5,017 research outputs found
New Insights into Traffic Dynamics: A Weighted Probabilistic Cellular Automaton Model
From the macroscopic viewpoint for describing the acceleration behavior of
drivers, this letter presents a weighted probabilistic cellular automaton model
(the WP model, for short) by introducing a kind of random acceleration
probabilistic distribution function. The fundamental diagrams, the
spatio-temporal pattern are analyzed in detail. It is shown that the presented
model leads to the results consistent with the empirical data rather well,
nonlinear velocity-density relationship exists in lower density region, and a
new kind of traffic phenomenon called neo-synchronized flow is resulted.
Furthermore, we give the criterion for distinguishing the high-speed and
low-speed neo-synchronized flows and clarify the mechanism of this kind of
traffic phenomena. In addition, the result that the time evolution of
distribution of headways is displayed as a normal distribution further
validates the reasonability of the neo-synchronized flow. These findings
suggest that the diversity and randomicity of drivers and vehicles has indeed
remarkable effect on traffic dynamics.Comment: 12 pages, 5 figures, submitted to Europhysics Letter
The structural basis of the Talin-KANK1 interaction that coordinates the actin and microtubule cytoskeletons at focal adhesions
Adhesion between cells and the extracellular matrix (ECM) is mediated by heterodimeric (alphabeta) integrin receptors that are intracellularly linked to the contractile actomyosin machinery. One of the proteins that control this link is talin, which organises cytosolic signalling proteins into discrete complexes on beta-integrin tails referred to as focal adhesions (FAs). The adapter protein KANK1 binds to talin in the region of FAs known as the adhesion belt. Here, we developed a novel crystallographic method to resolve the talin-KANK1 complex. This structure revealed that the talin binding KN motif of KANK1 has a novel fold, where a beta-turn stabilises the alpha-helical region, explaining its specific interaction with talin R7 and high affinity. Single point mutants in KANK1 identified from the structure abolished the interaction and enabled us to examine KANK1 enrichment in the adhesion belt. Strikingly, in cells expressing a constitutively active form of vinculin that keeps the FA structure intact even in the presence of myosin inhibitors, KANK1 localises throughout the entire FA structure even when actomyosin tension is released. We propose a model whereby actomyosin forces on talin eliminate KANK1 from talin binding in the centre of FAs while retaining it at the adhesion periphery
In situ characterization of cofacial Co(IV) centers in Co_4O_4 cubane: Modeling the high-valent active site in oxygen-evolving catalysts
The Co_4O_4 cubane is a representative structural model of oxidic cobalt oxygen-evolving catalysts (Co-OECs). The Co-OECs are active when residing at two oxidation levels above an all-Co(III) resting state. This doubly oxidized Co(IV)_2 state may be captured in a Co(III)_2(IV)_2 cubane. We demonstrate that the Co(III)_2(IV)_2 cubane may be electrochemically generated and the electronic properties of this unique high-valent state may be probed by in situ spectroscopy. Intervalence charge-transfer (IVCT) bands in the near-IR are observed for the Co(III)_2(IV)_2 cubane, and spectroscopic analysis together with electrochemical kinetics measurements reveal a larger reorganization energy and a smaller electron transfer rate constant for the doubly versus singly oxidized cubane. Spectroelectrochemical X-ray absorption data further reveal systematic spectral changes with successive oxidations from the cubane resting state. Electronic structure calculations correlated to experimental data suggest that this state is best represented as a localized, antiferromagnetically coupled Co(IV)_2 dimer. The exchange coupling in the cofacial Co(IV)_2 site allows for parallels to be drawn between the electronic structure of the Co_4O_4 cubane model system and the high-valent active site of the Co-OEC, with specific emphasis on the manifestation of a doubly oxidized Co(IV)_2 center on O-O bond formation
In vivo T1ρ and T2 mapping of articular cartilage in osteoarthritis of the knee using 3T MRI
SummaryObjectiveEvaluation and treatment of patients with early stages of osteoarthritis (OA) is dependent upon an accurate assessment of the cartilage lesions. However, standard cartilage dedicated magnetic resonance (MR) techniques are inconclusive in quantifying early degenerative changes. The objective of this study was to determine the ability of MR T1rho (T1ρ) and T2 mapping to detect cartilage matrix degeneration between normal and early OA patients.MethodSixteen healthy volunteers (mean age 41.3) without clinical or radiological evidence of OA and 10 patients (mean age 55.9) with OA were scanned using a 3Tesla (3T) MR scanner. Cartilage volume and thickness, and T1ρ and T2 values were compared between normal and OA patients. The relationship between T1ρ and T2 values, and Kellgren–Lawrence scores based on plain radiographs and the cartilage lesion grading based on MR images were studied.ResultsThe average T1ρ and T2 values were significantly increased in OA patients compared with controls (52.04±2.97ms vs 45.53±3.28ms with P=0.0002 for T1ρ, and 39.63±2.69ms vs 34.74±2.48ms with P=0.001 for T2). Increased T1ρ and T2 values were correlated with increased severity in radiographic and MR grading of OA. T1ρ has a larger range and higher effect size than T2, 3.7 vs 3.0.ConclusionOur results suggest that both in vivo T1ρ and T2 relaxation times increase with the degree of cartilage degeneration. T1ρ relaxation time may be a more sensitive indicator for early cartilage degeneration than T2. The ability to detect early cartilage degeneration prior to morphologic changes may allow us to critically monitor the course of OA and injury progression, and to evaluate the success of treatment to patients with early stages of OA
elearning improves allied health professionals\u27 knowledge and confidence to manage medically unexplained chronic fatigue states: A randomized controlled trial
