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1.
Phys Rev E ; 108(1-1): 014308, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37583232

RESUMO

We discuss the majority vote model coupled with scale-free networks and investigate its critical behavior. Previous studies point to a nonuniversal behavior of the majority vote model, where the critical exponents depend on the connectivity. At the same time, the effective dimension D_{eff} is unity for a degree distribution exponent 5/2<γ<7/2. We introduce a finite-size theory of the majority vote model for uncorrelated networks and present generalized scaling relations with good agreement with Monte Carlo simulation results. Our finite-size approach has two sources of size dependence: an external field representing the influence of the mass media on consensus formation and the scale-free network cutoff. The critical exponents are nonuniversal, dependent on the degree distribution exponent, precisely when 5/2<γ<7/2. For γ≥7/2, the model is in the same universality class as the majority vote model on Erdos-Rényi random graphs. However, for γ=7/2, the critical behavior includes additional logarithmic corrections.

2.
J Mol Model ; 29(7): 205, 2023 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-37294345

RESUMO

CONTEXT: The monoclinic L-histidine crystal is critical for protein structure and function and is also found in the myelin of brain nerve cells. This study numerically examines its structural, electronic, and optical properties. Our findings indicate that the L-histidine crystal has an insulating band gap of approximately 4.38 eV. Additionally, electron and hole effective masses range between 3.92[Formula: see text]-15.33[Formula: see text] and 4.16[Formula: see text]-7.53[Formula: see text], respectively. Furthermore, our investigation suggests that the L-histidine crystal is an excellent UV collector due to its strong optical absorption activity for photon energies exceeding 3.5 eV. METHODS: To investigate the structural, electronic, and optical properties of L-histidine crystals, we used the Biovia Materials Studio software to conduct Density Functional Theory (DFT) simulations as implemented in the CASTEP code. Our DFT calculations were performed using the generalized gradient approximation (GGA) as parameterized by the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional, with an additional dispersion energy correction (PBE [Formula: see text] TS) based on the model proposed by Tkatchenko and Scheffler to describe van der Waals interactions. Additionally, we employed the norm-conserving pseudopotential to treat core electrons.


Assuntos
Eletrônica , Histidina , Teoria da Densidade Funcional , Elétrons , Software
3.
Phys Rev E ; 105(3-1): 034105, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35428121

RESUMO

We define a stochastic reaction-diffusion process that describes a consensus formation in a nonsedentary population. The process is a diffusive version of the majority-vote model, where the state update follows two stages: In the first stage, spins are allowed to jump to a random neighbor node with probabilities D_{+} and D_{-} for the respective spin orientations, and in the second stage, the spins in the same node can change its values according to the majority-vote update rule. The model presents a consensus formation phase when the concentration is greater than a threshold value and a paramagnetic phase on the converse for equal diffusion probabilities, i.e., maintaining the inversion symmetry. Setting unequal diffusion probabilities for the respective spin orientations is the same as applying an external magnetic field. The system undergoes a discontinuous phase transition for concentrations higher than the critical threshold on the external field. The individuals that diffuse more dominate the stationary collective opinion.

4.
J Mol Model ; 27(5): 145, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33932166

RESUMO

In this work, we report a theoretical study of the structural, electronic, and optical properties of palmitic acid crystal in its C form under DFT calculations level. Palmitic acid is a fatty acid that constitutes the large majority of vegetable oils with recognized potential applications in medicine, pharmaceuticals, cosmetics technology, foods, and fuel. As a main result, we have found that the electronic bandstructure reveals an indirect gap given by 3.713 eV (E→B andE→Γ), as a main bandgap, while the secondary bandgaps found were 4.175 eV (γ1→Γ) and 4.172 eV (γ2→B). It behaves like a wide bandgap semiconductor, which points to potential applications in optoelectronic devices.

