Resistive Card Research Articles

P682 Antibiotic resistome profiles of fecal Escherichia coli isolates in association with Crohn’s disease

Abstract Background In recent years, there was a growing interest in the modulation and manipulation of the intestinal flora to treat patients through fecal microbiota transplantation (FMT). Unfortunately, 2 cases of bacteremia via FMT in 2019 occurred in patients due to extended-spectrum beta–lactamase–producing E. coli from the same stool donor. However, one of the recipients did not get an active infection. So, the association between health status and bacterial ability to resist chemicals requires further investigations. Methods Totally, 63 E. coli strains from 32 fecal samples (14 CD patients and 18 controls) were whole-genome sequenced on the Miseq platform (project #0671-2020-0058). The strains were tested against 15 antibiotics by a disc-diffusion assay according to EUCAST guidelines. E. coli ATCC 25922 was used as a control. Antibiotic resistance genes were predicted by the Resistance Gene Identifier and CARD database. Results All strains tested were susceptible only to meropenem (Figure 1). The proportion of multidrug-resistant strains in CD patients and controls did not differ significantly. Strains from both groups differed in sensitivity to amikacin and levofloxacin (Fisher’s exact test, p<0.1). Ciprofloxacin, widely used in therapy, was less effective against CD-derived strains (15%) compared to controls (3%). The inefficiency of fluoroquinolones could be due to plasmid-associated genes (qnrS1, qnrB19) and mutations in chromosome genes (gyrA, parC). Several strains carried aminoglycoside transferase genes, but only 1 CD-derived strain was non-sensitive. Susceptibility to tetracyclines did not differ between groups, and almost all strains, growing on the antibiotic, contained efflux pump genes (tetA, tetB, tetD, tetR). About half of the strains from both groups were active against penicillins carrying genes for class A (TEM-1, TEM-150) and D beta-lactamases (OXA-1). TEM-150 was only in control strains. Cephalosporin-resistant strains were in both groups and harbored AmpC type β-lactamases. Almost all strains had multidrug efflux systems (MdtEF-TolC, EmrAB-TolC, EmrKY-TolC, AcrAB-TolC), MdtG and AcrD efflux pumps, and their regulators. Although all strains contained pmrF and pmrC genes, only 1 CD-derived strain was non-sensitive to polymyxin. Figure 1. Antibiotic resistance of E. coli strains (in %, * - p < 0.1) Conclusion Thus, the differences in susceptibility between CD- and control-derived strains were revealed. However, E. coli strains from healthy subjects contained antibiotic resistance genes and demonstrated activity against antibiotics of various categories, which might be crucial and should be taken into account for a safe and effective therapy in the treatment of CD.

Spirograph Planar Monopole Antenna (SPMA) Providing Unidirectional Invariant Radiation Patterns by Employing a Broadband Ground Plane

The spirograph planar monopole antenna (SPMA) is combined with the proposed broadband ground plane to achieve unidirectional radiation patterns with enhanced gain and minimal broadside gain variation. The broadband ground plane is a simple structure that consists of a resistive card and a copper sheet in a fixed position. The measured impedance bandwidth for the unidirectional SPMA, with VSWR <; 2 matching criterion, is 1.14-2.90 GHz (87.1% bandwidth). The antenna has a unidirectional radiation pattern that is mostly invariant over the entire frequency range, a single main lobe, and low cross polarization. The measured broadside gain varies from 2.59 to 6.85 dBi within the impedance bandwidth.

E-pulse discrimination of R-cards in a layered environment

The feasibility of using the E-pulse technique to identify the values of a resistance card (R-card) contained within a material stack is demonstrated. The late-time response of a material stack is modeled as a resonance series and an E pulse is constructed to extinguish this response. Results using measured data show that it is possible to identify the R-card value from among five potential candidates.

A Fast Hybrid Asymptotic and Numerical Physical Optics Analysis of Very Large Scanning Cylindrical Reflectors With Stacked Linear Array Feeds

A novel hybrid combination of an analytical asymptotic high-frequency method with a numerical physical optics (PO) procedure is developed to efficiently and accurately predict the far zone fields of extremely long, scanning, very high gain, offset cylindrical reflectors of arbitrary cross-section, with large stacked finite periodic linear phased array feeds, for spaceborne applications. In this method, the field generated by each finite length linear feed array is represented as a spectral integral and the induced current on the cylindrical reflector surface due to this illumination is obtained via the PO approximation. The reflector surface is divided into thin, long, piecewise planar strips along the generator of the cylindrical reflector, and the radiation integral over each strip is evaluated asymptotically in closed form, yielding an eight-term ray solution for the radiated fields. What remains is simply the superposition of the contributions of each strip and linear array in the feed stack. The proposed approach is shown to be extremely efficient and accurate as compared to the conventional PO integration technique. In addition, the method is sufficiently versatile to account for the reflector edge treatments (e.g., using resistive cards), as well as to account for a twist in the reflector surface due to thermal distortions in space.

