Change In Reflection Coefficient Research Articles

Noncontact characterization of glucose by a waveguide microwave probe

We investigate the electromagnetic field interaction with a glucose aqueous solution using a microwave dielectric waveguide probe to evaluate the glucose concentrations. A microwave dielectric waveguide probe allows observation of the small variation of the glucose concentration changes in the range of 0–300mg/ml by measuring the change of the microwave reflection coefficient. We could observe the effect of concentration change of glucose with a detectable resolution up to 0.5mg/ml at an operating frequency of about f=2.0–2.5GHz. The change of the glucose concentration is directly related to the change of the reflection coefficient due to the electromagnetic interaction between the dielectric waveguide resonator and the glucose aqueous solution. The operational principal is explained by a plane-wave solution model. A glucose biosensor using a microwave dielectric waveguide probe provides a unique approach for glucose monitoring.

Differing Effects of Cilostazol and Aspirin on Thrombus Formation and Microvascular Permeability

Cilostazol is a unique antiplatelet drug as it has been shown to reduce the recurrence of vascular events without exacerbating a risk of bleeding complication, although mechanisms for such effects are unknown. We examined its effects on changes in formation of platelet thrombus and compared those with aspirin. Microhemorrhage was induced by laser ablation on a rat mesenteric venule to observe a spatiotemporal process of non‐occlusive thrombus formation. Platelet thrombi in both cilostazol‐ and aspirin‐treated rats were examined to choose the doses of reagents resulting in comparable anti‐platelet effects. Surprisingly, cilostazol, but not aspirin, was found to reduce erythrocyte extravasation under these conditions. To test if such an effect is attributed to modulation of endothelial barrier properties, we measured changes in water permeability (Lp) and reflection coefficient to albumin (σ) in single‐perfused venules. Cilostazol significantly abolished a transient increase in Lp and a decrease in σ when vessels were challenged by histamine. Furthermore the reagent attenuated baseline Lp under a control state. These results indicate that cilostazol not only acts on the platelet to reduce the size of developing thrombus, but also acts on endothelium to tighten up the endothelial barrier at least in part by inhibiting the cAMP‐degrading enzyme in the endothelium that differs from aspirin. Supported by MEXT.

Bode and Fano impedance matching

AbstractThe Bode limit on bandwidth enhancement through use of an ideal impedance matching network does not allow changes in antenna reflection coefficient over the bandwidth. An exact correction factor is derived from the Fano limitations, yielding a simple modification to the Bode limit. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 875–877, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23244

Nonspecular effects on reflection from absorbing media at and around Brewster's dip

We show that, for a TM (or p-state) Gaussian beam incident onto an absorbing medium at and around Brewster's dip, the reflected beam always remains Gaussian and undergoes a Goos-Hänchen-like (GH) shift, an angular shift, a focal shift, and a beam-waist modification, provided that the beam is sufficiently collimated that the third-order change of the (logarithmic) reflection coefficient can be ignored in the angular range of beam divergence. For weak absorption, not only are a large negative GH shift and an odd-functioned-like focal shift with greater magnitude found but also the angular shift, though small by itself, is shown to give an even larger lateral net shift at a distance beyond the Rayleigh range.

Effects of Interference and Inelastic Scattering in Aharonov–Bohm Ring with Quantum Dot

Interference effects are studied in an Aharonov–Bohm ring with a quantum dot within a one-dimensional model with effects of phase-breaking scattering. When a dot level crosses the Fermi level, the phase of the reflection coefficient changes over a wide range, inducing a resonance in various regions of the ring. Such reflection effects compete with those of resonant transmission through the dot. The peak asymmetry is determined by a combination of these effects and therefore exhibits a complicated behavior even as a function of the phase coherence length.

Label-Free DNA Detection Using a Near-Field Microwave

A near-field scanning microwave microscope (NSMM) is used to study the physical properties of DNA strands with a specific sequence and image lamda-DNA bundles. After the hybridization process between target and capture sequences, specific DNA binding events leads to microwave reflection coefficient (S11) changes of the NSMM. These changes are caused by a modification of the physical dielectric constant due to sequence specific DNA binding. This study demonstrates significant potential of the NSMM as a nondestructive and noncontact tool to detect DNA strands without a target-probe amplification process and as a valuable technique to understand the physical property of DNA.

