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We present a collocated pair of antennas, operating from 700 to 2700 MHz. The antenna structure consists of two wideband dipole elements placed at height 0.093 λlow above a 0.47 λlow × 0.54 λlow ground plane. The dipoles achieve an isolation of about 40 dB using orthogonal polarization arrangement with resistive sheets (R-card) placed between the antenna pair. The configuration is suitable for sidewall mounting and is easy to fabricate with integrated baluns on a single two-sided printed circuit board (PCB). This antenna pair should be useful for multiple-input-multiple-output (MIMO) systems and simultaneous transmit/receive applications in several common wireless communication bands. [ABSTRACT FROM AUTHOR]

This paper addresses the difficulties of achieving lower cross-polarization EM field transmission (or reception) levels by employing wideband electromagnetic-polarization filters (EMPFs). These electromagnetic-polarization filters are applied as add-on screens to reduce the cross-polarization levels of standard-gain horns (SGHs) and diagonal horns (DH). Cross-polarization level reductions as much as 19 dB are presented for diagonal horns with add-on screens. Similarly, more than 9 dB cross-polarization reductions are shown for standard-gain horns across the operational bandwidth. An alteration was made to the add-on screens by making use of Ludwig's third coordinate definition. This modification resulted in further cross-polarization suppression in the vicinity of the boresight direction. For instance, for an X-band standard-gain horn, near the boresight angular region where the cross-polarization level was kept below −60 dB, this increased by 26% with the use of this modified add-on screen. [ABSTRACT FROM AUTHOR]

Dilute ethanol (EtOH) is a widely used agent to remove the corneal epithelium during the modern refractive surgery. The application of EtOH may cause the underlying corneal fibroblasts to undergo apoptosis. This study was designed to investigate the protective effect and potential mechanism of the respiratory chain coenzyme Q10 (CoQ10), an electron transporter of the mitochondrial respiratory chain and a ubiquitous free radical scavenger, against EtOH-induced apoptosis of corneal fibroblasts. Corneal fibroblasts were pretreated with CoQ10 (10 mM) for 2 h, followed by exposure to different concentrations of EtOH (0.4, 2, 4, and 20%) for 20 s. After indicated incubation period (2-12 h), MTT assay was used to examine cell viability. Treated cells were further assessed by flow cytometry to identify apoptosis. Reactive oxygen species (ROS) and the change in mitochondrial membrane potential were assessed using dichlorodihydrofluorescein diacetate /29,79-dichlorofluorescein (DCFH-DA/DCF) assays and flow-cytometric analysis of JC-1 staining, respectively. The activity and expression of caspases 2, 3, 8, and 9 were evaluated with a colorimetric assay and western blot analysis. We found that EtOH treatment significantly decreased the viability of corneal fibroblasts characterized by a higher percentage of apoptotic cells. CoQ10 could antagonize the apoptosis inducing effect of EtOH. The inhibition of cell apoptosis by CoQ10 was significant at 8 and 12 h after EtOH exposure. In EtOH-exposed corneal fibroblasts, CoQ10 pretreatment significantly reduced mitochondrial depolarization and ROS production at 30, 60, 90, and 120 min and inhibited the activation and expression of caspases 2 and 3 at 2 h after EtOH exposure. In summary, pretreatment with CoQ10 can inhibit mitochondrial depolarization, caspase activation, and cell apoptosis. These findings support the proposition that CoQ10 plays an antiapoptotic role in corneal fibroblasts after ethanol exposure. [ABSTRACT FROM AUTHOR]

A novel ultrawideband (UWB) antenna referred to as the inverted-hat antenna (IHA) is described. Specifically, the paper provides a systematic approach to generate a frequency-scaled IHA structure subject to aperture width and height constraints. An experimental verification is also given. The proposed compact wideband antenna exhibits frequency-independent behavior by introducing a moderate number of appropriately scaled elliptical segments and by controlling the outer surface growth profile. A modified seven-ellipse IHA is demonstrated in this paper to provide a 10:1 impedance bandwidth with satisfactory radiation properties. The simulation and measurement results are in reasonably good agreement. [ABSTRACT FROM AUTHOR]

In low-profile applications, ground plane backing significantly degrades antenna performance when the electrical height is a small fraction of a wavelength. An approach to suppress the destructive interference from the ground plane reflections is to employ absorbing layers of ferrite materials. In this paper, we introduce a means to also control and utilize the mode excited in these finite ferrite layers to recover antenna performance at ultra/very high frequencies. Experimental verification is provided using commercial ferrite materials. [ABSTRACT FROM AUTHOR]

