–Ni–Nb–B and Fe–Co–Mo–Cu–B with T C close to room temperature. Samples in the form of ribbons were prepared by planar flow casting and magnetostriction in parallel and perpendicular directions and saturation magnetostrictions have been determined on these samples in as-cast states together with hysteresis loops. In addition, a magneto-optic device for dynamic domain observation has been used for observation of domain structure. Magnetostriction measurements using direct method of measurement show the decrease of saturation magnetostriction towards zero upon approaching T C. In paramagnetic state the field dependencies of magnetostriction in parallel and perpendicular configurations exhibit a linear dependence on the external magnetic field. In the transition region of temperatures the dependencies are a combination of ferromagnetic and paramagnetic field dependencies. The coercivity H C in the materials investigated exhibits values below 20 A/m. The observed magnetic domains are typical for this class of amorphous alloys. The polarization in paramagnetic state increases gradually with increase in magnetizing field, reflecting the increasing amount of polarized regions.

Comparing detection and location performance of perpendicular and parallel broadside GPR antenna orientations

GPR (Ground Penetrating Radar) results are shown for perpendicular broadside and parallel broadside antenna orientations. Performance in detection and localization of concrete tubes and steel tanks is compared as a function of acquisition configuration. The comparison is done using 100 MHz and 200 MHz center frequency antennas. All tubes and tanks are buried at the geophysical test site of IAG/USP in São Paulo city, Brazil. The results show that the long steel pipe with a 38-mm diameter was well detected with the perpendicular broadside configuration. The concrete tubes were better detected with the parallel broadside configuration, clearly showing hyperbolic diffraction events from all targets up to 2-m depth. Steel tanks were detected with the two configurations. However, the parallel broadside configuration was generated to a much lesser extent an apparent hyperbolic reflection corresponding to constructive interference of diffraction hyperbolas of adjacent targets placed at the same depth. Vertical concrete tubes and steel tanks were better contained with parallel broadside antennas, where the apexes of the diffraction hyperbolas better corresponded to the horizontal location of the buried target disposition. The two configurations provide details about buried targets emphasizing how GPR multi-component configurations have the potential to improve the subsurface image quality as well as to discriminate different buried targets. It is judged that they hold some applicability in geotechnical and geoscientific studies.

Membrane Binding by the Endophilin N-BAR Domain

The structure of the endophilin N-terminal amphipathic helix Bin/Amphiphysin/Rvs-homology (N-BAR) domain is unique because of an additional insert helix under the arch of the N-BAR dimer. The structure of this additional helix has not been fully resolved in crystallographic studies, and thus presents a challenge to molecular-level analysis. Large-scale molecular-dynamics simulations were therefore employed to investigate the interaction of a single endophilin N-BAR with a lipid bilayer. Various possible configurations of the additional insert helix under the top of the arch of the endophilin N-BAR were modeled to examine their effect on membrane bending. A residue-residue and residue-lipid headgroup distance analysis, similar to that performed with electron paramagnetic resonance spectroscopy, revealed that the insert helix remains perpendicular to the long axis of the N-BAR over the duration of the simulations. It was also found that the degree of membrane bending is directly related to the orientation of the additional insert helix, and that the perpendicular configuration generates the largest curvature consistent with mutation experiments. In addition, the angle formed between the two N-BAR monomers at the top of the arch is sensitive to the orientation of the insert helices. A membrane sensing-binding-bending mechanism is proposed to describe the process of an endophilin N-BAR interaction with a membrane.

Time-Resolved Dynamics of NO2 in Its Conical Intersection Region

Photodissociation dynamics of NO(2) in its conical intersection region have been explored experimentally on a real-time scale by time-of-flight mass spectrometry. Excited at 400.6 nm and probed by 801.6 nm femtosecond laser pulses, different dynamical behaviors of both the parent ion NO(2)(+) and the fragment ion NO(+) have been observed under parallel and perpendicular pump-probe laser polarization configurations. Distinct oscillations in NO(2)(+) and NO(+) signals are observed when laser polarizations of pump and probe are perpendicular to each other, whereas the oscillations become blurry when the laser polarizations are parallel. The observed transient signals imply that the dissociation mechanism of NO(2) in the A(2)B(2) excited state needed to be reconsidered. On the basis of our observation, Rydberg states play important roles in the ultrafast dissociation dynamics of NO(2).

RQM description of the charge form factor of the pion and its asymptotic behavior

The pion charge and scalar form factors, $F_1(Q^2)$ and $F_0(Q^2)$, are first calculated in different forms of relativistic quantum mechanics. This is done using the solution of a mass operator that contains both confinement and one-gluon-exchange interactions. Results of calculations, based on a one-body current, are compared to experiment for the first one. As it could be expected, those point-form, and instant and front-form ones in a parallel momentum configuration fail to reproduce experiment. The other results corresponding to a perpendicular momentum configuration (instant form in the Breit frame and front form with $q^+=0$) do much better. The comparison of charge and scalar form factors shows that the spin-1/2 nature of the constituents plays an important role. Taking into account that only the last set of results represents a reasonable basis for improving the description of the charge form factor, this one is then discussed with regard to the asymptotic QCD-power-law behavior $Q^{-2}$. The contribution of two-body currents in achieving the right power law is considered while the scalar form factor, $F_0(Q^2)$, is shown to have the right power-law behavior in any case. The low-$Q^2$ behavior of the charge form factor and the pion-decay constant are also discussed.}

