78 research outputs found
Massive Gauge Axion Fields
A gauge invariant formulation for the massive axion is considered. The axion
acquires mass through a topological term which couples a (pseudo)scalar and a
third rank antisymmetric tensor. Duality, local and canonical equivalences with
the non-gauge invariant proposal are established. The supersymmetric version of
the gauge invariant model is constructed.Comment: Final version. New references adde
Abelian Duality
We show that on three-dimensional Riemannian manifolds without boundaries and
with trivial first real de Rham cohomology group (and in no other dimensions)
scalar field theory and Maxwell theory are equivalent: the ratio of the
partition functions is given by the Ray-Singer torsion of the manifold. On the
level of interaction with external currents, the equivalence persists provided
there is a fixed relation between the charges and the currents.Comment: 11 pages, LaTeX, no figures, a reference added, submitted to Phys.
Rev.
Planetary and Light Motions From Newtoinian Theory: An Amusing Exercise
We attempt to see how closely we can formally obtain the planetary and light
path equations of General Relativity by employing certain operations on the
familiar Newtonian equation. This article is intended neither as an alternative
to nor as a tool for grasping Einstein's General Relativity. Though the
exercise is understandable by readers at large, it is especially recommended to
the teachers of Relativity for an appreciative understanding of its peculiarity
as well as its pedagogical value in the teaching of differential equations.Comment: 7 page
Induced Parity Breaking Term in Arbitrary Odd Dimensions at Finite Temperature
We calculate the exact parity odd part of the effective action
() for massive Dirac fermions in 2d+1 dimensions at finite
temperature, for a certain class of gauge field configurations. We consider
first Abelian external gauge fields, and then we deal with the case of a
non-Abelian gauge group containing an Abelian U(1) subgroup. For both cases, it
is possible to show that the result depends on topological invariants of the
gauge field configurations, and that the gauge transformation properties of
depend only on those invariants and on the winding number
of the gauge transformation.Comment: 10 pages, revtex, no figure
BF models, Duality and Bosonization on higher genus surfaces
The generating functional of two dimensional field theories coupled to
fermionic fields and conserved currents is computed in the general case when
the base manifold is a genus g compact Riemann surface. The lagrangian density
is written in terms of a globally defined 1-form and a
multi-valued scalar field . Consistency conditions on the periods of
have to be imposed. It is shown that there exist a non-trivial dependence of
the generating functional on the topological restrictions imposed to . In
particular if the periods of the field are constrained to take values , with any integer, then the partition function is independent of the
chosen spin structure and may be written as a sum over all the spin structures
associated to the fermions even when one started with a fixed spin structure.
These results are then applied to the functional bosonization of fermionic
fields on higher genus surfaces. A bosonized form of the partition function
which takes care of the chosen spin structure is obtainedComment: 17 page
Image informatics strategies for deciphering neuronal network connectivity
Brain function relies on an intricate network of highly dynamic neuronal connections that rewires dramatically under the impulse of various external cues and pathological conditions. Among the neuronal structures that show morphologi- cal plasticity are neurites, synapses, dendritic spines and even nuclei. This structural remodelling is directly connected with functional changes such as intercellular com- munication and the associated calcium-bursting behaviour. In vitro cultured neu- ronal networks are valuable models for studying these morpho-functional changes. Owing to the automation and standardisation of both image acquisition and image analysis, it has become possible to extract statistically relevant readout from such networks. Here, we focus on the current state-of-the-art in image informatics that enables quantitative microscopic interrogation of neuronal networks. We describe the major correlates of neuronal connectivity and present workflows for analysing them. Finally, we provide an outlook on the challenges that remain to be addressed, and discuss how imaging algorithms can be extended beyond in vitro imaging studies
Evaluation of methods for detection of fluorescence labeled subcellular objects in microscope images
<p>Abstract</p> <p>Background</p> <p>Several algorithms have been proposed for detecting fluorescently labeled subcellular objects in microscope images. Many of these algorithms have been designed for specific tasks and validated with limited image data. But despite the potential of using extensive comparisons between algorithms to provide useful information to guide method selection and thus more accurate results, relatively few studies have been performed.</p> <p>Results</p> <p>To better understand algorithm performance under different conditions, we have carried out a comparative study including eleven spot detection or segmentation algorithms from various application fields. We used microscope images from well plate experiments with a human osteosarcoma cell line and frames from image stacks of yeast cells in different focal planes. These experimentally derived images permit a comparison of method performance in realistic situations where the number of objects varies within image set. We also used simulated microscope images in order to compare the methods and validate them against a ground truth reference result. Our study finds major differences in the performance of different algorithms, in terms of both object counts and segmentation accuracies.</p> <p>Conclusions</p> <p>These results suggest that the selection of detection algorithms for image based screens should be done carefully and take into account different conditions, such as the possibility of acquiring empty images or images with very few spots. Our inclusion of methods that have not been used before in this context broadens the set of available detection methods and compares them against the current state-of-the-art methods for subcellular particle detection.</p
Toxicity of wine effluents and assessment of a depuration system for their control: assay with tadpoles of Rhinella arenarum (BUFONIDAE)
We evaluated the toxicity of the winery effluent and the efficiency of a symbiotic depuration system by means an experiment with Rhinella arenarum tadpoles. The studied effluent was taken from warehouses during the cleaning season. These effluents subsequently subjected to the purification treatment under evaluation. The effluent samples differentiated into two treatment levels: ârawâ where the effluent was evaluated with field conditions and âtreatedâ where the effluent was previously filtered with the symbiotic depuration system. The results of the bioassays compared with the physicochemical parameters determined in the effluent samples. The lethal response had a clear-cut correspondence with the effluent quality assessed utilizing physicochemical parameters. In all cases, dilution of the samples resulted in a significant reduction of their toxicity. It concluded that (a) winery effluents could be harmful to tadpoles of R. arenarum, (b) the symbiotic purification system used to treat wine effluents it would produce a significant reduction in the contaminant levels of the effluent. However, this reduction in contaminant levels does not provide sufficient safety for the release of the effluents into the environment.Fil: Navas Romero, Ana Laura. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Ăridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Ăridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Ăridas; ArgentinaFil: Herrera Moratta, Mario Andres. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Ăridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Ăridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Ăridas; ArgentinaFil: RodrĂguez, MarĂa Rosa. Universidad Nacional de San Juan. Facultad de IngenierĂa; ArgentinaFil: Quiroga, Lorena Beatriz. Universidad Nacional de San Juan. Facultad de FilosofĂa, Humanidades y Artes. Instituto de Ciencias BĂĄsicas; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Juan; ArgentinaFil: Echegaray, Marcelo Eduardo. Universidad Nacional de San Juan. Facultad de IngenierĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Juan; ArgentinaFil: Sanabria, Eduardo Alfredo. Universidad Nacional de San Juan. Facultad de FilosofĂa, Humanidades y Artes. Instituto de Ciencias BĂĄsicas; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Juan; Argentin
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