73 research outputs found
Gigantic Maximum of Nanoscale Noncontact Friction
We report measurements of noncontact friction between surfaces of NbSe
and SrTiO, and a sharp Pt-Ir tip that is oscillated laterally by a quartz
tuning fork cantilever. At 4.2 K, the friction coefficients on both the
metallic and insulating materials show a giant maximum at the tip-surface
distance of several nanometers. The maximum is strongly correlated with an
increase in the spring constant of the cantilever. These features can be
understood phenomenologically by a distance-dependent relaxation mechanism with
distributed time scales.Comment: 5 pages, 4 figure
The emergence of expanding space-time in a novel large- limit of the Lorentzian type IIB matrix model
The Lorentzian type IIB matrix model is a promising candidate for a
non-perturbative formulation of superstring theory. However, it was found
recently that a Euclidean space-time appears in the conventional large-
limit. In this work, we add a Lorentz invariant mass term to the original model
and consider a limit, in which the coefficient of the mass term vanishes at
large . By performing complex Langevin simulations to overcome the sign
problem, we observe the emergence of expanding space-time with the Lorentzian
signature.Comment: 10 pages, 8 figures, Contribution to the 39th International Symposium
on Lattice Field theory (LATTICE2022), 8th-13th August, 2022, Bonn, Germany;
(v2) reference adde
Dynamics of Scalar field in a Brane World
We study the dynamics of a scalar field in the brane cosmology. We assume
that a scalar field is confined in our 4-dimensional world. As for the
potential of the scalar field, we discuss three typical models: (1) a power-law
potential, (2) an inverse-power-law potential, and (3) an exponential
potential. We show that the behavior of the scalar field is very different from
a conventional cosmology when the energy density square term is dominated.Comment: 15pages, 8figures, submitted to Physical Review
Chemical and Photometric Evolution of Extended Ultraviolet Disks: Optical Spectroscopy of M83 (NGC5236) and NGC4625
We present the results from the analysis of optical spectra of 31
Halpha-selected regions in the extended UV (XUV) disks of M83 (NGC5236) and
NGC4625 recently discovered by GALEX. The spectra were obtained using IMACS at
Las Campanas Observatory 6.5m Magellan I telescope and COSMIC at the Palomar
200-inch telescope, respectively for M83 and NGC4625. The line ratios measured
indicate nebular oxygen abundances (derived from the R23 parameter) of the
order of Zsun/5-Zsun/10. For most emission-line regions analyzed the line
fluxes and ratios measured are best reproduced by models of photoionization by
single stars with masses in the range 20-40 Msun and oxygen abundances
comparable to those derived from the R23 parameter. We find indications for a
relatively high N/O abundance ratio in the XUV disk of M83. Although the
metallicities derived imply that these are not the first stars formed in the
XUV disks, such a level of enrichment could be reached in young spiral disks
only 1 Gyr after these first stars would have formed. The amount of gas in the
XUV disks allow maintaining the current level of star formation for at least a
few Gyr.Comment: 52 pages, 8 tables, 7 figures, accepted for publication in Ap
Heritable Differences in Schooling Behavior among Threespine Stickleback Populations Revealed by a Novel Assay
Identifying the proximate and ultimate mechanisms of social behavior remains a major goal of behavioral biology. In particular, the complex social interactions mediating schooling behavior have long fascinated biologists, leading to theoretical and empirical investigations that have focused on schooling as a group-level phenomenon. However, methods to examine the behavior of individual fish within a school are needed in order to investigate the mechanisms that underlie both the performance and the evolution of schooling behavior. We have developed a technique to quantify the schooling behavior of an individual in standardized but easily manipulated social circumstances. Using our model school assay, we show that threespine sticklebacks (Gasterosteus aculeatus) from alternative habitats differ in behavior when tested in identical social circumstances. Not only do marine sticklebacks show increased association with the model school relative to freshwater benthic sticklebacks, they also display a greater degree of parallel swimming with the models. Taken together, these data indicate that marine sticklebacks exhibit a stronger tendency to school than benthic sticklebacks. We demonstrate that these population-level differences in schooling tendency are heritable and are shared by individuals within a population even when they have experienced mixed-population housing conditions. Finally, we begin to explore the stimuli that elicit schooling behavior in these populations. Our data suggest that the difference in schooling tendency between marine and benthic sticklebacks is accompanied by differential preferences for social vs. non-social and moving vs. stationary shelter options. Our study thus provides novel insights into the evolution of schooling behavior, as well as a new experimental approach to investigate the genetic and neural mechanisms that underlie this complex social behavior
Maze Solving Using Fatty Acid Chemistry
This
study demonstrates that the Marangoni flow in a channel network
can solve maze problems such as exploring and visualizing the shortest
path and finding all possible solutions in a parallel fashion. The
Marangoni flow is generated by the pH gradient in a maze filled with
an alkaline solution of a fatty acid by introducing a hydrogel block
soaked with an acid at the exit. The pH gradient changes the protonation
rate of fatty acid molecules, which translates into the surface tension
gradient at the liquidâair interface through the maze. Fluid
flow maintained by the surface tension gradient (Marangoni flow) can
drag water-soluble dye particles toward low pH (exit) at the liquidâair
interface. Dye particles placed at the entrance of the maze dissolve
during this motion, thus exhibiting and finding the shortest path
and all possible paths in a maze
An autopsy study of combined pulmonary fibrosis and emphysema: correlations among clinical, radiological, and pathological features
Possible plasma dynamics in nighttime magnetosphere associated with Pi 2 onset as observed from dip-equator (extended abstract)
Possible plasma dynamics in nighttime magnetosphere associated with Pi 2 onset as observed from dip-equator (extended abstract)
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