In low-profile applications, the antenna is often positioned very closely to an electrically conducting surface, or ground plane. Such a ground-plane backing significantly degrades antenna performance when the electrical height is less than λ/15. Existing approaches, such as lossless electromagnetic bandgap (EBG) structures and artificial magnetic conductors (AMC), tend to operate over a small bandwidth. This paper discusses two alternative ultra-wideband (UWB) approaches that laminate the ground plane with special magneto-dielectric (or ferrite) layers. The first approach employs a ferrite layer with a high μ[subr]/ϵ[subr] ratio to produce an in-phase reflection, similar to that caused by a perfect magnetic conductor (PMC). The second approach adapts a lossy ferrite with similar values of relative permeability, μ[subr], and relative permittivity, ϵ[subr]. Radiation enhancements achieved via these ground-plane treatments will be demonstrated by simulated and measured examples. Design guidelines based on a parametric study will also be discussed. [ABSTRACT FROM AUTHOR]

A novel mobile antenna structure is presented to relay stress and strain data on railroad tracks. The antenna structure is a unique design employing dual probe-fed radiating cavities integrated with a Zigbee IEEE 802.15.4 wireless transceiver. This structure is mounted against the rail web and has a compact design to ensure survivability. A dielectric filler is employed inside each radiating cavity to minimize cavity width and protect the integrity of the mobile antenna structure. Measurements are given for a fabricated prototype to verify simulated performance characteristics. [ABSTRACT FROM AUTHOR]

A lossy transmission-line model that incorporates the radiation resistance of small loop antennas is introduced to characterize the input impedance of a spiral antenna over a large frequency range. This model also leads to a concept of controlling the current velocity and impedance on a spiral antenna by introducing distributed reactive loading along the spiral arms. An important application of the concept is to reduce antenna size and this is demonstrated by numerical simulation examples. [ABSTRACT FROM AUTHOR]

The response from targets illuminated by a transient plane wave the time dependence of which takes the form of a ramp function has been used to generate signatures for conductive and penetrable targets. Modified geometrical profile functions of various targets are used to generate their ramp response, which in turn is used to evaluate their scattered fields as a function of frequency. In early time, the ramp response is proportional to the physical cross-sectional area of the target (as a function of time or distance as the wave propagates over the target). Thus, the ramp response can be generated from the target's geometry. This is then Fourier transformed to obtain the spectrum of the ramp response. To obtain the spectrum of the impulse response, this result is simply multiplied by (jω)2, where ω is the angular frequency. These simple steps can be readily performed by anyone with an electrical engineering background to obtain the backscattered fields to a reasonable approximation. These same fundamentals can also be used to approximate a target's image from the measured ramp response. This has been done for axial incidence of rotationally symmetric targets. It can be extended to non-rotationally symmetric targets using an iterative process. [ABSTRACT FROM AUTHOR]

An ultrawide bandwidth (UWB) dielectric horn antenna (DHA) design is presented. This DHA design provides dual-linear polarization with similar E- and H-plane patterns and a near-constant beamwidth from 2 to 18 GHz. The fixed phase center makes it an excellent candidate for feeding a reflector. The DHA is composed of a resistively terminated broadband field launcher, a solid dielectric horn body, and microwave absorbers for suppressing lateral waves and back lobes. Desirable beamwidth can be achieved by choosing a specific horn angle. A design example that shows a beam aspect ratio (BAR) close to one and approximately 110-degree 10-dB beamwidth is presented. The measured results are validated by full-wave simulations with the finite difference time domain (FDTD) method. [ABSTRACT FROM AUTHOR]

A novel proximity-fed stacked patch antenna is presented to cover the new GPS band, namely L5 (1176 MHz, available after 2007) together with the L1 and L2 bands (1575 and 1227 MHz). High permittivity dielectric material is used to minimize the antenna size down to 1.2″ × 1.2″, implying an aperture size of only λ/8 × λ/8 at the L5 band. Quadrature phase feeding is employed to ensure RHCP radiation, with a broadside gain of 2 dBi. Because of its reduced size, the presented antenna can be used within a GPS antenna array or other tri-band GPS applications. The design procedures and employed tuning techniques to achieve the desired performance are presented. [ABSTRACT FROM AUTHOR]

A novel ultra-wide-bandwidth dual-polarization feed design for launching spherical fields into a tapered chamber is introduced. This new design provides improved bandwidth and field quality, which should enhance measurement accuracy and sensitivity. This feed is integrated into the feed section of tapered chambers, and thus eliminates the need for opening the feed section for placing different antennas. The quad-ridge wave-launcher partially embedded in the wall absorbers allows for lower operational frequencies. [ABSTRACT FROM AUTHOR]

