Planar Phase Research Articles

Phase Structure Transition and Properties of Salt-Free Phosphoric Acid/Non-ionic Surfactants in Water.

Precise control of phase structure transition for the synthesis of multi-dimensional soft materials is a fascinating target in amphiphilic molecule self-assembly. Here, we demonstrate a spontaneous formation of a closely packed lamellar phase consisting of uni- and multi-lamellar vesicles through the incorporation of a small amount of an extractant, di(2-ethylhexyl)phosphoric acid (DEHPA), into the highly swollen, planar lamellar phase of a non-ionic tetraethylene glycol monododecyl ether (C12EO4) surfactant in water. It is figured out that the introduction of negative membrane charges results in the electrostatic repulsion among the lamellae, which suppresses the Helfrich undulation and induces a phase structure transition from planar lamellae to closely packed vesicles. Our results provide important insight into amphiphilic molecule self-assembly, where additives and pH can satisfy the opportunities for the precise tuning of the lamellar structures, which makes a way for the development of lamellar soft materials.

Surface profile and stress field evaluation using digital gradient sensing method

Shape and surface topography evaluation from measured orthogonal slope/gradient data is of considerable engineering significance since many full-field optical sensors and interferometers readily output such a data accurately. This has applications ranging from metrology of optical and electronic elements (lenses, silicon wafers, thin film coatings), surface profile estimation, wave front and shape reconstruction, to name a few. In this context, a new methodology for surface profile and stress field determination based on a recently introduced non-contact, full-field optical method called digital gradient sensing (DGS) capable of measuring small angular deflections of light rays coupled with a robust finite-difference-based least-squares integration (HFLI) scheme in the Southwell configuration is advanced here. The method is demonstrated by evaluating (a) surface profiles of mechanically warped silicon wafers and (b) stress gradients near growing cracks in planar phase objects.

Large N Limits in Tensor Models: Towards More Universality Classes of Colored Triangulations in Dimension d≥2

We review an approach which aims at studying discrete (pseudo-)manifolds in dimension $d\geq 2$ and called random tensor models. More specifically, we insist on generalizing the two-dimensional notion of $p$-angulations to higher dimensions. To do so, we consider families of triangulations built out of simplices with colored faces. Those simplices can be glued to form new building blocks, called bubbles which are pseudo-manifolds with boundaries. Bubbles can in turn be glued together to form triangulations. The main challenge is to classify the triangulations built from a given set of bubbles with respect to their numbers of bubbles and simplices of codimension two. While the colored triangulations which maximize the number of simplices of codimension two at fixed number of simplices are series-parallel objects called melonic triangulations, this is not always true anymore when restricting attention to colored triangulations built from specific bubbles. This opens up the possibility of new universality classes of colored triangulations. We present three existing strategies to find those universality classes. The first two strategies consist in building new bubbles from old ones for which the problem can be solved. The third strategy is a bijection between those colored triangulations and stuffed, edge-colored maps, which are some sort of hypermaps whose hyperedges are replaced with edge-colored maps. We then show that the present approach can lead to enumeration results and identification of universality classes, by working out the example of quartic tensor models. They feature a tree-like phase, a planar phase similar to two-dimensional quantum gravity and a phase transition between them which is interpreted as a proliferation of baby universes.

Anomalous Refraction of Acoustic Guided Waves in Solids with Geometrically Tapered Metasurfaces.

The concept of a metasurface opens new exciting directions to engineer the refraction properties in both optical and acoustic media. Metasurfaces are typically designed by assembling arrays of subwavelength anisotropic scatterers able to mold incoming wave fronts in rather unconventional ways. The concept of a metasurface was pioneered in photonics and later extended to acoustics while its application to the propagation of elastic waves in solids is still relatively unexplored. We investigate the design of acoustic metasurfaces to control elastic guided waves in thin-walled structural elements. These engineered discontinuities enable the anomalous refraction of guided wave modes according to the generalized Snell's law. The metasurfaces are made out of locally resonant toruslike tapers enabling an accurate phase shift of the incoming wave, which ultimately affects the refraction properties. We show that anomalous refraction can be achieved on transmitted antisymmetric modes (A_{0}) either when using a symmetric (S_{0}) or antisymmetric (A_{0}) incident wave, the former clearly involving mode conversion. The same metasurface design also allows achieving structure embedded planar focal lenses and phase masks for nonparaxial propagation.

