Complex Gyrator Research Articles

Spectroscopic and computational investigation of the interaction between the new anticancer agent enasidenib and human serum albumin

Enasidenib (EDB) is a new therapeutic agent for the treatment of adult patients with relapsed or refractory acute myeloid leukemia (AML) with an isocitrate dehydrogenase-2 (IDH2) mutation. This research aimed at utilizing experimental and theoretical approaches to characterize the binding mechanism between EDB and human serum albumin (HSA). Formation of an EDB-HSA static complex was demonstrated by quenching of the HSA intrinsic fluorescence by EDB. Using well known mathematical relations (e.g. Stern–Volmer and Lineweaver-Burk equations), the recorded EDB-HSA fluorescence data were interpreted and revealed binding constants in the magnitude order of 104 M−1 for the different investigated temperatures. These determined results were taken into further mathematical calculations to reveal the thermodynamic properties of EDB-HSA binding. Results demonstrated that spontaneous EDB and HSA binding takes place led by electrostatic forces. Computational docking studies have further confirmed the latter finding showing that EDB fits into the HSA Sudlow site I. Molecular dynamic simulation was performed to calculate the root mean square deviation (RMSD), root mean square fluctuation (RMSF), radius of gyration (Rg) and hydrogen bond parameters for the EDB-HSA complex.

Quality Factor of the Waveguide Re-Entrant Turnstile Junction Circulator

One of the two independent variables entering into the description of the one-port complex gyrator circuit of a junction circulator is its quality factor. The other is the susceptance slope parameter. It determines both its gain bandwidth product and the upper frequency bound of this type of junction. The purpose of this paper is to investigate that of the partially recessed waveguide turnstile circulator using a quarter-wave-long re-entrant gyromagnetic resonator. The quality factor of this class of junction is essentially determined by the gyrotropy of the magnetic insulator, except for the penetration of the resonator into the housing of the junction. The other physical parameter of the junction may therefore be utilized to adjust the susceptance slope parameter of the gyrator circuit. The work undertaken here is in WR75 waveguide at a frequency of 13.25 GHz.

Interactions between Activin-Like Kinase 5 (ALK5) receptor and its inhibitors and the construction of a Docking Descriptor-Based QSAR model

In this study, molecular docking and molecular dynamics (MD) simulations were conducted to investigate both the binding site and interactions of 61 inhibitors with activin-like kinase-5 (ALK5) receptor. A MD simulation was performed on the receptor to obtain receptor conformation in a water environment. Docking analysis revealed that hydrophobic and hydrogen bonding interactions play important roles in ALK5-inhibitor complex. These interactions were confirmed by X-ray crystallography. Furthermore, to study receptor conformation stability, a second MD simulation on complex was performed in an aqueous environment. Radius of gyration for complex showed that the ALK5 conformation did not change in the presence of the inhibitor. 134 descriptors emerging from docking and molecular structure were calculated and the most feasible ones were used in quantitative structure -activity relationships (QSAR). The LS-SVR (least squares support vector regression) gave reliable model with Q2 = 0.837 and R = 0.917. Finally, the types of interactions and properties of the descriptors were used to propose new inhibitors.

Semi-experimental characterisation of the 3-port waveguide junction circulator containing a gyromagnetic post resonator

The original 3-port waveguide circulator relies for its operation on a simple gyromagnetic post resonator with top and bottom electric walls and an open magnetic side wall with no variation of the fields along its axis. Its description is a seminal paper in the literature. The purpose of this study is to characterise its first circulation condition (frequency) using a finite-element package and to characterise its second (complex gyrator circuit) experimentally. This is done for one-third-height, half-height and full-height resonator posts. The shortest of these three resonators is compatible with the synthesis of a circulator with an equal ripple degree-2 frequency response with a return loss of 23 dB over a 20 bandwidth. This sort of junction is met in the design of the externally latched junction circulator. This study includes a characterisation of a composite post resonator geometry consisting of an undersized ferrite cylinder surrounded by a dielectric sleeve.

Design of communication circulators using a triplet of U.E.'s at the junction of a circular plate

An attractive gyromagnetic resonator for the design of communication circulators is one for which the shape of the centre conductor between the top and bottom ferrite disks and ground plates incorporates a triplet of short metal strips or U.E.'s at the junction of a circular one. The complex gyrator circuit of one such geometry has recently been experimentally characterised in the literature. The introduction of U.E.'s in the resonator circuit provides a means of decoupling the coupling angle at the terminals of the circular plate from any external networks and a means of adjusting the susceptance slope parameter of the complex gyrator circuit of the junction. The study includes the practical design of one device at 2.0 GHz with a 23 dB return loss over a 30% bandwidth.

