544 research outputs found
Utilização de aplicativos Base e Calc do pacote BrOffice.org para criação de sistema de informação de pequeno porte.
Este artigo descreve uma forma de se criar um sistema de informação de pequeno porte usando as ferramentas Calc e Base e, com elas integradas, obtém-se uma ferramenta fácil de se usar e acessível a qualquer pessoa, sem custos. Um caso de estudo é mostrado para exemplificar o uso deste sistema
Quantum and Classical in Adiabatic Computation
Adiabatic transport provides a powerful way to manipulate quantum states. By
preparing a system in a readily initialised state and then slowly changing its
Hamiltonian, one may achieve quantum states that would otherwise be
inaccessible. Moreover, a judicious choice of final Hamiltonian whose
groundstate encodes the solution to a problem allows adiabatic transport to be
used for universal quantum computation. However, the dephasing effects of the
environment limit the quantum correlations that an open system can support and
degrade the power of such adiabatic computation. We quantify this effect by
allowing the system to evolve over a restricted set of quantum states,
providing a link between physically inspired classical optimisation algorithms
and quantum adiabatic optimisation. This new perspective allows us to develop
benchmarks to bound the quantum correlations harnessed by an adiabatic
computation. We apply these to the D-Wave Vesuvius machine with revealing -
though inconclusive - results
Role of disorder in the size-scaling of material strength
We study the sample size dependence of the strength of disordered materials
with a flaw, by numerical simulations of lattice models for fracture. We find a
crossover between a regime controlled by the fluctuations due to disorder and
another controlled by stress-concentrations, ruled by continuum fracture
mechanics. The results are formulated in terms of a scaling law involving a
statistical fracture process zone. Its existence and scaling properties are
only revealed by sampling over many configurations of the disorder. The scaling
law is in good agreement with experimental results obtained from notched paper
samples.Comment: 4 pages 5 figure
Statistical physics of fracture and earthquakes
Manifestations of emergent properties in stressed disordered materials are often the result of an interplay of strong perturbations in the stress field around defects. The collective response of a long-ranged correlated multi-component system is an ideal playing field for statistical physics. Hence, many aspects of such collective responses in widely spread length and energy scales can be addressed by tools of statistical physics. In this theme issue some of these aspects are treated from various angles of experiments, simulations and analytical methods, and connected together by their common base of complex-system dynamics
Size effects in statistical fracture
We review statistical theories and numerical methods employed to consider the
sample size dependence of the failure strength distribution of disordered
materials. We first overview the analytical predictions of extreme value
statistics and fiber bundle models and discuss their limitations. Next, we
review energetic and geometric approaches to fracture size effects for
specimens with a flaw. Finally, we overview the numerical simulations of
lattice models and compare with theoretical models.Comment: review article 19 pages, 5 figure
Spectroscopic Characteristics of Carbon Dots (C-Dots) Derived from Carbon Fibers and Conversion to Sulfur-Bridged C-Dots Nanosheets
We synthesized sub‐10 nm carbon nanoparticles (CNPs) consistent with photoluminescent carbon dots (C-dots) from carbon fiber starting material. The production of different C-dots fractions was monitored over seven days. During the course of the reaction, one fraction of C-dots species with relatively high photoluminescence was short-lived, emerging during the first hour of reaction but disappearing after one day of reaction. Isolation of this species during the first hour of the reaction was crucial to obtaining higher-luminescent C-dots species. When the reaction proceeded for one week, the appearance of larger nanostructures was observed over time, with lateral dimensions approaching 200 nm. The experimental evidence suggests that these larger species are formed from small C-dot nanoparticles bridged together by sulfur-based moieties between the C-dot edge groups, as if the C-dots polymerized by cross-linking the edge groups through sulfur bridges. Their size can be tailored by controlling the reaction time. Our results highlight the variety of CNP products, from sub‐10 nm C-dots to ~200 nm sulfur-containing carbon nanostructures, that can be produced over time during the oxidation reaction of the graphenic starting material. Our work provides a clear understanding of when to stop the oxidation reaction during the top-down production of C-dots to obtain highly photoluminescent species or a target average particle size
Decomposing Instantons in Two Dimensions
We study BPS string-like solutions in the 3+1 dimensional gauged CP(1)
non-linear sigma model. The same analysis can be applied to study instantons in
2 euclidean dimensions. We use the moduli matrix approach to construct
analytically the moduli space and and solve numerically the BPS equations. We
identify two topologically inequivalent type of magnetic vortices, which we
call S and N vortices. Moreover we discuss their relation to "lump-string"
solutions present in the un-gauged case. In particular, we describe how a lump
is split into a couple of component S-N vortices after gauging. We extend this
analysis to the case of the extended Abelian Higgs model with two flavors,
which is known to admit semi-local vortices. When we gauge the relative phase
between fields, semi-local vortices are also split into component vortices. We
discuss interesting applications of this simple set-up. First, gauging of
non-linear sigma models reveals a "partonic" nature of instantons in 1+1
dimensions, an idea long studied also in connection with four dimensional
instantons. Second, weak gauging provides for an interesting regularization of
the metric of semi-local vortices which preserves supersymmetry and does not
lift the moduli space of the string.Comment: Minor changes. 27 pages, 5 figure
Glucose and Fatty Acid Metabolism in a 3 Tissue In-Vitro Model Challenged with Normo- and Hyperglycaemia
Nutrient balance in the human body is maintained through systemic signaling between different cells and tissues. Breaking down this circuitry to its most basic elements and reconstructing the metabolic network in-vitro provides a systematic method to gain a better understanding of how cross-talk between the organs contributes to the whole body metabolic profile and of the specific role of each different cell type. To this end, a 3-way connected culture of hepatocytes, adipose tissue and endothelial cells representing a simplified model of energetic substrate metabolism in the visceral region was developed. The 3-way culture was shown to maintain glucose and fatty acid homeostasis in-vitro. Subsequently it was challenged with insulin and high glucose concentrations to simulate hyperglycaemia. The aim was to study the capacity of the 3-way culture to maintain or restore normal circulating glucose concentrations in response to insulin and to investigate the effects these conditions on other metabolites involved in glucose and lipid metabolism. The results show that the system’s metabolic profile changes dramatically in the presence of high concentrations of glucose, and that these changes are modulated by the presence of insulin. Furthermore, we observed an increase in E-selectin levels in hyperglycaemic conditions and increased IL-6 concentrations in insulin-free-hyperglycaemic conditions, indicating, respectively, endothelial injury and proinflammatory stress in the challenged 3-way system
Erratum: Hearing the Shape of the Ising Model with a Programmable Superconducting-Flux Annealer.
Erratum: Hearing the Shape of the Ising Model with a Programmable Superconducting-Flux Anneale
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