Results 1 - 10 of 36146
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[en] We present a qualitative study designed to examine how students construct an understanding of the human eye and vision from their knowledge of light and optics. As would be expected, vast differences are shown to exist between pre- and post-instruction students in terms of not only resource use, but also willingness to transfer their existing knowledge. However, we have found that appropriate scaffolding can facilitate resource activation and guide students to construct an understanding of vision and vision defects. (paper)
[en] Highlights: • A triboelectric biosensor is developed for the self-powered detection of thrombin. • The selective recognition of thrombin is achieved by using aptamer. • The change in the electrical output upon sensing is resulted from the changes in the surface potential. • The triboelectric biosensor achieves a high detection sensitivity of 0.41 nM. • Thrombin detection is also directly demonstrated via an array of LED lights. An aptamer-based triboelectric biosensor is developed for a highly specific, label-free and self-powered detection of thrombin. For the first time, intermolecular recognition interactions are used to develop a selective nanosensor based on triboelectric effect. Positively charged Au nanoparticles (Au NPs+) with large difference in triboelectric polarity and work function are assembled onto Al film to increase the electrical output of triboelectric nanogenerators (TENG). Modification of anti-thrombin aptamers on the Au NPs+-assembled TENG affords the triboelectric nanosensor highly selective toward thrombin, even in clinical samples because of specific binding affinity between aptamers and thrombin unlike random DNA-modified TENGs with undetectable response. A 0.41 nM limit of detection is achieved, which is directly demonstrated by the number of commercial LED lights without any supporting equipment such as power source and electrometer. Our study demonstrates an innovative and unique approach toward the self-powered and label-free detection of thrombin for rapid and simple in-field analysis.
[en] Following a discussion of two recent papers by Schmidt (1973, 1975), it is concluded that for the large amplitude, longer period Cepheids (log P greater than about 1.1), the small colour excesses derived from the six-colour photometry (traditional method or Parsons method) are to be preferred to the large colour excesses derived from the GAMMA-index photometry (Kraft's scale). (Auth.)
[en] Recent studies have shown that an asymmetric Bessel beam, similar to a conventional non-diverging Bessel beam; recovers their original intensity profile after encountering an obstruction. Here, we investigate the ability of an asymmetric Bessel beam to recover their original intensity profile when it is perturbed by an obstruction, and additionally drastically perturbed by a pattern of light generated by an annular obstruction. We believe that their intriguing properties have not been fully studied. A better understanding of their properties can help to make use of them appropriately in a variety of potential applications. Our investigations reveal that the dynamics of the reconstruction is affected by the asymmetry degree of the beam.
[en] Mutual events between natural satellites include mutual occultation and mutual eclipse. Mutual eclipse is another kind of mutual occultation as viewed from the center of the Sun instead of the Earth. Two mutual eclipses of J2 Europa by J1 Io (2009 Aug. 28 and Sept. 12) were observed at Yunnan Observatory during the PHEMU09 international campaign. We will calculate the astrometric data of these Galilean satellites by analyzing and fitting the light curves we obtained. The limb-darkening was considered during modeling the light intensity of eclipsed satellites in the penumbra zone, by taking the Lommel-Seeliger scattering law into account. Several dynamical quantities, such as the relative coordinates of the eclipsing satellite from the eclipsed one Δαcosδ and Δδ, impact parameter and mid-time corresponding to the impact parameter and the deviations O - C of observed Δαcosδ and Δδ relative to ephemerides, were obtained for each event respectively. (research papers)
[en] Limits on the optical luminosities of eight radio pulsars in the wavelength range lambda = 3500--6000 A are obtained from the results of their investigation on the six-meter telescope of the Special Astrophysical Observatory, USSR Academy of Sciences. The corresponding limits on the stellar magnitudes of these pulsars (under the assumption that the optical emission spectra of these pulsars are similar to the spectrum of the pulsar in the Crab Nebula) are m/sub B/roughly-equal25--26/sup m/