Irradiation of Sperm Tails by Laser Microbeam

1. Sea-urchin and starfish sperm tails were irradiated at pre-selected points along the flagellum and at pre-selected phases of the beat cycle by means of a pulsed ruby laser microbeam. Multiple-exposure dark-field photomicrographs were taken immediately before and after irradiation. The flagellum usually appeared to be broken at the irradiated point. 2. The portion of a flagellum between the head and the irradiated point continued for at least a few beats if its length was at least 25% of the length of the tail, and stopped immediately if it was shorter. 3. Bends already established beyond the irradiated point continued to propagate to the tip of the flagellum. Their propagation velocity generally decreased, and there were usually changes in other bend parameters. 4. No new bends ever developed beyond the irradiated point. 5. Irradiation within a bent region often completely eliminated that region

Small flow rate can supply inwardly migrating shortest-period planets

The number of exoplanets found with periods as short as one day and less was surprising given how fast these planets had been expected to migrate into the star due to the tides raised on the star by planets at such close distances. It has been seen as improbable that we would find planets in such a small final fraction of their lives. The favored solution has been that the tidal dissipation is much weaker than expected, which would mean that the final infall would be a larger fraction of the planets' life. We find no reason to exclude the explanation that a small number of planets are continuously sent migrating inwards such that these planets indeed are in the last fraction of their lives. Following the observation that the distribution of medium planets disfavors tidal dissipation being significantly weaker than has been found from observations of binary stars, we now show that the numbers of planets in such a "flow" of excess planets migrating inwards is low enough that even depletion of the three-day pileup is a plausible source. Then the shortest period occurrence distribution would be shaped by planets continuously being sent into the star, which may explain the depletion of the pileup in the Kepler field relative to the solar neighborhood (Howard et al. 2012, hereafter H12). Because Kepler observes above the galactic plane, H12 suggested the Kepler field may include an older population of stars. The tidal dissipation strength in stars due to giant planets may be not greatly weaker than it is in binary stars.Comment: Four pages, four figures, submitted to Hot Planets Cold Stars conference (2012 November Garching, Germany

Identity and ethnicity in /t/ in Glasgow-Pakistani high-school girls

This paper presents an acoustic phonetic analysis of Glasgow Asian syllable-initial /t/, in speech data collected from Pakistani-Muslim girls in a Glasgow high school after a long-term participant observation into their shared and differing social practices. The results show differences in spectral energy and shape according to following phonetic segment, and to membership in two contrasting Communities of Practice, more conservative girls maintaining traditional cultural practices, and more rebellious girls whose behaviour challenges such norms. The findings demonstrate that ethnicity is integrally linked with locally-salient identity, and hence that fine phonetic variation which indexes ethnicity is in fact indexical of local ethnic identity

Gamma Limit for Transition Paths of Maximal Probability

Chemical reactions can be modelled via diffusion processes conditioned to make a transition between specified molecular configurations representing the state of the system before and after the chemical reaction. In particular the model of Brownian dynamics - gradient flow subject to additive noise - is frequently used. If the chemical reaction is specified to take place on a given time interval, then the most likely path taken by the system is a minimizer of the Onsager-Machlup functional. The Gamma limit of this functional is determined in the case where the temperature is small and the transition time scales as the inverse temperatur

Smooth matter and source size in microlensing simulations of gravitationally lensed quasars

Several gravitationally lensed quasars are observed with anomalous magnifications in pairs of images that straddle a critical curve. Simple theoretical arguments suggest that the magnification of these images should be approximately equivalent, whereas one image is observed to be significantly demagnified. Microlensing provides a possible explanation for this discrepancy. There are two key parameters when modelling this effect. The first, the fraction of smooth matter in the lens at the image positions, has been explored by Schechter and Wambsganss (2002). They have shown that the anomalous flux ratio observed in the lensed quasar MG 0414+0534 is a priori a factor of 5 more likely if the assumed smooth matter content in the lens model is increased from 0% to 93%. The second parameter, the size of the emission region, is explored in this paper, and shown to be more significant. We find that the broadening of the magnification probability distributions due to smooth matter content is washed out for source sizes that are predicted by standard models for quasars. We apply our model to the anomalous lensed quasar MG 0414+0534, and find a 95% upper limit of 2.62 x 10^(16) h^(-1/2) (M/Msun)^(1/2) cm on the radius of the I-band emission region. The smooth matter percentage in the lens is unconstrained.Comment: 6 pages, 6 figures. To be published in MNRA