4,091 research outputs found
Free Minimization of the Fundamental Measure Theory Functional: Freezing of Parallel Hard Squares and Cubes
Due to remarkable advances in colloid synthesis techniques, systems of
squares and cubes, once an academic abstraction for theorists and simulators,
are nowadays an experimental reality. By means of a free minimization of the
free-energy functional, we apply Fundamental Measure Theory to analyze the
phase behavior of parallel hard squares and hard cubes. We compare our results
with those obtained by the traditional approach based on the Gaussian
parameterization, finding small deviations and good overall agreement between
the two methods. For hard squares our predictions feature at intermediate
packing fraction a smectic phase, which is however expected to be unstable due
to thermal fluctuations. This implies that for hard squares the theory predicts
either a vacancy-rich second-order transition or a vacancy-poor weakly
first-order phase transition at higher density. In accordance with previous
studies, a second-order transition with a high vacancy concentration is
predicted for hard cubes
WIMPs search by scintillators: possible strategy for annual modulation search with large-mass highly-radiopure NaI(Tl)
The DAMA experiments are running deep underground in the Gran Sasso National
Laboratory. Several interesting results have been achieved so far. Here a
maximum likelihood method to search for the WIMP annual modulation signature is
discussed and applied to a set of preliminary test data collected with large
mass highly radiopure NaI(Tl) detectors. Various related technical arguments
are briefly addressed.Comment: 6 pages, 4 figures, LaTex. Contributed paper to TAUP97; to appear in
the Proceeding
Density Functional Theory for Chiral Nematic Liquid Crystals
Even though chiral nematic phases were the first liquid crystals
experimentally observed more than a century ago, the origin of the
thermodynamic stability of cholesteric states is still unclear. In this Letter
we address the problem by means of a novel density functional theory for the
equilibrium pitch of chiral particles. When applied to right-handed hard
helices, our theory predicts an entropy-driven cholesteric phase, which can be
either right- or left-handed, depending not only on the particle shape but also
on the thermodynamic state. We explain the origin of the chiral ordering as an
interplay between local nematic alignment and excluded-volume differences
between left- and right-handed particle pairs
SWINE WASTE PHYTOREMEDIATION USING DUCKWEED (Landoltia punctata, Les & Crawford) IN A FULL SCALE PLANT
Banner Apresentado em Congresso: 11th International Conference, Heraklion, Crete, Greece PhytotechnologiesThe large amount of nitrogen and phosphorous compounds found in pig manure has caused ecological imbalances, with eutrophication of major river basins in the producing regions. Therefore, the aquatic macrophytes group named duckweeds (Araceae; Lemnoideae) have been successfully used for phytoextraction and rhizodegradation of nutrient and heavy metals from swine waste, generating further a biomass with high protein content. The present study evaluated the phytoremediation of nitrogen and phosphorus from swine waste using the duckweed Landoltia punctata and also their protein biomass production as by-product
Depletion-induced biaxial nematic states of boardlike particles
With the aim of investigating the stability conditions of biaxial nematic
liquid crystals, we study the effect of adding a non-adsorbing ideal depletant
on the phase behavior of colloidal hard boardlike particles. We take into
account the presence of the depletant by introducing an effective depletion
attraction between a pair of boardlike particles. At fixed depletant fugacity,
the stable liquid crystal phase is determined through a mean-field theory with
restricted orientations. Interestingly, we predict that for slightly elongated
boardlike particles a critical depletant density exists, where the system
undergoes a direct transition from an isotropic liquid to a biaxial nematic
phase. As a consequence, by tuning the depletant density, an easy experimental
control parameter, one can stabilize states of high biaxial nematic order even
when these states are unstable for pure systems of boardlike particles
DAMA annual modulation effect and asymmetric mirror matter
The long-standing model-independent annual modulation effect measured by DAMA
Collaboration is examined in the context of asymmetric mirror dark matter,
assuming that dark atoms interact with target nuclei in the detector via
kinetic mixing between mirror and ordinary photons, both being massless. The
relevant ranges for the kinetic mixing parameter are obtained taking into
account various existing uncertainties in nuclear and particle physics
quantities as well as characteristic density and velocity distributions of dark
matter in different halo models.Comment: 27 pages, 5 figures, 2 tables; version in publication on Eur. Phys.
J.
Observations of annual modulation in direct detection of relic particles and light neutralinos
The long-standing model-independent annual modulation effect measured by the
DAMA Collaboration, which fulfills all the requirements of a dark matter annual
modulation signature, and the new result by the CoGeNT experiment that shows a
similar behavior are comparatively examined under the hypothesis of a dark
matter candidate particle interacting with the detectors' nuclei by a coherent
elastic process. The ensuing physical regions in the plane of the dark
matter-particle mass versus the dark matter-particle nucleon cross-section are
derived for various galactic halo models and by taking into account the impact
of various experimental uncertainties. It is shown that the DAMA and the CoGeNT
regions agree well between each other and are well fitted by a supersymmetric
model with light neutralinos which satisfies all available experimental
constraints, including the most recent results from CMS and ATLAS at the CERN
Large Hadron Collider.Comment: 13 pages, 7 figure
Mutation of Directed Graphs -- Corresponding Regular Expressions and Complexity of Their Generation
Directed graphs (DG), interpreted as state transition diagrams, are
traditionally used to represent finite-state automata (FSA). In the context of
formal languages, both FSA and regular expressions (RE) are equivalent in that
they accept and generate, respectively, type-3 (regular) languages. Based on
our previous work, this paper analyzes effects of graph manipulations on
corresponding RE. In this present, starting stage we assume that the DG under
consideration contains no cycles. Graph manipulation is performed by deleting
or inserting of nodes or arcs. Combined and/or multiple application of these
basic operators enable a great variety of transformations of DG (and
corresponding RE) that can be seen as mutants of the original DG (and
corresponding RE). DG are popular for modeling complex systems; however they
easily become intractable if the system under consideration is complex and/or
large. In such situations, we propose to switch to corresponding RE in order to
benefit from their compact format for modeling and algebraic operations for
analysis. The results of the study are of great potential interest to mutation
testing
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