Symmetric Probe Research Articles

Ultra-Wideband Circular Polarized Implantable Patch Antenna for Implantable Blood Glucose Detection System Applications.

To address the current demands for antenna miniaturization, ultra-bandwidth, and circular polarization in advanced medical devices, a novel ISM band implantable antenna for blood glucose monitoring has been developed. This antenna achieves miniaturization by incorporating slots in the radiation patch and adding symmetric short-circuit probes, resulting in a compact size of only 0.054λ0 × 0.054λ0 × 0.005λ0 (λ0 is the wavelength in free space in respect of the lowest working frequency). By combining two resonance points and utilizing a differential feed structure, the antenna achieves ultra-broadband and circular polarization. Simulations indicate a |S11| bandwidth of 1.1 GHz (1.65-2.75 GHz) and an effective axial ratio (based on 3 dB axis ratio) bandwidth of 590 MHz (1.89-2.48 GHz), able to cover both the ISM frequency band (2.45 GHz) and the mid-field frequency band (1.9 GHz). The antenna exhibits CP gains of -20.04 dBi at a frequency of 2.45 GHz, while it shows gains of -24.64 dBi at 1.9 GHz. Furthermore, a superstrate layer on the antenna's radiating surface enhances its biocompatibility and minimizes its impact on the human body. Simulation and experimental results indicate that the antenna can establish a stable wireless communication link for implantable continuous blood glucose monitoring systems.

A bichromophoric squaraine based NIR fluorescent probe for G-quadruplex in living cells

The polymorphic formation of G-quadruplex brings more attentions, because changes of formation sites affect many physiological processes, like telomere maintenance, transcription and DNA replication. These processes are highly susceptible to ROS-induced oxidative damage. In this work, bichromophoric cores of symmetric squaraine probe SQ linked with ether chain is conducive to the recognition of G-quadruplex, based on the mechanism of intra or intermolecular “aggregation-disaggregation”. Several interaction behaviors, such as self-aggregation, binding affinity, stoichiometric ratio, were fully investigated via spectrum titration, circular dichroism, fluorescent intercalator displacement assay, and molecular docking. Furthermore, tracking G-quadruplex distribution in the cytoplasm was monitored by SQ during the oxidative stress enhancement. Interestingly, the G-quadruplex levels in the cytoplasm of cancer cells were slightly higher than that of normal cells to deal with oxidation-reduction imbalance. Overall, the lower detection limit of SQ for parallel G-quadruplex like pu27 is as low as 7.2 nM; and the complex of SQ and G-quadruplex will not change the topological structure of G-quadruplex. It has good sensitive and stability for parallel type of G-quadruplex. It is a potential tool for bioimaging of G-quadruplex in the cytoplasm.

A harmonic method for measuring electron temperature and ion density using an asymmetric double probe

The harmonic method using a symmetric double probe was developed for measuring electron temperature and ion density Oh et al (2012 Meas. Sci. Technol. 23 085001). When an alternating voltage is applied to the symmetric double probe where the two areas of the collector for current collection are equal, the fundamental frequency current and third harmonic currents are generated. The electron temperature and ion density are obtained by measuring the fundamental frequency current and the third harmonic current. However, it is observed that the third harmonic current can rapidly decrease to the level of base noise when the ratio of the applied voltage to the electron temperature decreases. Therefore, it is necessary to increase the harmonic currents generated to improve measurement accuracy for electron temperature and ion density. In this paper, a harmonic method using an asymmetric double probe with different collection areas is proposed to measure electron temperature and ion density. By using the double probe with different collector area, the fundamental frequency current and the second harmonic current are generated. In the proposed method, the electron temperature and ion density are obtained by measuring the fundamental frequency current and the second harmonic current. It is found that the accuracy of the electron temperature can be improved by measuring the second harmonic rather than measuring the third harmonic current. For quantitative comparison, the electron temperature and ion density obtained by the proposed method were compared with the electron temperature and electron density obtained by the measurement electron energy probability function, which showed good agreement between them in argon plasma at various conditions. In addition, it was experimentally verified that the electron temperature can be accurately measured even when the chamber is electrically insulated, and a dielectric layer is deposited on the collectors of the double probe, such as in the plasma process.

Bright Asymmetric Shielding Strategy-Based NIR-II Probes for Angiography and Localized Photothermal Therapy.

