1,234 research outputs found
Synthetic Turing protocells: vesicle self-reproduction through symmetry-breaking instabilities
The reproduction of a living cell requires a repeatable set of chemical
events to be properly coordinated. Such events define a replication cycle,
coupling the growth and shape change of the cell membrane with internal
metabolic reactions. Although the logic of such process is determined by
potentially simple physico-chemical laws, the modeling of a full,
self-maintained cell cycle is not trivial. Here we present a novel approach to
the problem which makes use of so called symmetry breaking instabilities as the
engine of cell growth and division. It is shown that the process occurs as a
consequence of the breaking of spatial symmetry and provides a reliable
mechanism of vesicle growth and reproduction. Our model opens the possibility
of a synthetic protocell lacking information but displaying self-reproduction
under a very simple set of chemical reactions
Coupled THM analysis of long-term anisotropic convergence in the full-scale micro tunnel excavated in the Callovo-Oxfordian argillite
The main purpose of this paper is to analyse the convergence measurements of the ALC1604 in situ heating test carried out in the Callovo-Oxfordian claystone formation (COx) in the Meuse/Haute-Marne underground research laboratory (MHM URL). The concept of the test consists of horizontal micro-tunnel, equipped with a steel casing. The micro-tunnel is excavated in the direction of the horizontal principal major stress (sH). In situ observations showed anisotropic convergence with the maximum and minimum values in the horizontal and vertical directions, respectively. Coupled THM numerical analyses have been carried out to provide a structured framework for interpretation, and to enhance understanding of THM behaviour of Callovo-Oxfordian claystone. However, a special mechanical constitutive law is adopted for the description of the time-dependent anisotropic behaviour of the COx. The simulation of the test using this enhanced model provides a satisfactory reproduction of the THM long-term anisotropic convergence results. It also provides a better understanding of the observed test response.Postprint (published version
Thermo-hydro-mechanical simulation of a full-scale steel-lined micro-tunnel excavated in the callovooxfordian claystone
The paper presents an interpretation of the full-scale ALC1604 in situ heating test carried out in Callovo-Oxfordian claystone (COx) in the Meuse/Haute-Marne underground research laboratory (MHM URL). The MHM URL is a site-specific facility planned to study radioactive waste disposal in the COx. The thermo-hydro-mechanical (THM) behaviour of the host rock is significant for the design of the underground radioactive waste disposal facility and for its long-term safety. When subjected to thermal loading, the Callovo-Oxfordian claystone of low permeability (~10-20-10-21 m2) exhibits a strong pore pressure response that significantly affects the hydraulic and mechanical behaviour of the material. The observations gathered in the in situ test have provided an opportunity to examine the integrated thermo-hydromechanical (THM) response of this sedimentary clay. Coupled THM numerical analyses have been carried out to provide a structured framework for interpretation, and to enhance understanding of THM behaviour of COx. Numerical analyses have been based on a coupled theoretical formulation that incorporates a constitutive law specially developed for this type of material. The law includes a number of features that are relevant for a satisfactory description of the hydromechanical behaviour. By performing the numerical analysis, it has been possible to incorporate anisotropy of material parameters and of in situ stresses. The performance and analysis of the in situ tests have significantly enhanced the understanding of a complex THM problem and have proved the capability of the numerical formulation to provide adequate predictive capacity
Primeros datos cromoestratigráficos de las series evaporíticas del triásico superior de Valencia (España)
El Triásico Superior del sector central valenciano de la Cordillera Ibérica presenta una facies germánica (Keuper) integrada por dos secuencias evaporíticas separadas por un episodio detrítico principal. Los datos preliminares obtenidos de una investigación palinológica en curso revelan una edad Karniense para todos estos materiales
Topology and Evolution of Technology Innovation Networks
The web of relations linking technological innovation can be fairly described
in terms of patent citations. The resulting patent citation network provides a
picture of the large-scale organization of innovations and its time evolution.
