A label-free DNA aptamer-based impedance biosensor for the detection of E. coli outer membrane proteins

A label-free DNA aptamer-based impedance biosensor for the detection of E. coli outer membrane proteins (OMPs) was developed. Two single stranded DNA sequences were tested as recognition elements and compared. The aptamer capture probes were immobilized, with and without 6-mercapto-1-hexanol (MCH) on a gold electrode. Each step of the modification process was characterized by Faradaic impedance spectroscopy (FIS). A linear relationship between the electron-transfer resistance (Ret) and E. coli OMPs concentration was demonstrated in a dynamic detection range of 1 × 10−7–2 × 10−6 M. Moreover, the aptasensor showed selectivity despite the presence of other possible water contaminates and could be regenerated under low pH condition. The developed biosensor shows great potential to be incorporated in a biochip and used for in situ detection of E. coli OMPs in water samples.

Excitation of low-profile equilateral-triangular dielectric resonator antenna using a conducting conformal strip

A new configuration that employs a conducting conformal strip to excite the low-profile equilaterial-triangular dielectric resonator antenna (DRA) of very high permittivity is proposed. As compared with the previous aperture-coupling configuration, the new configuration has a wider impedance bandwidth (- 5.5%) and a higher front-to-back radiation ratio. The return loss, radiation patterns, and antenna gain are measured and discussed

Investigations on the Multiferroic and Thermoelectric properties of Low and Intermediate band width Manganites

This thesis lays importance in the investigation on the multiferroic and thermooelectric properties of selected representatives of low bandwidth and intermediate band width manganites. The first candidate, Strontium doped Gd manganite, is prepared by wet solid state reaction method and the second candidate, Na doped La manganite, by citrate gel method. In addition to the above mentioned properties, magneto resistance and dielectric properties are investigated. Using dielectric spectroscopic the dispersion parameters are correlated to the relaxation mechanisms and an attempt is made to obtain the grain and grain boundary contribution to the impedance of the sample through impedance spectroscopy studies.

Reactive loaded microstrip leaky wave antenna for low cost beam steering applications

A novel fixed frequency beam scanning microstrip leaky wave antenna is reported. The beam scanning at fixed frequency is achieved by reactive loading. Simulation and measured results shows frequency scanability of 80° as well as fixed frequency beam steering of 68° over the −10 dB impedance band of 4.56–5.06 GHz.

Ocean acoustic models for low frequency propagation in 2D and 3D environments

In this paper we are mainly concerned with the development of efficient computer models capable of accurately predicting the propagation of low-to-middle frequency sound in the sea, in axially symmetric (2D) and in fully 3D environments. The major physical features of the problem, i.e. a variable bottom topography, elastic properties of the subbottom structure, volume attenuation and other range inhomogeneities are efficiently treated. The computer models presented are based on normal mode solutions of the Helmholtz equation on the one hand, and on various types of numerical schemes for parabolic approximations of the Helmholtz equation on the other. A new coupled mode code is introduced to model sound propagation in range-dependent ocean environments with variable bottom topography, where the effects of an elastic bottom, of volume attenuation, surface and bottom roughness are taken into account. New computer models based on finite difference and finite element techniques for the numerical solution of parabolic approximations are also presented. They include an efficient modeling of the bottom influence via impedance boundary conditions, they cover wide angle propagation, elastic bottom effects, variable bottom topography and reverberation effects. All the models are validated on several benchmark problems and versus experimental data. Results thus obtained were compared with analogous results from standard codes in the literature.

On the concept of electrical impedance for an electrolytic cell

The analysis of the electrical impedance of an electrolytic cell in the shape of a slab is performed. We have solved, numerically, the differential equations governing the phenomenon of the redistribution of the ions in the presence of an external electric field, and compared the results with the ones obtained by solving the linear approximation of these equations. The control parameters in our study are the amplitude and the frequency of the applied voltage, assumed a simple harmonic function of the time. We show that for the large amplitudes of the applied voltage, the actual current is no longer harmonic at low frequencies. From this result it follows that the concept of electrical impedance of a cell is a useful quantity only in the case where the linear approximation of the fundamental equations of problem work well.

Design and simulation of a low voltage wide band RF MEMS switch

This paper presents design of an electrostatic wide band shunt capacitive coupling RF MEMS switch with low actuation voltage. The key factors of the RF MEMS switch design are the proper scattering parameters, low actuation voltage, and the cost of the fabrication process. An overview of the recent low actuation voltage RFMEMS switches has been presented. These designs still suffer from the complexity of process, lack of reliability, limitation of frequency band, and process cost. RF characteristics of a shunt RF MEMS switches are specified mostly by coupling capacitor in upstate position of the membrane Cu. This capacitor is in trade-off with actuation voltage. In this work, the capacitor is eliminated by using two short high impedance transmission lines, at the input and output of the switch. The simulation results demonstrate an improvement in the RF characteristic of the switch.

Electrochemical impedance spectroscopy and surface characterization techniques to study carbon dioxide corrosion product scales

Electrochemical impedance spectroscopy (EIS) was used to study carbon dioxide (CO2) corrosion product scales and their effects on further CO2 corrosion. Objectives were to determine the suitability of EIS for studying corrosion scales and to investigate the influence of environmental factors on scale formation. EIS provided useful information about protective abilities and electrochemical properties of corrosion scales. CO2 corrosion scales formed at high-temperature and pressure provided better protection than those formed at low-temperature and pressure. The level of protection of the scale formed at higher temperature and pressure increased with exposure time. EIS results were compared with coupon weight-loss measurements. Scales were analyzed using a combination of Fourier transform infrared (FTIR) analysis, x-ray diffraction (XRD), and electron microscopy.