Fluorescent probes with fluorescence emission in the NIR-II window have been widely studied due to increased imaging depth. However, the currently reported NIR-II fluorescent probes present some disadvantages, such as complicated synthesis routes and low fluorescence quantum yields (QYs). The shielding strategy has been used in the development of NIR-II probes to improve their QYs. So far, this strategy has only been used for the symmetric NIR-II probes, especially those based on the benzo[1,2-c:4,5-c']bis([1,2,5]thiadiazole) (BBTD) skeleton. This work reports the synthesis of a series of asymmetric NIR-II probes based on shielding strategies accompanied by simple synthetic routes, high synthetic yields (above 90%), high QYs, and large Stoke shifts. Furthermore, the use of d-α-tocopheryl polyethylene glycol succinate (TPGS) as a surfactant for an NIR-II fluorescence probe (NT-4) improved its water solubility. In vivo studies showed that TPGS-NT-4 NPs with a high QY (3.46%) achieve high-resolution angiography and efficient local photothermal therapy, while displaying good biocompatibility. Hence, we combined angiography and local photothermal therapy to improve the tumor uptake of nanophotothermal agents while reducing their damage to normal tissues.

Cationic structure of premixed near-stoichiometric CH4/O2/Ar flames at atmospheric pressure: New insights from mass spectrometry, quantum chemistry, and kinetic modeling

The spatial distributions of naturally occurring cations in near-stoichiometric (equivalence ratios ϕ = 0.8 and 1.2) burner-stabilized methane/oxygen/argon flames at atmospheric pressure are studied by molecular beam mass spectrometry (MBMS) and kinetic modeling. The disturbing effect of a nickel sampling cone used in the measurements on the flame was comprehensively modeled using a two-dimensional direct numerical simulation of reacting flow near the axially symmetric probe along with a reduced chemical kinetic mechanism. The use of one-dimensional numerical simulation for predicting the flame structure perturbed by the metallic probe was firmly justified. We also proposed and applied a procedure to correct the measured spatial profiles of cations on the contribution of signals from the hydrates formed slightly upstream the reaction zone due to the sampling probe effects. With all these methodological advantages, we validated the ion chemistry mechanisms proposed earlier in the literature against the novel experimental data on the spatial distributions of the following cations: HCO+, CH3+, H3O+, C2H3O+, CH5O+, C3H3+. The kinetic mechanism published recently by Chen et al. [Combust. Flame 202 (2019) 208] for the charged species formed in methane flames was revised in order to improve its predictive ability. To this end, the highly accurate W2-F12 quantum chemical calculations were used to obtain the reliable formation enthalpies of all cations considered in the mechanism. In the case of C2H3O+ and C3H3+ cations, the calculated values turned out to be profoundly lower than those reported before. Apart from this, the theory also predicted another exit channel for H3O+ + acetylene reaction yielding HCO+ + CH4 instead of C2H3O+ + H2 proposed earlier. The corrections significantly improved the predictive ability of the ion chemistry mechanism. We also considered the most important directions for the further refinement of the mechanism.

Robust Quantum Metrology With Explicit Symmetric States

Quantum metrology is a promising practical use case for quantum technologies, where physical quantities can be measured with unprecedented precision. In lieu of quantum error correction procedures, near term quantum devices are expected to be noisy, and we have to make do with noisy probe states. We prove that, for a set of carefully chosen symmetric probe states that lie within certain quantum error correction codes, quantum metrology exhibits an advantage over classical metrology even after the probe states are corrupted by a constant number of erasure and dephasing errors. These probe states prove useful for robust metrology not only in the NISQ regime, but also in the asymptotic setting where they achieve Heisenberg scaling. This brings us closer towards making robust quantum metrology a technological reality.

