21,069 research outputs found
Shear-melting of a hexagonal columnar crystal by proliferation of dislocations
A hexagonal columnar crystal undergoes a shear-melting transition above a
critical shear rate or stress. We combine the analysis of the shear-thinning
regime below the melting with that of synchrotron X-ray scattering data under
shear and propose the melting to be due to a proliferation of dislocations,
whose density is determined by both techniques to vary as a power law of the
shear rate with a 2/3 exponent, as expected for a creep model of crystalline
solids. Moreover, our data suggest the existence under shear of a line hexatic
phase, between the columnar crystal and the liquid phase
BEC-BCS crossover in a cold and magnetized two color NJL model
The BEC-BCS crossover for a NJL model with diquark interactions is studied in
the presence of an external magnetic field. Particular attention is paid to
different regularization schemes used in the literature. A thorough comparison
of results is performed for the case of a cold and magnetized two-color NJL
model. According to our results, the critical chemical potential for the BEC
transition exhibits a clear inverse magnetic catalysis effect for magnetic
fields in the range . As for the BEC-BCS
crossover, the corresponding critical chemical potential is very weakly
sensitive to magnetic fields up to , showing a much smaller
inverse magnetic catalysis as compared to the BEC transition, and displays a
strong magnetic catalysis from this point on.Comment: 15 pages, 8 figures; v2 PRD versio
The role of Portuguese companies in the development of corporate strategies: case study
Strategy assumes a significant role in the managerial field concerning three levels of activity- corporate, business and functional. In academic terms, corporate strategy refers to a set of conceptualized strategies with distinct purposes. However, how does one make a decision regarding corporate strategies? Which forces, internal or external, are capable of influencing it? Are these strategies equally perceived? There is a gap of perception between the academic and business settings. Academically, corporate strategies are only explored towards their aim. However, under real conditions, companies are exposed to further features. Thus, the present investigation aims to develop an understanding about how distinct companies perceive strategy at the corporate level. This article relies on data from 30 companies, with a variety of industries. The results include valuable information regarding the main drivers of the decision behind corporate strategies and the dissimilarities associated to the perception of strategy at the corporate level.info:eu-repo/semantics/acceptedVersio
Medium-modified evolution of multiparticle production in jets in heavy-ion collisions
The energy evolution of medium-modified average multiplicities and
multiplicity fluctuations in quark and gluon jets produced in heavy-ion
collisions is investigated from a toy QCD-inspired model. In this model, we use
modified splitting functions accounting for medium-enhanced radiation of gluons
by a fast parton which propagates through the quark gluon plasma. The leading
contribution of the standard production of soft hadrons is found to be enhanced
by the factor while next-to-leading order (NLO) corrections are
suppressed by , where the nuclear parameter accounts for
the induced-soft gluons in the hot medium. The role of next-to-next-to-leading
order corrections (NNLO) is studied and the large amount of medium-induced soft
gluons is found to drastically affect the convergence of the perturbative
series. Our results for such global observables are cross-checked and compared
with their limits in the vacuum and a new method for solving the second
multiplicity correlator evolution equations is proposed.Comment: 21 pages and 8 figures, typo corrections, references adde
Capabilities and limitations of a new thermal finite volume model for the evaluation of laser-induced thermo-mechanical retinal damage
Many experimental studies focus on the physical damage mechanisms of short-term exposure to laser radiation. In the nanosecond (ns) pulse range, damage
in the Retinal Pigment Epithelium (RPE) will most likely occur at threshold levels due to bubble formation at the surface of the absorbing melanosome. The
energy uptake of the melanosomes is one key aspect in modeling the bubble formation and damage thresholds. This work presents a thermal finite volume model
for the investigation of rising temperatures and the temperature distribution of irradiated melanosomes. The model takes the different geometries and thermal
properties of melanosomes into account, such as the heat capacity and thermal conductivity of the heterogeneous absorbing melanosomes and the surrounding
tissue. This is the first time the size and shape variations on the melanosomes‘ thermal behavior are considered. The calculations illustrate the effect of the
geometry on the maximum surface temperature of the irradiated melanosome and the impact on the bubble formation threshold. A comparison between the
calculated bubble formation thresholds and the RPE cell damage thresholds within a pulse range of 3 to 5000 ns leads to a mean deviation of = 22 mJ ∕ cm2
with a standard deviation of = 21 mJ ∕ cm2. The best results are achieved between the simulation and RPE cell damage thresholds for pulse durations close to
the thermal confinement time of individual melanosomes
Avaliação de caracterÃsticas agronômicas e de produção de abóbora em áreas de agricultura familiar na região Agreste de Sergipe.
Integrated approach on solar drying, pilot convective drying and microstructural changes
Solar drying of foods is an old technique, still used nowadays. Nevertheless, the mathematical approach of the complex phenomena involved is not completely integrated. Drawbacks appear in modelling heat transport, specially related to the huge variability of meteorological factors. The great dependence of the heat and mass transfer model parameters on water content is also frequently forgotten. Macroscopic changes (e.g. shrinkage) that occur during drying processes, are usually not considered in mass transfer equations, also affecting the predictive ability of the models. The objective of this work was to develop the mathematical basis and considerations for integrating heat and mass transfer phenomena,
taking into consideration macroscopic changes and their correlation to changes at microscopic level (e.g. cellular shrinkage),
that might occur during solar drying of grapes
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