TMz Mode Research Articles

Accidental Encounter of Repair Intermediates in Alkylated DNA May Lead to Double-Strand Breaks in Resting Cells.

In clinics, chemotherapy is often combined with surgery and radiation to increase the chances of curing cancers. In the case of glioblastoma (GBM), patients are treated with a combination of radiotherapy and TMZ over several weeks. Despite its common use, the mechanism of action of the alkylating agent TMZ has not been well understood when it comes to its cytotoxic effects in tumor cells that are mostly non-dividing. The cellular response to alkylating DNA damage is operated by an intricate protein network involving multiple DNA repair pathways and numerous checkpoint proteins that are dependent on the type of DNA lesion, the cell type, and the cellular proliferation state. Among the various alkylating damages, researchers have placed a special on O6-methylguanine (O6-mG). Indeed, this lesion is efficiently removed via direct reversal by O6-methylguanine-DNA methyltransferase (MGMT). As the level of MGMT expression was found to be directly correlated with TMZ efficiency, O6-mG was identified as the critical lesion for TMZ mode of action. Initially, the mode of action of TMZ was proposed as follows: when left on the genome, O6-mG lesions form O6-mG: T mispairs during replication as T is preferentially mis-inserted across O6-mG. These O6-mG: T mispairs are recognized and tentatively repaired by a post-replicative mismatched DNA correction system (i.e., the MMR system). There are two models (futile cycle and direct signaling models) to account for the cytotoxic effects of the O6-mG lesions, both depending upon the functional MMR system in replicating cells. Alternatively, to explain the cytotoxic effects of alkylating agents in non-replicating cells, we have proposed a "repair accident model" whose molecular mechanism is dependent upon crosstalk between the MMR and the base excision repair (BER) systems. The accidental encounter between these two repair systems will cause the formation of cytotoxic DNA double-strand breaks (DSBs). In this review, we summarize these non-exclusive models to explain the cytotoxic effects of alkylating agents and discuss potential strategies to improve the clinical use of alkylating agents.

Cavity model analysis of 30°–60°–90° triangular microstrip antenna

Modal analysis of probe fed 30°–60°–90° triangular microstrip antenna (TMA) is presented using cavity model for TMz mode. Probe excitation is modeled here in three simple ways. A comparative study among these three types of feed modeling is given in a systematic way, hitherto unreported. Input impedance, quality factor, radiation patterns, efficiency, gain are discussed for first five modes. Closed form expressions for calculating the far-field radiation patterns are given here for the first time. New broadside modes are identified and excited successfully, hitherto unreported. Theoretical results are in good agreement with measured data and/or data obtained using 3D EM simulator. It is found that all first five modes show a peak in broadside direction. The results should be useful for practical design of 30°–60°–90° TMA.

Effect of external electromagnetic waves on a confocal elliptical multiconductor transmission line structure

The influence of external electromagnetic waves on a new kind of transmission line called a confocal elliptical multiconductor transmission line structure is introduced. The capacitance and inductance matrices are obtained to attain transmission line equations. Then a uniform plane wave, TEz or TMz mode, is applied to the structure (normal incidence) to find the induced voltages and currents along the conductors using Bernardi's method. Finally, the results of this analytical method are verified using the fullwave analysis software.

Transmission characteristics of two-dimensional magnetized magnetic photonic crystals

Transmission characteristics of two-dimensional magnetized magnetic photonic crystals (MPCs) have been studied by electromagnetic simulation and experiments in microwave frequencies. MPCs with square and hexagonal lattices are made of ferrites, and their transmission coefficients are measured in the X waveband with an applied static magnetic field. For the lattices, a stop-band and a band shift with the applied static magnetic field are observed. The experimental results are in good agreement with those of electromagnetic simulations when magnetic anisotropy of ferrites is represented by a tensor but deviate from the simulation results when the anisotropy is modelled by an effective permeability of TMz mode.

Numerical Study on Two-dimensional Magnetic Photonic Crystals Made of Magnetized Ferrites

Transmission characteristics of two-dimensional magnetic photonic crystals with square and hexagonal lattice have been studied by full wave electromagnetic simulation. The magnetic photonic crystals are composed of array of fully magnetized ferrite rods. Using FDTD methods, the transmission characteristics of the magnetic photonic crystals are simulated with difierent models of permeability. We flnd that simulation results using tensor permeability of ferrites difier from those of simulation with a scalar efiective permeability of TMz mode, which demonstrates that for magnetic photonic crystals anisotropy of ferrites cannot be simply modeled by an equivalent isotropic magnetic medium. During the last few years, photonic crystals (PCs) (1,2) or photonic band-gap (PBG) materials have been the subject of intensive theoretical and experimental research, due to their promising applications in microwave and optoelectronics (3{7). Generally, PCs are artiflcially constructed from dielectric or metallic materials (7). Recently, some papers are devoted to the investigation of magnetic photonic crystals (MPCs) (8{10). In all these works, the anisotropy of permeability for the magnetic materials in MPCs is modeled by an efiective permeability of TMz mode. Fully magnetized under the external static magnetic fleld ( ~

AN ANALYTICAL INVESTIGATION OF THE RADIATION CHARACTERISTICS OF INFINITESIMAL DIPOLE ANTENNA EMBEDDED IN PARTIALLY REFLECTIVE SURFACES TO OBTAIN HIGH DIRECTIVITY

Abstract—The far-field radiation characteristics of an infinitesimal dipole embedded between two partially reflective surfaces (PRS) to obtain high directivity are studied analytically. The analysis is based on integral summation of spectral radiation fields of the source in cylindrical coordinate, so that we can find the effects of transmission and reflection coefficients of PRS on all components of primary radiation source. The analysis shows that due to the existence of TEz and TMz modes for horizontal dipole source, the effects of PRSs are different for each mode. Also, this study shows that by adjusting the spacing of the plates, it is possible to achieve high directive multibeam patterns.

Radiation analysis in the space domain of laterally shielded planar transmission lines: 1. Theory

In this contribution, the propagation and radiation nature of laterally shielded top‐open planar waveguides (LShPW) is studied by using a discrete spectrum of parallel‐plate waveguide (PPW) TEz and TMz modes. This formulation allows for a simple but precise analysis of the propagation and radiation characteristics associated with the leaky‐wave modes which exist in such planar transmission lines. An approximate novel interpretation of the radiation mechanism is also given by describing each PPW mode as an inhomogeneous plane wave. Comparisons with previous works grant the accuracy of the proposed method. Besides, the analytical and rigorous nature of this approach makes it very suitable for the practical analysis and design of leaky‐wave antennas, as will be discussed in the second part of this work.

Surface-wave propagation along a metamaterial cylindrical guide

The dispersion relations for metamaterial cylindrical guides are found and their Brillouin diagrams are drawn for different guide parameters. It is found that the transverse propagation coefficient of the first TMz mode and the first TEz mode can be either real or imaginary. The longitudinal propagation coefficient of the first TMz mode starts at zero frequency and ends at a frequency where it is equal to the wave-number of the surrounding dielectric medium, while the longitudinal propagation coefficient of the first TEz mode starts at this same frequency and afterwards grows indefinitely. The first hybrid mode of order one as well as subsequent modes are also studied. It is found that for the first TMz and TEz modes, the group velocity is almost constant, whether the transverse propagation coefficient is real or imaginary. Moreover, interesting coupling effects can be obtained by using adjacent metamaterial and dielectric cylindrical guides. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 31–35, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20538