Spike-adding in parabolic bursters: The role of folded-saddle canards

The present work develops a new approach to studying parabolic bursting, and also proposes a novel four-dimensional canonical and polynomial-based parabolic burster. In addition to this new polynomial system, we also consider the conductance-based model of the Aplysia R15 neuron known as the Plant model, and a reduction of this prototypical biophysical parabolic burster to three variables, including one phase variable, namely the Baer–Rinzel–Carillo (BRC) phase model. Revisiting these models from the perspective of slow–fast dynamics reveals that the number of spikes per burst may vary upon parameter changes, however the spike-adding process occurs in an explosive fashion that involves special solutions called canards. This spike-adding canard explosion phenomenon is analysed by using tools from geometric singular perturbation theory in tandem with numerical bifurcation techniques. We find that the bifurcation structure persists across all considered systems, that is, spikes within the burst are incremented via the crossing of an excitability threshold given by a particular type of canard orbit, namely the true canard of a folded-saddle singularity. However there can be a difference in the spike-adding transitions in parameter space from one case to another, according to whether the process is continuous or discontinuous, which depends upon the geometry of the folded-saddle canard. Using these findings, we construct a new polynomial approximation of the Plant model, which retains all the key elements for parabolic bursting, including the spike-adding transitions mediated by folded-saddle canards. Finally, we briefly investigate the presence of spike-adding via canards in planar phase models of parabolic bursting, namely the theta model by Ermentrout and Kopell.

Screening for total ergot alkaloids in rye flour by planar solid phase extraction–fluorescence detection and mass spectrometry

The analysis of ergot alkaloids is generally performed by high-performance liquid chromatography (HPLC) coupled to fluorescence detection (FLD) or mass selective detection. As for monitoring only the sum of ergot alkaloids is relevant, a fast and easy screening method for the determination of the total alkaloid content was developed using planar solid phase extraction (pSPE). Applying pSPE, recently introduced for pesticide residue analysis in fruits and vegetables (Oellig and Schwack, 2011) and tea (Oellig and Schwack, 2012), all ergot alkaloids are concentrated in a target zone followed by detection as the sum. The herein presented method includes an ammonium acetate buffered extraction step, followed by a fast liquid–liquid partitioning pre-cleaning before pSPE is performed on high-performance thin-layer chromatography (HPTLC) amino plates with a single methanol development to separate the ergot alkaloids from the remaining matrix and to collect them in a single zone. For quantitation, the native fluorescence was used after dipping the plate in n-hexane/paraffin solution for fluorescence enhancement. Limits of detection and quantitation of 0.07 and 0.24mg/kg rye, respectively, expressed as ergocristine, were well below the currently applied quality criterion limit for rye. Near-100% recoveries were obtained at relevant spiking levels for different rye flour samples. Hence, the fast pSPE–FLD is an efficient and reliable method to screen for the total ergot alkaloid content in rye and a rapid alternative to the HPLC determination of individual alkaloids and to summing them up. HPTLC–MS additionally enables the identification of the ergot alkaloid composition by a single mass spectrum, when utilized as a fingerprint, offering an easy differentiation of Secale cornutum from different origins.

Symmetry-Protected Topological Superfluids and Superconductors —From the Basics to3He—

In this article, we give a comprehensive review of recent progress in research on symmetry-protected topological superfluids and topological crystalline superconductors, and their physical consequences such as helical and chiral Majorana fermions. We start this review article with the minimal model that captures the essence of such topological materials. The central part of this article is devoted to the superfluid $^3$He, which serves as a rich repository of novel topological quantum phenomena originating from the intertwining of symmetries and topologies. In particular, it is emphasized that the quantum fluid confined to nanofabricated geometries possesses multiple superfluid phases composed of the symmetry-protected topological superfluid B-phase, the A-phase as a Weyl superfluid, the nodal planar and polar phases, and the crystalline ordered stripe phase. All these phases generate noteworthy topological phenomena, including topological phase transitions concomitant with spontaneous symmetry breaking, Majorana fermions, Weyl superfluidity, emergent supersymmetry, spontaneous edge mass and spin currents, topological Fermi arcs, and exotic quasiparticles bound to topological defects. In relation to the mass current carried by gapless edge states, we also briefly review a longstanding issue on the intrinsic angular momentum paradox in $^3$He-A. Moreover, we share the current status of our knowledge on the topological aspects of unconventional superconductors, such as the heavy-fermion superconductor UPt$_3$ and superconducting doped topological insulators, in connection with the superfluid $^3$He.

