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Search Results: 1 - 10 of 505597 matches for " Bezerra de Mello E.R. "
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Physics in the Global Monopole Spacetime
Bezerra de Mello, E.R.;
Brazilian Journal of Physics , 2001, DOI: 10.1590/S0103-97332001000200012
Abstract: in this paper we review some important aspects of the global monopole spacetime and present how this manifold modifies, at classical and quantum points of view, the movement of a charged particle. the explicit calculations of the renormalized vacuum expectation values of the energy-momentum tensors, átmn(x)?ren., associated with massless bosonic and fermionic fields are also presented. moreover the effect of the nonzero temperature in this previous formalism is analyzed. finally, we briefly present other applications of this manifold in the topological inflation and condensed matter system.
Physics in the Global Monopole Spacetime
Bezerra de Mello E.R.
Brazilian Journal of Physics , 2001,
Abstract: In this paper we review some important aspects of the global monopole spacetime and present how this manifold modifies, at classical and quantum points of view, the movement of a charged particle. The explicit calculations of the renormalized vacuum expectation values of the energy-momentum tensors, áTmn(x) Ren., associated with massless bosonic and fermionic fields are also presented. Moreover the effect of the nonzero temperature in this previous formalism is analyzed. Finally, we briefly present other applications of this manifold in the topological inflation and condensed matter system.
Precipitated immune complexes of IgM induce the generation of reactive oxygen species by rabbit polymorphonuclear leucocytes
Lucisano, Y.M.;de-Mello, A.M.;Vasques, E.R.;Mantovani, B.;
Brazilian Journal of Medical and Biological Research , 1998, DOI: 10.1590/S0100-879X1998000600011
Abstract: we report that immune complexes of igm (icigm) antibodies and ovalbumin in the form of a precipitate from the equivalence zone induce the generation of reactive oxygen species by rabbit blood polymorphonuclear leucocytes (pmn), as measured by the chemiluminescence (cl) production in the presence of luminol. the kinetics of cl generation induced by icigm is quite different from that induced by precipitated immune complexes of igg (icigg): the maximum rate of cl production for icigm occurs around 14 min, whereas for icigg it occurs about 5 min after incubation with the cells. also the triggering of the process requires a higher concentration of icigm than of icigg. evidence is presented that these effects are not mediated by interaction of the antigen (ovalbumin) with the cell, since immune precipitates of ovalbumin and the f(ab')2 fragment had no effect. our observations that precipitated icigm can also be an effective stimulus for cl generation and thus for o2- production reveal a new functional capability of pmn. these results may have implications for the understanding of the participation of icigm (as well as of icigg) in inflammatory reactions mediated by pmn in immune complex diseases, and in the mechanisms of defense against microbes and other non-self agents.
Precipitated immune complexes of IgM induce the generation of reactive oxygen species by rabbit polymorphonuclear leucocytes
Lucisano Y.M.,de-Mello A.M.,Vasques E.R.,Mantovani B.
Brazilian Journal of Medical and Biological Research , 1998,
Abstract: We report that immune complexes of IgM (ICIgM) antibodies and ovalbumin in the form of a precipitate from the equivalence zone induce the generation of reactive oxygen species by rabbit blood polymorphonuclear leucocytes (PMN), as measured by the chemiluminescence (CL) production in the presence of luminol. The kinetics of CL generation induced by ICIgM is quite different from that induced by precipitated immune complexes of IgG (ICIgG): the maximum rate of CL production for ICIgM occurs around 14 min, whereas for ICIgG it occurs about 5 min after incubation with the cells. Also the triggering of the process requires a higher concentration of ICIgM than of ICIgG. Evidence is presented that these effects are not mediated by interaction of the antigen (ovalbumin) with the cell, since immune precipitates of ovalbumin and the F(ab')2 fragment had no effect. Our observations that precipitated ICIgM can also be an effective stimulus for CL generation and thus for O2- production reveal a new functional capability of PMN. These results may have implications for the understanding of the participation of ICIgM (as well as of ICIgG) in inflammatory reactions mediated by PMN in immune complex diseases, and in the mechanisms of defense against microbes and other non-self agents.
