647,153 research outputs found
Boojums and the Shapes of Domains in Monolayer Films
Domains in Langmuir monolayers support a texture that is the two-dimensional
version of the feature known as a boojum. Such a texture has a quantifiable
effect on the shape of the domain with which it is associated. The most
noticeable consequence is a cusp-like feature on the domain boundary. We report
the results of an experimental and theoretical investigation of the shape of a
domain in a Langmuir monolayer. A further aspect of the investigation is the
study of the shape of a ``bubble'' of gas-like phase in such a monolayer. This
structure supports a texture having the form of an inverse boojum. The
distortion of a bubble resulting from this texture is also studied. The
correspondence between theory and experiment, while not perfect, indicates that
a qualitative understanding of the relationship between textures and domain
shapes has been achieved.Comment: replaced with published version, 10 pages, 13 figures include
Understanding social machines
The framework introduced in this paper aims to reflect the characteristics that social machines have been described to have. The framework uses a mixed methods approach underpinned by social theory to provide a detailed and rich understanding of the socio-technical nature of a social machine. The strength of this lies in the diversity of the data being used; whilst the quantitative approach can provide mathematical rigor to the structure and properties of the networks and appreciate its scale, the qualitative approach seeks to examine the 'social relations', and the context to how the social machine is enabling humans and technologies to interact and shape each other. Like many studies using empirical-based research, this framework takes advantage of the complementary nature that mixed methods offers, and pushes it further by using an analytical socio-technical lens.<br/
Interplay of paramagnetic, orbital and impurity effects on the phase transition of a normal metal to superconducting state
We derive the generalized Ginzburg-Landau free energy functional for
conventional and unconventional singlet superconductors in the presence of
paramagnetic, orbital and impurity effects. Within the mean field theory, we
determine the criterion for appearence of the non uniform
(Fulde-Ferrell-Larkin-Ovchinnikov) superconducting state, with vortex lattice
structure and additional modulation along the magnetic field. We also discuss
the possible change of the order of transition from normal to superconducting
state. We find that the superconducting phase diagram is very sensitive to
geometrical effects such as the nature of the order parameter and the shape of
the Fermi surface. In particular, we obtain the qualitative phase diagrams for
three-dimensional isotropic s-wave superconductors and in quasi two-dimensional
d-wave superconductors under magnetic field perpendicular to the conducting
layers.
In addition, we determine the criterion for instability toward non uniform
superconducting state in s-wave superconductors in the dirty limit.Comment: 15 pages, 4 figure
Using structural complexity to explain decision-making on corporate responsibility
PhD ThesisIntra-organizational factors are an important line of inquiry to improve the explanation of
corporate social responsibility (CSR) behavior in current theory and management concepts.
Contributions from organizational behavior literature were used in this thesis to orient the
analysis to the company’s structure in order to provide alternative explanations as to ‘why’
and ‘how’ companies addressed social responsibility issues and activities. Qualitative
methods were employed to investigate the structure/decision relationship among a sample of
decision processes of multinational business organizations. Conclusions suggest that social
responsibility issues and activities can be treated contextually by the company, and its
complexity can influence and shape the development of alternatives to address the issues and
activities
Zero-dimensional limit of the two-dimensional Lugiato-Lefever equation
We study effects of tight harmonic-oscillator confinement on the
electromagnetic field in a laser cavity by solving the two-dimensional
Lugiato-Lefever (2D LL) equation, taking into account self- focusing or
defocusing nonlinearity, losses, pump, and the trapping potential. Tightly
confined (quasi-zero-dimensional) optical modes (pixels), produced by this
model, are analyzed by means of the variational approximation, which provides a
qualitative picture of the ensuing phenomena. This is followed by systematic
simulations of the time-dependent 2D LL equation, which reveal the shape,
stability, and dynamical behavior of the resulting localized patterns. In this
way, we produce stability diagrams for the expected pixels. Then, we consider
the LL model with the vortical pump, showing that it can produce stable pixels
with embedded vorticity (vortex solitons) in remarkably broad sta- bility
areas. Alongside confined vortices with the simple single-ring structure, in
the latter case the LL model gives rise to stable multi-ring states, with a
spiral phase field. In addition to the numeri- cal results, a qualitatively
correct description of the vortex solitons is provided by the Thomas-Fermi
approximation.Comment: 11 pages, 15 figures, Eur. Phys. Journal D, in press (Topical Issue
"Theory and Applications of the Lugiato-Lefever Equation"
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