1,806 research outputs found
Constraining Scatter in the Stellar Mass--Halo Mass Relation for Haloes Less Massive than the Milky Way
Most galaxies are hosted by massive, invisible dark matter haloes, yet little
is known about the scatter in the stellar mass--halo mass relation for galaxies
with host halo masses . Using mock catalogues based
on dark matter simulations, we find that two observable signatures are
sensitive to scatter in the stellar mass--halo mass relation even at these mass
scales; i.e., conditional stellar mass functions and velocity distribution
functions for neighbouring galaxies. We compute these observables for 179,373
galaxies in the Sloan Digital Sky Survey (SDSS) with stellar masses and redshifts 0.01 0.307. We then compare to mock
observations generated from the dark matter
simulation for stellar mass--halo mass scatters ranging from 0 to 0.6 dex. The
observed results are consistent with simulated results for most values of
scatter (0.6 dex), and SDSS statistics are insufficient to provide firm
constraints. However, this method could provide much tighter constraints on
stellar mass--halo mass scatter in the future if applied to larger data sets,
especially the anticipated Dark Energy Spectroscopic Instrument Bright Galaxy
Survey. Constraining the value of scatter could have important implications for
galaxy formation and evolution.Comment: 11 pages, 1 table, 9 main body figures, 9 appendix figure
Water-Driven Micromotors
We demonstrate the first example of a water-driven bubble-propelled micromotor that eliminates the requirement for the common hydrogen peroxide fuel. The new water-driven Janus micromotor is composed of a partially coated Al–Ga binary alloy microsphere prepared via microcontact mixing of aluminum microparticles and liquid gallium. The ejection of hydrogen bubbles from the exposed Al–Ga alloy hemisphere side, upon its contact with water, provides a powerful directional propulsion thrust. Such spontaneous generation of hydrogen bubbles reflects the rapid reaction between the aluminum alloy and water. The resulting water-driven spherical motors can move at remarkable speeds of 3 mm s^(–1) (i.e., 150 body length s^(–1)), while exerting large forces exceeding 500 pN. Factors influencing the efficiency of the aluminum–water reaction and the resulting propulsion behavior and motor lifetime, including the ionic strength and environmental pH, are investigated. The resulting water-propelled Al–Ga/Ti motors move efficiently in different biological media (e.g., human serum) and hold considerable promise for diverse biomedical or industrial applications
Catalytic Iridium-Based Janus Micromotors Powered by Ultralow Levels of Chemical Fuels
We describe catalytic micromotors powered by remarkably low concentrations of chemical fuel, down to the 0.0000001% level. These Janus micromotors rely on an iridium hemispheric layer for the catalytic decomposition of hydrazine in connection to SiO_2 spherical particles. The micromotors are self-propelled at a very high speed (of ∼20 body lengths s^(–1)) in a 0.001% hydrazine solution due to osmotic effects. Such a low fuel concentration represents a 10 000-fold decrease in the level required for common catalytic nanomotors. The attractive propulsion performance, efficient catalytic energy-harvesting, environmentally triggered swarming behavior, and magnetic control of the new Janus micromotors hold considerable promise for diverse practical applications
Highly Efficient Light-Driven TiO_2–Au Janus Micromotors
A highly efficient light-driven photocatalytic TiO_2–Au Janus micromotor with wireless steering and velocity control is described. Unlike chemically propelled micromotors which commonly require the addition of surfactants or toxic chemical fuels, the fuel-free Janus micromotor (diameter ∼1.0 μm) can be powered in pure water under an extremely low ultraviolet light intensity (2.5 × 10^(–3) W/cm^2), and with 40 × 10^(–3) W/cm^2, they can reach a high speed of 25 body length/s, which is comparable to common Pt-based chemically induced self-electrophoretic Janus micromotors. The photocatalytic propulsion can be switched on and off by incident light modulation. In addition, the speed of the photocatalytic TiO_2–Au Janus micromotor can be accelerated by increasing the light intensity or by adding low concentrations of chemical fuel H_2O_2 (i.e., 0.1%). The attractive fuel-free propulsion performance, fast movement triggering response, low light energy requirement, and precise motion control of the TiO_2–Au Janus photocatalytic micromotor hold considerable promise for diverse practical applications
PYR/PYL/RCAR abscisic acid receptors regulate K<sup>+</sup> and Cl<sup>-</sup> channels through reactive oxygen species-mediated activation of Ca<sup>2+</sup> channels at the plasma membrane of intact Arabidopsis guard cells.