Discrimination between phase and amplitude attributes in time-lapse seismic streamer data

Time-lapse seismic experiments aim to obtain information about production-related effects in hydrocarbon reservoirs to increase the recovery percentage. However, nonrepeatability problems such as acquisition differences, overburden effects, and noise are often significantly stronger than the imprint of production changes in time-lapse seismic data sets. Consequently, it is very difficult to appraise the changes in petrophysical reservoir parameters over time. We introduce a 4D monitoring approach based on the spectral ratio method. This method produces two time-lapse attributes: the relative change in reflection coefficient and the traveltime shift at reflecting interfaces. These attributes can be used for appraising production-related changes in the subsurface. The approach corrects for time-invariant nonrepeatability effects in the overburden and source-receiver coupling problems in time-lapse surveys. The validity of the method is limited to structurally simple overburden and reservoirs with weak lateral variations. First, we validate the methodology using a synthetic time-lapse seismic experiment. Next, we apply the method to a real time-lapse data set from the Troll West gas province in the North Sea. In the real example, we could not detect movement in the fluid contact of [Formula: see text]. The expected change in amplitude is less than 10%, which is probably below the background noise level for this data set.

Anomalous Reflection of a Longitudinal Ultrasonic Wave from a Strongly Dissipative Medium

Normal reflection of a longitudinal acoustic wave from the plane interface between a solid acoustic line and a strongly dissipative medium (an epoxide resin compound in the process of solidification) has been experimentally investigated. A 14‐fold change in the reflection coefficient of pulsed signals and a decrease in their duration have been detected and the point of phase transmission has been reliably determined by the minimum of the reflection coefficient. The coefficient of reflection of continuous acoustic waves with frequencies of 1–10 MHz from the interface between a plexiglas (or aluminum) and an epoxide resin compound in the process of solidification has been measured. The influence of the amplitude‐frequency characteristic of an ultrasonic piezoelectric transducer on the measurement data obtained has been analyzed. The change in the viscosity coefficient of an epoxide resin compound in the process of its solidification has been calculated by the spectral transform method with the use of computer programs and experimental data on the reflection coefficient dynamics.

The permeability-reducing effects of prostacyclin and inhibition of Rho kinase do not counteract endotoxin-induced increase in permeability in cat skeletal muscle

cAMP stimulation and Rho kinase inhibition are shown to decrease microvascular permeability during noninflammatory conditions, most likely by decreasing contractility of actomyosin filaments in the endothelial cell, but their effects on permeability during inflammatory conditions are not clarified. The objective of this in vivo study, performed on the autoperfused and denervated calf muscle of the cat, was therefore to evaluate to what extent cAMP stimulation and inhibition of Rho kinase reduce permeability at endotoxemia. Change in osmotic reflection coefficient for albumin was used as a measure of altered protein permeability and change in capillary filtration coefficient (CFC) as a measure of altered fluid permeability. After inducing a significant increase in protein and fluid permeability by infusion of lipopolysaccharide (LPS), we determined to what extent the increased permeability was decreased by the cAMP stimulator prostacyclin [1.0 ng/kg/min intravenously (iv)] or the Rho kinase inhibitor Y-27632 [1.05 μg/ml plasma/h intraarterially (ia)]. These doses are known to decrease permeability under noninflammatory conditions. The reflection coefficient for albumin and CFC were determined before and during LPS, and during LPS plus prostacyclin ( n = 6) or LPS plus Y-27632 ( n = 6). The reflection coefficient was reduced by about 30% ( P < 0.05) and CFC was increased by about 25% ( P < 0.05) by LPS, and these permeability parameters were not affected by prostacyclin or Y-27632. We conclude that cAMP stimulation and Rho kinase inhibition reduce permeability by other pathways and mechanisms than those by which permeability is increased during endotoxemia.

Cure monitoring using ultrasonic guided waves in wires

The possibility of using ultrasonic guided waves for monitoring the cure process of epoxy resins is investigated. The two techniques presented use a wire waveguide which is partly embedded in the resin. The first technique is based on the measurement of attenuation due to leakage of bulk waves into the resin surrounding the waveguide. The second technique measures the reflection of the guided wave that occurs at the point where the waveguide enters the resin. Both the attenuation and the reflection coefficient change significantly during cure, and the numerical methods to relate these to the material properties of the curing resin are presented in this paper. The results from the modeling are experimentally verified and show good agreement. The applicability of each testing method is discussed, and typical cure-monitoring curves are presented.

Magnetorefractive effect in magnetic nanocomposites

The magnetorefractive effect in ferromagnetic metal-insulator granular nanostructures (CoFeZr)-SiOn, Co-Al-O, FeSiOn, and (CoFe)-(Mg-F) is investigated in the infrared spectral region in a wavelength range from 5 to 20 μm. The magnitude of the effect varies from 0.1 to 1.5% for different nanocomposites and strongly depends on the frequency of light and magnetoresistance. It is shown that the reflection coefficient changes in a magnetic field not only due to the magnetorefractive effect, but also due to the even magnetooptical effect. Simple relations describing this effect are given for the case when the reflection from the substrate is insignificant and in the case of a three-layer (insulator-film-substrate) system. The expression for the frequency dependence of the magnetorefractive effect in nanocomposites is derived and its features in the case of high-frequency spin-dependent tunneling are analyzed.