Influence of flow confinement on the drag force on a static cylinder

The influence of confinement on the drag force F on a static cylinder in a viscous flow inside a rectangular slit of aperture h0 has been investigated from experimental measurements and numerical simulations. At low enough Reynolds numbers, F varies linearly with the mean velocity and the viscosity, allowing for the precise determination of drag coefficients λ∥ and λ⊥ corresponding, respectively, to a mean flow parallel and perpendicular to the cylinder length L. In the parallel configuration, the variation in λ∥ with the normalized diameter β=d/h0 of the cylinder is close to that for a two-dimensional (2D) flow invariant in the direction of the cylinder axis and does not diverge when β=1. The variation in λ∥ with the distance from the midplane of the model reflects the parabolic Poiseuille profile between the plates for β⪡1 while it remains almost constant for β∼1. In the perpendicular configuration, the value of λ⊥ is close to that corresponding to a 2D system only if β⪡1 and/or if the clearance between the ends of the cylinder and the side walls is very small: in that latter case, λ⊥ diverges as β→1 due to the blockage of the flow. In other cases, the side flow between the ends of the cylinder and the side walls plays an important part to reduce λ⊥: a full three-dimensional description of the flow is needed to account for these effects.

Magnetoresistance fluctuations in a weak disorder indium nitride nanowire

We report measurements of magnetoresistance (MR) fluctuations in a weak disorder indium nitride nanowire. The MR fluctuations are reproducible, aperiodic and symmetric in magnetic field but are asymmetric upon reversal of bias direction. The fluctuations are analysed for both perpendicular and parallel external magnetic field configurations in the light of tunnel magnetoresistance at low field and impurity scattering at higher field. The asymmetry in bias reversal is caused by breakdown of time reversal symmetry.

Effect of efficiency “droop” in violet and blue InGaN laser diodes

We have studied two types of InGaN laser diodes emitting at 410 and 440 nm. Each device was characterized by measuring light-current characteristics in two geometries for which the light was collected: along the resonator and perpendicularly to the cavity. In the first configuration, the 410 nm device displays no reduction of differential efficiency while 440 nm laser shows evidence of droop. In the perpendicular configuration both devices show the pronounced droop. We associate the suppression of the droop for 410 nm laser in the “along cavity” configuration with the appearance of the stimulated recombination.

Tertiary Motifs Revealed in Analyses of Higher-Order RNA Junctions

RNA junctions are secondary-structure elements formed when three or more helices come together. They are present in diverse RNA molecules with various fundamental functions in the cell. To better understand the intricate architecture of three-dimensional (3D) RNAs, we analyze currently solved 3D RNA junctions in terms of base-pair interactions and 3D configurations. First, we study base-pair interaction diagrams for solved RNA junctions with 5 to 10 helices and discuss common features. Second, we compare these higher-order junctions to those containing 3 or 4 helices and identify global motif patterns such as coaxial stacking and parallel and perpendicular helical configurations. These analyses show that higher-order junctions organize their helical components in parallel and helical configurations similar to lower-order junctions. Their sub-junctions also resemble local helical configurations found in three- and four-way junctions and are stabilized by similar long-range interaction preferences such as A-minor interactions. Furthermore, loop regions within junctions are high in adenine but low in cytosine, and in agreement with previous studies, we suggest that coaxial stacking between helices likely forms when the common single-stranded loop is small in size; however, other factors such as stacking interactions involving noncanonical base pairs and proteins can greatly determine or disrupt coaxial stacking. Finally, we introduce the ribo–base interactions: when combined with the along-groove packing motif, these ribo–base interactions form novel motifs involved in perpendicular helix–helix interactions. Overall, these analyses suggest recurrent tertiary motifs that stabilize junction architecture, pack helices, and help form helical configurations that occur as sub-elements of larger junction networks. The frequent occurrence of similar helical motifs suggest nature's finite and perhaps limited repertoire of RNA helical conformation preferences. More generally, studies of RNA junctions and tertiary building blocks can ultimately help in the difficult task of RNA 3D structure prediction.

High-field recovery of the undistorted triangular lattice in the frustrated metamagnetCuFeO2

Pulsed-field magnetization experiments extend the typical metamagnetic staircase of ${\text{CuFeO}}_{2}$ up to 58 T to reveal an additional first-order phase transition at high field for both the parallel and perpendicular field configuration. Virtually complete isotropic behavior is retrieved only above this transition, indicating the high-field recovery of the undistorted triangular lattice. A consistent phenomenological rationalization for the field dependence and metamagnetism crossover of the system is provided, demonstrating the importance of both spin-phonon coupling and a small field-dependent easy-axis anisotropy in accurately describing the magnetization process of ${\text{CuFeO}}_{2}$.

2-(2,4-Dichlorophenyl)-9-phenyl-2,3-dihydrothieno[3,2-b]quinoline

In the title compound, C23H15Cl2NS, the quinoline system is almost planar [r.m.s. deviation = 0.013 (2) Å]. The phenyl group is disordered over two positions with site occupancies of 0.55 and 0.45, and is oriented in a nearly perpendicular configuration to the quinoline ring [the dihedral angles between the quinoline ring and the major and minor disordered components of the phenyl ring are 81.8 (2) and 71.6 (2)°, respectively]. The dihydro­thiene ring adopts an envelope conformation. The dihedral angle between the chloro­phenyl ring and the quinoline system is 79.32 (1)°. In the crystal weak C—H⋯π inter­actions occur.