1,132 research outputs found

    Impact of cloud-borne aerosol representation on aerosol direct and indirect effects

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    International audienceAerosol particles attached to cloud droplets are much more likely to be removed from the atmosphere and are much less efficient at scattering sunlight than if unattached. Models used to estimate direct and indirect effects of aerosols employ a variety of representations of such cloud-borne particles. Here we use a global aerosol model with a relatively complete treatment of cloud-borne particles to estimate the sensitivity of simulated aerosol, cloud and radiation fields to various approximations to the representation of cloud-borne particles. We find that neglecting transport of cloud-borne particles introduces little error, but that diagnosing cloud-borne particles produces global mean biases of 20% and local errors of up to 40% for aerosol, droplet number, and direct and indirect radiative forcing. Aerosol number, aerosol optical depth and droplet number are significantly underestimated in regions and seasons where and when wet removal is primarily by stratiform rather than convective clouds (polar regions during winter), but direct and indirect effects are less biased because of the limited sunlight there and then. A treatment that predicts the total mass concentration of cloud-borne particles for each mode yields smaller errors and runs 20% faster than the complete treatment. The errors are much smaller than current estimates of uncertainty in direct and indirect effects of aerosols, which suggests that the treatment of cloud-borne aerosol is not a significant source of uncertainty in estimates of direct and indirect effects

    Numerical modelling of liquid droplet dynamics in microgravity

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    Microgravity provides ideal experimental conditions for studying highly reactive and under-cooled materials where there is no contact between the sample and the other experimental apparatus. The non-contact conditions allow material properties to be measured from the oscillating liquid droplet response to perturbations. This work investigates the impact of a strong magnetic field on these measurement processes for weakly viscous, electrically conducting droplets. We present numerical results using an axisymmetric model that employs the pseudo-spectral collocation method and a recently developed 3D model. Both numerical models have been developed to solve the equations describing the coupled electromagnetic and fluid flow processes. The models represent the changing surface shape that results from the interaction between forces inside the droplet and the surface tension imposed boundary conditions. The models are used to examine the liquid droplet dynamics in a strong DC magnetic field. In each case the surface shape is decomposed into a superposition of spherical harmonic modes. The oscillation of the individual mode coefficients is then analysed to determine the oscillation frequencies and damping rates that are then compared to the low amplitude solutions predicted by the published analytical asymptotic theory

    Retinal synaptic arrays: Continuing development in the adult goldfish

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    We report a light- and electron-microscopic examination of the inner plexiform layer of the central retina of young (c. 1 year) and old (3–4 year) goldfish. There were no new neurons added to this region during the growth period. Nonetheless, there were substantially more synapses (per cell, per mm 2 , or per degree 2 ) in the older retinas. This result is discussed in the contexts of retinal function and neural development.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50006/1/901850210_ftp.pd

    Liquid Droplet Dynamics in Gravity Compensating High Magnetic Field

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    Numerical models are used to investigate behavior of liquid droplets suspended in high DC magnetic fields of various configurations providing microgravity-like conditions. Using a DC field it is possible to create conditions with laminar viscosity and heat transfer to measure viscosity, surface tension, electrical and thermal conductivities, and heat capacity of a liquid sample. The oscillations in a high DC magnetic field are quite different for an electrically conducting droplet, like liquid silicon or metal. The droplet behavior in a high magnetic field is the subject of investigation in this paper. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case

    Birth of olfactory neurons: Lifelong neurogenesis

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24850/1/0000277.pd

    A comment on the "glissade"

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33915/1/0000180.pd

    Automated retinotectology

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    The retinotectal projection has been the principal battleground, since the 1930s, for the experimental investigation of the factors determining specific neural connections. Since the late 1950s, the electrophysiological determination of the retinotectal map has been the dominant experimental method. Many of the conclusions derived with this method have been questioned (by other investigators using the same method), and some of these disputes remain unresolved even today. Recently, David Northmore and his associates have developed two automated methods for assessing retinotectal function which are described below. In different ways, these methods correct some of the deficiencies of the old method.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25889/1/0000452.pd

    The time course of saccadic eye movements in goldfish

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    Spontaneous saccadic eye movements (2-25[deg]) made by goldfish have an initial brief acceleration, followed by a more prolonged deceleration, and occasionally a terminal phase during which the velocity reverses sign following overshoot of the final position. Overshoots by the individual eyes are independent events. The duration and the maximum velocity increase monotonically with the size of the saccade. Goldfish saccades have greater durations and slightly smaller maximum velocities than mammalian saccades of similar size.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22121/1/0000548.pd
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