Is it possible to accommodate massive photons in the framework of a gauge-invariant electrodynamics?

The construction of an alternative electromagnetic theory that preserves Lorentz and gauge symmetries, is considered. We start off by building up Maxwell electrodynamics in (3+1)D from the assumption that the associated Lagrangian is a gauge-invariant functional that depends on the electron and photon fields and their first derivatives only. In this scenario, as well-known, it is not possible to set up a Lorentz invariant gauge theory containing a massive photon. We show nevertheless that there exist two radically different electrodynamics, namely, the Chern-Simons and the Podolsky formulations, in which this problem can be overcome. The former is only valid in odd space-time dimensions, while the latter requires the presence of higher-order derivatives of the gauge field in the Lagrangian. This theory, usually known as Podolsky electrodynamics, is simultaneously gauge and Lorentz invariant; in addition, it contains a massive photon. Therefore, a massive photon, unlike the popular belief, can be adequately accommodated within the context of a gauge-invariant electrodynamics.Comment: 10 page

A Discussion on Massive Gravitons and Propagating Torsion in Arbitrary Dimensions

In this paper, we reassess a particular $R^{2}$-type gravity action in D dimensions, recently studied by Nakasone and Oda, taking now torsion effects into account. Considering that the vielbein and the spin connection carry independent propagating degrees of freedom, we conclude that ghosts and tachyons are absent only if torsion is non-propagating, and we also conclude that there is no room for massive gravitons. To include these excitations, we understand how to enlarge Nakasone-Oda's model by means of explicit torsion terms in the action and we discuss the unitarity of the enlarged model for arbitrary dimensions.Comment: 11 page

Is the pseudogap a topological state?

We conjecture that the pseudogap is an inhomogeneous condensate above the homogeneous state whose existence is granted by topological stability. We consider the simplest possible order parameter theory that provides this interpretation of the pseudogap and study its angular momentum states. The normal state gap density, the breaking of the time reversal symmetry and the checkerboard pattern are naturally explained under this view. The pseudogap is a lattice of skyrmions and the inner weak local magnetic field falls below the experimental threshold of observation given by NMR/NQR and $\mu$SR experiments.Comment: 12 pages, six figures, one tabl

Topologically stable gapped state in a layered superconductor

We show that a layered superconductor, described by a two-component order parameter, has a gapped state above the ground state, topologically protected from decay, containing flow and counter flow in the absence of an applied magnetic field. This state is made of skyrmions, breaks time reversal symmetry and produces a weak local magnetic field below the present threshold of detection by $\mu$SR and NMR/NQR. We estimate the density of carriers that condense into the pseudogap.Comment: 6 pages, 4 figure

Neisseria gonorrhoeae challenge increases matrix metalloproteinase-8 expression in fallopian tube explants

Indexación: Scopus.Background: Neisseria gonorrhoeae (Ngo) is the etiological agent of gonorrhea, a sexually transmitted infection that initially infects the female lower genital tract. In untreated women, the bacteria can ascend to the upper genital reproductive tract and infect the fallopian tube (FTs), which is associated with salpingitis and can lead to impaired FT function and infertility. The extracellular matrix (ECM) plays an important role in cell migration and differentiation in the female genital tract, and some pathogens modify the ECM to establish successful infections. The ECM is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs), their endogenous inhibitors; MMP deregulation causes pathological conditions in a variety of tissues. Results: The aim of this work was to analyze the expression and localization of MMP-3, MMP-8, MMP-9, and TIMP-1 in FT explants during Ngo infection using real-time PCR, immunohistochemistry, zymography and ELISA. No significant variations in MMP-3, MMP-9, and TIMP-1 transcript levels were observed. In contrast, a significant increase (p < 0.05) was observed for MMP-8 expression and was accompanied by stromal immunoreactivity in infected explants. ELISA results supported these findings and showed that MMP-8 release increased upon gonococcal infection. Conclusions: Our results indicate that gonococcal infection induces increased MMP-8 expression, which might contribute to FT damage during infection. © 2017 Juica, Rodas, Solar, Borda, Vargas, Muñoz, Paredes, Christodoulides and Velasquez.https://www.frontiersin.org/articles/10.3389/fcimb.2017.00399/ful

Financial and economic sustainability of urban solid waste recovery facilities in Colombia

Resumen En Colombia menos del 2% de los Residuos Sólidos Urbanos Domiciliarios (RSUD) son manejados en Plantas de Manejo de Residuos Sólidos (PMRS), presentando en la mayoría de casos perdidas operacionales cercanas al 60%, llevando al cierre de gran parte de dichas instalaciones. Ante ello, esta investigación se enfocó en establecer unas condiciones mínimas para un escenario económico-financiero de operación sostenible de PMRS en municipios menores a 50,000 habitantes, mediante la combinación de herramientas de Dinámica de Sistemas y Análisis Estructural. Como resultado se identificó que i) la cantidad de material potencialmente aprovechable a recibir, ii) los ingresos por tarifa de recepción de material y iii) las cantidades de material recuperado para la venta, se constituyen como Variables Clave de sostenibilidad. Para el escenario simulado se concluye que con el actual cobro de tarifas de recepción de residuos, el aumento de eficiencias de recuperación y comercialización de residuos, sería necesario la recepción de 302 t/mes para alcanzar una relación beneficio/costo igual a 0. Sin embargo dicho valor puede variar en función de las particularidades regionales y tecnologías implementadas de cada proyecto PMRS, lo cual hace necesario el desarrollo de estudios puntuales para el desarrollo de un proyecto en una localidad determinada. Abstract In Colombia, less that 2% of Urban Solid Waste (USW) are treated in Solid Waste Recovery Facilities (SWRF), having in almost all cases operational losses close to 60%, leading to the closure of several plants. Based on that, this research was focused on the establishment of some minimal conditions for the sustainability of a financial-economic scenario of a SWRF in towns with less than 50,000 inhabitants, by combining System Dynamics and Structural Analysis tools. As result, it was identified that the i.) amount of potentially usable material received, ii.) incomes for material reception, and iii.) amount of recovered material for sale, become as Key of sustainability. For the simulated scenario it is concluded that with the current fee of solid waste reception, the increase of recovery efficiency and merchandising of materials, it would be necessary to receive at least 302 t/month, to reach a cost/benefit ratio equal to 0. However that value can change as a function of the regional characteristics and implemented technologies of each project, thus it is necessary the development of studies of a project in a determined location