Classification of heavy-metal toxicity by human DNA microarray analysis

Microarray technology is proving to be a useful tool to classify undefined environmental toxicants, to investigate underlying mechanisms of toxicity, and to identify candidate toxicant-specific genetic markers by examining global effects of putative toxicants on gene expression profiles. The aim of this study was to evaluate the toxicities of six heavy metals through the comparison with gene expression patterns induced by well-known chemicals. For this purpose, we first identified the genes altered specifically in HepG2 under the exposure of 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), phenol, and N-nitrosodimethylamine (DMN), which were selected as the model chemicals, using DNA microarray. On the basis of the expression profiles of these genes, toxicities of six heavy metals, arsenic, cadmium, nickel, antimony, mercury, and chromium, were evaluated. The specific gene alteration and hierarchical clustering revealed that biological action of six heavy metals was clearly related to that of DMNQ which has been reported to be a reactive oxygen species (ROS) generating chemical and which induced the genes associated with cell proliferative responses. These results suggest that cell proliferative responses which are probably caused by ROS are a major apparent biological action of high-dose heavy metals, supporting the previous reports. Overall, a mechanism-based classification by DNA microarray would be an efficient method for evaluation of toxicities of environmental samples.     

A matching transformer‐less inrush current suppressor for transformers using a series‐connected small‐rated voltage‐source PWM converter—consideration of the control gains and required ratings of the PWM converter

This paper proposes a new inrush current suppressor using a series‐connected small‐rated PWM converter for a transformer. The PWM converter is directly connected in series between the source and transformer without a matching transformer. The inrush phenomena of the matching transformer, thus, can be avoided. The control gain and required ratings of the series‐connected small‐rated PWM converter are discussed in detail. The capacity of the DC capacitor of the PWM converter is also discussed considering the active power flows into the PWM converter. The PSCAD/EMTDC is used to verify the validity of the proposed inrush current suppressor. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed suppressor can perfectly overcome the inrush phenomena of transformers. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(3): 45–55, 2007; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.20374     

A parallel algorithm for allocation of spare cells on memory chips

The authors propose a parallel algorithm based on the artificial neural network model for solving the spare-allocation problem. The goal is to find a spare allocation which repairs all the faulty cells in the given faulty-cell map. The parallel algorithm requires 2n processing elements for the n×n faulty-cell map problem. The algorithm is verified by many simulation runs. Under the simulation the algorithm finds one of the near-optimum solutions in a nearly constant time with O(n) processors. The simulation results show the consistency of this algorithm. The algorithm can be easily extended for solving rectangular or other shapes of fault map problems     

A PWM-controlled rectifier step up/down output voltage with a high power factor

It is desirable that the rectifier that is an ac-to-dc converter, have the characteristics of fast response and the wide range of the output voltage control, and the sinusoidal source current waveform. In this paper, a step up/down output voltage PWM-controlled rectifier is proposed. The features of the proposed rectifier are as follows. (1) The calculation of pulsewidth is based on the geometrical technique and the source current can be inphase with the source voltage. (2) The output voltage is controlled from about zero to more than the maximum value of the source voltage. The aforementioned features are clarified by simulation and the steady-state characteristics are discussed. Further, these results are verified in experiment using the microprocessor-based control system.     

A binary Hopfield neural-network approach for satellite broadcastscheduling problems

This paper presents a binary Hopfield neural network approach for finding a broadcasting schedule in a low-altitude satellite system. Our neural network is composed of simple binary neurons on the synchronous parallel computation, which is greatly suitable for implementation on a digital machine. With the help of heuristic methods, the neural network of a maximum of 200000 neurons can always find near-optimum solutions on a conventional workstation in our simulations.     

An Improved Approximation Algorithm for the Traveling Tournament Problem

This paper describes the traveling tournament problem, a well-known benchmark problem in the field of tournament timetabling. We propose an approximation algorithm for the traveling tournament problem with the constraints such that both the number of consecutive away games and that of consecutive home games are at most k. When k≤5, the approximation ratio of the proposed algorithm is bounded by (2k−1)/k+O(k/n) where n denotes the number of teams; when k>5, the ratio is bounded by (5k−7)/(2k)+O(k/n). For k=3, the most investigated case of the traveling tournament problem to date, the approximation ratio of the proposed algorithm is 5/3+O(1/n); this is better than the previous approximation algorithm proposed for k=3, whose approximation ratio is 2+O(1/n).     

A new method of damping harmonic resonance at the DC link in a large‐capacity rectifier‐inverter system

This paper proposes a new method of damping harmonic resonance in the DC link of a large‐capacity rectifier‐inverter system, such as in rapid‐transit railways. A voltage‐source PWM converter is connected in series to the DC capacitor of the rectifier through a matching transformer, acting as a damping resistor to the DC capacitor current. No filters are needed to extract harmonic components from the DC capacitor current. This results in a quick response and highly stable damping. The relationship between the control gain of the PWM converter and the required rating is theoretically discussed. We show that the required rating is less than one‐thousandth of that previously proposed. In particular, regenerating the power consumed by the PWM converter is very important because of the large power in practical systems. Normally, an additional PWM inverter is connected to the DC bus of the PWM converter to regenerate the consumed power. The additional inverter regenerates the DC power to the AC source through a transformer. This method, however, makes the damping circuit complex, thus the proposed method for the DC‐link harmonic resonance is less practicable. In this paper, a simple and novel scheme that utilizes the DC‐link voltage of the rectifier as a DC source for the PWM converter is proposed. The excellent practicability of the proposed damping method with the novel regenerating scheme is confirmed using digital computer simulation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(2): 53–62, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10172