Here we study the patterns of change of patents registered by the US Patent and
Trademark Office (USPTO). We show that the scaling behavior exhibited by this
network is consistent with a preferential attachment mechanism together with a
Weibull-shaped aging term. Such attachment kernel is shared by scientific
citation networks, thus indicating an universal type of mechanism linking ideas
and designs and their evolution. The implications for evolutionary theory of
innovation are discussed.Comment: 6 pages, 5 figures, submitted to Physical Review
Exploring complex networks by walking on them
We carry out a comparative study on the problem for a walker searching on
several typical complex networks. The search efficiency is evaluated for
various strategies. Having no knowledge of the global properties of the
underlying networks and the optimal path between any two given nodes, it is
found that the best search strategy is the self-avoid random walk. The
preferentially self-avoid random walk does not help in improving the search
efficiency further. In return, topological information of the underlying
networks may be drawn by comparing the results of the different search
strategies.Comment: 5 pages, 5 figure
A linear construction for certain Kerdock and Preparata codes
The Nordstrom-Robinson, Kerdock, and (slightly modified) Pre\- parata codes
are shown to be linear over \ZZ_4, the integers . The Kerdock and
Preparata codes are duals over \ZZ_4, and the Nordstrom-Robinson code is
self-dual. All these codes are just extended cyclic codes over \ZZ_4. This
provides a simple definition for these codes and explains why their Hamming
weight distributions are dual to each other. First- and second-order
Reed-Muller codes are also linear codes over \ZZ_4, but Hamming codes in
general are not, nor is the Golay code.Comment: 5 page
Cronoestratigrafía (Palinología) del Triásico Sudpirenaico y del Pirineo Vasco-Cantábrico
This paper presients a general chronostratigraphy of the south Pyrenean Triassic basi:d on palynological studies. The Triassic in Les Nogueres-Cadí and the Basque Country areas is divided into the Buntsandstein, Muschelkalk and Keuper facies and the Isábena Forrnation. The Conglomeratic, sandstone and lutitic Unit of the Buntsandstein in the Puerto dr Otxondo (Basque Country) presents Stellapollenites thiergartii and together with the absence of Praecirculina granifer, suggests a Lower-middle Anisian age. The Lutitic Unit of the Buntsandstein in Igüem, Sant Sebastia de Buseu and Baga (Les Nogueres-Cadí) presenits Illinites kosankeii and Stellapollenites thiergartii, and the absence of Praecirculina granifer, indicates a Lower Anisian age. The Muschelkailk in Hostalets (Les Nogueres) presents Camerosporites secatus, suggesting an upper Ladinian age. The transit zone between the Muschelkaik and the Keuper facies in Odkn (Cadí) shows a palynological assemblage with Patinasporites densus, Partitisporites quadruplicis and Staurosaccites quadrifidus, indicating a Camain age, possibly Middie-upper Camian. The lower part of the Keuper in Noguera de Tor and Adons, in the Les Nogueres area, presents a palynological assemblage with Classopollis, Granuloperculatipollis rudis, Ovalipollis ovalis, Praecirculina granifer and Triadispora. The abundance of Classopollis and the presence of Granul~p~erculatipollrius dis suggest a Norian age, possibly lower-middle. The upper part of the Keuper in La Nou (Pedraforca) is Rhaetian in age due to the presence of cf. Deltaidospora and cf. Taeniasporites. The base of tlie Isábena Formation in Noves de Segre presents Corollina zwolinskae and Cerebropollenites pseudomassulae, indicating a Rhaetian age. The palynological studies, together with the forarninifera and conodonta data, deteimine the existence of important stratigraphicc hiatuses in the south Pyrenean Triassic supercycle
Nature and Nurture in Dark Matter Halos
Cosmological simulations consistently predict specific properties of dark
matter halos, but these have not yet led to a physical understanding that is
generally accepted. This is especially true for the central regions of these
structures. Recently two major themes have emerged. In one, the dark matter
halo is primarily a result of the sequential accretion of primordial structure
(ie `Nature'); while in the other, dynamical relaxation (ie `Nurture')
dominates at least in the central regions. Some relaxation is however required
in either mechanism. In this paper we accept the recently established
scale-free sub-structure of halos as an essential part of both mechanisms.
Consequently; a simple model for the central relaxation based on a self-similar
cascade of tidal interactions, is contrasted with a model based on the
accretion of adiabatically self-similar, primordial structure. We conclude that
a weak form of this relaxation is present in the simulations, but that is
normally described as the radial orbit instability.Comment: 25 pages, 3 figures, fig with parts 1 to d, fig 3 with parts a to
Graph Partitioning using Quantum Annealing on the D-Wave System
In this work, we explore graph partitioning (GP) using quantum annealing on
the D-Wave 2X machine. Motivated by a recently proposed graph-based electronic
structure theory applied to quantum molecular dynamics (QMD) simulations, graph
partitioning is used for reducing the calculation of the density matrix into
smaller subsystems rendering the calculation more computationally efficient.
Unconstrained graph partitioning as community clustering based on the
modularity metric can be naturally mapped into the Hamiltonian of the quantum
annealer. On the other hand, when constraints are imposed for partitioning into
equal parts and minimizing the number of cut edges between parts, a quadratic
unconstrained binary optimization (QUBO) reformulation is required. This
reformulation may employ the graph complement to fit the problem in the Chimera
graph of the quantum annealer. Partitioning into 2 parts, 2^N parts
recursively, and k parts concurrently are demonstrated with benchmark graphs,
random graphs, and small material system density matrix based graphs. Results
for graph partitioning using quantum and hybrid classical-quantum approaches
are shown to equal or out-perform current "state of the art" methods
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