Experimental study of the temporal characteristics of a switch for topologically modulated signals

Aspects of an experimental study of the temporal characteristics of switches for topologically modulated signals are considered. A microwave resistive switch card serves as the experimental model. The clock frequency of the generator of topologically modulated pulses developed is chosen such that the ratio of the wavelength at the clock frequency to the dimensions of the standard switch card is equal to 104. It is concluded on the basis of the virtual absence of distortions of the input pulses switched by the device and the application of scaling to the experimental results that a switch of micron dimensions is effective for microsecond pulses, confirming the previously obtained theoretical data.

Resistive treatment to reduce edge diffraction from large wedge‐shaped objects and planar antennas

The application of a tapered resistive card to reduce the EM scattering from the edge of an impedance wedge is presented. The problem is two‐dimensional, where the incident field is polarized transverse magnetic or electric to the axis of the wedge, and the resistive card is infinitesimally thin and is attached to the vertex of the wedge. An integral equation is formulated to solve for the scattering from the structure which utilizes a specialized Green's function for the impedance wedge. The integral equation is then solved using a method of moments technique. Since the presence of the wedge is taken into account by the Green's function, unknowns need to be placed only over the region of the resistive card and not along the boundaries of the wedge, thus reducing the size of the moment method matrix. Numerical optimization techniques are then employed to determine the resistance profiles for the cards which yield designs that minimize the scattered field over broad spatial regions and over broad frequency bands as well. The resulting designs for the resistive cards have therefore been optimized to yield maximum performance for scattering reduction. The application of this work to the reduction of edge diffraction from the edges of the ground plane of a microstrip antenna is also discussed, and measured as well as calculated results are presented.

Mixed-field hybrid FEM/BEM formulation for two-dimensional TE radiation and scattering by resistive strips

A new mixed-field, hybrid finite-element method (FEM) (E-field)/BEM (H-field) formulation is presented for modeling the two-dimensional (2-D) radiation and scattering from scatterers comprised with inhomogeneous materials including resistive cards and perfectly electrically conducting (PEC) strips for the TE polarization. Using the usual H-field formulation leads to the requirement for the use of a special gap element. The E-field formulation will result in a much more cumbersome BEM integral. The new mixed-field formulation retains the simplicity of the scalar formulation and is useful for problems which cannot be treated elegantly with the existing approach. The new formulation has been implemented into a 2-D FEM/BEM computer code. Numerical results obtained compare well to previously published results.

Thin‐film boundary conditions

AbstractA set of boundary conditions for general thin‐film structures is derived, which includes special cases of a resistive card and a thin coating over perfect electric conductors. The use of such boundary conditions in an analytical method, the method of moments, or the finite element method offers three distinct advantages: (i) the boundary conditions are much simpler, which makes the integral equation or the variational equation formulation simpler, (ii) the number of unknowns is reduced, and (iii) the numerical solution is more stable. © 1992 John Wiley &amp; Sons, Inc.

Modeling of resistive sheets in finite element solutions (EM scattering)

A variational formulation is presented for modeling a resistive card in the context of the finite-element method (FEM). To validate this formulation, results based on a physical modeling of the resistive sheet are also presented. In this case, the resistive sheet is equivalently replaced by a thin dielectric layer. The modeling of such a layer in the usual manner leads to larger and consequently inefficient linear systems, which is the primary reason for resorting to a mathematical modeling of the resistive sheet. Results based on the mathematical and physical modeling are presented in connection with the scattering by a metal-backed cavity in a ground plane. These are used to validate the proposed mathematical model. >

A representation theorem based analysis of two-dimensional electromagnetic scattering from materials and resistive cards

Representation-theorem-based surface integral operators are presented and used to predict electromagnetic scattering from a material body with an embedded resistive card. The integral operators are obtained from a representation theorem for the 2-D Helmholtz equation in a region with constant electrical properties characterized by complex permittivity and permeability. A resistive card embedded in the region is introduced by enforcing a resistive boundary condition on the representation theorem integrals as the thickness of a geometrically thin region surrounding an embedded card approaches zero. Surface integral operators are obtained by letting the field point in the representation theorem equations approach material boundaries and resistive cards. Multiple regions with constant electrical properties (including perfect conductors) are allowed by enforcing boundary conditions between regions. Two polarizations of normally incident plane wave radiation are considered. Prediction and experiment are in good agreement for a resistive card embedded in a bulk material. >

A Time-Domain, Finite-Volume Treatment for the Maxwell Equations

ABSTRACT For computation of electromagnetic scattering from layered objects, the differential form of the time-domain Maxwell's equations are first cast in a conservation form and then solved using a finite-volume discretization procedure derived from proven Computational Fluid Dynamics (CFD) methods 1 . The formulation accounts for any variations in the material properties (time, space, and frequency dependent), and can handle thin resistive sheets and lossy coatings by positioning them at finite-volume cell boundaries. The time-domain approach handles both continuous wave (single frequency) and pulse (broadband frequency) incident excitation. Arbitrarily shaped objects are modeled by using a body-fitted coordinate transformation. For treatment of complex internal/external structures with many material layers, a multizone framework with ability to handle any type of zonal boundary conditions (perfectly conducting, flux through, zero flux, periodic, nonreflecting outer boundary, resistive card, and lossy ...