Cerebrospinal Fluid Flow Studies and Recent Advancements

This article provides an overview of magnetic resonance imaging (MRI) techniques used to assess cerebrospinal fluid (CSF) movement in the central nervous system (CNS), including Phase-Contrast (PC), Time-Spatial Labeling Inversion Pulse, and simultaneous multi slice echo planar phase contrast imaging. These techniques have been used to assess CSF movement in the CNS under normal and pathophysiological situations. PC can quantitatively measure stroke volume in selected regions, particularly the aqueduct of Sylvius, as synchronized to the heartbeat. The PC is frequently used to investigate those patients with suspected normal pressure hydrocephalus and a Chiari I malformation. Time-Spatial Labeling Inversion Pulse, with high signal-to-noise ratio, captures motion of CSF anywhere in the CNS over a time period of up to 5 seconds. Variations of PC-MRI improved temporal resolution and included contributions from respiration. With non-invasive imaging such as these, more can be understood about CSF dynamics, especially with respect to the relative effects of cardiac and respiratory changes on CSF movement.

Crystal-Phase Control by Solution-Solid-Solid Growth of II-VI Quantum Wires.

A simple and potentially general means of eliminating the planar defects and phase alternations that typically accompany the growth of semiconductor nanowires by catalyzed methods is reported. Nearly phase-pure, defect-free wurtzite II-VI semiconductor quantum wires are grown from solid rather than liquid catalyst nanoparticles. The solid-catalyst nanoparticles are morphologically stable during growth, which minimizes the spontaneous fluctuations in nucleation barriers between zinc blende and wurtzite phases that are responsible for the defect formation and phase alternations. Growth of single-phase (in our cases the wurtzite phase) nanowires is thus favored.

Molecular structure and vibrations of NTCDA monolayers on Ag(111) from density-functional theory and infrared absorption spectroscopy.

The structure and vibrational properties of the metal-organic interface of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) on Ag(111) were analysed using Fourier-transform infrared absorption spectroscopy in conjunction with density functional theory calculations including dispersion forces (PBE-D3). Mode assignments and polarizations as well as molecular distortions were determined for four adsorption geometries of NTCDA on top and bridge sites aligned either parallel or perpendicular to the Ag rows and compared to accurate calculations of the free molecule. This enables an in-depth understanding of surface effects on the computed and experimental vibrational spectra of the adsorbed NTCDA molecule. The molecule-substrate interaction comprises two major and equally important contributions: non-directional van der Waals forces between molecule and surface, and covalent bonding of the acyl oxygen atoms with underlying Ag atoms, which is quantified by charge-transfer analysis. Furthermore, adsorption energy calculations showed that the molecular axis of flat-lying NTCDA is oriented preferably in parallel to the Ag rows. The molecule is subject to particular distortions from the planar gas phase structure with covalent bonding leading to downward bending of the acyl oxygen atoms and Pauli repulsion to upward bending of the carbon core. In parallel, strong buckling of the silver surface was identified. As found in previous studies, the lowest unoccupied molecular orbital (LUMO) of the molecule slips below the Fermi level and becomes partially populated upon adsorption. Excitation of totally symmetric vibrational modes then leads to substantial interfacial dynamical charge transfer, which is convincingly reproduced in the calculated IR spectra.

A Low-Profile Printed Planar Phase Correcting Surface to Improve Directive Radiation Characteristics of Electromagnetic Band Gap Resonator Antennas

This communication presents a method to enhance the radiation performance of conventional electromagnetic band gap resonator antennas (ERAs) by improving their aperture phase distributions. A low-profile printed planar phase correcting surface (PCS) was designed and fabricated to demonstrate performance enhancement. Measurements of a prototype demonstrated that the PCS significantly enhances the directive radiation properties of ERAs. This includes an 8 dB increase in peak directivity, 60% reduction in 3 dB beamwidth (from 35° to 14°), and a considerable reduction in side lobe levels.

Ultrafast laser inscription of volume phase gratings with low refractive index modulation and self-images of high visibility.

Ultrafast laser inscription of volume phase gratings with low index contrast and self-images with visibility of 0.96 is demonstrated. It is also demonstrated that phase differences of π/2 for visible light are achievable with only one layer of structures induced in bulk borosilicate glass by direct laser writing. The fabrication method avoids the stitching of several layers of structures and significantly reduces the time of process. The increment of visibility with the induced phase difference is proved and results are compared with the expected for planar phase gratings.

