3,334 research outputs found

    Casimir energy in the Gribov-Zwanziger approach to QCD

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    In this paper we study the Casimir energy of QCD within the Gribov-Zwanziger approach. In this model non-perturbative effects of gauge copies are properly taken into account. We show that the computation of the Casimir energy for the MIT bag model within the (refined) Gribov-Zwanziger approach not only gives the correct sign but it also gives an estimate for the radius of the bag.Comment: 5 pages, No figures. The discussion about the constraints on the RGZ parameters (as well as about the corresponding estimates) imposed by the requirement to have the correct behaviour of the Casimir energy has been expanded. Version accepted for publication on Physical Review

    Casimir energy in a spherical surface within surface impedance approach: the Drude model

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    The Casimir Energy of a spherical surface characterized by its surface impedance is calculated. The material properties of the boundary are described by means of the Drude model, so that a generalization of previous results is obtained. The limits of the proposed approach are analyzed and a solution is suggested. The possibility of modulating the sign of the Casimir force from positive (repulsion) to negative (attraction) is studied.Comment: 10 page

    Energy-momentum tensor for a scalar Casimir apparatus in a weak gravitational field: Neumann conditions

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    We consider a Casimir apparatus consisting of two perfectly conducting parallel plates, subject to the weak gravitational field of the Earth. The aim of this paper is the calculation of the energy-momentum tensor of this system for a free, real massless scalar field satisfying Neumann boundary conditions on the plates. The small gravity acceleration (here considered as not varying between the two plates) allows us to perform all calculations to first order in this parameter. Some interesting results are found: a correction, depending on the gravity acceleration, to the well-known Casimir energy and pressure on the plates. Moreover, this scheme predicts a tiny force in the upwards direction acting on the apparatus. These results are supported by two consistency checks: the covariant conservation of the energy-momentum tensor and the vanishing of its regularized trace, when the scalar field is conformally coupled to gravity.Comment: 5 pages in double-column format, Revtex4. The final version is shorter, and the presentation has been improve

    Variations of Casimir energy from a superconducting transition

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    We consider a five-layer Casimir cavity, including a thin superconducting film. We show that when the cavity is cooled below the critical temperature for the onset of superconductivity, the sharp variation (in the microwave region) of the reflection coefficient of the film produces a variation in the value of the Casimir energy. Even though the relative variation in the Casimir energy is very small, its magnitude can be comparable to the condensation energy of the superconducting film, and thus causes a significant increase in the value of the critical magnetic field, required to destroy the superconductivity of the film. The proposed scheme might also help clarifying the current controversy about the magnitude of the contribution to Casimir free energy from the TE zero mode, as we find that alternative treatments of this mode strongly affect the shift of critical field.Comment: RevTex 4, 15 pages, 8 figures. Revised version with improved presentation, a brief description of the ALADIN experiment, and a few references adde

    Lactoferrin against inflammatory and iron disorders in different infection models

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    Lactoferrin (Lf) is a cationic glycoprotein able to chelate two ferric ions per molecule. Human Lf (hLf), a key element of host defenses, is secreted by exocrine glands and by neutrophils. HLf and bovine Lf (bLf), possessing high sequence homology, exert identical functions, such as antimicrobial and antiviral activities. In the last decades, other important Lf activities have been discovered, including the anti-inflammatory one. This Lfs function is strictly dependent by the binding with specific host cell receptors, leading to Lf cell internalization and translocation into the nucleus, thus directly down-regulating pro-inflammatory genes’ expression. In this regard, our group has recently demonstrated the bLf ability in counteracting the tight interplay between inflammatory and iron homeostasis disorders in inflamed macrophages, by down-regulating interleukin (IL)-6 synthesis and rebalancing the expression of main iron-handling proteins, namely ferroportin (Fpn), transferrin receptor 1 (TfR1) and ferritin (Ftn). Here, the role of bLf in different infection models is presented, highlighting its ability to exert a potent action against infection as well as iron and inflammatory disorders. The first model regards a cystic fibrosis (CF) mice suffering from Pseudomonas aeruginosa chronic lung infection. Treatments with aerosolized bLf for 7 days were effective in significantly reducing pulmonary bacterial load. Furthermore, for the first time, we showed that bLf treatment was effective in rebalancing the expression of both iron exporter Fpn and iron storage Ftn, thus reducing pulmonary iron overload. The second model concerns the role of bLf against Chlamydia trachomatis infection in vitro and in vivo. C. trachomatis, an obligate intracellular pathogen causing infections associated to inflammation, requires iron for its replication. In in vitro study bLf interferes with C. trachomatis entry into human epithelial cell line when cell monolayers were pre-treated or treated with the protein at the moment of the infection. Lf exerts a potent anti-inflammatory activity down-regulating IL-6 and IL-8 synthesis as well as rebalancing the expression of Fpn and TfR1 in infected cells. In addition, pregnant women asymptomatically infected by C. trachomatis, after 30 days of bLf intravaginal administration, were negative for C. trachomatis with a decrease of cervical IL-6 levels. The third and last model regards the in vitro study of bLf antiviral activity against the new coronavirus infection (SARS-CoV-2). The coronavirus infection causes severe acute respiratory syndrome characterized by massive systemic levels of pro-inflammatory cytokines. In in vitro preliminary results, bLf, through its competitive binding with viral component(s) and its interaction with host surface receptors, blocks SARS-CoV-2 entry in different cell models. Interestingly, the in silico results strongly support the hypothesis of a direct recognition between the lactoferrin and the spike S glycoprotein, thus hindering the viral entry into the cells. Moreover, we performed a randomized, prospective, interventional study assessing for 30 days the effect and tolerability of an oral (1 gr/day) and intranasal (about 16 mg/nostril) liposomal lactoferrin on 10 asymptomatic and 22 mild-to-moderate COVID-19 patients. After 15 days of treatment, rRT-PCR revealed a negative conversion of SARS-COV-2 RNA of the naso-oropharingeal swab in 28 patients (87.5%) and in 4 after 30 days. A significant reduction of D-Dimer, IL-6 and ferritin blood levels was observed together with a fast clinical symptoms recovery. No adverse effects were observed

    Push on a Casimir apparatus in a weak gravitational field

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    The influence of the gravity acceleration on the regularized energy-momentum tensor of the quantized electromagnetic field between two plane parallel conducting plates is derived. We use Fermi coordinates and work to first order in the constant acceleration parameter. A new simple formula for the trace anomaly is found to first order in the constant acceleration, and a more systematic derivation is therefore obtained of the theoretical prediction according to which the Casimir device in a weak gravitational field will experience a tiny push in the upwards direction.Comment: 14 pages, Plain Tex. Talk given at the 17th SIGRAV Conference on General Relativity and Gravitational Physics, Torino, September 200

    Soil quality evaluation under agro-silvo-pastoral Mediterranean management systems

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    According to Franzluebber (2002) the degree of stratification of soil organic C and N, as well as other parameters, with soil depth, expressed as a ratio, can indicate soil quality or soil ecosystem functioning and sustainability under different agricultural management. Stratification ratios > 2 indicate a higher soil quality and contribution to agriculture sustainability. A case study from northeastern Sardinia (Italy) is presented
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