1,821 research outputs found
Driving dynamic colloidal assembly using eccentric self-propelled colloids
Designing protocols to dynamically direct the self-assembly of colloidal
particles has become an important direction in soft matter physics because of
the promising applications in fabrication of dynamic responsive functional
materials. Here using computer simulations, we found that in the mixture of
passive colloids and eccentric self-propelled active particles, when the
eccentricity and self-propulsion of active particles are high enough, the
eccentric active particles can push passive colloids to form a large dense
dynamic cluster, and the system undergoes a novel dynamic demixing transition.
Our simulations show that the dynamic demixing occurs when the eccentric active
particles move much faster than the passive particles such that the dynamic
trajectories of different active particles can overlap with each other while
passive particles are depleted from the dynamic trajectories of active
particles. Our results suggest that this is in analogy to the entropy driven
demixing in colloid-polymer mixtures, in which polymer random coils can overlap
with each other while deplete the colloids. More interestingly, we find that by
fixing the passive colloid composition at certain value, with increasing the
density, the system undergoes an intriguing re-entrant mixing, and the demixing
only occurs within certain intermediate density range. This suggests a new way
of designing active matter to drive the self-assembly of passive colloids and
fabricate dynamic responsive materials.Comment: Accepted in Soft Matter. Supplementary information can found at
https://www.dropbox.com/sh/xb3u5iaoucc2ild/AABFUyqjXips7ewaie2rFbj_a?dl=
Self-Assembled Chiral Photonic Crystals From Colloidal Helices Racemate
Chiral crystals consisting of micro-helices have many optical properties
while presently available fabrication processes limit their large-scale
applications in photonic devices. Here, by using a simplified simulation
method, we investigate a bottom-up self-assembly route to build up helical
crystals from the smectic monolayer of colloidal helices racemate. With
increasing the density, the system undergoes an entropy-driven
co-crystallization by forming crystals of various symmetries with different
helical shapes. In particular, we identify two crystals of helices arranged in
the binary honeycomb and square lattices, which are essentially composed by two
sets of opposite-handed chiral crystal. Photonic calculations show that these
chiral structures can have large complete photonic bandgaps. In addition, in
the self-assembled chiral square crystal, we also find dual polarization
bandgaps that selectively forbid the propagation of circularly polarized lights
of a specific handedness along the helical axis direction. The self-assembly
process in our proposed system is robust, suggesting possibilities of using
chiral colloids to assemble photonic metamaterials.Comment: Accepted in ACS Nan
Edge Manipulations for the Maximum Vertex-Weighted Bipartite b-matching
In this paper, we explore the Mechanism Design aspects of the Maximum
Vertex-weighted -Matching (MVbM) problem on bipartite graphs .
The set comprises agents, while represents tasks. The set is the
private information of either agents or tasks. In this framework, we
investigate three mechanisms - \MB, \MD, and \MG - that, given an MVbM
problem as input, return a -matching. We examine scenarios in which either
agents or tasks are strategic and report their adjacent edges to one of the
three mechanisms. In both cases, we assume that the strategic entities are
bounded by their statements: they can hide edges, but they cannot report edges
that do not exist. First, we consider the case in which agents can manipulate.
In this framework, \MB and \MD are optimal but not truthful. By
characterizing the Nash Equilibria induced by \MB and \MD, we reveal that
both mechanisms have a Price of Anarchy () and Price of Stability ()
of . These efficiency guarantees are tight; no deterministic mechanism can
achieve a lower or . In contrast, the third mechanism, \MG, is not
optimal, but truthful and its approximation ratio is . We demonstrate that
this ratio is optimal; no deterministic and truthful mechanism can outperform
it. We then shift our focus to scenarios where tasks can exhibit strategic
behaviour. In this case, \MB, \MD, and \MG all maintain truthfulness,
making \MB and \MD truthful and optimal mechanisms. In conclusion, we
investigate the manipulability of \MB and \MD through experiments on
randomly generated graphs. We observe that (1) \MB is less prone to be
manipulated by the first agent than \MD (2) \MB is more manipulable on
instances in which the total capacity of the agents is equal to the number of
tasks (3) randomizing the agents' order reduces the agents' ability to
manipulate \MB.Comment: 37 pages, 6 figures. arXiv admin note: substantial text overlap with
arXiv:2307.1230
The research infrastructure of Chinese foundations, a database for Chinese civil society studies
This paper provides technical details and user guidance on the Research Infrastructure of Chinese Foundations (RICF), a database of Chinese foundations, civil society, and social development in general. The structure of the RICF is deliberately designed and normalized according to the Three Normal Forms. The database schema consists of three major themes: foundations’ basic organizational profile (i.e., basic profile, board member, supervisor, staff, and related party tables), program information (i.e., program information, major program, program relationship, and major recipient tables), and financial information (i.e., financial position, financial activities, cash flow, activity overview, and large donation tables). The RICF’s data quality can be measured by four criteria: data source reputation and credibility, completeness, accuracy, and timeliness. Data records are properly versioned, allowing verification and replication for research purposes
