3,001 research outputs found
Glass transition of hard spheres in high dimensions
We have investigated analytically and numerically the liquid-glass transition
of hard spheres for dimensions in the framework of mode-coupling
theory. The numerical results for the critical collective and self
nonergodicity parameters and exhibit
non-Gaussian -dependence even up to . and
differ for , but become identical on a scale
, which is proven analytically. The critical packing fraction
is above the corresponding Kauzmann packing
fraction derived by a small cage expansion. Its quadratic
pre-exponential factor is different from the linear one found earlier. The
numerical values for the exponent parameter and therefore the critical
exponents and depend on , even for the largest values of .Comment: 11 pages, 8 figures, Phys. Rev. E (in print
Evidence for compact cooperatively rearranging regions in a supercooled liquid
We examine structural relaxation in a supercooled glass-forming liquid
simulated by NVE molecular dynamics. Time correlations of the total kinetic
energy fluctuations are used as a comprehensive measure of the system's
approach to the ergodic equilibrium. We find that, under cooling, the total
structural relaxation becomes delayed as compared with the decay of the
component of the intermediate scattering function corresponding to the main
peak of the structure factor. This observation can be explained by collective
movements of particles preserving many-body structural correlations within
compact 3D cooperatively rearranging regions.Comment: 8 pages, 4 figure
Environmental factors shaping the ecological niches of ammonia-oxidizing archaea
For more than 100 years it was believed that bacteria were the only group responsible for the oxidation of ammonia. However, recently, a new strain of archaea bearing a putative ammonia monooxygenase subunit A (amoA) gene and able to oxidize ammonia was isolated from a marine aquarium tank. Ammonia-oxidizing archaea (AOA) were subsequently discovered in many ecosystems of varied characteristics and even found as the predominant causal organisms in some environments. Here, we summarize the current knowledge on the environmental conditions related to the presence of AOA and discuss the possible site-related properties. Considering these data, we deduct the possible niches of AOA based on pH, sulfide and phosphate levels. It is proposed that the AOA might be important actors within the nitrogen cycle in low-nutrient, low-pH, and sulfide-containing environments
Concentration and mass dependence of transport coefficients and correlation functions in binary mixtures with high mass-asymmetry
Correlation functions and transport coefficients of self-diffusion and shear
viscosity of a binary Lennard-Jones mixture with components differing only in
their particle mass are studied up to high values of the mass ratio ,
including the limiting case , for different mole fractions .
Within a large range of and the product of the diffusion coefficient
of the heavy species and the total shear viscosity of the mixture
is found to remain constant, obeying a generalized Stokes-Einstein
relation. At high liquid density, large mass ratios lead to a pronounced cage
effect that is observable in the mean square displacement, the velocity
autocorrelation function and the van Hove correlation function
Unveiling the capabilities of bipolar conical channels in neuromorphic iontronics
Conical channels filled with an aqueous electrolyte have been proposed as
promising candidates for iontronic neuromorphic circuits. This is facilitated
by a novel analytical model for the internal channel dynamics [Kamsma et al.,
arXiv:2301.06158, 2023], the relative ease of fabrication of conical channels,
and the wide range of achievable memory retention times by varying the channel
lengths. In this work, we demonstrate that the analytical model for conical
channels can be generalized to channels with an inhomogeneous surface charge
distribution, which we predict to exhibit significantly stronger current
rectification and more pronounced memristive properties in the case of bipolar
channels, i.e. channels where the tip and base carry a surface charge of
opposite sign. Additionally, we show that the use of bipolar conical channels
in a previously proposed iontronic circuit features hallmarks of neuronal
communication, such as all-or-none action potentials and spike train
generation. Bipolar channels allow, however, for circuit parameters in the
range of their biological analogues, and exhibit membrane potentials that match
well with biological mammalian action potentials, further supporting its
potential for bio-compatibility
Iontronic Neuromorphic Signaling with Conical Microfluidic Memristors
Experiments have shown that the conductance of conical channels, filled with
an aqueous electrolyte, can strongly depend on the history of the applied
voltage. These channels hence have a memory and are promising elements in
brain-inspired (iontronic) circuits. We show here that the memory of such
channels stems from transient concentration polarization over the ionic
diffusion time. We derive an analytic approximation for these dynamics which
shows good agreement with full finite-element calculations. Using our analytic
approximation, we propose an experimentally realisable Hodgkin-Huxley iontronic
circuit where micrometer cones take on the role of sodium and potassium
channels. Our proposed circuit exhibits key features of neuronal communication
such as all-or-none action potentials upon a pulse stimulus and a spike train
upon a sustained stimulus
The many roles of mellitic acid during barium sulfate crystallization
The various roles of mellitic acid during barium sulfate crystallization from nucleation to mesocrystal formation are explored and elucidated
Structural Relaxation and Mode Coupling in a Simple Liquid: Depolarized Light Scattering in Benzene
We have measured depolarized light scattering in liquid benzene over the
whole accessible temperature range and over four decades in frequency. Between
40 and 180 GHz we find a susceptibility peak due to structural relaxation. This
peak shows stretching and time-temperature scaling as known from
relaxation in glass-forming materials. A simple mode-coupling model provides
consistent fits of the entire data set. We conclude that structural relaxation
in simple liquids and relaxation in glass-forming materials are
physically the same. A deeper understanding of simple liquids is reached by
applying concepts that were originally developed in the context of
glass-transition research.Comment: submitted to New J. Phy
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