Design and Characterization of a 170-GHz Resonant Diplexer for High-Power ECRH Systems

The development of resonant diplexers for millimeter waves can improve the flexibility, simplify the system complexity, and extend the performance of electron cyclotron resonance heating (ECRH) systems. A 170-GHz quasi-optical resonant diplexer consisting of two phase inversion mirrors and two planar phase gratings, which is compatible with ECHR for the international experimental tokamak reactor (ITER), has been realized and tested. In order to make the structure of the diplexer simple, the $LP_{01}$ beam is used directly without being converted into a Gaussian-beam. The beam propagation inside of the diplexer is presented and the working principles of each component are discussed in details. A resonator technique is applied to study the transmission characteristics by creating a high-Q-factor resonator with high sensitivity to any small variations of the diplexer. Numerical simulations and experimental measurements are in good agreement, showing a transmission efficiency of the resonant channel and the nonresonant channel of 0.95 and 0.97, respectively. The mode output and mode filtering of the resonant channel is investigated by changing the input modes, and the average wrong mode suppression for low-order modes is 8 dB and for very high-order modes reach 17.5 dB. The isolation of the diplexer is tested by measuring the power of the $LP_{01}$ mode in the isolated port for different loads at the outputs. The obtained results demonstrate the possibility of reducing the complexity of large ECRH systems, filtering the wrong modes in the transmission line system, as well as receiving electron cyclotron emission radiation from the plasma by sharing the launcher with the transmitted ECRH.

A planar microwave phase shifter using microstrip–CPW–microstrip transition with defected ground structures

A novel planar printed phase shifter design is proposed in this paper. The design is developed with microstrip–conductor-backed coplanar waveguide– microstrip (MP–CBCPW–MP) transition line with different defected ground structures (DGS). The differential phase shift can be controlled by altering the DGS dimensions. Three prototypes with DGS dimensions 5 × 10, 10 × 20, and 10 × 30 mm2, are employed at the finite ground plane to achieve 5°, 20°, and 30° shift in phase respectively and are validated with the phase delay relation. The prominent effect of the transition region is to confine the field area. The resonance is at 700 MHz with a bandwidth of 400 MHz (0.4–0.8 GHz). The proposed phase shifter can be used for broadcasting applications. The proposed MP–CBCPW–MP transition phase shifter design with DGS is simulated, fabricated, and measured to analyze its performance.

Influence of SDS on the Lα-phases of siloxane surfactant swollen by glycerol

The interaction between SDS and the swollen lamellar phase of an A-B-A type nonionic siloxane surfactant IM-22 in 60 % glycerol has been investigated with macroscopic phase observation, FF-TEM, SAXS, conductivity, and rheology experiments. Without addition of SDS, 20 % IM-22 forms highly swollen planar lamellar phase stabilized by strong thermal undulations. Upon addition of 1 mM SDS, the lamellae were transformed into giant multilamellar vesicles. The size of the vesicles decreases with increasing the amount of SDS below 5 mM whereas the number density of the vesicles increases. Further increasing the concentration of SDS leads to break of the vesicles. In this self-assembly transition process, the viscosity of the system exhibits maximum at 5 mM SDS, where the system owns property of gels. Conductivity measurements suggest that SDS starts to bind IM-22 at a concentration below 2 mM, but SAXS results reveal that the interlamellar spacings were not affected up to 5 mM. This was explained by the special interactions in this system. On the one hand, the ionization degree of SDS in 60 % glycerol is very low due to the low dielectric constant, which results in lower charge density in the lamellae. Therefore, thermal undulations dominate the electrostatic forces at SDS concentration below 5 mM. On the other hand, the mutual phobic nature of SDS with IM-22 allows break of the lamellae at higher SDS concentrations.

Triband phase shifter design using split-ring resonator and complementary split-ring resonator-loaded ground plane for wireless applications

This paper presents the design of a novel linear analog planar phase shifter deploying split-ring resonator (SRR) and complementary split-ring resonator (CSRR) structures. Based on the advantages of these structures, a triband phase shifter is designed for multiple target systems to operate at 0.85, 1.69, and 2.46 GHz bands finding applications for European RFIDs, Satellite Radio Broadcast System, Mobile Services, and ISM Band, respectively. The effect of SRR and CSRR coupling with host transmission line is also analyzed on the basis of Bloch mode theory and the modes are validated through Eigen mode analysis. The proposed phase shifter design shows a good agreement between simulated and measured results. A 90° ± 8° shift in phase is observed at lower and upper bands, and a 135° ± 8° shift is observed in center band with reasonable group delay components.

