Association of Leptin and Adiponectin Levels with Three-yearWeight Change among Japanese Male Workers

The purpose of this study was to clarify, through a prospective study, the relationship between leptin and adiponectin levels, and subsequent weight change. The study subjects were 2,485 male office workers aged 35-64 employed by a company in Fukuoka Prefecture, Japan. Of these men, 1,936 (77.9%) received health check-ups both in 2005-2007 and 3 years later, in 2008-2010. Of the subjects who received both health check-ups, 352 were excluded duo to cancer, cardiac infarction, stroke or diabetes mellitus, leaving a total of 1,584. We divided them into tertiles according to baseline leptin and adiponectin levels, and compared the subsequent change in body mass index (BMI) over 3 years. The subjects with the lowest leptin levels showed a significantly greater increase in BMI (difference in change in BMI＝0.178kg/m2, 95% CI:0.025-0.331kg/m2) over 3 years when those with the highest leptin levels were regarded as the reference even after adjusting for age, baseline BMI, smoking status, drinking status and exercise. The subjects with the highest adiponectin levels showed a greater increase in BMI (difference in change in BMI＝0.099kg/m2, 95% CI:－0.034-0.231kg/m2) over 3 years when those with the lowest adiponectin levels were regarded as the reference, but this association was not statistically significant after adjusting for age, baseline BMI, smoking status, drinking status and exercise. Our findings suggest that higher leptin levels may suppress weight gain in Japanese male workers

Using Square Wave Input for Wireless Power Transfer

A wireless power transfer (WPT) circuit is composed of a transmitting circuit with an AC power supply and a receiving circuit with a load, and the circuits are wirelessly connected each other. Then a designer chooses the wave form of the AC power supply. Many papers about WPT adopt a sinusoidal wave as the input. The frequency of the sinusoidal wave is generally determined to the resonant frequency of the circuit for high power transfer. Since the number of circuit elements in the power supply to generate a square wave is much less than that of a sinusoidal wave, WPT with a square wave input should be treated. In fact, some papers about WPT adopt a square wave as the input, and adjust the frequency of the square wave to the resonant frequency of the circuit. In this paper, we examine how the frequency of a square wave input affects power and efficiency of WPT circuits, and propose a procedure how to determine the frequency of the input to improve power and efficiency. Finally we discuss which wave should be adopted as an input and how the frequency of the input should be determined, regardless of whether resonant phenomena occur or not

A General Method to Parameter Optimization for Highly Efficient Wireless Power Transfer

This paper proposes a new and general method to optimize a working frequency and a load resistance in order to realize highly efficient wireless power transfer. It should be noticed that neither resonant frequency nor matched impedance maximizes efficiency of wireless power transfer circuit, in general. This paper establishes a mathematical model of a commonly used wireless power transfer circuit, and derives a mathematical expression of circuit efficiency which involves a working frequency, a load resistance and the other parameters as symbols. This enables us to find the optimal workingfrequency and load resistance. The result of this paper is compared with results by a method based on resonance and impedance matching, and then clarified by a numerical example

A Criterion on Existence and Uniqueness of Behavior in Electric Circuit

Behavior of electric circuits can be observed by solving circuit equations symbolically as well as numerically. In general, symbolic computation for circuits with certain number of circuit elements needs much more time than numerical computation. It is reasonable to check the existence and uniqueness of the solution to circuit equations beforehand in order to avoid computation for the case of no solution. Indeed, some circuits have no solution; in that case, one should notice it and avoid to wait meaningless computation. This paper proposes a new theorem to check whether given circuit equations have a solution and their voltages and currents of all circuit elements are uniquely determined or not. The theorem is suitable for developing a computer algorithm and helps quick symbolic computation for electric circuits