Radar measurement of the upper atmosphere

In the last two decades large radars have proved to be powerful instruments for the measurement of the properties of the upper atmosphere. These radars were used initially to measure properties of the ionosphere by the Thomson scattering technique at heights above 100 kilometers. Careful interpretation of the power and spectrum of radar echoes yielded data on electron and ion densities and temperatures as well as on bulk motion of the ionospheric plasma, all as functions of height and time. More recent developments have made it possible to measure wind speeds and the structure of turbulence in the stratosphere and mesosphere at altitudes below 100 kilometers.     

关于信息度量问题的思考

为克服Shannon熵的局限性,修改了Shannon熵的公理,用公理化的方法,推导出具有有限分布列的离散型随机变量的信息量系。并且将它推广到任意具有可数无限分布列的离散型随机变量和随机向量。证明了信息量系的最大信息量定理,可加性定理,广义可加性定理、互信息定理、独立性定理等性质。对信息量系中参数值的选取提出建议。     

Borehole measurement of the newtonian gravitational constant

It has been reported that the geophysically determined Newtonian gravitational constant is consistently larger than the laboratory value by 1 to 2% on the basis of gravity measurements in Australian mines. This discrepancy may have strong implications for the physics of gravitation. To test whether similar results can be observed in a different geological environment, gravity measurements in a Michigan borehole have been examined. Although these results cannot be taken as conclusive, owing to the large uncertainties involved in mass determination on a geophysical scale, these measurements are generally consistent with those of the Australian experiment.     

一种抗性淀粉测定方法的改进

通过淀粉水解动力学分析,比较了防腐剂和抗生素抑制淀粉消化液发酵的效果,以改进Goni等分析抗性淀粉的方法。结果表明,抗生素和防腐剂均能有效抑制消化液中微生物的生长,但防腐剂的使用需要无菌条件,而且对淀粉酶活性的抑制比抗生素强,因此使用抗生素是比较好的选择。为加快淀粉水解速率,降低抗生素对淀粉酶的抑制作用,淀粉酶用量从120 mg增至160 mg,但对水解速率较低的籼稻品种南京11未有改善,因此仍选择120 mg的酶量。这些结果为建立稳定可靠的抗性淀粉测定方法及筛选高抗性淀粉的水稻品种奠定了良好的技术基础。     

Gravity: first measurement on the lunar surface

The gravity at the landing site of the first lunar-landing mission has been determined to be 162,821.680 milligals from data telemetered to earth by the lunar module on the lunar surface. The gravity was measured with a pulsed integrating pendulous accelerometer. These measurements were used to compute the gravity anomaly and radius at the landing site.     

Advances in measurement science

Year after year, physicists measure various quantities with increasing accuracy and see various objects in increasing detail. These advances are vital, because science's understanding of the physical world is necessarily limited by the accuracy with which science can measure that world. The Instrument and Measurement Science Topical Group of the American Physical Society sponsored several symposia at the recent APS March meeting in New Orleans that discussed recent advances in measurement and observation.     

The quantum measurement problem

Despite the spectacular success of quantum mechanics (QM) over the last 80 years in explaining phenomena observed at the atomic and subatomic level, the conceptual status of the theory is still a topic of lively controversy. Most of the discussion centers around two famous paradoxes (or, as some would have it, pseudoparadoxes) associated, respectively, with the names of Einstein, Podolsky, and Rosen (EPR) and with Schrodinger's cat. In this Viewpoint, I will concentrate on the paradox of Schrodinger's cat or, as it is often known (to my mind somewhat misleadingly), the quantum measurement paradox.     

酚氧化酶活力测定方法中关于测定时间的研究

以克氏原螯虾(Procambarus clarkii)血清酚氧化酶为材料,采用Ashida的分光光度法测定了不同活力酚氧化酶与L-DOPA在60 min内每2 min生成物的吸光度以及计算了不同时间的酚氧化酶活力.结果显示,当测定时间为60 min时,随着酚氧化酶活力升高,吸光度与测定时间的直线相关系数逐渐降低,反映了测定的酚氧化酶活力准确性也越差,与其他已报道的南美白对虾(Penaeus vannamei)、中国对虾(Penaeus chinesis)和中华绒螯蟹(Eriocheir sinensis)等虾蟹类及昆虫(Pieris rapae)的酚氧化酶活力测定结果相似.与6 min时的相关系数和酶活力计算结果相比,当测定时间长于12 min时相关系数显著变小(P﹤0.05),而短于6 min时也有变小的趋势;当测定时间长于10 min时酚氧化酶活力计算结果显著变小(P﹤0.05).通过不同测定时长的相关系数以及酚氧化酶活力计算结果的差异性比较,得出酚氧化酶活力测定最为准确的测定时长(t)为6 min≤t＜10 min,最佳时长为6 min.     