A three-dimensional Maxwell's equation solver for computation of scattering from layered media

The differential time-domain Maxwell's equations are cast in a conservative form and then solved using a finite-volume discretization procedure derived from computational fluid dynamics methods applied to linear/nonlinear gasdynamics equations. The formulation accounts for any variations in the material properties (time, space, and frequency dependence) and can handle thin resistive sheets and lossy coatings by positioning them at finite-volume cell boundaries. The time-domain approach handles both continuous-wave (single-frequency) and pulsed (broadband-frequency) incident excitation. Arbitrarily shaped objects are modeled using a body-fitted coordinate transformation. For treatment of complex internal/external structures with many material layers, a multizone framework with ability to handle any type of zonal boundary conditions (perfectly conducting, flux through, zero flux, periodic, nonreflecting outer boundary, resistive card, lossy coatings, etc.) is implemented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Development of Thin Metal Film Corrosion Indicators

Abstract An account is given of the development of visual and electrical corrosion indicators which utilize thin metal films vacuum-deposited on non-metallic substrates. Data are presented showing the behavior of these indicators in corrosive atmospheres. Although the indicators were developed primarily to detect and mark corrosive conditions in packages and storage areas, other possible applications are described briefly. Data reported include comparative corrosion information on electrical cards and buttons in various humid atmospheres, condition of visual and resistance thin film indicators at first sign of corrosion on hardware items, and behavior of polyvinyl resistance card indicators at different sensitizations at 25 C and 60 percent relative humidity. The paper presents the progress of this development program from the feasibility studies through the final development of manufacturing protypes. 3.23

100:1 Bandwidth Balun Transformer

The theory and design of a Tchebycheff tapered balun transformer which will function over frequency bandwidths as great as 100:1 is presented. The balun is an impedance matching transition from coaxial line to a balanced, two-conductor line. The transition is accomplished by cutting open the outer wall of the coax so that a cross-sectional view shows a sector of the outer conductor removed. As one progresses along the balun from the coaxial end, the open sector varies from zero to almost 2π, yielding the transition to a two-conductor line. The balun impedance is tapered so that the input reflection coefficient follows a Tchebycheff response in the pass band. To synthesize the impedance taper, the impedance of a slotted coaxial line was obtained by means of a variational solution which yielded upper and lower bounds to the exact impedance. Slotted line impedance was determined experimentally by painting the line cross section on resistance card using silver paint and measuring the dc resistance of the section. The measured VSWR of a test balun did not exceed 1.25:1 over a 50:1 bandwidth. Dissipative loss was less than 0.1 db over most of the range. Measurements show that the unbalanced current at the output terminals is negligible.

Theoretical Analysis of the Operation of the Field-Displacement Ferrite Isolator

A theoretical analysis of the resistance-sheet isolator is carried out, and numerical solutions are obtained for the forward and reverse propagation constants of the distorted dominant mode in a rectangular waveguide containing a transversely magnetized thick ferrite slab displaced slightly from the side wall. The microwave electric field patterns within the waveguide are plotted for several values of the physical design parameters of the isolator for which experimental performance data have been reported. Field patterns are used to describe the principles of the isolator and to select the optimum values of slab thickness, internal dc magnetic field, ferrite magnetization, and location of the slab in the waveguide for the idealized isolator. Evidence is presented to show that it is necessary to use a comparatively thick ferrite slab located in a very small usable range of distances from the side wall. The appropriate value of internal dc magnetic field is simply related to the magnetization of the ferrite and to the frequency. It has not been necessary to take into account the perturbing effects of the resistance card or matching techniques in order to explain the basic design principles.

Nonreflecting absorbers for microwave radiation

The absorption of very short electromagnetic waves by absorbing systems, which avoid reflection of the incident wave is a problem of practical interest. Three different methods are applicable: 1. Complete absorption of the incident energy can be obtained for one wavelength by using resonance systems of relatively small thickness; e.g., a resistance card having a surface resistivity equal to the wave impedance of free space and placed a quarter of the wavelength in front of a metal sheet; a dielectric layer of lossy material on a metal sheet, with the thickness of the layer equal to about a quarter of the wavelength in the material; a two-dimensional periodic structure of concentric resonant circuits arranged within the metal sheet itself. 2. The reflecting object can be covered by a thick layer of absorbing material, so that in a wide wavelength range most energy of the incident wave will be absorbed before reaching the reflecting surface. To avoid reflection, the absorption material can be tapered or arranged in different layers in such a manner that the loss tangent steadily increases towards the base plate. 3. The bandwidth of resonance absorbers can be widened without an increase of its thickness by combination of two specially dimensioned resonant circuits.

A sine function resistor

This paper describes a sine function resistor of rather unusual design. A linear resistance card bent to circular shape about an eccentric frame of very simple construction is employed to obtain a resistance variation that is within very close limits of true sine values. This resistor should find application in certain computer circuits, particularly in those of the balanced-bridge type. The same theory is also applied to the function (1 - sin φ)i (i = 1/2, 1).