Vacuum polarization by a scalar field in de Sitter spacetime in the presence of global monopole
E. R. Bezerra de Mello
Physics , 2009, DOI: 10.1134/S0202289310020027
Abstract: In this paper we analyse the vacuum polarization effects associated with massive scalar quantum fields in a higher-dimensional de Sitter space in the presence of a global monopole. Because this analysis has been developed in a pure de Sitter space, here we are mainly interested on the effects induced by the presence of the global monopole. So, in order to achieve this objective we calculate the corresponding Wightman function, which is expressed in an integral representation and explicitly depends on the parameters associated with the presence of the monopole and the cosmological constant. Admitting that the former is closed to the unity, which corresponds to a realistic value predicted by Grand Unified Theories, it is possible to express this function as the sum of two terms: the first one corresponds to the Wightman function on the bulk where the global monopole is absent, and the second one is a contribution induced by the presence of the monopole.
Vacuum polarization by topological defects in de Sitter spacetime
E. R. Bezerra de Mello
Physics , 2010, DOI: 10.1088/1742-6596/222/1/012034
Abstract: In this paper we investigate the vacuum polarization effects associated with a massive quantum scalar field in de Sitter spacetime in the presence of gravitational topological defects. Specifically we calculate the vacuum expectation value of the field square, $<\Phi^2>$. Because this investigation has been developed in a pure de Sitter space, here we are mainly interested on the effects induced by the presence of the defects.
Induced fermionic current densities by magnetic flux in higher dimensional cosmic string spacetime
E. R. Bezerra de Mello
Physics , 2009, DOI: 10.1088/0264-9381/27/9/095017
Abstract: In this paper we analyse the vacuum fluctuations of quantum fermionic current densities, $$, induced by a magnetic flux running along the core of the conical space produced by the presence of cosmic string, in a $(1+d)-$dimensional bulk, for $2\leq d\leq 5$. In order to develop this investigation we construct an expression for the fermionic propagator, which can be applied for those different dimensions of the spacetime. Two specific analysis for the induced current densities are presented: $(i)$ for massless fields in three and four dimensions, and $(ii)$ for massive fields in all dimensions considered. In the latter specific values for the parameters which codify the presence of the cosmic string and the fractional part of the ratio of the magnetic flux by the quantum one are considered. Although being a very special situation and somewhat unnatural, the corresponding analysis of induced fermionic current densities under this circumstance may shed light on the qualitative behavior of these quantities in a more general situation.
Reply to "Comment on 'Gravitating Magnetic Monopole in the Global Monopole Spacetime' "
E. R. Bezerra de Mello
Physics , 2003, DOI: 10.1103/PhysRevD.68.088702
Abstract: In this Reply I present some arguments in favor of the stability of the topological defect composed by global and magnetic monopoles.
Comment to "Fine structure constant in the spacetime of a cosmic string"
E. R. Bezerra de Mello
Physics , 2005, DOI: 10.1016/j.physletb.2005.07.009
Abstract: In the paper Phys. Lett. B614 (2005), 140-142, F. Nasseri shows that the values of the fine structure constant reduces due to the presence of a cosmic string. In this comment I want to point out that this conclusion is not completely correct in the sense that the result obtained is valid only in a very special situation.
Fermionic vacuum polarization in higher-dimensional global monopole spacetime
E. R. Bezerra de Mello
Physics , 2007, DOI: 10.1103/PhysRevD.76.125021
Abstract: In this paper we analyse the vacuum polarization effects associated with a massless fermionic field in a higher-dimensional global monopole spacetime in the "braneworld" scenario. In this context we admit that the our Universe, the bulk, is represented by a flat $(n-1)-$dimensional brane having a global monopole in a extra transverse three dimensional submanifold. We explicitly calculate the renormalized vacuum average of the energy-momentum tensor, $_{Ren.}$, admitting the global monopole as being a point-like object. We observe that this quantity depends crucially on the value of $n$, and we provide explicit expressions to it for specific values attributed to $n$.
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