995 research outputs found
Phase equilibria and glass transition in colloidal systems with short-ranged attractive interactions. Application to protein crystallization
We have studied a model of a complex fluid consisting of particles
interacting through a hard core and a short range attractive potential of both
Yukawa and square-well form. Using a hybrid method, including a self-consistent
and quite accurate approximation for the liquid integral equation in the case
of the Yukawa fluid, perturbation theory to evaluate the crystal free energies,
and mode-coupling theory of the glass transition, we determine both the
equilibrium phase diagram of the system and the lines of equilibrium between
the supercooled fluid and the glass phases. For these potentials, we study the
phase diagrams for different values of the potential range, the ratio of the
range of the interaction to the diameter of the repulsive core being the main
control parameter. Our arguments are relevant to a variety of systems, from
dense colloidal systems with depletion forces, through particle gels,
nano-particle aggregation, and globular protein crystallization.Comment: 20 pages, 10 figure
Normal and Lateral Casimir Forces between Deformed Plates
The Casimir force between macroscopic bodies depends strongly on their shape
and orientation. To study this geometry dependence in the case of two deformed
metal plates, we use a path integral quantization of the electromagnetic field
which properly treats the many-body nature of the interaction, going beyond the
commonly used pairwise summation (PWS) of van der Waals forces. For arbitrary
deformations we provide an analytical result for the deformation induced change
in Casimir energy, which is exact to second order in the deformation amplitude.
For the specific case of sinusoidally corrugated plates, we calculate both the
normal and the lateral Casimir forces. The deformation induced change in the
Casimir interaction of a flat and a corrugated plate shows an interesting
crossover as a function of the ratio of the mean platedistance H to the
corrugation length \lambda: For \lambda \ll H we find a slower decay \sim
H^{-4}, compared to the H^{-5} behavior predicted by PWS which we show to be
valid only for \lambda \gg H. The amplitude of the lateral force between two
corrugated plates which are out of registry is shown to have a maximum at an
optimal wavelength of \lambda \approx 2.5 H. With increasing H/\lambda \gtrsim
0.3 the PWS approach becomes a progressively worse description of the lateral
force due to many-body effects. These results may be of relevance for the
design and operation of novel microelectromechanical systems (MEMS) and other
nanoscale devices.Comment: 20 pages, 5 figure
A giant galaxy in the young Universe with a massive ring
In the local (redshift z~0) Universe, collisional ring galaxies make up only
~0.01% of galaxies and are formed by head-on galactic collisions that trigger
radially propagating density waves. These striking systems provide key
snapshots for dissecting galactic disks and are studied extensively in the
local Universe. However, not much is known about distant (z>0.1) collisional
rings. Here we present a detailed study of a ring galaxy at a look-back time of
10.8 Gyr (z=2.19). Compared with our Milky Way, this galaxy has a similar
stellar mass, but has a stellar half-light radius that is 1.5-2.2 times larger
and is forming stars 50 times faster. The large, diffuse stellar light outside
the star-forming ring, combined with a radial velocity on the ring and an
intruder galaxy nearby, provides evidence for this galaxy hosting a collisional
ring. If the ring is secularly evolved, the implied large bar in a giant disk
would be inconsistent with the current understanding of the earliest formation
of barred spirals. Contrary to previous predictions, this work suggests that
massive collisional rings were as rare 11 Gyr ago as they are today. Our
discovery offers a unique pathway for studying density waves in young galaxies,
as well as constraining the cosmic evolution of spiral disks and galaxy groups.Comment: Author's version for the main article (10 pages). The Supplementary
Information (22 pages) and a combined pdf are provided here
http://astronomy.swin.edu.au/~tyuan/paper Published version available online
http://dx.doi.org/10.1038/s41550-020-1102-
Resistance to autosomal dominant Alzheimer's disease in an APOE3 Christchurch homozygote: a case report.
We identified a PSEN1 (presenilin 1) mutation carrier from the world's largest autosomal dominant Alzheimer's disease kindred, who did not develop mild cognitive impairment until her seventies, three decades after the expected age of clinical onset. The individual had two copies of the APOE3 Christchurch (R136S) mutation, unusually high brain amyloid levels and limited tau and neurodegenerative measurements. Our findings have implications for the role of APOE in the pathogenesis, treatment and prevention of Alzheimer's disease
Gender Differences in Russian Colour Naming
In the present study we explored Russian colour naming in a web-based psycholinguistic experiment
(http://www.colournaming.com). Colour singletons representing the Munsell Color Solid (N=600 in total) were presented on a computer monitor and named using an unconstrained colour-naming method. Respondents were
Russian speakers (N=713). For gender-split equal-size samples (NF=333, NM=333) we estimated and compared (i)
location of centroids of 12 Russian basic colour terms (BCTs); (ii) the number of words in colour descriptors; (iii) occurrences of BCTs most frequent non-BCTs. We found a close correspondence between femalesâ and malesâ
BCT centroids. Among individual BCTs, the highest inter-gender agreement was for seryj âgreyâ and goluboj
âlight blueâ, while the lowest was for sinij âdark blueâ and krasnyj âredâ. Females revealed a significantly richer repertory of distinct colour descriptors, with great variety of monolexemic non-BCTs and âfancyâ colour names; in comparison, males offered relatively more BCTs or their compounds. Along with these measures, we gauged
denotata of most frequent CTs, reflected by linguistic segmentation of colour space, by employing a synthetic
observer trained by gender-specific responses. This psycholinguistic representation revealed femalesâ more
refined linguistic segmentation, compared to males, with higher linguistic density predominantly along the redgreen axis of colour space
Plasma Dynamics
Contains research objectives and summary of research on twenty-one projects split into three sections, with four sub-sections in the second section and reports on twelve research projects.National Science Foundation (Grant ENG75-06242)U.S. Energy Research and Development Administration (Contract E(11-1)-2766)U.S. Energy Research and Development Agency (Contract E(11-1)-3070)U.S. Energy Research and Development Administration (Contract E(11-1)-3070)Research Laboratory of Electronics, M.I.T. Industrial Fellowshi
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