Label-free biosensor using an optical waveguide with induced Bragg grating of variable strength

A new design of a highly sensitive optical biosensor is described. It consists of a planar waveguide with a corrugated surface, tuned to be a resonant Bragg reflector. Only the heights of the corrugation are covered by an opto-chemical transducer layer that selectively adsorbs target biomolecules. Upon adsorption, the corrugation depth rises and reflection coefficient changes. This is used to monitor surface reactions. Theoretical analysis and mathematical modeling proves that the device sensitivity compares favorably with current known designs. The proposed biosensor is shown to possess a unique capability of unambiguous discrimination between surface reactions and refraction index changes in the bulk solution.

Ultrasonic Monitoring of Nozzle and Cavity during Injection Moulding

Ultrasonic techniques are recognised as powerful sources of process information. Transducers are applied directly, are non-invasive, yet interrogate the entire melt cross-section, while data are available real-time. During injection moulding, two zones are considered: nozzle and cavity. In the nozzle, ultrasonic velocity measurement provides temperature and pressure information. Mean temperatures not observed by other techniques are detected. Previous extrusion based experience is used to address issues of high temperature transducer operation. In the cavity, changes in reflection coefficient and ultrasonic velocity provide information on mould filling and part cooling. Various mould geometries are monitored using a number of ultrasonic transducers.

Transfer Relations for Electromagnetic Wave Scattering From Periodic Dielectric One-Dimensional Interface: Te Polarization

Some general statements for theory of wave multiple scattering in a three-dimensional inhomogeneous layered dielectric medium are established using the composition rule of the scattering (T-matrix) operators to show that the problem of wave scattering from dielectric interface may be studied similar to the problem of volume wave scattering. The medium is thought as being a stack of n layers, each of them is confined by perpendicular to the z axis planes and consists of a three-dimensional discrete or continuous inhomogeneous medium. The layers do not intersect between them and are embedded into a homogeneous background. A result of the paper is a mixed system of exact operator equations (transfer relations) for the operator wave reflection and transmission coefficients of the medium and the operator wave amplitudes of waves in splits between layers. It is shown that the transfer relations lead to a separate recurrent system of operator equations, which describe the incremental change of the operator wave reflection and transmission coefficients of stack of n - 1 layers upon attachment of a n's layer to the stack. We derive from this recurrent equations a generalized Riccati equation for the operator wave reflection coefficient of the medium and an corresponding equation for the operator wave transmission coefficient of the medium, the coefficients of the Riccati equation and the corresponding equation being expressed in terms of the operator wave reflection and transmission coefficients of a thin slice of the medium and embedding parameter being taken along the z axis. The derived Riccati equation is applied to the problem of electromagnetic wave reflection from a periodic one-dimensional interface of two dielectric half-spaces, the interface being varied in the x axis direction and the wave electric field vector being parallel to the y axis. A solution to the Riccati equation for this problem is found numerically, taking into account with the aid of the Bloch (Floquet) theorem both the propagating and evanescent waves and not invoking the Rayleigh hypothesis. A resonant effect related to the Wood anomalies is discussed.

Antenna radiation pattern measurement using a near-field wire scattering technique

A method of measurement of antenna radiation patterns is described. The variations in reflection coefficient at the antenna feed were recorded as a thin wire is moved past the antenna aperture. It is shown that for antennas whose aperture distributions are separable, the change in reflection coefficient is approximately proportional to the square of the integrated aperture field at the position of the wire. By taking the square root of the change in reflection coefficient due to the signal scattered from the wire, as a function of wire position, the integrated aperture field can be obtained, and hence one cut of the far-field radiation pattern. An experimental system has been constructed, and comparisons are presented of radiation patterns measured using the scanning wire technique with those of the same antennas measured on a far-field range, demonstrating good agreement. The technique should provide a rapid and simple method of checking antenna performance.

Unilateral smoke inhalation in sheep: effect on left lung lymph flow with right lung injury.

