3,280 research outputs found
Preparatory studies of zero-g cloud drop coalescence experiment
Experiments to be performed in a weightless environment in order to study collision and coalescence processes of cloud droplets are described. Rain formation in warm clouds, formation of larger cloud drops, ice and water collision processes, and precipitation in supercooled clouds are among the topics covered
Evaluation of data obtained from atmospheric laser Doppler velocimeter
The Doppler lidar velocimeter produces a variety of kinds of data. Besides the line of sight velocity components, there are the reflected amplitudes and the Doppler widths. Computer graphics software for displaying these data was produced. Different methods of presentation are needed for the various items. A picture was produced as pictures are often the best way to gain understanding. The individual lidar scans form a crosshatch pattern. Thus one-dimensional measurements fit together to form a two-dimensional whole. A pair of velocity measurements at a point combine to form a wind measurement with direction and magnitude. This gives a forest of wind vectors. The goal is to find a recognizable pattern to these trees. Often it is necessary to show only part of the information. That is, show only the wind direction not its magnitude or reduce the wind to streamlines of air flow. In other cases data are reduced to contour plots. Just enough contour lines are included to show the picture described
Microglia Tweak Retinogeniculate Pathways during Visual Circuit Refinement
Cheadle et al. reveal that microglia expressing TWEAK facilitate synapse elimination through a novel, non-phagocytic mechanism in the retinogeniculate pathway during visual circuit development. This mechanism is experience-dependent and occurs through the local binding of TWEAK to postsynaptic Fn14
The Ups and Downs of Firing Rate Homeostasis
Torrado Pacheco et al. demonstrate that downward firing rate homeostasis occurs when cellular activity levels increase beyond baseline, but only during sleep-dense periods. In contrast, Hebbian-facilitated changes in firing rate occur independently of sleep and wake states
The Transition State in a Noisy Environment
Transition State Theory overestimates reaction rates in solution because
conventional dividing surfaces between reagents and products are crossed many
times by the same reactive trajectory. We describe a recipe for constructing a
time-dependent dividing surface free of such recrossings in the presence of
noise. The no-recrossing limit of Transition State Theory thus becomes
generally available for the description of reactions in a fluctuating
environment
A Suzaku, NuSTAR, and XMM-Newton view on variable absorption and relativistic reflection in NGC 4151
We disentangle X-ray disk reflection from complex line-of-sight absorption in
the nearby Seyfert NGC 4151, using a suite of Suzaku, NuSTAR, and XMM-Newton
observations. Extending upon earlier published work, we pursue a physically
motivated model using the latest angle-resolved version of the lamp-post
geometry reflection model relxillCp_lp together with a Comptonization
continuum. We use the long-look simultaneous Suzaku/NuSTAR observation to
develop a baseline model wherein we model reflected emission as a combination
of lamp-post components at the heights of 1.2 and 15.0 gravitational radii. We
argue for a vertically extended corona as opposed to two compact and distinct
primary sources. We find two neutral absorbers (one full-covering and one
partial-covering), an ionized absorber (), and a highly-ionized
ultra-fast outflow, which have all been reported previously. All analyzed
spectra are well described by this baseline model. The bulk of the spectral
variability between 1 keV and 6 keV can be accounted for by changes in the
column density of both neutral absorbers, which appear to be degenerate and
inversely correlated with the variable hard continuum component flux. We track
variability in absorption on both short (2 d) and long (1 yr) timescales;
the observed evolution is either consistent with changes in the absorber
structure (clumpy absorber at distances ranging from the broad line region
(BLR) to the inner torus or a dusty radiatively driven wind) or a geometrically
stable neutral absorber that becomes increasingly ionized at a rising flux
level. The soft X-rays below 1 keV are dominated by photoionized emission from
extended gas that may act as a warm mirror for the nuclear radiation.Comment: 21 pages, 19 figures, 8 tables, accepted for publication by A&
Half a Century of Supreme Court Clean Air Act Interpretation: Purposivism, Textualism, Dynamism, and Activism
This Article addresses the history of the Supreme Court’s interpretation of the Clean Air Act, which now goes back almost half a century. Many scholars have argued that the Court has shifted from an approach to statutory interpretation that relied heavily on purposivism—the custom of giving statutory goals weight in interpreting statutes—toward one that relies more heavily on textualism during this period. At the same time, proponents of dynamic statutory interpretation have argued that courts, in many cases, do not so much excavate a statute’s meaning as adapt a statute to contemporary circumstances
- …