2,287 research outputs found
Venus
This is a film review of Venus (2022), directed by Jaume Balagueró
The Convert
This is a film review of The Convert (2023), directed by Lee Tamahori
223 Wick
This is a film review of 223 Wick (2022), directed by Sergio Myers
Werckmeister Harmonies
This is a film review of the 4K restoration of Werckmeister Harmonies (2000), directed by Béla Tarr and Ágnes Hranitzky
Lost Ladies
This is a film review of Lost Ladies (2023), directed by Kiran Rao
Reason (Vivek)
This is a film review of Reason (Vivek) (2018), directed by Anand Patwardhan
Ad Vitam
This is a film review of Ad Vitam (2018), directed by Thomas Calley
Kill
This is a film review of Kill (2023) directed by Nikhil Nagesh Bhatt
Theoretical model for the images formed by a spherical particle in a coherent imaging system: comparison
A simple theoretical model is presented that allows calculation of the image produced by a spherical absorbing particle illuminated by monochromatic, coherent laser light. Results presented in this paper are restricted to a singe-lens imaging system, although generalization to more complex imaging system configurations would be straightfoward. The method uses classic Lorenz-Mie scattering theory to obtain the electromagnetic field external to an absorbing spherical particle and a Fourier optics approach to calculate the intensities in the image plane. Experimental results evaluating focus characteristics are examined for 50 um diameter water droplets using an N2 laser imaging system in conjunction with a digital image processor, and the experimental images are compared with a digital image processor, and the experimental images are compared to the results of the theoretical model. Comparative focus criteria results are particularly useful in aerosol science research involving dynamic particle size measuremetns in which criteria for focus and depth of field must be established
Tidally-Triggered Star Formation in Close Pairs of Galaxies
We analyze new optical spectra of a sample of 502 galaxies in close pairs and
n-tuples, separated by <= 50/h kpc. We extracted the sample objectively from
the CfA2 redshift survey, without regard to the surroundings of the tight
systems. We probe the relationship between star formation and the dynamics of
the systems of galaxies. The equivalent widths of H\alpha (EW(H\alpha) and
other emission lines anti-correlate strongly with pair spatial separation
(\Delta D) and velocity separation. We use the measured EW(H\alpha) and the
starburst models of Leitherer et al. to estimate the time since the most recent
burst of star for- mation began for each galaxy. In the absence of a large
contribution from an old stellar population to the continuum around H\alpha,
the observed \Delta D -- EW(H\alpha) correlation signifies that starbursts with
larger separations on the sky are, on average, older. By matching the dynamical
timescale to the burst timescale, we show that the data support a simple
picture in which a close pass initiates a starburst; EW(H\alpha) decreases with
time as the pair separation increases, accounting for the anti-correlation.
This picture leads to a method for measuring the duration and the initial mass
function of interaction-induced starbursts: our data are compatible with the
starburst and orbit models in many respects, as long as the starburst lasts
longer than \sim10^8 years and the delay between the close pass and the
initiation of the starburst is less than a few \times 10^7 years. If there is
no large contribution from an old stellar population to the continuum around
H\alpha the Miller-Scalo and cutoff (M <= 30 M_\sun) Salpeter initial mass
functions fit the data much better than a standard Salpeter IMF. (Abridged.)Comment: 43 pages, 22 figures, to appear in the ApJ; we correct an error which
had minor effects on numerical values in the pape
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