We previously reported that smoke inhalation to the right lung will result in damage to the air-insufflated left lung. In this study we confirm these findings and determine whether this injury is associated with an elevation in lung lymph flow and pulmonary microvascular permeability to protein as indexed by changes in reflection coefficient. Sheep (n = 12) were surgically prepared by placement of a Swan-Ganz catheter and pneumatic occluders on all pulmonary veins and the left pulmonary artery. The left lung lymphatic was selectively cannulated as shown previously (Y. Kikuchi, H. Nakazawa, and D. Traber. Am. J. Physiol. 269 (Regulatory Integrative Comp. Physiol. 38): R943-R947, 1995). All afferent lymphatics from the right lung were severed, and the right pulmonary ligament was sectioned. The caudal end of the lymph node was sectioned to remove systemic lymph contamination. The sheep were studied in the unanesthetized state 7 days later. To ensure that lymph flow was exclusively from the left lung (QLL), right pulmonary microvascular pressure was increased, a procedure that resulted in little or no change in QLL, as was previously shown. The sheep were then anesthetized, and a Carlens tube was positioned to allow separate ventilation of the right and left lung. The right lungs of five sheep and the left lungs of two sheep were insufflated with cotton smoke. Insufflation of the left lung with cotton smoke produced a fourfold increase in QLL that began 4 h after insult. Insufflation of the right lung with smoke led to a doubling of QLL that began 12 h after insult. Changes in QLL were associated with increased microvascular permeability, as indexed by the reflection coefficient. Control sheep (air insufflated into both lungs, n = 5) showed no change in QLL. Injury to the right lung resulted in damage to the left air-insufflated lung, suggesting a hematogenous mediation of the response.

Ion-induced alkali-silicon interfaces: Atomistic simulations of collisional effects

The bombardment of Si with Cs is investigated by computer simulation with the program TRIDYN. The dynamic target changes due to the bombardment as composition profiles and the corresponding changes in sputtering yield and reflection coefficient are studied as functions of incident conditions. The incident energy is varied from 0.1 to 100 keV, and for 4 and 40 keV the dependence on the incident angle is considered. The dynamic results are compared with data from static calculations (low fluence). The influence of interaction potentials and of the choice of three surface binding energy models on the results are discussed.

Changes in vegetation reflection coefficient caused by changes in geochemistry — first results

This paper provides a theoretical overview and empirical demonstration of Partial Least Squares Path Modeling (PLS) comparing it to Structural Equation Modeling (SEM). The two data analysis techniques share historical origins but differ in terms of underlying algorithms, which gives rise to other key differences: (a) the treatment of unexplained indicator variance; (b) the specification of formative constructs; (c) the availability of model fit estimates; and (d) sample size requirements. We conduct secondary analyses of an existing data set from MacCann, Fogarty, and Roberts (2012) as an empirical demonstration of the utility of PLS in psychology research. The first analysis shows PLS will produce results similar to those of SEM for a simple mediation model. The second analysis shows that PLS can produce results for a complex model for which SEM would require a prohibitively large sample. We conclude that: (1) under common constraints of differential psychology research settings, sample size requirements of PLS may be substantially smaller than those of SEM; (2) PLS is a useful tool for differential psychology research in scenarios where sample size constrains the use of robust SEM; and (3) that PLS offers a viable means to explore and text complex models beyond current limits.

Monitoring soil contaminations using a contactless conductivity probe1

AbstractIn order to investigate the possibility of using low‐frequency electromagnetic waves to detect and monitor oil contamination of soils, a series of laboratory measurements were performed. A new measurement system to monitor the resistivities of soil and sand samples while samples are being contaminated by diesel oil is presented. The frequency used in measurements is 100 kHz. Since the measurement system is composed of coil‐type transmitters and receivers, there is no need for electrodes to be in contact with samples. The contamination process is simulated using diesel oil dripping on top of soil and sand samples. The conductivity distributions in samples along the sample length are recorded as a function of time. Water‐wet sand and soil samples were measured during diesel oil contamination. The measured data show that the conductivities of soil and sand samples change during the contamination process. The change in resistivity for measured samples before and after diesel oil contamination is in the range of 20% to 50%, giving a reflection coefficient change in the low‐frequency limit of 4.7% to 7%. This amount of change in the reflection coefficient makes it very challenging to detect and monitor oil contamination based on EM reflection from the contaminants. The results suggest that EM methods based on propagation and induction, such as tomography and borehole induction, could be used for this purpose.

Microwave compressive strength estimation of cement paste using monopole probes

Abstract In-situ evaluation of the compressive strength of existing concrete structures using a direct approach is the objective of this investigation. The principle factor affecting the compressive strength of a concrete structure is its water/cement (w/c) ratio. The reflection properties of four cement paste samples with w/c ratios of 0.35, 0.40, 0.50, and 0.55 were measured using several monopole probes at microwave frequencies of 5, 9, and 12 GHz. The effect of several parameters, such as the operating frequency, the probe length (h), and the properties of the cement paste (w/c ratio) on the measurement sensitivity, were studied theoretically as well. For a given monopole probe (fixed diameter), h and the operating frequency can be optimized such that any slight change in the w/c ratio causes a large change in the reflection coefficient. Lower microwave frequencies are shown to be more sensitive in detecting variation in the reflection coefficient of these samples as a function of the w/c ratio. After...