The miniaturization of a broadband square slot spiral antenna is proposed using high-contrast (ϵr > 30) dielectric materials. A previously developed circular slot spiral antenna is the starting point of the design. This spiral is first modified in terms of its feed and termination to facilitate the dielectric loading of the antenna by means of a superstrate. The subsequently placed superstrate is also modified by tapering its thickness to improve impedance matching. Several measurements were carried out using square spiral apertures having diameters of 2" and 6", respectively. It is demonstrated that the ceramic loading of a 2" spiral with an ϵr. = 90 shifts the initial operating frequency by nearly 320 MHz down to 564 MHz representing a size reduction of 36%. Additionally, a 6" aperture loaded with a superstrate having ϵr = 30 is shown to operate down to 270 MHz corresponding to a size reduction of 18 %. [ABSTRACT FROM AUTHOR]

It is widely acknowledged that tree roots and other forms of buried biomass can have an adverse effect on the performance of ground-penetrating radars (GPRs). In this paper, we present analyses that examine that effect for ground-contacting GPR systems. A test site containing extensive root infiltration at Eglin Air Force Base, FL, was excavated, and the root structure and soil were thoroughly characterized. A numerical simulator based on the discrete dipole approximation, which is an integral-equation-based method, was developed, validated, and subsequently used to compute scattering from root structures modeled by an ensemble of buried cylinders. An examination of the results is presented that quantifies the potential for false alarms and increased clutter due to buried roots. [ABSTRACT FROM AUTHOR]

A new ultrawide-bandwidth dielectric-rod antenna is presented with its application in detecting shallow targets, such as antipersonnel (AP) mines. The lowest hybrid mode is launched and guided along a circular-dielectric waveguide. The end of the waveguide is tapered to a point where electromagnetic waves are radiated out with field behavior similar to that radiated from a Hertzian dipole in the forward direction. The low antenna clutter and weak antenna-ground interaction are two unique features. Its near-field radiation properties are investigated by directly probing the fields and by numerical simulation with a three-dimensional finite-difference time-domain technique. Both measurement and numerical simulation results are presented for the detection of buried AP mines using a prototype dielectric-rod antenna operated at a frequency range from 1 to 6 GHz. [ABSTRACT FROM AUTHOR]

Presents a study which used an ultrawide-bandwidth ground penetrating radar to collect fully-polarimetric backscattered data using a dual-polarization version of the dielectric-loaded horn-fed bow-tie antenna. Feature extraction for unexploded ordnance (UXO)-like targets; UXO classification results; Problem associated with the polarization feature for small objects close to surface.

A single-fed circularly polarized stacked patch antenna is proposed to cover all GPS bands, including the E5a/E5b band for the Galileo system. The small aperture size (λ8 at 1176 MHz, the L5 band) makes this antenna attractive for small GPS arrays. Also, in contrast to previous GPS antennas, the presented design uses a single feed for circular polarization. In this paper, we present the design procedures and performance of the designed GPS antenna and discuss issues relating to coupling between array elements. Modifications to reduce coupling are then presented. [ABSTRACT FROM AUTHOR]

A foreword to the to the special issue of "IEEE Transactions on Geoscience and Remote Sensing" about subsurface sensing using ground-penetrating radar (GPR) is presented.

A patch bandwidth-broadening technique is introduced by modifying the dielectric under the square patch. The dielectric modification is guided by the field intensity under the original uniform substrate. This broadening technique is particularly attractive for high-contrast substrates that are often used for miniaturization. An example design is measured for demonstration. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 421–423, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21189 [ABSTRACT FROM AUTHOR]

Pemetrexed is approved for first-line and maintenance treatment of patients with advanced or metastatic non-small-cell lung cancer (NSCLC). The protein kinase Akt/protein kinase B is a well-known regulator of cell survival which is activated by pemetrexed, but its role in pemetrexed-mediated cell death and its molecular mechanisms are unclear. This study showed that stimulation with pemetrexed induced S-phase arrest and cell apoptosis and a parallel increase in sustained Akt phosphorylation and nuclear accumulation in the NSCLC A549 cell line. Inhibition of Akt expression by Akt specific siRNA blocked S-phase arrest and protected cells from apoptosis, indicating an unexpected proapoptotic role of Akt in the pemetrexed-mediated toxicity. Treatment of A549 cells with pharmacological inhibitors of phosphatidylinositol 3-kinase (PI3K), wortmannin and Ly294002, similarly inhibited pemetrexed-induced S-phase arrest and apoptosis and Akt phosphorylation, indicating that PI3K is an upstream mediator of Akt and is involved in pemetrexed-mediated cell death. Previously, we identified cyclin A-associated cyclin-dependent kinase 2 (Cdk2) as the principal kinase that was required for pemetrexed-induced S-phase arrest and apoptosis. The current study showed that inhibition of Akt function and expression by pharmacological inhibitors as well as Akt siRNA drastically inhibited cyclin A/Cdk2 activation. These pemetrexed-mediated biological and molecular events were also observed in a H1299 cell line. Overall, our results indicate that, in contrast to its normal prosurvival role, the activated Akt plays a proapoptotic role in pemetrexed-mediated S-phase arrest and cell death through a mechanism that involves Cdk2/cyclin A activation.