5.
Physica A ; 559: 125067, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32834437

RESUMO

The spreading of epidemics in complex networks has been a subject of renewed interest of several scientific branches. In this regard, we have focused our attention on the study of the susceptible-infected-susceptible (SIS) model, within a Monte Carlo numerical simulation approach, representing the spreading of epidemics in a clustered homophilic network. The competition between infection and recovery that drives the system either to an absorbing or to an active phase is analyzed. We estimate the static critical exponents ß ∕ ν , 1 ∕ ν and γ ∕ ν , through finite-size scaling (FSS) analysis of the order parameter ρ and its fluctuations, showing that they differ from those associated with the contact process on a scale-free network, as well as those predicted by the heterogeneous mean-field theory.

6.
J Mol Model ; 26(5): 100, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32297023

RESUMO

Nowadays, boron nitride has attracted a great deal of attention due to its physical (chemical) properties, facile synthesis, and experimental characterization, indicating great potential for industrial application. Based on this, we develop here a theoretical study on boron nitride nanoflakes built-up from hexagonal boron nitride nanosheets exhibiting hexagonal, rectangular, and triangular shapes. In order to investigate geometry effects such as those due to the presence of armchair and zigzag edges and distinct shapes, we analyzed their properties from both classical and quantum viewpoints. Using classical molecular dynamics calculations, we show that the nanosheets preserve their structural stability at high temperatures, while DFT calculations demonstrate HOMO-LUMO energy gap variation within the theoretical energy gaps of h-BN in bulk and 2D crystals. Besides that, we have also found that boron nitride nanoflakes structures have spatially symmetrical spin densities.

7.
Artigo em Inglês | MEDLINE | ID: mdl-23848628

RESUMO

We introduce a superdiffusive one-dimensional epidemic process model on which infection spreads through a contact process. Healthy (A) and infected (B) individuals can jump with distinct probabilities D(A) and D(B) over a distance ℓ distributed according to a power-law probability P(ℓ)[proportionality]1/ℓ(µ). For µ≥3 the propagation is equivalent to diffusion, while µ<3 corresponds to Lévy flights. In the D(A)>D(B) diffusion regime, field-theoretical results have suggested a first-order transition, a prediction not supported by several numerical studies. An extensive numerical study of the critical behavior in both the diffusive (µ≥3) and superdiffusive (µ<3) D(A)>D(B) regimes is also reported. We employed a finite-size scaling analysis to obtain the critical point as well as the static and dynamic critical exponents for several values of µ. All data support a second-order phase transition with continuously varying critical exponents which do not belong to the directed percolation universality class.


Assuntos
Doenças Transmissíveis/epidemiologia , Surtos de Doenças/estatística & dados numéricos , Transmissão de Doença Infecciosa/estatística & dados numéricos , Modelos Estatísticos , Animais , Simulação por Computador , Difusão , Humanos , Incidência
8.
Trop Geogr Med ; 23(1): 89-101, 1971 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-5573585

RESUMO

PIP: Jet injection was 1st introduced into Brazil's smallpox eradication program in 1965 following field studies in Amapa Territory that confirmed the effectiveness of this technique. Between January 27-February 15, 1965, vaccination teams vaccinated 53,654 people in this territory, representing 89% of the target population. Local personnel with limited training were able to operate the jet injectors with few problems. Vaccination take rates were significantly higher both in primary vaccinees and revaccinees when the jet injectors as opposed to the conventional multiple pressure technique was used. Take rates ranged from 81-90% in the various villages, and there were only 2 complications reported. An average of over 600 vaccinations could be performed per hour with jet injection and total man-hours expended were 1/3 the number involved in the traditional technique. The cost per vaccination was estimated to be US$0.022 for the jet injector technique compared with 0.067 for the multiple pressure approach. Overall, the experience in Amapa Territory indicates that jet injection has obvious advantages, including a reduction in manpower needs, a reduction in transportation needs, increased efficiency, and a reduction in vaccine needs. For best use of the equipment, priority should be given to urban areas.^ieng


Assuntos
Injeções/instrumentação , Vacina Antivariólica , Varíola/prevenção & controle , Vacinação/instrumentação , Brasil , Custos e Análise de Custo , Mão de Obra em Saúde , Humanos , Injeções Intradérmicas , População Rural , População Urbana
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