Complex gyrator circuit of a three-port circulator using a planar resonator composed of a gyromagnetic disk, a triplet of UEs and a triplet of single radial magnetic walls

A classic planar gyromagnetic resonator, encountered in the construction of three-port circulators, is one with top and bottom electric walls and a magnetic sidewall symmetrically loaded with a triplet of single magnetic walls. The main purpose is to experimentally characterise the complex gyrator circuit of a three-port junction using a resonator made up of a circular region, a triplet of single magnetic walls and a triplet of short 5° long UEs. It is compatible with the design of degree-2 circulators with commercial specifications and one experimental example is included for completeness sake. The effect of the UE embodied in the resonator under consideration is to decouple the coupling angle of the resonator terminals from any external microwave circuits, thereby facilitating the practical design of degree-2 circulators. A similar magnetised resonator loaded with a triplet of triple magnetic walls instead of single ones is also dealt with. It has the effect of reducing the spacing between the first three cut-off numbers of the isotropic geometry.

Split Frequencies and Susceptances of the Three-Port Junction Circulator From an Experimental Determination of the Complex Gyrator Circuit

The adjustment of the classic three-port circulator involves an in-phase eigen-network and a pair of split counter-rotating ones. The purpose of this paper is to use some recent relationships to experimentally extract the split susceptances of the counter-rotating immittances and the susceptance slope parameter of the junction by having recourse to a one-port measurement of its complex gyrator circuit. This is done under the assumption that the in-phase eigen-network of the junction may be idealized by an electric wall. The split frequencies of the counter-rotating eigen-networks of the circulator may also be deduced from this characterization and are in good agreement, under the same assumption, with those derived from one-port measurements on a terminated circulator. The latter arrangement does not, however, allow the split susceptances of the counter-rotating eigen-networks to be deduced.

Substrate-Integrated-Waveguide Circulators Suitable for Millimeter-Wave Integration

Over the years, many millimeter-wave circulator techniques have been presented, such as nonradiative dielectric and fin-line circulators. Although excellent results have been demonstrated in the literature, their proliferation in commercial devices has been hindered by complex assembly cost. This paper presents a study of substrate-integrated millimeter-wave degree-2 circulators. Although the substrate integrated-circuits technique may be applied to virtually any planar transmission medium, the one adopted in this paper is the substrate integrated waveguide (SIW). Two design configurations are possible: a planar one that is suitable for thin substrate materials and a turnstile one for thicker substrate materials. The turnstile circulator is ideal for systems where the conductor losses associated with the thin SIW cannot be tolerated. The design methodology adopted in this paper is to characterize the complex gyrator circuit as a preamble to design. This is done via a commercial finite-element package

Open-circuit parameters of circulators using side-coupled wye resonators: an impedance pole approach

The open-circuit parameters at the terminals of a circular gyromagnetic region to which triplets of coupling ports and stubs are connected may be written in terms of simple linear combinations of the impedance poles of each symmetrical sextet of ports. As the poles of either problem region are available in closed form the construction of the open-circuit parameters poses no difficulty. The arrangement under consideration is met in connection with the description of a junction circulator using a side-coupled wye gyromagnetic resonator. Once the open-circuit parameters are available, the formulation of the complex gyrator circuit of the junction proceeds in terms of standard matrix operations.

Complex gyrator circuit of 4-port single junction circulator

The adjustment of the 4-port single junction circulator involves a degeneracy between a single impedance pole, a pair of split degenerate poles and one impedance zero. The purpose of this paper is to deduce the real part of the complex gyrator circuit of this device under the assumption that the degenerate relationships between the poles and zeros of the arrangement have been met. This determines the gyrotropy of the ideal device and the adjustment of any matching network.

WR75 junction circulator using 90° and 180° ridge UEs

The gain–bandwidth product of a practical junction circulator is fixed by the quality factor of its junction and the topology of its matching circuit. One difficulty with the design of a large mean power circulator or a millimetre one is that its quality factor may not be compatible with the use of 30° and 90° UEs. A method of overcoming these difficulties is to employ a 180° UE at each so-called characteristic plane of the junction. The purpose of the paper is to describe one arrangement in a WR75 waveguide. The device has a return loss of 20 dB and an insertion loss of 0.17 dB over a 16% frequency band. The quality factor of its complex gyrator circuit is 4.0.

Complex gyrator circuit of three-port circulators using gyromagnetic resonators with six-fold symmetry

An important planar resonator for use in the design of commercial three-port circulators consists of a radial gyromagnetic region symmetrically loaded by six uniform or radial transmission lines. One possible model for this sort of junction is, in general, a six-port network with three-fold symmetry with three coupled ports and three short- or open-circuited ones. The development of the open-circuited parameters and the complex gyrator circuit of this arrangement is made particularly simple by taking advantage of the symmetry of the problem region. Its tracking solution is given special attention.

