20,445 research outputs found
Phenomenological study on the significance of the scalar potential and Lamb shift
We indicated in our previous work that for QED the contributions of the
scalar potential which appears at the loop level is much smaller than that of
the vector potential and in fact negligible. But the situation may be different
for QCD, one reason is that the loop effects are more significant because
is much larger than , and secondly the non-perturbative QCD
effects may induce the scalar potential. In this work, we phenomenologically
study the contribution of the scalar potential to the spectra of charmonia.
Taking into account both vector and scalar potentials, by fitting the well
measured charmonia spectra, we re-fix the relevant parameters and test them by
calculating other states of the charmonia family. We also consider the role of
the Lamb shift and present the numerical results with and without involving the
Lamb shift
Generation of two-photon EPR and Wstates
In this paper we present a scheme for generation of two-photon EPR and W
states in the cavity QED context. The scheme requires only one three-level
Rydberg atom and two or three cavities. The atom is sent to interact with
cavities previously prepared in vacuum states, via two-photon process. An
appropriate choice of the interaction times one obtains the mentioned state
with maximized fidelities. These specific times and the values of success
probability and fidelity are discussed.Comment: 4 pages, 5 figure
Aplicação do building information modeling (bim) em projetos de infraestrutura nas fases pre-completion e/ou post-completion.
Anualmente, o Governo Federal gasta bilhÔes de reais em obras de infraestrutura e estas por sua vez fazem parte e são essenciais para, por exemplo, mitigar as condiçÔes de habitabilidade.
Contribuindo na ampliação dos horizontes da gestão de riscos na atuação governamental para a gestão eficiente; de promover a atuação sobre as incertezas; e ainda de contribuir no ùmbito do Governo federal na disseminação da tecnologia BIM, tem-se nesse artigo a anålise de projetos de infraestrutura nas fases pre-completion e/ou post-completion com a consequente proposição para que as açÔes governamentais cheguem ao beneficiårio no tempo e medidas certas.
Ă o paradigma de "olhar para a frente". As atividades de operação e manutenção representam mais de 95% do tempo dos empreendimentos de infraestrutura, hĂĄ um elevado peso das vantagens trazidas pelo BIM, onde as inerentes ao projeto e/ou obra permitem a implantação de um sistema de gestĂŁo integrada e automatizada das atividades de operação e manutenção alĂ©m de atividades de Auditoria, Controle e Fiscalização em todo o ciclo de vida.28 p.PolĂticas de Infraestrutur
Thermodynamics of Surfactants, Block Copolymers and Their Mixtures in Water: The Role of the Isothermal Calorimetry
The thermodynamics of conventional surfactants, block copolymers and their mixtures in water was described to the light of the enthalpy function. The two methodologies, i.e. the vanât Hoff approach and the isothermal calorimetry, used to determine the enthalpy of micellization of pure surfactants and block copolymers were described. The vanât Hoff method was critically discussed. The aqueous copolymer+surfactant mixtures were analyzed by means of the isothermal titration calorimetry and the enthalpy of transfer of the copolymer from the water to the aqueous surfactant solutions. Thermodynamic models were presented to show the procedure to extract straightforward molecular insights from the bulk properties
Prevalence of long face pattern in brazilian individuals of different ethnic backgrounds
Conclusions: Black individuals had greater prevalence of long face pattern, followed by Brown, White and Yellow individuals. The prevalence of long face pattern was 14.06% in which 13.39% and 0.68% belonged to moderate and severe subtypes, respectively.Objective: The long face pattern is a facial deformity with increased anterior total facial height due to vertical excess of the lower facial third. Individuals with long face may present different degrees of severity in vertical excess, as well as malocclusions that are difficult to manage. The categorization of vertical excess is useful to determine the treatment prognosis. This survey assessed the distribution of ethnically different individuals with vertical excess according to three levels of severity and determined the prevalence of long face pattern. Material and Methods: The survey was comprised of 5,020 individuals of Brazilian ethnicity (2,480 females and 2,540 males) enrolled in middle schools in Bauru-SP, Brazil. The criterion for inclusion of individuals with vertically impaired facial relationships was based on lip incompetence, evaluated under natural light, in standing natural head position with the lips at rest. Once identified, the individuals were classified into three subtypes according to the severity: mild, moderate, and severe. Then the pooled sample was distributed according to ethnical background as White (Caucasoid), Black (African descent), Brown (mixed descent), Yellow (Asian descent) and Brazilian Indian (Brazilian native descent). The Chi-square (Ï2 ) test was used (p<0.05) to compare the frequency ratios of individuals with vertically impaired facial relationships in the total sample and among different ethnicities, according to the three levels of severity. Results: The severe subtype was rare, except in Black individuals (7.32%), who also presented the highest relative frequency (45.53%) of moderate subtype, followed by Brown individuals (43.40%). In the mild subtype, Yellow (68.08%) and White individuals (62.21%) showed similar and higher relative frequency values.\ud
Conclusions: Black individuals had greater prevalence of long face pattern, followed by Brown, White and Yellow individuals. The prevalence of long face pattern was 14.06% in which 13.39% and 0.68% belonged to moderate and severe subtypes, respectively
A disk-wind model with correct crossing of all MHD critical surfaces
The classical Blandford & Payne (1982) model for the magnetocentrifugal
acceleration and collimation of a disk-wind is revisited and refined. In the
original model, the gas is cold and the solution is everywhere subfast
magnetosonic. In the present model the plasma has a finite temperature and the
self-consistent solution of the MHD equations starts with a subslow
magnetosonic speed which subsequently crosses all critical points, at the slow
magnetosonic, Alfven and fast magnetosonic separatrix surfaces. The superfast
magnetosonic solution thus satisfies MHD causality. Downstream of the fast
magnetosonic critical point the poloidal streamlines overfocus towards the axis
and the solution is terminated. The validity of the model to disk winds
associated with young stellar objects is briefly discussed. ~Comment: 13 pages, MNRAS accepted for publicatio
Active control of qubit-qubit entanglement evolution
In this work, we propose a scheme to design the time evolution of the entropy
of entanglement between two qubits. It is shown an explicit accurate solution
for the inverse problem of determining the time dependence of the coupling
constant from a user-defined dynamical entanglement function. Such an active
control of entanglement can be implemented in many different physical
implementations of coupled qubits, and we briefly comment on the use of
interacting flux qubits.Comment: Author added, Expanded version, 10 figure
Electronic structure of triangular, hexagonal and round graphene flakes near the Fermi level
The electronic shell structure of triangular, hexagonal and round graphene
quantum dots (flakes) near the Fermi level has been studied using a
tight-binding method. The results show that close to the Fermi level the shell
structure of a triangular flake is that of free massless particles, and that
triangles with an armchair edge show an additional sequence of levels ("ghost
states"). These levels result from the graphene band structure and the plane
wave solution of the wave equation, and they are absent for triangles with an
zigzag edge. All zigzag triangles exhibit a prominent edge state at the Fermi
level, and few low-energy conduction electron states occur both in triangular
and hexagonal flakes due to symmetry reasons. Armchair triangles can be used as
building blocks for other types of flakes that support the ghost states. Edge
roughness has only a small effect on the level structure of the triangular
flakes, but the effect is considerably enhanced in the other types of flakes.
In round flakes, the states near the Fermi level depend strongly on the flake
radius, and they are always localized on the zigzag parts of the edge
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