Design Approach for a Microstrip Yagi Antenna With a Switched Beam Using Resonant TM10 and TM20 Modes

In this paper, a design approach for a microstrip Yagi antenna with a switched beam using resonant TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> modes is proposed. The antenna consists of a driven patch and two parasitic patches. Initially, a driven patch radiator with two symmetric probes is investigated to determine whether TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> or TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode of this patch can be generated by properly exciting the dual feeding ports. The operating bands of the dual modes are reallocated in close proximity to overlap with each other by introducing the shorting pins and narrow slots. Then, two smaller-sized parasitic patches are placed on the right side of the driver to achieve switchable tilted-beam radiation patterns. The results demonstrate that the smaller-sized parasitic patches act as either directors or reflectors when their TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode or TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode is excited, respectively. Therefore, the quasi-end-fire beams can be satisfactorily generated and steered in the E-plane by switching these two radiative modes by feeding probes. Finally, a proposed antenna is designed and measured. The measured results show that the antenna operating in TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> modes can achieve a common band of 3.03-3.19 GHz, and their beams are oriented at the directions of +27° and -42° in E-plane patterns, respectively. Most importantly, no RF switches are introduced in our design, thus significantly reducing the complexity and cost of the proposed antenna.

Electrostatic Friction Force on an AFM Probe Moving Near a Sample Surface

Within the framework of nonrelativistic electrodynamics, general formulas have been obtained for the tangential dissipative force of electrostatic friction and the normal force of attraction to the surface of an axially symmetric probe moving parallel to the smooth surface of homogeneous materials or coated with thin films substrates with various combinations of materials. As a numerical example, the interaction of a metal ball moving above a metal surface has been studied. The results of the calculations are compared with the available experimental and theoretical results of other authors.

Broadband Pattern Diversity Patch Antenna With Switchable Feeding Network

A single-feed wideband pattern diversity antenna is presented in this paper. The pattern reconfigurability is realized by a p-i-n-diodes-intergrated switchable feeding network with the ability of providing 0° in-phase or 180° out-of-phase antenna excitation. The radiating patch is excited by the feeding network through a pair of symmetric stepped probes. When the two stepped probes are with in-phase excitation, a conical mode can be generated on the patch. On the other hand, the antenna can operate at a broadside mode if the excitation is out-of-phase. A meticulous prototype is developed, manufactured, and measured. The measured impedance bandwidths of the 10-dB return loss are 60.7% from 1.95 to 3.65 GHz for the broadside mode and 72.7% from 1.65 to 3.65 GHz for the conical mode. Meanwhile, measured peak gains of up to 10.2 and 7.7 dBi and measured radiation efficiencies of higher than 80% and 76% are obtained for the broadside mode and conical mode, respectively.

Fast and Selective Two-Stage Ratiometric Fluorescent Probes for Imaging of Glutathione in Living Cells.

Two fluorescent, m-nitrophenol-substituted difluoroboron dipyrromethene dyes have been designed by nucleophilic substitution reaction of 3,5-dichloro-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY). Nonsymmetric and symmetric probes, that is. BODIPY 1 (with one nitrophenol group at the position 3) and BODIPY 2 (with two nitrophenol groups at the positions 3 and 5) were applied to ratiometric fluorescent glutathione detection. The detection is based on the two-step nucleophilic aromatic substitution of the nitrophenol groups of the probes by glutathione in buffer solution containing CTAB. In the first stage, probe 1 showed ratiometric fluorescent color change from green (λem = 530 nm) to yellow (λem = 561 nm) because of monosubstitution with glutathione (I561nm/I530nm). Addition of excess glutathione caused the second stage of ratiometric fluorescent color change from yellow to reddish orange (λem = 596 nm, I596nm/I561nm) due to disubstitution with glutathione. Therefore, different concentration ranges of glutathione (from less to excess) could be rapidly detected by the two-stage ratiometric fluorescent probe 1 in 5 min. While, probe 2 shows single-stage ratiometric fluorescent detection to GSH (from green to reddish orange, I596nm/I535nm). Probes 1 and 2 exhibit excellent properties with sensitive, specific colorimetric response and ratiometric fluorescent response to glutathione over other sulfur nucleophiles. Application to cellular ratiometric fluorescence imaging indicated that the probes were highly responsive to intracellular glutathione.

Symmetric fluorescent probes for the selective recognition of Ag-ion via restricted C N isomerization and on-site visual sensing applications

Naphthalene based salen type fluorescent chemosensors have been designed and synthesized for the highly selective detection of silver ions by fluorimetry. These probes 1, 2 and 3 sense Ag+ over other cations as fluorescence ‘on-off’ behaviour. A possible mechanism is proposed, where the heavy atom effect of silver ion overcomes the effect of CN isomerization and intramolecular restricted torsional rotation through the CC single bond between the naphathalene and the benzene moieties. These chemosensors are further utilized to detect Ag+ as strip tests and solid supported silica gel material. These results are further supported by the theoretical calculations.

