Acquired or inherent drug resistance is the major problem in achieving successful cancer treatment. However, the mechanism(s) of pleiotropic drug resistance remains obscure. We have identified and characterized a cellular metabolic strategy that differentiates drug-resistant cells from drug-sensitive cells. This strategy may serve to protect drug-resistant cells from damage caused by chemotherapeutic agents and radiation. We show that drug-resistant cells have low mitochondrial membrane potential, use nonglucose carbon sources (fatty acids) for mitochondrial oxygen consumption when glucose becomes limited, and are protected from exogenous stress such as radiation. In addition, drug-resistant cells express high levels of mitochondrial uncoupling protein 2 (UCP2). The discovery of this metabolic strategy potentially facilitates the design of novel therapeutic approaches to drug resistance.

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A method for the design of minimum-phase FIR digital filters using spectral factorization is described. In the proposed method, the required digital filter is designed by formulating a set of nonlinear equations that represent the design problem at hand and then solving it by using the Levenberg-Marquardt optimization method. By using an exact formulation of the Jacobian and Hessian matrix in the Levenberg-Marquardt method, significant performance improvement and fast convergence is achieved. Comparisons show that the new method leads to a significant reduction in the maximum value and L2 norm of the residual error relative to those in state-ofthe-art competing methods.

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A method for the design of ultraspherical window functions that achieves prescribed spectral characteristics is proposed. The method comprises a collection of techniques that can be used to determine the three independent parameters of the ultraspherical window such that a specified ripple ratio and main-lobe width or null-to-null width along with a user-defined side-lobe pattern can be achieved. Other known two-parameter windows can achieve a specified ripple ratio and main-lobe width; however, their side-lobe pattern cannot be controlled as in the proposed method. A comparison with other windows has shown that a difference in performance exists between the ultraspherical and Kaiser windows, which depends critically on the required specifications. The paper also highlights some applications of the proposed method in the areas of digital beamforming and image processing

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Abstract-Peak-to-average power-ratio (PAPR) reduction for OFDM systems is investigated in a probabilistic framework. A new constellation extension technique is developed whereby the data for each subcarrier are represented either by points in the original constellation or by extended points. An optimal representation of the OFDM signal is achieved by using a de-randomization algorithm where the conditional probability involved is handled by using the Chernoff bound and the evaluation of the many hyperbolic cosine functions involved is replaced by a tight upper bound for these functions. The proposed algorithm can be used by itself or be combined with a selective rotation technique described in the paper and with other known algorithms such as the coordinate descent optimization and selective mapping algorithms to achieve further performance enhancements at the cost of a slight increase in the computational complexity. When compared with other existing PAPR-reduction algorithms, the enhanced algorithm offers improved PAPRreduction performance and improved computational complexity although the transmit power is increased somewhat.