15 research outputs found
Cement nanotubes: on chemical gardens and cement
© 2016 Springer Science+Business Media New York“Do cement nanotubes exist?” is a question that has recently been asked. The answer is yes, they do exist. The evidence is in the literature, in tens of papers showing in detail chemical garden-type tubes in cement from the nanoscale upwards that were published in the 1970s and 1980s. Here, we present a nano-review of the literature
Passive Scalars and Three-Dimensional Liouvillian Maps
Global aspects of the motion of passive scalars in time-dependent
incompressible fluid flows are well described by volume-preserving
(Liouvillian) three-dimensional maps. In this paper the possible invariant
structures in Liouvillian maps and the two most interesting nearly-integrable
cases are investigated. In addition, the fundamental role of invariant lines in
organizing the dynamics of this type of system is exposed. Bifurcations
involving the destruction of some invariant lines and tubes and the creation of
new ones are described in detail.Comment: 18 pages, plain TeX, appears in Physica D, 76, 22-33, 1994. (Lack of
figures in original submission corrected in this new upload.
Geometric phases in discrete dynamical systems
In order to study the behaviour of discrete dynamical systems under adiabatic
cyclic variations of their parameters, we consider discrete versions of
adiabatically-rotated rotators. Paralleling the studies in continuous systems,
we generalize the concept of geometric phase to discrete dynamics and
investigate its presence in these rotators. For the rotated sine circle map, we
demonstrate an analytical relationship between the geometric phase and the
rotation number of the system. For the discrete version of the rotated rotator
considered by Berry, the rotated standard map, we further explore this
connection as well as the role of the geometric phase at the onset of chaos.
Further into the chaotic regime, we show that the geometric phase is also
related to the diffusive behaviour of the dynamical variables and the Lyapunov
exponent
Labyrinthine Turing Pattern Formation in the Cerebral Cortex
I propose that the labyrinthine patterns of the cortices of mammalian brains
may be formed by a Turing instability of interacting axonal guidance species
acting together with the mechanical strain imposed by the interconnecting
axons.Comment: See home page http://lec.ugr.es/~julya
Chemobrionics: from self-assembled material architectures to the origin of life
Self-organizing precipitation processes, such as chemical gardens forming biomimetic micro- and nanotubular forms, have the potential to show us new fundamental science to explore, quantify, and understand nonequilibrium physicochemical systems, and shed light on the conditions for life's emergence. The physics and chemistry of these phenomena, due to the assembly of material architectures under a flux of ions, and their exploitation in applications, have recently been termed chemobrionics. Advances in understanding in this area require a combination of expertise in physics, chemistry, mathematical modeling, biology, and nanoengineering, as well as in complex systems and nonlinear and materials sciences, giving rise to this new synergistic discipline of chemobrionics
From chemical gardens to chemobrionics
Chemical gardens are perhaps the best example in chemistry of a
self-organizing nonequilibrium process that creates complex
structures. Many different chemical systems and materials can
form these self-assembling structures, which span at least 8
orders of magnitude in size, from nanometers to meters. Key to
this marvel is the self-propagation under fluid advection of
reaction zones forming semipermeable precipitation membranes
that maintain steep concentration gradients, with osmosis and
buoyancy as the driving forces for fluid flow. Chemical gardens
have been studied from the alchemists onward, but now in the
21st century we are beginning to understand how they can lead
us to a new domain of self-organized structures of semipermeable
membranes and amorphous as well as polycrystalline solids
produced at the interface of chemistry, fluid dynamics, and
materials science. We propose to call this emerging field
chemobrionics
Embryonic nodal flow and the dynamics of nodal vesicular parcels
We address with fluid-dynamical simulations using direct numerical techniques three important and fundamental questions with respect to fluid flow within the mouse node and left–right development. First, we consider the differences between what is experimentally observed when assessing cilium-induced fluid flow in the mouse node in vitro and what is to be expected in vivo. The distinction is that in vivo, the leftward fluid flow across the mouse node takes place within a closed system and is consequently confined, while this is no longer the case on removing the covering membrane and immersing the embryo in a fluid-filled volume to perform in vitro experiments. Although there is a central leftward flow in both instances, we elucidate some important distinctions about the closed in vivo situation. Second, we model the movement of the newly discovered nodal vesicular parcels (NVPs) across the node and demonstrate that the flow should indeed cause them to accumulate on the left side of the node, as required for symmetry breaking. Third, we discuss the rupture of NVPs. Based on the biophysical properties of these vesicles, we argue that the morphogens they contain are likely not delivered to the surrounding cells by their mechanical rupture either by the cilia or the flow, and rupture must instead be induced by an as yet undiscovered biochemical mechanism
Chemobrionics Database: Categorisation of Chemical Gardens According to the Nature of the Anion, Cation and Experimental Procedure
International audienc