Atom interferometer measurement of the newtonian constant of gravity

We measured the Newtonian constant of gravity, G, using a gravity gradiometer based on atom interferometry. The gradiometer measures the differential acceleration of two samples of laser-cooled Cs atoms. The change in gravitational field along one dimension is measured when a well-characterized Pb mass is displaced. Here, we report a value of G = 6.693 x 10(-11) cubic meters per kilogram second squared, with a standard error of the mean of +/-0.027 x 10(-11) and a systematic error of +/-0.021 x 10(-11) cubic meters per kilogram second squared. The possibility that unknown systematic errors still exist in traditional measurements makes it important to measure G with independent methods.     

A spectroscopic measurement of the coronal density of procyon

One of the open key issues in the astrophysics of stellar coronae is the determination of their spatial structure and density. From almost all previous measurements, one can infer merely the presence of a corona, which for the most energetic stellar coronae may exceed the solar x-ray output by as much as five orders of magnitude, but no information can be obtained on the densities and hence volumes and sizes of the hot x-ray emitting material. A direct spectroscopic measurement of the coronal density was obtained for the star Procyon with the spectrometer on board the Extreme Ultraviolet Explorer satellite; the ratio of two Fe XIV lines at 211.32 and 264.79 angstroms was used to determine a density of approximately 4 x 10(9) to 7 x 10(9) electrons per cubic centimeter, which is a factor of 2 to 3 higher than typical solar active region densities. From this value, we estimate that approximately 6 percent of the stellar surface is covered with approximately 7 x 10(4) coronal loops.     

Pressure measurement made by the utilization of ruby sharp-line luminescence

A rapid, convenient technique for precision pressure measurement in the diamond-anvil high-pressure cell, which makes use of the sharp-line (R-line) luminescence of ruby, has been developed. The observed shift is -0.77 +/-0.03 reciprocal centimeters per kilobar for R(1) and -0.84+/- 0.03 reciprocal centimeters per kilobar for R(2) to lower energy and is approximately linear in the range studied (to 22 kilobars). Line-broadening has been observed in some instances and has been tentatively identified with nonhydrostatic conditions surrounding the ruby sample.     

International basis for uniform measurement

The influence and importance of the International Bureau have never been greater than they are today and there seems little doubt that its position will be enhanced in the future. The rapid development of science and technological industry during recent decades has placed heavy demands on fundamental metrology to keep ahead of immediate needs. This trend is likely to increase. Other organizations also have an important role to play in measurement and its ultimate application. However, if the International Bureau conserves its competence, the fact that it has always envisaged its role as that of providing leadership in the development of an international scientific consensus rather than developing and imposing its own ideas, combined with the authority that is conferred only by international treaty, will assure its position as the international focus for world measurement. Inevitably this will call for expansion of the Bureau's activities. Not all demands made on it will be legitimate or wise. It will be the responsibility of the International Committee to keep the situation under continuous study and bring imaginative yet prudent recommendations to the Conference.     

Direct measurement of light waves

The electromagnetic field of visible light performs approximately 10(15) oscillations per second. Although many instruments are sensitive to the amplitude and frequency (or wavelength) of these oscillations, they cannot access the light field itself. We directly observed how the field built up and disappeared in a short, few-cycle pulse of visible laser light by probing the variation of the field strength with a 250-attosecond electron burst. Our apparatus allows complete characterization of few-cycle waves of visible, ultraviolet, and/or infrared light, thereby providing the possibility for controlled and reproducible synthesis of ultrabroadband light waveforms.     

Radio method for the precise measurement of the rotation period of the Earth

Radio interferometry with independent high-precision clocks, without a high-frequency communication channel between the stations, is now a possibility. It allows the stations to be as far apart as the earth can accommodate. This then makes the radio band from 10- to 60-centimeters wavelength the best frequency range for high-precision angular measurements, since the variability of the atmosphere is less disturbing there than in the optical band.