Effect of aluminum on the corrosion resistance of low-alloy steel in 10wt% sulfuric acid solution

The aqueous corrosion behavior of low-alloy steel with aluminum contents was examined in a 10 wt% H₂SO₄ (pH 0.13) solution using electrochemical techniques and surface analyses. The corrosion resistance of the new alloy steel was evaluated in terms of electrochemical parameters, such as passive current density, film, and charge transfer resistances. The results showed that a high Al content in the steel imparted better passivation behavior resulting in a lower corrosion rate. It related to the enrichment of iron carbonate and hydrocarbon by the dissolution of the carbide phase.

Comparative study of ni effect on the corrosion behavior of low alloy steels in FGD and acid rain environments

The alloying effect of a small amount of nickel on low alloy steel for application to flue gas desulfurization(FGD) systems was studied. The structural characteristics of the rust layer were investigated by scanning electron microscopy(SEM). The electrochemical properties were examined by means of potentiostatic polarization test, potentiodynamic polarization test, and electrochemical impedance spectroscopy(EIS) in a modified green death solution of 16.9 vol.% H2SO4+0.35 vol.% HC1 at 60°C and an acid rain solution of 6.25 X 10-5 M H2S04+5.5 X 10-3 M NaCl at room temperature. It was found that as the amount of nickel increased, the corrosion rate increased in the modified green death solution, which seemed to result from micro-galvanic corrosion between NiS and alloy matrix. In acid rain solution, the corrosion rate decreased as the amount of nickel increased due to the repulsive force of NiFe204 rust against Cl-ions by electronegativity.

Studies of CO2 corrosion product scales using electrochemical impedance spectroscopy and surface characterisation techniques

Electrochemical impedance spectroscopy (EIS) was used to study carbon dioxide (CO2) corrosion product scales and their effects on further CO2 corrosion. Objectives were to determine the suitability of EIS for studying corrosion scales and to investigate the influence of environmental factors on scale formation. EIS provided useful information about protective abilities and electrochemical properties of corrosion scales. CO2 corrosion scales formed at high-temperature and pressure provided better protection than those formed at low-temperature and pressure. The level of protection of the scale formed at higher temperature and pressure increased with exposure time. EIS results were compared with coupon weight-loss measurements. Scales were analyzed using a combination of Fourier transform infrared (FTIR) analysis, x-ray diffraction (XRD), and electron microscopy

Low cost BIST techniques for linear and non-linear analog circuits

With the ever increasing demands for high complexity consumer electronic products, market pressures demand faster product development and lower cost. SoCbased design can provide the required design flexibility and speed by allowing the use of IP cores. However, testing costs in the SoC environment can reach a substantial percent of the total production cost. Analog testing costs may dominate the total test cost, as testing of analog circuits usually require functional verification of the circuit and special testing procedures. For RF analog circuits commonly used in wireless applications, testing is further complicated because of the high frequencies involved. In summary, reducing analog test cost is of major importance in the electronic industry today. BIST techniques for analog circuits, though potentially able to solve the analog test cost problem, have some limitations. Some techniques are circuit dependent, requiring reconfiguration of the circuit being tested, and are generally not usable in RF circuits. In the SoC environment, as processing and memory resources are available, they could be used in the test. However, the overhead for adding additional AD and DA converters may be too costly for most systems, and analog routing of signals may not be feasible and may introduce signal distortion. In this work a simple and low cost digitizer is used instead of an ADC in order to enable analog testing strategies to be implemented in a SoC environment. Thanks to the low analog area overhead of the converter, multiple analog test points can be observed and specific analog test strategies can be enabled. As the digitizer is always connected to the analog test point, it is not necessary to include muxes and switches that would degrade the signal path. For RF analog circuits, this is specially useful, as the circuit impedance is fixed and the influence of the digitizer can be accounted for in the design phase. Thanks to the simplicity of the converter, it is able to reach higher frequencies, and enables the implementation of low cost RF test strategies. The digitizer has been applied successfully in the testing of both low frequency and RF analog circuits. Also, as testing is based on frequency-domain characteristics, nonlinear characteristics like intermodulation products can also be evaluated. Specifically, practical results were obtained for prototyped base band filters and a 100MHz mixer. The application of the converter for noise figure evaluation was also addressed, and experimental results for low frequency amplifiers using conventional opamps were obtained. The proposed method is able to enhance the testability of current mixed-signal designs, being suitable for the SoC environment used in many industrial products nowadays.

Impedance of carrier injection at the metal-organic interface mediated by surface states in electron-only tris(8-hydroxyquinoline) aluminium (Alq(3)) thin layers

Capacitance spectra of thin (< 200 nm) Alq(3) electron-only devices have been measured as a function of bias voltage. Capacitance spectra exhibit a flat response at high frequencies (> 10(3) Hz) and no feature related to the carrier transit time is observed. Toward low frequencies the spectra reach a maximum and develop a negative excess capacitance. Capacitance response along with current-voltage (J-V) characteristics are interpreted in terms of the injection of electrons mediated by surface states at the metal organic interface. A detailed model for the impedance of the injection process is provided that highlights the role of the filling/releasing kinetics of energetically distributed interface states. This approach connects the whole capacitance spectra to the occupancy of interface states, with no additional information about bulk trap levels. Simulations based on the model allow to derive the density of interface states effectively intervening in the carrier injection (similar to 1.5 x 10(12) cm (2)). (C) 2008 Elsevier B.V. All rights reserved.

Real-time multi-sensors measurement system with temperature effects compensation for impedance-based structural health monitoring

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