Objectives: To evaluate the impact of eLearning by allied health professionals on improving the knowledge and confidence to manage people with medically unexplained chronic fatigue states (FS). Methods: Using a parallel randomized controlled trial design, participants were randomized 1:1 to a 4-week eLearning or wait-list control group. Knowledge and self-reported confidence in clinical skills to implement a therapeutic intervention for patients with FS were assessed at baseline, post-intervention and follow-up. Secondary outcomes (adherence and satisfaction with online education, knowledge retention) were also assessed. Data was analyzed using intention-to-treat. Results: There were 239 participants were randomized (eLearning n = 119, control n = 120), of whom 101 (85%) eLearning and 107 (89%) control participants completed baseline assessments and were included in the analysis. Knowledge (out of 100) improved significantly more in the eLearning group compared to the control group [mean difference (95% CI) 8.6 (5.9 to 11.4), p \u3c 0.001]. Knowledge was reduced in the eLearning group at follow-up but was still significantly higher than baseline [6.0 (3.7 to 8.3), p \u3c 0.001]. Median change (out of 5) in confidence in clinical skills to implement the FS intervention was also significantly greater in the eLearning group compared to the control group [knowledge: eLearning (1.2), control (0); clinical skills: eLearning (1), control (0.1); both p \u3c 0.001)]. Average time spent on the eLearning program was 8.8 h. Most participants (80%) rated the lesson difficulty as at the “right level”, and 91% would recommend it to others. Conclusions: eLearning increased knowledge and confidence to manage FS amongst allied health professionals and was well-accepted. Registration: ACTRN12616000296437 https://anzctr.org.au/Trial/Registration/TrialReview.aspx?id=370222&isReview=true
A stochastic cellular automaton model for traffic flow with multiple metastable states
A new stochastic cellular automaton (CA) model of traffic flow, which
includes slow-to-start effects and a driver's perspective, is proposed by
extending the Burgers CA and the Nagel-Schreckenberg CA model. The flow-density
relation of this model shows multiple metastable branches near the transition
density from free to congested traffic, which form a wide scattering area in
the fundamental diagram. The stability of these branches and their velocity
distributions are explicitly studied by numerical simulations.Comment: 11 pages, 20 figures, submitted for publicatio
Ultrafast optical control of entanglement between two quantum dot spins
The interaction between two quantum bits enables entanglement, the
two-particle correlations that are at the heart of quantum information science.
In semiconductor quantum dots much work has focused on demonstrating single
spin qubit control using optical techniques. However, optical control of
entanglement of two spin qubits remains a major challenge for scaling from a
single qubit to a full-fledged quantum information platform. Here, we combine
advances in vertically-stacked quantum dots with ultrafast laser techniques to
achieve optical control of the entangled state of two electron spins. Each
electron is in a separate InAs quantum dot, and the spins interact through
tunneling, where the tunneling rate determines how rapidly entangling
operations can be performed. The two-qubit gate speeds achieved here are over
an order of magnitude faster than in other systems. These results demonstrate
the viability and advantages of optically controlled quantum dot spins for
multi-qubit systems.Comment: 24 pages, 5 figure
Density Fluctuations in an Electrolyte from Generalized Debye-Hueckel Theory
Near-critical thermodynamics in the hard-sphere (1,1) electrolyte is well
described, at a classical level, by Debye-Hueckel (DH) theory with (+,-) ion
pairing and dipolar-pair-ionic-fluid coupling. But DH-based theories do not
address density fluctuations. Here density correlations are obtained by
functional differentiation of DH theory generalized to {\it non}-uniform
densities of various species. The correlation length diverges universally
at low density as (correcting GMSA theory). When
one has as
where the amplitudes compare informatively with experimental data.Comment: 5 pages, REVTeX, 1 ps figure included with epsf. Minor changes,
references added. Accepted for publication in Phys. Rev. Let
Ginzburg Criterion for Coulombic Criticality
To understand the range of close-to-classical critical behavior seen in
various electrolytes, generalized Debye-Hueckel theories (that yield density
correlation functions) are applied to the restricted primitive model of
equisized hard spheres. The results yield a Landau-Ginzburg free-energy
functional for which the Ginzburg criterion can be explicitly evaluated. The
predicted scale of crossover from classical to Ising character is found to be
similar in magnitude to that derived for simple fluids in comparable fashion.
The consequences in relation to experiments are discussed briefly.Comment: 4 pages, revtex, 2 tables (latex2.09 required due to revtex's
incompatibility with latex2e tables
Pair-breaking quantum phase transition in superconducting nanowires
A quantum phase transition (QPT) between distinct ground states of matter is
a wide-spread phenomenon in nature, yet there are only a few experimentally
accessible systems where the microscopic mechanism of the transition can be
tested and understood. These cases are unique and form the experimentally
established foundation for our understanding of quantum critical phenomena.
Here we report the discovery that a magnetic-field-driven QPT in
superconducting nanowires - a prototypical 1d-system - can be fully explained
by the critical theory of pair-breaking transitions characterized by a
correlation length exponent and dynamic critical exponent . We find that in the quantum critical regime, the electrical
conductivity is in agreement with a theoretically predicted scaling function
and, moreover, that the theory quantitatively describes the dependence of
conductivity on the critical temperature, field magnitude and orientation,
nanowire cross sectional area, and microscopic parameters of the nanowire
material. At the critical field, the conductivity follows a
dependence predicted by phenomenological scaling theories and more recently
obtained within a holographic framework. Our work uncovers the microscopic
processes governing the transition: The pair-breaking effect of the magnetic
field on interacting Cooper pairs overdamped by their coupling to electronic
degrees of freedom. It also reveals the universal character of continuous
quantum phase transitions.Comment: 22 pages, 5 figure
- …