1,273 research outputs found
Interaction between vortices in models with two order parameters
The interaction energy and force between widely separated strings is analyzed
in a field theory having applications to superconducting cosmic strings, the
SO(5) model of high-temperature superconductivity, and solitons in nonlinear
optics. The field theory has two order parameters, one of which is broken in
the vacuum (giving rise to strings), the other of which is unbroken in the
vacuum but which could nonetheless be broken in the core of the string. If this
does occur, there is an effect on the energetics of widely separated strings.
This effect is important if the length scale of this second order parameter is
longer than that of the other fields in the problem.Comment: 11 pages, 3 figures. Minor changes in the text. Accepted for
publication in Phys. Rev.
Fluid Dynamics of Relativistic Quantum Dust
The microscopic transport equations for free fields are solved using the
Schwinger function. Thus, for general initial conditions, the evolution of the
energy-momentum tensor is obtained, incorporating the quantum effects exactly.
The result for relativistic fermions differs from classical hydrodynamics,
which is illustrated for Landau and Bjorken type initial conditions in this
model of exploding primordial matter. Free fermions behave like classical dust
concerning hydrodynamic observables. However, quantum effects which are present
in the initial state are preserved.Comment: 5 pages; LaTe
Multiple-Scale Analysis of the Quantum Anharmonic Oscillator
Conventional weak-coupling perturbation theory suffers from problems that
arise from resonant coupling of successive orders in the perturbation series.
Multiple-scale perturbation theory avoids such problems by implicitly
performing an infinite reordering and resummation of the conventional
perturbation series. Multiple-scale analysis provides a good description of the
classical anharmonic oscillator. Here, it is extended to study the Heisenberg
operator equations of motion for the quantum anharmonic oscillator. The
analysis yields a system of nonlinear operator differential equations, which is
solved exactly. The solution provides an operator mass renormalization of the
theory.Comment: 12 pages, Revtex, no figures, available through anonymous ftp from
ftp://euclid.tp.ph.ic.ac.uk/papers/ or on WWW at
http://euclid.tp.ph.ic.ac.uk/Papers/papers_95-6_.htm
In vitro cytocompatibility evaluation of poly(DL-lactic acid) scaffolds loaded with minocycline and voriconazole addressing osteomyelitis
Osteomyelitis or bone infection is an acute or chronic inflammatory process involving the bone and its structures, secondary to infection with pyogenic organisms, such as bacteria and fungi. Considering the associated high patient economic burden, morbidity, and mortality, it is essential to develop novel strategies for osteomyelitis management. Porous scaffolds based on biomaterials may locally deliver high concentrations of antibiotics, an effective strategy in eradicating bone infection. When incorporating bioactive bioglasses and bioresorbable polymers like poly(DL-lactic acid) (PDLLA), these structures exhibit biosafety, biodegradability, and the expected global structure to promote cell expansion and cell differentiation, being critical to consider and evaluate their biocompatibility compliance. As the encapsulation of more than one active pharmaceutical ingredient is an attractive approach, the present study focuses on the cytocompatibility evaluation of an innovative system based on the dual delivery of two antimicrobials, an antibiotic that enhances bone formation, minocycline (MH), and an antifungal agent with a broad spectrum of activity, voriconazole (VCZ), aiming bone infection therapeutics. Scaffolds were prepared by solvent casting/particulate leaching techniques and functionalized with bioglass. The scaffolds produced were adsorbed with 0.5 or 0.1 mg/mL of minocycline and also with 0.1 mg/mL of voriconazole. To test the bio-functionality and the biological safety of scaffolds, in vitro cell assays were achieved employing the MG-63 cell line (ATCC® CRL-1427TM human osteoblast cell line). The AlamarBlue® assay was used to measure cell proliferation in the scaffold. As osteoblast differentiation markers, the following were determined: alkaline phosphatase activity and mineralization using Alizarin red assay, an indicator of in vitro bone formation. All scaffolds sustained the proliferation of metabolically active cells, nonetheless, scaffolds adsorbed with the highest concentration of MH (0.5 mg/mL) presented a significant (p<0.05) cytotoxic effect. Matrix maturation assays supported early osteoblasts differentiation and the osteoinductive role of minocycline described in the literature was also highlighted. Matrix mineralization analysis showed the highest value associated with scaffolds with both antimicrobials adsorbed. Once the described scaffolds enhanced osteoblasts' differentiation, and matrix mineralization and evidenced no cytotoxic effects, they come to light as an auspicious alternative for local antimicrobial therapy addressing osteomyelitis prevention and therapeutics.info:eu-repo/semantics/publishedVersio
Density-dependence of functional development in spiking cortical networks grown in vitro
During development, the mammalian brain differentiates into specialized
regions with distinct functional abilities. While many factors contribute to
functional specialization, we explore the effect of neuronal density on the
development of neuronal interactions in vitro. Two types of cortical networks,
dense and sparse, with 50,000 and 12,000 total cells respectively, are studied.
Activation graphs that represent pairwise neuronal interactions are constructed
using a competitive first response model. These graphs reveal that, during
development in vitro, dense networks form activation connections earlier than
sparse networks. Link entropy analysis of dense net- work activation graphs
suggests that the majority of connections between electrodes are reciprocal in
nature. Information theoretic measures reveal that early functional information
interactions (among 3 cells) are synergetic in both dense and sparse networks.
However, during later stages of development, previously synergetic
relationships become primarily redundant in dense, but not in sparse networks.
Large link entropy values in the activation graph are related to the domination
of redundant ensembles in late stages of development in dense networks. Results
demonstrate differences between dense and sparse networks in terms of
informational groups, pairwise relationships, and activation graphs. These
differences suggest that variations in cell density may result in different
functional specialization of nervous system tissue in vivo.Comment: 10 pages, 7 figure
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