4,285 research outputs found
Entropy driven key-lock assembly
The effective interaction between a sphere with an open cavity (lock) and a
spherical macroparticle (key), both immersed in a hard sphere fluid, is studied
by means of Monte Carlo simulations. As a result, a 2d map of the key-lock
effective interaction potential is constructed, which leads to the proposal of
a self-assembling mechanism: there exists trajectories through which the
key-lock pair could assemble avoiding trespassing potential barriers. Hence,
solely the entropic contribution can induce their self-assembling even in the
absence of attractive forces. This study points out the solvent contribution
within the underlying mechanisms of substrate-protein assembly/disassembly
processes, which are important steps of the enzyme catalysis and protein
mediated transport
Living on the edge of chaos: minimally nonlinear models of genetic regulatory dynamics
Linearized catalytic reaction equations modeling e.g. the dynamics of genetic
regulatory networks under the constraint that expression levels, i.e. molecular
concentrations of nucleic material are positive, exhibit nontrivial dynamical
properties, which depend on the average connectivity of the reaction network.
In these systems the inflation of the edge of chaos and multi-stability have
been demonstrated to exist. The positivity constraint introduces a nonlinearity
which makes chaotic dynamics possible. Despite the simplicity of such minimally
nonlinear systems, their basic properties allow to understand fundamental
dynamical properties of complex biological reaction networks. We analyze the
Lyapunov spectrum, determine the probability to find stationary oscillating
solutions, demonstrate the effect of the nonlinearity on the effective in- and
out-degree of the active interaction network and study how the frequency
distributions of oscillatory modes of such system depend on the average
connectivity.Comment: 11 pages, 5 figure
A variety of Levitrons: A review
After a brief history and critique of some older instruments, several new
Levitron geometries are described. As a result of their greater stability these
devices can be used as analogues of a number of phenomena and applications,
including magnetic resonance techniques, atom traps and accelerator rings. In
particular, the notion of the spinning magnet (or spignet) in a linear trap is
similar to the mechanism underpinning the confinement of antihydrogen in a
magnetic minimum trap, as achieved in experiments at CERN
ASASSN-13db 2014-2017 Eruption as an Intermediate Luminosity Optical Transient
The low mass star ASASSN-13db experienced an EXor outburst in 2013, which
identified it as a Young Stellar Object (YSO). Then, from 2014 to 2017 it had
another outburst, longer and more luminous than the earlier. We analyze the
observations of the second outburst, and compare it to eruptions of
Intermediate Luminosity Optical Transients (ILOTs). We show that the decline of
the light curve is almost identical to that of the V838 Mon, a prototype of a
type of ILOT known as Luminous Red Nova (LRN). This similarity becomes
conspicuous when oscillations that are associated with rotation are filtered
out from the light curve of ASASSN-13db. We suggest that the eruption was the
result of accretion of a proto-planet of a few Earth masses. The proto-planet
was shredded by tidal forces before it was accreted onto the YSO, releasing
gravitational energy that powered the outburst for days, and
ended in a days decline phase. When the accretion material started
depleting the accretion rate lowered and the eruption light curve declined for
almost two months. Then it exhausted completely, creating a sharp break in the
light curve. Another possibility is that the mass was a result of an
instability in the proto-planetary disk that lead to a large episode of
accretion from an inner viscous disk. We find that the variation of the
temperature of the outburst is consistent with the surface temperature expected
from a depleted viscous accretion disk. The 2014-2017 outburst of ASASSN-13db
may be the least energetic ILOT to have been discovered to date, with an energy
budget of only erg.Comment: Accepted to Galaxie
Gene Therapy Applications to Cancer Treatment
Over the past ten years significant advances have been made in the fields of gene therapy and tumour immunology, such that there now exists a considerable body of evidence validating the proof in the principle of gene therapy based cancer vaccines. While clinical benefit has so far been marginal, data from preclinical and early clinical trials of gene therapy combined with standard therapies are strongly suggestive of additional benefit. Many reasons have been proposed to explain the paucity of clinical responses to single agent vaccination strategies including the poor antigenicity of tumour cells and the development of tolerance through down-regulation of MHC, costimulatory, signal transduction, and other molecules essential for the generation of strong immune responses. In addition, there is now evidence from animal models that the growing tumour may actively inhibit the host immune response. Removal of the primary tumour prior to T cell transfer from the spleen of cancer bearing animals, led to effective tumour cell line specific immunity in the recipient mouse suggesting that there is an ongoing tumour-host interaction. This model also illustrates the potential difficulties of clinical vaccine trials in patients with advanced stage disease
Classification of All Poisson-Lie Structures on an Infinite-Dimensional Jet Group
A local classification of all Poisson-Lie structures on an
infinite-dimensional group of formal power series is given. All
Lie bialgebra structures on the Lie algebra {\Cal G}_{\infty} of
are also classified.Comment: 11 pages, AmSTeX fil
Michaelis-Menten dynamics in protein subnetworks
To understand the behaviour of complex systems it is often necessary to use
models that describe the dynamics of subnetworks. It has previously been
established using projection methods that such subnetwork dynamics generically
involves memory of the past, and that the memory functions can be calculated
explicitly for biochemical reaction networks made up of unary and binary
reactions. However, many established network models involve also
Michaelis-Menten kinetics, to describe e.g. enzymatic reactions. We show that
the projection approach to subnetwork dynamics can be extended to such
networks, thus significantly broadening its range of applicability. To derive
the extension we construct a larger network that represents enzymes and enzyme
complexes explicitly, obtain the projected equations, and finally take the
limit of fast enzyme reactions that gives back Michaelis-Menten kinetics. The
crucial point is that this limit can be taken in closed form. The outcome is a
simple procedure that allows one to obtain a description of subnetwork
dynamics, including memory functions, starting directly from any given network
of unary, binary and Michaelis-Menten reactions. Numerical tests show that this
closed form enzyme elimination gives a much more accurate description of the
subnetwork dynamics than the simpler method that represents enzymes explicitly,
and is also more efficient computationally
Toward an ecological aesthetics: music as emergence
In this article we intend to suggest some ecological based principles
to support the possibility of develop an ecological aesthetics. We consider that
an ecological aesthetics is founded in concepts as âdirect perceptionâ,
âacquisition of affordances and invariantsâ, âembodied embedded
perceptionâ and so on. Here we will purpose that can be possible explain
especially soundscape music perception in terms of direct perception, working
with perception of first hand (in a Gibsonian sense). We will present notions
as embedded sound, detection of sonic affordances and invariants, and at the
end we purpose an experience with perception/action paradigm to make
soundscape music as emergence of a self-organized system
An Information-Centric Platform for Social- and Location-Aware IoT Applications in Smart Cities
Recent advances in Smart City infrastructures and the Internet of Things represent a significant opportunity to improve people's quality of life. Corresponding research often focuses on Cloud-centric network architectures where sensor devices transfer collected data to the Cloud for processing. However, the formidable traffic generated by countless IoT devices and the need for low-latency services raise the need to move away from centralized architectures and bring the computation closer to the data sources. To this end, this paper discusses SPF, a middleware solution that supports IoT application development, deployment, and management. SPF runs IoT services on capable devices located at the network edge and proposes an information-centric programming model that takes advantage of decentralized computation resources located in the proximity of application users and data sources. SPF also adopts Value-of-Information based methods to prioritize the transmission of essential information
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