The discovery of the START family of abscisic acid (ABA) receptors places these proteins at the front of a protein kinase/phosphatase signal cascade that promotes stomatal closure. The connection of these receptors to Ca<sup>2+</sup> signals evoked by ABA has proven more difficult to resolve, although it has been implicated by studies of the pyrbactin-insensitive <i>pyr1/pyl1/pyl2/pyl4</i> quadruple mutant. One difficulty is that flux through plasma membrane Ca<sup>2+</sup> channels and Ca<sup>2+</sup> release from endomembrane stores coordinately elevate cytosolic free Ca<sup>2+</sup> concentration ([Ca<sup>2+</sup>]<sub>i</sub>) in guard cells, and both processes are facilitated by ABA. Here, we describe a method for recording Ca<sup>2+</sup> channels at the plasma membrane of intact guard cells of Arabidopsis (Arabidopsis thaliana). We have used this method to resolve the loss of ABA-evoked Ca<sup>2+</sup> channel activity at the plasma membrane in the <i>pyr1/pyl1/pyl2/pyl4</i> mutant and show the consequent suppression of [Ca<sup>2+</sup>]<sub>i</sub> increases in vivo. The basal activity of Ca<sup>2+</sup> channels was not affected in the mutant; raising the concentration of Ca<sup>2+</sup> outside was sufficient to promote Ca<sup>2+</sup> entry, to inactivate current carried by inward-rectifying K<sup>+</sup> channels and to activate current carried by the anion channels, both of which are sensitive to [Ca<sup>2+</sup>]<sub>i</sub> elevations. However, the ABA-dependent increase in reactive oxygen species (ROS) was impaired. Adding the ROS hydrogen peroxide was sufficient to activate the Ca<sup>2+</sup> channels and trigger stomatal closure in the mutant. These results offer direct evidence of PYR/PYL/RCAR receptor coupling to the activation by ABA of plasma membrane Ca<sup>2+</sup> channels through ROS, thus affecting [Ca<sup>2+</sup>]<sub>i</sub> and its regulation of stomatal closure
Water-Driven Micromotors
We demonstrate the first example of a water-driven bubble-propelled micromotor that eliminates the requirement for the common hydrogen peroxide fuel. The new water-driven Janus micromotor is composed of a partially coated Al–Ga binary alloy microsphere prepared via microcontact mixing of aluminum microparticles and liquid gallium. The ejection of hydrogen bubbles from the exposed Al–Ga alloy hemisphere side, upon its contact with water, provides a powerful directional propulsion thrust. Such spontaneous generation of hydrogen bubbles reflects the rapid reaction between the aluminum alloy and water. The resulting water-driven spherical motors can move at remarkable speeds of 3 mm s^(–1) (i.e., 150 body length s^(–1)), while exerting large forces exceeding 500 pN. Factors influencing the efficiency of the aluminum–water reaction and the resulting propulsion behavior and motor lifetime, including the ionic strength and environmental pH, are investigated. The resulting water-propelled Al–Ga/Ti motors move efficiently in different biological media (e.g., human serum) and hold considerable promise for diverse biomedical or industrial applications
(6R,7R)-3-Hydroxymethyl-7-(2-phenylacetamido)-3-cephem-4-carboxylic acid lactone
In the title compound {systematic name: N-[(4R,5R)-3,11-dioxo-10-oxa-6-thia-2-azatricyclo[6.3.0.02,5]undec-1(8)-en-4-yl]-2-phenylacetamide}, C16H14N2O4S, the four- and five-membered rings adopt planar conformations (with r.m.s. deviations of 0.0349 and 0.0108 Å respectively) while the six-membered ring adopts a half-chair, or envelope-like, conformation with the S atom in the flap position. In the crystal, molecules are linked by N—H⋯O hydrogen bonds
Topological (Sliced) Doping of a 3D Peierls System: Predicted Structure of Doped BaBiO3
At hole concentrations below x=0.4, Ba_(1-x)K_xBiO_3 is non-metallic. At x=0,
pure BaBiO3 is a Peierls insulator. Very dilute holes create bipolaronic point
defects in the Peierls order parameter. Here we find that the Rice-Sneddon
version of Peierls theory predicts that more concentrated holes should form
stacking faults (two-dimensional topological defects, called slices) in the
Peierls order parameter. However, the long-range Coulomb interaction, left out
of the Rice-Sneddon model, destabilizes slices in favor of point bipolarons at
low concentrations, leaving a window near 30% doping where the sliced state is
marginally stable.Comment: 6 pages with 5 embedded postscript figure
Diethyl 2,3-dihydrothieno[3,4-b]-1,4-dioxine-5,7-dicarboxylate
The title compound, C12H14O6S, is a dicarboxylic acid diethyl ester of 3,4-ethylenedioxythiophene, which is a component of electrically conductive poly(3,4-ethylenedioxythiophene) (PEDOT). The ethylene group is disordered over two sites with occupancy factors 0.64 and 0.36. Both the carbonyl groups are coplanar with the thiophene ring. The molecules form centrosymmetric dimers with an R
2
2(12) coupling by intermolecular C—H⋯O hydrogen bonds [3.333 (5) Å] at the ethoxycarbonyl groups. The dimer units are arranged to form a ribbon-like molecular sheet
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Electrotunable liquid sulfur microdroplets.
Manipulating liquids with tunable shape and optical functionalities in real time is important for electroactive flow devices and optoelectronic devices, but remains a great challenge. Here, we demonstrate electrotunable liquid sulfur microdroplets in an electrochemical cell. We observe electrowetting and merging of sulfur droplets under different potentiostatic conditions, and successfully control these processes via selective design of sulfiphilic/sulfiphobic substrates. Moreover, we employ the electrowetting phenomena to create a microlens based on the liquid sulfur microdroplets and tune its characteristics in real time through changing the shape of the liquid microdroplets in a fast, repeatable, and controlled manner. These studies demonstrate a powerful in situ optical battery platform for unraveling the complex reaction mechanism of sulfur chemistries and for exploring the rich material properties of the liquid sulfur, which shed light on the applications of liquid sulfur droplets in devices such as microlenses, and potentially other electrotunable and optoelectronic devices
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