Investigation of false triggering mechanism

This paper discusses a problem that a half‐bridge circuit can generate, namely a false trigger by high‐speed switching transition. In general, a false trigger occurs by charging a gate–source capacitance because of high‐speed voltage transition and influx of current via a reverse transfer capacitance. Therefore, it is thought that the ratio of the input capacitance and the reverse transfer capacitance is important to check whether a false trigger occurs. However, we find another reason and propose a novel assumption. A novel false triggering mechanism appears by considering the source‐side parasitic inductance. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于液晶引流效应的全新微流体驱动方式

对现有微流体驱动技术中普遍存在的微型化难、驱动力小等缺点,提出液晶引流驱动方式。作为开发该驱动方式的第一步,采用理论计算模拟与辅助试验验证相结合的研究方法,以小分子液晶Leslie-Ericksen理论为基础,对上板处于浮动状态下液晶盒的驱动效果及影响因素进行研究。结果表明,连续方波电场作用下引起的液晶引流效应可以驱动液晶盒上板运动,方波电场频率为1 Hz、有效率为5%时驱动速度最大。液晶分子指向矢倾斜角的旋转范围对驱动效果影响较大,所施加电压对于倾斜角的旋转范围没明显影响,两板间的距离却影响很大。通过选择合适的驱动条件已成功得到90μm/s的高驱动速度。采用显微镜下直接观察液晶盒上板运动情况的方法进行试验验证,结果与理论计算结果定性上十分吻合,定量上试验结果偏小,最大差距出现在电场施加后的第三周期,主要原因是液晶盒制作时初始配向误差,可通过改变配向膜的种类及摩擦条件来改善。     

A caged progesterone analog alters intracellular Ca2+ and flagellar bending in human sperm

Progesterone is a physiological agonist for mammalian sperm, modulating its flagellar movement and facilitating the acrosome reaction. To study the initial action of progesterone, we developed a caged analog with a photosensitive group: nitrophenylethanediol, at position 20. Using this compound combined with stroboscopic illumination, we performed Ca(2)(+) imaging of human spermatozoa and analyzed the effects of progesterone on the intracellular Ca(2)(+) concentration ([Ca(2)(+)](i)) of beating flagella for the first time. We observed a transient [Ca(2)(+)](i) increase in the head and the flagellum upon photolysis of the caged progesterone and an increase in flagellar curvature. Detailed kinetic analysis revealed that progesterone elicits an increase in the [Ca(2)(+)](i) immediately in the flagellum (mid-piece and principal piece), thereafter in the head with a short time lag. This observation is different from the progesterone-induced Ca(2)(+) mobilization in mouse spermatozoa, where the Ca(2)(+) rise initiates at the base of the sperm head. Our finding is mostly consistent with the recent discovery that progesterone activates CatSper channels in human spermatozoa, but not in mouse spermatozoa.     

Sperm channel diversity and functional multiplicity

Ion channels are extraordinarily efficient machines that move ions in diversely controlled manners, allowing cells to rapidly exchange information with the outside world and with other cells. Communication is the currency of fertilization, as it is of most fundamental cell signaling events. Ion channels are deeply involved in the dialogue between sperm, its surroundings, and the egg. How sperm swim, find the egg and fertilize it depend on ion permeability changes modulated by environmental cues and components of the egg outer layer. Different ion channels distinctly localized in these tiny, amazing cells perform specific decoding functions that shape the sophisticated behavior of sperm. It is not surprising that certain sperm ion channels are turning out to be unique. New strategies to characterize sperm ion transport have opened exciting possibilities to dissect sperm-egg signaling and unveil novel contraception targets.     

Detection and activity of iodine-131 in brown algae collected in the Japanese coastal areas

Iodine-131 (physical half-life: 8.04 days) was detected in brown algae collected off the Japanese coast. Brown algae have been extensively used as bioindicators for radioiodine because of their ability to accumulate radionuclides in high concentration factors. The maximum measured specific activity of ¹³¹I in brown algae was 0.37 ± 0.010 Bq/kg-wet. Cesium-137 was also detected in all brown algal samples used in this study. There was no correlation between specific activities of ¹³¹I and ¹³⁷Cs in these seaweeds. The specific activity of ¹³⁷Cs ranged from 0.0034 ± 0.00075 to 0.090 ± 0.014 Bq/kg-wet. Low specific activity and minimal variability of ¹³⁷Cs in brown algae indicated that past nuclear weapon tests were the source of ¹³⁷Cs. Although nuclear power stations and nuclear fuel reprocessing plants are known to be pollution sources of ¹³¹I, there was no relationship between the sites where ¹³¹I was detected and the locations of nuclear power facilities. Most of the sites where ¹³¹I was detected were near big cities with large populations. Iodine-131 is frequently used in diagnostic and therapeutic nuclear medicine. On the basis of the results, we suggest that the likely pollution source of ¹³¹I, detected in brown seaweeds, is not nuclear power facilities, but nuclear medicine procedures.