Inhibition of the dynamical Casimir effect with Robin boundary conditions

We consider a real massless scalar field in 3+1 dimensions satisfying a Robin boundary condition at a nonrelativistic moving mirror. Considering vacuum as the initial field state, we compute explicitly the number of particles created per unit frequency and per unit solid angle, exhibiting in this way the angular dependence of the spectral distribution. The well known cases of Dirichlet and Neumann boundary conditions may be reobtained as particular cases from our results. We show that the particle creation rate can be considerably reduced (with respect to the Dirichlet and Neumann cases) for particular values of the Robin parameter. Our results extend for 3+1 dimensions previous results found in the literature for 1+1 dimensions. Further, we also show that this inhibition of the dynamical Casimir effect occurs for different angles of particle emission.Comment: 18 pages, 3 figure

Time-dependent Robin boundary conditions in the dynamical Casimir effect

Motivated by experiments in which moving boundaries are simulated by time-dependent properties of static systems, we discuss the model of a massless scalar field submitted to a time-dependent Robin boundary condition (BC) at a static mirror in 1+1 dimensions. Using a perturbative approach, we compute the spectral distribution of the created particles and the total particle creation rate, considering a thermal state as the initial field state.Comment: 10 pages, 3 figures. To appear in proceedings of Conference on Quantum Field Theory under the Influence of External Condition

Art and Religion

Krista Andreson: Art and ReligionKeywords: sacral art; art and religion; „art as religion“Summary:On October 10th and 11th, the Autumn School “Art and Religion” took place in the Department of Art History at the University of Tartu, in the course of which, art historians, theologians and philosophers spoke about the relations between art and religion, as well as their fields of meaning from the Early Christian period to the present day. The focus of the first day, with the subtitle of “Images and the Church”, was on sacral art. The presentations dealt with the “picture question” in the Western and Eastern branches of Christianity, the various functions and possibilitiesfor the interpretation of the works of art in the service of  medieval Catholicism and post-Reformation Lutheranism, as well as the contacts between ritual and religion in the Early Modern period, based on the example of 17th-century portraiture. On the second day of the Autumn School, with the subtitle “Art and/as Religion”, the focus was on religious themes in connection with contemporary “autonomous” art. The opposite ends of the axis were examined – the alienation between art and religion, as well as the reinterpretation of the relationship on new bases, including the impact of different religions of the 20th century and the various forms of expressing religiosity on the art world. The presentations showed that Christian art and religiousthemes have not disappeared, however a significant change hasgenerally occurred in the bases of this art and within the framework of certain works. As one of the main topics of the second day, the trends that have developed inside and adjacent to “mainstream” art emerged. These are on the one hand characterised by the emergence of the artist’s “me” – art has become the new religion and the artist has become God. Thus, along with the contrasting, one can also notice a certain analogy,including between the operational mechanisms of art and religion. However, these trends are often marked with the impact of modern “substitute” religions or new forms of religion, including various “secret sciences” with a spiritual background.CV:Krista Andreson is a research fellow in the Department of Art History at the University of Tartu. She has studied in Germany at the University of Kiel, as well as held shorter academic residencies in Leipzig and Greifswald. From 2003 to 2010, Andreson was a research fellow at the Niguliste Museum (branch of the Art Museum of Estonia). Her main area of research is medieval ecclesiastical art and iconography and she has published several research papers on the medieval wooden sculptures and altarpieces in the Baltic Sea Region. The topic of Krista Andreson’s doctoral thesis is “The Relations between Art and Culture in Old Livonia Based on the Example of Ecclesiastical Art: Wooden ScuSculptures from the 13th Century to the First Half of the 15th Century”

Linear peptidomimetics as potent antagonists of Staphylococcus aureus agr quorum sensing

AbstractStaphylococcus aureus is an important pathogen causing infections in humans and animals. Increasing problems with antimicrobial resistance has prompted the development of alternative treatment strategies, including antivirulence approaches targeting virulence regulation such as the agr quorum sensing system. agr is naturally induced by cyclic auto-inducing peptides (AIPs) binding to the AgrC receptor and cyclic peptide inhibitors have been identified competing with AIP binding to AgrC. Here, we disclose that small, linear peptidomimetics can act as specific and potent inhibitors of the S. aureus agr system via intercepting AIP-AgrC signal interaction at low micromolar concentrations. The corresponding linear peptide did not have this ability. This is the first report of a linear peptide-like molecule that interferes with agr activation by competitive binding to AgrC. Prospectively, these peptidomimetics may be valuable starting scaffolds for the development of new inhibitors of staphylococcal quorum sensing and virulence gene expression.</jats:p

The Presence of the Sacred: A 13th-century cult image from Saaremaa (Estonia)

This article undertakes a closer examination of the small (52-cm) oak figure of the crucified Christ on permanent exhibit at the Saaremaa Museum in Kuressaare. The original crossbar of the crucifix has not survived, it is covered with modern polychrome and there is no definitive information on which church the sculpture initially belonged to. If we wishto reconstruct the initial function of the sculpture in the sacral context, we must rely primarily on the object itself, its particular iconographical properties and style of depiction, as well as the results of technologicalresearch. In addition, we can seek additional information from the network of relationships between visual objects and liturgy of the past. On the one hand, Saaremaa’s crucified Christ is characterised by an “old-fashioned” method of attachment to the cross using four nails, and on the other, Christ’s chest wounds and the traits characteristic of a tense, hanging body are emphasised. Since changes in the number of nails and method of attachment to the cross started to appear in the middle of the 12th century, and the great breakthrough did not occur until the late 1210s and early 1220s, and it became prevalent by the middle of the 13th century at the latest, this time period establishes the temporal framework for the completion of the Saaremaa crucifix. The Saaremaa crucified Christ is also characterised by a specific iconography, which alludes to Passion piety and respect for the bodily Christ in the first half of the 13th century. Recent technological research provides a basis to believe that the back (and probably the head) of the figure initially contained a sepulchrum, which traditionally contained a relic or piece of the Host. As such, the Saaremaa crucified Christ is a medieval cult image, and in addition to the existence of the repository, is unusual due the fact that it dates back to the period of the first written information on the existence of Christian houses of worship on Estonian territory. However, the Christianisation of the Estonian area had yet to be completed and the network of churches was still in the process of being developed. The sculpture’s artistic parallels point to a group of  crucifixes of German origin completed in the second quarter of the 13th century – to comparative material from a region, from which, along with ecclesiastical and political contacts, artistic impulses arrived in Saaremaa, and more broadly in Livonia during this period