Complex gyrator circuit of a waveguide junction circulator using an Okada resonator

Conventional waveguide junction circulators usually consist of either a single or a pair of coupled quarter-wave long gyromagnetic resonators in a turnstile arrangement, or a planar post one in contact with the top and bottom walls of the junction of three H-plane waveguides. Another geometry that has much to commend it is that obtained by suppressing the axial resonance in the geometry, using either the single or the pair of coupled quarter-wave long resonators. The complex gyrator circuit of a junction circulator using such a weakly magnetised resonator is approximately developed in terms of effective constitutive parameters and is experimentally verified. The construction of a quarter-wave coupled device is separately described. Circulators using such resonators have been tested at 6000 W-CW at S-band, 1500 W-CW at X-band and 400 W-CW at J-band.

Approximate upper and lower bounds on the VSWR of a 3-port circulator with nonideal loads

The upper and lower bounds on the voltage standing wave ratio (VSWR) at port 1 of a 3-port circulator with a complex load under any phase conditions at port 2 and a nonideal termination at port 3 is of some interest in microwave engineering. The purpose of this letter is to give a solution to this problem under some simplifying conditions. The lower bound obtained here is in keeping with the definition of the complex gyrator circuit of this sort of junction when either port 2 or port 3 is terminated in its complex conjugate load.

Complex gyrator circuit of a junction circulator using weakly magnetised planar irregular hexagonal resonator

While the first two circulation conditions of a planar junction circulator using an irregular hexagonal resonator are fairly well established, the description of its network parameters is still wanting. This is remedied by bringing together some new and existing data that are applicable in the weakly magnetised model of this sort of gyromagnetic resonator. This is done by having recourse to some finite-element, contour-integral and closed-form calculations in conjunction with the classic relationship between the gyrator conductance, the susceptance slope parameter and the split frequencies of the gyromagnetic resonator. Experimental data on the susceptance slope parameter and quality factor of this type of problem region are included for completeness.

Synthesis of quarter-wave coupled junction circulators using moderately magnetised disc resonators with commensurate eigennetworks

A classic solution met in the theory of a junction circulator using a disc gyromagnetic resonator is the so-called tracking one for which the complex gyrator circuit displays a nearly frequency-independent gyrator conductance and a nearly constant susceptance-slope parameter over nearly an octave band. It is characterised by a tensor permeability with an offdiagonal element κ, 0.50 ≤ κ ≤ 1.0, a unique coupling angle, an in-phase eigennetwork with an ideal electric wall at the terminals of the junction, and counterrotating ones with split conjugate reactances at the same terminals. Another useful solution is the so-called weakly magnetised one for which the gyrotropy is bracketed by 0 ≤ κ ≤ 0.30 but for which the solution is independent of the coupling angle. The paper investigates the complex gyrator circuit of this sort of circulator in the intermediate gyromagnetic interval defined by 0.30 ≤ κ ≤ 0.50. Each gyromagnetic interval is associated with a unique complex gyrator circuit with a distinct value of gain–bandwidth product or quality factor. A practical example of such a synthesis is included.

Synthesis of octave-band quarter-wave coupled semi-tracking stripline junction circulators

The complex gyrator circuit of stripline circulators using tracking junctions which satisfy the physical and magnetic variables of the Wu and Rosenbaum boundary conditions, is a nearly frequency independent octave-band resistive network. Such a junction may exhibit two minimas in its reflection coefficient when matched by a two section impedance transformer. However, a third minima may be realised by utilizing a complex rather than a real gyrator circuit. This paper summarises this class of semi-tracking solution in a simple way as a preamble to the design of a degree-3 quarter wave coupled circulator. The overall frequency behaviour of this class of junction has been separately evaluated by combining the electromagnetic and network problems (in conjunction with a two step impedance matching network).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Experimental evaluation of junction circulators: a review

The adjustment of any microwave device should always reflect as far as possible its physical properties. The purpose of the paper is to summarise existing experimental techniques for the characterisation of the classic 3-port junction circulator for which the inphase eigennetwork may be approximately represented by an electric wall boundary condition. Some important possibilities include its matrix descriptions, its corresponding eigenvalues and its complex gyrator circuit. New experimental techniques for the evaluation of the immittances and frequencies of the split eigennetworks are separately described.

Synthesis of series STUB-R complex gyrator circuits using halfwave long impedance transformers

The complex shunt STUB-G circuits met in the practice of three-port circulators may be matched using one eight-wave long alternate lines or quarter wave long impedance transformers. Another possibility is to employ halfwave long UEs at the characteristic planes of the junction where the complex gyrator circuit is a series STUB-R network. Although this topology is not particularly compact the impedance levels met in this solution are appropriate for the matching of junction circulators with high Q complex gyrator loads. This paper gives the synthesis of this problem in the case of a single halfwave long UE.

Technical Memorandum: Complex gyrator circuit of junction circulators using weakly magnetised ring resonators

Planar junction circulators using weakly magnetised disc, wye, triangular and hexagonal resonators have by now been described in the literature. Another resonator that has the symmetry of the 3-port junction circulator is the ring resonator. Since the degenerate and split frequencies in this type of gyromagnetic resonator have already been established in the literature, an understanding of its complex gyrator circuit requires only a definition of its susceptance slope parameter. The purpose of this effort is to tackle this problem.