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Novel broadband monopole antenna designs with dual-band circular polarization (CP) are presented. The proposed antenna comprised of a ground plane embedded with an inverted-L slit, which is capable of generating a resonant mode for broadband impedance-bandwidth, and excites two orthogonal E vectors with equal amplitude and 90[degrees] phase difference (PD) for radiating left-hand circular polarization (LHCP) at 2.5 GHz and right-hand circular polarization (RHCP) at 3.4 GHz. A bevel is cut in the rectangular radiator to increase the impedance-band-width. The measured result of the impedance-bandwidth is about 4.46 GHz from 2.12 to 6.58 GHz; the 3-dB axial ratio (AR) bandwidths are about 150 MHz at the lower band (2.5 GHz) and 230 MHz at the upper band (3.4 GHz). Furthermore, embedding an I-shaped slit in the rectangular radiator and adding an I-shaped stub in the ground plane, the impedance-bandwidth can be further increased to 6.30 GHz (2.17-8.47 GHz), and the 3-dB AR-bandwidth at the upper band is greatly enhanced from 230 to 900 MHz. Index Terms--Axial ratio (AR), broadband antennas, circular polarization (CP), monopole antennas.

A new technique is proposed to increase the bandwidth (BW) of a Z-like slot antenna for operation at 2.4 GHz and 5 GHz, over the industrial-scientific-medical (ISM) bands and the Hiperlan2 bands. By splitting two side slots of the Z-like slot antenna into two or three fingers, several additional resonances can be created. After careful optimization of the geometrical parameters of the antenna, the resonances are merged and thus a wide impedance bandwidth is obtained. Index Terms--Double-slot, symmetrically tuning stub, triple-slot, Z-like slot.

This paper describes a two-directional linear scanned design by integrating a short leaky-wave antenna (LWA) with aperture-coupled patch antenna arrays. This architecture proposes a technique not only having the advantage of suppressing the backlobe due to the reflected wave in the short LWA but also producing two separate linearly scanned beams, each of them radiating in a different region of space (in both the front side and backside of the LWA). In this design, most of the reflected wave of the short LWA is coupled to the patch antenna arrays on the backside of the substrate. The phase of this coupled signal to each antenna element is adjusted by tuning the individual phase shifter in order to control electronically the patch antenna main beam in the cross plane (x < 0). Meanwhile, on the front side, the main beam of the short LWA can be simultaneously scanned in the elevation plane (x > 0) by changing the operating frequency. Hence, the two linear beam-scanning radiation patterns of individual direction can be created independently, including a narrow beam in the elevation plane (xy plane at x > 0) at the front side and a broadside beam in the cross plane (xz plane at x < 0) on the backside. The measured results show that the reflected wave of the short LWA in the proposed design is suppressed 8 dB as compared with a traditional short LWA without the aperture-coupled antenna arrays at 10.5 GHz. As a result, this novel architecture provides more flexibility both in the upward elevation plane (H plane) and the downward cross plane (backside-E plane) for possible beam-scanning applications in microwave communications and remote identification. Index Terms--Aperture-coupled patch antenna arrays, phase shifter, reflected wave, varactor diode.

A novel two-beam scanning active leaky-wave antenna (LWA) has been developed. This LWA with a two-terminal feeding microstrip line structure is integrated with a varactor-tuned X-band high-electron mobility transistor (HEMT) voltage-controlled oscillator (VCO). The signal of the VCO is injected via a T-divider into the radiating element. To excite the first higher order mode, the designed antenna is fed asymmetrically at both ends of the microstrip line. Compared with single-terminal feeding leaky-wave antennas, this configuration offers the advantages of dual-direction and suppression of the reflected wave caused by the open end of the radiating element. The scanning angle is steered over a range of 24-46 degrees for the right beam and 128-150 degrees for the left beam. The Effective isotropic radiated power (EIRP) is calculated to be 17.5 and 16.67 dBm at 10.4 GHz, respectively. The measured return loss S(sub 11) is less than -10 dB in the range of 9-11.5 GHz. The transmission coefficient S(sub 21) indicated that the power radiates into the space. Index Terms: Leaky-wave antennas, microstrip transmission lines, printed antennas, scanning antennas.

Previous studies have shown that phthalate exposure in childhood is associated with the development of respiratory problems. However, few studies have assessed the relative impact of prenatal and postnatal exposure to phthalates on the development of asthma later in childhood. Therefore, we assessed the impact of prenatal and postnatal phthalate exposure on the development of asthma and wheezing using a Taiwanese birth cohort. A total of 430 pregnant women were recruited, and 171 (39.8%) of them had their children followed when they were aged 2, 5, and 8 years. The International Study of Asthma and Allergies in Childhood questionnaire was used to assess asthma and wheezing symptoms and serum total immunoglobulin E levels were measured at 8 years of age. Urine samples were obtained from 136 women during their third trimester of pregnancy, 99 children at 2 years of age, and 110 children at 5 years. Four common phthalate monoester metabolites in maternal and children’s urine were measured using liquid chromatography-electrospray ionization-tandem mass spectrometry. Maternal urinary mono-benzyl phthalate [MBzP] concentrations were associated with an increased occurrence of wheezing in boys at 8 years of age (odds ratio [OR] = 4.95 (95% CI 1.08–22.63)), for upper quintile compared to the others) after controlling for parental allergies and family members' smoking status. Urinary mono-2-ethylhexyl phthalate [MEHP] levels over the quintile at 2-year-old were associated with increased asthma occurrence (adjusted OR = 6.14 (1.17–32.13)) in boys. Similarly, the sum of di-2-ethyl-hexyl phthalate [DEHP] metabolites at 5 years was associated with asthma in boys (adjusted OR = 4.36 (1.01–18.86)). Urinary MEHP in maternal and 5-year-old children urine were significantly associated with increased IgE in allergic children at 8 years. Prenatal and postnatal exposure to phthalate was associated with the occurrence of asthma in children, particularly for boys. [ABSTRACT FROM AUTHOR]

We conducted a repeated-measures cohort study of coke oven workers to evaluate the relationships between the traditional exposure biomarker, urinary 1-hydroxypyrene (1-OHP), and a series of biomarkers, including urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), N7-methylguanine (N7-MeG), acute toxicity, and mutagenicity. A total of eight spot urine samples were collected from each high-exposed (at topside oven area) and low-exposed workers (at side oven area) during the whole working cycle, which consisted of 6 consecutive days of working followed by 2 days off. Our results showed that the high-exposed workers had significantly higher urinary levels of 1-OHP, 8-oxodG, and N7-MeG compared with the low-exposed workers. Acute toxicity and mutagenicity of urine were also found to be markedly increased in the high-exposed workers, as determined by Microtox assay and Ames test, respectively. Multivariate regressions analysis revealed that the urinary 8-oxodG, N7-MeG, or acute toxicity was significantly correlated with 1-OHP concentrations. Overall, the present study showed that exposure to coke oven emissions increased oxidatively damaged DNA products and mutagenicity of urine, and for the very first time, such exposure was also found to increase DNA methylation and urinary acute toxicity. The potential source of methylating agents in coke oven emissions warrants further investigation. Additionally, with repeated measurements, the pattern of time course for urinary 1-OHP was found to be different from those of 8-oxodG and N7-MeG, as well as acute toxicity and mutagenicity. This finding implies that the single measurement that was often conducted in occupational healthy investigations should be used with certain precautions, because single measurement may fail to provide the proper information of interest.