Single Patch Antenna With Monopulse Patterns

A dual probe-fed single microstrip patch antenna for the monopulse tracking applications is proposed. The monopulse antenna, consisting of a slot-embedded patch, two symmetric probe feeds and a 180° directional coupler is fabricated in a normal PCB process with a size of only $0.63\lambda \times 0.69\lambda $ . The sum or difference patterns are achieved with out-of-phase or in-phase feeding mechanism. A prototype shows that the measured −10-dB impedance bandwidth is 345MHz (2.11GHz-2.455GHz), and the measured port-isolation is higher than 15dB at the frequency band 2.12GHz-2.50GHz. The measured sum gain and difference null at boresight are 7.54dBi and −32.7dBi, respectively.

Parafermionic phases with symmetry breaking and topological order

Parafermions are the simplest generalizations of Majorana fermions that realize topological order. We propose a less restrictive notion of topological order in 1D open chains, which generalizes the seminal work by Fendley [J. Stat. Mech., P11020 (2012)]. The first essential property is that the groundstates are mutually indistinguishable by local, symmetric probes, and the second is a generalized notion of zero edge modes which cyclically permute the groundstates. These two properties are shown to be topologically robust, and applicable to a wider family of topologically-ordered Hamiltonians than has been previously considered. An an application of these edge modes, we formulate a new notion of twisted boundary conditions on a closed chain, which guarantees that the closed-chain groundstate is topological, i.e., it originates from the topological manifold of degenerate states on the open chain. Finally, we generalize these ideas to describe symmetry-breaking phases with a parafermionic order parameter. These exotic phases are condensates of parafermion multiplets, which generalizes Cooper pairing in superconductors. The stability of these condensates are investigated on both open and closed chains.

Shock-Sensitivity in Shell-Like Structures: With Simulations of Spherical Shell Buckling

Under increasing compression, an unbuckled shell is in a metastable state which becomes increasingly precarious as the buckling load is approached. So to induce premature buckling, a lateral disturbance will have to overcome a decreasing energy barrier which reaches zero at buckling. Two archetypal problems that exhibit a severe form of this behavior are the axially-compressed cylindrical shell and the externally pressurized spherical shell. Focusing on the cylinder, a nondestructive technique was recently proposed to estimate the “shock-sensitivity” of a laboratory specimen using a lateral probe to measure the nonlinear load-deflection characteristic. If a symmetry-breaking bifurcation is encountered on the path, computer simulations showed how this can be suppressed by a controlled secondary probe. Here, we extend our understanding by assessing in general terms how a single control can capture remote saddle solutions: in particular, how a symmetric probe could locate an asymmetric solution. Then, more specifically, we analyze the spherical shell with point and ring probes, to test the procedure under challenging conditions to assess its range of applicability. Rather than a bifurcation, the spherical shell offers the challenge of a destabilizing fold (limit point) under the rigid control of the probe.

A 10–100-GHz Double-Ridged Horn Antenna and Coax Launcher

The design, fabrication, and measurement of a coax to double-ridged waveguide launcher and horn antenna is presented. The novel launcher design employs two symmetric field probes across the ridge gap to minimize spreading inductance in the transition, and achieves better than 15 dB return loss over a 10:1 bandwidth. The aperture-matched horn uses a half-cosine transition into a linear taper for the outer waveguide dimensions and ridge width, and a power-law scaled gap to realize monotonically varying cutoff frequencies, thus avoiding the appearance of trapped mode resonances. It achieves a nearly constant beamwidth in both E- and H-planes for an overall directivity of about 16.5 dB from 10–100 GHz.