Electronic properties of monolayer and bilayer arsenene under in-plain biaxial strains

Using first-principles density functional theory, we have investigated the mechanical and electronic properties of monolayer and bilayer arsenenes under in-plain biaxial strains. It is interesting to find that under large enough tensile strains, the monolayer arsenene transfers from buckled honeycomb structure to planar honeycomb phase while the interlayer distance D of bilayer arsenene maintains at about 1.371Å. Both monolayer and bilayer arsenenes possess indirect band gaps and their electronic properties can be tuned via in-plane biaxial strains. The variations of the band gap energy are diverse with respect to the compressive and tensile biaxial strains. Under compressive strains, the band gap of both monolayer and bilayer arsenenes initially increases, and then rapidly decreases. In addition, the monolayer arsenene exhibits an indirect-to-direct band gap transition when the compressive strains reach to −10%. However, under tensile strains, the band gap of monolayer arsenene monotonously decreases with the strains, while the band gap of bilayer arsenene reduces quickly to zero under small tensile strains. Our present results will be conductive to design strain-based arsenene materials for applications in nanoelectronic and optoelectronic devices.

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

The self-assembled formation of ordered, vertically stacked rocksalt/wurtzite MgxZn1−xO heterostructures by planar phase separation is shown. These heterostructures form quasi “natural” two-dimensional hetero-interfaces between the different phases upon annealing of MgO-oversaturated wurtzite MgxZn1−xO layers grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates. The optical absorption spectra show a red shift simultaneous with the appearance of a cubic phase upon annealing at temperatures between 900 °C and 1000 °C. Transmission electron microscopy reveals that these effects are caused by phase separation leading to the formation of a vertically ordered rock salt/wurtzite heterostructures. To explain these observations, we suggest a phase separation epitaxy model that considers this process being initiated by the formation of a cubic (Mg,Zn)Al2O4 spinel layer at the interface to the sapphire substrate, acting as a planar seed for the epitaxial precipitation of rock salt MgxZn1−xO. The equilibrium fraction x of magnesium in the resulting wurtzite (rock salt) layers is approximately 0.15 (0.85), independent of the MgO content of the as-grown layer and determined by the annealing temperature. This model is confirmed by photoluminescence analysis of the resulting layer systems after different annealing temperatures. In addition, we show that the thermal annealing process results in a significant reduction in the density of edge- and screw-type dislocations, providing the possibility to fabricate high quality templates for quasi-homoepitaxial growth.

Diffusion of lithium ions and diffusion-induced stresses in a phase separating electrode under galvanostatic and potentiostatic operations: Phase field simulations

Phase separation in an electrode of a lithium ion battery, which is a phenomenon where an active electrode material is separated into Li-rich and Li-poor phases, exists widely in many active materials and has significant impacts on the diffusion of lithium ions and diffusion-induced stresses. A phase field model is developed to study the phase separation. Firstly, the influences of various energies, such as the free energy of uniform Li-ion concentration, gradient energy and elastic energy, on phase separation are discussed. Secondly, the impacts of charge operation, e.g. galvanostatic and potentiostatic, on Li-ion diffusion and diffusion-induced stresses in a planar phase separating electrode are investigated. Calculations are also made for single phase electrodes based on Fick’s law for comparison. The obtained simulation results show that the Li-ion diffusion in a phase separating electrode depends significantly on the phase separating profile and movement of phase boundary, but it is not sensitive to charge operation. The diffusion-induced stresses also separate into high and low stress regions. Finally, based on the diffusion process and diffusion-induced stress, it is suggested that phase separation should be avoided for the sake of fast charging and mechanical reliability.

Integrated Microwave Front-Ends with Avionics Applications [Book\/Software Reviews

This book has a total of 14 chapters, covering planar transmission lines, lump elements, directional couplers, filters, switches, limiters, phase shifters, duplexers, low-noise amplifiers, and mixers. The author also introduces a variety of avionics equipment, such as XPDR (transponder), distance measuring equipment (DME), universal access transceiver (UAT), automatic dependent surveillance-broadcast (ADS-B), traffic collision avoidance system, and antennas,along with the design and fabrication technology. This book, overall, is very practical and useful to the design and field engineers in RF/microwave and avionics. It can serve as a field guide for experienced engineers as well as a beginner.