Vichate Ungvichian

EFFECTS OF 60 HZ AC MAGNETIC FIELDS ON GENE EXPRESSION FOLLOWING EXPOSURE OVER MULTIPLE CELL GENERATIONS USING SACCHAROMYCES CEREVISIAE

Abstract We are reporting that gene expression in the unicellular yeast, Saccharomyces cerevisiae , is altered in response to continuous exposure to 20 μT 60Hz AC electromagnetic fields (EMF) over a period of approximately 15 cell generations. This effect was indicated by changes in the steady-state abundance of specific messenger RNAs (mRNA). To evaluate changes in mRNA levels, we used two-dimensional gel electrophoresis of in vitro translation products. For the majority of mRNAs examined (44–67%), differential effects on transcript levels were no different than those observed in sham-exposed experiments. However, the relative abundance of a significant proportion of mRNAs (26–38%) was increased at least 2-fold in cells exposed to EMF. Finally, a smaller percentage of mRNAs (7–18%) showed decreased levels (below 50% of control) in the EMF-exposed cells.

Effects of Substrate Permittivity on Planar Inverted-F Antenna Performances

This paper quantifies the gain and matching bandwidth variations of a planar inverted-F antenna (PIFA) for several dielectric substrates. The performance of the PIFA is assessed in two configurations. First, the PIFA is studied with different substrates for a radiating patch of fixed dimensions of 4.92 cm x 2.13 cm. The effects of the dielectric constant of the perfect and lossy substrates on the resonant frequency, bandwidth and gain are investigated. A gain drop of 2 dB per decade is observed. In the second evaluation, the physical dimensions of the radiating element of the PIFA are adjusted to achieve resonance at 1.14 GHz. The gain drop reduces to 1.5 dB per decade.

A study of crosstalk applied to ultra-high-speed parallel lossy microstrip and strip lines with shielding effectiveness

Several researchers have reported that in some cases the crosstalk in the lossless ultra-high-speed parallel microstrip transmission lines does not necessarily reduce by increasing the spacing in between the two lines. In this study, the substrate loss parameters which are dielectric and conductor are included in the calculation. Furthermore, the influence of a near-by cover plate which provides shielding is also considered. The technique used to calculate the crosstalk is based upon accurate wide-range closed form expressions for the frequency-dependent parameters in conjunction with a linear system theory and Fourier theory. The simulations using Gaussian pulses with different widths as input source have indicated that the crosstalk decreases nonmonotonically for certain s/h and pulse-width of less than 20 picoseconds. Also the crosstalk can be reduced further by using a cover plate mounted sufficiently close to the transmission lines.

An EMI Immunity Study of TMR Heads in Quasi-Static Tester due to the Direction of Sweeping Frequency

This report aims to investigate a comparative effect of Electromagnetic Interference (EMI) on recording heads due to sweeping directions of low-to-high and high-to-low frequencies. Four selected Quasi-Static Tester (QST) parameters; MR resistance, MR amplitude asymmetry, Barkhausen noise and Hysteresis, are used for monitoring the effect of EMI on Head Gimbal Assembly (HGA). It is undoubtedly found that the Asymmetry and Hysteresis parameters provide insufficient indication of EMI effect for both sweeping frequency directions. On the other hand, it is discovered that the sweeping direction of the low-to-high frequency is more effective to two test parameters; MR resistance and Barkhausen noise, than the other direction. The dramatic energy accumulation is possibly explained this phenomenon but this energy level is not high enough to cause the Hysteresis change.

Anomalous magnetic responsiveness of giant magnetoresistive heads under specific electromagnetic interference frequencies using quasistatic tester

The giant magnetoresistive (GMR) heads have been used in the computer industry for decade. Recently, the anomalous performance caused by cell phones or external electromagnetic interference (EMI) is reported [V. Kraz and A. Wallash, J. Electrost. 54, 39 (2002)]; [Kruesubthaworn et al., J. Magn. Magn. Mater. 316, e142 (2007)] This prompts an experimental study of an anomalous magnetic disturbance to the heads under ascending and descending frequency variations. The rf generator with predetermined output is set for 30–1000MHz swept frequency in both directions, with the antenna being horizontal and vertical orientations. Five quasistatic tester (QST) parameters; magnetoresistive (MR) resistance, MR amplitude, asymmetry, Barkhausen noise, and hysteresis are used as markers in the EMI sensitivity study of head gimbal assembly. It is found that the worst change of MR amplitude is 10.2% (marginally over the norm), which occurs at 910MHz during ascending swept frequency and horizontal polarization. The largest v...

A positive step toward education in electromagnetic compatibility

In response to the needs of the local electronics industry, an undergraduate electromagnetic compatibility (EMC) course was introduced at Florida Atlantic University, in the Department of Electrical and Computer Engineering. The course stsructure is outlined and some of the problems encountered in teaching such a course are discussed. Recommendations are included for others planning a similar course. >

The effects of an additional shorting stub on PIFA performance

A planar inverted-F antenna (PIFA) is known for its low-profile and compactness as compared to rectangular microstrip antennas. The shorting element in PIFA generates a quarter-wave resonance which reduces the physical dimensions of the antenna by at least 50%. In this paper, the effects of an additional shorting stub on an FR4-epoxy substrate PIFA are investigated. Computational and experimental VSWR results are reported for a PIFA with and without an additional short. It is observed that the additional shorting element increases the resonant frequency from 590 MHz to 950 MHz, or by 60%, while preserving the return loss. Additionally, simulation results reveal a 4 dB gain improvement for the modified PIFA at the resonant frequency.

A titanium-dioxide based ceramic composite dispersed with conducting inclusions as an EMI shielding material

A class of composite materials constituted by conducting inclusions dispersed in a host ceramic medium (such as TiO/sub 2/) is described. This test composite is studied as a potential EMI (electromagnetic interference) shielding material. A mixture formula for predicting the effective electrical conductivity of the test composite in terms of the volume fraction and geometric aspect of the conducting inclusions and the permittivity of the host medium is indicated for calculating the shielding effectiveness of the material. Theoretical and experimental results are furnished and discussed. Depending on the conducting particulate loading, the shielding effectiveness of the composite(s) falls in the range of 5-20 dB over the frequency range of 500 MHz to 1 GHz.<<ETX>>

Electromagnetic fields due to overhead and buried high-voltage power-lines: a quantitative comparison

Possible health hazards due to nonionizing radiations emanating from high-voltage power-lines are addressed. Specifically, the magnetic field due to power-line radiation has been considered as an etiological factor in some form(s) of childhood cancer. An investigation of the possibility of reducing the magnetic field effect nEar the earths surface by burying the power lines was conducted. The overall electromagnetic field distributions due to buried and overhead lines are elucidated and the explicit advantages (if any) in burying cables are verified quantitatively. It is concluded that it is indeed possible to suppress the magnetic field influence near the Earths surface by burying the high-voltage cable. The extent of suppression will vary considerably in relation to proximity and stand-off regions. Suppression of magnetic influence near the Earths surface is effective when the buried cable has minimum conductance leakage of energy into the surrounding medium.<<ETX>>

A Study of substrate permittivity effects on the gain of planar inverted-F antennas

A planar inverted-F antenna (PIFA) of fixed dimensions, with a 4.92 cm x 2.13 cm radiating element 4.4 mm high above the ground plane is evaluated with different substrates. The resonance frequency, the bandwidth and the gain are studied in relation to the relative dielectric constant of the perfect and lossy substrates. The results reveal that the normalized resonance frequency (Deltaf/f) decreases logarithmically and the gain drops linearly with a slope of 2 dB per decade.