Development of Simple Designs of Multitip Probe Diagnostic Systems for RF Plasma Characterization

Multitip probes are very useful diagnostics for analyzing and controlling the physical phenomena occurring in low temperature discharge plasmas. However, DC biased probes often fail to perform well in processing plasmas. The objective of the work was to deduce simple designs of DC biased multitip probes for parametric study of radio frequency plasmas. For this purpose, symmetric double probe, asymmetric double probe, and symmetric triple probe diagnostic systems and their driving circuits were designed and tested in an inductively coupled plasma (ICP) generated by a 13.56 MHz radio frequency (RF) source. Using I-V characteristics of these probes, electron temperature, electron number density, and ion saturation current was measured as a function of input power and filling gas pressure. An increasing trend was noticed in electron temperature and electron number density for increasing input RF power whilst a decreasing trend was evident in these parameters when measured against filling gas pressure. In addition, the electron energy probability function (EEPF) was also studied by using an asymmetric double probe. These studies confirmed the non-Maxwellian nature of the EEPF and the presence of two groups of the energetic electrons at low filling gas pressures.

Time-resolved measurement of plasma parameters by means of triple probe

Triple Langmuir probe (TLP) diagnostic system with its necessary driving circuit is developed and successfully applies for time-resolved measurement of plasma parameters in the negative glow region of pulsating-dc discharge. This technique allows the instantaneous measurement of electron temperature [T_], electron number density [n_] as well as plasma fluctuations without any voltage or frequency sweep. In TLP configuration two probes are differentially biased and serve as a floating symmetric double probe whereas the third probe is simply floating into plasma to measure floating potential as a function of time and thus incorporates the effect of plasma fluctuations. As an example of the application to time-dependent plasmas, basic plasma parameters such as floating potential, electron temperature, and electron number density in low pressure air discharge are determined as a function of time for different fill pressure. The results demonstrate temporal evolution of plasma parameters and thus plasma generation progression for different fill pressures.

Active plasma resonance spectroscopy: a functional analytic description

The term ‘active plasma resonance spectroscopy’ denotes a class of diagnostic methods which employ the ability of plasmas to resonate on or near the plasma frequency. The basic idea dates back to the early days of discharge physics: a signal in the GHz range is coupled to the plasma via an electrical probe; the spectral response is recorded, and then evaluated with a mathematical model to obtain information on the electron density and other plasma parameters. In recent years, the concept has found renewed interest as a basis of industry compatible plasma diagnostics. This paper analyzes the diagnostic technique in terms of a general description based on functional analytic (or Hilbert Space) methods which hold for arbitrary probe geometries. It is shown that the response function of the plasma–probe system can be expressed as a matrix element of the resolvent of an appropriately defined dynamical operator. A specialization of the formalism to a symmetric probe design is given, as well as an interpretation in terms of a lumped circuit model consisting of series resonance circuits. We present ideas for an optimized probe design based on geometric and electrical symmetry.

SYMMETRIC AND ASYMMETRIC DOUBLE LANGMUIR PROBES CHARACTERIZATION OF RADIO FREQUENCY INDUCTIVLEY COUPLED NITROGEN PLASMA

The symmetric and asymmetric double Langmuir probe systems with their necessary driving circuits are developed for characterization of low pressure inductively coupled nitrogen plasma, generated and sustained with 13.56 MHz RF source and an automatic impedance matching network. First of all, the plasma parameters such as ion saturation current, electron temperature and electron number density are determined with symmetric double probe system at different input RF powers, filling gas pressures and radial distance Received 4 March 2011, Accepted 28 March 2011, Scheduled 30 March 2011 Corresponding author: Muhammad Yasin Naz (yasin603@yahoo.com).

Measurement of Adhesion Force by a Symmetric AFM Probe for Nano-imprint Lithography Application

In the nano-imprint lithography process, an important prerequisite for reproducibility is suitable adhesion properties of adhesion promoters to substrate or anti-sticking layer to the stamp. In this study, a rhombus-shaped symmetrical probe with a pillar tip was developed and fabricated using the micro-electro mechanical system (MEMS) fabrication technique and the focused ion beam (FIB) process. For the experimental setup of the adhesion test using a UV-curable resist coated AFM tip with a few surfaces of adhesion promoter, the pillar tip was covered with a UV-curable resist using a micromanipulator. An FOTS anti-sticking layer was applied on the tip by the vapor deposition method. The adhesion force between various adhesion promoters (GPTS, APMDS, APTS and DUV30J) and UV-curable resist, and the adhesion force between the FOTS anti-sticking layer and UV-curable resist were evaluated using the force-distance mode of AFM. It could be shown that the adhesion forces of GPTS and FOTS were about 7497 nN and 449 nN, respectively.