A Improved Particle Swarm Optimization Algorithm with Dynamic Acceleration Coefficients
Particle swarm optimization (PSO) is one of the famous heuristic methods. However, this method may suffer to trap at local minima especially for multimodal problem. This paper proposes a modified particle swarm optimization with dynamic acceleration coefficients (ACPSO). To efficiently control the local search and convergence to the global optimum solution, dynamic acceleration coefficients are introduced to PSO. To improve the solution quality and robustness of PSO algorithm, a new best mutation method is proposed to enhance the diversity of particle swarm and avoid premature convergence. The effectiveness of ACPSO algorithm is tested on different benchmarks. Simulation results found that the proposed ACPSO algorithm has good solution quality and more robust than other methods reported in previous work
Role of protein acetylation, formation and dispersal of biofilms, and their impact on insects
Bacterial biofilms form on liquid/air and liquid/solid surfaces and consist of cells combined with an extracellular matrix such as exopolysaccharides, extracellular DNA, and glycoproteins. Bacteria have up to a 1000-fold increase of antibiotic resistance in biofilms compared to planktonic cells. Furthermore, biofilm cells show better tolerance to adverse environmental conditions such as nutrition limitations, temperature changes, pH changes, and non-optimal osmotic conditions. In Escherichia coli, the outer membrane protein OmpA increased biofilm formation on polystyrene, polypropylene, and polyvinyl chloride surfaces while it decreased biofilm formation on glass surfaces. This surface-dependent phenotype was because OmpA inhibits cellulose production by inducing the CpxRA two-component signal transduction pathway, and cellulose inhibits biofilm formation on plastic due to its hydrophilic nature. We discovered, and then engineered, BdcA (formerly YjgI), for biofilm dispersal. We found that in E. coli, BdcA increases motility and extracellular DNA production while it decreases exopolysaccharide production, cell length, and aggregation. We reasoned that the 3, 5-cyclic diguanylic acid (c-di-GMP) levels increase upon deleting bdcA, and showed that BdcA binds c-di-GMP in vitro. In addition, we used protein engineering to evolve BdcA for greater c-di-GMP binding and found that the single amino acid change E50Q causes nearly complete biofilm dispersal.
We isolated Proteus mirabilis from the blowfly Lucilia sericata, which swarmed significantly. By motility screening and complementation with putative interkingdom signal molecules that have been shown to attract flies, we found lactic acid, phenol, NaOH, KOH, putrescine, and ammonia restore the swarming motility of seven different swarming deficient mutants. These mutants and putative signal molecules will be further tested for fly attraction and oviposition. Acetylation of lysine residues is conserved in all three kingdoms although its role in bacteria is not clear. We demonstrated that acetylation enables E. coli to withstand environmental stresses. Specifically, the bacteria became more resistant to heat and oxidative stress. Furthermore, we showed that the increase in oxidative stress resistance is due to the induction of catalase gene katG. Hence we demonstrate for the first time a specific physiological role for acetylation in prokaryotes
Phase Structure of Compact Star in Modified Quark-Meson Coupling Model
The K condensation and quark deconfinement phase transitions are
investigated in the modified quark-meson coupling model. It is shown that K
condensation is suppressed because of the quark deconfinement when
202.2MeV, where is the bag constant for unpaired quark matter.
With the equation of state (EOS) solved self-consistently, we discuss the
properties of compact stars. We find that the EOS of pure hadron matter with
condensed K phase should be ruled out by the redshift for star EXO0748-676,
while EOS containing unpaired quark matter phase with being about
180MeV could be consistent with this observation and the best measured mass of
star PSR 1913+16. We then probe into the change of the phase structures in
possible compact stars with deconfinment phase as the central densities
increase. But if the recent inferred massive star among Terzan 5 with
M1.68M is confirmed, all the present EOSes with condensed phase
and deconfined phase would be ruled out and therefore these exotic phases are
unlikely to appear within neutron stars.Comment: 11 pages, 5 figure
Poly[μ2-aqua-[μ2-1,1′-(butane-1,4-diyl)diimidazole]bis(μ4-naphthalene-1,4-dicarboxylato)dimanganese(II)]
In the title compound, [Mn2(C12H6O4)2(C10H14N4)(H2O)]n or [Mn2(1,4-ndc)2(L)(H2O)]n, where 1,4-ndc is naphthalene-1,4-dicarboxylate and L is 1,1′-(butane-1,4-diyl)diimidazole, the coordination polyhedron around each MnII atom is distorted octahedral. The water molecule and the L ligand are situated across a twofold rotation axis. The MnII atoms are bridged by 1,4-ndc and L ligands, forming a three-dimensional network. O—H⋯O hydrogen bonds are observed within the network
Poly[μ-aqua-[μ-1,1′-(butane-1,4-diyl)diimidazole]bis(μ4-naphthalene-1,4-dicarboxylato)dicadmium(II)]
In the title compound, [Cd2(C12H6O4)2(C10H14N4)(H2O)]n, the coordination polyhedron around each CdII ion is a distorted CdNO5 octahedron. The water O atom has site symmetry 2 and the complete 1,1′-(butane-1,4-diyl)diimidazole (L) ligand is generated by inversion. The naphthalene-1,4-dicarboxylate and L ligands bridge the metal centres, forming a three-dimensional framework, which is consolidated by O—H⋯O hydrogen bonds
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